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An Acad Bras Cienc (2021) 93(3): e20200254 DOI 10.1590/0001-3765202120200254
Anais da Academia Brasileira de Ciências | Annals of the Brazilian Academy of Sciences
Printed ISSN 0001-3765 I Online ISSN 1678-2690
www.scielo.br/aabc | www.fb.com/aabcjournal
CELLULAR AND MOLECULAR BIOLOGY
Lutzomyia longipalpis: an update
on this sand fly vector
FELIPE D. RÊGO & RODRIGO PEDRO SOARES
Abstract: Lutzomyia longipalpis is the most important vector of Leishmania infantum,
the etiological agent of visceral leishmaniasis (VL) in the New World. It is a permissive
vector susceptible to infection with several Leishmania species. One of the advantages
that favors the study of this sand fly is the possibility of colonization in the laboratory.
For this reason, several researchers around the world use this species as a model for
different subjects including biology, insecticides testing, host-parasite interaction,
physiology, genetics, proteomics, molecular biology, and saliva among others. In 2003,
we published our first review (Soares & Turco 2003) on this vector covering several
aspects of Lu. longipalpis. This current review summarizes what has been published
between 2003-2020. During this period, modern approaches were incorporated following
the development of more advanced and sensitive techniques to assess this sand fly.
Key words: Lutzomyia longipalpis, sand flies, vector biology, interaction.
INTRODUCTION A great deal of information about Lu.
longipalpis has already been reviewed by
Lutzomyia longipalpis sensu lato Lutz & Neiva, Soares & Turco (2003), therefore, here we
1912 is considered the main vector of Leishmania discuss updates throughout the last decades on
infantum Nicole, 1908 in the American continent this sand fly vector, focusing on the information
(Lainson & Rangel 2005). This species is widely generated from 2003 to early 2020.
distributed, occurring in diverse ecological
niches, such as dry habitats, humid forests but
especially in urban and rural areas, where it Lutzomyia Longipalpis SPECIES
has successfully established and spread itself COMPLEX AND SEX PHEROMONES
(Ximenes et al. 2000, Souza et al. 2009b, Brazil
Understanding the evolutionary history of Lu.
2013, Rodrigues et al. 2014, Dvorak et al. 2018).
longipalpis, as well as how geographical barriers
Several components are involved in the
and, more recently, anthropogenic environmental
urbanization and dispersion of Lu. longipalpis
changes and activities have contributed to the
including climatic, environmental and
evolution of sibling species continues to remain
sociocultural factors. This topic has been deeply
a challenge. Combined analyses using molecular
reviewed by Salomón et al. (2015). Furthermore,
markers and behavioral traits such as love
the occurrence and the likely geographical
songs and pheromones strongly suggest that Lu.
distribution of this sand fly in Brazil has been
longipalpis is a complex species, with distinct
predicted and modeled using geographic
population structures as well as reproductively
information systems and remote sensing
isolated populations (Arrivillaga et al. 2003,
(Andrade-Filho et al. 2017).
An Acad Bras Cienc (2021) 93(3)FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
2009, Hodgkinson et al. 2003, Bottecchia et (3MαH) or cembrene (CEMB-1 or CEMB-2). To
al. 2004, Watts et al. 2005, Balbino et al. 2006, date, populations that produce diterpenes
Bauzer et al. 2007, Araki et al. 2009). Details has been found only in Brazilian populations.
on the current status of the Lu. longipalpis All pheromone typed species in South and
species complex have been reviewed by Souza Central America, excluding Brazil, were
et al. (2017), especially regarding the historical 9MGB (Spiegel et al. 2016). Within the sibling
overview, behavioral traits, courtship song and species of Lu. longipalpis complex, Lutzomyia
genetic characteristics of the group. Therefore, pseudolongipalpis from Venezuela produces
factors involved in mating have undoubtedly 3MαH (Hamilton et al. 2005, Watts et al. 2005)
played (and continue to play) a significant role and Lutzomyia cruzi from Corumbá, Mato Grosso
in maintaining reproductive isolation among the do Sul state, Brazil, produces 9MGB (Vigoder
different sibling species. et al. 2010). There is no information about
The most current data on genetic the pheromone type produced by Lutzomyia
diversity using several molecular markers gaminarai, a species endemic in the southern
of Lu. longipalpis indicate the presence of region of Brazil, occurring in the States of Paraná
two clades: the first one is composed by and Rio Grande do Sul (Galati 2018).
Brazilian and Argentinian haplogroups and Several aspects on Lu. longipalpis complex
the second clade includes populations from still remains an open field to the investigators.
Central America and northern South America Although most studies have focused on
(Guatemala, Honduras, Costa Rica, Colombia and the genetic structure of the sibling species,
Venezuela) (Pech-May et al. 2018). However, even description of pheromones and love songs,
belonging to the same clade, Argentinian and the female of Lu. gaminarai has not yet been
Brazilian populations present distinct genetic formally described. Moreover, until today it is
polymorphisms (Araki et al. 2009), resulting in not clear how many species or incipient species
separated populations (sub-clades) using a within the Lu. longipalpis-complex exist in Brazil,
more refined analysis. A complex population or even which species is the original type, since
structure of Lu. longipalpis from Brazil has been the specimens used to describe this sand fly
presented on a geographical scale by Casaril et (Lutz & Neiva 1912) no longer exist. Furthermore,
al. (2019). The presence of geographical barriers few specimens have been collected in Benjamin
may also contribute to divergence and the Constant, Minas Gerais State, Brazil, the type
speciation process that seems to be occurring locality of Lu. longipalpis (Brazil et al. 2006),
within the species complex. Genetic studies of becoming one of the biggest bottlenecks on sand
Lu. longipalpis provide information about the fly study, given the difficulty to establish a new
heterogeneity of vector capacity/competence species-type for the complex and consequently
and vector susceptibility to insecticides as will the description of sibling species.
be discussed later. Within the Brazilian populations of Lu.
Based on the geographical distribution longipalpis, Araki et al. (2009) have proposed to
and pheromone types, it is predicted that (S)- segregate the species complex into two groups:
9-methylgermacrene-B (9MGB) is the ancestral the first one, more homogeneous, representing
chemotype in Lu. longipalpis across South America, a single species in which males produce burst-
followed by subsequent speciation to either type copulation songs and CEMB-1 pheromones;
diterpenes (1S,3S,7R)-3-methyl-α-himachalene the other group, more heterogeneous, probably
An Acad Bras Cienc (2021) 93(3) e20200254 2 | 29FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
represents incipient species that produce permissive vector, intra-populations variability
different combinations between pulse- may result in a lack of interaction between the
type songs (five patterns of pulse-type) and parasite and the vector. This was the case of
pheromones such as 9MGB, 3MαH, CEMB-1 and allopatric populations of Nyssomyia umbratilis
CEMB-2, totaling at least six sibling species collected in the south and north of Negro River
(Vigoder et al. 2015). Genetic evidence suggests in the Amazon (Soares et al. 2018). In this paper,
that introgressive hybridization has been a using the in vitro system, the authors observed
crucial phenomenon of the recent speciation that the south population was refractory to
process that occurs within the Lu. longipalpis interaction with Le. guyanensis. However, we do
complex (Araki et al. 2013). Microsatellite not know if such a phenomenon would occur
data have shown limited genetic flow and in Lu. longipalpis and this would be a very
introgression between Lu. longipalpis and Lu. interesting direction of further molecular and
cruzi in which the divergence level was similar biochemical studies.
to that observed among Brazilian populations The sympatric populations from Sobral,
of Lu. longipalpis (Vigoder et al. 2010, Lins et State of Ceará, Brazil, have been deeply studied,
al. 2012, Santos et al. 2013). However, data from focusing on the genetic, evolutionary and
12S rDNA sequencing did not differentiate Lu. epidemiologic significance of the one-pair-of-
longipalpis from Lu. cruzi (Corumbá), suggesting spots (S1) and two-pairs-of-spots (S2) male
that the speciation process is recent or still phenotypes of Lu. longipalpis. Lins et al. (2008)
occurring (Ribolla et al. 2016). Nevertheless, have identified a clear difference between these
more genetic data is needed to confirm the populations using the paralytic (para) gene
occurrence of the recent speciation process as well as an association of the para and the
between Lu. longipalpis and Lu. cruzi. Moreover, resistance to pyrethroid insecticides. Further
introgression patterns in the genome seem to studies on genetic polymorphisms in period
have a relevant effect on transmission dynamics gene (per) have also suggested the presence
of Leishmania parasites. Therefore, exploring of two sibling species in Sobral (Costa-Júnior
these aspects on Lu. longipalpis complex may be et al. 2015). This data added crucial information
a good way to understand the vectorial capacity about these reproductive isolated populations,
of the sibling species (Araki et al. 2013). Distinct suggesting the importance of premating
genetic composition of populations from Espírito barriers in Lu. longipalpis sibling species
Santo, Brazil, seems to affect their susceptibility speciation (Maingon et al. 2003). Additionally,
to Leishmania or even the capability to transmit genetic divergence in the cacophony gene (cac)
the pathogen in an anthroponotic environment showed that S2 population is more related to
by the low adaptability of Lu. longipalpis to Natal population (both produce burst type and
this environment (Rocha et al. 2011). Although CEMB-1) whereas S1 (pulse type 3 and 9MGB) was
a lot of papers have focused on establishing closer to Jacobina (pulse type 1 and 3MαH) and
the genetic and pheromone variations in the Lu. Lapinha (pulse type 2 and 9MGB). The genetic
longipalpis species complex, there is still a gap diversity observed in S1 and S2 may also reflect
in how those variations affect interaction with distinct physiological and behavioral aspects
Le. infantum. It would be extremely important for both populations. However, until today,
to address the vectorial competence of a given there is a lack of information on host-parasite
Lu. longipalpis population. Although it is a interaction comparing sympatric populations
An Acad Bras Cienc (2021) 93(3) e20200254 3 | 29FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
as S1 and S2. The genetic divergence between affect the interaction with Le. infantum is an
these populations may affect the interaction open field still needed to be explored by the
with Le. infantum. Although few variations investigators.
have been observed, both males and females
from the S2 population seem to initiate their
crepuscular activity a little earlier than S1 (Rivas Lutzomyia Longipalpis CONTROL
et al. 2008). However, more studies are needed Although nowadays it is still difficult to control
to confirm distinct patterns of hourly activity as the sand flies vector populations, important
well as other differences in biological behavior tools have been arising to improve the strategies,
between these populations. Besides their especially for VL control. The first problem is
circadian rhythms, also the pheromones and the difficulty to find the larval stages in the
patches were shown to affect bionomic aspects environment (Casanova 2001, Sangiorgi et al.
of Lu. longipalpis. Populations that produce 2012). In a field evaluation using an adulticide-
homosesquiterpene (C16), such as sand flies larvicide mixture (100 mg of permethrin and 2
from Jacobina (3MαH), Lapinha and Sobral one mg/m2 of pyriproxyfen), a significant decrease
spot (1S) (both 9MGB) seems to be more easily in the number of Lu. longipalpis was reported
adapted to the colonization conditions than the for at least two weeks (Juan et al. 2016). However,
population whose males produces diterpenes further studies are needed to evaluate the
(CEMB-1) such as the sand flies from Natal and persistence of the residual effect of pyriproxyfen
Sobral two spots (2S) (Souza et al. 2009a). Since in controlling Lu. longipalpis larvae. For this
colonization is an important aspect that hinders reason, most of the studies have focused on
sand fly studies, a better knowledge of those the adult stages. Volatile compounds based
pheromones could also help to choose a more on male pheromones and kairomones have
productive colony. demonstrated a good efficacy if used combined
Finally, although most of the studies with automatic light traps improving catch rates,
focused on patches occurred in Sobral, those especially for Lu. longipalpis. Furthermore,
phenotypes were also detected in other states. synthetic pheromones can feasibly improve
For example, S2 male phenotype was found in the efficacy of sand fly control programs when
Jaíba (Minas Gerais State), Estrela de Alagoas used alongside insecticides. This combined
(Alagoas State), Raposa and Codó (Maranhão strategy attracts and kills both sexes, preventing
State) (Araki et al. 2009). Consistent with the host-seeking females from transmitting
studies in Sobral, Silva et al. (2011) have shown Le. infantum and males from establishing
genetic polymorphisms between Raposa and alternative aggregation sites elsewhere (Bray et
Codó sympatric populations, suggesting a clear al. 2009). A decrease in the number of sand flies
segregation related to spot phenotypes (Lins et attracted usually occurs as a consequence of
al. 2008, Costa-Júnior et al. 2015). insecticide treatments, however, the application
In conclusion, a large number of papers of synthetic pheromones into insecticide-
published before 2003 have addressed the sprayed experimental sheds seems to prevent
pheromones and the genetic aspects of the Lu. and reverse it, improving the catch rates of Lu.
longipalpis complex. Since 2003 those numbers longipalpis (Bray et al. 2010). The number of
have decreased, probably due to the acceptance pheromone-lures seems to have an influence
of the species complex idea. How such variations
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on the effectiveness of this strategy to attract mortality faster. Both insecticides classes
sand flies. Bell et al. (2018) have shown that have similar modes of action, and, despite
increasing the number of lures results in the differences in killing rates for carbamates
an upward trend in the number of sand flies and organophosphates, Lu. longipalpis are
that are caught in the field, especially males. most susceptible to bendiocarb and propoxur
Kairomones have been extensively used carbamates as well as to the organophosphate
to attract hematophagous insects, such as fenitrothion (Denlinger et al. 2015). Furthermore,
mosquitoes and tse tse flies, however, there are the doses for each insecticide have been
few studies focusing on sand fly attraction. The determined using the CDC bottle bioassay to
compounds 1-octanol, a volatile component of assess Lu. longipalpis resistance, providing
bovine and human breath, and 1-nonanol, a starting points to test on field populations
volatile from cattle urine, elicited the highest (Denlinger et al. 2016).
attractiveness response in Lu. longipalpis adults The use of insecticide-impregnated nets
in a dose-dependent manner (Magalhães-Junior has also been used as a complementary tool for
et al. 2014). However, these alcohols have been sand fly control, especially Lu. longipalpis. The
identified at small levels in human breath or entomological efficacy of 25% deltamethrin EC
skin odors, which may justify the lack of interest insecticide-treated bednets has been evaluated
in their potential role as an attractant for sand by Courtenay et al. (2007), in a crossover field
flies (Magalhães-Junior et al. 2014). study in Amazon Brazil (Marajó Island, State
Although the chemical attraction has been of Pará). Compared with untreated nets, the
the newest tool in this field, sand fly control insecticide ones increased the barrier effect of
programmes still often rely on spraying potential the nets by 39%, reduced human landing rates
resting sites (intra or peridomiciliary sites) with by 80% and increased the 24 hours mortality rate
residual insecticides, especially pyrethroids as (Courtenay et al. 2007). The lambda-cyhalothrin
lambda-cyhalothrin (Feliciangeli et al. 2003, seems to have a short residual effect, whose
Camargo-Neves et al. 2007a), deltamethrin efficacy declined to 74% after six months. On
(Santini et al. 2010), alpha cypermethrin (Pessoa the other hand, permethrin-impregnated nets
et al. 2015) and permethrin (Alexander et al. maintained its effectiveness close to 100%
2009), with varying effectiveness. However, lethality 24 hours post exposure for at least
spraying also requires training to be conducted a year under laboratory conditions (Bray &
effectively, in order to ensure that the correct Hamilton 2013). However, those conditions may
concentration of insecticide is applied, not be possible in the field. Trials using a variety
minimizing exposure to sub-lethal amounts of indoor and outdoor surfaces are needed
which might promote the onset of resistance to confirm the effectiveness of this netting-
to several compounds. Denlinger et al. (2015) treatment protocol in the field, especially close
have quantified the insecticide susceptibility to animal shelters.
in laboratory-reared Lu. longipalpis to ten A distinguished feature in Lu. longipalpis
insecticides, comprising four chemical classes: populations is their ability to respond
pyrethroid, organophosphate, carbamate differently to the action of pyrethroids and
and organochlorine. The organophosphate organophosphates. For example, Montes Claros
insecticides caused delayed mortality in the sand flies were most susceptible to malathion,
sand fly population, while carbamate caused fenithorion and deltamethrin, while those from
An Acad Bras Cienc (2021) 93(3) e20200254 5 | 29FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
Lapinha were most susceptible to cialotrhin, that evaluate the efficacy of this strategy in
malathion and permethrin in laboratory the field. Longer follow-up studies on how ICC
conditions (Alexander et al. 2009). Moreover, affects vector population and its impact on VL
a significant reduction in the susceptibility cases are needed. Considering the importance
to the insecticides reinforced the importance of protecting dogs from sand fly bites, it would
of developing tools for detecting resistance be interesting to evaluate the potential role of
(Alexander et al. 2009). Since the efficacy mass use of ICC as a strategy to reduce canine
of insecticides differ within Lu. longipalpis visceral leishmaniasis incidence. However, the
populations, the combined use of insecticides short-lasting effect, the need to frequently
may be a better strategy for the sand fly replace the ICC, and local symptoms in dogs, are
control. In this context, the repellent efficacy of still problems to be solved.
a spot-on topical combination of fipronil and Although insecticide-based control
permethrin has been evaluated in dogs (Cutolo measures are available for sand flies, there is
et al. 2018). A significant repellent effect against still an urgent need for novel and alternative
Lu. longipalpis as soon as it was applied on methods that do not affect or are less harmful
the dogs and high protection rates for 28 days to the environment. In this context, biological
has been shown. However, due to the short control could represent an important initiative
anti-feeding effect, regular application in dogs for future studies. The combined use of
may hinder its protective effect in VL-endemic chemical insecticides and selective pathogens
areas (Cutolo et al. 2018). Likewise, the 4% may increase the efficiency of insect control.
deltamethrin-impregnated canine collar (ICC) In this way, a possible alternative to current
has not presented a long-lasting effect compared strategies may be the biological control of
with spot-on topical repellents; however, the the vector using the entomopathogenic fungi
ICC is currently being considered as a relevant Beauveria bassiana. Amóra et al. (2009) report
tool for VL control (Albuquerque e Silva et al. that Lu. longipalpis eggs infected with this
2018). The ICC tends to reduce the prevalence fungus reduced the hatching to 59%, suggesting
of canine VL, in two basic ways: 1) reducing the a pathogenic potential on both larvae and
blood feeding by the vector and, 2) reducing adults. Moreover, Metarhizium anisopliae var.
the vector population, mediated by repellent acridum, another entomopathogenic fungal, was
and insecticidal action of deltamethrin (Coura harmful to sand flies in the adult stage (Amóra
et al. 2019). The use of ICC reduced the number et al. 2010). Even in the laboratory, the studies
of Lu. longipalpis captured in an interventional on entomopathogenic fungi are very scarce. This
area in Montes Claros, State of Minas Gerais reinforces the need for more studies on the
(14% of reduction) and Fortaleza, State of Ceará impact-cost of such organisms while applying
(60% of reduction). Moreover, a 40% decrease them in the field for controlling sand flies.
in canine VL prevalence has been reported Several studies have investigated the use
in both municipalities (Albuquerque e Silva of plants to control vector-borne diseases.
et al. 2018). The anti-feeding effect of ICC has Plants from the Meliaceae family (Azadirachta
also been reported in Europe for Phlebotomus indica) have been deeply studied due to their
perniciosus, the vector of Le. infantum (Maroli effects against many insects, especially those
et al. 2001, Manzillo et al. 2006, Ferroglio et al. of agricultural importance. However, few studies
2008). Until today, there are few studies in Brazil have focused on sand flies. Few ovicidal and
An Acad Bras Cienc (2021) 93(3) e20200254 6 | 29FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
larvicidal effects have been reported even in fauna and consequently obtain the specific
high concentration of A. indica oil when Lu. antisera. Further, molecular methods (PCR and
longipalpis eggs and larvae were treated in DNA sequencing) gradually replaced those
laboratory conditions (Maciel et al. 2010). On the techniques, improving blood meal identification
other hand, the triterpenoid azadirachtin seems by using CytB as universal primers (Sant’Anna et
to block the metamorphosis when added to al. 2008, Soares et al. 2014, Carvalho et al. 2017b).
larval food of Lu. longipalpis (Andrade-Coelho Lutzomyia longipalpis has broad-range
et al. 2006). Studies have also showed that A. feeding habits due to their adaptation to
indica and Melia azedarach fruit and leaves in different habitats in both intradomiciliary and
natura significantly increased larval mortality peridomiciliary sites. Several authors have
in comparison to untreated insects (Andrade- reported that this vector fed on dogs, cats,
Coelho et al. 2009). Azadirachtin also seems pigs, cattles, horses, chickens and synanthropic
to affect Lu. longipalpis oviposition and may vertebrates (rats and opossums). With the
increase the mortality in adults, indicating that exception of chicken, most of the aforementioned
azadirachtin may be a potent sterilizer that hosts are potential reservoirs of Leishmania
could be used against the development of Lu. (Dias et al. 2003, Marassá et al. 2006, Camargo-
longipalpis populations (Andrade-Coelho et al. Neves et al. 2007b, Missawa et al. 2008, Sant’Anna
2014). et al. 2008, Afonso et al. 2012, Soares et al. 2014,
In conclusion, there are few field studies Carvalho et al. 2017b). Although chickens are
that have evaluated the impact of biological refractory to Leishmania infection, Sant’Anna
controls against sand fly vectors. Although et al. (2010) have shown that, this vertebrate
distinct classes of insecticides are available, provides valuable blood sources to support
sand fly resistance has been reported in Brazil the Lu. longipalpis population in peridomestic
and other endemic countries (Surendran et al. sites. The quality of chicken blood supports
2005, Lins et al. 2008, Hassan et al. 2012). Thus, the development of transmissible Leishmania
while studies on sand fly control are extremely infections in Lu. longipalpis (Sant’Anna et al.
relevant, other strategies than chemical control 2010).
are necessary. Besides blood, both females and males
feed on plant-derived sugar meals as a source
of energy. Sugary solutions such as nectar
FOOD SOURCE IDENTIFICATION or honeydew (secreted by plant-sucking
During the past decades, several studies have homopteran insects) and phloem sap are
been performed to identify the blood source ingested by sand flies by probing plant tissues
of engorged females of potential and proven with their mouthparts. Many studies have
vectors such as Lu. longipalpis. Initially, the addressed Lu. longipalpis plants preference.
precipitin test was the most common technique DNAs from Anacardiaceae, Meliaceae and
to identify blood meal (Dias et al. 2003, Camargo- Fabaceae families have been detected in the
Neves et al. 2007b, Missawa et al. 2008) and ELISA sand flies (Lima et al. 2016). More recently, the
(Marassá et al. 2006, Afonso et al. 2012). However, source of sand fly plant meals based on next
those techniques have some limitations, generation sequencing (NGS) of chloroplast DNA
such as the need to know the previous local gene ribulose bisphosphate carboxylase large
chain (rbcL) was assessed. Interestingly, the
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predilection of several sand fly species such as ceratopogonids) can help to clarify this subject
Lu. longipalpis for feeding on Cannabis sativa, and are fertile fields for entomologists.
a presumably illegal plant in some countries, Molecular studies have contributed to
was found (Abbasi et al. 2018). However, there understanding the events that occur during the
is still a lack of knowledge on how specific establishment of Leishmania infection in sand
sugars from plants may affect Leishmania flies (Ramalho-Ortigão et al. 2010). Leishmania
development in sand flies. It is already known molecules such as LPG (Pimenta et al. 1994,
that besides functioning as a source of energy, Svárovská et al. 2010), which binds to the sand
sugars may also be used by Leishmania during fly midgut galectin receptor PpGalec (Kamhawi
its establishment in the midgut. et al. 2004), sand fly digestive enzymes (Borovsky
& Schlein 1987, Schlein & Jacobson 1998,
Sant’Anna et al. 2009, Telleria et al. 2010) and
MIDGUT PHYSIOLOGY the peritrophic matrix (PM) (Pimenta et al. 1997)
The sand fly gut is divided into three main contribute to the success of the infection. The
regions: the foregut, the midgut, and the PM is a chitinous structure that envelopes the
hindgut. The cardia separates the foregut from bloodmeal along the entire midgut, separating
the midgut and the pyloric valve separates the ingested food from the midgut epithelium.
the midgut from the hindgut (Bates 2008). In most sand flies, this structure is formed
Most studies have focused on host-parasite between 12-24 h after blood ingestion and
interaction of suprapylarian Leishmania species degraded after 72h, when digestion is completed
(Assis et al. 2012). This development is restricted (Secundino et al. 2005, Sádlová & Volf 2009).
to the portion of the gut anterior to the pylorus, For more information about the Lu. longipalpis
mainly in the thoracic and abdominal midgut PM structure, composition, degradation and
(Lainson & Shaw 1987). This is different from synthesis kinetics see Secundino et al. (2005).
Viannia species whose development occurs The authors also have described a midgut
in the hindgut prior to migration to anterior muscle network of Lu. longipalpis.
parts. On the other hand, the mode of the The PM degradation after blood digestion
gut development is poorly recognized by the requires the activity of chitinases, which cleave
subgenera Mundinia and Sauroleishmania the chitin microfibril components of the matrix.
(Espinosa et al. 2018). For this reason, more Although Leishmania chitinase is believed to
studies on how species from these subgenera take part in the escape of the parasite from the
behave in their respective vectors are needed. PM, it is likely that a sand fly-derived chitinase
In this context, an early study (Luz et al. 1967) may also be involved. Ramalho-Ortigão & Traub-
reported a suprapylarian development for Le. Csekö (2003) have isolated and characterized a
enriettii in Pintomyia monticola, the suspected cDNA encoding a chitinase (Llchit1) from midgut
vector. However, this species, together with of Lu. longipalpis. Messenger RNA expression
Le. orientalis did not developed very well in indicates that this gene is induced upon blood
Lu. longipalpis (Seblova et al. 2015b, Chanmol feeding and reaches a peak at approximately
et al. 2019). Thus, studies with their suspected 72h post blood meal, presuming that this sand
vectors (phlebotomine sand flies and/or fly chitinase has a function in PM degradation
(Ramalho-Ortigão et al. 2005). Besides that,
Ortigão-Farias et al. (2018) have shown that
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alternative splicing generates chitinases with two cDNAs, Lltryp1 and Lltryp2, coding for
different domain structures. LlChit1A is present trypsin-like proteins in Lu. longipalpis. Lltryp1
in adult females post blood meal, L4 larvae and expression remains undetected until blood
pre-pupae, whereas LlChit1B and LlChit1C are feeding and reaches a peak at 12h post-blood
found in L4 larvae and disappear just before meal, returning to pre-blood meal levels after
pupation. 72h. Lltryp2, on the other hand, is constitutively
Serine proteases (trypsins and expressed at high levels in the non-blood fed
chymotrypsins) are the most abundant digestive female but is reduced upon blood feeding. At
enzymes in the midgut of sand flies. In addition the end of the digestive cycle, Lltryp2 regains its
to blood digestion, those proteases have been pre-blood meal levels (Telleria et al. 2007). The
implicated in Le. infantum establishment in pattern of trypsin expression in Lu. longipalpis
their respective insect vector, appearing to differs from the results obtained for the Old-
be detrimental to parasite survival during the World species Phlebotomus papatasi (Ramalho-
first 48 hours prior to their increase after this Ortigão & Traub-Csekö 2003). However, there is
period (Freitas et al. 2012). However, the same still lack of information on how proteases from
detrimental effect has not occurred in sand Ph. perniciosus and from other natural vectors
flies infected with L. major and L. donovani, affect the development of Le. infantum. The
suggesting that Leishmania mortality is not transcriptome analysis has demonstrated that
caused directly by sand fly proteases, but L. infantum infection can reduce the transcript
from toxic products of blood meal digestion. abundance of trypsin PperTryp3 in the midgut of
(Pruzinova et al. 2018). More studies are needed Ph. perniciosus (Dostálová et al. 2011). Although
to better understand the effect of proteases Lu. longipalpis and Ph. perniciosus may sustain
on Leishmania establishment within sand infection with Le. infantum, the kinetics of
flies. The opposite data may indicate distinct proteases in those vectors in parallel are yet to
effects of proteases in Leishmania species. be determined.
Sant’Anna et al. (2009) have reported that Studies on midgut pH as well as the
Leishmania mexicana was able to downregulate mechanisms involved in pH control are extremely
the trypsin secretion in Lu. longipalpis to its relevant, since Leishmania develops exclusively
own advantage, promoting their establishment in the sand fly gut and the digestive processes
in the midgut. Likewise, a decrease of trypsin are essentially enzymatic (Bates & Rogers 2004).
enzymatic activity in Lu. longipalpis infected There are three known mechanisms involved
by Le. infantum has been reported (Telleria et in the process of controlling gut pH. The first
al. 2010). Lutzomyia longipalpis trypsin 1 gene involves the loss of CO2 from ingested blood
knockdown through dsRNA microinjections into and the transport of different ions through the
the thorax of females, seems to enhance the plasmatic membrane of the enterocytes (Santos
survival of Le. mexicana in comparison with et al. 2008). Other physiological processes related
mock-injected controls. Altogether, those data to the alkalinization of the abdominal midgut
reinforce the inverse relationship between involves the presence of blood in the abdominal
the expression and production of trypsin and midgut composed by proteins and amino acids.
the establishment of Leishmania in the sand Those components cause midgut endocrine
fly midgut (Sant’Anna et al. 2009). Telleria et cells to release alkalinizing hormones, increasing
al. (2007) have identified and characterized gut pH favoring blood digestion (Santos et al.
An Acad Bras Cienc (2021) 93(3) e20200254 9 | 29FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
2011). The third mechanism act involves Proton- milieu (Soares et al. 2002, Coelho-Finamore et
Assisted Amino Acid Transporter (LuloPATs), al. 2011).
removing H+ ions from the gut lumen into the Early studies of Elnaiem have already
cytoplasm of the enterocytes (Nepomuceno et focused on the effect of a second blood meal in
al. 2020). However, alkalinization of the lumen the development of Lu. longipalpis (Elnaiem et
may occur by the entry of some amino acids al. 1992, 1994). Nowadays, most of the studies are
into the cytoplasm of enterocytes triggering a interested in how a second bloodmeal affects
luminal alkalinization mechanism independent Leishmania development. In this context, the
of LuloPATs (Nepomuceno et al. 2020). Some effects of sequential blood meals on longevity,
reports along the decades have shown the protein digestion, trypsin activity and Leishmania
influence of Leishmania on sand fly physiology development within Lu. longipalpis midgut
and such behavior most likely evolved to have been recently evaluated. The mortality
favor the development and transmission of of blood-fed females increases after a second
the parasite. Leishmania infantum is able to blood meal as compared to sugar-fed females
reduce the alkalinization in the vector midgut, and the trypsin activity was lower during the
decreasing the activity of proteases like trypsin, second gonotrophic cycle (Moraes et al. 2018).
resulting in a decreased supply of amino acids The authors have not observed difference in the
to the enterocytes favoring the development population size of Leishmania in the gut with
of the parasites during digestion (Santos et al. sequential blood meals. However, Serafim et al.
2014). (2018) have reported that sequential blood meals
There are few studies regarding midgut promoted Leishmania replication and reversed
physiology of Lu. longipalpis larvae. The anatomy metacyclogenesis to a leptomonad-like stage,
of the digestive tube of Lu. longipalpis larvae the retroleptomonad promastigote, enhancing
as well as the pH along the midgut have been the Lu. longipalpis infectivity. Needless to say,
described in Vale et al. (2007). The carbohydrases this paper was a landmark study, bringing new
α-amylase, present in the anterior midgut and information on parasite development after a
probably involved in the digestion of glycogen; second blood meal.
α-glucosidase, that completes the digestion
of glycogen in the posterior midgut, and a Salivary proteins
membrane bound trehalase, that probably In general, female sand flies, except autogenic
acts in the digestion of trehalose, seems to be species, need to ingest blood for egg
the most abundant within the midgut of the development and sugar for energy metabolism.
larvae (Moraes et al. 2012, Vale et al. 2012). The Saliva is essential in both types of feeding,
expression pattern of glycoside hydrolase genes playing different roles since it contains sets
in Lu. longipalpis larvae have been described of enzymes for blood and sugar feeding, as
by Moraes et al. (2014), where the catabolism α-amylase (Cavalcante et al. 2006). Early studies
of microbial carbohydrates in insects generally by Volf have shown the effect of salivary gland
involves β-1,3-glucanases, chitinases and proteins in Old World sand flies, in which the
digestive lysozymes. This is interesting because composition of sand fly saliva depend not only
Le. infantum LPG possess terminal β-1,3-glucoses on sex, but also on the physiological state of
that could be cleaved by those enzymes and the female (Volf et al. 2000). The salivary protein
perhaps contribute to the sand fly midgut sugar composition of Lu. longipalpis also depends on
An Acad Bras Cienc (2021) 93(3) e20200254 10 | 29FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
age and diet (Prates et al. 2008). The protein (Costa et al. 2004). Moreover, SGH seem to
content from unfed sand flies increased 94% increase the IL-17 expression in human peripheral
from the first to the fifth day after emergence and blood mononuclear cells (Teixeira et al. 2018).
such variation can be related to the synthesis Human volunteers exposed to laboratory-reared
of important enzymes for meal ingestion and Lu. longipalpis bites developed both humoral
initial digestion (Prates et al. 2008). A kinetic and cell-mediated immune response against
of protein content in salivary glands seems to sand fly saliva, presenting increased frequency
occur after the blood meal, in which a depletion of CD4+CD25+ and CD8+CD25+ T cells as well as
of total protein content has been observed with IFN-γ and IL-10 synthesis (Vinhas et al. 2007)
gradual increase in subsequent days, returning and moreover, inducing heme oxygenase-1
to similar basal values (Prates et al. 2008). The expression at bite site (Luz et al. 2018). These
findings of Volf for Old World sand flies and the studies confirm powerful immunomodulatory
further records of Prates for New World ones properties of saliva and help clarify how
could be generalized for sand flies worldwide, Leishmania takes advantage of them during the
in view of the salivary content appears to follow bite.
the same pattern in several sand fly species. BALB/c mice exposed to repeated Lu.
Blood-feeding causes tissue damage longipalpis bites have developed a diffuse
creating a hemorrhagic pool resulting from inflammatory infiltrate characterized by
probing and destruction of small capillaries. neutrophils, eosinophils, and macrophages when
In this environment Leishmania and saliva challenged with SGH (Silva et al. 2005). Antibodies
interact with different host cells including anti-saliva have also been detected in exposed
peripheral blood and resident cells in the mice, that presented significant increase of IgG
skin (Vasconcelos et al. 2014). It has been well and IgG1, but not IgG2a or IgG2b, suggesting a
documented that sand fly saliva possesses an predominant Th2 response with a putative
array of potent pharmacological components, role for immune complexes in cell recruitment
such as anticoagulants, anti-platelet, (Silva et al. 2005). Lu. longipalpis saliva is also
vasodilators, immunomodulators and anti- capable of inducing neutrophil and macrophage
inflammatory molecules. For more details about recruitment and of modulating their function
the inflammatory role of Lu. longipalpis saliva in (Silva et al. 2005, Teixeira et al. 2005, Araújo-
leishmaniasis see Prates et al. (2012). Santos et al. 2010, Prates et al. 2011, Carregaro
To know the effect of these molecules, et al. 2013). Neutrophil and macrophage activity
most studies on sand fly saliva have used seem to be impaired in the presence of saliva
experimental animals (mice), and to a lesser resulting in cell apoptosis, production of PGE2
extent human cell. Salivary gland homogenates and LTB4 promoting increased parasite survival
(SGH) of Lu. longipalpis induce an increase of (Monteiro et al. 2005, Araújo-Santos et al. 2010,
IL-6, IL-8 and IL-12p40 and inhibits TNF-α and Prates et al. 2011). Lutzomyia longipalpis saliva
IL-10 production by human monocytes. SGH enhances Le. amazonensis infection affecting
have also influenced the expression of cell the macrophage function by upregulation of
surface molecules such as MHC class II, CD80 IL-10 and downregulation of NO production
and CD86 on antigen-presenting cells, except on (Norsworthy et al. 2004). The same regulation
dendritic cells, representing a critical point for pattern of immune response has been described
the development of a protective Tcell response in BALB/c mice experimentally infected with Le.
An Acad Bras Cienc (2021) 93(3) e20200254 11 | 29FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
major, in which a considerable increase of IL-10 a strong Th1 type immune response was
and IFN-γ was detected, inducing preferentially observed in immunized C57BL/6 mice infected
type-2 cytokines and the sequential migration with Le. major (Xu et al. 2011) and in BALB/c
of neutrophils, eosinophils, and CD4+ CD45RBlow mice infected with Le. braziliensis (Cunha et al.
cells (Monteiro et al. 2007). However, Laurenti 2018). Immunization with salivary protein LJM19
et al. (2009) have reported that SGH from wild- induced protection in hamsters challenged with
caught Lu. longipalpis have determined lower Le. braziliensis (Tavares et al. 2011). The presence
production of IL-4 and IL-10 but higher IL-12 levels of smaller lesion sizes as well as reduced parasite
in C57BL/6 compared with laboratory-reared burdens both at lesion sites and in the draining
SGH. These findings may indicate a probable lymph nodes, was associated with a significant
bias by using SGH from laboratory-colonized decrease in the expression levels of IL-10 and
sand flies instead of wild-caught vector SGH. TGF-β and increased IFN-γ expression have been
In addition, it indicates differences on immune reported (Tavares et al. 2011). Both LJM17 and
response of the most used experimental models LJL143-immunized dogs have presented a mixed
for studies concerning saliva effects (Laurenti et (Th1/Th2) immune response and moreover,
al 2009). However, it is important to note that increased IFN-γ production (Abbehusen et al.
sand flies also inject their microbiota together 2018), providing immune responses qualitatively
with the salivary content, and the presence of similar to those previously obtained by Collin
distinct bacteria within laboratory-colonized et al. (2009). Although knowing specifically the
sand flies compared to wild-caught ones, can activity of a given molecule, the use of several
also influence the immune response. The antigens that do not exhibit antagonistic
presence of SGH from Lu. longipalpis was able properties could help the development of more
to differentially modulate the course of the potent saliva-based vaccines.
lesion and macrophage differentiation in Cavia Valenzuela et al. (2004) have isolated
porcellus caused by avirulent and virulent Le. and identified the most abundant secreted
enriettii strains (Pinheiro et al. 2018). Several proteins from the salivary glands of Lu.
basic studies, especially those that used needle longipalpis using massive cDNA sequencing,
models, were very important for understanding proteomics and customized computational
the Leishmania infection. However, there is an biology approaches. However, several proteins
urgent need that from now on, transmission coded by their corresponding salivary gland
needle studies use saliva at least from a transcripts remain without a defined function
colonized sand fly vector. Although, for obvious until today (Valenzuela et al. 2004, Anderson et
reasons, it is not possible to use the natural al. 2006). Likewise, some biological functions
pairs depending on the Leishmania species, described in the salivary gland have not been
most of the properties of the saliva of different associated with a specific protein. For example,
sand flies share similar effects. the anticoagulant of Lu. longipalpis remained
Most of the studies above have used SGH, but elusive for decades until Collin et al. (2012)
it seems that the search for specific molecules describe Lufaxin (Lutzomyia longipalpis Factor
has been the target for by several groups. Xa inhibitor). This recombinant protein has
Consistent with this observation, the structure potent and specific anticoagulant activity toward
and function of LJM11 has been described by FXa, impairing protease-activated receptor 2
Xu et al. (2011). A protective immunity driving activation and, consequently inhibiting the
An Acad Bras Cienc (2021) 93(3) e20200254 12 | 29FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
inflammation and thrombosis in C57BL/6 mice. cells. Moreover, MAX seemed to upregulate the
New insights of recombinant hyaluronidase cytokines associated with a type-2 response (IL-
(LuloHya) and Lutzomyia NET destroying 10, IL-6, and TGF-β) and downregulated type-1
protein (Lundep), the proteins responsible for cytokines (IL-12p70 and TNF-α), NO and CCR7.
the hyaluronidase and endonuclease activities This enhanced parasite survival in the vertebrate
have been described (Chagas et al. 2014, Martin- host in the early stages of infection (Brodie et al.
Martin et al. 2018). Lundep seems to increase 2007, Wheat et al. 2008). MAX was also able to
Le. major survival, destroy neutrophil traps drive plasma leakage via PAC1–CXCR1/2-pathway
and inhibits XIIa contact activation in human (Svensjö et al. 2009, 2012). A protective effect
plasma. The relationship between Leishmania against Le. major infection in murine models
parasites and sand flies hyaluronidase was first has also been reported for MAX (Wheat et al.
described by Volfova et al. (2008). The authors 2017).
have shown that co-inoculation of parasites with Anti-saliva antibodies can be used to assess
hyaluronidase enhances Leishmania infection. exposure of humans and other Leishmania hosts
Altogether, those data indicate that saliva is an to sand fly bites (Rohousova et al. 2005, Bahia et
endless subject and several factors are still to al. 2007, Vinhas et al. 2007, Hostomska et al. 2008,
be defined and how to block those molecules Fraga et al. 2016). These anti-saliva antibodies
is an open field for alternative tools against seem to be species-specific as shown by Volf &
transmission. Rohousova (2001) and Rohousova et al. (2005).
Lutzomyia longipalpis is able to feed on The antibodies of hosts bitten by Old-World
several mammal and bird species (Afonso et al. sand flies did not cross-react with Lu. longipalpis
2012). For this reason, an arsenal of complement SGH. Therefore, this specificity of anti-saliva
inhibitors is needed to protect this species. In antibodies enables to measure/estimate the
this context, Lu. longipalpis saliva was able to exposure to a particular species. Also, the
inhibit the serum complement activation from a protective effect of immunization by saliva have
wide range of vertebrates, including dogs, guinea been species-specific as shown by Thiakaki et
pigs and rats (Mendes-Sousa et al. 2013). Studies al. (2005): mice have been protected against co-
involving the human complement inhibition inoculation of Leishmania with Lu. longipalpis
by Lu. longipalpis saliva have shown at least saliva only if they were preimmunized by SGL
two inhibitors of the classical pathway in this of Lu. longipalpis but not if preimmunized by
species. The first is a Salivary Anti-complement SGL of Phlebotomus species. Nine recombinant
from Lu. longipalpis (SALO) (Ferreira et al. 2016), salivary proteins were developed and tested for
considered a leishmaniasis vaccine candidate immunogenicity and specificity in mammalian
(Asojo et al. 2017) and the second, a soluble hosts (Teixeira et al. 2010). The recombinant
intestinal inhibitor (Saab et al. 2020). proteins LJM17 and LJM11, both belonging to
One of the most studied salivary peptides the insect “yellow” family of proteins, were
is the potent vasodilator maxadilan (MAX). potential markers of exposure to sand fly bite
MAX also seems immuno-modulate the host (Souza et al. 2010). LJM17 was recognized by
immune response. MAX treatment reduced the human, dog, and fox sera and LJM11 by humans
surface expression of CD80 on CD11c+ dendritic and dogs. Notably, LJM17 and LJM11 were
cells and resulted in a concomitant increase in specifically recognized by humans exposed to
CD86 expression on a subpopulation of these Lu. longipalpis but not by individuals exposed
An Acad Bras Cienc (2021) 93(3) e20200254 13 | 29FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
to Nyssomyia intermedia (Teixeira et al. 2010). A for terminal N-acetyl-galactosamine (GalNAc)
recent paper has shown that one of the salivary present on O-linked glycoconjugates, bound
proteins of Ny. intermedia, LinB-13, could be a to midgut proteins from permissive but not
useful marker for the development of a more from specific vectors (Myšková et al. 2007). The
severe cutaneous leishmaniasis (Carvalho et characterization of O-linked glycoconjugate
al. 2017a). This study opens the possibility that of Lu. longipalpis has revealed the presence
similar mechanisms could also happen in the of mucin-like properties, GPI-anchored in the
viscerotropic Leishmania species transmitted by membrane of enterocytes and localized it on the
Lu. longipalpis, especially in canine infection, luminal side of the midgut (Myšková et al. 2016).
that is a very susceptible host compared to As Leishmania undergo metacyclogenesis
humans. and acquire infectivity within the sand fly
gut, they secrete a unique class of serine-
rich proteophosphoglycans (PPGs); which
HOST-PATHOGEN INTERACTIONS condense to form a gel in which the parasites
Laboratory studies on sand fly competence to are embedded (Rogers & Bates 2007). PPGs are
Leishmania parasites suggest that the sand flies synthesized by all species of Leishmania in
fall into two groups. Several species are termed vitro and the promastigote secretory gel (PSG)
specific/restricted vectors that support the has been observed in all Leishmania-sand
development of one Leishmania species. On the fly combinations examined to date. The Le.
other hand, permissive vectors are susceptible infantum PPGs regurgitated by the bite of Lu.
to various Leishmania parasites (Volf & Myskova longipalpis promote parasite establishment in
2007, Dostálová & Volf 2012). The presence of the mouse skin and skin-distant tissues, reinforcing
permissive vector Lu. longipalpis in Latin America PSG as an important part of Le. infantum
was crucial for the establishment of L. infantum transmission and visceral infection (Rogers et al.
from Mediterranean to this continent (Volf & 2010). The binding of Leishmania promastigotes
Myskova 2007). Another factor that seems to to the midgut epithelium is regarded as an
affect the establishment of Leishmania in sand essential part of the lifecycle in the sand fly
flies is the temperature. Leishmania infantum vector, enabling the parasites to persist beyond
and Le. braziliensis have developed well in the initial blood meal phase and establish
Lu. longipalpis at 20 and 26 degrees C, while the infection. Wilson et al. (2010) have shown
Le. peruviana, a mountain species, developed that Leishmania gut binding is strictly stage-
well in sand fly females kept at 20 degrees C dependent and is a property of those forms
(Hlavacova et al. 2013). Previous studies have found in the middle phase of development
suggested that for ‘specific’ vectors, successful (nectomonad and leptomonad forms) but is
parasite development is mediated by parasite absent in the early blood meal and final stages
surface glycoconjugates and sand fly lectins. (procyclic and metacyclic forms). Furthermore,
However, Myšková et al. (2007) have shown that the adhesion is affected by glycoconjugates on
interactions involving ‘permissive’ vectors, as Leishmania surface, especially LPG and gp63
Lu. longipalpis utilize other molecules of the (Jecna et al. 2013).
midgut epithelium as a parasite ligand. The Significant advances have been made
Helix pomatia agglutinin (HPA), a lectin specific in exploring Leishmania-vector interactions
throughout the last two decades, especially
An Acad Bras Cienc (2021) 93(3) e20200254 14 | 29FELIPE D. RÊGO & RODRIGO PEDRO SOARES AN OVERVIEW ON Lutzomyia longipalpis
on permissiveness of Lu. longipalpis. The In mixed infections of the permissive sand fly
development of Le. infantum from establishment Lu. longipalpis, paralyzed promastigotes and
of infection to metacyclogenesis as well as the uncoordinated swimmers of Le. mexicana were
transmission dynamics by the bite to BALB/c severely diminished in the sand fly after the
mice and golden hamster have been described blood digestion. Furthermore, the parasites have
(Maia et al. 2011, Freitas et al. 2012, Secundino not reached the anterior regions of the midgut,
et al. 2012). For the first time Ph. perniciosus suggesting that L. mexicana needs directional
and Lu. longipalpis have been co-infected with motility for successful colonization of sand
transgenic promastigotes of Le. donovani strains flies (Beneke et al. 2019). The relationship
carrying hygromycin or neomycin resistance between the zinc protease gp63 and the parasite
genes (Sadlova et al. 2011). Seblova et al. (2015a) development in the sand fly vector has been
have tested the development of Le. infantum/ evaluated (Hajmová et al. 2004). Leishmania
Leishmania donovani natural hybrid (CUK strain) amazonensis gp63-downregulated have
in Lu. longipalpis and the biological behavior presented a weak development especially in
appeared similar to what has been observed the early phase of infection, indicating that gp63
in the natural vector Phlebotomus tobbi. The may protect promastigotes from degradation by
phenotype impact of miltefosine-resistant Le. the midgut digestive enzymes, favoring parasite
infantum has been evaluated on Lu. longipalpis survival. More recently, trying to understand the
showing a significant reduction in sand fly concomitant roles of gp63 and LPG, Soares et al.
infection, stomodeal valve colonization and (2017) evaluated those two glycoconjugates using
differentiation into metacyclic forms compared the midgut in vitro system (Pimenta et al. 1992)
to the isogenic parent susceptible strain and LL5 cells. Both glycoconjugates were equally
(Bockstal et al. 2019). Paromomycin-resistant responsible for inhibiting parasite attachment
Le. infantum (MHOM/FR/96/LEM3323-cl4) has in those models reinforcing their importance for
behaved similar to those WT, in terms of infection interaction with the invertebrate host.
and parasite location within Lu. longipalpis, Parasites of the subgenus Leishmania
and are able to colonize the stomodeal valve (Mundinia) (Espinosa et al. 2018) are becoming
with metacyclic forms (Hendrickx et al. 2020). increasingly important to human health, since
However, the mechanisms underlying drug- some species have been reported to infect
resistance phenotype during infection in the humans, such as Le. martiniquensis, Le. “Ghana
sand fly are yet to be determined. strain”, and Le. orientalis (previously called “Le.
In laboratory conditions Lu. longipalpis siamensis”) (Pothirat et al. 2014, Chiewchanvit et
supports infection of other Leishmania species, al. 2015, Kwakye-Nuako et al. 2015, Jariyapan et al.
besides Le. infantum. However, aflagellated 2018). The two other known species, Le. enrietti,
Le. amazonensis promastigotes (Ld ARL- have been found in guinea pigs (Cavia porcellus),
3A-Q70L-overexpressing) did not survive in and Le. macropodum (previously called “Le. sp.
experimentally infected Lu. longipalpis, in AM-2004”), have been found in red kangaroos
contrast to untransfected or native Ld ARL- and other macropods (Rose et al. 2004, Dougall
3A overexpressing cells (Cuvillier et al. 2003). et al. 2011, Barratt et al. 2017). Some authors have
The role of Leishmania flagellar proteins in evaluated the biological behavior of Leishmania
establishment of the parasite in the vector have (Mundinia) parasites in permissive vectors, such
been recently explored by Beneke et al. (2019). as Lu. longipalpis in view of the uncertainty
An Acad Bras Cienc (2021) 93(3) e20200254 15 | 29You can also read
