Mosquito pericardial cells upregulate Cecropin expression after an immune challenge.

Most mosquito-transmitted pathogens grow or replicate in the midgut before invading the salivary glands. Pathogens are exposed to several immunological factors along the way. Recently, it was shown that hemocytes gather near the periostial region of the heart to efficiently phagocytose pathogens circulating in the hemolymph. Nerveless, not all pathogens can be phagocyted by hemocytes and eliminated by lysis. Interestingly, some studies have shown that pericardial cells (PCs) surrounding periostial regions, may produce humoral factors, such as lysozymes. Our current work provides evidence that Anopheles albimanus PCs are a major producer of Cecropin 1 (Cec1). Furthermore, our findings reveal that after an immunological challenge, PCs upregulate Cec1 expression. We conclude that PCs are positioned in a strategic location that could allow releasing humoral components, such as cecropin, to lyse pathogens on the heart or circulating in the hemolymph, implying that PCs could play a significant role in the systemic immune response.

Effect of juvenile hormone on phenoloxidase and hemocyte number: The role of age, sex, and immune challenge.

Hormones are key factors in determining the response of organisms to their environment. For example, the juvenile hormone (JH) coordinates the insects' development, reproduction, and survival. However, it is still unclear how the impact of juvenile hormone on insect immunity varies depending on the sex and reproductive state of the individual, as well as the type of the immune challenge (i.e., Gram-positive or Gram-negative bacteria). We used Tenebrio molitor and methoprene, a JH analog (JHa) to explore these relationships. We tested the effect of methoprene on phenoloxidase activity (PO), an important component of humoral immunity in insects, and hemocyte number. Lyophilized Gram-positive Staphylococcus aureus or Gram-negative Escherichia coli were injected for the immune challenge. The results suggest that JH did not affect the proPO, PO activity, or hemocyte number of larvae. JH and immune challenge affected the immune response and consequently, affected adult developmental stage and sex. We propose that the influence of JH on the immune response depends on age, sex, the immune response parameter, and the immune challenge, which may explain the contrasting results about the role of JH in the insect immune response.

Plasmodium exposure alters midgut epithelial cell dynamics during the immune memory in Anopheles albimanus.

Immunological priming in insects is defined as a previous contact with non-virulent pathogens, which induces protection after a second virulent infection. The mechanism of this process is not well understood. We have observed midgut DNA synthesis (endoreplication) in Plasmodium berghei exposure mosquitoes (primed) and after the immune challenge, which could be an essential component of the priming response in the mosquito. Endoreplication requires cell cycle components re-direction to make multiple DNA copies. Therefore, it is fundamental to understand the role of cell cycle components in priming. Here, we analyzed the expression of the cyclins A, B, E, and AurkA, and the endoreplication components NOTCH and HNT in the mosquito Anopheles albimanus; after priming with non-infective Plasmodium berghei and challenged with an infective P. berghei. The overexpression of cell cycle elements occurred seven days after priming with a quick reduction 24 h after the challenge. Hnt and NOTCH overexpression occurred 24 h after priming. Antimicrobial peptide cecropin is quickly overexpressed after 24 h in primed mosquitoes, then is downregulated at day seven and overexpressed again after parasite challenge. We also found that DNA synthesis occurs in cells with different nuclear sizes, suggesting a change in midgut epithelial dynamics after Plasmodium exposure. Inhibition of DNA synthesis via cisplatin revealed that DNA synthesis is required for priming to limit Plasmodium infection. Our results indicate the importance of cell cycle components on DNA synthesis and Notch pathway during priming response in An. albimanus mosquitoes.

Development of the indirect flight muscles of Aedes aegypti, a main arbovirus vector.

BACKGROUND: Flying is an essential function for mosquitoes, required for mating and, in the case of females, to get a blood meal and consequently function as a vector. Flight depends on the action of the indirect flight muscles (IFMs), which power the wings beat. No description of the development of IFMs in mosquitoes, including Aedes aegypti, is available. METHODS: A. aegypti thoraces of larvae 3 and larvae 4 (L3 and L4) instars were analyzed using histochemistry and bright field microscopy. IFM primordia from L3 and L4 and IFMs from pupal and adult stages were dissected and processed to detect F-actin labelling with phalloidin-rhodamine or TRITC, or to immunodetection of myosin and tubulin using specific antibodies, these samples were analyzed by confocal microscopy. Other samples were studied using transmission electron microscopy. RESULTS: At L3-L4, IFM primordia for dorsal-longitudinal muscles (DLM) and dorsal-ventral muscles (DVM) were identified in the expected locations in the thoracic region: three primordia per hemithorax corresponding to DLM with anterior to posterior orientation were present. Other three primordia per hemithorax, corresponding to DVM, had lateral position and dorsal to ventral orientation. During L3 to L4 myoblast fusion led to syncytial myotubes formation, followed by myotendon junctions (MTJ) creation, myofibrils assembly and sarcomere maturation. The formation of Z-discs and M-line during sarcomere maturation was observed in pupal stage and, the structure reached in teneral insects a classical myosin thick, and actin thin filaments arranged in a hexagonal lattice structure. CONCLUSIONS: A general description of A. aegypti IFM development is presented, from the myoblast fusion at L3 to form myotubes, to sarcomere maturation at adult stage. Several differences during IFM development were observed between A. aegypti (Nematoceran) and Drosophila melanogaster (Brachyceran) and, similitudes with Chironomus sp. were observed as this insect is a Nematoceran, which is taxonomically closer to A. aegypti and share the same number of larval stages.

The Search of a Malaria Vaccine: The Time for Modified Immuno-Potentiating Probes.

Malaria is a deadly disease that takes the lives of more than 420,000 people a year and is responsible for more than 229 million clinical cases globally. In 2019, 95% of malaria morbidity occurred in African countries. The development of a highly protective vaccine is an urgent task that remains to be solved. Many vaccine candidates have been developed, from the use of the entire attenuated and irradiated pre-erythrocytic parasite forms (or recombinantly expressed antigens thereof) to synthetic candidates formulated in a variety of adjuvants and delivery systems, however these have unfortunately proven a limited efficacy. At present, some vaccine candidates are finishing safety and protective efficacy trials, such as the PfSPZ and the RTS,S/AS01 which are being introduced in Africa. We propose a strategy for introducing non-natural elements into target antigens representing key epitopes of Plasmodium spp. Accordingly, chemical strategies and knowledge of host immunity to Plasmodium spp. have served as the basis. Evidence is obtained after being tested in experimental rodent models for malaria infection and recognized for human sera from malaria-endemic regions. This encourages us to propose such an immune-potentiating strategy to be further considered in the search for new vaccine candidates.

Lysozyme c-1 gene is overexpressed in Anopheles albimanus pericardial cells after an immune challenge.

Different evidences suggest that pericardial cells play an important role during the immune response against pathogens that invade the mosquito hemocoel. Previously, we identified two lysozyme genes in Anopheles albimanus heart transcriptome. The present study showed that one of these genes (IDVB: AALB004517) has high percentage of identity to mosquito lysozyme genes related to immunity, suggesting its possible participation during the mosquito immune response. This An. albimanus gen, constitutively expressed lysozyme c-1 mRNA (albLys c-1) in mosquito heart; however, it was overexpressed in bacteria-injected mosquitoes. In heart extract samples, we identified a protein of approximately 14 kDa (likely lysozyme c-1), which lysed M. luteus. In addition, mRNA-FISH assay in heart samples, showed specific fluorescent hybridization signal in pericardial cells from M. luteus-injected mosquitos. We conclude that for the first time an inducible immune factor (lysozyme c-1) is identified in Anopheles albimanus mosquito pericardial cells, which could be a key component in the response against pathogens that interact with the mosquito heart.

DNA synthesis increases during the first hours post-emergence in Anopheles albimanus mosquito midgut.

In hematophagous insects, the midgut is a fundamental barrier against infections and limits the development and transmission of pathogens. However, in mosquitoes, cell differentiation, proliferation, and cell cycle process in the midgut have not been characterized. Here we provide evidence of how cell cycle progression occurs in the newly emerged Anopheles albimanus mosquito midgut and describing cyclins expression as mediators of the cell cycle. The cell cycle at different post-emergence times was evaluated in disaggregated cells from midgut tissue using flow cytometry. Also, cyclins A, B, and E were identified by bioinformatics tools. These cyclins were used to analyze cell cycle progression. Flow cytometry data and the expression-pattern of the cyclins by qRT-PCR supported a polyploidy process, besides mitosis marker was marginally detected and only in newly emerged mosquitoes. Our results suggest that DNA increment in midguts occurs by polyploidy during the first hours post-emergence.

Juvenile hormone controls ovarian development in female Anopheles albimanus mosquitoes.

Anophelinae mosquitoes are vectors of human malaria, a disease that infects hundreds of millions of people and causes almost 600,000 fatalities annually. Despite their medical importance, laboratory studies on key aspects of Anophelinae reproductive biology have been limited, and in particular, relatively little is known about the role of juvenile hormone (JH) in the control of female reproduction. The study presented here attempts to fill a gap of knowledge in our understanding of the JH control of ovarian development in female Anophelinae mosquitoes, using Anopheles albimanus as a model. Our studies revealed that JH controls the tempo of maturation of primary follicles in An. albimanus in a similar manner to that previously described in Aedes aegypti. At adult eclosion JH hemolymph titer was low, increased in 1-day old sugar-fed insects, and decreased in blood fed individuals. JH titers decreased if An. albimanus females were starved, and were reduced if insects emerged with low teneral reserves, precluding previtellogenic ovarian development. However, absolute hemolymph titers were lower than Ae. aegypti. Decapitation experiments suggested that if teneral reserves are sufficient, factors from the head activate JH synthesis by the corpora allata (CA) during the first 9-12 h after adult emergence. In conclusion, our studies support the hypothesis that JH controls previtellogenic ovarian development in female An. albimanus mosquitoes, in a similar manner that have been described in Culicinae.

DNA Synthesis Is Activated in Mosquitoes and Human Monocytes During the Induction of Innate Immune Memory.

Endoreplication is a cell cycle program in which cells replicate their genomes without undergoing mitosis and cytokinesis. For the normal development of many organisms (from fungi to humans) and the formation of their organs, endoreplication is indispensable. The aim of the present study was to explore whether endoreplication and DNA synthesis are relevant processes during the induction of trained innate immunity in human monocytes and in the Anopheles albimanus mosquito cell line. During the induction of trained immunity in both models, endoreplication markers were overexpressed and we observed an increase in DNA synthesis with an augmented copy number of genes essential for trained immunity. Blocking DNA synthesis prevented trained immunity from being established. Overall, these findings suggest that DNA synthesis and endoreplication are important mechanisms involved in inducing innate immune memory. They have probably been conserved throughout evolution from invertebrates to humans.

De Novo DNA Synthesis in Aedes aegypti Midgut Cells as a Complementary Strategy to Limit Dengue Viral Replication.

Aedes aegypti is the main vector of Dengue Virus, carrying the virus during the whole mosquito life post-infection. Few mosquito fitness costs have been associated to the virus infection, thereby allowing for a swift dissemination. In order to diminish the mosquito population, public health agency use persistent chemicals with environmental impact for disease control. Most countries barely use biological controls, if at all. With the purpose of developing novel Dengue control strategies, a detailed understanding of the unexplored virus-vector interactions is urgently needed. Damage induced (through tissue injury or bacterial invasion) DNA duplication (endoreplication) has been described in insects during epithelial cells renewal. Here, we delved into the mosquito midgut tissue ability to synthesize DNA de novo; postulating that Dengue virus infection could trigger a protective endoreplication mechanism in some mosquito cells. We hypothesized that the Aedes aegypti orthologue of the Drosophila melanogaster hindsight gene (not previously annotated in Aedes aegypti transcriptome/genome) is part of the Delta-Notch pathway. The activation of this transcriptional cascade leads to genomic DNA endoreplication. The amplification of the genomic copies of specific genes ultimately limits the viral spreading during infection. Conversely, inhibiting DNA synthesis capacity, hence endoreplication, leads to a higher viral replication.

JH biosynthesis and hemolymph titers in adult male Aedes aegypti mosquitoes.

Juvenile hormone (JH) is a major hormonal regulator in insects. In Aedes aegypti females, JH signals the completion of the ecdysis to the adult stage and initiates reproductive processes. Although the regulation of JH synthesis and titer in Ae. aegypti females has been extensively studied, relatively little is known about changes of JH synthesis and titers in male mosquitoes, as well as on the roles of JH controlling male reproductive biology. A better understanding of male mosquito reproductive biology, including an improved knowledge of the hormonal control of reproduction, could increase the likelihood of success of male-targeting vector control programs. Using a high performance liquid chromatography coupled to electrospray tandem mass spectrometry method, we measured JH biosynthesis and hemolymph levels in male mosquitoes during pupal and adult stages. Our results revealed tightly concomitant changes in JH biosynthesis and JH hemolymph titers. Synthesis of JH III was very low in late pupae, significantly increased during the first 24 h after adult eclosion, and then remained relatively constant during the first six days after adult eclosion. Feeding high sugar diets resulted in an increase of JH synthesis and titers, and starvation significantly decreased JH synthesis, but this effect could be reversed by changing the males back to a high sugar diet. JH synthesis rates were similar in virgin and mated males, but hemolymph JH levels were different in well-nourished virgin and mated males. Starvation resulted in a significant reduction in insemination rates; with well-nourished males inseminating 2 times more females than water-fed. Giving a 20% sugar meal for 24 h to those mosquitoes that were previously starved for 6 days, caused a significant rise in insemination rates, restoring them to levels similar to those recorded for 20% fed males. These results suggest that nutrition plays a role on male fecundity, and this effect might be mediated by JH.

Allatotropin: A pleiotropic neuropeptide that elicits mosquito immune responses.

Allatotropins (AT) are neuropeptides with pleotropic functions on a variety of insect tissues. They affect processes such as juvenile hormone biosynthesis, cardiac rhythm, oviduct and hindgut contractions, nutrient absorption and circadian cycle. The present work provides experimental evidence that AT elicits immune responses in two important mosquito disease vectors, Anopheles albimanus and Aedes aegypti. Hemocytes and an immune-competent mosquito cell line responded to AT by showing strong morphological changes and increasing bacterial phagocytic activity. Phenoloxidase activity in hemolymph was also increased in Ae. aegypti mosquitoes treated with AT but not in An. albimanus, suggesting differences in the AT-dependent immune activation in the two species. In addition, two important insect immune markers, nitric oxide levels and expression of antimicrobial peptide genes, were increased in An. albimanus guts after AT treatment. AT conjugated to quantum dot nanocrystals (QDots) specifically labeled hemocytes in vivo in both mosquito species, implying molecular interactions between AT and hemocytes. The results of our studies suggest a new role for AT in the modulation of the immune response in mosquitoes.

Somatostatin signaling system as an ancestral mechanism: Myoregulatory activity of an Allatostatin-C peptide in Hydra.

The coordination of physiological processes requires precise communication between cells. Cellular interactions allow cells to be functionally related, facilitating the maintaining of homeostasis. Neuropeptides functioning as intercellular signals are widely distributed in Metazoa. It is assumed that neuropeptides were the first intercellular transmitters, appearing early during the evolution. In Cnidarians, neuropeptides are mainly involved in neurotransmission, acting directly or indirectly on epithelial muscle cells, and thereby controlling coordinated movements. Allatostatins are a group of chemically unrelated neuropeptides that were originally characterized based on their ability to inhibit juvenil hormone synthesis in insects. Allatostatin-C has pleiotropic functions, acting as myoregulator in several insects. In these studies, we analyzed the myoregulatory effect of Aedes aegypti Allatostatin-C in Hydra sp., a member of the phylum Cnidaria. Allatostatin-C peptide conjugated with Qdots revealed specifically distributed cell populations that respond to the peptide in different regions of hydroids. In vivo physiological assays using Allatostatin-C showed that the peptide induced changes in shape and length in tentacles, peduncle and gastrovascular cavity. The observed changes were dose and time dependent suggesting the physiological nature of the response. Furthermore, at highest doses, Allatostatin-C induced peristaltic movements of the gastrovascular cavity resembling those that occur during feeding. In silico search of putative Allatostatin-C receptors in Cnidaria showed that genomes predict the existence of proteins of the somatostatin/Allatostatin-C receptors family. Altogether, these results suggest that Allatostatin-C has myoregulatory activity in Hydra sp, playing a role in the control of coordinated movements during feeding, indicating that Allatostatin-C/Somatostatin based signaling might be an ancestral mechanism.

Plasmodium berghei induced priming in Anopheles albimanus independently of bacterial co-infection.

Priming in invertebrates is the acquired capacity to better combat a pathogen due to a previous exposure to sub-lethal doses of the same organism. It is proposed to be functionally analogous to immune memory in vertebrates. Previous studies with Anopheles gambiae mosquitoes provide evidence that the inhibitory response to a second challenge by the malaria parasite Plasmodium berghei resulted from a sustained activation of hemocytes by midgut bacteria. These bacteria probably accessed the hemolymph during a first aborted infection through lesions produced by parasites invading the midgut. Since the mosquito immune responses to midgut bacteria and Plasmodium overlap, it is difficult to determine the priming responses of each. We herein document priming induced in the aseptic An. albimanus midgut by P. berghei, probably independent of the immune response induced by midgut bacteria. This idea is further evidenced by experiments with Pbs 25-28 knock out parasites (having an impaired capacity for invading the mosquito midgut) and dead ookinetes. Priming protection against a homologous challenge with P. berghei lasted up to 12 days. There was greater incorporation of 5-bromo-2'-deoxyuridine into midgut cell nuclei (indicative of DNA synthesis without mitosis) and increased transcription of hnt (a gene required for the endocycle of midgut cells) in primed versus unprimed mosquitoes, suggesting that endoreplication was the underlying mechanism of priming. Moreover, the transcription of hnt and antimicrobial peptides related to an anti-Plasmodium response (attacin, cecropin and gambicin) was enhanced in a biphasic rather than sustained response after priming An. albimanus with P. berghei.

Coordinated changes in JH biosynthesis and JH hemolymph titers in Aedes aegypti mosquitoes.

Juvenile hormone III (JH) is synthesized by the corpora allata (CA) and plays a key role in mosquito development and reproduction. A decrease in JH titer during the last instar larvae allows pupation and metamorphosis to proceed. As the anti-metamorphic role of JH comes to an end, the CA of the late pupa once again synthesizes JH, which plays an essential role in orchestrating reproductive maturation. In spite of the importance of Aedes aegypti as a vector, a detailed study of the changes of JH hemolymph titers during the gonotrophic cycle has never been performed. In the present studies, using a high performance liquid chromatography coupled to a fluorescent detector (HPLC-FD) method, we measured changes in JH levels in the hemolymph of female mosquitoes during the pupal and adult stages. Our results revealed tightly concomitant changes in JH biosynthesis and JH hemolymph titers during the gonotrophic cycle of female mosquito. Feeding high sugar diets resulted in an increase of JH titers, and mating also modified JH titers in hemolymph. In addition these studies confirmed that JH titer in mosquitoes is fundamentally determined by the rate of biosynthesis in the CA.

Development and glycoprotein composition of the perimicrovillar membrane in Triatoma (Meccus) pallidipennis (Hemiptera: Reduviidae).

Hemipterans and thysanopterans (Paneoptera: Condylognatha) differ from other insects by having an intestinal perimicrovillar membrane (PMM) which extends from the base of the microvilli to the intestinal lumen. The development and composition of the PMM in hematophagous Reduviidae depend on factors related to diet. The PMM may also allow the human parasite Trypanosoma cruzi, the etiological agent of human Chagas Disease, to establish and develop in this insect vector. We studied the PMM development in the Mexican vector of Chagas Disease, Triatoma (Meccus) pallidipennis. We describe changes in the midgut epithelial cells of insects in response to starvation, and at different times (10, 15 and 20 days) after bloodfeeding. In starved insects, the midguts showed epithelial cells closely connected to each other but apparently free of PMM with some regions being periodic acid-Schiff (PAS-Schiff) positive. In contrast, the PMM was evident and fully developed in the midgut region of insects 15 days after feeding. After this time, the PMM completely covered the microvilli and reached the midgut lumen. At 15 days following feeding the labeled PAS-Schiff increased in the epithelial apex, suggesting an increase in carbohydrates. Lectins as histochemical reagents show the presence of a variety of glycoconjugates including mannose, glucose, galactosamine, N-acetyl-galactosamine. Also present were N-acetyl-glucosamine and sialic acid which contribute to the successful establishment and replication or T. cruzi in its insect vectors. By means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the formation and structure of the PMM is confirmed at 15 days post feeding. Our results confirmed the importance of the feeding processes in the formation of the PMM and showed the nature of the biochemical composition of the vectors' intestine in this important Mexican vector of Chagas disease.

Allatotropin: an ancestral myotropic neuropeptide involved in feeding.

BACKGROUND: Cell-cell interactions are a basic principle for the organization of tissues and organs allowing them to perform integrated functions and to organize themselves spatially and temporally. Peptidic molecules secreted by neurons and epithelial cells play fundamental roles in cell-cell interactions, acting as local neuromodulators, neurohormones, as well as endocrine and paracrine messengers. Allatotropin (AT) is a neuropeptide originally described as a regulator of Juvenile Hormone synthesis, which plays multiple neural, endocrine and myoactive roles in insects and other organisms. METHODS: A combination of immunohistochemistry using AT-antibodies and AT-Qdot nanocrystal conjugates was used to identify immunoreactive nerve cells containing the peptide and epithelial-muscular cells targeted by AT in Hydra plagiodesmica. Physiological assays using AT and AT- antibodies revealed that while AT stimulated the extrusion of the hypostome in a dose-response fashion in starved hydroids, the activity of hypostome in hydroids challenged with food was blocked by treatments with different doses of AT-antibodies. CONCLUSIONS: AT antibodies immunolabeled nerve cells in the stalk, pedal disc, tentacles and hypostome. AT-Qdot conjugates recognized epithelial-muscular cell in the same tissues, suggesting the existence of anatomical and functional relationships between these two cell populations. Physiological assays indicated that the AT-like peptide is facilitating food ingestion. SIGNIFICANCE: Immunochemical, physiological and bioinformatics evidence advocates that AT is an ancestral neuropeptide involved in myoregulatory activities associated with meal ingestion and digestion.

Diferential DNA synthesis in Anopheles albimanus tissues induced by immune challenge with different microorganisms.

The induction of DNA synthesis in various tissues of Anopheles albimanus, in response to challenge with Saccharomyces cerevisiae, Micrococcus luteus, and Serratia marcescens, was analyzed by 5-bromo-2-deoxy-uridine (BrdU) incorporation. Microorganism-inoculated mosquitoes were fed with a sucrose solution containing BrdU and maintained alive for 5 days. Alternatively, abdominal carcasses of microorganisms-inoculated mosquitoes were cultivated in Roswell Park Memorial Institute (RPMI) medium supplemented with BrdU for 5 days. Control groups were inoculated with RPMI alone. In both experiments, DNA synthesis, evidenced by epifluorescence with an anti-BrdU fluorescein-labeled antibody, occurred in fat body, epithelial cells of pleural membranes, dorsal vessel, and the oviducts. Relative quantification of DNA synthesis, evaluated by ELISA using an anti-BrdU peroxidase-labeled antibody, was higher in abdomen tissues of microorganisms-inoculated mosquitoes than controls in in vitro and in vivo experiments. The intensity of DNA synthesis varied among the different microorganism challenges, but was higher in in vivo experiments, compared to cultured samples. These differences in DNA synthesis suggest a compartmentalization of the immune response, probably mediated by different signaling pathways.

Antimicrobial properties of Anopheles albimanus pericardial cells.

Insect pericardial cells (PCs) are strategically located along the dorsal vessel where they encounter a high hemolymph flow enabling them to undertake their osmoregulatory, detoxifying, and scavenging functions. In this location, PCs also encounter foreign molecules and microorganisms. The response of PCs of the mosquito Anopheles albimanus, one of the most important Plasmodium vivax vectors in Mexico and Latin America, to Saccharomyces cerevisiae was analyzed by using biochemical, cellular, ultrastructural, and bioinformatics approaches. Immune gene transcripts were identified in the PC transcriptome of A. albimanus. PCs responded to the presence of yeast and zymosan with increased lysosomal and phosphatase activities and produced lytic activity against bacteria. Our results indicate that mosquito PCs play a key role in the neutralization and elimination of pathogens.

Transcriptome of the adult female malaria mosquito vector Anopheles albimanus.

BACKGROUND: Human Malaria is transmitted by mosquitoes of the genus Anopheles. Transmission is a complex phenomenon involving biological and environmental factors of humans, parasites and mosquitoes. Among more than 500 anopheline species, only a few species from different branches of the mosquito evolutionary tree transmit malaria, suggesting that their vectorial capacity has evolved independently. Anopheles albimanus (subgenus Nyssorhynchus) is an important malaria vector in the Americas. The divergence time between Anopheles gambiae, the main malaria vector in Africa, and the Neotropical vectors has been estimated to be 100 My. To better understand the biological basis of malaria transmission and to develop novel and effective means of vector control, there is a need to explore the mosquito biology beyond the An. gambiae complex. RESULTS: We sequenced the transcriptome of the An. albimanus adult female. By combining Sanger, 454 and Illumina sequences from cDNA libraries derived from the midgut, cuticular fat body, dorsal vessel, salivary gland and whole body, we generated a single, high-quality assembly containing 16,669 transcripts, 92% of which mapped to the An. darlingi genome and covered 90% of the core eukaryotic genome. Bidirectional comparisons between the An. gambiae, An. darlingi and An. albimanus predicted proteomes allowed the identification of 3,772 putative orthologs. More than half of the transcripts had a match to proteins in other insect vectors and had an InterPro annotation. We identified several protein families that may be relevant to the study of Plasmodium-mosquito interaction. An open source transcript annotation browser called GDAV (Genome-Delinked Annotation Viewer) was developed to facilitate public access to the data generated by this and future transcriptome projects. CONCLUSIONS: We have explored the adult female transcriptome of one important New World malaria vector, An. albimanus. We identified protein-coding transcripts involved in biological processes that may be relevant to the Plasmodium lifecycle and can serve as the starting point for searching targets for novel control strategies. Our data increase the available genomic information regarding An. albimanus several hundred-fold, and will facilitate molecular research in medical entomology, evolutionary biology, genomics and proteomics of anopheline mosquito vectors. The data reported in this manuscript is accessible to the community via the VectorBase website (http://www.vectorbase.org/Other/AdditionalOrganisms/).