Mosquito Anopheles Albimanus Research Articles

Modeling Sustained Transmission of Wolbachia among Anopheles Mosquitoes: Implications for Malaria Control in Haiti.

Wolbachia infection in Anopheles albimanus mosquitoes can render mosquitoes less capable of spreading malaria. We developed and analyzed a mechanistic compartmental ordinary differential equation model to evaluate the effectiveness of Wolbachia-based vector control strategies among wild Anopheles mosquitoes in Haiti. The model tracks the mosquito life stages, including egg, larva, and adult (male and female). It also accounts for critical biological effects, such as the maternal transmission of Wolbachia through infected females and cytoplasmic incompatibility, which effectively sterilizes uninfected females when they mate with infected males. We derive and interpret dimensionless numbers, including the basic reproductive number and next-generation numbers. The proposed system presents a backward bifurcation, which indicates a threshold infection that needs to be exceeded to establish a stable Wolbachia infection. The sensitivity analysis ranks the relative importance of the epidemiological parameters at baseline. We simulate different intervention scenarios, including prerelease mitigation using larviciding and thermal fogging before the release, multiple releases of infected populations, and different release times of the year. Our simulations show that the most efficient approach to establishing Wolbachia is to release all the infected mosquitoes immediately after the prerelease mitigation process. Moreover, the model predicts that it is more efficient to release during the dry season than the wet season.

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.

Oral susceptibility to ivermectin is over fifty times greater in a wild population of Anopheles albimanus mosquitoes from Belize than the STECLA laboratory reference strain of this mosquito

BackgroundThe STECLA strain of Anopheles albimanus has been in continuous colony for many years and is the reference strain on which genomic studies for the species are based. Recently, the STECLA strain was demonstrated to be much less susceptible to ivermectin ingested in a blood meal (4-day LC50 of 1468 ng/ml) than all other Anopheles species tested to-date (LC50 values range from 7 to 56 ng/ml). The ability of An. albimanus to survive ingestion of ivermectin at concentrations far beyond that typically found in the blood of ivermectin-treated people or livestock (i.e., 30–70 ng/ml) could invalidate the use of ivermectin as a malaria vector control strategy in areas where An. albimanus is a primary vector.MethodsTo investigate this, host-seeking An. albimanus were captured in northern Belize and used in membrane feeding bioassays of ivermectin, employing the same methods as described earlier with the STECLA strain.ResultsField-collected An. albimanus in Belize were 55 times more susceptible to ingested ivermectin than were the STECLA reference strain. Oral susceptibility to ivermectin in wild An. albimanus from Belize (4-day LC50 of 26 ng/ml) was equivalent to that of other Anopheles species tested.ConclusionsContrary to initial assessments using a highly inbred strain of mosquito, laboratory studies using a field population indicate that ivermectin treatment of livestock could reduce An. albimanus populations in areas of Central America and the Caribbean where malaria transmission may occur. Toxicity screening of ivermectin and other systemic parasiticides for malaria control should examine wild populations of the vector species being targeted.

Malaria in Haiti: A descriptive study on spatial and temporal profile from 2009 to 2018.

ABSTRACTBackground: Haiti is one of the Caribbean countries where malaria persists. More than 99% of malaria cases are caused by Plasmodium falciparum, the main vector being the mosquito Anopheles albimanus. In this paper, we describe the epidemiological profile of malaria in Haiti between 2009 and 2018. Methods We analyzed information on cases reported by the Ministry of Health of Haiti and the World Health Organization (WHO). Results: Between 2009 and 2018, 232,479 malaria cases were reported by the Ministry of Public Health and Population (MSPP); an increase in the incidence of malaria in the country in 2010, followed by a decrease in 2011, was primarily observed. Due to recent efforts to reduce malaria by 2020, its incidence declined from 60,130 cases in 2010 to 8,978 cases in 2018. Controversially, in terms of the number of reported cases, the MSPP and WHO report conflicting data. However, the results from both datasets present the same trend in Haiti from 2009 to 2018. The results also illustrate the endemicity of the disease throughout Haiti, both in rural and urban areas, especially along the coast. Conclusions: This study emphasizes the need to promote official data collection and analyses, as well as the application of epidemiological surveillance of malaria at the municipal level, for a better understanding of the real impact of malaria on the Haitian population and to create more appropriate interventions.

Expression of Heat shock protein 70 (Hsp70-1) in Plasmodium berghei ookinetes and its participation in midgut mosquito infection

The heat shock protein family 70 (Hsp70) comprises chaperone proteins that play major multiple roles in Plasmodium asexual and sexual development. In this study, we analyzed the expression of Hsp70-1 in gametocytes, gametes, zygotes, and its participation in ookinete formation and their transition into oocysts. A monoclonal antibody against recombinant Hsp70-1 revealed its presence in zygotes and micronemes of ookinetes. Compared to wild type parasites, Hsp70-1 knockout ookinetes produced fewer oocysts in Plasmodium-susceptible Anopheles albimanus mosquitoes. This may indicate a defective transformation of ookinetes into oocysts in the absence of Hsp70-1. The presence of this protein in micronemes suggests its participation in mosquito infection, probably aiding to the adequate structural conformation of proteins in charge of motility, recognition and invasion of the insect midgut epithelium.

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.

Composition and structure of the culturable gut bacterial communities in Anopheles albimanus from Colombia.

The understanding of factors affecting the gut bacterial communities in malaria vectors is essential for the design of vector control interventions, such as those based on a paratransgenic approach. One of the requirements of this method is the availability of bacteria from the mosquito susceptible to culture. Thus, the aim of this study was to evaluate the composition and structure of the culturable gut bacterial communities in field mosquitoes Anopheles albimanus from Colombia, in addition to generate a bacterial collection to further analyze microbial functional activity. Gut bacteria were isolated from An. albimanus larvae and adult mosquitoes collected in localities of the Atlantic and Pacific Coasts. The bacterial isolates were grouped in 28 morphospecies that corresponded to three phyla, three classes, nine families and 14 genera. The larvae guts from San Antero (Atlantic Coast) and Buenaventura (Pacific Coast) shared the genera Bacillus and Lysinibacillus and in adults, Bacillus and Bacillus cereus Group were registered in both localities. Gut bacterial richness was higher in adults from the Pacific with respect to the Atlantic Coast, while larval richness was similar in samples of both coasts. The Shannon index indicated uniformity in morphospecies abundances in both localities. Finally, the characterization of morphospecies from the gut of Anopheles albimanus mosquitoes from Colombia by culture-dependent methods complemented with 16S rRNA gene sequencing allowed the definition, at a finer resolution, of the composition and structure of these microbial communities. In addition, the obtained bacterial culture collection will allow further evaluation of the microorganisms for their potential as biocontrol agents.

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.

Differential susceptibilities of Anopheles albimanus and Anopheles stephensi mosquitoes to ivermectin

BackgroundVector control is a crucial element of anti-malaria campaigns and works best when there is a thorough knowledge of the biology and behaviour of the Anopheles vector species responsible for transmitting malaria within a given locale. With the push to eradicate malaria stronger than ever, there is a growing need to develop and deploy control strategies that exploit the behavioural attributes of local vector species. This is especially true in regions where the vectors are exophagic (i.e., prefer to bite outdoors), exophilic (i.e., prefer to remain outdoors), and zoophagic (i.e., as likely to feed on non-humans as humans). One promising strategy targeting vectors with these behavioural traits is the administration of avermectin-based endectocides, such as ivermectin, to humans and livestock. When ingested in a blood meal, ivermectin has been shown to reduce mosquito survivorship and fecundity in a number of Anopheles species. In this study, the relative toxicity of ivermectin was compared between two zoophagic, exophilic malaria vectors—Anopheles albimanus and Anopheles stephensi.ResultsToxicity of ivermectin was assessed using membrane feedings, intrathoracic injections, and mosquito feedings on treated mice. When ingested in a blood meal, ivermectin was much less toxic to An. albimanus (4-day oral LC50 = 1468 ng/ml) than to An. stephensi (4-day oral LC50 = 7 ng/ml). However when injected into the haemocoel of An. albimanus, ivermectin was much more toxic (3-day parenteral LC50 = 188 ng/ml). Because the molecular targets of ivermectin (i.e., glutamate-gated chloride channels) reside outside the midgut in nerves and muscles, this suggests that ingested ivermectin was not readily absorbed across the midgut of An. albimanus. In contrast, ivermectin was considerably more toxic to An. stephensi when ingested (4-day oral LC50 = 7 ng/ml) than when injected (3-day parenteral LC50 = 49 ng/ml). This suggests that metabolic by-products from the digestion of ivermectin may play a role in the oral toxicity of ivermectin to An. stephensi. Blood meal digestion and subsequent oviposition rates were significantly hindered in both species by ingested ivermectin but only at concentrations at or above their respective oral LC50 concentrations. To test mosquitocidal activity of ivermectin in a live host system, two groups of three mice each received subcutaneous injections of either ivermectin (600 µg/kg BW) or saline (control). One day after injection, the ivermectin-treated mice (n = 3) exhibited significant mosquitocidal activity against both An. stephensi (85% mortality vs 0% in control-fed) and, to a lesser degree, An. albimanus (44% mortality vs 11% in control-fed). At 3 days, the mosquitocidal activity of ivermectin-treated mice waned and was effective only against An. stephensi (31% mortality vs 3% in control-fed).ConclusionsIvermectin was not uniformly toxic to both Anopheles species. Previous studies indicate that ivermectin is a good choice of endectocide to use against malaria vectors in southeast Asia and Africa. However, these data suggest that ivermectin may not be the optimal endectocide to use in Central America or the Caribbean where An. albimanus is a major malaria vector species. If endectocides are to be used to help eradicate malaria, then additional efficacy data will be needed to define the activity of specific endectocides against the major malaria vector species of the world.

Ecdysis-related pleiotropic neuropeptides expression during Anopheles albimanus development.

To analyze the transcription pattern of neuropeptides in the ontogeny of a malaria vector, the mosquito Anopheles albimanus. The transcription pattern of Crustacean CardioActive peptide (CCAP), corazonin, Ecdysis Triggering Hormone (ETH), allatostatin-A, orcokinin, Insulin Like Peptide 2 (ILP2), Insulin Like Peptide 5 (ILP5) and bursicon was evaluated using qPCR on larvae (1st - 4th instar), pupae and adult mosquitoes. Unlike in other insects, transcripts of CCAP (70.8%), ETH (60.2%) and corazonin (76.5%) were expressed in 4th instar larvae, probably because these three neuropeptides are associated with the beginning of ecdysis. The neuropeptide ILP2 showed higher transcription levels in other stages and orcokinin decreased during the development of the mosquito. The CCAP, corazonin and ETH neuropeptidesare potential targets for the design of control strategies aimed at disrupting An. albiamnus larval development.

Immune Regulation of Plasmodium Is Anopheles Species Specific and Infection Intensity Dependent.

ABSTRACTMalaria parasite ookinetes must traverse the vector mosquito midgut epithelium to transform into sporozoite-producing oocysts. The Anopheles innate immune system is a key regulator of this process, thereby determining vector competence and disease transmission. The role of Anopheles innate immunity factors as agonists or antagonists of malaria parasite infection has been previously determined using specific single Anopheles-Plasmodium species combinations. Here we show that the two C-type lectins CTL4 and CTLMA2 exert differential agonistic and antagonistic regulation of parasite killing in African and South American Anopheles species. The C-type lectins regulate both parasite melanization and lysis through independent mechanisms, and their implication in parasite melanization is dependent on infection intensity rather than mosquito-parasite species combination. We show that the leucine-rich repeat protein LRIM1 acts as an antagonist on the development of Plasmodium ookinetes and as a regulator of oocyst size and sporozoite production in the South American mosquito Anopheles albimanus. Our findings explain the rare observation of human Plasmodium falciparum melanization and define a key factor mediating the poor vector competence of Anopheles albimanus for Plasmodium berghei and Plasmodium falciparum.

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.

Recombinant Pvs48/45 antigen expressed in E. coli generates antibodies that block malaria transmission in Anopheles albimanus mosquitoes.

Transmission of malaria parasites from humans to Anopheles mosquitoes can be inhibited by specific antibodies elicited during malaria infection, which target surface Plasmodium gametocyte/gamete proteins. Some of these proteins may have potential for vaccine development. Pvs48/45 is a P. vivax gametocyte surface antigen orthologous to Pfs48/45, which may play a role during parasite fertilization and thus has potential for transmission blocking (TB) activity. Here we describe the expression of a recombinant Pvs48/45 protein expressed in Escherichia coli as a ∼60kDa construct which we tested for antigenicity using human sera and for its immunogenicity and transmission blocking activity of specific anti-mouse and anti-monkey Pvs48/45 antibodies. The protein reacted with sera of individuals from malaria-endemic areas and in addition induced specific IgG antibody responses in BALB/c mice and Aotus l. griseimembra monkeys. Sera from both immunized animal species recognized native P. vivax protein in Western blot (WB) and immunofluorescence assays. Moreover, sera from immunized mice and monkeys produced significant inhibition of parasite transmission to An. Albimanus mosquitoes as shown by membrane feeding assays. Results indicate the presence of reactive epitopes in the Pvs48/45 recombinant product that induce antibodies with TB activity. Further testing of this protein is ongoing to determine its vaccine potential.

Larvicidal activity of single and macrocyclic tyrosine derivatives against three important vector mosquitoes

The larvicidal activity of several phenylethylamines derived from l-tyrosine against larvae of the mosquito species Anopheles albimanus, Aedes aegypti, and Culex quinquefasciatus was studied. The results showed that the phenylethylamine nucleus present in different organic compounds with larvicidal activity has moderate larvicidal activity in itself, that the phenolic hydroxyl group is not decisive in larvicidal activity, that macrocyclic amino acids have activity comparable to or less than that observed for simple phenylethylamines, that the hydrocarbon chain on the carboxyl group affects the larvicidal activity, and that intermolecular interactions are crucial to the larvicidal activity of phenylethylamines, which is a new aspect to consider in the design of alternative, environmentally friendly insecticides for vector control with importance for public health. This paper presents a possible structure–larvicidal activity relationship for phenylethylamines with potential to guide the rational search for new nitrogen compounds useful for control of diseases borne by mosquito vectors.

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.

The Anopheles gambiae cE5, a tight- and fast-binding thrombin inhibitor with post-transcriptionally regulated salivary-restricted expression

Mosquito saliva carries a large number of factors with anti-hemostatic, anti-inflammatory and immuno-modulatory activities. The cE5 protein was initially identified during an Anopheles gambiae salivary gland transcriptome study and later shown to share sequence similarity with anophelin, a thrombin inhibitor from the saliva of the New World mosquito Anopheles albimanus. The cE5 gene was found to encode different mRNA isoforms coexisting in several tissues of both male and female mosquitoes, a highly unusual profile for a gene potentially encoding an anti-thrombin and involved in blood feeding. Expression of the cE5 protein and assessment of its activity and inhibitory properties showed that it is a highly specific and tight-binding thrombin inhibitor, which differs from the A. albimanus orthologue for the fast-binding kinetics. Despite the widespread occurrence of cE5 transcripts in different mosquito tissues the corresponding protein was only found in female salivary glands, where it undergoes post-translational modification. Therefore, tissue-specific restriction of the A. gambiae cE5 is not achieved by transcriptional control, as common for mosquito salivary genes involved in hematophagy, but by post-trascriptional gene regulatory mechanisms. Our observations provide a paradigm of post-transcriptional regulation as key determinant of tissue specificity for a protein from an important disease vector and point out that transcriptomic data should be interpreted with caution in the absence of concomitant proteomic support.

Determination of the resistance to organophosphate, carbamate, and pyrethroid insecticides in Panamanian Anopheles albimanus (Diptera: Culicidae) mosquitoes

The susceptibility of Anopheles albimanus to organophosphates, carbamates and pyrethroid insecticides was unknown in the Panama communities of Aguas Claras, Pintupo and Puente Bayano, located in the Amerindian Reservation of Madungandi. This region is considered a malaria transmission area, where An. albimanus is the main vector. The resistance to organophosphate insecticides, carbamates and pyrethroids was evaluated in field populations of the Anopheles albimanus in Panama. Progeny of An. albimanus collected in three localities in the indigenous Madugandi region were exposed to bioassays of susceptibility to organophosphate insecticides (fenitrothion, malathion and chlorpyrifos), the carbamate (propoxur) and pyrethroids (deltamethrin, lambdacyhalothrin, cyfluthrin and cypermethrin). The protocols were in accordance with those established for adult mosquitoes by World Health Organization. The three strains of the An. albimanus were resistant to the pyrethroid insecticides deltamethrin, lambdacyhalothrin, cyfluthrin and cypermethrin. Susceptibility remained for the organophosphate insecticides fenitrothion, malathion, chlorpyrifos, and the carbamate insecticide propoxur. The results provided important information to the vector control program, contributing to the application of new strategies on the use of insecticides, and thereby lengthening the life of the insecticide in use.

Plasmodium vivax Sporozoite Production in Anopheles albimanus Mosquitoes for Vaccine Clinical Trials

Vaccine development for Plasmodium vivax malaria is underway. A model to assess the protective efficacy of vaccine candidates in humans is urgently needed. Given the lack of continuous P. vivax cultures, we developed a system to infect Anopheles albimanus mosquitoes using blood from P. vivax-infected patients and determined parameters for challenge of malaria-naive volunteers by mosquito bite. Absence of co-infections in parasitized blood was confirmed by tests consistent with blood bank screening. A total of 119 experiments were conducted using batches of 900-4,500 mosquitoes fed by an artificial membrane feeding method. Optimal conditions for mosquito probing and infection were determined. Presence of oocyst and sporozoites were assessed on Days 7-8 and 14-15, respectively, and conditions to choose batches of infected mosquitoes for sporozoite challenge were established. Procedures to infect volunteers took a 2-hour period including verification of inoculum dose. Anopheles albimanus mosquitoes represent a valuable resource for P. vivax sporozoite challenge of volunteers.

Characterization of Plasmodium vivax Transmission-Blocking Activity in Low to Moderate Malaria Transmission Settings of the Colombian Pacific Coast

Malaria infection induces antibodies capable of suppressing the infectivity of gametocytes and gametes, however, little is known about the duration of the antibody response, the parasite specificity, and the role of complement. We report the analyses of the transmission-blocking (TB) activity of sera collected from 105 Plasmodium vivax-infected and 44 non-infected individuals from a malaria endemic region of Colombia, using a membrane feeding assay in Anopheles albimanus mosquitoes. In infected donors we found that TB activity was antibody dose dependent (35%), lasted for 2-4 months after infection, and in 70% of the cases different P. vivax wild isolates displayed differential susceptibility to blocking antibodies. Additionally, in a number of assays TB was complement-dependent. Twenty-seven percent of non-infected individuals presented TB activity that correlated with antibody titers. Studies here provide preliminary data on factors of great importance for further work on the development of TB vaccines.