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Vallejo A.F.,Malaria Vaccine and Drug Development Center | Rubiano K.,Caucaseco Scientific Research Center | Amado A.,Caucaseco Scientific Research Center | Krystosik A.R.,Kent State University | And 2 more authors.
PLoS Neglected Tropical Diseases | Year: 2016

Introduction: Individuals exposed to malaria infections for a long time develop immune responses capable of blocking Plasmodium transmission to mosquito vectors, potentially limiting parasite spreading in nature. Development of a malaria TB vaccine requires a better understanding of the mechanisms and main effectors responsible for transmission blocking (TB) responses. The lack of an in vitro culture system for Plasmodium vivax has been an important drawback for development of a standardized method to assess TB responses to this parasite. This study evaluated host, vector, and parasite factors that may influence Anopheles mosquito infection in order to develop an efficient and reliable assay to assess the TB immunity. Methods/Principal Findings: A total of 94 P. vivax infected patients were enrolled as parasite donors or subjects of direct mosquito feeding in two malaria endemic regions of Colombia (Tierralta, and Buenaventura). Parasite infectiousness was assessed by membrane feeding assay or direct feeding assay using laboratory reared Anopheles mosquitoes. Infection was measured by qPCR and by microscopically examining mosquito midguts at day 7 for the presence of oocysts. Best infectivity was attained in four day old mosquitoes fed at a density of 100 mosquitos/cage. Membrane feeding assays produced statistically significant better infections than direct feeding assays in parasite donors; cytokine profiles showed increased IFN-γ, TNF and IL-1 levels in non-infectious individuals. Mosquito infections and parasite maturation were more reliably assessed by PCR compared to microscopy. Conclusions: We evaluated mosquito, parasite and host factors that may affect the outcome of parasite transmission as measured by artificial membrane feeding assays. Results have led us to conclude that: 1) optimal mosquito infectivity occurs with mosquitoes four days after emergence at a cage density of 100; 2) mosquito infectivity is best quantified by PCR as it may be underestimated by microscopy; 3) host cellular immune response did not appear to significantly affect mosquito infectivity; and 4) no statistically significant difference was observed in transmission between mosquitoes directly feeding on humans and artificial membrane feeding assays. © 2016 Vallejo et al.

Teixeira L.H.,Federal University of Sao Paulo | Tararam C.A.,Federal University of Sao Paulo | Lasaro M.O.,Wistar Institute | Lasaro M.O.,Boehringer Ingelheim | And 10 more authors.
Infection and Immunity | Year: 2014

Plasmodium vivax is the most widespread and the second most prevalent malaria-causing species in the world. Current measures used to control the transmission of this disease would benefit from the development of an efficacious vaccine.In the case of the deadly parasite P. falciparum, the recombinant RTS,S vaccine containing the circumsporozoite antigen (CSP) consistently protects 30 to 50% of human volunteers against infection and is undergoing phase III clinical trials in Africa with similar efficacy. These findings encouraged us to develop a P. vivax vaccine containing the three circulating allelic forms of P. vivax CSP. Toward this goal, we generated three recombinant bacterial proteins representing the CSP alleles, as well as a hybrid polypeptide called PvCSP-All-CSP-epitopes. This hybrid contains the conserved N and C termini of P. vivax CSP and the three variant repeat domains in tandem. We also generated simian and human recombinant replication-defective adenovirus vectors expressing PvCSP-All-CSP-epitopes. Mice immunized with the mixture of recombinantproteins in a formulation containing the adjuvant poly(I.C) developed high and long-lasting serum IgG titers comparable to those elicited by proteins emulsified in complete Freund's adjuvant. Antibody titers were similar in mice immunized with homologous (protein-protein) and heterologous (adenovirus-protein) vaccine regimens. The antibodies recognized the three allelic forms of CSP, reacted to the repeated and nonrepeated regions of CSP, and recognized sporozoites expressing the alleles VK210 and VK247. The vaccine formulations described in this work should be useful for the further development of an anti-P. vivax vaccine. © 2014, American Society for Microbiology.

Herrera S.,University of Valle | Herrera S.,Malaria Vaccine and Drug Development Center | Solarte Y.,University of Valle | Jordan-Villegas A.,University of Valle | And 8 more authors.
American Journal of Tropical Medicine and Hygiene | Year: 2011

A safe and reproducible Plasmodium vivax infectious challenge method is required to evaluate the efficacy of malaria vaccine candidates. Seventeen healthy Duffy (+) and five Duffy (-) subjects were randomly allocated into three (A-C) groups and were exposed to the bites of 2-4 Anopheles albimanus mosquitoes infected with Plasmodium vivax derived from three donors. Duffy (-) subjects were included as controls for each group. Clinical manifestations of malaria and parasitemia were monitored beginning 7 days post-challenge. All Duffy (+) volunteers developed patent malaria infection within 16 days after challenge. Prepatent period determined by thick smear, was longer for Group A (median 14.5 d) than for Groups B and C (median 10 d/each). Infected volunteers recovered rapidly after treatment with no serious adverse events. The bite of as low as two P. vivax -infected mosquitoes provides safe and reliable infections in malaria-naive volunteers, suitable for assessing antimalarial and vaccine efficacy trials. Copyright © 2011 by The American Society of Tropical Medicine and Hygiene.

Vallejo A.F.,Malaria Vaccine and Drug Development Center | Chaparro P.E.,National Institute of Health of Colombia | Benavides Y.,Caucaseco Scientific Research Center | Alvarez A.,Caucaseco Scientific Research Center | And 7 more authors.
Malaria Journal | Year: 2015

Background: Malaria transmission in Latin America is typically characterized as hypo-endemic and unstable with ∼170 million inhabitants at risk of malaria infection. Although Colombia has witnessed an important decrease in malaria transmission, the disease remains a public health problem with an estimated ∼10 million people currently living in areas with malaria risk and ∼61,000 cases reported in 2012. This study aimed to establish the malaria prevalence in three endemic regions of Colombia to aid in designing new interventions for malaria elimination. Methods: A cross-sectional survey was conducted in three regions of Colombia with different malaria epidemiological profiles: Tierralta (Ta), Tumaco (Tu) and Buenaventura (Bv). The Annual Parasite Index (API) was 10.7, 6.9 and 3.1, respectively. Participants were asked to respond to a sociodemographic questionnaire and then were bled to determine the Duffy genotype and the prevalence of malaria infection by microscopy and quantitative real-time PCR (qPCR). Results: The study was conducted between October 2011 and January 2012. Eight sentinel sites with 1,169 subjects from 267 households were included. The overall prevalence of sub-microscopic infections measured by thick blood smear (TBS) was 0.3% (n = 4) whereas by qPCR it was 9.7% (n = 113), with a greater proportion (13%) in 40-50 years old individuals. Furthermore, different regions displayed different prevalence of sub-microscopic infections: Bv 12%, Ta 15%, and Tu 4%. From these 113 samples (qPCR), 74% were positive for P. vivax and 22% for P. falciparum, and 4% were mixed infections, which correlates to the overall parasite prevalence in Colombia. This study showed that in the southern Pacific coast of Colombia (Bv and Tu), around 56% of the population have a Duffy-negative genotype, compared to the northern region (Ta) where the percentage of Duffy-negative genotype is around 3%. Conclusions: Sub-microscopic infections are prevalent across different regions in Colombia, particularly in areas with relatively low transmission intensity. The poor microscopy results suggest the need for more sensitive diagnostic tools for detection of sub-microscopic infections. This study underscores the importance of conducting active case surveillance to more accurately determine malaria incidence, and highlights the need for updating the malaria guidelines to track and treat sub-microscopic malaria infections. © 2015 Vallejo et al.; licensee BioMed Central.

Herrera S.,Caucaseco Scientific Research Center | Herrera S.,Malaria Vaccine and Drug Development Center | Ochoa-Orozco S.A.,Caucaseco Scientific Research Center | Ochoa-Orozco S.A.,Malaria Vaccine and Drug Development Center | And 5 more authors.
PLoS Neglected Tropical Diseases | Year: 2015

Malaria remains endemic in 21 countries of the American continent with an estimated 427,000 cases per year. Approximately 10% of these occur in the Mesoamerican and Caribbean regions. During the last decade, malaria transmission in Mesoamerica showed a decrease of ~85%; whereas, in the Caribbean region, Hispaniola (comprising the Dominican Republic [DR] and Haiti) presented an overall rise in malaria transmission, primarily due to a steady increase in Haiti, while DR experienced a significant transmission decrease in this period. The significant malaria reduction observed recently in the region prompted the launch of an initiative for Malaria Elimination in Mesoamerica and Hispaniola (EMMIE) with the active involvement of the National Malaria Control Programs (NMCPs) of nine countries, the Regional Coordination Mechanism (RCM) for Mesoamerica, and the Council of Health Ministries of Central America and Dominican Republic (COMISCA). The EMMIE initiative is supported by the Global Fund for Aids, Tuberculosis and Malaria (GFATM) with active participation of multiple partners including Ministries of Health, bilateral and multilateral agencies, as well as research centers. EMMIE’s main goal is to achieve elimination of malaria transmission in the region by 2020. Here we discuss the prospects, challenges, and research needs associated with this initiative that, if successful, could represent a paradigm for other malaria-affected regions. © 2015 Herrera et al.

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