In malaria parasites, the erythrocyte binding-like proteins (EBL) are a family of invasion proteins that are attractive vaccine targets. In the case of Plasmodium vivax, the widespread malaria ...parasite, blood-stage vaccines have been largely focused on a single EBL candidate, the Duffy binding-like domain (DBL) of the Duffy binding protein (DBPII), due to its well-characterized role in the reticulocyte invasion. A novel P. vivax EBL family member, the Erythrocyte binding protein (EBP2, also named EBP or DBP2), binds preferentially to reticulocytes and may mediate an alternative P. vivax invasion pathway. To gain insight into the natural genetic diversity of the DBL domain of EBP2 (region II; EBP2-II), we analyzed ebp2-II gene sequences of 71 P. vivax isolates collected in different endemic settings of the Brazilian Amazon rainforest, where P. vivax is the predominant malaria-associated species. Although most of the substitutions in the ebp2-II gene were non-synonymous and suggested positive selection, the results showed that the DBL domain of the EBP2 was much less polymorphic than that of DBPII. The predominant EBP2 haplotype in the Amazon region corresponded to the C127 reference sequence first described in Cambodia (25% C127-like haplotype). An overview of ebp2-II gene sequences available at GenBank (n = 352) from seven countries (Cambodia, Madagascar, Myanmar, PNG, South Korea, Thailand, Vietnam) confirmed the C127-like haplotype as highly prevalent worldwide. Two out of 43 haplotypes (5 to 20 inferred per country) showed a global frequency of 60%. The results presented here open new avenues of research pursuit while suggesting that a vaccine based on the DBL domain of EBP2 should target a few haplotypes for broad coverage.
•The ebp2-II gene was less diverse than dbpII gene in parasites from the Amazon.•Natural selection analysis suggested that ebp2-II gene underwent positive selection•A 3D predicted structure of EBP2-II showed most of the nsSNPs as exposed on its surface.•The worldwide ebp2-II variability indicated C127-like haplotype as highly prevalent.
Plasmodium vivax blood-stage invasion into reticulocyte is critical for parasite development. Thus, validation of novel parasite invasion ligands is essential for malaria vaccine development. ...Recently, we demonstrated that EBP2, a Duffy binding protein (DBP) paralog, is antigenically distinct from DBP and could not be functionally inhibited by anti-DBP antibodies. Here, we took advantage of a small outbreak of P.vivax malaria, located in a non-malarious area of Brazil, to investigate for the first time IgM/IgG antibodies against EBP2 and DEKnull-2 (an engineering DBPII vaccine) among individuals who had their first and brief exposure to P.vivax (16 cases and 22 non-cases). Our experimental approach included 4 cross sectional surveys at 3-month interval (12-month follow-up). The results demonstrated that while a brief initial P.vivax infection was not efficient to induce IgM/ IgG antibodies to either EBP2 or DEKnull-2, IgG antibodies against DEKnull-2 (but not EBP2) were boosted by recurrent blood-stage infections following treatment. Of interest, in most recurrent P. vivax infections (4 out of 6 patients) DEKnull-2 IgG antibodies were sustained for 6 to 12 months. Polymorphisms in the ebp2 gene does not seem to explain EBP2 low immunogenicity as the ebp2 allele associated with the P.vivax outbreak presented high identity to the original EBP2 isolate used as recombinant protein. Although EBP2 antibodies were barely detectable after a primary episode of P.vivax infection, EBP2 was highly recognized by serum IgG from long-term malaria-exposed Amazonians (range from 35 to 92% according to previous malaria episodes). Taken together, the results showed that individuals with a single and brief exposure to P.vivax infection develop very low anti-EBP2 antibodies, which tend to increase after long-term malaria exposure. Finally, the findings highlighted the potential of DEKnull-2 as a vaccine candidate, as in non-immune individuals anti-DEKnull-2 IgG antibodies were boosted even after a brief exposure to P.vivax blood stages.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Plasmodium vivax blood-stage invasion into reticulocyte is critical for parasite development. Thus, validation of novel parasite invasion ligands is essential for malaria vaccine development. ...Recently, we demonstrated that EBP2, a Duffy binding protein (DBP) paralog, is antigenically distinct from DBP and could not be functionally inhibited by anti-DBP antibodies. Here, we took advantage of a small outbreak of P.vivax malaria, located in a non-malarious area of Brazil, to investigate for the first time IgM/IgG antibodies against EBP2 and DEKnull-2 (an engineering DBPII vaccine) among individuals who had their first and brief exposure to P.vivax (16 cases and 22 non-cases). Our experimental approach included 4 cross sectional surveys at 3-month interval (12-month follow-up). The results demonstrated that while a brief initial P.vivax infection was not efficient to induce IgM/ IgG antibodies to either EBP2 or DEKnull-2, IgG antibodies against DEKnull-2 (but not EBP2) were boosted by recurrent blood-stage infections following treatment. Of interest, in most recurrent P. vivax infections (4 out of 6 patients) DEKnull-2 IgG antibodies were sustained for 6 to 12 months. Polymorphisms in the ebp2 gene does not seem to explain EBP2 low immunogenicity as the ebp2 allele associated with the P.vivax outbreak presented high identity to the original EBP2 isolate used as recombinant protein. Although EBP2 antibodies were barely detectable after a primary episode of P.vivax infection, EBP2 was highly recognized by serum IgG from long-term malaria-exposed Amazonians (range from 35 to 92% according to previous malaria episodes). Taken together, the results showed that individuals with a single and brief exposure to P.vivax infection develop very low anti-EBP2 antibodies, which tend to increase after long-term malaria exposure. Finally, the findings highlighted the potential of DEKnull-2 as a vaccine candidate, as in non-immune individuals anti-DEKnull-2 IgG antibodies were boosted even after a brief exposure to P.vivax blood stages. Author summary Vaccines might be a crucial component of the current efforts to malaria control and elimination, and much of the vaccine-related research on P. vivax has been focused on region II of the Duffy binding protein (DBPII), a ligand for human blood-stage infection. Recently, the newly described Erythrocyte binding protein 2 (EBP2), a P.vivax DBP paralog that it is antigenically distinct from DBP, was identified as potential vaccine targets. To date, scarce data are available about the naturally acquired immunity to EBP2. In a small outbreak of P.vivax malaria, located in a non-malarious area, we investigated whether a first P.vivax exposure induces antibodies against EBP2 that could be boosted by P.vivax recurrent infections. In parallel, we included an engineered DBPII vaccine (named DEKnull-2) whose antibody response were previously associated with broadly neutralizing P.vivax antibodies. This study shows EBP2, compared with DEKnull-2, was poorly immunogenic among individuals who experienced their first blood-stage P. vivax malaria infection. However, EBP2 was highly immunogenic in long-term malaria exposed individuals, reinforcing its potential as a P. vivax blood-stage vaccine candidate. Finally, our results reinforce that multiple blood-stage antigens should be targeted for the development of efficient vaccines against P. vivax.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Plasmodium vivax Duffy binding protein (PvDBP) and its erythrocytic receptor, the Duffy antigen receptor for chemokines (DARC), are involved in the major P. vivax erythrocyte invasion pathway. An ...open cohort study to analyze DARC genotypes and their relationship to PvDBP immune responses was carried out in 620 volunteers in an agricultural settlement of the Brazilian Amazon. Three cross-sectional surveys were conducted at 6-month intervals, comprising 395, 410, and 407 subjects, respectively. The incidence rates of P. vivax infection was 2.32 malaria episodes per 100 personmonths under survey (95% confidence interval CI of 1.92-2.80/100 person-month) and, of P. falciparum, 0.04 per 100 person-months (95% CI of 0.007-0.14/100 person-month). The distribution of DARC genotypes was consistent with the heterogeneous ethnic origins of the Amazon population, with a predominance of non-silent DARC alleles: FY*A > FY*B. The 12-month follow-up study demonstrated no association between DARC genotypes and total IgG antibodies as measured by ELISA targeting PvDBP (region II, DBPII or regions II-IV, DBPII-IV). The naturally acquired DBPII specific binding inhibitory antibodies (BIAbs) tended to be more frequent in heterozygous individuals carrying a DARC-silent allele (FY*B.sup.ES). These results provide evidence that DARC polymorphisms may influence the naturally acquired inhibitory anti-Duffy binding protein II immunity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Plasmodium vivax Duffy binding protein (PvDBP) and its erythrocytic receptor, the Duffy antigen receptor for chemokines (DARC), are involved in the major P. vivax erythrocyte invasion pathway. An ...open cohort study to analyze DARC genotypes and their relationship to PvDBP immune responses was carried out in 620 volunteers in an agricultural settlement of the Brazilian Amazon. Three cross-sectional surveys were conducted at 6-month intervals, comprising 395, 410, and 407 subjects, respectively. The incidence rates of P. vivax infection was 2.32 malaria episodes per 100 personmonths under survey (95% confidence interval CI of 1.92-2.80/100 person-month) and, of P. falciparum, 0.04 per 100 person-months (95% CI of 0.007-0.14/100 person-month). The distribution of DARC genotypes was consistent with the heterogeneous ethnic origins of the Amazon population, with a predominance of non-silent DARC alleles: FY*A > FY*B. The 12-month follow-up study demonstrated no association between DARC genotypes and total IgG antibodies as measured by ELISA targeting PvDBP (region II, DBPII or regions II-IV, DBPII-IV). The naturally acquired DBPII specific binding inhibitory antibodies (BIAbs) tended to be more frequent in heterozygous individuals carrying a DARC-silent allele (FY*B.sup.ES). These results provide evidence that DARC polymorphisms may influence the naturally acquired inhibitory anti-Duffy binding protein II immunity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Objective: To investigate risk factors associated with the acquisition of antibodies against Plasmodium vivax Duffy binding protein (PvDBP) - a leading malaria vaccine candidate - in a ...well-consolidated agricultural settlement of the Brazilian Amazon Region and to determine the sequence diversity of the PvDBP ligand domain (DBPII) within the local malaria parasite population. Methods: Demographic, epidemiological and clinical data were collected from 541 volunteers using a structured questionnaire. Malaria parasites were detected by conventional microscopy and PCR, and blood collection was used for antibody assays and molecular characterization of DBPII. Results: The frequency of malaria infection was 7% (6% for P. vivax and 1% for P. falciparum), with malaria cases clustered near mosquito breeding sites. Nearly 50% of settlers had anti-PvDBP IgG antibodies, as detected by enzyme-linked immunosorbent assay (ELISA) with subject's age being the only strong predictor of seropositivity to PvDBP. Unexpectedly, low levels of DBPII diversity were found within the local malaria parasites, suggesting the existence of low gene flow between P. vivax populations, probably due to the relative isolation of the studied settlement. Conclusion: The recognition of PvDBP by a significant proportion of the community, associated with low levels of DBPII diversity among local P. vivax, reinforces the variety of malaria transmission patterns in communities from frontier settlements. Such studies should provide baseline information for antimalarial vaccines now in development.PUBLICATION ABSTRACT
Objective To investigate risk factors associated with the acquisition of antibodies against Plasmodium vivax Duffy binding protein (PvDBP) - a leading malaria vaccine candidate - in a ...well-consolidated agricultural settlement of the Brazilian Amazon Region and to determine the sequence diversity of the PvDBP ligand domain (DBPII) within the local malaria parasite population. Methods Demographic, epidemiological and clinical data were collected from 541 volunteers using a structured questionnaire. Malaria parasites were detected by conventional microscopy and PCR, and blood collection was used for antibody assays and molecular characterisation of DBPII. Results The frequency of malaria infection was 7% (6% for P. vivax and 1% for P. falciparum), with malaria cases clustered near mosquito breeding sites. Nearly 50% of settlers had anti-PvDBP IgG antibodies, as detected by enzyme-linked immunosorbent assay (ELISA) with subject's age being the only strong predictor of seropositivity to PvDBP. Unexpectedly, low levels of DBPII diversity were found within the local malaria parasites, suggesting the existence of low gene flow between P. vivax populations, probably due to the relative isolation of the studied settlement. Conclusion The recognition of PvDBP by a significant proportion of the community, associated with low levels of DBPII diversity among local P. vivax, reinforces the variety of malaria transmission patterns in communities from frontier settlements. Such studies should provide baseline information for antimalarial vaccines now in development.Original Abstract: Objectif: Investiguer les facteurs de risque associes a l'acquisition d'anticorps contre la proteine de liaison Duffy de Plasmodium vivax (PvDBP) - un candidat vaccin de premiere ligne contre le paludisme - dans une zone d'habitation agricole bien consolidee de la region amazonienne du Bresil, et determiner la diversite des sequences du domaine ligand PvDBP (DBPII) au sein de la population locale du parasite du paludisme. Methodes: Les donnees demographiques, epidemiologiques et cliniques ont ete recueillies a partir de 541 volontaires a l'aide d'un questionnaire structure. Les parasites du paludisme ont ete detectes par la microscopie conventionnelle et la PCR, et la collecte de sang a ete utilisee pour les essais d'anticorps et la caracterisation moleculaire du DBPII. Resultats: La frequence de l'infection palustre etait de 7% (6% pour P. vivax et 1% pour P. falciparum), avec des cas de paludisme regroupes a proximite des sites de reproduction des moustiques. Pres de 50% des residents avaient des anticorps IgG anti-PvDBP, tels que detectes par le test ELISA, avec l'age du sujet etant le seul facteur predictif fort de la seropositivitea PvDBP. De facon inattendue, de faibles niveaux de diversite DBPII ont ete trouves parmi les parasites locaux du paludisme, ce qui suggere l'existence de peu de flux de genes entre les populations de P. vivax, probablement en raison de l'isolement relatif de la zone etudiee. Conclusion: La reconnaissance de PvDBP par une proportion significative de la communaute, associee a de faibles niveaux de diversite DBPII parmi les moustiques P. vivax locaux, renforce la variete des modes de transmission du paludisme dans les communautes etablies dans des zones frontalieres. Ces etudes devraient fournir des informations de base pour les vaccins antipaludiques en cours de developpement. Objetivo: Investigar los factores de riesgo asociados con la adquisicion de anticuerpos frente a la proteina de union al Duffy de Plasmodium vivax (PvDBP) - uno de los principales candidatos a vacuna de malaria - en un asentamiento agricola bien consolidado de la region Amazonica del Brasil; y determinar la diversidad en la secuencia del dominio del ligando de PvDBP (DBPII) dentro de la poblacion local de parasitos de malaria. Metodos: Se recolectaron datos demograficos, epidemiologicos y clinicos de 541 voluntarios utilizando un cuestionario estructurado. Los parasitos de malaria se detectaron mediante microscopia convencional y PCR, y se utilizaron muestras de sangre para realizar pruebas de anticuerpos y la caracterizacion molecular de DBPII. Resultados: La frecuencia de infeccion de malaria era del 7% (6% para P. vivax y 1% para P. falciparum), con los casos de malaria agrupados cerca de lugares de cria de mosquitos. Casi un 50% de los pobladores tenian anticuerpos IgG anti-PvDBP, detectados mediante un ensayo por inmunoabsorcion ligado a enzimas (ELISA), siendo la edad del sujeto el unico vaticinador importante de seropositividad frente a PvDBP. Sorprendentemente, se hallo un bajo nivel de diversidad de DBPII dentro de la poblacion local de parasitos de malaria, sugiriendo la existencia de un flujo genetico bajo entre las poblaciones de P. vivax, probablemente debido al aislamiento relativo del emplazamiento estudiado. Conclusion: El reconocimiento de PvDBP en una proporcion significativa de la comunidad, asociada a unos bajos niveles de diversidad del DBPII entre la poblacion local de P. vivax, refuerza la variedad de patrones de trasmision de malaria en comunidades viviendo en emplazamientos fronterizos. Algunos estudios deberian aportar la informacion de base para vacunas antimalaricas ahora en desarrollo.
The Plasmodium vivax Duffy binding protein (PvDBP) and its erythrocytic receptor, the Duffy antigen receptor for chemokines (DARC), are involved in the major P. vivax erythrocyte invasion pathway. An ...open cohort study to analyze DARC genotypes and their relationship to PvDBP immune responses was carried out in 620 volunteers in an agricultural settlement of the Brazilian Amazon. Three cross-sectional surveys were conducted at 6-month intervals, comprising 395, 410, and 407 subjects, respectively. The incidence rates of P. vivax infection was 2.32 malaria episodes per 100 person-months under survey (95% confidence interval CI of 1.92-2.80/100 person-month) and, of P. falciparum, 0.04 per 100 person-months (95% CI of 0.007-0.14/100 person-month). The distribution of DARC genotypes was consistent with the heterogeneous ethnic origins of the Amazon population, with a predominance of non-silent DARC alleles: FY*A > FY*B. The 12-month follow-up study demonstrated no association between DARC genotypes and total IgG antibodies as measured by ELISA targeting PvDBP (region II, DBPII or regions II-IV, DBPII-IV). The naturally acquired DBPII specific binding inhibitory antibodies (BIAbs) tended to be more frequent in heterozygous individuals carrying a DARC-silent allele (FY*BES). These results provide evidence that DARC polymorphisms may influence the naturally acquired inhibitory anti-Duffy binding protein II immunity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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