RESUMO
An important step when designing a vaccine is identifying the antigens that function as targets of naturally acquired antibodies. We investigated specific antibody responses against two Plasmodium vivax vaccine candidates, PvMSP-119 and PvMSP-3α359â798. Moreover, we assessed the relationship between these antibodies and morbidity parameters. PvMSP-119 was the most immunogenic antigen and the frequency of responders to this protein tended to increase in P. vivax patients with higher parasitemia. For both antigens, IgG antibody responses tended to be lower in patients who had experienced their first bout of malaria. Furthermore, anemic patients presented higher IgG antibody responses to PvMSP-3α359â798. Since the humoral response involves a number of antibodies acting simultaneously on different targets, we performed a Principal Component Analysis (PCA). Anemic patients had, on average, higher first principal component scores (IgG1/IgG2/IgG3/IgG4 anti-MSP3α), which were negatively correlated with hemoglobin levels. Since antibodies against PfMSP-3 have been strongly associated with clinical protection, we cannot exclude the possibility of a dual role of PvMSP-3 specific antibodies in both immunity and pathogenesis of vivax malaria. Our results confirm the high immunogenicity of the conserved C terminus of PvMSP-1 and points to the considerable immunogenicity of polymorphic PvMSP-3α359â798 during natural infection.
Assuntos
Anticorpos Antiprotozoários/sangue , Antígenos de Protozoários/imunologia , Vacinas Antimaláricas/imunologia , Malária Vivax/imunologia , Proteína 1 de Superfície de Merozoito/imunologia , Plasmodium vivax/imunologia , Proteínas de Protozoários/imunologia , Adolescente , Adulto , Idoso , Brasil , Criança , Feminino , Humanos , Imunoglobulina G/sangue , Vacinas Antimaláricas/administração & dosagem , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Plasmodium vivax Merozoite Surface Protein-3alpha and 3beta are members of a family of related merozoite surface proteins that contain a central alanine-rich domain with heptad repeats that is predicted to form alpha-helical secondary and coiled-coil tertiary structures. Seven recombinant proteins representing different regions of MSP-3alpha and MSP-3beta of P. vivax were generated to investigate their structure. Circular dichroism spectra analysis revealed that some proteins are folded with a high degree of alpha-helices as secondary structure, whereas other products contain a high content of random coil. Using size exclusion chromatography, we found that the two smaller fragments of the MSP-3alpha, named CC4 and CC5, predicted to form coiled-coil (CC) structures, eluted at volumes corresponding to molecular weights larger than their monomeric masses. This result suggests that both proteins are oligomeric molecules. Analytical ultracentrifugation experiments showed that the CC5 oligomers are elongated molecules. Together, these data may help to understand important aspects of P. vivax biology.
Assuntos
Antígenos de Protozoários/química , Biofísica/métodos , Plasmodium vivax/química , Proteínas de Protozoários/química , Alanina/química , Animais , Antígenos de Protozoários/genética , Antígenos de Protozoários/imunologia , Antígenos de Protozoários/metabolismo , Dicroísmo Circular , Plasmídeos , Plasmodium vivax/genética , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Proteínas de Protozoários/genética , Proteínas de Protozoários/imunologia , Proteínas de Protozoários/metabolismo , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/isolamento & purificação , Proteínas Recombinantes de Fusão/metabolismoRESUMO
Diversas proteínas de superfície de merozoítas (MSPs) de Plasmodium têm sido consideradas a compor uma vacina contra a malária. Nos últimos anos estudamos diversos aspectos da reposta imune naturalmente adquirida contra proteínas recombinantes baseadas nas MSPs de P. vivax. Estes estudos demonstram que estas proteínas recombinantes mantêm suas funções imunológicas, podendo servir como base para a caracterização de suas estruturas tridimensionais. Com o objetivo de obter informações estruturais sobre as MSPs de P. vivax, 10 proteínas recombinantes, correspondentes à região C-terminal da MSP-1 (MSP119), e diferentes regiões da MSP-3α e MSP-3β foram expressas em Escherichia coli. Os dados estruturais da MSP119 foram obtidos por modelagem molecular com base nas coordenadas cristalográficas da MSP19 de P. cynomolgi. Por outro lado existem poucas informações estruturais sobre as proteínas da família MSP-3 de Plasmodium. A análise da estrutura primária dessas proteínas indica que elas apresentam um domínio central rico em alaninas que estão organizadas como motivos heptads...
Assuntos
Proteína 1 de Superfície de Merozoito , Malária/imunologia , Plasmodium vivax , Proteínas Recombinantes , Cromatografia em Gel/métodos , Dicroísmo Circular/métodos , Espectrometria de Massas/métodos , Biologia MolecularRESUMO
In previous immuno-epidemiological studies of the naturally acquired antibody responses to merozoite surface protein-1 (MSP-1) of Plasmodium vivax, we had evidence that the responses to distinct erythrocytic stage antigens could be differentially regulated. The present study was designed to compare the antibody response to three asexual erythrocytic stage antigens vaccine candidates of P. vivax. Recombinant proteins representing the 19 kDa C-terminal region of MSP-1(PvMSP19), apical membrane antigen n-1 ectodomain (PvAMA-1), and the region II of duffy binding protein (PvDBP-RII) were compared in their ability to bind to IgG antibodies of serum samples collected from 220 individuals from the state of Pará, in the North of Brazil. During patent infection with P. vivax, the frequency of individuals with IgG antibodies to PvMSP1(19), PvAMA-1, and PvDBP-RII were 95, 72.7, and 44.5% respectively. Although the frequency of responders to PvDBP-RII was lower, this frequency increased in individuals following multiple malarial infections. Individually, the specific antibody levels did not decline significantly nine months after treatment, except to PvMSP1(19). Our results further confirm a complex regulation of the immune response to distinct blood stage antigens. The reason for that is presently unknown but it may contribute to the high risk of re-infection in individuals living in the endemic areas.
Assuntos
Anticorpos Antiprotozoários/imunologia , Imunoglobulina G/imunologia , Vacinas Antimaláricas/imunologia , Malária Vivax/imunologia , Proteína 1 de Superfície de Merozoito/imunologia , Plasmodium vivax/imunologia , Animais , Ensaio de Imunoadsorção Enzimática , Humanos , Proteína 1 de Superfície de Merozoito/química , Proteínas Recombinantes/imunologiaRESUMO
In previous immuno-epidemiological studies of the naturally acquired antibody responses to merozoite surface protein-1 (MSP-1) of Plasmodium vivax, we had evidence that the responses to distinct erythrocytic stage antigens could be differentially regulated. The present study was designed to compare the antibody response to three asexual erythrocytic stage antigens vaccine candidates of P. vivax. Recombinant proteins representing the 19 kDa C-terminal region of MSP-1(PvMSP19), apical membrane antigen n-1 ectodomain (PvAMA-1), and the region II of duffy binding protein (PvDBP-RII) were compared in their ability to bind to IgG antibodies of serum samples collected from 220 individuals from the state of Pará, in the North of Brazil. During patent infection with P. vivax, the frequency of individuals with IgG antibodies to PvMSP1(19), PvAMA-1, and PvDBP-RII were 95, 72.7, and 44.5 percent respectively. Although the frequency of responders to PvDBP-RII was lower, this frequency increased in individuals following multiple malarial infections. Individually, the specific antibody levels did not decline significantly nine months after treatment, except to PvMSP1(19). Our results further confirm a complex regulation of the immune response to distinct blood stage antigens. The reason for that is presently unknown but it may contribute to the high risk of re-infection in individuals living in the endemic areas.
Assuntos
Humanos , Animais , Anticorpos Antiprotozoários/imunologia , Imunoglobulina G/imunologia , Malária Vivax/imunologia , Proteína 1 de Superfície de Merozoito/imunologia , Plasmodium vivax/imunologia , Ensaio de Imunoadsorção Enzimática , Proteína 1 de Superfície de Merozoito/química , Proteínas Recombinantes/imunologiaRESUMO
A multianalyte Dot-enzyme-linked immunosorbent assay (Dot-ELISA-Multi) with Trypanosoma cruzi epimastigote alkaline extract (EAE), trypomastigote excreted-secreted antigen (TESA), recombinant protein derived from 19-kDa C-terminal region of the Plasmodium vivax merozoite surface protein 1 (PvMSP1(19)), Plasmodium falciparum Zwittergent extract (Pf-Zw), and Treponema pallidum Zwittergent extract (Tp-Zw) was standardized and evaluated as a method for surveying IgG-specific antibodies in Chagas disease, malaria, and syphilis in a single test. The study was carried out on serum samples from 52 patients with chronic Chagas disease, 103 individuals with current (parasitemic) or past malaria (aparasitemic), 43 patients with syphilis, 21 individuals with heterologous antibodies, and 100 blood donors. Dot-ELISA-Multi yielded 99% specificity for Chagas disease and 100% for malaria and syphilis. The test sensitivity was 100% for chronic Chagas disease, 88% for syphilis, 90% for P. vivax, and 47% for P. falciparum. In past malaria individuals, positivity was 92%. Therefore, Dot-ELISA-Multi can be useful under field conditions where laboratory facilities and resources are scarce, for small-scale epidemiologic studies.
Assuntos
Doença de Chagas/diagnóstico , Ensaio de Imunoadsorção Enzimática/métodos , Imunoglobulina G/sangue , Malária Falciparum/diagnóstico , Sorodiagnóstico da Sífilis/métodos , Animais , Doença de Chagas/imunologia , Humanos , Malária Falciparum/imunologia , Sensibilidade e EspecificidadeRESUMO
BACKGROUND: The naturally-acquired immune response to Plasmodium vivax variant antigens (VIR) was evaluated in individuals exposed to malaria and living in different endemic areas for malaria in the north of Brazil. METHODS: Seven recombinant proteins representing four vir subfamilies (A, B, C, and E) obtained from a single patient from the Amazon Region were expressed in Escherichia coli as soluble glutathione S-transferase fusion proteins. The different recombinant proteins were compared by ELISA with regard to the recognition by IgM, IgG, and IgG subclass of antibodies from 200 individuals with patent infection. RESULTS: The frequency of individuals that presented antibodies anti-VIR (IgM plus IgG) during the infection was 49%. The frequencies of individuals that presented IgM or IgG antibodies anti-VIR were 29.6% or 26.0%, respectively. The prevalence of IgG antibodies against recombinant VIR proteins was significantly lower than the prevalence of antibodies against the recombinant proteins representing two surface antigens of merozoites of P. vivax: AMA-1 and MSP119 (57.0% and 90.5%, respectively). The cellular immune response to VIR antigens was evaluated by in vitro proliferative assays in mononuclear cells of the individuals recently exposed to P. vivax. No significant proliferative response to these antigens was observed when comparing malaria-exposed to non-exposed individuals. CONCLUSION: This study provides evidence that there is a low frequency of individuals responding to each VIR antigens in endemic areas of Brazil. This fact may explain the host susceptibility to new episodes of the disease.