RESUMO
Peptide vaccine strategies using Plasmodium-derived antigens have emerged as an attractive approach against malaria. However, relatively few studies have been conducted with malaria-exposed populations from non-African countries. Herein, the seroepidemiological profile against Plasmodium falciparum of naturally exposed individuals from a Brazilian malaria-endemic area against synthetic peptides derived from vaccine candidates circumsporozoite protein (CSP), liver stage antigen-1 (LSA-1), erythrocyte binding antigen-175 (EBA-175), and merozoite surface protein-3 (MSP-3) was investigated. Moreover, human leukocyte antigen (HLA)-DRB1* and HLA-DQB1* were evaluated to characterize genetic modulation of humoral responsiveness to these antigens. The study was performed using blood samples from 187 individuals living in rural malaria-endemic villages situated near Porto Velho, Rondônia State. Specific IgG and IgM antibodies and IgG subclasses were detected by enzyme-linked immunosorbent assay, and HLA-DRB1* and HLA-DQB1* low-resolution typing was performed by PCR-SSP. All four synthetic peptides were broadly recognized by naturally acquired antibodies. Regarding the IgG subclass profile, only CSP induced IgG1 and IgG3 antibodies, which is an important fact given that the acquisition of protective immunity appears to be associated with the cytophilicity of IgG1 and IgG3 antibodies. HLA-DRB1*11 and HLA-DQB1*7 had the lowest odds of responding to EBA-175. Our results showed that CSP, LSA-1, EBA, and MSP-3 are immunogenic in natural conditions of exposure and that anti-EBA antibody responses appear to be modulated by HLA class II antigens.
Assuntos
Antígenos de Protozoários/imunologia , Cadeias beta de HLA-DQ/genética , Imunidade Humoral , Vacinas Antimaláricas/imunologia , Malária Falciparum/imunologia , Adolescente , Adulto , Anticorpos Antiprotozoários/sangue , Brasil/epidemiologia , Feminino , Humanos , Imunoglobulina G/sangue , Imunoglobulina M/sangue , Malária Falciparum/epidemiologia , Masculino , Pessoa de Meia-Idade , Plasmodium falciparum/imunologia , Proteínas de Protozoários/imunologia , Esporozoítos/imunologia , Adulto JovemRESUMO
BACKGROUND: The Plasmodium falciparum P126 protein is an asexual blood-stage malaria vaccine candidate antigen. Antibodies against P126 are able to inhibit parasite growth in vitro, and a major parasite-inhibitory epitope has been recently mapped to its 47 kDa N-terminal extremity (octamer repeat domain--OR domain). The OR domain basically consists of six octamer units, but variation in the sequence and number of repeat units may appear in different alleles. The aim of the present study was to investigate the polymorphism of P126 N-terminal region OR domain in P. falciparum isolates from two Brazilian malaria endemic areas and its impact on anti-OR naturally acquired antibodies. METHODS: The study was carried out in two villages, Candeias do Jamari (Rondonia state) and Peixoto de Azevedo (Mato Grosso state), both located in the south-western part of the Amazon region. The repetitive region of the gene encoding the P126 antigen was PCR amplified and sequenced with the di-deoxy chain termination procedure. The antibody response was evaluated by ELISA with the Nt47 synthetic peptide corresponding to the P126 OR-II domain. RESULTS: Only two types of OR fragments were identified in the studied areas, one of 175 bp (OR-I) and other of 199 bp (OR-II). A predominance of the OR-II fragment was observed in Candeias do Jamari whereas in Peixoto de Azevedo both fragments OR-I and OR-II were frequent as well as mixed infection (both fragments simultaneously) reported here for the first time. Comparing the DNA sequencing of OR-I and OR-II fragments, there was a high conservation among predicted amino acid sequences of the P126 N-terminal extremity. Data of immune response demonstrated that the OR domain is highly immunogenic in natural conditions of exposure and that the polymorphism of the OR domain does not apparently influence the specific immune response. CONCLUSION: These findings confirm a limited genetic polymorphism of the P126 OR domain in P. falciparum isolates and that this limited genetic polymorphism does not seem to influence the development of a specific humoral immune response to P126 and its immunogenicity in the studied population.
Assuntos
Anticorpos Antiprotozoários/imunologia , Polimorfismo Genético , Proteínas de Protozoários/genética , Proteínas de Protozoários/imunologia , Animais , Brasil , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Masculino , Reação em Cadeia da Polimerase , Polimorfismo Conformacional de Fita Simples , Análise de Sequência de DNAAssuntos
Doenças dos Bovinos/parasitologia , Criptosporidiose/parasitologia , Criptosporidiose/veterinária , Cryptosporidium/classificação , Cryptosporidium/isolamento & purificação , Doenças das Cabras/parasitologia , Síndrome da Imunodeficiência Adquirida/complicações , Animais , Bovinos , Criptosporidiose/epidemiologia , Criptosporidiose/transmissão , Cryptosporidium/genética , DNA de Protozoário/química , DNA de Protozoário/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Fezes/parasitologia , França/epidemiologia , Genes de Protozoários , Variação Genética , Genótipo , Cabras , Haiti/epidemiologia , Humanos , Epidemiologia Molecular , Filogenia , RNA Ribossômico 18S/genética , Análise de Sequência de DNARESUMO
In this work we investigated the frequency of polymorphism in exon II of the gene encoding most of the amino-terminal region of the serine rich antigen (SERA) in Plasmodium falciparum field samples. The blood samples were collected from P. falciparum infected individuals in three areas of the Brazilian Amazon. Two fragments have been characterized by polymerase chain reaction: one of 175 bp corresponding to the repeat region with 5 octamer units and one other of 199 bp related to the 6 repeat octamer units of SERA protein. The 199 bp fragment was the predominant one in all the studied areas. The higher frequency of this fragment has not been described before and could be explained by an immunological selection of the plasmodial population in the infected individuals under study. Since repeat motifs in the amino-terminal region of SERA contain epitopes recognized by parasite-inhibitor antibodies, data reported here suggest that the analysis of the polymorphism of P. falciparum isolates in different geographical areas is a preliminary stage before the final drawing of an universal vaccine against malaria can be reached.
Assuntos
Antígenos de Protozoários/genética , Plasmodium falciparum/genética , Polimorfismo Genético/genética , Sequência de Aminoácidos , Animais , Brasil , DNA de Protozoário/análise , Éxons , Dados de Sequência Molecular , Reação em Cadeia da PolimeraseRESUMO
In this work we investigated the frequency of polymorphism in exon II of the gene encoding most of the amino-terminal region of the serine rich antigen (SERA) in Plasmodium falciparum field samples. The blood samples were colleted from P. falciparum infected individuals in three areas of the Brazilian Amazon. Two fragments have been characterized by polymerase chain reaction: one of 175 bp corresponding to the repeat region with 5 octamer units and one other of 199 bp related to the 6 repeat octamer units of SERA protein. The 199 bp fragment was the predominant one in all the studied areas. The higher frequency of this fragment has not been described before and could be explained by an immunological selection of the plasmodial population in the infected individuals under study. Since repeat motifs in the amino-terminal region of SERA contain epitopes recognized by parasite-inhibitor antibodies, data reported here suggest that the analysis of the polymorphism of P. falciparum isolates in different geographical areas is a preliminary stage before the final drawing of an universal vaccine against malaria can be reached.
Assuntos
Animais , Antígenos de Protozoários/genética , Plasmodium falciparum/genética , Polimorfismo Genético/genética , Sequência de Aminoácidos , Brasil , DNA de Protozoário/análise , Éxons , Dados de Sequência Molecular , Reação em Cadeia da PolimeraseRESUMO
We investigated the relationships between class II human leukocyte antigens (HLA) and the antibody response to Plasmodium falciparum p126 protein and to its amino-terminal portion (Nt47) in 2 malaria-endemic villages in Brazil, Colina and Ribeirinha. All people from the endemic areas had anti-p126 antibodies, and the frequencies of anti-Nt47 antibodies were similar in both communities (66% for Colina and 75% for Ribeirinha). Typing of HLA showed that Colina and Ribeirinha groups had no significant differences in HLA antigen frequencies. However, in both groups, significant associations between positive response to anti-Nt47 and presence of HLA-DR4, as well as between absence of response and presence of HLA-DR15, were observed. The predominance of positive responses to Nt47 among HLA-DR4 people was independent of the presence of any particular allele. There was no evidence for association between HLA-DQB1 alleles and antibody response to Nt47. Thus, naturally exposed people with different HLA class II antigens seem to respond differently to Nt47, indicating that the choice of relevant peptide sequences may have important consequences for subunit vaccine development.
Assuntos
Anticorpos Antiprotozoários/sangue , Antígenos de Protozoários/imunologia , Antígenos HLA-D/imunologia , Plasmodium falciparum/imunologia , Proteínas de Protozoários/imunologia , Adulto , Alelos , Animais , Formação de Anticorpos , Brasil , Feminino , Genes MHC da Classe II , Geografia , Antígenos HLA-DR/análise , Subtipos Sorológicos de HLA-DR , Antígeno HLA-DR4/análise , Teste de Histocompatibilidade , Humanos , Malária Falciparum/imunologia , MasculinoRESUMO
The P126 protein, a parasitosphorus vacuole antigen of Plasmodium falciparum has beenshoen to induce protective immunity in Saimiri and Aotus monkeys. In the present work we investigated its immunogenicity. Our results suggest that the N-term of P126 is poorly immunogenic and antibody response against the P126 could be under a MHC restricted control in C57BL/6(H-2b) mice, which could be problematic in ternms of a use of the P126 in a vaccine program. However, we observed that a synthetic peptide, copying the 6 octapeptide repeat corresponding to the N-term of the P126, induces an antibody response to the native molecule in C57BL/6 non-responder mice. Moreover, the vaccine-P126 recombinant induced anmtibodies against the N-term of the molecule in rabbits while the unprocessed P126 did not