Acquired immune response to defined Plasmodium vivax antigens in individuals residing in northern India.

In this investigation, we evaluated the naturally acquired immune response to Plasmodium vivax stage-specific antigens in individuals of different age groups belonging to malaria endemic areas of northern India. Four synthetic peptides containing both B- and T-cell epitopes from P. vivax circumsporozoite protein, merozoite surface protein-1, apical membrane antigen-1 and gametocyte surface antigen-1 were used to determine both humoral and cellular immune responses. Immunity, in terms of antibody response and T-cell proliferation against these stage-specific peptides, has been observed in the study subjects. The results demonstrated age-dependent antibody response in this population. Forty two patients were diagnosed with P. vivax. There was a significant association (P=0.013) between number of antibody responders and recognition of stage-specific epitopes by antibodies. The antibody response to B-epitopes of P. vivax CSP, MSP1, AMA1 and GAM1 was associated with age; adults responded more frequently to these antigens than did younger children. In this population, 66% (201/304) cases showed seropositivity to all peptides and 13% (41/304) showed negative response. Peripheral blood mononuclear cells of more than 75% of individuals proliferated in response to stimulation by all four epitopes. In conclusion, the results demonstrated immunogenicity of the epitopes to P. vivax in population of this endemic zone. Copyright 2009 Elsevier Masson SAS. All rights reserved.