Naturally acquired antibody responses to the C-terminal region of merozoite surface protein 1 of Plasmodium vivax in Korea

We expressed a protein in Saccharomyces cerevisiae in order to evaluate the humoral immune responses to the C-terminal region of the merozoite surface protein 1 of Plasmodium vivax, This protein (Pv200(18)) had a molecular ma ss of 18 kDa and was reactive with the sera of individuals with patent viva x malaria on immunoblotting analysis. The levels of immunoglobulin M (IgM) and Ige antibodies against Pv200(18) were measured in 421 patients with viv ax malaria (patient group), 528 healthy individuals from areas of nonendemi city (control group 1), and 470 healthy individuals from areas of endemicit y (control group 2), using the indirect enzyme-linked immunosorbent assay ( ELISA) method. To study the longevity of the antibodies, 20 subjects from t he patient group were also tested for the antibody levels once a month for 1 year. When the cutoff values for seropositivity were determined as the me an + 3 x standard deviation of the antibody levels in control group 1, both IgG and IgM antibody levels were negative in 98.5% (465 of 472) of control group 2, The IgG and IgM antibodies were positive in 88.1% (371 of 421) an d 94.5% (398 of 421) of the patient group, respectively. The IgM antibody b ecame negative 2 to 4 months after the onset of symptoms, whereas the Ige a ntibody usually remained positive for more than 5 months. In conclusion, in direct ELISA using Pv200(18) expressed in S. cerevisiae may be a useful dia gnostic method for vivax malaria.