Seasonal variation of anti-RESA/Pf155 Plasmodium falciparum antibodies in three localities from the state of Amapá, Brazil.

Anti-RESA/Pf155 antibodies were assayed in sera of individuals from three localities (Laranjal do Jari, Vila Padaria and Vila Paraíso) in the State of Amapá, Brazil, during the long-rains and short-rains seasons. All of these had negative blood smears for malaria. Most of the sera collected were positive in Indirect Fluorescent Antibody (IFA) with P. falciparum parasites, with no seasonal variation. A high percentage of these sera (62% to 100%) was RESA positive by Modified Indirect Fluorescent Antibody (MIFA), with a significant (p < 0.05) increase of geometric mean titers during the short-rains season, when the transmission of the disease is highest. ELISA with three repetitive RESA peptides (EENV)3 (4 x 3), (EENVEHDA)2 (8 x 2) and (DDEHVEEPTVA)2 (11 x 2) did not reveal statistically significant seasonal variations, although a small enhancement of positivity was observed in V. Padaria (15.3 to 38.8%) in the short-rains season with the 8 x 2 peptides, and with 4 x 3 and 8 x 2 peptides in V. Paraíso, with a decrease in 11 x 2. MIFA titers appeared to be correlated mainly to the peptide 4 x 3 and it was the immunodominant in the three localities.