NATURALLY-OCCURRING PLASMODIUM-SPECIFIC IGA ANTIBODY IN HUMANS FROM A MALARIA ENDEMIC AREA

Blood samples collected from individuals belonging to an endemic area in Uttar Pradesh, were tested for plasmodial antigen specific immunoglobulin A (IgA) by enzyme immune assay using soluble extract of Plasmodium falciparum from culture. Among 773 (20.18%, P < 0.0001) samples 156 sera demonstrated a detectable seropositivity for antigen specific IgA. IgA levels were higher among individuals who experienced repeated attacks of malaria compared to acute infected patients. Among seropositive individuals the IgA titers were found increased with the age. Immunoglobulin isolated from sera having high level of IgA showed growth inhibitory effect in Plasmodium falciparum in vitro. A group of sera with high IgA antibody against Plasmodium falciparum crude antigen showed seronegativity with specific peptides. Statistically, no positive or negative correlations were observed between antigen specific IgG and IgA. However, there was a tendency towards negative correlation between IgA and IgM. Mechanisms for the parasite specific IgA production remain to be established.