IMMUNOGLOBULIN-G REACTIVITIES TO RHOPTRY-ASSOCIATED PROTEIN-I ASSOCIATED WITH DECREASED LEVELS OF PLASMODIUM-FALCIPARUM PARASITEMIA IN TANZANIAN CHILDREN

In the Muheza region of Tanzania, an area with holoendemic malaria, th e proportion of responders with IgG enzyme-linked immunosorbent assay reactivities to recombinant rhoptry-associated protein-1 (rRAP-1) as w ell as IgG reactivities to a repeat region of the acidic-basic repeat antigen (ABRA) increased with age. The proportion of responders with I gM reactivities to rRAP-1 increased with age in the first three decade s. However, levels of IgG reactivities to rRAP-1 did not increase with age, indicating high levels of reactivities among young children. Hig h P. falciparum densities were only detectable in children less than f ive years of age; in this group the proportion of IgG responders to rR AP-1 and to the ABRA repeat region was low but levels of IgG reactivit ies to rRAP-1 were inversely correlated with parasite density, suggest ing that immune recognition of the antigen may be associated with resi stance to infection. On the other hand, levels of IgG reactivities to the repeat region of ABRA increased with parasite densities in childre n 1-4 years of age. Two different profiles of IgG reactivities to rRAP -1 and to ABRA are detectable in young Tanzanian children and the Ig r eactivities against rRAP-1 may be a component of the immune reactions restricting parasite multiplication.