ELISA HTLV retrovirus antibody reactivity associated with malaria and immune complexes in healthy Africans

A serological survey of 250 outpatients in rural Zaire showed that the prevalence of antibody against HTLV-I, HTLV-II, and HTLV-III, as detected by enzyme-linked immunosorbent assay, correlated strongly with level of antibodies against Plasmodium falciparum. The age curve for the prevalence of antibody against these retroviruses and high titres of antibodies against P falciparum were similar. Tests with control sera obtained from HTLV-III seropositive homosexual men and American subjects repeatedly infected with malaria who had high antibody titres against P falciparum indicated that there was no cross-reactivity between P falciparum and these retroviruses. Immune-complex levels, but not IgG, IgM, or IgE levels, also correlated strongly with seropositivity in the ELISA HTLV-I and HTLV-III assay, although immune-complex-positive control samples were negative. Possible explanations include coincidental distribution paralleling malaria; similar mode of transmission; virus activation and/or enhanced antibody production due to the effect of malaria on the immune system; and false-positive reactivity in the ELISA assay due to cross-reactive antibodies or other unknown factors.