The relationship between splenomegaly and antibody to the circumsporozoite protein of Plasmodium falciparum in two groups of women with high and low enlarged spleen rates in Madang, Papua New Guinea.

The objective of this study was to determine the prevalence of antibodies recognizing the circumsporozoite (CS) protein of Plasmodium by an enzyme-linked immunosorbent assay, in 2 subpopulations of women with significantly different enlarged spleen rates but similar exposure to malaria, on the north coast of Papua New Guinea. Antibody levels of immunoglobulin G (IgG) antibody to CS protein in the high and low spleen rate groups were similar (56.2% and 55.1%) but there was a significant difference in IgM (29.6% and 16.7%). In neither group did antibodies increase with parity (age). In both groups a high level of either IgG or IgM antibody to CS protein was associated with a high spleen rate and women with hyper-reactive malarious splenomegaly were more likely to be positive for both. Lower parasite rates were associated only with increased IgM antibody titres. High levels of antibody to blood-stage parasites were also present in the high spleen rate group, suggesting that antibodies to the CS protein were not protective. It is considered that cell-mediated immunity may be deficient in women with persistent splenomegaly.