FIG 4.

Magnitude of homologous and heterologous responses 1 month after CHMI at a single serum dilution of 1:500 to PvCSP, PvMSP, PfCSP, and PfMSP. (A) P. vivax challenge induces both IgM and IgG responses to both homologous preerythrocytic and erythrocytic antigens. The majority of heterologous responses were IgM. The horizontal line represents the median value. (B) After P. falciparum CHMI, a large percentage of individuals show homologous and heterologous reactivity, but no IgG responses to either homo- or heterologous CSP were seen. The horizontal line represents the median value. There was a positive Spearman correlation between homologous IgM and IgG for PvCSP (r = 0.38) (A) as well as PfMSP (r = 0.52; P = 0.07) (B). The only heterologous correlation was seen between anti-CSP and MSP IgMs: PvCHMI sera showed a weak positive correlation between PfCSP and PfMSP (A), while the PfCHMI sera demonstrated a high correlation between PvCSP and PfMSP IgMs (r = 0.9; P = 0.04) (B). Ab, antibody.