Transplacentally transferred functional antibodies against Plasmodium falciparum decrease with age

Abstract

Transplacental transfer of antibodies from clinically malaria immune pregnant women to their fetuses is thought to provide passive protection against malaria during infancy. However, the presences and duration of functional antibodies against Plasmodium falciparum (Pf) in newborns has not been described. We used growth inhibition assays (GIA) to measure total anti-malaria functional antibodies present at birth and over the following year. Samples were drawn from cord blood (n=86) and in infants at six and 12 months of life (n=86 and 65 respectively). Three laboratory Pf strains (D10, W2mef, 3D7) and a field isolate (Msambweni 2006) were used in the assays. Median (ranges) GIA levels for cord plasma differed between laboratory parasite strains: D10, 0% (0-81); W2mef, 6% (0-80); 3D7, 18% (0-88); Msambweni 2006, 6% (0-43) (P<0.001, Wilcoxon signed-rank test). GIA levels against all Pf strains were found to decline in infants from birth to six months (P<0.01, Wilcoxon, signed-rank test). Functional antibodies as measured by GIA are transferred to the fetus and wane in the infants over time. Infant protection from clinical malaria disease may in part be mediated by these functional anti-malaria antibodies.

Keywords: Functional antibodies; Growth inhibition assay; Malaria; Plasmodium falciparum.

Figure 1

A: GIA results for N=270 samples of cord blood for each laboratory parasite line (D10, W2Mef, and 3D7). The results are a composite of three separate experiments (N=104, N=54 and N=112; Wilcoxon signed-rank test). B: GIA results for N=112 samples of cord blood for each laboratory parasite line (D10, W2Mef, and 3D7) and Msambweni 2006 (Wilcoxon signed-rank test).

Figure 2

GIA results from paired cord blood (N=86), six month follow-up (N=86), and 12 month follow-up (N=65) with laboratory parasite strains (3D7, W2Mef, and D10) and Msambweni 2006 field isolate (Wilcoxon signed-rank test).