Impact of Plasmodium falciparum submicroscopic infection on the expression of anti-VAR2CSA IgG antibodies in women at delivery in a Health Center in Yaounde, Cameroon

Abstract
Placental malaria is a tropical scourge associated with serious adverse effects on the mother and the foetus. Pregnancy leads to a selection of P. falciparum strains expressing the VAR2CSA antigen, which sequester in the placental tissue via the chondroitin sulphate A, leading to the expression of specific IgG antibodies. This study aimed at determining the impact of a submicroscopic P. falciparum infection diagnosed by the RT-LAMP technique on the expression of IgG anti-VAR2CSA in women at delivery in Yaoundé, Cameroon. Thus, as part of a cross-sectional study, 322 women at delivery were enrolled at the Marie Reine Medical Health Center in Etoudi, Yaoundé. Peripheral, placental blood and small pieces of placental tissue were collected from these women immediately after delivery. Placental malaria and submicroscopic peripheral blood infection were diagnosed by microscopic examination of the placental tissue smear and by RT-LAMP respectively. Plasma levels of antibodies specific to the entire VAR2CSA (VAR2CSA-FV2) molecule and its DBL-5 and DBL-3 domains were determined using the Multianalyte Platform assay. The results revealed that the prevalence of placental microscopic infection was 15.2% while that of submicroscopic infection was 47.1%, the latter did not vary with parity. The seroprevalence of IgG antibodies to VAR2CSA-FV2, DBL-5 and DBL-3 domains were slightly higher in women with submicroscopic malaria infection (31%, 27.7% and 11.9% respectively) compared to uninfected women (28.7%, 23% and 6, 9%). Furthermore, the plasma levels of these anti-FV2, anti-DBL-5, and anti-DBL-3 IgGs were positively associated with parity (p< 0.0001, p < 0.001 and p=0.0002), microscopic parasitaemia of the impression smear (p< 0.0001, p = 0.0001 and p = 0.0004, respectively). These results overall suggest that submicroscopic infection diagnosed by RT-LAMP does not have a significant impact on anti-VAR2CSA IgG expression and cannot distinguish uninfected women from those with submicroscopic malaria infection diagnosed by the RT-LAMP technique.
Keywords: Women, Plasmodium falciparum, submicroscopic infection, Placental malaria, IgG anti-VAR2CSA.