Effect of varying malaria parasite multiplicity of infection on the quality and quantity of anti-gametocyte antibodies in school children: A longitudinal study

Abstract

The sexual stages (gametocytes) of Plasmodium falciparum are critical to malaria transmission and are a target for the development of malaria transmission blocking vaccine candidates. Accelerating development of this vaccine requires understanding the characteristics of naturally-induced antibody responses against gametocyte antigens, including Pfs230, Pfs48/45 that have the potential to prevent parasite transmission. The number of P. falciparum clones in an infection can vary over time, which may lead to variation in antibody quality and quantity against gametocytes in a host. This study therefore assessed the impact of varying

multiplicity of infection (MOI) on the quantity (level) and quality (avidity) of

naturally-induced antibody responses against Pfs230 and Pfs48/45 in

asymptomatic children. Venous blood (2.5 ml) was collected from 109 children (6 to 12 years old) every 2-months beginning in November 2017 to May 2018. Plasma samples were used in indirect ELISA test to measure IgG concentrations

and avidity against Pfs230 and Pfs48/45 antigens. Msp2 genotyping was done on

extracted DNA from dried blood spot to determine MOI. Increased MOI at time points close to peak season positively correlated with IgG against Pfs48/45.

Positive correlation existed between IgG against both antigens despite the quality and quantity of IgG against them seems to be inversely correlated from the middle to the end of the dry season. Increased MOI near the peak season positively correlated with Pfs48/45 but not Pfs230 IgG levels suggests that repeated infections in the community preferentially boosts antibodies targeting Pfs48/45 than Pfs230 in children. However, larger studies are needed to affirm this finding