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
