Abstract:
Background: Plasmodium falciparum genetic diversity and multiplicity of infection (MOI) are parasite features that
have been suggested to influence the acquisition of protective immunity against malaria. This study sought to
assess the relationship between MOI and parasite density (PD) in malaria patients living in the Central Region of
Ghana and to determine whether naturally occurring antibody levels against P. falciparum GLURP (PF3D7_1035300)
and MSP3 (PF3D7_1035400) antigens are associated with decreased parasite load.
Methods: Dried filter paper blood blots were obtained from children and adults diagnosed with uncomplicated P.
falciparum malaria. Microscopy was used to estimate P. falciparum parasite density and polymerase chain reaction
(PCR) amplification of the polymorphic regions of msp1 (PF3D7_0930300) and msp2 (PF3D7_0206800) was used for
parasite genotyping and MOI determination. ELISA was used to measure the serum IgG concentration of R0
fragment of GLURP (GLURP(R0)) and MSP3 antibodies.
Results: All 115 samples were positive for P. falciparum by PCR using either the msp1 or msp2 genotyping primer
sets. The most prevalent msp1 and msp2 alleles were KI and 3D7, respectively. The geometric mean (GM) for MOI
determined by both msp1 and msp2 genotyping was 1.3 for the entire population and was generally higher in
children than in adults. Seropositivity was estimated at 67 and 63% for GLURP(R0) and MSP3 antibodies,
respectively, and antibody titers were negatively correlated with parasite density.
Conclusions: The negative correlation between naturally occurring GLURP(R0) and MSP3 antibody levels and
parasite density observed in this study suggest that augmenting the antibody response with the GMZ2 vaccine
could enhance protection in the Central Region of Ghana.
