Immune Response to Genetically Diverse Plasmodium Falciparum Gametocytes in Areas of High and Low Malaria Transmission Intensity in Southern Ghana.

ABSTRACT

Plasmodium falciparum gametocytes are able to infect the mosquito even at levels below microscopic detection and are responsible for malaria transmission. Gametocytes are exposed to immune pressure from the host and as a result, the host is able to develop antibodies against these gametocytes. However, it has not been determined whether naturally acquired immune response against gametocytes have a direct correlation with the presence of sub-microscopic gametocytes in the peripheral blood. The aim of the study was to determine differences in the prevalence of gametocytes and access the quality and quantity of immune responses to gametocytes in two towns in Ghana which have different malaria transmission patterns and also determine whether genetically diverse gametocytes induce altered immune responses. The immunogenicity of gametocyte antigens Pfs230 and Pfs48/45 were evaluated using archived serum samples from a longitudinal study involving children between the ages of 6 - 12 years.

Briefly, the levels of antibodies against two gametocyte antigens Pfs230 and Pfs48/45 in sera of Ghanaian children were monitored using ELISA. Gametocyte prevalence and diversity was analyzed using amplification fragment length polymorphism of Pfg377 (female gametocyte osmiophilic gene) in corresponding cDNA samples. ELISA results showed that there was significant similarity in means of the IgG and IgM antibody response for both Pfs230 and Pfs48/45. PCR detected a higher allelic frequency of the Pfg377 gene in gametocytes found in Obom as opposed to Abura. The correlation analysis with SPSS statistical software showed that there was no significant association (r < 0.4 and p-value > 0.05) between naturally acquired immunity in the host and gametocyte diversity. However, further work would have to be done such as molecular quantification of the Pfg377 gene and membrane feeding with the serum samples to see its possible effect on malaria transmission.