Background As malaria transmission intensity declines, the heterogeneity in infectious burden becomes pronounced. There is thus the need for more sensitive tools to identify micro-geographic areas of higher risk for targeted interventions. We sought to evaluate several immunogenic peptides of P. falciparum, secreted ookinete and sporozoite proteins (PSOP24) and possibly validate specific short sequence immunogenic peptides as an infectious bite marker for assessing malaria transmission intensity and dynamics.
Methods We conducted four cross-sectional serological and parasitological surveys within one peri-urban and one rural community about 3 km apart, in South-western Ghana. The field surveys were conducted from November 2012 to July 2014 across dry and rainy seasons. Several bioinformatics models were used to predict the immunogenic epitopes of PSOP24 peptides. Total IgG antibody response were determined for three most promising peptides (PSOP24–374, PSOP24–375 and PSOP24–377), together with MSP119, CSP and salivary gland antigen. Alongside we determined parasite prevalence and density as well as the entomological inoculation rates.
Results Peptide PSOP24-377 showed seasonal variation with a twofold increase in IgG response in the high-transmission rainy season. This collaborates with the twofold increase in IgG response to the mosquito salivary antigen gSG6-P1. Also, PSOP24-377 was able to show a subtle difference from Ayeigbekorpe to Odumase during the dry season and a high sero-prevalence between the two communities during the rainy season. This was in contrast with gSG6-P1 because, while PSOP24-377 measures sero-response to infectious bites, gSG6-P1 measure responses to only vector exposure. The immune response variation determined by PSOP24-377 correlated with parasite prevalence and the entomological inoculation rates.
Conclusion The preliminary data points to the potential of PSOP24-377 as an infectious bite marker. This may be exploited as a routine surveillance tool for monitoring malaria transmission at the community level.
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