Humoral Immune Response to Malaria Vaccine Candidates (RESA and CSP) in Malaria Endemic Areas in Sudan

Abstract

The present study was carried-out in Kosti town, White Nile state, Sudan. This area is characterized by a seasonal but stable transmition. During two cross-sectional studies curried-out in March 2003 and January 2004, a total of 173 samples was collected to determine the parasitological and molecular characterization of the parasite and to determine the immune response to malaria vaccine candidates (RESA and CSP). Microscopic examination has revealed that the parasite point prevalence was 26.4% and 38.5% in 2003 and 2004 respectively, and 96.2% of all malaria cases were due to P.falciparum. Using PCR technique, 21 out of 173 (12.1%) (9 samples in 2003 and 12 samples in 2004) samples with negative BFs were found to harbour low parasitaemia, this lead to increase in PCR point prevalence. Using merozoite surface proteins (MSP1 and MSP2) as genotypic markers, 71 samples were successively genotyped for the presence of MSP-1 alleles (MAD20, K1 and RO33) and MSP-2 alleles (FC27 and IC1). The frequencies of these alleles indicated that RO33 is the predominant MSP-1 allelic family and IC1 was found to be the predominant allelic family for MSP-2. In this study 10 allelic sizes for MSP-1 and 10 allelic sizes for MSP-2 were found to be shared between samples collectedin 2003 and 2004 (3 sizes for MAD20, 3 sizes for K1, 4 sizes for RO33, 6 sizes for IC1 and 4 sizes for FC27). The mean number of parasite clones per individual infection was 3.25-3.5 in 2003 and 2004 respectively. 22.3% and 57.7% samples in 2003 and 2004 respectively harboured more than one parasite clone