MOLECULAR AND HUMORAL CHARACTERIZATION OF PLASMODIUM FALCIPARUM MALARIA IN WADMEDANI, SUDAN

Abstract

A total of 570 samples of both sexes were collected from malaria-suspected patients who attended Medani Pediatric and adult teaching Hospital during August-December 2005. That period was the peak of malaria transmission season in the area. Out of these, 155 samples were detected to be positive for malaria and 140 cases (90%) out of the positive samples were due to Plasmodium falciparum and the rest, which were excluded from the study, (15 patients) were due to other plasmodium species. Based on the clinical data, the Plasmodium faciparum patients were classified as asymptomatic (7 patients) and symptomatic patients (133 patients). Among the symptomatic patients, 106 (75.7%) were detected as mild anemia, 24 (17.1%) as severe anemia and 10 (7.2%) as subject with normal hemoglobin level. Among the symptomatic patients also there are 22 cerebral malaria, 12 pregnant, 8 patient with splenomegally and two with hepatomegally. Patients are categorized into 4 age groups, group 1 has 71 (50.7%) individuals followed by groups 2,3, and 4 which have 44 (31.4%), 17 (12.1%), and 8 (5.8%) individuals respectively. One of the goals of this work was molecular characterization of the parasite populations circulating in Gazira, central part of Sudan. This work investigated the extent of genetic polymorphism in P. falciparum field isolates from Gazira. Allelic diversity was analyzed in the highly polymorphic parasite genes encoding the merozoite surface proteins-1 (MSP-1) and -2 (MSP-2) and the glutamate-rich protein (GLURP) by the polymerase chain reaction. Different size polymorphism was detected in all genes analyzed, with 13 and 8 variants for the MSP-1 and MSP-2 alleles, respectively, and 5 size variants for the GLURP. Moreover, based on the studied genetic markers, most infections consisted of more than one genetically distinct parasite clones. These results suggest that the P. falciparum parasite populations circulating in this region are genetically homogeneous and point to an association between the extent of parasite genetic diversity and the intensity of malaria transmission Different genotypes were found to be associated with severity of disease. In this respect, association between high parasitemia and anemia on one hand and variants of K1 were found, MAD20, RO33 and FC allelic families on the other hand. In addition, some IV variants of the allelic families were found to be associated with children between 0-10 years of age. Individuals living in malaria endemic areas generally harbor multiple parasite strains which known by Multiplicity of infection (MOI) and can be used as an indicator of immune status. One of the goals of this study was to examine the MOI in Plasmodium faciparum-infected samples and to relate it to severity of the disease. Results of genotyping reveal that MOI was significantly higher at the end of transmission season and the majority of PCR positive subjects had multiple infections at that time points (54%). No association between MOI and severity of disease was observed. MOI did not vary over age at any time points. There was a significant correlation between MOI and parasite density, as the higher parasite counts increases the probability of having multiple infections. One of the major goals of this work was the investigation of the immune response of glutamate rich protein among the study population as an indicator for acquisition of protective immunity. This is achieved by estimation of IgG, IgG1, IgG3 and IgM antibodies directed against GLURP-R0, GLURP-R1 and GLURP-R2. The results indicate comparatively high titres of these antibodies to the three fragments of GLURP, although R2 and R0 encountered with significantly higher concentrations of the antibodies. The results also showed that IgG3 was presented with high concentration followed by IgG1 suggesting their protective role and their major participation in acquisition of immunity to malaria. The results of association between immune response and different strain of Plasmodium population isolated in this work reveal that some strain are encountered with high immune response and severity of malaria. This association supports the speculation of the presence of strain-specific immunity and premunition among inhabitants of malaria endemic areas. The results also re-enforce the ongoing announcement that any future malaria vaccine should include GLURP fragments notably GLURP-R2 and GLURP-R0. Ethical clearance for this work has been approved by the ethical committee of the institute of endemic diseases, faculty of medicine, University of Khartoum.