Genetic Polymorphism in Msp-2, Ama-1 and Csp Genes in Plasmodium Falciparum Field Isolates from North and North-Western India (Research Articles) (Report‪)‬

Introduction Malaria is an important tropical disease with an estimated global burden of 300 to 660 million cases every year, of which around 90% occur in sub-Saharan Africa where mortality due to malaria is also reported to be higher than elsewhere (1,2). The increase in incidence of Plasmodium falciparum, the agent of severe and complicated malaria in India is a matter of immense clinical and public health importance. The situation has become more complicated due to the spread of chloroquine resistant strains of P. falciparum throughout the world and in India (3-6). The alternative new drugs are cost intensive and potentially toxic, therefore, an effective malaria vaccine development is necessary. It will be a useful adjunct to existing control measures for malaria. Malaria research is now focused on immunologically relevant proteins, especially those expressed on the parasite surface and which are the first ones to come in contact with the host's immune system. Several antigens of P. falciparum from different stages of the life cycle have been characterized for use as a malaria vaccine (7-9). Several malaria vaccines have undergone field trials but these have shown low efficacy during the field trials (10). One of the reasons for the low efficacy could be the antigenic polymorphism in the vaccine candidate antigens (11). Recently, Phase 1-2b clinical trial of a vaccine based on msp-2, in Papua New Guinea has indicated that antigen of one allelic type included in the vaccine may be more effective against the parasites having same allelic type than those having other alleles (12). Merozoite surface protien-2 (MSP-2), apical membrane antigen-1 (AMA-1) and circumsporo-zoite protein (CSP) of P. falciparum are considered prime candidates for the development of malaria vaccine (13,14). Polymorphism in these malaria vaccine candidate antigens has been reported from several parts of the world (7,8,15,16). However, limited reports are available on the genetic diversity existing among P. falciparum populations of India (17-20). Some of these vaccine candidate genes have been reported to be dimorphic, e.g. msp-1 and msp-221. The analysis of genetic variation among the isolates of P. falciparum prevalent in a region is important before the development or field trial of a malaria vaccine in that geographical region.