Genetic polymorphism of and vaccine candidate genes in pre-artemisinin era clinical isolates from Lakhimpur district in Assam, Northeast India.

Background: Northeast India shares its international border with Southeast Asia and has a number of malaria endemic zones. Monitoring genetic diversity of malaria parasites is important in this area as drug resistance and increasing genetic diversity form a vicious cycle in which one favours the development of the other. This retrospective study was done to evaluate the genetic diversity patterns in strains circulating in North Lakhimpur area of Assam in the pre-artemisinin era and compare the findings with current diversity patterns.

Methods: Genomic DNA extraction was done from archived blood spot samples collected in 2006 from malaria-positive cases in Lakhimpur district of Assam, Northeast India. Three antigenic markers of genetic diversity were studied - (block-2), (block-3) and the RII region of using nested PCR.

Results: Allelic diversity was examined in 71 isolates and high polymorphism was observed. In eight genotypes were detected; K1 (single allele), MAD20 (six different alleles) and RO33 (single allele) allelic families were noted. Among genotypes, 22 distinct alleles were observed out of which FC27 had six alleles and IC/3D7 had 16 alleles. In RII region of nine genotypes were obtained. Expected heterozygosity ( ) values of the three antigenic markers were 0.72, 0.81 and 0.88, respectively. Multiplicity of infection (MOI) values noted were 1.28, 1.84 and 1.04 for and respectively.

Conclusion: Results suggest a high level of genetic diversity in ( of and ) and the RII region in Northeast India in the pre-artemisinin era when chloroqunine was the primary drug used for uncomplicated malaria. Comparison with current studies have revealed that the genetic diversity in these genes is still high in this region, complicating malaria vaccine research.