Umar Farooq1, N Malla, M L Dubey. 1. Department of Parasitology, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
Abstract
BACKGROUND & OBJECTIVES: Malaria is a major public health problem in tropical and sub-tropical countries. Malaria vaccine is highly desirable as an adjunct to existing malaria control measures. The polymorphism in vaccine candidate antigens might be a hurdle in developing an effective vaccine. Merozoite surface protein-2, apical membrane antigen-1 and circumsporozoite protein of Plasmodium falciparum are vaccine candidate antigens. The aim of this study was to detect extent of genetic polymorphism in potential vaccine candidate antigen genes, i.e. msp-2, ama-1 and csp of P. falciparum isolates prevalent in northern and north-western parts of India. METHODS: Overall 88 parasite isolates of P. falciparum were collected during July 1998-March 2002 from different parts of northern and north-western India. DNA was extracted and analyzed for genetic polymorphism by PCR-RFLP method. For msp-2 gene, family-specific (FC-27 and 3D7) nested PCR was also performed. RESULTS: PCR showed size polymorphism in all the target genes. Three alleles were observed in msp-2 and ama-1, while only two in csp. RFLP of ama-1 and csp with Dra-1 and Ssp-1 endonucleases respectively, failed to differentiate isolates in sub-allelic types, while Hinf-I digestion of msp-2 amplicons differentiated three alleles into two distinct allelic families, i.e. FC-27 and 3D7. The allelic family-specific PCR generally confirmed the results of PCR-RFLP except in a few isolates, which showed mixed (two) clones of msp-2 gene. INTERPRETATION & CONCLUSION: There was extensive polymorphism in msp-2 gene while ama-1 and csp genes showed low polymorphism which may be due to the functional constraints of these proteins. The low level transmission of malaria in the study area may also be a factor for low polymorphism.
BACKGROUND & OBJECTIVES:Malaria is a major public health problem in tropical and sub-tropical countries. Malaria vaccine is highly desirable as an adjunct to existing malaria control measures. The polymorphism in vaccine candidate antigens might be a hurdle in developing an effective vaccine. Merozoite surface protein-2, apical membrane antigen-1 and circumsporozoite protein of Plasmodium falciparum are vaccine candidate antigens. The aim of this study was to detect extent of genetic polymorphism in potential vaccine candidate antigen genes, i.e. msp-2, ama-1 and csp of P. falciparum isolates prevalent in northern and north-western parts of India. METHODS: Overall 88 parasite isolates of P. falciparum were collected during July 1998-March 2002 from different parts of northern and north-western India. DNA was extracted and analyzed for genetic polymorphism by PCR-RFLP method. For msp-2 gene, family-specific (FC-27 and 3D7) nested PCR was also performed. RESULTS: PCR showed size polymorphism in all the target genes. Three alleles were observed in msp-2 and ama-1, while only two in csp. RFLP of ama-1 and csp with Dra-1 and Ssp-1 endonucleases respectively, failed to differentiate isolates in sub-allelic types, while Hinf-I digestion of msp-2 amplicons differentiated three alleles into two distinct allelic families, i.e. FC-27 and 3D7. The allelic family-specific PCR generally confirmed the results of PCR-RFLP except in a few isolates, which showed mixed (two) clones of msp-2 gene. INTERPRETATION & CONCLUSION: There was extensive polymorphism in msp-2 gene while ama-1 and csp genes showed low polymorphism which may be due to the functional constraints of these proteins. The low level transmission of malaria in the study area may also be a factor for low polymorphism.
Authors: Issiaka Soulama; Jude D Bigoga; Magatte Ndiaye; Edith C Bougouma; Josephine Quagraine; Prisca N Casimiro; Timothy T Stedman; Sodiomon B Sirima Journal: Am J Trop Med Hyg Date: 2011-02 Impact factor: 2.345