Genetic heterogeneity of Wuchereria bancrofti populations at spatially hierarchical levels in Pondicherry and surrounding areas, south India.

Lymphatic filariasis (LF), caused by Wuchereria bancrofti is widely distributed in areas of India with variable geoclimatic factors. These factors, coupled with chemotherapeutic pressure exerted for past half a century may have influenced the genetic structure of the parasite populations. A complex genetic structure of parasite populations will have major consequences to the on-going global LF elimination programme. Hence, it is of interest to understand the genetic heterogeneity of W. bancrofti parasite populations. We studied the genetic heterogeneity of populations of W. bancrofti populations from mf carriers residing in an urban area of Pondicherry and surrounding villages through molecular (RAPD) fingerprinting. The analysis showed that W. bancrofti populations of an urban area were mostly highly heterogeneous, while those of rural areas were homogenous. The urban parasite populations appeared to be a pool of parasite population originating from surrounding rural areas. At least two genotypes, exhibiting high genetic differentiation and minimum gene flow between them, existed in Pondicherry urban areas. There was a minimum gene flow between parasite populations of villages. The genetic heterogeneity of parasite population in an adult microfilariae carrier was significantly high, possibly due to accumulation of different genotypes of the parasite with increasing age. The genetic heterogeneity of W. bancrofti populations in an individual mf carrier, in urban and rural areas, within an endemic area at large, and in different geographical regions of India may have far reaching implications to the epidemiology and strategies of chemotherapy control being adopted for LF elimination programme launched on a global scale.

Polymorphism of gp15/400 allergen gene of W. bancrofti from different regions of India endemic for lymphatic filariasis.

Nematode polyprotein allergens (NPA) are lipid binding/transport molecules that elicit elevated levels of IgE response in the infected host, leading to Th2 type of immune response. They also transport arachidonic acid and its metabolites that are known to be involved in the action of antifilarial drug, Diethylcarbamazine and hence are of great significance for the control of lymphatic filariasis. We investigated the polymorphism of gp15/400 polyprotein of 35 isolates of lymphatic filarial parasite Wuchereria bancrofti collected from different geographic locations of India. The repeat sub-unit of the gene was found to be highly conserved in all the isolates with only two nucleotide synonymous changes at positions 286 (A-G) and 337 (C-T). Since this molecule is highly conserved and has multifarious roles in the survival and pathogenesis of the parasite it has good potential as a target for drug, immunodulation tool and immunotherapy development.

Polymorphism of gp15/400 allergen gene of Wuchereria bancrofti from different regions of India endemic for lymphatic filariasis.

Nematode polyprotein allergens (NPA) are lipid-binding/transport molecules that elicit elevated levels of IgE response in the infected host, leading to Th2 type of immune response. They also transport arachidonic acid and metabolites that is known to be the action of antifilarial drug, diethylcarbamazine, and hence are of great significance to the control of lymphatic filariasis. We investigated the polymorphism of gp15/400 polyprotein of 35 isolates of lymphatic filarial parasite Wuchereria bancrofti collected from different geographic locations of India. The repeat subunit of the gene was found to be highly conserved in all the isolates with only two nucleotide synonymous changes at positions 369 (A-G) and 375 (C-T). As this molecule is highly conserved and has multifarious roles in the survival and pathogenesis of the parasite, it has good potential as a target for drug, immunodulation tools and immunotherapy development.

Isolation of Wuchereria bancrofti microfilariae from archived stained blood slides for use in genetic studies and amplification of parasite and endosymbiont genes.

Information on change in genetic diversity of Wuchereria bancrofti is important in view of the launching of the Global Lymphatic Filariasis Elimination Programme, as it may have important consequences on the control operations and on the potential resurgence after their withdrawal. Since attention was not paid to generate such information when the programme was launched, use of archived parasite material will provide an opportunity to derive this information in a prospective manner. In this paper a simple and effective technique is reported for isolation of microfilariae of W. bancrofti from dried and stained slides archived for several years and their utility in analysis of genetic structure and amplification of certain genes of the parasite is tested. The method was found to be efficient in purifying mf from the dried smears and the DNA of the parasite found to be useful in studying the genetic structure of Wuchereria bancrofti populations using random amplified polymorphic DNA (RAPD)-PCR and for amplifying genes of the parasite and its endosymbiont, Wolbachia sp.

Phylogeography of human lymphatic filarial parasite, Wuchereria bancrofti in India.

Wuchereria bancrofti, a nematode parasite causing human lymphatic filariasis is widely distributed in India. The phylogeography of this parasite was studied by constructing RAPD profiles of parasite populations collected from 71 microfilaria carriers residing in different geoclimatic regions of India. The analysis showed that the phylogeography of W. bancrofti populations is complex, with a high genetic divergence and gene flow among populations. The total genetic diversity (H(T)) and genetic differentiation (G(ST)) estimated for all the parasite populations were 0.0926 and 0.5859, respectively. The gene flow (Nm) between different regions indicated that two strains of W. bancrofti were prevalent in the country, one in the eastern side and the other on the western side of the Western Ghats. A highly significant genetic differentiation (F(ST) [theta] = 0.7978) was estimated between these two strains (chi 2 = 308.2789; P < 0.001). The gene flow between these strains was very low (0.2338). These two strains appear to have drifted genetically because of their geographic isolation by this thickly forested mountain range. The strain in the eastern side was found to be monophyletic in origin and is undergoing genetic divergence as the major parasite population in the country, spanning from eastern peninsular region to the northern plains. The variable geoclimatic factors and the antifilarial chemotherapeutical pressure on the parasite, which is in place for the past half a century, might have contributed for the high genetic heterogeneity its strains/populations in the country. The route of entry of the parasite into Indian sub-continent possibly appeared to be from an ancient origin from the countries of the Southeast Asian archipelago, through the eastern coastal line of the southern peninsula.