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Journal of Immunology and Immunopathology
Year : 2002, Volume : 4, Issue : 1&2
First page : ( 117) Last page : ( 121)
Print ISSN : 0972-0561.

Vaccine prospects in human filariasis

Misra-Bhattacharya Shailja, Gupta Ruma

Division of Parasitology, Central Drug Research Institute, P.B. 173, Lucknow - 226001, India.

Abstract

Lymphatic filariasis a major tropical disease caused by mosquito borne-nematode parasites persists as a major cause of morbidity and significant impediment to socioeconomic development. In absence of an effective macrofilaricide, control of infection by immunological means appear logical. The pursuit of anti filarial vaccine is complicated by the phenomenon of inmmnoslippression, immunologically induced pathology and strict primate host -specificity of target human filarids Wuchereria bancrofti and Onchocerca volvulus. Crude somatic products derived from different life stages and species of filariids have mostly been used in the past with limited success. However, partially purified antigens were found to exert superior protective efficacy. Excretory-secretory antigens have been considered to be highly immunogenic. Irradiated infective larvae have been demonstrated to offer strong resistance to subsequent larval exposures in a variety of filariid species. Microfilarial extracts (25, 70–75 and 110 kDa) could produce only stage-specific protection. However, our results demonstrated the extension of protective efficacy against larval establishment also, if immunization was carried out in already infected animals (Chatterjee et al., 1992). Our studies also revealed that low molecular weight antigens developed better resistance than high molecular weight antigens in addition to induction of T-cell response (Misra et al., 1994; Dikshit et al., 1995). Endemic normal individuals apparently free from filarial infection demonstrate hyperimmune response to most parasite antigens and represent an interesting group to work on protective molecules. 43 kDa molecule of Brugia infective larvae was recognized by 100% of the endemic normal sera but not micro filaraemics indicating its importance as a candidate prophylactic antigen. Cloning of few peptides and enzymes including antioxidants and their further immunoprophylactic evaluation led to development of either mf-specific or low grade protection. A cocktail of these recombinants has not yet been evaluated. Targeted vaccine approaches might help in blocking parasite morphogenesis, migration, reproduction or in targeting an enzyme highly essential for physiological function of parasite.

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Key words

Filaria, vaccine, immunoprophylaxis, protective antigens, immunogens, immunity, immunization.

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