Protection against L 3 induced Brugia malayi infection in Mastomys coucha pre-immunized with BmAFII fraction of the filarial adult worm

Abstract

The present study was aimed at investigating protective efficacy of BmAFII (Sephadex G-200 eluted fraction of Brugia malayi adult worm extract) against establishment of infective larvae (L 3)-induced B. malayi infection in Mastomys coucha and to delineate immunological responses induced in the host. Healthy male M. coucha were immunized with BmAFII and subsequently inoculated with B. malayi L 3. Specific IgG and cell mediated immune responses (cellular proliferation) including release of tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), transforming growth factor-β (TGF-β) and nitric oxide (NO) from host's cells stimulated with BmAFII or lipopolysaccharide (LPS)/concanavalin A (Con A) in vitro were determined. Immunization with BmAFII reduced the adult worm recovery by 85.7% ( P < 0.001) and microfilaraemia by 77–95% of unimmunized controls ( P < 0.05–0.01). Immunization alone resulted in downregulation of responses of cellular proliferation, IFN-γ, TNF-α and NO production ( P < 0.01) but increased TGF-β release ( P < 0.001) whereas the converse was seen after L 3 inoculation in these animals. In unimmunized + L 3 inoculated animals all the above parameters were found downregulated ( P < 0.01–0.001). The cell proliferative response of BmAFII immunized + L 3 challenged animals was larger for Con A ( P < 0.001) but not for BmAFII. Specific IgG levels were higher in immunized, immunized + L 3 inoculated and unimmunized + L 3 inoculated groups ( P < 0.001) compared to unimmunized animals, the highest level being shown by immunized + L 3 inoculated group. In conclusion, immunization with BmAFII suppresses establishment of L 3-induced infection in M. coucha by stimulating proinflammatory responses to L 3.