Free Living Nematode Rhabditis as Helminth Vaccine Against Toxocar Vitulorum

Abstract

Free living nematode Rhabditis axei were cultured on blood agar at 37oC and 70-80% humidity, soil samples obtained from canal channels and cultivated fields were found positive for Rhabditis axei. Supplementation of 2-3 grams of glucose in the culturing media significantly enhanced the growth of the Rhabditis axei. Sub-culturing of the Rhabditis axei was maintained up to 42 generations, by transferring into fresh blood agar media. Sterile hatching Toxocara vitulorum larvae was accomplished in 0.5% formalin, incubated at 28oC for 18 days. Crude, protein sub-unit and lipopolysaccharide sub-unit vaccines were prepared with and without Freund’s complete adjuvant. The evaluation of the vaccines was determined on the basis of humoral, cellular and challenge responses in a rabbit model. No significant difference (P<0.01) in the humoral response was found among the whole larvae pellet (WLP) and whole larvae supernatant (WLS) with and without Freund’s complete adjuvant compared to control. There was a highly significant difference (P<0.01) among lipopolysaccharides sub-unit (LPS) and protein sub-unit (PS) with and without adjuvant compared to control. The best response was produced by LPS followed by PS, WLS, and WLP. A similar cellular response was observed vise the LPS being the best followed by PS, WLS and WLP. There was no significant difference (P<0.01) in the response induced by the vaccines with and without Freund’s complete adjuvant. Challenge infection with 20000 L3 of Toxocara vitulorum indicated that all the vaccine were effective against Toxocara Vitulorum with variable level of protection being lower to higher from crude to submit vaccines.