Trypanosoma congolense: Prophylactic Potentials Of Antiserum And Adjuvant In Experimental Mice

Abstract

Trypanosomiasis, a protozoan disease affecting livestock and transmitted by Glossina (tsetse) flies is a major constraint to livestock production in Sub-Saharan Africa. Approaches towards developing an anti-trypanosomal vaccine have so far shown little success. This study is targeted towards assessing the prophylactic potential of a “trypanotolerant” rabbit anti-serum vaccine in the presence or absence of an adjuvant (peanut oil) in the course of Trypanosoma congolense infection in mice. Forty healthy female Swiss albino mice were grouped in eight (n=5) as follows: unimmunized uninfected, serumimmunized uninfected, adjuvant-immunized uninfected, serum-adjuvant immunized uninfected, unimmunized infected, serum-immunized infected, adjuvant-immunized infected, serum-adjuvant immunized infected. For the first immunization, 200 μg of crude rabbit antiserum emulsified in a 100μl of phosphate-buffered saline (PBS) and adjuvant (1:1) or 200 μg of crude rabbit antiserum was injected intramuscularly on day 0. Similarly, the mice were administered a booster of half the crude antiserum (100 μg) every two weeks three consecutive times. Each mouse in the infected groups received 200μl of infective donor mouse blood containing 1x106 Trypanosomes per ml of blood on day 42 post immunization. Blood samples were collected daily for parasitemia determination and on days 0, 42 and 62 post immunization for hematological parameters determination. The pre-patent periods, body weight changes and survival times were assessed as well. Immunization with the rabbit antiserum (emulsified with or without the adjuvant) resulted in significantly (P<0.05) lowered mean parasitemia levels. However, significant (P<0.05) increases were observed in the mean pre-patent periods, body weights, survival times, red blood cell counts and differential white blood cell counts in the serum and serum-adjuvant immunized groups. Results from this study have shown some promising effectiveness of antiserum prophylaxis when used alongside an adjuvant (peanut oil) during the course of Trypanosoma congolense infection in experimental mice.

Keywords: Trypanosoma congolense, Adjuvant, Anti-serum, Immunization, PCR