The leucocytic and parasitaemic profiles and immune response of rats treated with retinyl palmitate before infection with Trypanosoma brucei.

The effects of oral administration of retinyl palmitate (30,000 IU/kg bodyweight) for 3 days to rats before infection with Trypanosoma brucei were investigated by examining the leucocytic and parasitaemic profiles, and the antibody response to sheep red blood cells. The pretreatment significantly (P<0.01) improved the leucocytic profile (especially the absolute lymphocyte count) from day 7 post-infection to the time of death. It also significantly delayed the onset of parasitaemia (i.e., lengthened the pre-patent period) and led to reduced levels of parasitaemia throughout the period of infection. Pretreatment significantly increased the antibody response to sheep red blood cells (P<0.01) throughout the infection, even after treatment with diminazene aceturate, to levels that more than compensated for the immunosuppressive effect of the T. brucei. Further studies are warranted on the possible use of retinyl palmitate in overcoming immunosuppression associated with trypanosome infections in man and animals in endemic areas.