IMMUNOSUPPRESSION IN EXPERIMENTAL TRYPANOSOMIASIS - EFFECTS OF TRYPANOSOMA-BRUCEI ON IMMUNIZATION AGAINST LOUPING-ILL VIRUS AND LYMPHOCYTIC CHORIOMENINGITIS VIRUS

The effect of chronic Trypanosoma brucei infection on the immune response of mice was studied. Following vaccination against either louping-ill virus or lymphocytic choriomeningitis (LCM) virus, groups of trypanosome-infected and control mice were challenged with homologous virus. There was a marked delay in the development of vaccine-induced protection against louping-ill virus in mice infected with trypanosomes and the proportion protected was reduced compared with control mice. Intraperitoneal (i.p.) injection of LCM virus protected all control mice against intracerebral (i.c.) inoculation when given as few as 3 days before challenge. In contrast trypanosome-infected mice were not protected when virus was given i.p. 3 days before challenge but were after 7 days. Control mice died from LCM 6 to 7 days after i.c. inoculation whereas trypanosome-infected mice succumbed between days 7 and 11. These results support the concept that T-cell responses are only diminished and the major immunosuppressive effect of trypanosomiasis is mediated through a B-cell hyporesponsiveness. © 1979.