SUSCEPTIBILITY OF SEVERE COMBINED IMMUNODEFICIENT (SCID) MICE TO TRYPANOSOMA-BRUCEI-GAMBIENSE AND T-B. RHODESIENSE

Susceptibility of severe combined immunodeficient (SCID) mice to 7 iso lates of Trypanosoma brucei gambiense and 2 isolates of T. b. rhodesie nse was examined in terms of their infectivity, course of parasitaemia , packed cell volume (PCV) and survival period in comparison with that of normal immunocompetent (BALB/c) mice. All isolates of T. b. gambie nse and T, b, rhodesiense caused high (> 1 X 10(8) parasites/ml) paras itaemia in the SCID mice, the survival periods ranged from 5 to 47 day s. On the other hand, 5 of 7 isolates of T. b. gambiense developed chr onic infection in the BALB/c mice with sporadic but persistent parasit aemia with less than 5 X 10(6) parasites/ml. All the mice tested in th is group survived more than 60 days after infection. In contrast, the 2. remaining isolates of T. b. gambiense and both isolates of T. b. rh odesiense showed high virulence in the BALB/c mice and killed all of t hem within 30 days after infection. The results demonstrate that the S CID mice, in which functional B- and T-cell-mediated immunities are co ngenitally lacking, are highly susceptible for 'low-virulence' T. b. g ambiense. This makes SCID mice useful tools for the isolation of paras ites from T. b. gambiense sleeping sickness patients and the propagati on of large amounts of such parasites.