PROTECTIVE RECONSTITUTION OF THE SCID MOUSE AGAINST REACTIVATION OF TOXOPLASMIC ENCEPHALITIS

A SCID mouse model of toxoplasmic encephalitis (TE) is described. Immu nologic reconstitution using splenocytes from Toxoplasma gondii-immune allogeneic or nonimmune syngeneic donors was not successful in preven ting reactivation of TE in chronically infected SCID mice. Splenocytes from immune syngeneic donors successfully prevented reactivation. Flo w cytometry of spleens of transplanted mice demonstrated only transien t reconstitution with allogeneic cells, but syngeneic lymphocytes exhi bited prolonged engraftment. Reconstitution with syngeneic cells allow ed enhanced production of T. gondii-specific antibody. In vitro deplet ion of CD4(+) and CD8(+) lymphocytes from BALB/c splenocytes before tr ansplantation into infected SCID mice resulted in survival inferior to that of fully reconstituted SCID mice. Depletion of CD4(+) or CD8(+) cells before transplantation did not result in mortality, but transfer of CD4(+)-depleted splenocytes resulted in histologic evidence of rea ctivation of TE, whereas transfer of CD8(+)-depleted cells did not. Th is model could be used for study of the pathogenesis of TE and applied to the evaluation of therapies for TE in immunocompromised hosts.