STUDIES OF THE SUSCEPTIBILITY OF NUDE, CD4 KNOCKOUT, AND SCID MUTANT MICE TO THE DISEASE INDUCED BY THE MURINE AIDS DEFECTIVE VIRUS

Murine AIDS (MAIDS) is induced by a defective retrovirus that infects lymphocyte cells of the B lineage. To determine whether functional T c ells are required for the infection of B cells, T-cell-deficient mice (nude, CD4 knockout, and SCID) were infected with helper-free stocks o f the MAIDS defective virus. Infection of B cells was monitored by Nor thern blot analysis and in situ hybridization. The C57BL/6 nude mice c ontained clusters of infected B cells, but less so than did the euthym ic mice. In contrast, the (C57BL/6 x BALB/c)F-1 nude mice harbored mor e infected B cells than did their euthymic littermates when maintained in a pathogen-free environment. Clusters of infected B cells were als o detected in the MAIDS virus-infected CD4(-/-) knockout mice despite the total absence of CD4(+) T cells in these mice. However, infected c ells were not detected in SCID mice (deficient in mature T and B cells ) inoculated with the same virus, indicating that precursor B cells ar e not a target of the virus in the absence of mature CD4(+) T cells. T hese data confirm that the primary event in the development of MAIDS i s the infection of relatively mature peripheral B cells and that CD4() T cells are required to promote the expansion of these infected B ce lls.