TH0-LIKE CD4(-CELLS PROTECT MICE WITH MURINE RETROVIRUS-INDUCED IMMUNODEFICIENCY SYNDROME (MAIDS) AGAINST COINFECTION WITH LISTERIA-MONOCYTOGENES() T)

We examined the host defence mechanism against infection with Listeria monocytogenes, a facultative intracellular bacterium, in mice with mu rine acquired immunodeficiency syndrome (MAIDS) caused by LP-BM5 murin e leukaemia virus (MuLv) infection. Although LP-BM5 MuLV infection in C57BL/6 mice leads to a stage of immunodeficiency characterized by sev ere compromise of cell-mediated immunity, the mice with established MA IDS infected with LP-BM5 8 weeks previously, showed resistance to an i ntraperitoneal infection with Listeria monocytogenes. These MAIDS mice also showed resistance to a lethal dose of secondary listerial challe nge, while the delayed-type hypersensitivity response to heat-killed L isteria (HKL) was severely impaired in MAIDS mice. The resistance of M AIDS mice to listerial infection was mediated by CD4(+) alpha beta T c ells but neither by gamma delta T cells nor natural killer (NK) cells. Interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) were produced by CD4(+) T cells from Listeria-infected MAIDS mice in response to th e in vitro stimulation with HKL, whereas IFN-gamma but not IL-10 were produced by those from Listeria-infected control mice. These results s uggest that T-helper 0 (Th0)-like immune responses of CD4(+) T cells o ccur and participate in host defence mechanisms against listerial infe ction in MAIDS mice.