Impaired IL-15 production associated with susceptibility of murine AIDS to mycobacterial infection

LP‐BM5 murine leukemia virus (MuLV) injection causes murine AIDS (MAIDS), a disease characterized by many functional abnormalities of immunocompetent cells. We show that MAIDS mice are susceptible to Mycobacterium bovis Bacille Calmette‐Guérin (BCG) infection as assessed by survival rate and bacterial counts. The peritoneal exudate macrophages from MAIDS mice produced a significant level of interleukin (IL)‐12 soon after inoculation with BCG, whereas IL‐15 and tumor necrosis factor (TNF) production were severely impaired in BCG‐infected MAIDS mice. The appearance of natural killer (NK) and CD4+ T helper type 1 (Th1) cells specific for mycobacterial antigen were depressed in MAIDS mice after BCG infection. Thus, it appeared that impaired production of IL‐15, besides other inflammatory cytokines, in MAIDS mice may be involved in the poor responses of the NK and Th1 cells, resulting in an increased susceptibility to BCG.