IL-12 promotes enhanced recovery from vesicular stomatitis virus infection of the central nervous system.

To investigate the role of a cytokine in host defense against the vesicular stomatitis virus (VSV) infection of the central nervous system (CNS), IL-12 was injected i.p. into groups of 10 BALB/c mice on days -1, 0, 1, 2, and 3 postinfection. Four days postinfection, mice were examined. IL-12 strongly enhanced immunity to VSV infection in the CNS as demonstrated by 1) decreased VSV titers in brain homogenate of IL-12-injected mice compared with those of controls; 2) increased expression of inducible nitric oxide synthase in the CNS; 3) enhanced expression of both MHC class I and class II Ags in the CNS; 4) increased T cell infiltration in the CNS, especially in the olfactory bulb; and 5) diminished VSV-induced apoptosis in olfactory bulb. No detrimental effect was observed even with the 200 ng/mouse dose of IL-12. Protective effects of IL-12 were dose dependent. Collectively, these results demonstrate that exogenously added IL-12, even when injected peripherally, significantly enhances recovery from VSV infection of the CNS.