The importance of route of infection in determining the extent of exacerbation of listeriosis by anti-interferon-gamma monoclonal antibody.

Treating mice with a neutralizing rat monoclonal antibody (mAb) against murine interferon-gamma (IFN-gamma) prevented them from controlling an otherwise sublethal Listeria infection initiated via an extravascular route, but not via an intravenous route. In mice inoculated extravascularly, anti-IFN-gamma mAb treatment caused rapid uncontrolled growth of Listeria at the site of inoculation, and the continuous systemic dissemination of large numbers of bacteria to the liver and spleen. The infection-enhancing effects of anti-IFN-gamma treatment in mice infected intravenously was seen as an increase in the number of bacteria in the liver and spleen, but in subsequent control and eventual resolution of infection beginning 5 days after inoculation. The results serve to show that the exacerbating effect of anti-IFN-gamma treatment on murine listeriosis is greater for infections initiated at extravascular sites.