Modification of Resistance to <i>Streptococcus pneumoniae</i> by Dietary Ethanol, Immunization, and Murine Retroviral Infection

Abstract

Hallmarks of the acquired immune deficiency syndrome (AIDS) are immunologic alterations, frequently associated with opportunistic infections. To study such associations, LP-BM5 murine retrovirus infection was used as a murine model of AIDS. Retrovirally infected and uninfected mice were fed a 5% (v/v) ethanol diet for 55 days and then fed a 7% v/v ethanol diet for the final 7 days to assert the role of ethanol as a cofactor in development of murine AIDS. There was a reduction in polymorphonuclear neutrophils count in ethanol-fed groups. Neutrophils increased in retrovirus-infected groups, except those vaccinated 10 days before challenge with live bacteria. The percentage of splenic lymphocytes in the retrovirus-infected group was reduced in comparison with controls. Survival of the mice challenged intraperitoneally with Streptococcus pneumoniae was increased by vaccination and suppressed by dietary alcohol. Retrovirus infection caused a much faster death rate after bacterial challenge than nonretrovirus infected controls. Vaccination played an important role in delaying the death rate in all treated groups. Transferring spleen cells from healthy, unimmunized mice also enabled the retrovirally infected mice to survive the bacterial infection longer. Enhancement of resistance to S. pneumoniae by vaccination and transfer of immunocompetent cells to mice immunosuppressed by retroviral infection show the potential to use immunomodulation to affect disease resistance in AIDS.