Modification of spleen cell subsets by chronic cocaine administration and murine retrovirus infection in normal and protein-malnourished mice

Abstract

We have developed an experimental mouse model to study the effect of daily cocaine administration on the immune system during an acquired immune deficiency syndrome (AIDS). Mice were infected with LP-BM5 murine leukemia virus, a retrovirus which causes immunosuppression with the development of functional murine AIDS. Increasing doses of cocaine given by daily intraperitoneal injection for 11 weeks reduced body weight. A daily cocaine injection in some mice as well as a saline injection in others showed a decrease in the percentage of Thy 1.2 +, CD4 + and CD8 + cells, while both treatments increased the percentage and absolute numbers of B-cells per spleen. Saline and cocaine treatment induced an increase in γ-IFN and TNF-α production by splenocytes. Cocaine treatment favored a decrease in sIL-2R secretion. Saline and cocaine treatment had slightly different effects on the splenocytes of protein-malnourished mice. Cocaine treatment induced an increase in the percentage of CD8 + cells. Saline and cocaine treatments decreased the number of Mac 1 + cells in the spleen. Moreover, saline- and cocaine-treated protein-malnourished mice splenocytes did not present the increase in γ-IFN production as well-nourished mice splenocytes showed. Retrovirus-infected mice showed a decrease in the percentage of Thy 1.2 + and CD8 + cells and an increase in the percentage and absolute numbers of CD4 +, IL-2R +, Mac 1 + and B-cells. Cocaine partially prevented the enlargement of lymphoid organs due to lymphoid cell proliferation induced by murine retrovirus infection, but had little effect on the elevated percentage of CD4 + cells or B-cells or the depressed numbers of CD8 + cells associated with virus infection. However, cocaine did reduce the number of activated IL-2R + cells and macrophages (Mac 1 +) in addition to reducing the total number of cells per spleen in all subsets in retrovirus-infected mice, but not in uninfected controls. Cocaine treatment and retrovirus infection alone or in combination suppressed the release of sIL-2R into supernatant fluid during in vitro culture of splenocytes. These data illustrate that cocaine treatment modulates cell proliferation in retrovirus-infected mice and thus modifies the absolute number of cells in those subsets already altered by retrovirus infection. Retrovirus-infected and retrovirus-infected cocaine-treated protein-malnourished mice showed similar results.