Studies on immunosuppression indued by Measles Virus

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Peripheral blood mononuclear cells (PBMC) and T lymphocytes were infected with measles virus (MV) and cultured with a protein kinase C (PKC) activator, phorbol 12-myristate 13-acetate (PMA) and a calcium ionophore, ionomycin. After stimulation, cell viability and incorporation of BrdU were decreased in MV-infected cells compared to mock-infected cells. DNA content analysis and terminal deoxytransferase (TdT)-mediated dUTP nick end labeling demonstrated that the hypodiploid fraction and DNA fragmentation were increased in MV-infected, T lymphocytes activated with PMA plus ionomycin. These data suggest that MV induces apoptotic cell death in cells activated by PMA plus ionomycin. In contrast to stimulation with PMA plus ionomycin, mitogenic stimulation with phytohaemagglutinin (PHA) did not induce apoptotic cell death in MV-infected cells, although cell proliferation was suppressed. Apoptosis induced in stimulated. MV-infected cells may be one mechanism of immunosuppression.We investigated the changes in intracellular cytokine levels in different lymphocyte populations induced by measles virus (MV). MV-infected and uninfected peripheral blood mononuclear cells were cultured with phorbol 2-myristate 13-acetate (PMA) plus ionomycin in the presence of monensin for 10h. Surface antigen and intracellular cytokines, interleukin (IL)-2, interferon (IFN)-gamma, and IL-4, were stained simultaneously and analyzed by flow cytometry. The percentage of cells that expressed IL-2 and IFN-gamma was significantly increased in MV-infected CD3+, CD4+, CD8+ lymphocytes as compared with uninfected lymphocytes. IL-2 was increased mainly in MV-infected CD4+ lymphocytes, whereas IFN-gamma was increased mainly in MV-infected CD8+ lymphocytes and gammadelta T lymphocytes. Expression of IL-4 was unaffected by MV infection. These results demonstrate that MV enhances the intracellular levels of type 1 cytokines during the acute phase of measles.