Measles virus-induced immunosuppression in cotton rats is associated with cell cycle retardation in uninfected lymphocytes

Measles virus (MV)-induced immune suppression during acute measles often le ads to secondary viral, bacterial and parasitic infections which severely c omplicate the course of disease, Previously, we have shown that cotton rats are a good animal model to study MV-induced immune suppression, where prol iferation inhibition after ex vivo stimulation of cotton rat spleen cells i s induced by the viral glycoproteins (fusion and haemagglutinin proteins), We have now tested a variety of putative mechanisms of MV-induced immune su ppression in this animal model. Proliferation inhibition is not due to fusi on mediated by the MV glycoproteins and subsequent lysis of cells, Other pu tative mechanisms like classical anergy (unresponsiveness towards IL-2) or apoptosis do not seem to play a role in MV-induced immune suppression, In c ontrast, it was shown that spleen cells from infected animals preferentiall y accumulate in the G(0)/G(1) phase and progress more slowly through the ce ll cycle after mitogen stimulation in comparison to cells from nan-infected animals. These data indicate a retardation of the cell cycle which is corr elated with proliferation inhibition and might have severe consequences in mounting an effective immune response.