Effects of immunosuppression on West Nile virus infection in hamsters.

A research study, comparing the pathogenesis of experimental West Nile virus (WNV) infection in immunocompetent and immunosuppressed golden hamsters, is described. Cyclophosphamide was used to immunosuppress the animals. The immunosuppressed hamsters had a prolonged period of viremia, depressed humoral immune response, more extensive and severe pathology, and higher fatality rate than the untreated immunocompetent animals. Histopathological and immunohistochemical studies of tissues from the two groups showed that pathologic changes in the untreated infected animals were confined to the brain and spinal cord, whereas the histopathological changes and WNV antigen distribution in the immunosuppressed animals were much more extensive and diffuse, involving the adrenal, kidney, heart and lung, and brain and spinal cord. Results of this study in the hamster model provide insight into the increased severity of WNV infection observed in immunosuppressed people.