Disseminated histoplasmosis in a SIV-infected rhesus monkey

Disseminated histoplasmosis due to Histoplasma capsulatum was diagnosed in a rhesus monkey inoculated with simian immunodeficiency virus (SIV). Immunohistochemical staining of tissues for viral core antigens revealed that those macrophages that expressed viral antigen contained few or no fungal organisms, while those that were filled with fungal organisms did not express viral antigen. This is a previously undocumented condition in a SIV-infected macaque, and suggests that SIV infection of individual macrophages is not the cause of macrophage dysfunction in SIV infections.