Rhesus Cytomegalovirus (Macacine Herpesvirus 3)–Associated Facial Neuritis in Simian Immunodeficiency Virus–Infected Rhesus Macaques (Macaca mulatta)

Peripheral neuropathies are common sequelae to human immunodeficiency virus (HIV) infection in humans and are due to a variety of mechanisms, including direct antiretroviral toxicity, HIV-mediated damage, immune-mediated disorders, and opportunistic viral infections. Rhesus macaques (Macaca mulatta) infected with simian immunodeficiency virus (SIV) remain the most consistent animal model for unraveling the pathogenesis of lentiviral-associated disease and its associated opportunistic infections. Rhesus cytomegalovirus (RhCMV) is the most common opportunistic viral infection in rhesus macaques infected with SIV and causes multiorgan pathology; however, its role in peripheral nerve pathology has not been explored. We have identified 115 coinfected cases with SIV and RhCMV, of which 10 cases of RhCMV-associated facial neuritis were found (8.7% prevalence). Histologic lesions were consistent in all cases and ranged from partial to complete obliteration of the nerves of the tongue, lacrimal gland, and other facial tissues with a mixed inflammatory population of neutrophils and macrophages, of which the latter commonly contained intranuclear inclusion bodies. Luxol fast blue staining and myelin basic protein immunohistochemistry confirmed the progressive myelin loss in the peripheral nerves. Bielschowsky silver stain revealed progressive loss of axons directly related to the severity of inflammation. Double immunohistochemistry with spectral imaging analysis revealed RhCMV-infected macrophages directly associated with the neuritis, and there was no evidence to support RhCMV infection of Schwann cells. These results suggest that peripheral nerve damage is a bystander effect secondary to inflammation rather than a direct infection of Schwann cells and warrants further investigations into the pathogenesis of RhCMV-induced peripheral neuropathy.