[Why does the human immunodeficiency virus (HIV) invade the nervous system?]

Human Immunodeficiency Virus (HIV) has neurotropic effects that are independent of the well-known lymphotropism. They have been proved by various techniques, but their pathogenesis is not clear. It is remarkable that the neuropathological features do not correlate with the degree of the clinical symptomatology. HIV antigens and antibodies are demonstrable within the central nervous system by immunological tests. The macrophages transport the virus across the blood-brain barrier and are responsible for its persistence in that location. Different cell types, especially of the subcortical areas, have HIV-receptive CD4 molecules. These markers may be identical with the receptors for endogenous neuropeptides and it is likely that viral proteins are causing a competitive inhibition of these mostly neurotrophic factors. This interference is discussed as one of the main reasons of HIV dementia.