Distinct biological and serological properties of human immunodeficiency viruses from the brain.

Human immunodeficiency viruses from the brain can be distinguished from peripheral blood isolates by their ability to infect established human cell lines and their sensitivity to serum neutralization. Isolates from the brain and lymph nodes obtained from the same person displayed similar host range tropism and susceptibility to serum neutralization; however, the brain isolate infected macrophages more efficiently. These data suggest that brain isolates may represent a distinct subtype of the human immunodeficiency virus.