DIRECTIONAL BUDDING OF HUMAN-IMMUNODEFICIENCY-VIRUS FROM MONOCYTES

Time-lapse cinematography revealed that activated human immunodeficien cy virus (HIV)-infected monocytes crawl along surfaces, putting forwar d a leading pseudopod, Scanning electron micrographs showed monocyte p seudopods associated with spherical structures the size of HIV virions , and transmission electron micrographs revealed HIV virions budding f rom pseudopods. Filamentous actin (F-actin) was localized by electron microscopy in the pseudopod by heavy meromyosin decoration. Colocaliza tion of F-actin and p24 viral antigen by light microscopy immunofluore scence indicated that F-actin and virus were present on the same pseud opod, These observations indicate that monocytes produce virus from a leading pseudopod. We suggest that HIV secretion at the leading edges of donor monocytes/macrophages may be an efficient way for HIV to infe ct target cells.