Highly productive infection with pseudotyped human immunodeficiency virus type 1 (HIV-1) indicates no intracellular restrictions to HIV-1 replicationin primary human astrocytes

Human astrocytes can be infected with human immunodeficiency virus type I ( HIV-1) in vitro and in vivo, but, in contrast to T lymphocytes and macropha ges, virus expression is inefficient. To investigate the HIV-1 life cycle i n human fetal astrocytes, we infected cells with HIV-1 pseudotyped with env elope glycoproteins of either amphotropic murine leukemia virus or vesicula r stomatitis virus. Infection by both pseudotypes was productive and long l asting and reached a peak of 68% infected cells and 1.7 mug of viral p24 pe r ml of culture supernatant 7 days after virus inoculation and then continu ed with gradually declining levels of virus expression through 7 weeks of f ollow-up. This contrasted with less than 0.1% HIV-1 antigen-positive cells and 400 pg of extracellular p24 per ml at the peak of astrocyte infection w ith native HIV-1. Cell viability and growth kinetics were similar in infect ed and control cells. Northern blot analysis revealed the presence of major HIV-1 RNA species of 9, 4, and 2 kb in astrocytes exposed to pseudotyped ( but not wild-type) HIV-1 at 2, 14, and 28 days after infection. Consistent with productive infection, the 9- and 4-kb viral transcripts in astrocytes infected by pseudotyped HIV-1 were as abundant as the 2-kb mRNA during 4 we eks of follow-up, and both structural and regulatory viral proteins were de tected in infected cells by immunoblotting or cell staining. The progeny vi rus released by these cells was infectious. These results indicate that the major barrier to HIV-1 infection of primary astrocytes is at virus entry a nd that astrocytes have no intrinsic intracellular restriction to efficient HIV-1 replication.