Macrophage Tropism and Cytopathicity of HIV-1 Variants Isolated Sequentially from a Long-Term Survivor Infected with nef-Deleted Virus

Abstract

Long-term survival of human immunodeficiency virus type 1 (HIV-1) infection has been noted in rare cohorts of individuals infected with nef-deleted virus. Enhanced macrophage tropism and cytopathicity contribute to pathogenicity of wild type HIV-1. To better understand the pathogenesis of nef-deleted HIV-1, we analyzed the replication capacity and macrophage cytopathicity of nef-deleted HIV-1 isolated sequentially from a long-term survivor during progression to AIDS (n=6 isolates). Compared with controls, all nef-deleted viruses replicated to low levels in peripheral blood mononu-clear cells and monocyte-derived macrophages (MDM). One nef-deleted virus that was isolated on the development of AIDS caused high levels of syncytia in MDM similar to control viruses, but five viruses isolated from earlier times prior to AIDS onset caused only minimal cytopathicity. Together, these results suggest that enhanced cytopathicity of nef-deleted HIV-1 for MDM can occur independently of replication capacity, and may contribute to the pathogenesis of nef-deleted HIV-1 infection.

Fig. (1). Replication kinetics in PBMC

PBMC were infected with equivalent amounts of each virus, as described in Materials and Methodology, and cultured for 28 days. Mock infected cells were treated with culture medium alone. Virus production in culture supernatants was measured by RT assays. Values shown are means from duplicate infections. Error bars represent standard deviations. Results are representative of two independent experiments using cells obtained from different donors, which gave similar results.

Fig. (2). Replication kinetics in MDM

MDM were infected with equivalent amounts of each virus, as described in Materials and Methodology, and cultured for 28 days. Mock infected cells were treated with culture medium alone. Virus production in culture supernatants was measured by RT assays. Values shown are means from duplicate infections. Error bars represent standard deviations. Results are representative of two independent experiments using cells obtained from different donors, which gave similar results.

Fig. (3). Syncytium formation in MDM induced by nef-deleted viruses

MDM were infected with equivalent amounts of each virus, as described in Materials and Methodology. Mock-infected MDM were treated with culture medium alone. Syncytia formation was documented at day 11 (ADA), 14 (89.6) or 18 (D36 viruses) post-infection. Syncytia were counted manually and scored as +/-, occasional syncytia; +, low frequency of syncytia, occurring in <5% of cells; ++, moderate frequency of syncytia, occurring in 5 to 50% of cells; or +++, extensive syncytia, occurring in >50% of cells, as described previously [37]. Results are representative of two independent experiments using cells obtained from different donors, which gave similar results. Photographs are at a final magnification of x400.