Macrophage-Derived Simian Immunodeficiency Virus Exhibits Enhanced Infectivity by Comparison with T-Cell-Derived Virus

Abstract

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infect and productively replicate in macrophages and T lymphocytes. Here, we show that SIV virions derived from macrophages have higher levels of infectivity than those derived from T cells. The lower infectivity of T-cell-derived viruses is influenced by the quantity or type of mannose residues on the virion. Our results demonstrate that the cellular origin of a virus is a major factor in viral infectivity. Cell-type-specific factors in viral infectivity, and organ-specific or disease stage-specific differences in cellular derivation of virions, can be critical in the pathogenesis of HIV and AIDS. CD4ϩ T cells and macrophages are the major targets and sources of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV). In view of the essential but highly distinct roles these cell types play in the pathogenesis of HIV (7,9,14,22), understanding how viral production in each of these cell types affects the subsequent activity of virions is important for understanding the development of disease. To determine if different factors to which virions are exposed during their generation can influence their infectivity, we generated SIV stocks from both macrophages and T cells.Two molecular clones of SIV, SIVmac316 (17) and SIVmac129 (6), were used to generate viral stocks from both macrophages and T cells. These SIV stocks (herein referred to as matching viral stocks) were derived from infection of primary rhesus monocytederived macrophages (MDM) or primary rhesus T cells. Primary MDM were derived from freshly isolated rhesus peripheral blood mononuclear cells by immunomagnetic CD11b selection and differentiated by adherence for 6 days in the presence of macrophage colony-stimulating factor (10 ng/ml). The remaining peripheral blood mononuclear cells were then subjected to CD8 immunomagnetic depletion to yield CD4 ϩ enriched cells for the primary T-cell cultures and then stimulated with phytohemagglutinin (5 g/ml) and interleukin 2 (10 ng/ml) for 3 days. Following stimulation, T cells were cultured in the presence of interleukin 2 alone for 3 additional days.Both MDM and T cells were inoculated with SIV after 6 days in culture, and cell-free supernatants from each cell type were collected daily for 8 days after SIV inoculation and stored at Ϫ80°C. Stocks were then pooled and either aliquoted and frozen or purified by ultracentrifugation over a 20% sucrose cushion to eliminate contaminating cell-derived factors such as cytokines and then aliquoted and stored at Ϫ80°C. Stocks from macrophages and T cells were collected, stored, and processed simultaneously to avoid preparation related differences in infectivity. Viral stocks were generated from a total of 12 different rhesus donors; only macrophage and T-cell stocks derived from cells isolated from a single donor at the same time were used for comparison. SIV stocks were quantified by both enzyme-linked immunosorbent assay (ELISA) for p27 Gag (Beckman-Coulter) and branched-DNA assa...

Ex vivo analysis of SIV‐infected cells by flow cytometry

“…To enrich for SIV-infected cells we removed B-cells, NK cells, and CD8 + T cells, since they are rarely infected with SIV. Additionally, we removed macrophages from our lymphocyte preparations even though they may be productively infected by SIV (14,15). The rationale for removing macrophages was: (a) flow cytometric detection does not allow distinction between ingested viral particles and actively produced virus; (b) replicating SIV might not downregulate the expression of CD4, MHC-II, or MHC-I antigens (our unpublished observation from in vitro experiments) on macrophages thereby eliminating the possibility of differentiating infected macrophages from macrophages that merely ingested viral particles.…”

Gag- and Nef-specific CD4+T cells recognize and inhibit SIV replication in infected macrophages early after infection

“…Macrophages also contribute to the latent reservoir of virus by archiving infectious virions for extended periods of time (29). Furthermore, virus produced from infected macrophages is more infectious than virus produced in CD4 ϩ T cells because of a lower number of mannose residues on macrophage-derived virions (30). Thus, the ability of CD4 ϩ T cells to suppress viral replication in macrophages is likely an important antiviral feature of these cells.…”

Fitness Disadvantage of Transitional Intermediates Contributes to Dynamic Change in the Infecting-Virus Population during Coreceptor Switch in R5 Simian/Human Immunodeficiency Virus-Infected Macaques

“…Furthermore, while CD4 ϩ T cells account for Ͼ90% of the viral load during early virus infection, macrophages may contribute substantially to plasma viral load during late-stage infection (19,29,32,40). On a per-cell basis, productively infected macrophages cumulatively release at least 10-fold more viruses than do productively infected T cells (18), and macrophages generate virions with greater levels of infectivity than T cells (21). Moreover, they are the primary virus-producing cells following the nearly complete depletion of CD4 ϩ target T cells in SIVinfected rapid progressors (6).…”