Cytoplasmic assembly and accumulation of human immunodeficiency virus types 1 and 2 in recombinant human colony-stimulating factor-1-treated human monocytes: an ultrastructural study

Abstract

Recombinant human colony-stimulating factor-i-treated human peripheral blood-derived monocytes-macrophages are efficient host cells for recovery of the human immunodeficiency virus (HIV) from blood leukocytes of patients with acquired immunodeficiency syndrome. These cells can be maintained as viable monolayers for intervals exceeding 3 months. Infection with HIV resulted in virus-induced cytopathic effects, accompanied by relatively high levels of released progeny virus, followed by a prolonged low-level release of virus from morphologically normal cells. In both acutely and chronically infected monocytes, viral particles were seen budding into and accumulating within cytoplasmic vacuoles. The number of intravacuolar virions far exceeded those associated with the plasma membrane, especially in the chronic phase, and were concentrated in the perinuclear Golgi zone. In many instances, the vacuoles were identified as Golgi elements. Fusion of virus-laden vacuoles with primary lysosomes was rare. The pattern of cytoplasmic assembly of virus was observed with both HIV types 1 and 2 and in brain macrophages of an individual with acquired immunodeficiency syndrome encephalopathy. Immunoglobulin-coated gold beads added to acutely infected cultures were segregated from the vacuoles containing virus; relatively few beads and viral particles colocalized. The assembly of HIV virions within vacuoles of macrophages is in contrast to the exclusive surface assembly of HIV by T lymphocytes. Intracytoplasmic virus hidden from immune surveillance in monocytes-macrophages may explain, in part, the persistence of HIV in the infected human host.

β2 Integrin Adhesion Complexes Maintain the Integrity of HIV‐1 Assembly Compartments in Primary Macrophages

“…Indeed, studies tracing the assembly of HIV-1 Gag virus-like particles in Gag-GFP model systems, which tend to involve transfection of 6-7-day-old MDM and analysis within 6-24 h, have documented significant particle assembly at the cell surface with comparatively little budding at intracellular sites (7,27); IPMC are not well developed at this age. In contrast, experiments with infected macrophages are often analysed at later times, after around 2 weeks in culture, when intracellular accumulations of HIV become predominant (3,5,6,(8)(9)(10)14). In our studies, virus particles were only rarely detected at the cell surface and almost all HIV budding profiles and immature virions were seen in the IPMC.…”

“…Virus-containing IPMC have been observed in a number of different MDM preparations (3,5,6,(8)(9)(10)14), and the appearance of these structures appears to be largely independent of the method by which the cells are isolated or by culture conditions such as serum, growth factor treatments or the surfaces that the cells are cultured on. Furthermore, HIV has been shown to be present in intracellular compartments in macrophages in vivo, e.g.…”

Marked differences in the structures and protein associations of lymphocyte and monocyte CD4: Resolution of a novel CD4 isoform

“…51 Cell-specific differences are also notable, as in lymphocytes HIV-1 buds from the cell surface, but in macrophages is released into intracellular exosomal vacuoles. 52,53 As there are differences in the lipid compositions of plasma and exosomal membranes, 54 and in the lipid-raft compositions between lymphocytes and monocytes, 44 it is anticipated that HIV-1 envelopes derived from lymphocytes and H9), primary monocyte-derived macrophages and monocytic cell lines (U937, THP1). RT-PCR and electrophoresis was performed as described in the Materials and methods.…”

Human Immunodeficiency Virus Type 1-Associated Cd4 Downmodulation

“…In addition, infection by Vpu-particles caused more cytotoxicity and syncytium formation than that associated with Vpu+ viruses (Klimkait et al, 1990;Strebel et al, 1988Strebel et al, ,1989Terwilliger et al, 1989;Yao et al, 1992). Transmission electron microscopy revealed both greater numbers of plasma membrane-associated virus and viral budding into cytoplasmic vacuoles in the case of Vpu-viruses (Klimkait et al, 19901, a finding similar to the intracytoplasmic accumulation of viral particles seen in HIV-infected macrophages (Orenstein et al, 1988). This effect of Vpu on virion release is independent of both envelope glycoprotein and CD4 expression (Yao et al, 1992) and suggests that Vpu may facilitate either rates of viral assembly or release.…”