Novel pathway for induction of latent virus from resting CD4(+) T cells in the simian immunodeficiency virus/macaque model of human immunodeficiency virus type 1 latency

Although combination therapy allows the suppression of human immunodeficiency virus type 1 (HIV-1) viremia to undetectable levels, eradication has not been achieved because the virus persists in cellular reservoirs, particularly the latent reservoir in resting CD4(+) T lymphocytes. We previously established a simian immunodeficiency virus (SIV)/macaque model to study latency. We describe here a novel mechanism for the induction of SIV from latently infected resting CD4(+) T cells. Several human cell lines including CEMx174 and Epstein-Barr virus-transformed human B-lymphoblastoid cell lines mediated contact-dependent activation of resting macaque T cells and induction of latent SIV. Antibody-blocking assays showed that interactions between the costimulatory molecule CD2 and its ligand CD58 were involved, whereas soluble factors and interactions between T-cell receptors and major histocompatibility complex class II were not. Combinations of specific antibodies to CD2 also induced T-cell activation and virus induction in human resting CD4(+) T cells carrying latent HIV-1. This is the first demonstration that costimulatory signals can induce latent virus without the coengagement of the T-cell receptor, and this study might provide insights into potential pathways to target latent HIV-1.     

Human immunodeficiency virus type 1 (HIV-1) antigen secretion by latently infected resting CD4+ T lymphocytes from HIV-1-infected individuals

In resting CD4(+) T lymphocytes harboring human immunodeficiency virus type 1 (HIV-1), replication-competent virus persists in patients responding to highly active antiretroviral therapy (HAART). This small latent reservoir represents between 10(3) and 10(7) cells per patient. However, the efficiency of HIV-1 DNA-positive resting CD4(+) T cells in converting to HIV-1-antigen-secreting cells (HIV-1-Ag-SCs) after in vitro CD4(+)-T-cell polyclonal stimulation has not been satisfactorily evaluated. By using an HIV-1-antigen enzyme-linked immunospot assay, 8 HIV-1-Ag-SCs per 10(6) CD4(+) resting T cells were quantified in 25 patients with a plasma viral load of <20 copies/ml, whereas 379 were enumerated in 10 viremic patients. In parallel, 369 and 1,238 copies of HIV-1 DNA per 10(6) CD4(+) T cells were enumerated in the two groups of patients, respectively. Only a minority of latently HIV-1 DNA-infected CD4(+) T cells could be stimulated in vitro to become HIV-1-Ag-SCs, particularly in aviremic patients. The difference between the number of HIV-1 immunospots in viremic versus aviremic patients could be explained by HIV-1 unintegrated viral DNA that gave additional HIV-1-Ag-SCs after in vitro CD4(+)-T-cell polyclonal stimulation. The ELISPOT approach to targeting the HIV-1-Ag-SCs could be a useful method for identifying latently HIV-1-infected CD4(+) T cells carrying replication-competent HIV-1 in patients responding to HAART.     

Human immunodeficiency virus type 1 can establish latent infection in resting CD4+ T cells in the absence of activating stimuli

Resting CD4(+) T cells are the best-defined reservoir of latent human immunodeficiency virus type 1 (HIV-1) infection, but how the reservoir is formed is unclear. Understanding how the reservoir of latently infected cells forms is critical because it is a major barrier to curing HIV infection. The system described here may provide an in vitro model of latent HIV-1 infection in resting CD4(+) T cells. We demonstrated that HIV-1 integrates into the genomes of in vitro-inoculated resting CD4(+) T cells that have not received activating stimuli and have not entered cell cycle stage G(1b). A percentage of the resting CD4(+) T cells that contain integrated DNA produce virus upon stimulation, i.e., are latently infected. Our results show that latent HIV-1 infection occurs in unstimulated resting CD4(+) T cells and suggest a new route for HIV-1 reservoir formation.