Human immunodeficiency virus pathogenesis: insights from studies of lymphoid cells and tissues

Longitudinal imaging of HIV-1 spread in humanized mice with parallel 3D immunofluorescence and electron tomography

Dissemination of HIV-1 throughout lymphoid tissues leads to systemic virus spread following infection. We combined tissue clearing, 3D-immunofluorescence, and electron tomography (ET) to longitudinally assess early HIV-1 spread in lymphoid tissues in humanized mice. Immunofluorescence revealed peak infection density in gut at 10–12 days post-infection when blood viral loads were low. Human CD4+ T-cells and HIV-1–infected cells localized predominantly to crypts and the lower third of intestinal villi. Free virions and infected cells were not readily detectable by ET at 5-days post-infection, whereas HIV-1–infected cells surrounded by pools of free virions were present in ~10% of intestinal crypts by 10–12 days. ET of spleen revealed thousands of virions released by individual cells and discreet cytoplasmic densities near sites of prolific virus production. These studies highlight the importance of multiscale imaging of HIV-1–infected tissues and are adaptable to other animal models and human patient samples.

DOI:http://dx.doi.org/10.7554/eLife.23282.001

Antibody against integrin lymphocyte function-associated antigen 1 inhibits HIV type 1 infection in primary cells through caspase-8-mediated apoptosis

HIV-1 infection induces formation of a virological synapse wherein CD4, chemokine receptors, and cell-adhesion molecules such as lymphocyte function-associated antigen 1 (LFA-1) form localized domains on the cell surface. Studies show that LFA-1 on the surface of HIV-1 particles retains its adhesion function and enhances virus attachment to susceptible cells by binding its counterreceptor intercellular adhesion molecule 1 (ICAM-1). This virus-cell interaction augments virus infectivity by facilitating binding and entry events. In this study, we demonstrate that inhibition of the LFA-1/ICAM-1 interaction by a monoclonal antibody leads to decreased virus production and spread in association with increased apoptosis of HIV-infected primary T cells. The data indicate that the LFA-1/ICAM-1 interaction may limit apoptosis in HIV-1-infected T cells. This phenomenon appears similar to anoikis wherein epithelial cells are protected from apoptosis conferred by ligand-bound integrins. These results have implications for further understanding HIV pathogenesis and replication in peripheral compartments and lymphoid organs.

HIV medications: an update and review of metabolic complications

In the past 30 years, medical advances for those with human immunodeficiency virus (HIV) have reduced morbidity and mortality to extend life with highly active antiretroviral therapy (HAART) and with the continued development of new therapies. With this success, HIV is being managed chronically, but other health issues of an aging HIV-infected population have emerged. The challenges of treating HIV infection have shifted from AIDS-related mortality improvements to drug-induced disease from HAART, including cardiovascular disease, metabolic disorders, and bone health. Prolonged use of antiretroviral therapy maintaining immune restoration appears to represent additional, ongoing risk factors for the development of these metabolic complications. These drug-related problems continue to challenge patients and clinicians in the management of HIV disease, as well as ongoing research for drug development improvements to minimize these risks. These health risks imposed by HAART must be vigilantly monitored and aggressively addressed to improve the overall health of those treated for HIV infection.

Measles virus inhibits human immunodeficiency virus type 1 reverse transcription and replication by blocking cell-cycle progression of CD4+ T lymphocytes

Acute measles virus (MV) infection results in a decrease in plasma human immunodeficiency virus type 1 (HIV-1) RNA levels in co-infected children. An in vitro peripheral blood mononuclear cell (PBMC) culture system was used to assess the mechanisms by which MV blocks HIV-1 replication. MV inhibited proliferation of CD4(+) T lymphocytes, the target cell for HIV-1 replication. In the presence of MV, cells did not progress to G(1b) and S phases, steps critical for the completion of HIV-1 reverse transcription and productive replication. This block in cell-cycle progression was characterized by an increased proportion of CD4(+) and HIV-1-infected cells retained in the parental generation in PBMCs co-cultured with MV and HIV-1, and decreased levels of cyclins and RNA synthesis. Early HIV-1 replication was also inhibited in the presence of MV, as measured by reduced expression of a luciferase reporter gene and lower levels of both early (LTR) and late (LTR-gag) DNA intermediates of HIV-1 reverse transcription in the presence of CCR5-tropic HIV-1. The effects of MV on lymphoproliferation and p24 antigen production were reproduced by n-butyrate and hydroxyurea, drugs that block the cell cycle in G(1a) and G(1)/S, respectively. It was concluded that MV inhibits HIV-1 productive replication in part by blocking the proliferation of CD4(+) T lymphocytes.

The importance of virus-associated host ICAM-1 in human immunodeficiency virus type 1 dissemination depends on the cellular context

The primary objective of this study was to define whether the nature of virion-bound host cell membrane proteins influenced the process of human immunodeficiency virus 1 (HIV-1) capture and transmission. We pulsed cells of monocytoid lineage (established and primary) and CD4-negative epithelial cells transiently expressing DC-SIGN or LFA-1 with isogenic HIV-1 particles either devoid or bearing host-derived ICAM-1 or ICAM-3 before incubation with an indicator cell line. To our surprise, the ICAM-1/LFA-1 association was a more efficient transmission factor than the combined gp120/DC-SIGN and ICAM-3/DC-SIGN interactions. The involvement of the association between virus-bound ICAM-1 and its natural ligand LFA-1 in virus binding and carriage was confirmed when using more physiological cellular targets, i.e., human lymphoid tissues cultured ex vivo. However, the contribution of virus-anchored host ICAM-1 to the process of retention and transmission of HIV-1 could not be confirmed when using primary human cells of macrophage/dendritic lineage as transmitter cells and autologous CD4+ T lymphocytes as targets. Altogether these data underscore the complexity of factors participating in virus-cell contact and efficient dissemination of HIV-1 to target cells.

The relationship between simian immunodeficiency virus RNA levels and the mRNA levels of alpha/beta interferons (IFN-alpha/beta) and IFN-alpha/beta-inducible Mx in lymphoid tissues of rhesus macaques during acute and chronic infection

To define the role of alpha/beta interferons (IFN-alpha/beta) in simian immunodeficiency virus (SIV) infection, IFN-alpha and IFN-beta mRNA levels and mRNA levels of Mx, an antiviral effector molecule, were determined in lymphoid tissues of rhesus macaques infected with pathogenic SIV. IFN-alpha/beta responses were induced during the acute phase and persisted in various lymphoid tissues throughout the chronic phase of infection. IFN-alpha/beta responses were most consistent in tissues with high viral RNA levels; thus, IFN-alpha/beta responses were not generally associated with effective control of SIV replication. IFN-alpha/beta responses were differentially regulated in different lymphoid tissues and at different stages of infection. The most consistent IFN-alpha/beta responses in acute and chronic SIV infection were observed in peripheral lymph nodes. In the spleen, only a transient increase in IFN-alpha/beta mRNA levels during acute SIV infection was observed. Further, IFN-alpha and IFN-beta mRNA levels showed a tissue-specific expression pattern during the chronic, but not the acute, phase of infection. In the acute phase of infection, SIV RNA levels in lymphoid tissues of rhesus macaques correlated with mRNA levels of both IFN-alpha and IFN-beta, whereas during chronic SIV infection only increased IFN-alpha mRNA levels correlated with the level of virus replication in the same tissues. In lymphoid tissues of all SIV-infected monkeys, higher viral RNA levels were associated with increased Mx mRNA levels. We found no evidence that monkeys with increased Mx mRNA levels in lymphoid tissues had enhanced control of virus replication. In fact, Mx mRNA levels were associated with high viral RNA levels in lymphoid tissues of chronically infected animals.