Abstract:Critical aspects of HIV-1 infection occur in mucosal tissues, particularly in the gut, which contains large numbers of HIV-1 target cells that are depleted early in infection. We used electron tomography (ET) to image HIV-1 in gut-associated lymphoid tissue (GALT) of HIV-1–infected humanized mice, the first three-dimensional ultrastructural examination of HIV-1 infection in vivo. Human immune cells were successfully engrafted in the mice, and following infection with HIV-1, human T cells were reduced in GALT. … Show more
“…ET corroborated the IF results, showing the presence of infected cells indicated by virus budding profiles projecting from the plasma membrane and free virions in similar tissue locations (Figure 1C,D). The localization and levels of T-cells and HIV-1 within colon crypts were consistent with our previous studies in HIV-1–infected BLT animals (Ladinsky et al, 2014), establishing the validity of the PBMC-NSG model for conducting longitudinal imaging studies of HIV-1 infection and spread in lymphoid tissues.10.7554/eLife.23282.002Figure 1.HIV-1 infection and Imaging of hu-mice.( A ) Mean blood p24 levels from three HIV-1–infected PBMC-NSG mice assessed at 0, 12, and 21 days PI. Error bars represent standard deviation.…”
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
“…ET corroborated the IF results, showing the presence of infected cells indicated by virus budding profiles projecting from the plasma membrane and free virions in similar tissue locations (Figure 1C,D). The localization and levels of T-cells and HIV-1 within colon crypts were consistent with our previous studies in HIV-1–infected BLT animals (Ladinsky et al, 2014), establishing the validity of the PBMC-NSG model for conducting longitudinal imaging studies of HIV-1 infection and spread in lymphoid tissues.10.7554/eLife.23282.002Figure 1.HIV-1 infection and Imaging of hu-mice.( A ) Mean blood p24 levels from three HIV-1–infected PBMC-NSG mice assessed at 0, 12, and 21 days PI. Error bars represent standard deviation.…”
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
Preface
The narrow membrane necks formed during viral, exosomal, and intra-endosomal budding from membranes, cytokinesis, and related processes have interiors that are contiguous with the cytosol. The severing of these necks involves action from the opposite face of the membrane as compared to the well-characterized coated vesicle pathways, and is referred to as “reverse” or “inverse” topology membrane scission. This process is carried out by the endosomal sorting complexes required for transport (ESCRT) proteins. In particular, the ESCRT-III proteins can form filaments, flat spirals, tubes and conical funnels, which are thought to somehow direct membrane remodeling and scission. Their assembly, and their disassembly by the ATPase VPS4, has been intensively studied, but the mechanism of scission has been elusive. New insights from cryo-electron microscopy and various types of spectroscopy may finally be close to rectifying this situation.
“…The first (founding) infected cells seem to be CD4 lymphocytes 114, 115 rather than macrophages. In submucosa, infected cells transmit HIV-1 to uninfected cells through a cell-to-cell specific structure called a virological synapse and through nanotubes and filopodia 116-119 .…”
Section: Seminal Free and Cell-associated Virus In The Establishment mentioning
The vast majority of new HIV infections in male-to-female transmission occurs through semen, where HIV-1 is present in two different forms: as free and as cell-associated virus. In the female lower genital tract, semen mixes with female genital secretions that contain various factors, some of which facilitate or inhibit HIV-1 transmission. Next, HIV-1 crosses the genital epithelia, reaches the regional lymph nodes, and disseminates through the female host. Cervico-vaginal mucosa contains multiple barriers, resulting in a low probability of vaginal transmission. However, in some cases HIV-1 is able to break these barriers. Although the exact mechanisms of how these barriers function remain unclear, their levels of efficiency against cell-free and cell-associated HIV-1 are different, and both cell-free and cell-associated virions seem to use different strategies to overcome these barriers. Understanding the basic mechanisms of HIV-1 vaginal transmission is required for the development of new antiviral strategies to contain HIV-1 epidemics.
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