Use of a replication-defective vector to track cells initially infected by SIV in vivo: infected mononuclear cells rapidly appear in the draining lymph node after intradermal inoculation of rhesus monkeys

Human CRM1 augments production of infectious human and feline immunodeficiency viruses from murine cells

Productive replication of human immunodeficiency virus type 1 (HIV-1) occurs efficiently only in humans. The posttranscriptional stages of the HIV-1 life cycle proceed poorly in mouse cells, with a resulting defect in viral assembly and release. Previous work has shown that the presence of human chromosome 2 increases HIV-1 production in mouse cells. Recent studies have shown that human chromosome region maintenance 1 (hCRM1) stimulates Gag release from rodent cells. Here we report that expressions of hCRM1 in murine cells resulted in marked increases in the production of infectious HIV-1 and feline immunodeficiency virus (FIV). HIV-1 production was also increased by hSRp40, and a combination of hCRM1 and hSRp40 resulted in a more-than-additive effect on HIV-1 release. In contrast, the overexpression of mouse CRM1 (mCRM1) minimally affected HIV-1 and FIV production and did not antagonize hCRM1. In the presence of hCRM1 there were large increases in the amounts of released capsid, which paralleled the increases in the infectious titers. Consistent with this finding, the ratios of unspliced to spliced HIV-1 mRNAs in mouse cells expressing hCRM1 and SRp40 became similar to those of human cells. Furthermore, imaging of intron-containing FIV RNA showed that hCRM1 increased RNA export to the cytoplasm.By testing chimeras between mCRM1 and hCRM1 and comparing those sequences to feline CRM1, we mapped the functional domain to HEAT (Huntingtin, elongation factor 3, protein phosphatase 2A, and the yeast kinase TOR1) repeats 4A to 9A and a triple point mutant in repeat 9A, which showed a loss of function. Structural analysis suggested that this region of hCRM1 may serve as a binding site for viral or cellular factors to facilitate lentiviral RNA nuclear export.

Lymphocyte-dendritic cell interactions and mucosal acquisition of SIV/HIV infection

PURPOSE OF REVIEW

Several previous models of HIV dissemination implicated dendritic cells as viral conduits to the lymphatics. However, recent macaque transmission and microbicide studies have highlighted a more complex situation.

RECENT FINDINGS

Resting CD4 lymphocytes are observed to be the major infected population in mucosal tissue after vaginal challenge with SIV. Resting lymphocytes appear to bridge infection over short distances, whereas activated lymphocytes provide long-distance virus dissemination as a result of greater virus amplification. In addition, dendritic cells might be early carriers of virus, transmitting virus to T cells locally and to the lymph nodes, and thus support parallel mechanisms in transmission. Microbicide studies using agents against CCR5 corroborate a model that infection at the mucosa must occur for transmission to be successful. The fast-rate dendritic cell trafficking of virus to the lymphatics may not result in immediate and efficient viral replication in lymphatic tissue. As dendritic cells might also be infected at the mucosa before lymphatic trafficking, this would enable them to transfer virus in this region at a later timepoint.

SUMMARY

There are now several models that can be attributed to the mucosal acquisition of SIV/HIV. One feature that unites these models is that infection in the mucosa must occur for dissemination to take place. Whether this is a feature of CD4 lymphocytes, dendritic cells or macrophage infection is still unclear. A model that intertwines one or more of the above cell types would be more prudent than addressing each in isolation.

Propagation and dissemination of infection after vaginal transmission of simian immunodeficiency virus

In the current global AIDS pandemic, more than half of new human immunodeficiency virus type 1 (HIV-1) infections are acquired by women through intravaginal HIV exposure. For this study, we explored pathogenesis issues relevant to the development of effective vaccines to prevent infection by this route, using an animal model in which female rhesus macaques were exposed intravaginally to a high dose of simian immunodeficiency virus (SIV). We examined in detail the events that transpire from hours to a few days after intravaginal SIV exposure through week 4 to provide a framework for understanding the propagation, dissemination, and establishment of infection in lymphatic tissues (LTs) during the acute stage of infection. We show that the mucosal barrier greatly limits the infection of cervicovaginal tissues, and thus the initial founder populations of infected cells are small. While there was evidence of rapid dissemination to distal sites, we also show that continuous seeding from an expanding source of production at the portal of entry is likely critical for the later establishment of a productive infection throughout the systemic LTs. The initially small founder populations and dependence on continuous seeding to establish a productive infection in systemic LTs define a small window of maximum vulnerability for the virus in which there is an opportunity for the host, vaccines, or other interventions to prevent or control infection.