Gut-associated lymphoid tissue (GALT) has been identified as the primary target of HIV-1 infection. To investigate why GALT is especially vulnerable to HIV-1, and to determine whether the selective transmission of CCR5-using viral variants (R5) in vivo is the result of a greater susceptibility of GALT to this viral variant, we performed comparative studies of CXCR4-using (X4) and R5 HIV-1 infections of human lymphoid (tonsillar) and rectosigmoid tissues ex vivo under controlled laboratory conditions. We found that the relative level of R5 replication in rectosigmoid tissue is much greater than in tonsillar tissue. This difference is associated with the expression of the CCR5 co-receptor on approximately 70% of CD4 T cells in rectosigmoid tissue, whereas in tonsillar tissue it is expressed on fewer than 15% of CD4 T cells. Furthermore, tonsillar tissue responds to X4 HIV-1 infection by upregulating the secretion of CC-chemokines, providing a potential CCR5 blockade and further resistance to R5 infection, whereas gut tissue failed to increase such innate immune responses. Our results show that rectosigmoid tissue is more prone than tonsillar lymphoid tissue to R5 HIV-1 infection, primarily because of the high prevalence and availability of R5 cell targets and reduced chemokine blockade. The majority of CD4 T cells express CXCR4, however, and X4 HIV-1 readily replicates in both tissues, suggesting that although the differential expression of co-receptors contributes to the GALT vulnerability to R5 HIV-1, it alone cannot account for the selective R5 infection of the rectal mucosa in vivo.
"Therefore, the contribution of c-suPAR to chemotaxis and HIV expression was opposite in the context of CCS obtained from infected and uninfected tonsils in that c-suPAR did not modulate chemotaxis but inhibited HIV expression induced by CCS from uninfected tonsils, whereas it inhibited the chemotactic potential and contributed to HIV-1 expression induced by CCS from infected tonsils. Although in the present study we have not further investigated the underlying mechanisms responsible for this functional dichotomy, it is conceivable that c-suPAR might interfere with the intracellular signaling pathways induced by different factors present in the CCS of infected and uninfected histocultures, known to secrete different levels of cytokines and chemokines ,  able to influence both chemotaxis and HIV-1 expression. "
[Show abstract][Hide abstract] ABSTRACT: Cell-associated receptor for urokinase plasminogen activator (uPAR) is released as both full-length soluble uPAR (suPAR) and cleaved (c-suPAR) form that maintain ability to bind to integrins and other receptors, thus triggering and modulating cell signaling responses. Concerning HIV-1 infection, plasma levels of suPAR have been correlated with the severity of disease, levels of immune activation and ineffective immune recovery also in individuals receiving combination anti-retroviral therapy (cART). However, it is unknown whether and which suPAR forms might contribute to HIV-1 induced pathogenesis and to the related state of immune activation. In this regard, lymphoid organs represent an import site of chronic immune activation and virus persistence even in individuals receiving cART. Lymphoid organs of HIV-1(+) individuals showed an enhanced number of follicular dendritic cells, macrophages and endothelial cells expressing the cell-associated uPAR in comparison to those of uninfected individuals. In order to investigate the potential role of suPAR forms in HIV-1 infection of secondary lymphoid organs, tonsil histocultures were established from HIV-1 seronegative individuals and infected ex vivo with CCR5- and CXCR4-dependent HIV-1 strains. The levels of suPAR and c-suPAR were significantly increased in HIV-infected tonsil histocultures supernatants in comparison to autologous uninfected histocultures. Supernatants from infected and uninfected cultures before and after immunodepletion of suPAR forms were incubated with the chronically infected promonocytic U1 cell line characterized by a state of proviral latency in unstimulated conditions. In the contest of HIV-conditioned supernatants we established that c-suPAR, but not suPAR, inhibited chemotaxis and induced virus expression in U1 cells. In conclusion, lymphoid organs are an important site of production and release of both suPAR and c-suPAR, this latter form being endowed with the capacity of inhibiting chemotaxis and inducing HIV-1 expression.
PLoS ONE 07/2013; 8(7):e70606. DOI:10.1371/journal.pone.0070606 · 3.23 Impact Factor
"Such differences in TCID50 values measured in one system do not directly translate into consistent differences in virus replication capacity in another system, in this case in tissues from various donors . Furthermore, the observed differences in TCID50 of different viruses are much less than the variability that is seen for replication of a given virus stock in tissues from different donors , . "
[Show abstract][Hide abstract] ABSTRACT: Recently, it was found that 80% of sexual HIV-1 transmissions are established by a single virion/viral genome. To investigate whether the transmitted/founder (T/F) viruses have specific biological properties favoring sexual transmission, we inoculated human cervical tissue explants with isogenic HIV-1 viruses encoding Env sequences from T/F and control reference (C/R) HIV-1 variants as well as with full length T/F HIV-1 and compared their replication efficiencies, T cell depletion, and the activation status of infected cells. We found that all the HIV-1 variants were capable of transmitting infection to cervical tissue ex vivo and in this system preferentially replicate in activated CD4 T cells and deplete these cells. There was no difference in the biological properties of T/F and C/R HIV-1 variants as evaluated in ex vivo cervical tissue.
PLoS ONE 12/2012; 7(12):e50839. DOI:10.1371/journal.pone.0050839 · 3.23 Impact Factor
"Although the absolute levels of XMRV RNA released varied from donor to donor, the replication was similar to those observed in tonsillar tissue infected with some strains of HIV (R5 strains) (ranging between 2 and 5×106 RNA copies/mL) , but lower than viral production of more pathogenic strains of HIV (×4 strains), which range from 15 to 60×106 RNA copies/mL . However, for HIV has never been reported whether this amount of virus produced is sufficient to establish a new productive infection in a new histoculture. "
[Show abstract][Hide abstract] ABSTRACT: Xenotropic murine leukemia virus-related virus (XMRV) was generated after a recombination event between two endogenous murine leukemia viruses during the production of a prostate cancer cell line. Although the associations of the XMRV infection with human diseases appear unlikely, the XMRV is a retrovirus of undefined pathogenic potential, able to replicate in human cells in vitro. Since recent studies using animal models for infection have yielded conflicting results, we set out an ex vivo model for XMRV infection of human tonsillar tissue to determine whether XMRV produced by 22Rv1 cells is able to replicate in human lymphoid organs. Tonsil blocks were infected and infection kinetics and its pathogenic effects were monitored
XMRV, though restricted by APOBEC, enters and integrates into the tissue cells. The infection did not result in changes of T or B-cells, immune activation, nor inflammatory chemokines. Infectious viruses could be recovered from supernatants of infected tonsils by reinfecting DERSE XMRV indicator cell line, although these supernatants could not establish a new infection in fresh tonsil culture, indicating that in our model, the viral replication is controlled by innate antiviral restriction factors.
Overall, the replication-competent retrovirus XMRV, present in a high number of laboratories, is able to infect human lymphoid tissue and produce infectious viruses, even though they were unable to establish a new infection in fresh tonsillar tissue. Hereby, laboratories working with cell lines producing XMRV should have knowledge and understanding of the potential biological biohazardous risks of this virus.
PLoS ONE 05/2012; 7(5):e37415. DOI:10.1371/journal.pone.0037415 · 3.23 Impact Factor
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