Strong mucosal immune responses in SIV infected macaques contribute to viral control and preserved CD4+ T-cell levels in blood and mucosal tissues.

BACKGROUND: Since there is still no protective HIV vaccine available, better insights into immune mechanism of persons effectively controlling HIV replication in the absence of any therapy should contribute to improve further vaccine designs. However, little is known about the mucosal immune response of this small unique group of patients. Using the SIV-macaque-model for AIDS, we had the rare opportunity to analyze 14 SIV-infected rhesus macaques durably controlling viral replication (controllers). We investigated the virological and immunological profile of blood and three different mucosal tissues and compared their data to those of uninfected and animals progressing to AIDS-like disease (progressors). RESULTS: Lymphocytes from blood, bronchoalveolar lavage (BAL), and duodenal and colonic biopsies were phenotypically characterized by polychromatic flow cytometry. In controllers, we observed higher levels of CD4+, CD4+CCR5+ and Gag-specific CD8+ T-cells as well as lower immune activation in blood and all mucosal sites compared to progressors. However, we could also demonstrate that immunological changes are distinct between these three mucosal sites.Intracellular cytokine staining demonstrated a significantly higher systemic and mucosal CD8+ Gag-specific cellular immune response in controllers than in progressors. Most remarkable was the polyfunctional cytokine profile of CD8+ lymphocytes in BAL of controllers, which significantly dominated over their blood response. The overall suppression of viral replication in the controllers was confirmed by almost no detectable viral RNA in blood and all mucosal tissues investigated. CONCLUSION: A strong and complex virus-specific CD8+ T-cell response in blood and especially in mucosal tissue of SIV-infected macaques was associated with low immune activation and an efficient suppression of viral replication. This likely afforded a repopulation of CD4+ T-cells in different mucosal compartments to almost normal levels. We conclude, that a robust SIV-specific mucosal immune response seems to be essential for establishing and maintaining the controller status and consequently for long-term survival.

Topical nonnucleoside reverse transcriptase inhibitor MC 1220 partially prevents vaginal RT-SHIV infection of macaques.

The availability of an effective vaginal microbicide would be a major step toward containment of HIV transmission as well as allowing women self-protection against HIV infection. Here we evaluated the efficacy of vaginal application of the potent nonnucleoside reverse transcriptase inhibitor (NNRTI) MC 1220 against vaginal challenge of macaques with RT-SHIV, a chimeric simian immunodeficiency virus (SIV) containing the reverse transcriptase (RT) gene of HIV-1. Challenge infection of monkeys with RT-SHIV currently represents the only nonhuman primate model available to test the anti-HIV-1 effects of NNRTIs. Two different gel formulations containing different MC 1220 concentrations were evaluated for efficacy in female rhesus macaques exposed to RT-SHIV. Five groups of five animals each were treated with two different gel compositions containing no drug, 0.1% or 0.5% MC 1220, followed by vaginal RT-SHIV challenge 30 min later. One animal in each group treated with the low concentration of MC 1220 as well as one control animal remained uninfected after vaginal challenge. By contrast, three of the animals receiving 0.5% MC 1220 remained uninfected, suggesting a threshold of the drug. Despite being negative for plasma viral RNA and absence of seroconversion, almost all uninfected animals exhibited SIV-specific T cells, either in the periphery or in lymph nodes draining the portal of virus entry. Our results make MC 1220 a promising compound for further development as a topical microbicide and warrant additional testing with improved formulation, long-lasting vaginal delivery systems, or even combinations with other inhibitors.

Flow cytometric characterization of the lymphocyte composition in a variety of mucosal tissues in healthy rhesus macaques.

BACKGROUND: Rhesus monkeys play a central role in model studies on human infectious diseases, and often mucosal organs are affected by these pathogens, e.g. HIV. However, a comparative investigation into lymphocyte composition from different mucosal tissues is still missing. METHODS: Lymphocyte composition of duodenum, jejunum, ileum, colon, vagina, cervix, uterus and bronchoalveolar lavage from healthy rhesus monkeys was characterized in detail by flow cytometry. Moreover, we compared the lymphocyte proportions from intestinal biopsies with resections. RESULTS: All mucosal tissues exhibited higher values of CD8(+) , CD4(+) CCR5(+) and CD45RA(-) memory T cells than blood, but similar levels of total T cells. Especially within the four gut sites, the lymphocyte composition varied significantly. The relative proportions of lymphocyte subsets from duodenal and colonic biopsies compared to resections differed. CONCLUSION: The lymphocyte composition highly varies between different mucosal sites, and data obtained from biopsy and necropsy samples were mostly not comparable.

Correlation between CD4+ T-cell loss and Gag-specific T cells in different intestinal sites of chronically SIV-infected rhesus monkeys.

OBJECTIVE: To determine the loss of CD4+ T cells and virus-specific cytotoxic T cells (CTL) in different mucosal sites of rhesus monkeys infected with simian immunodeficiency virus (SIV). DESIGN: A cross-sectional comparative investigation of seven different mucosal sites from chronically SIV-infected rhesus monkeys was performed by analyzing blood and mucosal lymphocytes. METHODS: Mucosal lymphocytes were isolated from duodenum, jejunum, ileum and colon as well as from vagina, cervix and uterus of SIV-infected rhesus monkeys at necropsy. CD4+ T cells and SIV-Gag-specific CTL were determined in blood and mucosal samples by flow cytometry. RESULTS: A significant depletion of CD4+ T cells was observed in blood and all mucosal sites of SIV-infected rhesus monkeys compared to uninfected animals. But the mean percentage loss of CD4+ T cells varied between 66 and 95% between the different mucosal tissues. The frequency of CTL ranged between 0.4 and 2.4% with the highest proportions in vagina and cervix. Among the intestinal sites the mean levels of CTL correlated with mean percentage loss of CD4+ T cells. CONCLUSION: A discriminative pronounced loss of CD4+ T cells among the mucosal tissues confirmed that viral replication affects different mucosal sites in a distinct way. Despite high levels of CTL, especially in vagina and cervix, the severe loss of mucosal CD4+ T cells could not be prevented during chronic SIV infection. However, within the four sites of the intestine a high virus-specific cellular immune response correlated with better preservation of CD4+ T cells.