Stepwise Release of Biologically Active HMGB1 during HSV-2 Infection

BACKGROUND: High mobility group box 1 protein (HMGB1) is a major endogenous danger signal that triggers inflammation and immunity during septic and aseptic stresses. HMGB1 recently emerged as a key soluble factor in the pathogenesis of various infectious diseases, but nothing is known of its behaviour during herpesvirus infection. We therefore investigated the dynamics and biological effects of HMGB1 during HSV-2 infection of epithelial HEC-1 cells. METHODOLOGY/PRINCIPAL FINDINGS: Despite a transcriptional shutdown of HMGB1 gene expression during infection, the intracellular pool of HMGB1 protein remained unaffected, indicating its remarkable stability. However, the dynamics of HMGB1 was deeply modified in infected cells. Whereas viral multiplication was concomitant with apoptosis and HMGB1 retention on chromatin, a subsequent release of HMGB1 was observed in response to HSV-2 mediated necrosis. Importantly, extracellular HMGB1 was biologically active. Indeed, HMGB1-containing supernatants from HSV-2 infected cells induced the migration of fibroblasts from murine or human origin, and reactivated HIV-1 from latently infected T lymphocytes. These effects were specifically linked to HMGB1 since they were blocked by glycyrrhizin or by a neutralizing anti-HMGB1 antibody, and were mediated through TLR2 and the receptor for Advanced Glycation End-products (RAGE). Finally, we show that genital HSV-2 active infections also promote HMGB1 release in vivo, strengthening the clinical relevance of our experimental data. CONCLUSIONS: These observations target HMGB1 as an important actor during HSV-2 genital infection, notably in the setting of HSV-HIV co-infection

HIV-1 and recombinant gp120 affect the survival and differentiation of human vessel wall-derived mesenchymal stem cells

BAckground:HIV infection elicits the onset of a progressive immunodeficiency and also damages several other organs and tissues such as the CNS, kidney, heart, blood vessels, adipose tissue and bone. In particular, HIV infection has been related to an increased incidence of cardiovascular diseases and derangement in the structure of blood vessels in the absence of classical risk factors. The recent characterization of multipotent mesenchymal cells in the vascular wall, involved in regulating cellular homeostasis, suggests that these cells may be considered a target of HIV pathogenesis. This paper investigated the interaction between HIV-1 and vascular wall resident human mesenchymal stem cells (MSCs). RESULTS: MSCs were challenged with classical R5 and X4 HIV-1 laboratory strains demonstrating that these strains are able to enter and integrate their retro-transcribed proviral DNA in the host cell genome. Subsequent experiments indicated that HIV-1 strains and recombinant gp120 elicited a reliable increase in apoptosis in sub-confluent MSCs. Since vascular wall MSCs are multipotent cells that may be differentiated towards several cell lineages, we challenged HIV-1 strains and gp120 on MSCs differentiated to adipogenesis and endotheliogenesis. Our experiments showed that the adipogenesis is increased especially by upregulated PPAR\u3b3 activity whereas the endothelial differentiation induced by VEGF treatment was impaired with a downregulation of endothelial markers such as vWF, Flt-1 and KDR expression. These viral effects in MSC survival and adipogenic or endothelial differentiation were tackled by CD4 blockade suggesting an important role of CD4/gp120 interaction in this context. CONCLUSIONS: The HIV-related derangement of MSC survival and differentiation may suggest a direct role of HIV infection and gp120 in impaired vessel homeostasis and in genesis of vessel damage observed in HIV-infected patients

HMBG1 and other soluble factors in HIV-1 pathogenesis [Elektronisk resurs]

The innate immune system is the first defense mechanism invading pathogens encounter. Macrophages, dendritic cells and cytokines/chemokines are important factors for the functionality of the innate immunity, and provide the adaptive immune system with sufficient signals for the proper action. Immune activation occurring during HIV-1 infection is essential to understand and investigate. The aims of this thesis were to evaluate the role of immune activation factors of the innate immune system, such as cytokines and chemokines, in different sets of patient categories, cellular systems and phases during the HIV-1 infection. We were most interested in a particular cytokine, the high mobility group box protein 1 (HMGB1). In addition to our in vitro experiments, we had access to an unique cohort, the Quest study, which is the first placebo controlled treatment trial in acute HIV-1 infection. For our substudy, we selected 22 patients, categorized into responders and non-responders regarding the outcome of their viral load after analytical treatment interruption (ATI). We found that high levels of immune activation as determined by the pattern of cytokines/chemokines during PHI, did not favor a better virological outcome after ATI. The early initiation of ART did not seem to affect the preservation of the immune system. HMGB1 is a proinflammatory cytokine, ubiquitously expressed in all nucleated cells, with a functional importance as a regulator of transcription and stabilization of the nucleosomal structure. HMGB1 is actively secreted from LPS- or TNF-activated macrophages/monocytes, pituicytes and other cells. HMGB1 can also be passively released by damaged necrotic or apoptotic cells. We studied the role of HGMB1 in different systems and modes during HIV-1 infection. Extracellular HMGB1 upregulated HIV-1 infection in latently infected U1 monocytic cells, but did not have impact on viral replication in ACH-2 Tlymphocytic cells. In acute HIV-1 infected monocyte-derived macrophages (MDMs), HIV-1 production was downregulated, most likely due to the increased production of the chemokines MIP-1alpha, MIP-1beta and Rantes. Furthermore, higher levels of HMGB1 were found in HIV-1 infected patients with deteriorated immune status and opportunistic conditions, compared to uninfected individuals and HIV-1 infected patients with less preserved immune status. Additionally, HMGB1 was released by HIV-1 infected MT4 cells and CD4+ T-cells, in connection with virus induced cell death. This release could be interfered by addition of a pan-caspase inhibitor Z-vad to MT4 cells cultures. We suggest that HMGB1 was released passively from MT4 cells not only during necrosis but also during apoptosis. In conclusion, the presented data cast a light on the importance of the immune activation process during HIV-1 pathogenesis. HMGB1 is released during the viral cell infection and may be a molecule connecting the cell death processes and the immune activation during HIV-1 infection