MgSO4 exposure before preterm birth is neuroprotective, reducing the risk of cerebral palsy and major motor dysfunction. Neonatal inflammatory cytokine levels correlate with neurologic outcome, leading us to assess the effect of MgSO4 on cytokine production in humans. We found reduced maternal TNF-α and IL-6 production following in vivo MgSO4 treatment. Short-term exposure to a clinically effective MgSO4 concentration in vitro substantially reduced the frequency of neonatal monocytes producing TNF-α and IL-6 under constitutive and TLR-stimulated conditions, decreasing cytokine gene and protein expression, without influencing cell viability or phagocytic function. In summary, MgSO4 reduced cytokine production in intrapartum women, term and preterm neonates, demonstrating effectiveness in those at risk for inflammation-associated adverse perinatal outcomes. By probing the mechanism of decreased cytokine production, we found that the immunomodulatory effect was mediated by magnesium and not the sulfate moiety, and it was reversible. Cellular magnesium content increased rapidly upon MgSO4 exposure, and reduced cytokine production occurred following stimulation with different TLR ligands as well as when magnesium was added after TLR stimulation, strongly suggesting that magnesium acts intracellularly. Magnesium increased basal IκBα levels, and upon TLR stimulation was associated with reduced NF-κB activation and nuclear localization. These findings establish a new paradigm for innate immunoregulation, whereby magnesium plays a critical regulatory role in NF-κB activation, cytokine production, and disease pathogenesis.

Limited material resources, exposure to violence, and high-risk sexual behaviors were the best predictors of HIV risk.

Zoonotic transmission of lethal Henipaviruses (HNV) from their natural fruit bat reservoirs to humans has only been reported in Australia and South/Southeast Asia. However, a recent study discovered numerous HNV clades in African bat samples. To determine the potential for HNV spillover events among humans in Africa, here we examine well-curated sets of bat (Eidolon helvum, n=44) and human (n=497) serum samples from Cameroon for Nipah virus (NiV) cross-neutralizing antibodies (NiV-X-Nabs). Using a VSV-based pseudoparticle seroneutralization assay, we detect NiV-X-Nabs in 48% and 3-4% of the bat and human samples, respectively. Seropositive human samples are found almost exclusively in individuals that reported butchering bats for bushmeat. Seropositive human sera also neutralize Hendra virus and Gh-M74a (an African HNV) pseudoparticles, as well as live NiV. Butchering bat meat and living in areas undergoing deforestation are the most significant risk factors associated with seropositivity. Evidence for HNV spillover events warrants increased surveillance efforts.

*Telomerase reverse transcribes telomere DNA onto the ends of linear chromosomes and retards cellular aging. In contrast to most normal somatic cells, which show little or no telomerase activity, immune cells up-regulate telomerase in concert with activation. Nevertheless, during aging and chronic HIV-1 infection, there are high proportions of dysfunctional CD8؉ CTL with short telomeres, suggesting that telomerase is limiting. The present study shows that exposure of CD8 ؉ T lymphocytes from HIV-infected human donors to a small molecule telomerase activator (TAT2) modestly retards telomere shortening, increases proliferative potential, and, importantly, enhances cytokine/chemokine production and antiviral activity. The enhanced antiviral effects were abrogated in the presence of a potent and specific telomerase inhibitor, suggesting that TAT2 acts primarily through telomerase activation. Our study is the first to use a pharmacological telomerase-based approach to enhance immune function, thus directly addressing the telomere loss immunopathologic facet of chronic viral infection. The Journal of Immunology, 2008, 181: 7400 -7406.T elomeres, the TTAGGG tandem repeats at chromosome ends, become progressively shorter in dividing somatic cells (1). Numerous studies have shown associations between leukocyte telomere shortening and risk of disease, suggesting that these cells may serve as biomarkers for the cumulative burden of inflammation, chronic immune activation, or oxidative stress. Indeed, hypertension and increased insulin resistance are associated with shorter leukocyte telomere length in the participants of the Framingham heart study (2), and telomere shortening in peripheral blood leukocytes chronicles ischemic heart disease risk in older people (3). Leukocyte telomere length also correlates with bone mineral density, and shorter telomeres are seen in women with osteoporosis (4). Finally, in both aging and chronic HIV-1 infection, there are increased proportions of CD8 ϩ T lymphocytes with shortened telomeres, reduced proliferative capacity and altered effector function (5). Thus, strategies to retard or prevent telomere loss may lead to novel treatments for a variety of human pathologies.T and B lymphocytes transiently up-regulate telomerase, the cellular reverse transcriptase that adds telomeric DNA to the ends of chromosomes (6 -8). Such telomerase activity is believed to mitigate the losses of replicative capacity and function caused by chronic antigenic stimulation, oxidative stress, and cellular aging (9, 10). However, the ability of CD8 ϩ T lymphocytes to up-regulate telomerase is lost after repeated encounters with Ag, and continued chronic stimulation ultimately leads to critically short telomeres and other changes associated with replicative senescence (10, 11).We hypothesized that sustained telomerase activity in chronically activated CD8 ϩ T lymphocytes might prevent or delay immune dysfunction associated with aging and/or chronic disease. In previous studies, we showed that gene transduction of ...

Pluripotent stem cells (PSC) may provide a potential source of haematopoietic stem/progenitor cells (HSPCs) for transplantation; however, unknown molecular barriers prevent the self-renewal of PSC-HSPCs. Using two-step differentiation, human embryonic stem cells (hESCs) differentiated in vitro into multipotent haematopoietic cells that had CD34+CD38−/loCD90+CD45+GPI-80+ foetal liver (FL) HSC immunophenotype, but displayed poor expansion potential and engraftment ability. Transcriptome analysis of immunophenotypic hESC-HSPCs revealed that, despite their molecular resemblance to FL-HSPCs, medial HOXA genes remained suppressed. Knockdown of HOXA7 disrupted FL-HSPC function and caused transcriptome dysregulation that resembled hESC-derived progenitors. Overexpression of medial HOXA genes prolonged FL-HSPC maintenance but was insufficient to confer self-renewal to hESC-HSPCs. Stimulation of retinoic acid signalling during endothelial-to-haematopoietic transition induced the HOXA cluster and other HSC/definitive haemogenic endothelium genes, and prolonged HSPC maintenance in culture. Thus, retinoic acid signalling-induced medial HOXA gene expression marks the establishment of the definitive HSC fate and controls HSC identity and function.