Neurons and oligodendrocytes differentiated from induced pluripotent stem cells (iPSCs) of patients with inherited TLR3 and UNC-93B deficiencies are found to be more susceptible to infection by HSV-1 than control cells because they fail to induce a normal interferon response, whereas neural stem cells and astrocytes are not susceptible. Childhood herpes simplex encephalitis (HSE) is a rare but severe disease in which the usually innocuous herpes simplex virus 1 (HSV-1) infects the central nervous system. This paper reports the development of an in vitro model for HSE. The authors derived induced pluripotent stem cells (iPSCs) from cells taken from patients with TLR3 and UNC-93B mutations. Neurons and immature oligodendrocytes differentiated from these iPSCs were more susceptible than normal cells to infection with HSV-1 and failed to induce a normal innate-immune response. By contrast, undifferentiated iPSCs, neural stem cells and astrocytes were not susceptible to HSV-1 infection. This study demonstrates the underlying pathogenesis of herpes simplex encephalitis in children with TLR3 and UNC-93B deficiencies. In the course of primary infection with herpes simplex virus 1 (HSV-1), children with inborn errors of toll-like receptor 3 (TLR3) immunity are prone to HSV-1 encephalitis (HSE)1,2,3. We tested the hypothesis that the pathogenesis of HSE involves non-haematopoietic CNS-resident cells. We derived induced pluripotent stem cells (iPSCs) from the dermal fibroblasts of TLR3- and UNC-93B-deficient patients and from controls. These iPSCs were differentiated into highly purified populations of neural stem cells (NSCs), neurons, astrocytes and oligodendrocytes. The induction of interferon-β (IFN-β) and/or IFN-λ1 in response to stimulation by the dsRNA analogue polyinosinic:polycytidylic acid (poly(I:C)) was dependent on TLR3 and UNC-93B in all cells tested. However, the induction of IFN-β and IFN-λ1 in response to HSV-1 infection was impaired selectively in UNC-93B-deficient neurons and oligodendrocytes. These cells were also much more susceptible to HSV-1 infection than control cells, whereas UNC-93B-deficient NSCs and astrocytes were not. TLR3-deficient neurons were also found to be susceptible to HSV-1 infection. The rescue of UNC-93B- and TLR3-deficient cells with the corresponding wild-type allele showed that the genetic defect was the cause of the poly(I:C) and HSV-1 phenotypes. The viral infection phenotype was rescued further by treatment with exogenous IFN-α or IFN-β ( IFN-α/β) but not IFN-λ1. Thus, impaired TLR3- and UNC-93B-dependent IFN-α/β intrinsic immunity to HSV-1 in the CNS, in neurons and oligodendrocytes in particular, may underlie the pathogenesis of HSE in children with TLR3-pathway deficiencies.

Research from JAMA — Surgical Site Infection and the Routine Use of Perioperative Hyperoxia in a General Surgical Population — A Randomized Controlled Trial — ContextSurgical site infection (SSI) in the general surgical population is a significant public health issue. The use of a high fractional inspired concentration of oxygen (FIO2) during the perioperative period has been reported to be of benefit in selected patients, but its role as a routine intervention has not been investigated.ObjectiveTo determine whether the routine use of high FIO2 during the perioperative period alters the incidence of SSI in a general surgical population.Design, Setting, and PatientsDouble-blind, randomized controlled trial conducted between September 2001 and May 2003 at a large university hospital in metropolitan New York City of 165 patients undergoing major intra-abdominal surgical procedures under general anesthesia.InterventionsPatients were randomly assigned to receive either 80% oxygen (FIO2 of 0.80) or 35% oxygen (FIO2 of 0.35) during surgery and for the first 2 hours after surgery.Main Outcome MeasuresPresence of clinically significant SSI in the first 14 days after surgery, as determined by clinical assessment, a management change, and at least 3 prospectively defined objective criteria.ResultsThe study groups were closely matched in a large number of clinical variables. The overall incidence of SSI was 18.1%. In an intention-to-treat analysis, the incidence of infection was significantly higher in the group receiving FIO2 of 0.80 than in the group with FIO2 of 0.35 (25.0% vs 11.3%; P = .02). FIO2 remained a significant predictor of SSI (P = .03) in multivariate regression analysis. Patients who developed SSI had a significantly longer length of hospitalization after surgery (mean [SD], 13.3 [9.9] vs 6.0 [4.2] days; P<.001).ConclusionsThe routine use of high perioperative FIO2 in a general surgical population does not reduce the overall incidence of SSI and may have predominantly deleterious effects. General surgical patients should continue to receive oxygen with cardiorespiratory physiology as the principal determinant.

The pace of human brain development is highly protracted compared with most other species^1–7. The maturation of cortical neurons is particularly slow, taking months to years to develop adult functions^3–5. Remarkably, such protracted timing is retained in cortical neurons derived from human pluripotent stem cells (hPSCs) during in vitro differentiation or upon transplantation into the mouse brain^4,8,9. Those findings suggest the presence of a cell-intrinsic clock setting the pace of neuronal maturation, although the molecular nature of this clock remains unknown. Here we identify an epigenetic developmental programme that sets the timing of human neuronal maturation. First, we developed a hPSC-based approach to synchronize the birth of cortical neurons in vitro which enabled us to define an atlas of morphological, functional and molecular maturation. We observed a slow unfolding of maturation programmes, limited by the retention of specific epigenetic factors. Loss of function of several of those factors in cortical neurons enables precocious maturation. Transient inhibition of EZH2, EHMT1 and EHMT2 or DOT1L, at progenitor stage primes newly born neurons to rapidly acquire mature properties upon differentiation. Thus our findings reveal that the rate at which human neurons mature is set well before neurogenesis through the establishment of an epigenetic barrier in progenitor cells. Mechanistically, this barrier holds transcriptional maturation programmes in a poised state that is gradually released to ensure the prolonged timeline of human cortical neuron maturation.