Impaired intrinsic immunity to HSV-1 in human iPSC-derived TLR3-deficient CNS cells

Abstract

In the course of primary infection with herpes simplex virus 1 (HSV-1), children with inborn errors of TLR3 immunity are prone to HSV-1 encephalitis (HSE) 1–3. We tested the hypothesis that the pathogenesis of HSE involves non hematopoietic central nervous system (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 IFN-β and/or IFN-γ1 in response to poly(I:C) stimulation was dependent on TLR3 and UNC-93B in all cells tested. However, the induction of IFN-β and IFN-γ1 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 demonstrated that the genetic defect was the cause of the poly(I:C) and HSV-1 phenotypes. The viral infection phenotype was further rescued by treatment with exogenous IFN-α/β, but not IFN-γ1.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.

The toll-like receptor 3 pathway in homeostasis, responses to injury and wound repair

“…These findings were supported by subsequent analysis of patients with defects in genes encoding the TLR3 signalling components TRIF, TBK-1 and IRF3 [35][36][37]. An impaired TLR3-inducible type-1 IFN response to HSV-1 in neurons and oligodendrocytes in the central nervous system (CNS) was subsequently linked with this condition [32][33][34][35][36][37]. These findings are also consistent with studies in mouse models of DNA virus infections.…”

“…Patients with mutations in TLR3 and UNC93B1 are susceptible to HSV-1 encephalitis [32][33][34]. Recognition by TLR3 of intermediate dsRNA produced by HSV-1 during its replicative cycle likely explains this phenomenon [32].…”

Severe infectious diseases of childhood as monogenic inborn errors of immunity

“…TLR3 can recognize viral dsRNA intermediates. With the aid of induced pluripotent stem cell (iPSC) technology, we and our colleagues Lorenz Studer and Luigi Notarangelo demonstrated that the mutations in these patients impaired intrinsic antiviral immunity in neurons and oligodendrocytes, accounting for the brain-tropic nature of HSE (123). The central nervous system-restricted nature of HSE is explained by the TLR3-independence of most other cell types, including leukocytes and keratinocytes, tested for responses to dsRNAs (117,121).…”

TLR3 deficiency in herpes simplex encephalitis

“…7 However, only 10 of the 120 children or young adults with HSE studied by our group to date have been found to carry mutations affecting the TLR3 pathway. Two have autosomal dominant (AD) partial TLR3 deficiency 8 and a third has autosomal recessive (AR) complete TLR3 deficiency.…”

“…6 TLR3 is expressed on CNS-resident cells that are permissive for HSV-1 infection. 7 High susceptibility to HSV-1 infection in patient-specific induced pluripotent stem cell (iPSC)-derived UNC-93B-and TLR3-deficient neurons and oligodendrocytes has been demonstrated recently.…”