Presenting Author:

Osefame Ewaleifoh

Principal Investigator:

Greg Smith

Department:

Microbiology-Immunology

Keywords:

HSV infection, Innate immunity, IPSC, Encephalities, Toll like receptors, Herpes, Interferon.

Location:

Third Floor, Feinberg Pavilion, Northwestern Memorial Hospital

B86 - Basic Science

TLR3 Restricts Entry To Protect Human CNS Neurons From HSV-1

Background: HSV-1 infection of CNS neurons can result in severe neurological disorders from Herpes Simplex Encephalitis (HSE). In born genetic disorders in Toll like receptor 3 functions have recently been observed to increase susceptibility to HSE. This study investigates the mechanism and role of TLR3 in restricting HSV-1 infection in human iPSC derived neurons. Methods: We examined the mechanism by which Toll-like receptor 3 (TLR3) protects CNS neurons from herpes simplex virus type 1 (HSV-1) infection. Induced pluripotent stem cell derived CNS neurons obtained from TLR3, UnC93, STAT-1 mutant patients and healthy controls were infected with recombinant strains of HSV-1 expressing fluorescent reporter fusions. Viral entry, retrograde axon transport, and gene expression were assessed. Results: Our studies indicate that healthy control CNS neurons were resistant to HSV-1 infection arising from a stringent block in both viral entry and retrograde axonal transport. Viral entry required a transient endocytosis step followed by membrane fusion to release capsids into the cytosol. TLR3-mediated inhibition of HSV-1 infection of CNS neurons occurs by a rapid interferon-independent mechanism intrinsic to the axon. The absence of TLR3, but not STAT-1, permitted robust retrograde axonal viral transport. The axonal barrier was restored in TLR3 patient cells upon addition of exogenous IFNbeta to neuronal soma, but absent following IFNbeta addition to axons. Conclusions: The results document that human CNS neurons antagonize HSV-1 infection in a TLR3 dependent/interferon independent manner by preventing viral entry and retrograde axon transport as well as in a TLR3-independent/interferon-dependent mechanism .