IL-17c promotes peripheral nerve growth during human herpes simplex virus type 2 (HSV-2) infection

During human HSV-2 infection, peripheral nerve destruction and sensory anesthesia are rarely developed, despite frequent virus reactivation. The mechanisms underlying this clinical observation are unclear. Here, we describe a novel interaction between HSV infected keratinocytes and the peripheral nerve system via IL-17c that promotes neurite growth and neuron survival during reactivations. Skin biopsies obtained during asymptomatic human HSV-2 reactivation exhibit a higher nerve fiber density in relation to biopsies obtained during the virological and clinical quiescent phase. Keratinocytes, the peripheral targets of HSV reactivation, produce IL-17c both in vivo during HSV-2 reactivation in humans and in vitro in primary cultures. Further characterization indicates that IL17RE, the receptor specific for IL-17c signaling, is expressed on nerve endings in human skin and on nerve fibers, glia cells and sensory neurons in human dorsal root ganglia. The addition of exogenous human IL-17c promotes neurite growth and branching and provides directional guidance in a microfluidic device. Furthermore, pretreatment of IL-17c reduces apoptosis in HSV-2 infected primary neurons. Taken together, these results suggest that IL-17c might function as a neurotrophic factor to induce peripheral nerve ending growth and protect neurons from apoptosis during HSV reactivation. This interaction provides a potential mechanism for the lack of clinical nerve damage from a lifelong recurrent neurotropic viral infection. It also highlights the role of immune cytokines in regulating the functions of the peripheral nervous system.

Tin oxide nanowires suppress herpes simplex virus-1 entry and cell-to-cell membrane fusion

The advent of nanotechnology has ushered in the use of modified nanoparticles as potential antiviral agents against diseases such as herpes simplex virus 1 and 2 (HSV-1) (HSV-2), human immunodeficiency virus (HIV), monkeypox virus, and hepatitis B virus. Here we describe the application of tin oxide (SnO₂) nanowires as an effective treatment against HSV-1 infection. SnO₂ nanowires work as a carrier of negatively charged structures that compete with HSV-1 attachment to cell bound heparan sulfate (HS), therefore inhibiting entry and subsequent cell-to-cell spread. This promising new approach can be developed into a novel form of broad-spectrum antiviral therapy especially since HS has been shown to serve as a cellular co-receptor for a number of other viruses as well, including the respiratory syncytial virus, adeno-associated virus type 2, and human papilloma virus.

MyD88-dependent and MyD88-independent pathways in synergy, priming, and tolerance between TLR agonists

TLRs sense components of microorganisms and are critical host mediators of inflammation during infection. Different TLR agonists can profoundly alter inflammatory effects of one another, and studies suggest that the sequence of exposure to TLR agonists may importantly impact on responses during infection. We tested the hypothesis that synergy, priming, and tolerance between TLR agonists follow a pattern that can be predicted based on differential engagement of the MyD88-dependent (D) and the MyD88-independent (I) intracellular signaling pathways. Inflammatory effects of combinations of D and I pathway agonists were quantified in vivo and in vitro. Experiments used several D-specific agonists, an I-specific agonist (poly(I:C)), and LPS, which acts through both the D and I pathways. D-specific agonists included: peptidoglycan-associated lipoprotein, Pam3Cys, flagellin, and CpG DNA, which act through TLR2 (peptidoglycan-associated lipoprotein and Pam3Cys), TLR5, and TLR9, respectively. D and I agonists were markedly synergistic in inducing cytokine production in vivo in mice. All of the D-specific agonists were synergistic with poly(I:C) in vitro in inducing TNF and IL-6 production by mouse bone marrow-derived macrophages. Pretreatment of bone marrow-derived macrophages with poly(I:C) led to a primed response to subsequent D-specific agonists and vice versa, as indicated by increased cytokine production, and increased NF-kappaB translocation. Pretreatment with a D-specific agonist augmented LPS-induced IFN-beta production. All D-specific agonists induced tolerance to one another. Thus, under the conditions studied here, simultaneous and sequential activation of both the D and I pathways causes synergy and priming, respectively, and tolerance is induced by agonists that act through the same pathway.