The innate immune system senses pathogens by pattern recognition receptors (PRR) that signal to induce effector cytokines, such as type I interferons (IFNs). We characterized IFNε as a type I IFN because it signaled via the Ifnar1 and Ifnar2 receptors to induce IFN-regulated genes. In contrast to other type I IFNs, IFNε was not induced by known PRR pathways, but was instead constitutively expressed by epithelial cells of the female reproductive tract (FRT) and hormonally regulated. Ifnε-deficient mice had increased susceptibility to infection of the FRT by common sexually transmitted infections (STIs) Herpes Simplex Virus (HSV)-2 and Chlamydia muridarum. IFNε is thus a potent anti-pathogen and immunoregulatory cytokine that may be important in combating STIs which represent a major global health and socioeconomic burden.

Inflammatory lymphangiogenesis plays a crucial role in the development of inflammation and transplant rejection. The mechanisms of inflammatory lymphangiogenesis during bacterial infection, toll-like receptor ligand administration, and wound healing are well characterized and depend on ligands for the vascular endothelial grow factor receptor (VEGFR) 3 that are produced by infiltrating macrophages. But inflammatory lymphangiogenesis in nonlymphoid tissues during chronic viral infection is unstudied. Herpes simplex virus 1 (HSV-1) infection of the cornea is a leading cause of blindness and depends on aberrant host immune responses to antigen within the normally immunologically privileged cornea. We report that corneal HSV-1 infection drives lymphangiogenesis and that corneal lymphatics persist past the resolution of infection. The mechanism of HSV-1–induced lymphangiogenesis was distinct from the described mechanisms of inflammatory lymphangiogenesis. HSV-1–elicited lymphangiogenesis was strictly dependent on VEGF-A/VEGFR-2 signaling but not on VEGFR-3 ligands. Macrophages played no role in the induction of lymphangiogenesis and were not a detectable source of VEGF-A. Rather, using VEGF-A reporter transgenic mice, we have identified infected epithelial cells as the primary source of VEGF-A during HSV-1 infection. Our results indicate that HSV-1 directly induces vascularization of the cornea through up-regulation of VEGF-A expression.

We have previously found that interleukin (IL)-2, IL-10, interferon (IFN)-gamma, RANTES, and tumor necrosis factor (TNF)-alpha mRNA transcription remain elevated in the trigeminal ganglia (TG) of herpes simplex virus type 1 (HSV-1) latently infected mice up to 120 days postinoculation (p.i.). To determine if this phenomenon was dependent on HSV-1 DNA replication after the establishment of latency (i.e., reactivation), cytokine gene expression was compared in TG of acyclovir-treated and untreated latently infected mice. Oral acyclovir treatment (begun 16 days p.i.) had no effect on serum levels of total anti-HSV-1 antibodies. However, there was a significant reduction in the titer of antibody specific for glycoprotein D and glycoprotein B but not glycoprotein H/L 120 days PI in the acyclovir-treated compared to vehicle-treated mice. These differences were not significant at earlier time points (i.e., days 34 and 60 p.i.). Consistent with these findings, acyclovir had no effect on cytokine gene expression in latently infected TG 35 and 60 days p.i. However, 120 days p.i., IFN-gamma and TNF-alpha mRNA were approaching baseline levels in TG of acyclovir-treated mice, but remained significantly elevated in untreated controls (i.e., IFN-gamma mRNA levels were sixfold higher in TG of untreated mice). Therefore, viral DNA replication appears to provide an antigenic stimulus for persistent cytokine gene expression in latently infected TG.

Objective. The sympathetic nervous system (SNS) seems to play a proinflammatory role in the early asymptomatic phase of arthritis, but its role in the late stages of chronic arthritis is not well known. The purpose of this study was to examine the effects of the SNS on late-stage chronic arthritis in mice with type II collagen-induced arthritis (CIA).Methods. We tested the effects of the SNS by ablating sympathetic nerves at different time points in mice with CIA. Early sympathectomy was performed 7 days before immunization. Late sympathectomy was performed on day 56. Cytokine stimulation assays were performed on local lymph node cells and spleen cells, and levels of interleukin-10 (IL-10), IL-4, tumor necrosis factor ␣ (TNF␣), and interferon-␥ (IFN␥) were determined.Results. Animals with CIA that underwent early sympathectomy showed significantly lower arthritis scores than the controls. In contrast, animals that underwent late sympathectomy had significantly increased arthritis scores compared with controls. On day 0, lymph node cells from animals subjected to early sympathectomy had increased levels of IL-10 and IL-4 and unchanged levels of TNF␣ and IFN␥ compared with those from untreated animals. This indicates an immune-stimulating property of the SNS in draining lymph nodes. On day 80, lymph node cells and spleen cells from animals subjected to late sympathectomy showed increased levels of TNF␣ and IFN␥ compared with those from nonsympathectomized controls with CIA. This indicates an immune-depressing property of the SNS in draining lymph nodes and spleen. Arthritis per se largely diminished sympathetic nerve fiber density in synovium on day 80 (P < 0.01).Conclusion. The effect of the SNS is bimodal, enhancing or depressing levels of proinflammatory and antiinflammatory cytokines. This feature is dependent on the time point of immune system activation and the respective compartment. The SNS supports inflammation during the asymptomatic phase of CIA, whereas it inhibits inflammation during the chronic symptomatic phase.Since the work of Selye in the 1940s (1), the sympathetic nervous system (SNS) together with the hypothalamic-pituitary-adrenal axis has been thought to play an important supportive role in the fight-or-flight response during stressful events. In linking this important concept to inflammatory diseases, several groups of investigators working from 1960 to the late 1980s delineated a proinflammatory role of the SNS for the early inflammatory response (for review, see ref.2). Indeed, the SNS seems to be a critical proinflammatory component of neurogenic inflammation, which is particularly evident during the first hours after induction of joint inflammation (3), when the SNS mediates an increase in vessel leakage, plasma extravasation, migration of leukocytes to inflamed tissue. This is accompanied by stimulation of sensory nerve fibers (2).At the beginning of the 1980s, with the introduction of in vitro immune cell culture assays that could continue for several days and with the detection of Sup...