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Corneal transparency is an essential characteristic necessary for normal vision. In response to microbial infection, the integrity of the cornea can become compromised as a result of the inflammatory response and the ensuing tissue pathology including neovascularization (NV) and collagen lamellae destruction. We have previously found complement activation contributes to cornea pathology-specifically, denervation in response to HSV-1 infection. Therefore, we investigated whether the complement system also played a role in HSV-1-mediated neovascularization. Using wild type (WT) and complement component 3 deficient (C3 KO) mice infected with HSV-1, we found corneal NV was accelerated associated with an increase in inflammatory monocytes (CD11b+CCR2+CD115+/−Ly6G−Ly6Chigh), macrophages (CD11b+CCR2+CD115+Ly6G−Ly6Chigh) and a subpopulation of granulocytes/neutrophils (CD11b+CCR2−CD115+Ly6G+Ly6Clow). There were also increases in select pro-inflammatory and pro-angiogenic factors including IL-1α, matrix metalloproteinases (MMP)-2, MMP-3, MMP-8, CXCL1, CCL2, and VEGF-A that coincided with increased inflammation, neovascularization, and corneal opacity in the C3 KO mice. The difference in inflammation between WT and C3 KO mice was not driven by changes in virus titer. However, viral antigen clearance was hindered in C3 KO mouse corneas suggesting the complement system has a dynamic regulatory role within the cornea once an inflammatory cascade is initiated by HSV-1.

The intensity and longevity of inflammatory responses to inhaled allergens is determined largely by the balance between effector and regulatory immune responses, but the mechanisms that determine the relative magnitudes of these opposing forces remain poorly understood. We have found that the type of adjuvant used during allergic sensitization has a profound effect on both the nature and longevity of the pulmonary inflammation triggered by subsequent reexposure to that same provoking allergen. TLR ligand adjuvants and house dust extracts primed immune responses characterized by a mixed neutrophilic and eosinophilic inflammation that was suppressed by multiple daily allergen challenges. During TLR ligand-mediated allergic sensitization, mice displayed transient airway neutrophilia, which triggered the release of TGF-β into the airway. This neutrophil-dependent production of TGF-β during sensitization had a delayed, suppressive effect on eosinophilic responses to subsequent allergen challenge. Neutrophil depletion during sensitization did not affect numbers of Foxp3+ Tregs but increased proportions of Gata3+CD4+ T cells, which, upon their transfer to recipient mice, triggered stronger eosinophilic inflammation. Thus, a neutrophil/TGF-β axis acts during TLR-mediated allergic sensitization to fine-tune the phenotype of developing allergen-specific CD4+ T cells and limit their pathogenicity, suggesting a novel immunotherapeutic approach to control eosinophilia in asthma.

The contribution of T cell and antibody responses following vaccination in resistance to herpes simplex virus 1 (HSV-1) infection continues to be rigorously investigated. In the present article, we explore the contribution of CD8(+) T cells specific for the major antigenic epitope for HSV-1 glycoprotein B (gB(498–505), gB) in C57BL/6 mice using a transgenic mouse (gBT-I.1) model vaccinated with HSV-1 0ΔNLS. gBT-I.1-vaccinated mice did not generate a robust neutralization antibody titer in comparison to the HSV-1 0ΔNLS-vaccinated wild-type C57BL/6 counterpart. Nevertheless, the vaccinated gBT-I.1 mice were resistant to ocular challenge with HSV-1 compared to vehicle-vaccinated animals based on survival and reduced corneal neovascularization but displayed similar levels of corneal opacity. Whereas there was no difference in the virus titer recovered from the cornea comparing vaccinated mice, HSV-1 0ΔNLS-vaccinated animals possessed significantly less infectious virus during acute infection in the trigeminal ganglia (TG) and brain stem compared to the control-vaccinated group. These results correlated with a significant increase in gB-elicited interferon-γ (IFN-γ), granzyme B, and CD107a and a reduction in lymphocyte activation gene 3 (LAG-3), programmed cell death 1 (PD-1), and T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3) expressed by TG infiltrating gB-specific CD8(+) T cells from the HSV-1 0ΔNLS-vaccinated group. Antibody depletion of CD8(+) T cells in HSV-1 0ΔNLS-vaccinated mice rendered animals highly susceptible to virus-mediated mortality similar to control-vaccinated mice. Collectively, the HSV-1 0ΔNLS vaccine is effective against ocular HSV-1 challenge, reducing ocular neovascularization and suppressing peripheral nerve virus replication in the near absence of neutralizing antibody in this unique mouse model. IMPORTANCE The role of CD8(+) T cells in antiviral efficacy using a live-attenuated virus as the vaccine is complicated by the humoral immune response. In the case of the herpes simplex virus 1 (HSV-1) 0ΔNLS vaccine, the correlate of protection has been defined to be primarily antibody driven. The current study shows that in the near absence of anti-HSV-1 antibody, vaccinated mice are protected from subsequent challenge with wild-type HSV-1 as measured by survival. The efficacy is lost following depletion of CD8(+) T cells. Whereas increased survival and reduction in virus replication were observed in vaccinated mice challenged with HSV-1, cornea pathology was mixed with a reduction in neovascularization but no change in opacity. Collectively, the study suggests CD8(+) T cells significantly contribute to the host adaptive immune response to HSV-1 challenge following vaccination with an attenuated virus, but multiple factors are involved in cornea pathology in response to ocular virus challenge.

The cornea is essential for vision yet highly sensitive to immune-mediated damage following infection. Generating vaccines that provide sterile immunity against ocular surface pathogens without evoking vision loss is therefore clinically challenging. Here, we tested a prophylactic live-attenuated vaccine against herpes simplex virus type 1 (HSV-1), a widespread human pathogen that can cause corneal blindness. Parenteral vaccination of mice resulted in sterile immunity to subsequent HSV-1 challenge in the cornea and suppressed productive infection of the nervous system. This protection was unmatched by a relevant glycoprotein subunit vaccine. Efficacy of the live-attenuated vaccine involved a T-dependent humoral immune response and complement C3 but not Fcγ-receptor 3 or interferon-α/β signaling. Proteomic analysis of viral proteins recognized by antiserum revealed an unexpected repertoire dominated by sequestered antigens rather than surface-exposed envelope glycoproteins. Ocular HSV-1 challenge in naive and subunit-vaccinated mice triggered vision loss and severe ocular pathologies including corneal opacification, scar formation, neovascularization, and sensation loss. However, corneal pathology was absent in mice receiving the live-attenuated vaccine concomitant with complete preservation of visual acuity. Collectively, this is the first comprehensive report of a prophylactic vaccine candidate that elicits resistance to ocular HSV-1 infection while fully preserving the cornea and visual acuity.

The capacity of licensed vaccines to protect the ocular surface against infection is limited. Common ocular pathogens, such as HSV-1, are increasingly recognized as major contributors to visual morbidity worldwide. Humoral immunity is an essential correlate of protection against HSV-1 pathogenesis and ocular pathology, yet the ability of Ab to protect against HSV-1 is deemed limited due to the slow IgG diffusion rate in the healthy cornea. We show that a live-attenuated HSV-1 vaccine elicits humoral immune responses that are unparalleled by a glycoprotein subunit vaccine vis-à-vis Ab persistence and host protection. The live-attenuated vaccine was used to assess the impact of the immunization route on vaccine efficacy. The hierarchical rankings of primary immunization route with respect to efficacy were s.c. ≥ mucosal > i.m. Prime-boost vaccination via sequential s.c. and i.m. administration yielded greater efficacy than any other primary immunization route alone. Moreover, our data support a role for complement in prophylactic protection, as evidenced by intracellular deposition of C3d in the corneal epithelium of vaccinated animals following challenge and delayed viral clearance in C3-deficient mice. We also identify that the neonatal Fc receptor (FcRn) is upregulated in the cornea following infection or injury concomitant with increased Ab perfusion. Lastly, selective small interfering RNA–mediated knockdown of FcRn in the cornea impeded protection against ocular HSV-1 challenge in vaccinated mice. Collectively, these findings establish a novel mechanism of humoral protection in the eye involving FcRn and may facilitate vaccine and therapeutic development for other ocular surface diseases.

The ocular surface is continually exposed to the external environment, yet the default regulation of this mucosal site involves immune privilege to maintain normal vision. Many regulatory mechanisms work together to create an immunological balance that suppresses inflammation and limits microbial growth in the ocular surface mucosa to preserve the visual axis. However, the ocular surface mucosa remains vulnerable to a variety of pathogens that can break immune tolerance and provoke substantial ocular immunopathology. The coordinated mechanisms that govern immune privilege but drive pathology in the eye present a distinct conundrum for vaccine development: how to amplify the immune system in the ocular mucosa without provoking visual morbidity? Even short-lived inflammatory events in the eye can have deleterious visual outcomes. This chapter reviews the organization and immunology of the ocular surface mucosa, common ocular pathogens, and current strategies guiding ocular vaccine development for two of the leading infectious causes of blindness worldwide: Chlamydia trachomatis and herpes simplex virus type 1. While the ocular mucosa is now a common delivery route for vaccines against diseases of veterinary and agricultural importance, this chapter will focus on human pathogens and their impact on vision.

Whether complement dysregulation directly contributes to the pathogenesis of peripheral nervous system diseases, including sensory neuropathies, is unclear. We addressed this important question in a mouse model of ocular HSV-1 infection, where sensory nerve damage is a common clinical problem. Through genetic and pharmacologic targeting, we uncovered a central role for C3 in sensory nerve damage at the morphological and functional levels. Interestingly, CD4 T cells were central in facilitating this complement-mediated damage. This same C3/CD4 T cell axis triggered corneal sensory nerve damage in a mouse model of ocular graft-versus-host disease (GVHD). However, this was not the case in a T-dependent allergic eye disease (AED) model, suggesting that this inflammatory neuroimmune pathology is specific to certain disease etiologies. Collectively, these findings uncover a central role for complement in CD4 T cell-dependent corneal nerve damage in multiple disease settings and indicate the possibility for complement-targeted therapeutics to mitigate sensory neuropathies.

HSV-1 continues to be the leading cause of infectious corneal blindness. Clinical trials for vaccines against genital HSV infection have been ongoing for more than three decades. Despite this, no approved vaccine exists, and no formal clinical trials have evaluated the impact of HSV vaccines on eye health. We review here the current state of development for an efficacious HSV-1 vaccine and call for involvement of ophthalmologists and vision researchers.

HSV-1 is the leading cause of sporadic viral encephalitis, with mortality rates approaching 30% despite treatment with the antiviral drug of choice, acyclovir. Permanent neurologic deficits are common in patients that survive, but the mechanism leading to this pathology is poorly understood, impeding clinical advancements in treatment to reduce CNS morbidity. Using magnetic resonance imaging and type I IFN receptor–deficient mouse chimeras, we demonstrate HSV-1 gains access to the murine brain stem and subsequently brain ependymal cells, leading to enlargement of the cerebral lateral ventricle and infection of the brain parenchyma. A similar enlargement in the lateral ventricles is found in a subpopulation of herpes simplex encephalitic patients. Associated with encephalitis is an increase in CXCL1 and CXCL10 levels in the cerebral spinal fluid, TNF-α expression in the ependymal region, and the influx of neutrophils of encephalitic mouse brains. Reduction in lateral ventricle enlargement using anti-secretory factor peptide 16 reduces mortality significantly in HSV-1–infected mice without any effect on expression of inflammatory mediators, infiltration of leukocytes, or changes in viral titer. Microglial cells but not infiltrating leukocytes or other resident glial cells or neurons are the principal source of resistance in the CNS during the first 5 d postinfection through a Toll/IL-1R domain-containing adapter inducing IFN-β–dependent, type I IFN pathway. Our results implicate lateral ventricle enlargement as a major cause of mortality in mice and speculate such an event transpires in a subpopulation of human HSV encephalitic patients.

Viral fitness dictates virulence and capacity to evade host immune defenses. Understanding the biological underpinnings of such features is essential for rational vaccine development. We have previously shown that the live-attenuated herpes simplex virus 1 (HSV-1) mutant lacking the nuclear localization signal (NLS) on the ICP0 gene (0ΔNLS) is sensitive to inhibition by interferon beta (IFN-β) in vitro and functions as a highly efficacious experimental vaccine. Here, we characterize the host immune response and in vivo pathogenesis of HSV-1 0ΔNLS relative to its fully virulent parental strain in C57BL/6 mice. Additionally, we explore the role of type 1 interferon (IFN-α/β) signaling on virulence and immunogenicity of HSV-1 0ΔNLS and uncover a probable sex bias in the induction of IFN-α/β in the cornea during HSV-1 infection. Our data show that HSV-1 0ΔNLS lacks neurovirulence even in highly immunocompromised mice lacking the IFN-α/β receptor. These studies support the translational viability of the HSV-1 0ΔNLS vaccine strain by demonstrating that, while it is comparable to a virulent parental strain in terms of immunogenicity, HSV-1 0ΔNLS does not induce significant tissue pathology. IMPORTANCE HSV-1 is a common human pathogen associated with a variety of clinical presentations ranging in severity from periodic “cold sores” to lethal encephalitis. Despite the consistent failures of HSV subunit vaccines in clinical trials spanning the past 28 years, opposition to live-attenuated HSV vaccines predicated on unfounded safety concerns currently limits their widespread acceptance. Here, we demonstrate that a live-attenuated HSV-1 vaccine has great translational potential.

Correlates of immunologic protection requisite for an efficacious herpes simplex virus 1 (HSV-1) vaccine remain unclear with respect to viral pathogenesis and clinical disease. In the present study, mice were vaccinated with a novel avirulent, live attenuated virus (0ΔNLS) or an adjuvanted glycoprotein D subunit (gD-2) similar to that used in several human clinical trials. Mice vaccinated with 0ΔNLS showed superior protection against early viral replication, neuroinvasion, latency, and mortality compared to that of gD-2-vaccinated or naive mice following ocular challenge with a neurovirulent clinical isolate of HSV-1. Moreover, 0ΔNLS-vaccinated mice exhibited protection against ocular immunopathology and maintained corneal mechanosensory function. Vaccinated mice also showed suppressed T cell activation in the draining lymph nodes following challenge. Vaccine efficacy correlated with serum neutralizing antibody titers. Humoral immunity was identified as the correlate of protection against corneal neovascularization, HSV-1 shedding, and latency through passive immunization. Overall, 0ΔNLS affords remarkable protection against HSV-1-associated ocular sequelae by impeding viral replication, dissemination, and establishment of latency. IMPORTANCE HSV-1 manifests in a variety of clinical presentations ranging from a rather benign “cold sore” to more severe forms of infection, including necrotizing stromal keratitis and herpes simplex encephalitis. The present study was undertaken to evaluate a novel vaccine to ocular HSV-1 infection not only for resistance to viral replication and spread but also for maintenance of the visual axis. The results underscore the necessity to reconsider strategies that utilize attenuated live virus as opposed to subunit vaccines against ocular HSV-1 infection.

Type I IFN (IFN-α/β)–driven immune responses to acute viral infection are critical to counter replication and prevent dissemination. However, the mechanisms underlying host resistance to HSV type 1 (HSV-1) are incompletely understood. In this study, we show that mice with deficiencies in IFN-α/β signaling or stimulator of IFN genes (STING) exhibit exacerbated neurovirulence and atypical lymphotropic dissemination of HSV-1 following ocular infection. Synergy between IFN-α/β signaling and efficacy of early adaptive immune responses to HSV-1 were dissected using bone marrow chimeras and adoptive cell transfer approaches to profile clonal expansion, effector function, and recruitment of HSV-specific CD8+ T cells. Lymphotropic viral dissemination was commensurate with abrogated CD8+ T cell responses and pathological alterations of fibroblastic reticular cell networks in the draining lymph nodes. Our results show that resistance to HSV-1 in the trigeminal ganglia during acute infection is conferred in part by STING and IFN-α/β signaling in both bone marrow–derived and –resident cells, which coalesce to support a robust HSV-1–specific CD8+ T cell response.

Purpose To explore the impact of ocular surface insults on the immunomodulatory capacity and phenotype of corneal epithelial cells (CECs) with a focus on epithelial-mesenchymal transition (EMT). Methods Corneas were harvested from mice 6 days following scratch injury, ragweed pollen-induced allergy, or herpes simplex virus type 1 (HSV-1) infection and compared to healthy tissue controls. Corneas were enzymatically digested and CECs phenotypically characterized using flow cytometry. CECs were defined as epithelial cell adhesion molecule (EpCAM)-positive CD45-negative cells. CECs were assessed by PCR to evaluate EMT-associated transcripts. Recombinant HSV-1 and transgenic mice were utilized to investigate the role of vascular endothelial growth factor A (VEGFA) on the phenotype observed. The immunomodulatory potential of CECs was assessed in coculture assays with ovalbumin-specific CD4 T cells. Results Ectopic expression of classic "myeloid" antigens Ly6G, CCR2, and CX3CR1 was identified in CEC subsets from all groups with evidence supporting an underlying partial EMT event resulting from loss of cell-cell contacts. Corneal HSV-1 infection induced Ly6C expression and major histocompatibility complex (MHC)-II upregulation in CECs through a VEGFA-linked mechanism. These Ly6C+ MHC-II+ CECs were found to function as amateur antigen-presenting cells and induced CD4 T cell proliferation in vitro. Conclusions This study characterizes a novel immunomodulatory CEC phenotype with possible implications for immune privilege, chronic inflammation, and tissue fibrosis. Moreover, the identification of CECs masquerading with multiple "myeloid" antigens warrants careful evaluation of flow cytometry data involving corneal digests.

Type 1 interferons (IFNs; IFNα/β) mediate immunological host resistance to numerous viral infections, including herpes simplex virus type 1 (HSV-1). The pathways responsible for IFNα/β signaling during the innate immune response to acute HSV-1 infection in the cornea are incompletely understood. Using a murine ocular infection model, we hypothesized that the stimulator of IFN genes (STING) mediates resistance to HSV-1 infection at the ocular surface and preserves the structural integrity of this mucosal site. Viral pathogenesis, tissue pathology, and host immune responses during ocular HSV-1 infection were characterized by plaque assay, esthesiometry, pachymetry, immunohistochemistry, flow cytometry, and small interfering RNA transfection in wild-type C57BL/6 (WT), STING-deficient (STING(-/-)), and IFNα/β receptor-deficient (CD118(-/-)) mice at days 3-5 postinfection. The presence of STING was critical for sustained control of HSV-1 replication in the corneal epithelium and resistance to viral neuroinvasion, but loss of STING had a negligible impact with respect to gross tissue pathology. Auxiliary STING-independent IFNα/β signaling pathways were responsible for maintenance of corneal integrity. Lymphatic vessels, mast cells, and sensory innervation were compromised in CD118(-/-) mice concurrent with increased tissue edema. STING-dependent signaling led to the upregulation of tetherin, a viral restriction factor we identify is important in containing the spread of HSV-1 in vivo.

Immunizing events including pregnancy, transfusions, and transplantation promote strong alloantibody responses to HLA. Such alloantibodies to HLA preclude organ transplantation, foster hyperacute rejection, and contribute to chronic transplant failure. Diagnostic antibody-screening assays detect alloreactive antibodies, yet key attributes including antibody concentration and isotype remain largely unexplored. The goal here was to provide a detailed profile of allogeneic antibodies to class II HLA. Methodologically, alloantibodies were purified from sensitized patient sera using an HLA-DR11 immunoaffinity column and subsequently categorized. Antibodies to DR11 were found to fix complement, exist at a median serum concentration of 2.3 μg/mL, consist of all isotypes, and isotypes IgG2, IgM, and IgE were elevated. Because multimeric isotypes can confound diagnostic determinations of antibody concentration, IgM and IgA isotypes were removed and DR11-IgG tested alone. Despite removal of multimeric isotypes, patient-to-patient antibody concentrations did not correlate with MFI values. In conclusion, allogeneic antibody responses to DR11 are comprised of all antibody isotypes at differing proportions, these combined isotypes fix complement at nominal serum concentrations, and enhancements other than the removal of IgM and IgA multimeric isotypes may be required if MFI is to be used as a means of determining anti-HLA serum antibody concentrations in diagnostic clinical assays.

Background: Thrombocytopenia is a well-recognized adverse effect of many drugs. However, the association of thrombocytopenia with complementary ⁄alternative medicines, herbal remedies, nutritional supplements, foods, and beverages has been rarely described, except for reports of thrombocytopenia caused by quinine-containing beverages. Objectives: To systematically identify all published reports of thrombocytopenia associated with these substances and to assess the evidence supporting their causal association with thrombocytopenia. Methods: Eleven databases were searched to identify relevant published reports. A priori criteria were defined for article selection and assessment. Each selected article was independently assessed by the three authors to document the presence of the criteria and determine the level of evidence for a causal association of the reported substance with thrombocytopenia. Results: Twenty-seven articles were identified that reported the occurrence of thrombocytopenia with 25 substances (other than quinine). However, only six articles describing five substances (cow’s milk, cranberry juice, Jui [Chinese herbal tea], Lupinus termis bean, and tahini [pulped sesame seeds]) reported clinical data supporting definite evidence of a causal association with thrombocytopenia. Four articles provided probable evidence for four additional substances, and five articles provided possible evidence for five additional substances. In the remaining articles, the association with thrombocytopenia was unlikely or the articles were excluded from review. Conclusions: Reports of thrombocytopenia describing definite or probable evidence for an association of a complementary ⁄alternative medicines, herbal remedies, nutritional supplements, foods, and beverages are rare. Whether the occurrence of thrombocytopenia with these substances is uncommon or unrecognized is unknown.

Herpes simplex virus type-1 (HSV-1) is a neurotropic double-stranded DNA virus with significant clinical interest due to its endemic nature, life-long persistence, and status as the leading cause of infectious corneal blindness.1,2 The global burden of corneal HSV-1 infection is estimated to be 1.5 million annual occurrences including 40,000 new cases of severe monocular visual impairment or blindness.3 More than 60% of the human population is infected with and harbors latent HSV-1 in neuronal ganglia.2,4,5 Periodic reactivation of HSV-1 facilitates shedding of infectious progeny in external mucosae innervated by infected neurons, often resulting in herpes labialis (i.e., cold sores) or ocular herpes keratitis.2,6 Farooq et al.7 have reviewed the mechanisms of HSV-1 cell entry and spread in the eye. Intermittent but recurrent HSV-1 reactivation in the cornea contributes to the development of herpes stromal keratitis (HSK), a blinding immunopathology characterized by inflammation, scarring, and neovascularization.2,3 Investigating processes of immune surveillance and innate countermeasures during the earliest stages of infection is important to better understand HSV-1 pathogenesis, focus development of novel therapeutics, and ultimately prevent HSK. The innate immune response to HSV-1 infection in the cornea is multifactorial. It is abundantly clear that type-1 IFN-α/β signaling in both resident cells and infiltrating leukocytes is required for control of HSV-1.8 Due to the avascular nature of the normal cornea, circulating leukocytes must extravasate from blood vessels surrounding the cornea in the limbus and migrate through the tissue in accordance with the local milieu of inflammatory mediators (i.e., cytokines, chemokines, eicosanoids, etc.) following injury or pathogenic insult.9–12 Acute corneal HSV-1 infection provokes a potent influx of innate leukocytes including inflammatory monocytes, macrophages, natural killer (NK) cells, and neutrophils (PMNs). Of these responders, inflammatory monocytes contribute to virus clearance during the first 48 hours post infection (pi).8 Conversely, current evidence suggests that PMNs are not responsible for HSV-1 clearance.13,14 Resident and perhaps infiltrating dendritic cells also respond to HSV-1 infection or regulate the activity of other leukocytes in the cornea.15 In addition to resident dendritic cells, an often overlooked bone marrow–derived cell residing in the mucosa of the external eye is the mast cell (MC).16 Mast cells are long-lived radioresistant granulocytes strategically localized in tissues exposed to the external environment to facilitate pathogen surveillance.17,18 Mast cells express an armament of innate sensors to accommodate this protective role.18 Upon stimulation, MCs undergo rapid degranulation of cytoplasmic granules containing preformed proteases and potent vasoactive mediators including histamine and TNFα . Following degranulation, MCs produce many soluble factors de novo to fine-tune subsequent innate and adaptive responses.17,18 The scope and functional diversity of immunomodulatory mast cell granule products have recently been reviewed by Wernersson and Pejler.19 Though the activities attributed to MCs in general are broad, it is recognized that the MC phenotype and products are regulated in a niche- and stimulus-specific manner.19,20 Mast cells have been implicated in the maintenance of immune privilege and contribute to pathogen surveillance and defense in various anatomic sites including the skin, lung, bladder, and gut.18,19,21,22 In the human host, MCs reside in an organized fashion within the eye-associated lymphoid tissue including the lacrimal gland, limbus, and conjunctiva.23–25 Whereas the contributions of ocular MCs are appreciated in IgE-mediated allergic conjunctivitis, they have not been investigated with respect to pathogen defense in the eye. In the present article, we hypothesized MCs are involved in the innate immune response to ocular HSV-1 infection due to their proximity to the cornea and immunomodulatory potential. Mice deficient in MCs were found to be more sensitive to HSV-1 infection, but counterintuitively exhibited greater corneal edema. Collectively, our results underscore a novel role for MCs in the eye as an innate sentinel against acute HSV-1 infection by promoting virus clearance and limiting inflammation to preserve the visual axis. We also found that MCs serve as a type of gatekeeper in the corneal vasculature. Imbalances in eicosanoid mediators are implicated in increased corneal PMN infiltration and inflammation in KitW-sh mice. Neutrophils were identified as surrogates for HSV-1 replication using in vivo, in vitro, and adoptive cell transfer approaches. Lastly, we establish that myeloid-derived suppressor cells (MDSC) do not compromise the use of KitW-sh mice in our model investigating the impact of MCs on the innate and early adaptive immune response to acute HSV-1 infection.

Herpes simplex virus type 1 (HSV-1) is a prevalent human pathogen worldwide. HSV-1 remains lytic and resists entry into latency within neurons of the trigeminal ganglia (TG) in the absence of type I interferon (IFN). However, the immunologic mechanisms involved in clearing lytic virus in the TG during primary infection remain poorly defined. HSV-1 is able to develop progeny virus during primary infection in the TG, suggesting that the establishment of HSV-1 latency is not simply due to infection of a non-permissive neuron. To address this issue, the immune response to HSV-1 in the TG was examined in a murine model of ocular infection. Viral titer and leukocyte infiltration in TG were surveyed in bone marrow (BM) chimeras generated from C57BL/6 wildtype (WT) mice and mice deficient in the type I IFN receptor alpha chain (CD118 −/− ) to determine the contribution of type I IFN signaling in resident and BM-derived cells. Data show that both resident and BM-derived cells contribute to type I IFN-mediated clearance of lytic virus within the TG. Moreover, HSV-1 titers correlated inversely with infiltrating NK cells, CD8 + T cells and HSV-specific CD8 + T cells. These results were supported by the observation that gBT-I.1 TCR transgenic mice in which CD8 + T cells are specific for the immunodominant epitope of HSV-1 glycoprotein B have significantly less virus in the TG compared to WT following infection. CD8 T cell depletion at the site of infection showed a trend towards increased virus in the TG and systemic depletion is currently being pursued. Infection of WT and STING-deficient mouse TG in situ revealed that the innate sensing pathway critical for production of type I IFN in peripheral tissues is dispensable in the TG. Understanding the immune response to lytic HSV-1 infection in the TG is critical for rational prophylactic HSV-1 vaccine design.