Multiple entry receptors can mediate infection of cells by herpes simplex virus (HSV), permitting alternative pathways for infection and disease. We investigated the roles of two known entry receptors, herpesvirus entry mediator (HVEM) and nectin-1, in infection of neurons in the CNS and the development of encephalitis. Wild-type, HVEM KO, nectin-1 KO, and HVEM/nectin-1 double KO mice were inoculated with HSV into the hippocampus. The mice were examined for development of encephalitis or were killed at various times after inoculation for immunohistological analyses of brain slices. Nectin-1 KO mice showed no signs of disease after intracranial inoculation, and no HSV antigens were detectable in the brain parenchyma. However, HSV antigens were detected in non-parenchymal cells lining the ventricles. In the double KO mice, there was also no disease and no detectable expression of viral antigens even in non-parenchymal cells, indicating that infection of these cells in the nectin-1 KO mice was dependent on the expression of HVEM. Wild-type and HVEM KO mice rapidly developed encephalitis, and the patterns of HSV replication in the brain were indistinguishable. Thus, expression of nectin-1 is necessary for HSV infection via the intracranial route and for encephalitis; HVEM is largely irrelevant. These results contrast with recent findings that (i) either HVEM or nectin-1 can permit HSV infection of the vaginal epithelium in mice and (ii) nectin-1 is not the sole receptor capable of enabling spread of HSV infection from the vaginal epithelium to the PNS and CNS.HSV ͉ pathogenesis W e have undertaken studies to determine whether the various aspects of disease caused by herpes simplex virus (HSV) are critically dependent on the same or different entry receptors. The usual manifestations of HSV disease in humans, the natural host, are perioral or genital lesions of the skin or mucosa or lesions on the cornea. The virus can spread from epithelial cells to neurons and establish latent infections in sensory and autonomic ganglia. Rarely, the virus also spreads to the CNS to cause encephalitis or meningitis (1).Mice can be infected by HSV with manifestations of disease similar to those found in humans. In addition, the mouse entry receptors for HSV are paralogs of the human entry receptors (2). Thus, mice and mice mutated for specific HSV entry receptors provide excellent models for the study of HSV entry requirements in disease.Binding of HSV to either mouse or human cells can be mediated by interactions of virion envelope glycoproteins gB or gC with cell surface heparan sulfate (3). These interactions are not sufficient for viral entry. Entry requires the binding of at least two envelope glycoproteins, both gD and gB, to specific cell surface receptors (4, 5). These interactions activate the fusogenic activity of gB, a homotrimer, and/or gH-gL, a heterodimer, resulting in fusion of the virion envelope with a cell membrane (6, 7).There are multiple alternative gD receptors, including herpesvirus entry mediator (HVEM), necti...

Background and Purpose-Recent measurements in intracerebral hemorrhage (ICH) patients suggest a primary reduction in brain metabolism is responsible for reduced cerebral blood flow and low oxygen extraction surrounding the hematoma. We sought to determine whether reduced mitochondrial respiratory function could account for reduced metabolic demand in ICH patients. Methods-Brain-tissue samples from 6 patients with acute spontaneous ICH and 6 control patients undergoing brain resection for management of seizure were evaluated. Only tissue removed from the brain adjacent to the hematoma was studied. Specimens were collected in the operating room; mitochondrial studies were begun within 1-hour. Mitochondrial oxygen consumption was measured after the addition of pyruvate, malate, and ADP, followed by oligomycin and carbonylcyanide. Results-The ICH patients ranged in age from 40 to 54 years; 2 were female and half black. Hemorrhages were located in the temporal lobe (3), cerebellum (2) and parietal lobe (1).

Herpes simplex virus 1 (HSV-1) is a ubiquitous human pathogen that enters cells by the receptor-mediated fusion of the viral envelope with a host cell membrane. The envelope glycoprotein gD of HSV must bind to one of its receptors for entry to take place. Recent studies using knockout (KO) mice demonstrated that the gD receptors herpesvirus entry mediator (HVEM) and nectin-1 are the primary entry receptors for HSV-2 in the mouse vagina and brain. Nectin-1 was most crucial for the neuronal spread of HSV-2, particularly in the brain. HVEM was dispensable for infection in these models, but when both HVEM and nectin-1 were absent, infection was completely prevented. We sought to determine the receptor requirements of HSV-1 in an ocular model of infection using knockout mice. Wild-type, HVEM KO, nectin-1 KO, and HVEM/nectin-1 double-KO mice were infected via corneal scarification and monitored for clinical signs of infection and viral replication in various tissues. We report that either HVEM or nectin-1 must be present for HSV-1 infection of the cornea. Additionally, we observed that the infection was attenuated in both HVEM KO and nectin-1 KO mice. This is in contrast to what was reported for studies of HSV-2 in vagina and brain and suggests that receptor requirements for HSV vary depending on the route of inoculation and/or serotype.Herpes simplex virus 1 (HSV-1), an alphaherpesvirus, is the leading cause of infectious blindness in developed countries (12). Infection begins in peripheral epithelial tissues, including the oral mucosal, skin, or corneal epithelium. After replicating in the epithelium, the virus infects adjacent neurons and travels via retrograde transport to sensory ganglia, including the trigeminal ganglia (TG) (1). In nerve cell bodies HSV is able to establish a life-long latent infection and reactivate at a later point or immediately undergo additional rounds of replication. During replication in neurons the virus can transit back down axons and reinfect the site of inoculation. HSV is also capable of spreading, in a zosteriform manner, to other peripheral tissues innervated by neurons from the infected ganglia. In rare cases in humans the virus can spread to the brain and cause encephalitis (7). HSV-1 is the predominant cause of ocular herpes infections and usually begins as conjunctivitis or epithelial keratitis. The reactivation of the virus can lead to subsequent damage to the cornea and stromal keratitis. This outcome depends on a variety of host and viral factors but often leads to blindness (2).The infectious cycle of HSV-1 begins when the virion envelope fuses with a host cell membrane either at the plasma membrane or in endocytic vesicles. Fusion is a complex process that requires multiple glycoproteins, including gD, gB, and the heterodimeric complex gH/gL (4). While the precise function of each glycoprotein remains unclear, it is well accepted that gD must bind to a gD receptor on the host cell for efficient entry. Several gD receptors have been identified, including herpesvirus entry ...

The cellular proteins nectin-1 and herpesvirus entry mediator (HVEM) can both mediate the entry of herpes simplex virus 1 (HSV-1). We have recently shown how these receptors contribute to infection of skin by investigating HSV-1 entry into murine epidermis. Ex vivo infection studies reveal nectin-1 as the primary receptor in epidermis, whereas HVEM has a more limited role. Although the epidermis represents the outermost layer of skin, the contribution of nectin-1 and HVEM in the underlying dermis is still open. Here, we analyzed the role of each receptor during HSV-1 entry in murine dermal fibroblasts that were deficient in expression of either nectin-1 or HVEM or both receptors. Because infection was not prevented by the absence of either nectin-1 or HVEM, we conclude that they can act as alternative receptors. Although HVEM was found to be highly expressed on fibroblasts, entry was delayed in nectin-1-deficient cells, suggesting that nectin-1 acts as the more efficient receptor. In the absence of both receptors, entry was strongly delayed leading to a much reduced viral spread and virus production. These results suggest an unidentified cellular component that acts as alternate but inefficient receptor for HSV-1 on dermal fibroblasts. Characterization of the cellular entry mechanism suggests that HSV-1 can enter dermal fibroblasts both by direct fusion with the plasma membrane and via endocytic vesicles and that this is not dependent on the presence or absence of nectin-1. Entry was also shown to require dynamin and cholesterol, suggesting comparable entry pathways in keratinocytes and dermal fibroblasts. IMPORTANCEHerpes simplex virus (HSV) is a human pathogen which infects its host via mucosal surfaces or abraded skin. To understand how HSV-1 overcomes the protective barrier of mucosa or skin and reaches its receptors in tissue, it is essential to know which receptors contribute to the entry into individual skin cells. Previously, we have explored the contribution of nectin-1 and herpesvirus entry mediator (HVEM) as receptors for HSV-1 entry into murine epidermis, where keratinocytes form the major cell type. Since the underlying dermis consists primarily of fibroblasts, we have now extended our study of HSV-1 entry to dermal fibroblasts isolated from nectin-1-or HVEM-deficient mice or from mice deficient in both receptors. Our results demonstrate a role for both nectin-1 and HVEM as receptors and suggest a further receptor which appears much less efficient.T o initiate infection, herpes simplex virus 1 (HSV-1) enters its human host via mucosal surfaces or abraded skin. HSV-1 entry into individual cells involves the interaction of several viral glycoproteins with various cell surface receptors (1, 2). The first step during entry is the attachment of virions to glycosaminoglycans, which facilitates the interaction with cellular receptors, leading to the fusion of the viral envelope with a cellular membrane. Fusion can either occur with the plasma membrane or with vesicle membranes after virions are int...

PurposeTo determine cellular and temporal expression patterns of herpes virus entry mediator (HVEM, Tnfrsf14) in the murine cornea during the course of herpes simplex virus 1 (HSV-1) infection, the impact of this expression on pathogenesis, and whether alterations in HVEM or downstream HVEM-mediated effects ameliorate corneal disease.MethodsCorneal HVEM levels were assessed in C57BL/6 mice after infection with HSV-1(17). Leukocytic infiltrates and corneal sensitivity loss were measured in the presence, global absence (HVEM knockout [KO] mice; Tnfrsf14−/−), or partial absence of HVEM (HVEM conditional KO). Effects of immune-modifying nanoparticles (IMPs) on viral replication, corneal sensitivity, and corneal infiltrates were measured.ResultsCorneal HVEM+ populations, particularly monocytes/macrophages during acute infection (3 days post infection [dpi]) and polymorphonuclear neutrophils (PMN) during the chronic inflammatory phase (14 dpi), increased after HSV-1 infection. Herpes virus entry mediator increased leukocytes in the cornea and corneal sensitivity loss. Ablation of HVEM from CD45+ cells, or intravenous IMP therapy, reduced infiltrates in the chronic phase and maintained corneal sensitivity.ConclusionsHerpes virus entry mediator was expressed on two key populations: corneal monocytes/macrophages and PMNs. Herpes virus entry mediator promoted the recruitment of myeloid cells to the cornea in the chronic phase. Herpes virus entry mediator–associated corneal sensitivity loss preceded leukocytic infiltration, suggesting it may play an active role in recruitment. We propose that HVEM on resident corneal macrophages increases nerve damage and immune cell invasion, and we showed that prevention of late-phase infiltration of PMN and CD4+ T cells by IMP therapy improved clinical symptoms and mortality and reduced corneal sensitivity loss caused by HSV-1.