Herpes Simplex Virus Pathogenesis Research Articles

Animal models of herpes simplex virus immunity and pathogenesis.

Herpes simplex viruses are ubiquitous human pathogens represented by two distinct serotypes: herpes simplex virus (HSV) type 1 (HSV-1); and HSV type 2 (HSV-2). In the general population, adult seropositivity rates approach 90% for HSV-1 and 20-25% for HSV-2. These viruses cause significant morbidity, primarily as mucosal membrane lesions in the form of facial cold sores and genital ulcers, with much less common but more severe manifestations causing death from encephalitis. HSV infections in humans are difficult to study in many cases because many primary infections are asymptomatic. Moreover, the neurotropic properties of HSV make it much more difficult to study the immune mechanisms controlling reactivation of latent infection within the corresponding sensory ganglia and crossover into the central nervous system of infected humans. This is because samples from the nervous system can only be routinely obtained at the time of autopsy. Thus, animal models have been developed whose use has led to a better understanding of multiple aspects of HSV biology, molecular biology, pathogenesis, disease, and immunity. The course of HSV infection in a spectrum of animal models depends on important experimental parameters including animal species, age, and genotype; route of infection; and viral serotype, strain, and dose. This review summarizes the animal models most commonly used to study HSV pathogenesis and its establishment, maintenance, and reactivation from latency. It focuses particularly on the immune response to HSV during acute primary infection and the initial invasion of the ganglion with comparisons to the events governing maintenance of viral latency.

Review of clinical and basic approaches to corneal endotheliitis.

Corneal endotheliitis was first reported as an autoimmune disease by Khodadoust in 1982. Thereafter, herpes simplex virus (HSV) was detected as a causative agent, and corneal endotheliitis was classified as an infectious disease. However, most primary corneal endotheliitis had been idiopathic. In 2006, cytomegalovirus (CMV) DNA was detected in a case of corneal endotheliitis, and other reports on CMV endotheliitis from Asian countries established it as a new clinical entity. Limited studies have reported clinical findings, and the pathogenesis of HSV and CMV corneal endotheliitis is unknown. Therefore, this review describes what is currently known about the pathogenesis of HSV and CMV endotheliitis by way of previously reported case studies and basic research. In addition, we review work by our own group regarding the role of Toll-like receptor 9 and the results of transcriptome analysis after HSV infection in an in vitro model using immortalized human corneal endothelial cells. It is critical to diagnose corneal endotheliitis early to provide effective treatment with ganciclovir or valganciclovir and prevent the loss of corneal endothelial cells. Therefore, we hope that these in vitro results may provide further information to help elucidate the in vivo pathogenesis of HSV and CMV endotheliitis.

Direct activation of RIP3/MLKL-dependent necrosis by herpes simplex virus 1 (HSV-1) protein ICP6 triggers host antiviral defense.

The receptor-interacting kinase-3 (RIP3) and its downstream substrate mixed lineage kinase domain-like protein (MLKL) have emerged as the key cellular components in programmed necrotic cell death. Receptors for the cytokines of tumor necrosis factor (TNF) family and Toll-like receptors (TLR) 3 and 4 are able to activate RIP3 through receptor-interacting kinase-1 and Toll/IL-1 receptor domain-containing adapter inducing IFN-β, respectively. This form of cell death has been implicated in the host-defense system. However, the molecular mechanisms that drive the activation of RIP3 by a variety of pathogens, other than the above-mentioned receptors, are largely unknown. Here, we report that human herpes simplex virus 1 (HSV-1) infection triggers RIP3-dependent necrosis. This process requires MLKL but is independent of TNF receptor, TLR3, cylindromatosis, and host RIP homotypic interaction motif-containing protein DNA-dependent activator of IFN regulatory factor. After HSV-1 infection, the viral ribonucleotide reductase large subunit (ICP6) interacts with RIP3. The formation of the ICP6-RIP3 complex requires the RHIM domains of both proteins. An HSV-1 ICP6 deletion mutant failed to cause effective necrosis of HSV-1-infected cells. Furthermore, ectopic expression of ICP6, but not RHIM mutant ICP6, directly activated RIP3/MLKL-mediated necrosis. Mice lacking RIP3 exhibited severely impaired control of HSV-1 replication and pathogenesis. Therefore, this study reveals a previously uncharacterized host antipathogen mechanism.

Current thinking on genital herpes

Genital herpes has a high global prevalence and burden of disease. This manuscript highlights recent advances in our understanding of genital herpes simplex virus (HSV) infections. Studies demonstrate a changing epidemiological landscape with an increasing proportion of genital herpes cases associated with HSV type 1. There is also growing evidence that the majority of infected individuals exhibit frequent, brief shedding episodes that are most often asymptomatic, which likely contribute to high HSV transmission rates. Given this finding as well as readily available serological assays, some have proposed that routine HSV screening be performed; however, this remains controversial and is not currently recommended. Host immune responses, particularly local CD4 and CD8 T cell activity, are crucial for HSV control and clearance following initial infection, during latency and after reactivation. Prior HSV immunity may also afford partial protection against HSV reinfection and disease. Although HSV vaccine trials have been disappointing to date and existing antiviral medications are limited, novel prophylactic and therapeutic modalities are currently in development. Although much remains unknown about genital herpes, improved knowledge of HSV epidemiology, pathogenesis and host immunity may help guide new strategies for disease prevention and control.

Synergistic control of herpes simplex virus pathogenesis by IRF-3, and IRF-7 revealed through non-invasive bioluminescence imaging

Interferon regulatory factors IRF-3 and IRF-7 are central to the establishment of the innate antiviral response. This study examines HSV-1 pathogenesis in IRF-3−/−, IRF-7−/− and double-deleted IRF3/7−/− (DKO) mice. Bioluminescence imaging of infection revealed that DKO mice developed visceral infection following corneal inoculation, along with increased viral burdens in all tissues relative to single knockout mice. While all DKO mice synchronously reached endpoint criteria 5 days post infection, the IRF-7−/− mice survived longer, indicating that although IRF-7 is dominant, IRF-3 also plays a role in controlling disease. Higher levels of systemic pro-inflammatory cytokines were found in IRF7−/− and DKO mice relative to wild-type and IRF-3−/− mice, and IL-6 and G-CSF, indicative of sepsis, were increased in the DKO mice relative to wild-type or single-knockout mice. In addition to controlling viral replication, IRF-3 and -7 therefore play coordinating roles in modulation of inflammation during HSV infection.

50 Years Ago in The Journal of Pediatrics: Latent Virus Infection: Recurrent Herpes Simplex

Blattner RJ. J Pediatr 1961;59:784-6 In the section of The Journal “Comments on Current Literature,” Blattner gives a glimpse of the “state-of-the-thinking” on pathogenesis of herpes simplex virus (HSV) infections. Investigators and “thinkers” at the time had so much of it right (ie, most primary HSV infections are subclinical, yet whether clinical or subclinical, infection leads to establishment of latency and cycles of reactivation in most people). Presence of antibody does not prevent superficial recurrences (reactivations), which sometimes take on “zosteriform” characteristics by following nerve distribution. Investigators and clinicians even recognized (and made experimental models in animals to prove) some triggers of reactivation. One thing that they didn’t have quite right was the risk factors for occurrence of HSV encephalitis beyond the neonatal period. They thought that encephalitis would occur only with primary HSV infection and likely was associated with particularly neurotropic strains of HSV, neither of which is true. We now know that the host, rather than the virus, probably has the relevant influence on events. Abel et al have studied extensively and presented evidence that HSV encephalitis beyond the neonatal period, seemingly a rare but sporadic event, is not “bad luck” or “bad bug,” but is attributable at least in part to one or more organism-specific host innate immune defects.1Abel L. Plancoulaine S. Jouanguy E. et al.Age-dependent Mendelian predisposition to herpes simplex virus type 1 encephalitis in childhood.J Pediatr. 2010; 157: 623-629Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar

Effects of Phosphorylation of Herpes Simplex Virus 1 Envelope Glycoprotein B by Us3 Kinase In Vivo and In Vitro

We recently reported that the herpes simplex virus 1 (HSV-1) Us3 protein kinase phosphorylates threonine at position 887 (Thr-887) in the cytoplasmic tail of envelope glycoprotein B (gB) (A. Kato, J. Arii, I. Shiratori, H. Akashi, H. Arase, and Y. Kawaguchi, J. Virol. 83:250-261, 2009; T. Wisner, C. C. Wright, A. Kato, Y. Kawaguchi, F. Mou, J. D. Baines, R. J. Roller and D. C. Johnson, J. Virol. 83:3115-3126, 2009). In the studies reported here, we examined the effect(s) of this phosphorylation on viral replication and pathogenesis in vivo and present data showing that replacement of gB Thr-887 by alanine significantly reduced viral replication in the mouse cornea and development of herpes stroma keratitis and periocular skin disease in mice. The same effects have been reported for mice infected with a recombinant HSV-1 carrying a kinase-inactive mutant of Us3. These observations suggested that Us3 phosphorylation of gB Thr-887 played a critical role in viral replication in vivo and in HSV-1 pathogenesis. In addition, we generated a monoclonal antibody that specifically reacted with phosphorylated gB Thr-887 and used this antibody to show that Us3 phosphorylation of gB Thr-887 regulated subcellular localization of gB, particularly on the cell surface of infected cells.

HSV ICP0 recruits USP7 to modulate TLR-mediated innate response

AbstractPattern recognition receptors represent the first line of defense against invading pathogens. Herpes simplex virus (HSV) encodes multiple ligands detected by these receptors, yet persists in the majority of infected individuals indicating a breakdown in host defense against the virus. Here we identify a novel mechanism through which HSV immediate-early protein ICP0 inhibits TLR-dependent inflammatory response by blocking NF-κB and JNK activation downstream of TLR signal activation. This process depends on ICP0-mediated translocation of USP7 (HAUSP) from the nucleus to cytoplasm. We show that nuclear USP7 migrates to the cytoplasm in response to TLR engagement, a process that contributes to termination of TLR response. Cytoplasmic USP7 binds to and deubiquitinates TRAF6 and IKKγ, thus terminating TLR-mediated NF-κB and JNK activation. These findings suggest that USP7 is part of a negative feedback loop regulating TLR signaling and that ICP0 exploits this physiologic process to attenuate innate response to HSV. ICP0 inhibition of the TLR response serves to uncouple the innate and adaptive immune response, thereby playing a key role in HSV pathogenesis and persistence.

Regulation of the Catalytic Activity of Herpes Simplex Virus 1 Protein Kinase Us3 by Autophosphorylation and Its Role in Pathogenesis

Us3 is a serine/threonine protein kinase encoded by herpes simplex virus 1 (HSV-1). We recently identified serine at Us3 position 147 (Ser-147) as a physiological phosphorylation site of Us3 (A. Kato, M. Tanaka, M. Yamamoto, R. Asai, T. Sata, Y. Nishiyama, and Y. Kawaguchi, J. Virol. 82:6172-6189, 2008). In the present study, we investigated the effects of phosphorylation of Us3 Ser-147 on regulation of Us3 catalytic activity in infected cells and on HSV-1 pathogenesis. Our results were as follows. (i) Only a small fraction of Us3 purified from infected cells was phosphorylated at Ser-147. (ii) Us3 phosphorylated at Ser-147 purified from infected cells had significantly higher kinase activity than Us3 not phosphorylated at Ser-147. (iii) Phosphorylation of Us3 Ser-147 in infected cells was dependent on Us3 kinase activity. (iv) Replacement of Us3 Ser-147 by alanine significantly reduced viral replication in the mouse cornea and the development of herpes stromal keratitis and periocular skin disease in mice. These results indicated that Us3 catalytic activity is tightly regulated by autophosphorylation of Ser-147 in infected cells and that regulation of Us3 activity by autophosphorylation appeared to play a critical role in viral replication in vivo and in HSV-1 pathogenesis.

Keratin, a dual role in herpes simplex virus pathogenesis

Keratin is a strong, fibrous protein that coats the skin, male genitalia and some tissues in the mouth and female genitalia. Keratin protects the host by providing a barrier against primary herpes simplex virus infection. We postulate that keratin may also hinder the host by protecting the virus from effective immune responses such as those present on mucosal surfaces, enabling recurrent lesions to preferentially develop within keratinized tissues at mucocutaneous junctions. The natural history of infection supports the importance of preventing infection in keratinized tissues for developing an effective herpes simplex virus vaccine, since potent immunity on mucosal surfaces may be inadequate to protect keratinized tissues.

Replication of herpes simplex virus 1 depends on the gamma 134.5 functions that facilitate virus response to interferon and egress in the different stages of productive infection.

The ability of the gamma(1)34.5 protein to suppress the PKR response plays a crucial role in herpes simplex virus pathogenesis. In this process, the gamma(1)34.5 protein associates with protein phosphatase 1 to form a large complex that dephosphorylates eIF-2alpha and thereby prevents translation shutoff mediated by PKR. Accordingly, gamma(1)34.5 null mutants are virulent in PKR-knockout mice but not in wild-type mice. However, gamma(1)34.5 deletion mutants, with an extragenic compensatory mutation, inhibit PKR activity but remain avirulent, suggesting that the gamma(1)34.5 protein has additional functions. Here, we show that a substitution of the gamma(1)34.5 gene with the NS1 gene from influenza A virus renders viral resistance to interferon involving PKR. The virus replicates as efficiently as wild-type virus in SK-N-SH and CV-1 cells. However, in mouse 3T6 cells, the virus expressing the NS1 protein grows at an intermediate level between the wild-type virus and the gamma(1)34.5 deletion mutant. This decrease in growth, compared to that of the wild-type virus, is due not to an inhibition of viral protein synthesis but rather to a block in virus release or egress. Virus particles are predominantly present in the nucleus and cytoplasm. Notably, deletions in the amino terminus of the gamma(1)34.5 protein lead to a significant decrease in virus growth in mouse 3T6 cells, which is independent of eIF-2alpha dephosphorylation. In correlation, a series of deletions in the amino-terminal domain impair nuclear as well as cytoplasmic egress. These results indicate that efficient viral replication depends on the gamma(1)34.5 functions required to prevent the PKR response and to facilitate virus egress in the different stages during virus infection.

Persistent expression of chemokine and chemokine receptor RNAs at primary and latent sites of herpes simplex virus 1 infection

Inflammatory cytokines and infiltrating T cells are readily detected in herpes simplex virus (HSV) infected mouse cornea and trigeminal ganglia (TG) during the acute phase of infection, and certain cytokines continue to be expressed at lower levels in infected TG during the subsequent latent phase. Recent results have shown that HSV infection activates Toll-like receptor signaling. Thus, we hypothesized that chemokines may be broadly expressed at both primary sites and latent sites of HSV infection for prolonged periods of time. Real-time reverse transcriptase-polymrease chain reaction (RT-PCR) to quantify expression levels of transcripts encoding chemokines and their receptors in cornea and TG following corneal infection. RNAs encoding the inflammatory-type chemokine receptors CCR1, CCR2, CCR5, and CXCR3, which are highly expressed on activated T cells, macrophages and most immature dendritic cells (DC), and the more broadly expressed CCR7, were highly expressed and strongly induced in infected cornea and TG at 3 and 10 days postinfection (dpi). Elevated levels of these RNAs persisted in both cornea and TG during the latent phase at 30 dpi. RNAs for the broadly expressed CXCR4 receptor was induced at 30 dpi but less so at 3 and 10 dpi in both cornea and TG. Transcripts for CCR3 and CCR6, receptors that are not highly expressed on activated T cells or macrophages, also appeared to be induced during acute and latent phases; however, their very low expression levels were near the limit of our detection. RNAs encoding the CCR1 and CCR5 chemokine ligands MIP-1α, MIP-1β and RANTES, and the CCR2 ligand MCP-1 were also strongly induced and persisted in cornea and TG during the latent phase. These and other recent results argue that HSV antigens or DNA can stimulate expression of chemokines, perhaps through activation of Toll-like receptors, for long periods of time at both primary and latent sites of HSV infection. These chemokines recruit activated T cells and other immune cells, including DC, that express chemokine receptors to primary and secondary sites of infection. Prolonged activation of chemokine expression could provide mechanistic explanations for certain aspects of HSV biology and pathogenesis.

Herpes simplex virus type 2 virion host shutoff protein regulates alpha/beta interferon but not adaptive immune responses during primary infection in vivo.

The herpes simplex virus (HSV) virion host shutoff (vhs) protein, the product of the UL41 (vhs) gene, is an important determinant of HSV virulence. vhs has been implicated in HSV interference with host antiviral immune responses, down-regulating expression of major histocompatibility complex molecules to help HSV evade host adaptive immunity. The severe attenuation of vhs-deficient viruses in vivo could reflect their inability to escape immune detection. To test this hypothesis, BALB/c or congenic SCID mice were infected intravaginally (i.vag.) with the HSV type 2 (HSV-2) vhs null mutant 333d41 or the vhs rescue virus 333d41(R). vhs-deficient virus remained severely attenuated in SCID mice compared with rescue virus, indicating that vhs regulation of adaptive immune responses does not influence HSV pathogenesis during acute infection. Innate antiviral effectors remain intact in SCID mice; prominent among these is alpha/beta interferon (IFN-alpha/beta). The attenuation of HSV-2 vhs mutants could reflect their failure to suppress IFN-alpha/beta-mediated antiviral activity. To test this hypothesis, 129 and congenic IFN-alpha/beta receptor-deficient (IFN-alpha/betaR(-/-)) mice were infected i.vag. with wild-type virus, vhs null mutants 333-vhsB or 333d41, or the vhs rescue virus 333d41(R). Whereas vhs-deficient viruses showed greatly reduced replication in the genital mucosa of 129 mice compared with wild-type or vhs rescue viruses, they were restored to nearly wild-type levels of replication in IFN-alpha/betaR(-/-) mice over the first 2 days postinfection. Only wild-type and vhs rescue viruses caused severe genital disease and hind limb paralysis in 129 mice, but infection of IFN-alpha/betaR(-/-) mice restored the virulence of vhs-deficient viruses. vhs-deficient viruses replicated as vigorously as wild-type and rescue viruses in the nervous systems of IFN-alpha/betaR(-/-) mice. Restoration was specific for the vhs mutation, because thymidine kinase-deficient HSV-2 did not regain virulence or the capacity to replicate in the nervous systems of IFN-alpha/betaR(-/-) mice. Furthermore, the defect in the IFN-alpha/beta response was required for restoration of vhs-deficient virus replication and virulence, but the IFN-alpha/beta-stimulated protein kinase R pathway was not involved. Finally, vhs of HSV-2 has a unique capacity to interfere with the IFN-alpha/beta response in vivo, because an HSV-1 vhs null mutant did not recover replication and virulence after i.vag. inoculation into IFN-alpha/betaR(-/-) mice. These results indicate that vhs plays an important role early in HSV-2 pathogenesis in vivo by interfering with the IFN-alpha/beta-mediated antiviral response.

Morphine reduces herpes simplex virus-1 pathogenesis in the murine flank

Here we investigate the effect of morphine on herpes simplex virus-1 (HSV-1) pathogenesis using a murine flank scarification model. Murine flank scarification with HSV-1 results in primary lesions at the site of inoculation within three days and lesions at secondary sites within four days. The lesions are scored based on lesion size. Applying 0.1 mM morphine to the skin one-day post inoculation tested the effect of morphine on the formation of the herpes lesion. On days three through five, mice treated with morphine developed lesions with scores half of that observed in untreated animals, however, skin viral titers on these days were equivalent. Further, 1.0 microM morphine did not effect the replication rate of HSV-1 in Vero cells. Taken together, these data suggest the morphine reduced HSV-1 pathogenesis by modifying the host response to HSV-1 infection and not by reducing viral replication rates.

Herpes simplex virus antiviral drug resistance--current trends and future prospects.

The various manifestations of herpes simplex virus (HSV) have been widely treated using antiviral agents for more than 40 years. Acyclovir (ACV) is the drug that has been most commonly used to date. When tested in cell culture, the majority of isolates of HSV are sensitive to ACV with ED50 values of approximately 0.1 microg/ml. ACV-resistant strains (defined as having ED50>2 microg/ml) are rarely encountered in clinical practice among normal patients (<1% isolates) and there is no firm evidence, to date, that this incidence is increasing. Resistant HSV occurs much more frequently, however, among immunocompromised patients during treatment (approximately 5% isolates) where this is recognised to be an important clinical problem leading to ineffective therapy. In this review it is argued that the rapid establishment of neuronal latency in the normal pathogenesis of HSV is the key to the low incidence of resistance development and leads to some optimism concerning future trends.

Type I interferons and herpes simplex virus infection: a naked DNA approach as a therapeutic option?

Herpes simplex virus (HSV) types 1 and 2 are highly successful human pathogens that can elicit blinding herpetic keratoconjunctivitis, fatal sporadic encephalitis, aseptic meningitis, and increase the risk of acquiring additional sexually transmitted diseases. Type I interferons (IFN) play a significant role in controlling HSV pathogenesis by antagonizing viral replication and spread. Taking advantage of the susceptibility of HSV to IFNs, a novel approach of employing plasmid DNA cassettes expressing type 1 IFNs to antagonize viral pathogenesis has been undertaken. This review will describe recent work in our lab and those of others using naked DNA encoding cytokines to antagonize HSV replication and virus trafficking or immune-mediated pathogenesis as a result of viral assault to ocular tissue.

Generation and Use of Recombinant Reporter Viruses for Study of Herpes Simplex Virus Infectionsin Vivo

It has become increasingly clear that the fate of herpes simplex virus (HSV) infections involves complex interactions between the virus and the specific cell types that comprise the tissues of the animal host. No reliable cell culture system for studying the establishment of latency and reactivation exists, and therefore these studies must be performed within animal models. One difficulty in elucidating the molecular regulation of these events is in determining the transcriptional activity of key viral genes during different stages of the infectionin vivo.The heterogeneous cell types comprising infected tissues make PCR analysis of tissue homogenates difficult to interpret. The need to characterize expression of multiple transcriptional markers reliably and quantitatively at the level of individual cells is therefore key to determining the interplay between viral and cellular genes during latency and reactivation. Here we discuss the construction and evaluation of HSV reporter viruses that have been used in these analyses. HSV-1 recombinants have been engineered with representative viral promoters driving β-galactosidase as a reporter. Methodology used to evaluate the levels of gene expression using (1) quantitative enzyme assays, (2) precipitatable substrate assays to localize the positive cells, and (3) immunohistochemistry and fluorescence assays to look at colocalization of markers duringin vivoinfection is presented. In addition to studying the molecular pathogenesis of HSV, the application of similar reporter viruses to evaluate promoters for targeting various differentiated tissues will be useful in developing these viruses as potential vectors for gene therapy.

Viral and cellular requirements for entry of herpes simplex virus type 1 into primary neuronal cells.

Herpes simplex virus (HSV) causes many disease states including mucosal lesions, encephalitis or disseminated infection in the immunocompromised host. These diverse clinical manifestations reflect the capacity of the virus to infect both epithelial and neuronal cell types. Determining the requirements for virus entry into both cell types may provide insights into the pathogenesis of HSV. Previous studies have focused on identifying viral and cellular requirements for entry using epithelial cells. However, little is known about the requirements for binding and entry into neuronal cells. The purpose of the studies reported here was to identify viral and cellular components involved in entry of HSV-1 into primary neuronal cells. Heparan sulfate glycosaminoglycans were found to serve as a receptor for entry of HSV-1 into primary neuronal cells. Evidence to support this includes the findings that heparin (an analogue of heparan sulfate) competitively inhibited virus binding and expression of immediate early virus gene products. In addition, heparitinase removed viral receptors and inhibited virus entry. In epithelial cells, deletion of HSV-1 glycoprotein C (gC) results in virions that have reduced specific binding activity (virus particles bound per cell) and specific infectivity. However, in neuronal cells, it was found that deletion of gC resulted in no loss in specific binding activity, but did result in significant impairment of virus entry as measured by expression of immediate early viral gene product. Taken together, these findings suggest cell-type differences in virus binding and entry and a different role for gC in neuronal cell infection.

Neuroinvasive properties of herpes simplex virus type 1 glycoprotein variants are controlled by the immune response.

Neuroinvasiveness is a property central to the pathogenesis of herpes simplex virus (HSV) and most isolates demonstrate this property. Exceptions are HSV strains KOS and ANG, for which we have previously shown that the non-neuroinvasive phenotype is referable to single amino acid changes in glycoprotein D for ANG or glycoprotein B for KOS. Because glycoproteins B and D are immunologically significant, the possibility that the phenotype has an immunologic basis was examined. Nonimmunosuppressed mice could not be killed with any dose of these non-neuroinvasive viruses after footpad inoculation, but in cyclophosphamide-suppressed animals, the ratios of plaque-forming units to LD50 decreased by at least four orders of magnitude to levels comparable with that of ANG-path, a neuroinvasive derivative of ANG. KOS and ANG induced a more rapid circulating neutralizing Ab response than did ANG-path, and mice were protected when these agents were co-infected with the neuroinvasive strain. The noninvasive viruses engendered an enhanced mononuclear cell infiltrate in infected spinal ganglia which consisted of increased numbers of CD4+ and CD8+ T cells and an increased production and secretion of IgG. HSV-specific Ab-secreting cells were also observed. In addition, passive transfer of anti-HSV mouse serum protected immunosuppressed mice from lethal HSV challenge. Selective in vivo depletion of T lymphocytes increased the detectable levels of both KOS and ANG viruses in the spinal ganglia at 6 days postinfection, but it did not alter the ratios of plaque-forming units to LD50 or affect the HSV-induced increase in ganglionic IgG. Taken together, these data indicate that in these systems there is an immunologic basis for the control of HSV-1 neuroinvasiveness and that humoral, rather than cell-mediated immunity, is playing the major role.

Herpes simplex virus pathogenesis in transgenic mice is altered by the homeodomain protein Hox 1.3.

The DNA sequence TAAT is the core binding motif for the mouse homeodomain protein Hox 1.3 (proposed new name, Hoxa-5). These sequences are present within the multiple TAATGARAT regulatory motifs in the promoters of the immediate-early genes which control herpes simplex virus type 1 replication. To investigate the role of this homeodomain protein in the regulation of herpes simplex virus gene expression and pathogenesis, transgenic mice containing a mouse Hox 1.3 cDNA under the control of the virus- and interferon-inducible Mx 1 promoter were generated. After infection of transgenic mice with herpes simplex virus, Hox 1.3 RNA and protein were expressed at the sites of virus replication. In these transgenic mice, herpes simplex virus replication, spread of virus through the host, and virus-induced mortality were markedly enhanced. Increased spread and replication of herpes simplex virus were also observed in cultured fibroblasts from transgenic mice. This finding suggests that in vivo, Hox 1.3 may increase viral spread by increasing viral replication at the level of the individual infected cells. These results demonstrate that expression of a transgene encoding a single host protein, Hox 1.3, alters the pathogenesis of experimental herpes simplex virus infection. We conclude that a protein that belongs to a class of DNA-binding proteins which are best known for their role in regulating embryonic development may also regulate herpesvirus pathogenesis.