Apoptosis induction after herpes simplex virus infection differs according to cell type in vivo

The chicken chorioallantoic membrane model for isolation of CRISPR/cas9-based HSV-1 mutant expressing tumor suppressor p53

Oncolytic viruses (OVs) have emerged as a novel cancer treatment modality, which selectively target and kill cancer cells while sparing normal ones. Among them, engineered Herpes simplex virus type 1 (HSV-1) has been proposed as a potential treatment for cancer and was moved to phase III clinical trials. Previous studies showed that design of OV therapy combined with p53 gene therapy increases the anti-cancer activities of OVs. Here, the UL39 gene of the ICP34.5 deleted HSV-1 was manipulated with the insertion of the EGFP-p53 expression cassette utilizing CRISPR/ Cas9 editing approach to enhance oncoselectivity and oncotoxicity capabilities. The ΔUL39/Δγ34.5/HSV1-p53 mutant was isolated using the chorioallantoic membrane (CAM) of fertilized chicken eggs as a complementing membrane to support the growth of the viruses with gene deficiencies. Comparing phenotypic features of ΔUL39/Δγ34.5/HSV1-p53-infected cells with the parent Δγ34.5/HSV-1 in vitro revealed that HSV-1-P53 had cytolytic ability in various cell lines from different origin with different p53 expression rates. Altogether, data presented here illustrate the feasibility of exploiting CAM model as a promising strategy for isolating recombinant viruses such as CRISPR/Cas9 mediated HSV-1-P53 mutant with less virus replication in cell lines due to increased cell mortality induced by exogenous p53.

Caspase-8 is required for HSV-1-induced apoptosis and promotes effective viral particle release via autophagy inhibition

Regulated cell death (RCD) plays an important role in the progression of viral replication and particle release in cells infected by herpes simplex virus-1 (HSV-1). However, the kind of RCD (apoptosis, necroptosis, others) and the resulting cytopathic effect of HSV-1 depends on the cell type and the species. In this study, we further investigated the molecular mechanisms of apoptosis induced by HSV-1. Although a role of caspase-8 has previously been suggested, we now clearly show that caspase-8 is required for HSV-1-induced apoptosis in a FADD-/death receptor-independent manner in both mouse embryo fibroblasts (MEF) and human monocytes (U937). While wild-type (wt) MEFs and U937 cells exhibited increased caspase-8 and caspase-3 activation and apoptosis after HSV-1 infection, respective caspase-8-deficient (caspase-8-/-) cells were largely impeded in any of these effects. Unexpectedly, caspase-8-/- MEF and U937 cells also showed less virus particle release associated with increased autophagy as evidenced by higher Beclin-1 and lower p62/SQSTM1 levels and increased LC3-I to LC3-II conversion. Confocal and electron microscopy revealed that HSV-1 stimulated a strong perinuclear multivesicular body response, resembling increased autophagy in caspase-8-/- cells, entrapping virions in cellular endosomes. Pharmacological inhibition of autophagy by wortmannin restored the ability of caspase-8-/- cells to release viral particles in similar amounts as in wt cells. Altogether our results support a non-canonical role of caspase-8 in both HSV-1-induced apoptosis and viral particle release through autophagic regulation.

Approaches to Evaluating Necroptosis in Virus-Infected Cells

The immune system functions to protect the host from pathogens. To counter host defense mechanisms, pathogens have developed unique strategies to evade detection or restrict host immune responses. Programmed cell death is a major contributor to the multiple host responses that help to eliminate infected cells for obligate intracellular pathogens like viruses. Initiation of programmed cell death pathways during the early stages of viral infections is critical for organismal survival as it restricts the virus from replicating and serves to drive antiviral inflammation immune recruitment through the release of damage-associated molecular patterns (DAMPs) from the dying cell. Necroptosis has been implicated as a critical programmed cell death pathway in a diverse set of diseases and pathological conditions including acute viral infections. This cell death pathway occurs when certain host sensors are triggered leading to the downstream induction of mixed-lineage kinase domain-like protein (MLKL). MLKL induction leads to cytoplasmic membrane disruption and subsequent cellular destruction with the release of DAMPs. As the role of this cell death pathway in human disease becomes apparent, methods identifying necroptosis patterns and outcomes will need to be further developed. Here, we discuss advances in our understanding of how viruses counteract necroptosis, methods to quantify the pathway, its effects on viral pathogenesis, and its impact on cellular signaling.

Fas/FasL Contributes to HSV-1 Brain Infection and Neuroinflammation

The Fas/FasL pathway plays a key role in immune homeostasis and immune surveillance. In the central nervous system (CNS) Fas/FasL is involved in axonal outgrowth and adult neurogenesis. However, little is known about the role of the Fas/FasL pathway in herpes encephalitis. In this study, we used a neuropathogenic clinical strain of herpes simplex virus type 1 (HSV-1) to explore infection-induced inflammation and immune responses in the mouse brain and the role of Fas/FasL in antiviral CNS immunity. HSV-1 CNS infection induced the infiltration of Fas- FasL-bearing monocytes and T cells in the brain and also to an up-regulation of Fas and FasL expression on resident astrocytes and microglia within infected sites. Upon infection, Fas- and FasL-deficient mice (lpr and gld) were partially protected from encephalitis with a decreased morbidity and mortality compared to WT mice. Fas/FasL deficiency promoted cell-mediated immunity within the CNS. Fas receptor stimulation abrogated HSV-1 induced activation and inflammatory reactions in microglia from WT mice, while lack of Fas or FasL led to a more pronounced activation of monocytes and microglia and also to an enhanced differentiation of these cells into a pro-inflammatory M1 phenotype. Furthermore, the specific immune system was more efficient in Fas- and FasL-deficient mice with significantly higher numbers of infiltrating HSV-1-specific cytotoxic T cells in the brain. Our data indicate that the Fas/FasL pathway leads to excessive neuroinflammation during HSV-1 infection, which is associated with a diminished anti-viral response and an excessive neuroinflammation.

Herpes Simplex Virus Type 1 Neuronal Infection Triggers the Disassembly of Key Structural Components of Dendritic Spines

Herpes simplex virus type 1 (HSV-1) is a widespread neurotropic virus. Primary infection of HSV-1 in facial epithelium leads to retrograde axonal transport to the central nervous system (CNS) where it establishes latency. Under stressful conditions, the virus reactivates, and new progeny are transported anterogradely to the primary site of infection. During the late stages of neuronal infection, axonal damage can occur, however, the impact of HSV-1 infection on the morphology and functional integrity of neuronal dendrites during the early stages of infection is unknown. We previously demonstrated that acute HSV-1 infection in neuronal cell lines selectively enhances Arc protein expression - a major regulator of long-term synaptic plasticity and memory consolidation, known for being a protein-interaction hub in the postsynaptic dendritic compartment. Thus, HSV-1 induced Arc expression may alter the functionality of infected neurons and negatively impact dendritic spine dynamics. In this study we demonstrated that HSV-1 infection induces structural disassembly and functional deregulation in cultured cortical neurons, an altered glutamate response, Arc accumulation within the somata, and decreased expression of spine scaffolding-like proteins such as PSD-95, Drebrin and CaMKIIβ. However, whether these alterations are specific to the HSV-1 infection mechanism or reflect a secondary neurodegenerative process remains to be determined.

Oncolytic activity of naturally attenuated herpes-simplex virus HF10 against an immunocompetent model of oral carcinoma

Prognosis for advanced oral carcinoma remains poor. Oncolytic virotherapy uses replication-competent viruses to infect and kill only the tumor cells. However, it has been difficult to investigate the oncolytic activity of viruses against oral carcinomas in mouse models. This study established a mouse model of oral cancer and investigated the in vitro and in vivo anti-tumor effects of HF10, a highly attenuated, replication-competent herpes simplex virus (HSV)-1. Mouse tongue cancer was induced by injecting 4-nitroquinoline 1-oxide into the mouse tongue. The murine oral cancer cell line isolated from this tumor, named NMOC1, formed invasive carcinoma within a week when injected into mouse tongue. HF10 successfully infected, replicated, and spread in the cancer cells in vitro. HF10 was able to kill cancer cells isolated from human or mouse tongue tumor. HF10 injection into tongue carcinomas prolonged mouse survival without any side effects or weight loss. Intertumoral injection of GFP-expressing HF10 confirmed that viral spread was confined within the tumors. Immunohistochemical staining showed that HF10 induced infiltration of CD8-positive T cells around HSV-infected cells in the tumor mass, implying increased anti-tumor immunity. We successfully established an oral cancer cell line and showed that HF10 is a promising therapeutic agent for oral cancer.

Oncolytic activity of HF10 in head and neck squamous cell carcinomas

Recent developments in therapeutic strategies have improved the prognosis of head and neck squamous cell carcinoma (HNSCC). Nevertheless, 5-year survival rate remains only 40%, necessitating new therapeutic agents. Oncolytic virotherapy entails use of replication-competent viruses to selectively kill cancer cells. We aimed to explore the potential of HF10 as an oncolytic virus against human or mouse HNSCC cell lines, and primary-cultured HNSCC cells. HF10 replicated well in all the HNSCC cells, in which it induced cytopathic effects and cell killing. Next, we investigated the oncolytic effects of HF10 in ear tumor models with human or mouse tumor cells. We detected HF10-infected cells within the ear tumors based on their expression of green fluorescent protein. HF10 injection suppressed ear tumor growth and prolonged overall survival. In the syngeneic model, HF10 infection induced tumor necrosis with infiltration of CD8-positive cells. Moreover, the splenocytes of HF10-treated mice released antitumor cytokines, IL-2, IL-12, IFN-alpha, IFN-beta, IFN-gamma, and TNF-alpha, after stimulation with tumor cells in vitro. The HF10-treated mice that survived their original tumor burdens rejected tumor cells upon re-challenge. These results suggested that HF10 killed HNSCC cells and induced antitumoral immunity, thereby establishing it as a promising agent for the treatment of HNSCC patients.

Epstein-Barr virus particles induce centrosome amplification and chromosomal instability

Infections with Epstein–Barr virus (EBV) are associated with cancer development, and EBV lytic replication (the process that generates virus progeny) is a strong risk factor for some cancer types. Here we report that EBV infection of B-lymphocytes (in vitro and in a mouse model) leads to an increased rate of centrosome amplification, associated with chromosomal instability. This effect can be reproduced with virus-like particles devoid of EBV DNA, but not with defective virus-like particles that cannot infect host cells. Viral protein BNRF1 induces centrosome amplification, and BNRF1-deficient viruses largely lose this property. These findings identify a new mechanism by which EBV particles can induce chromosomal instability without establishing a chronic infection, thereby conferring a risk for development of tumours that do not necessarily carry the viral genome.

Infection with Epstein–Barr virus (EBV) is associated with increased risk of cancer development. Here the authors show that EBV particles, and more specifically the viral protein BNRF1, induce centrosome amplification and chromosomal instability in host cells in the absence of chronic infection.

Herpes simplex encephalitis is linked with selective mitochondrial damage; a post-mortem and in vitro study

Herpes simplex virus type-1 (HSV-1) encephalitis (HSE) is the most commonly diagnosed cause of viral encephalitis in western countries. Despite antiviral treatment, HSE remains a devastating disease with high morbidity and mortality. Improved understanding of pathogenesis may lead to more effective therapies. Mitochondrial damage has been reported during HSV infection in vitro. However, whether it occurs in the human brain and whether this contributes to the pathogenesis has not been fully explored. Minocycline, an antibiotic, has been reported to protect mitochondria and limit brain damage. Minocycline has not been studied in HSV infection. In the first genome-wide transcriptomic study of post-mortem human HSE brain tissue, we demonstrated a highly preferential reduction in mitochondrial genome (MtDNA) encoded transcripts in HSE cases (n = 3) compared to controls (n = 5). Brain tissue exhibited a significant inverse correlation for immunostaining between cytochrome c oxidase subunit 1 (CO1), a MtDNA encoded enzyme subunit, and HSV-1; with lower abundance for mitochondrial protein in regions where HSV-1 was abundant. Preferential loss of mitochondrial function, among MtDNA encoded components, was confirmed using an in vitro primary human astrocyte HSV-1 infection model. Dysfunction of cytochrome c oxidase (CO), a mitochondrial enzyme composed predominantly of MtDNA encoded subunits, preceded that of succinate dehydrogenase (composed entirely of nuclear encoded subunits). Minocycline treated astrocytes exhibited higher CO1 transcript abundance, sustained CO activity and cell viability compared to non-treated astrocytes. Based on observations from HSE patient tissue, this study highlights mitochondrial damage as a critical and early event during HSV-1 infection. We demonstrate minocycline preserves mitochondrial function and cell viability during HSV-1 infection. Minocycline, and mitochondrial protection, offers a novel adjunctive therapeutic approach for limiting brain cell damage and potentially improving outcome among HSE patients.

Innate defense mechanisms against HSV-1 infection in the target tissues, skin and brain

Herpes simplex virus type 1 (HSV-1) initiates productive infection in mucocutaneous tissues to cause cold sores and establishes latent infection in the trigeminal ganglia. Under certain circumstances, HSV-1 may cause encephalitis. Here, we compared host innate defenses against HSV-1 in the two clinically relevant tissues, skin and brain, using a unique ex vivo system of organ culture. Upon HSV-1 infection and spread, apoptosis induction was observed in the skin, but not in brain tissues. While the two tissues elicited interferon (IFN-β) response upon HSV1 infection, IFN induction was more robust in the skin compared to the brain. Moreover, antiviral response to exogenous IFNβ treatment was much stronger in the skin compared to brain tissues. This observation was not related to the availability of the IFN receptor on cells' surface. Taken together, our study demonstrates differential innate antiviral responses to HSV-1 infection that may be exploited in future development of selective and tissue-specific anti-viral treatments.

Latent herpes simplex virus 1 infection does not induce apoptosis in human trigeminal Ganglia

Herpes simplex virus 1 (HSV-1) can establish lifelong latency in human trigeminal ganglia. Latently infected ganglia contain CD8(+) T cells, which secrete granzyme B and are thus capable of inducing neuronal apoptosis. Using immunohistochemistry and single-cell reverse transcription-quantitative PCR (RT-qPCR), higher frequency and transcript levels of caspase-3 were found in HSV-1-negative compared to HSV-1-positive ganglia and neurons, respectively. No terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assay-positive neurons were detected. The infiltrating T cells do not induce apoptosis in latently infected neurons.

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.

Different modes of herpes simplex virus type 1 spread in brain and skin tissues

Herpes simplex virus type 1 (HSV-1) initially infects the skin and subsequently spreads to the nervous system. To investigate and compare HSV-1 mode of propagation in the two clinically relevant tissues, we have established ex vivo infection models, using native tissues of mouse and human skin, as well as mouse brain, maintained in organ cultures. HSV-1, which is naturally restricted to the human, infects and spreads in the mouse and human skin tissues in a similar fashion, thus validating the mouse model. The spread of HSV-1 in the skin was concentric to form typical plaques of limited size, predominantly of cytopathic cells. By contrast, HSV-1 spread in the brain tissue was directed along specific neuronal networks with no apparent cytopathic effect. Two additional differences were noted following infection of the skin and brain tissues. First, only a negligible amount of extracellular progeny virus was produced of the infected brain tissues, while substantial quantity of infectious progeny virus was released to the media of the infected skin. Second, antibodies against HSV-1, added following the infection, effectively restricted viral spread in the skin but have no effect on viral spread in the brain tissue. Taken together, these results reveal that HSV-1 spread within the brain tissue mostly by direct transfer from cell to cell, while in the skin the progeny extracellular virus predominates, thus facilitating the infection to new individuals.

Oncolytic viral therapy with a combination of HF10, a herpes simplex virus type 1 variant and granulocyte-macrophage colony-stimulating factor for murine ovarian cancer

Ovarian cancer is the most frequent cause of gynecological cancer-related mortality as a majority of patients are diagnosed at an advanced stage with intraperitoneal dissemination because of the absence of initial symptoms. Granulocyte-macrophage colony-stimulating factor (GM-CSF) plays an important role in the maturation of specialized antigen-presenting cells. In this study, we utilized a herpes simplex virus (HSV) amplicon expressing murine GM-CSF combined with HF10 (mGM-CSF amplicon), a highly attenuated HSV type 1 strain functioning as a helper virus to strengthen anti-tumor immune response, for the treatment of ovarian cancer with intraperitoneal dissemination. A mouse ovarian cancer cell line, OV2944-HM-1 (HM-1), was intraperitoneally injected, following which HF10 only or the mGM-CSF amplicon was injected intraperitoneally three times. HF10 injection prolonged survival and decreased intraperitoneal dissemination, but to a lesser extent than the mGM-CSF amplicon. Although HF10 replication was not observed in HM-1 cells, expression of VP5, a late gene coding the major capsid protein of HSV, was detected. Moreover, mGM-CSF production was detected in transfected HM-1 cells. Immunohistochemical staining revealed the infiltration of CD4- and CD8-positive cells into the peritoneal tumor(s). A significantly increased CD4+ T cell concentration was observed in the spleen. Murine splenic cells after each treatment were stimulated with HM-1 cells, and the strongest immune response was observed in the mice that received mGM-CSF amplicon injections. These results suggested that the mGM-CSF amplicon is a promising agent for the treatment of advanced ovarian cancer with intraperitoneal dissemination.

Inhibition of Bim enhances replication of varicella-zoster virus and delays plaque formation in virus-infected cells

Programmed cell death (apoptosis) is an important host defense mechanism against intracellular pathogens, such as viruses. Accordingly, viruses have evolved multiple mechanisms to modulate apoptosis to enhance replication. Varicella-zoster virus (VZV) induces apoptosis in human fibroblasts and melanoma cells. We found that VZV triggered the phosphorylation of the proapoptotic proteins Bim and BAD but had little or no effect on other Bcl-2 family members. Since phosphorylation of Bim and BAD reduces their proapoptotic activity, this may prevent or delay apoptosis in VZV-infected cells. Phosphorylation of Bim but not BAD in VZV-infected cells was dependent on activation of the MEK/extracellular signal-regulated kinase (ERK) pathway. Cells knocked down for Bim showed delayed VZV plaque formation, resulting in longer survival of VZV-infected cells and increased replication of virus, compared with wild-type cells infected with virus. Conversely, overexpression of Bim resulted in earlier plaque formation, smaller plaques, reduced virus replication, and increased caspase 3 activity. Inhibition of caspase activity in VZV-infected cells overexpressing Bim restored levels of virus production similar to those seen with virus-infected wild-type cells. Previously we showed that VZV ORF12 activates ERK and inhibits apoptosis in virus-infected cells. Here we found that VZV ORF12 contributes to Bim and BAD phosphorylation. In summary, VZV triggers Bim phosphorylation; reduction of Bim levels results in longer survival of VZV-infected cells and increased VZV replication.

Immunological control of herpes simplex virus infections

Herpes simplex virus type 1 (HSV-1) is capable of causing a latent infection in sensory neurons that lasts for the lifetime of the host. The primary infection is resolved following the induction of the innate immune response that controls replication of the virus until the adaptive immune response can clear the active infection. HSV-1-specific CD8⁺ T cells survey the ganglionic regions containing latently infected neurons and participate in preventing reactivation of HSV from latency. The long-term residence and migration dynamics of the T cells in the trigeminal ganglia appear to distinguish them from the traditional memory T cell subsets. Recently described tissue resident memory (T_RM) T cells establish residence and survive for long periods in peripheral tissue compartments following antigen exposure. This review focuses on the immune system response to HSV-1 infection. Particular emphasis is placed on the evidence pointing to the HSV-1-specific CD8⁺ T cells in the trigeminal belonging to the T_RM class of memory T cells and the role of T_RM cells in virus infection, pathogenesis, latency, and disease.

A neuron-specific role for autophagy in antiviral defense against herpes simplex virus

Type I interferons (IFNs) are considered to be the universal mechanism by which viral infections are controlled. However, many IFN-stimulated genes (ISGs) rely on antiviral pathways that are toxic to host cells, which may be detrimental in nonrenewable cell types, such as neurons. We show that dorsal root ganglionic (DRG) neurons produced little type I IFNs in response to infection with a neurotropic virus, herpes simplex type 1 (HSV-1). Further, type I IFN treatment failed to completely block HSV-1 replication or to induce IFN-primed cell death in neurons. We found that DRG neurons required autophagy to limit HSV-1 replication both in vivo and in vitro. In contrast, mucosal epithelial cells and other mitotic cells responded robustly to type I IFNs and did not require autophagy to control viral replication. These findings reveal a fundamental difference in the innate antiviral strategies employed by neurons and mitotic cells to control HSV-1 infection.

Enhanced antitumoral activity of oncolytic herpes simplex virus with gemcitabine using colorectal tumor models

To enhance the oncolytic activity of herpes simplex viruses (HSVs) control of immune-suppression and immune-resistance by cancer cells is important. Myeloid-derived suppressor cells (MDSCs), which interfere with tumor-suppressive environments, are inhibited by gemcitabine (GEM) treatment. We investigated the oncolytic activity and systemic antitumor immunity induced by oncolytic HSVs in combination with GEM treatment. A mouse model with subcutaneous tumors on both sides of the lateral flanks was used. A highly attenuated HSV type 1, strain HF10, was inoculated into one side of each tumor three times following intraperitoneal injection of GEM. Histopathological changes and IFN-γ secretion of the tumor and leukocytes in the spleen were analyzed. These treatments were repeated to enhance oncolytic activity. HF10 inoculation reduced tumor growth only on the HF10-treated side. HF10 inoculation following GEM treatment resulted in greater reduction of tumor growth on the HF10-treated tumor; furthermore, reduction of tumors on the contralateral untreated side was also observed. Necrosis of the tumor was observed in areas where HSV-infected cells were detected. F4/80(+) macrophages around the tumor were eliminated, and CD4(+) T and CD8(+) T cells increased in the spleen. A single injection of GEM decreased CD11b(+) /Gr-1(+) MDSCs while retaining CD4(+) T cells and CD8(+) T cells. Repetition of this treatment regimen resulted in even greater reduction of tumor growth on both sides and complete rejection in some of the mice. Intratumoral injection of oncolytic HSVs following GEM injection reduced MDSCs. Repeated treatment with oncolytic HSVs following GEM resulted in enhanced oncolytic activity.

Translationally controlled tumour protein (TCTP) is present in human cornea and increases in herpetic keratitis

BACKGROUND

Translationally controlled tumour protein is a multifunctional calcium binding protein which has an important role in apoptosis, calcium levels balance and immunological response. The aim of this study was to evaluated the presence and distribution of TCTP in healthy human corneas and to identify and characterize the presence and distribution of this protein in human normal cornea. Since recent studies suggest that apoptosis, calcium levels and immunological mechanisms play a role in the pathogenesis of herpetic stromal keratitis, we studied TCTP expression in this disease.

METHODS

We evaluated the expression of TCTP at both RNA messanger and protein level by using reverse transcriptase analysis, immunoblotting and immunohistochemistry in 10 healthy samples cornea: four obtained after penetrating keratoplasty and six from eyes enucleated for other pathologies. Finally, we analysed by immunohistochemistry ten paraffin-embedded samples of Herpes simplex virus keratitis collected at Siena Department of Human Pathology and Oncology: 5 had clinically quiescent disease and 5 had active corneal inflammation.

RESULTS

Reverse transcriptase and immunoblotting demonstrated TCTP expression in cornea as a 22,000 Da molecular weight band corresponding to the molecular weight of this protein. Immunohistochemically, all the layers of normal corneal epithelium showed TCTP cytoplasmic expression. TCTP was, also, observed in keratocytes and in the endothelium. In Herpes simplex virus keratitis samples, strong expression of TCTP was evident in stromal cells, in the inflammatory infiltrate and in neo-vessels.

CONCLUSIONS

In this preliminary study we demonstrated, for the first time, the presence of TCTP in human cornea, suggesting a potential role in the pathogenesis of herpes virus keratitis.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/3306813447428149.

Control of HSV-1 latency in human trigeminal ganglia--current overview

Although recurrent Herpes simplex virus type 1 (HSV-1) infections are quite common in humans, little is known about the exact molecular mechanisms involved in latency and reactivation of the virus from its stronghold, the trigeminal ganglion. After primary infection, HSV-1 establishes latency in sensory neurons, a state that lasts for the life of the host. Reactivation of the virus leads to recurrent disease, ranging from relatively harmless cold sores to ocular herpes. If herpes encephalitis-often a devastating disease-is also caused by reactivation or a new infection, is still a matter of debate. It is widely accepted that CD8(+) T cells as well as host cellular factors play a crucial role in maintaining latency. At least in the animal model, IFNγ and Granzyme B secretion of T cells were shown to be important for control of viral latency. Furthermore, the virus itself expresses factors that regulate its own latency-reactivation cycle. In this regard, the latency associated transcript, immediate-early proteins, and viral miRNAs seem to be the key players that control latency and reactivation on the viral side. This review focuses on HSV-1 latency in humans in the light of mechanisms learned from animal models.

Herpes simplex virus type 1 penetrates the basement membrane in human nasal respiratory mucosa

Background

Herpes simplex virus infections are highly prevalent in humans. However, the current therapeutics suffer important drawbacks such as limited results in neonates, increasing occurrence of resistance and impeded treatment of stromal infections. Remarkably, interactions of herpesviruses with human mucosa, the locus of infection, remain poorly understood and the underlying mechanisms in stromal infection remain controversial.

Methodology/Principal Findings

A human model consisting of nasal respiratory mucosa explants was characterised. Viability and integrity were examined during 96 h of cultivation. HSV1-mucosa interactions were analysed. In particular, we investigated whether HSV1 is able to reach the stroma.

Explant viability and integrity remained preserved. HSV1 induced rounding up and loosening of epithelial cells with very few apoptotic and necrotic cells observed. Following 16–24 h of infection, HSV1 penetrated the basement membrane and replicated in the underlying lamina propria.

Conclusions/Significance

This human explant model can be used to study virus-mucosa interactions and viral mucosal invasion mechanisms. Using this model, our results provide a novel insight into the HSV1 stromal invasion mechanism and for the first time directly demonstrate that HSV1 can penetrate the basement membrane.

Auditory and vestibular defects induced by experimental labyrinthitis following herpes simplex virus in mice

CONCLUSION

Our herpes simplex virus (HSV) labyrinthitis mouse model suggests that HSV infection induces vestibular neuritis and sudden deafness.

OBJECTIVE

Viral labyrinthitis has been postulated to play a role in vestibular neuritis and sudden deafness. We established a mouse model to investigate the pathogenesis of HSV-induced labyrinthitis. The relationship between HSV infection and apoptosis in the labyrinth was assessed.

METHODS

HSV types 1 and 2 were inoculated into the middle ear of mice, and the function of the cochlear and vestibular nerves was assessed. Histopathological changes were examined with hematoxylin and eosin staining. Anti-HSV immunohistochemistry staining and TUNEL staining were done to investigate the relationship between HSV-infected cells and apoptotic cells.

RESULTS

Hearing loss and vestibular dysfunction were observed in all mice after inoculation of HSV type 1 or 2. In the cochlear duct, columnar epithelial cells in the stria vascularis were infected with HSV, but only a portion of the infected cells underwent apoptosis. In contrast, many uninfected cells in the spiral organ of Corti were apoptotic. Vestibular dysfunction was observed when vestibular ganglion cells were largely infected, but not apoptotic. These findings recapitulate sudden deafness and vestibular neuritis described in patients.

IL-29/IL-28A suppress HSV-1 infection of human NT2-N neurons

The newly identified cytokines, IL-28/IL-29 (also termed type III IFNs), are able to inhibit a number of viruses. Here, we examined the antiviral effects of IL-29/IL-28A against herpes simplex virus type 1 (HSV-1) in human NT2-N neurons and CHP212 neuronal cells. Both IL-29 and IL-28A could efficiently inhibit HSV-1 replication in neuronal cells, as evidenced by the reduced expression of HSV-1 DNA and proteins. This inhibitory effect of IL-29 and IL-28A against HSV-1 could be partially blocked by antibody to IL-10Rβ, one of the key receptors for IL-29 and IL-28A. To explore the underlying antiviral mechanisms employed by IL-29/IL-28A, we showed that IL-29/IL-28A could selectively induce the expression of several Toll-like receptors (TLRs) as well as activate TLR-mediated antiviral pathway, including IFN regulatory factor 7, IFN-α, and the key IFN-α stimulated antiviral genes.

A novel oncolytic herpes simplex virus that synergizes with phosphoinositide 3-kinase/Akt pathway inhibitors to target glioblastoma stem cells

PURPOSE

To develop a new oncolytic herpes simplex virus (oHSV) for glioblastoma (GBM) therapy that will be effective in glioblastoma stem cells (GSC), an important and untargeted component of GBM. One approach to enhance oHSV efficacy is by combination with other therapeutic modalities.

EXPERIMENTAL DESIGN

MG18L, containing a U(S)3 deletion and an inactivating LacZ insertion in U(L)39, was constructed for the treatment of brain tumors. Safety was evaluated after intracerebral injection in HSV-susceptible mice. The efficacy of MG18L in human GSCs and glioma cell lines in vitro was compared with other oHSVs, alone or in combination with phosphoinositide-3-kinase (PI3K)/Akt inhibitors (LY294002, triciribine, GDC-0941, and BEZ235). Cytotoxic interactions between MG18L and PI3K/Akt inhibitors were determined using Chou-Talalay analysis. In vivo efficacy studies were conducted using a clinically relevant mouse model of GSC-derived GBM.

RESULTS

MG18L was severely neuroattenuated in mice, replicated well in GSCs, and had anti-GBM activity in vivo. PI3K/Akt inhibitors displayed significant but variable antiproliferative activities in GSCs, whereas their combination with MG18L synergized in killing GSCs and glioma cell lines, but not human astrocytes, through enhanced induction of apoptosis. Importantly, synergy was independent of inhibitor sensitivity. In vivo, the combination of MG18L and LY294002 significantly prolonged survival of mice, as compared with either agent alone, achieving 50% long-term survival in GBM-bearing mice.

CONCLUSIONS

This study establishes a novel therapeutic strategy: oHSV manipulation of critical oncogenic pathways to sensitize cancer cells to molecularly targeted drugs. MG18L is a promising agent for the treatment of GBM, being especially effective when combined with PI3K/Akt pathway-targeted agents.

Hepatocyte growth factor incorporated into herpes simplex virus vector accelerates facial nerve regeneration after crush injury

Hepatocyte growth factor (HGF) promotes regeneration of the central nervous system, but its effects on the peripheral nervous system remain unclear. This study was conducted to elucidate the effect of HGF on regeneration of the murine facial nerve after crush injury. To do so, a replication-defective herpes simplex virus vector that incorporated HGF was prepared (HSV-HGF). The main trunk of the facial nerve was compressed by mosquito hemostats, and HSV-HGF, control vector or medium was then applied to the compressed nerve. We found that mice in the HGF group required significantly fewer days for complete recovery from nerve compression. Furthermore, the amplitude of the evoked buccinator muscle compound action potential increased following HSV-HGF application. HGF expression in and around the compressed nerve was demonstrated by enzyme-linked immunoassay and immunohistochemistry. In addition, HSV-HGF introduction around the damaged nerve significantly accelerated recovery of function of the facial nerve. These data suggest a possible role of HGF in promoting facial nerve regeneration after nerve damage. Furthermore, this viral delivery method may be applied clinically for many types of severe facial palsy during facial nerve decompression surgery.

Regulation of shrimp PjCaspase promoter activity by WSSV VP38 and VP41B

Members of the Caspase family play essential roles in apoptosis. In kuruma shrimp Marsupenaeus japonicus the caspase gene (PjCaspase) was previously found dramatically up-regulated in viral-challenged and -resistant shrimp, suggesting that PjCaspase plays an important role in protecting host from viral infection. In order to further delineate the transcriptional regulation of PjCaspase in response to viral infection, the promoter activity was confirmed by fusing the 5'-flanking promoter region of the PjCaspase gene to the enhanced green fluorescence protein (EGFP) gene and transformed to Trichoplusia ni High Five™ cell line. With streptavidin-bead pulldown assay, two envelope proteins VP38 and VP41B of white spot syndrome virus (WSSV) were found to bind to PjCaspase promoter in vitro. Luciferase reporter assay by cotransfection of PjCaspace promoter with VP38 or VP41B revealed that the proteins act as repressor and activator of PjCaspase transcription respectively. Our study suggested a potential role for the two WSSV proteins on shrimp PjCaspase regulation in response to WSSV challenge. To our knowledge this is the first report on WSSV envelope proteins found to be involved in gene regulation. These results provide insights into the molecular regulation of PjCaspase gene expression, which will be helpful for shrimp viral disease control.