Equine herpesvirus type 1-mediated oncolysis of human glioblastoma multiforme cells

Equid Alphaherpesvirus 1 Modulates Actin Cytoskeleton and Inhibits Migration of Glioblastoma Multiforme Cell Line A172

Equid alphaherpesvirus 1 (EHV-1) causes respiratory diseases, abortion, and neurological disorders in horses. Recently, the oncolytic potential of this virus and its possible use in anticancer therapy has been reported, but its influence on cytoskeleton was not evaluated yet. In the following study, we have examined disruptions in actin cytoskeleton of glioblastoma multiforme in vitro model—A172 cell line, caused by EHV-1 infection. We used three EHV-1 strains: two non-neuropathogenic (Jan-E and Rac-H) and one neuropathogenic (EHV-1 26). Immunofluorescent labelling, confocal microscopy, real-time cell growth analysis and Oris^TM cell migration assay revealed disturbed migration of A172 cells infected with the EHV-1, probably due to rearrangement of actin cytoskeleton and the absence of cell projections. All tested strains caused disruption of the actin network and general depolymerization of microfilaments. The qPCR results confirmed the effective replication of EHV-1. Thus, we have demonstrated, for the first time, that EHV-1 infection leads to inhibition of proliferation and migration in A172 cells, which might be promising for new immunotherapy treatment.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): infection with Equine Herpesvirus-1

Equine Herpesvirus-1 infection has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of: Article 7 on disease profile and impacts, Article 5 on the eligibility of the disease to be listed, Article 9 for the categorisation of the disease according to disease prevention and control measures as in Annex IV and Article 8 on the list of animal species related to Equine Herpesvirus-1 infection. The assessment has been performed following a methodology composed of information collection and compilation, and expert judgement on each criterion at individual and collective level. The outcome is the median of the probability ranges provided by the experts, which indicates whether the criterion is fulfilled (66-100%) or not (0-33%), or whether there is uncertainty about fulfilment (33-66%). For the questions where no consensus was reached, the different supporting views are reported. According to the assessment performed, Equine Herpesvirus-1 infection can be considered eligible to be listed for Union intervention according to Article 5 of the Animal Health Law with 33-90% certainty. According to the criteria as in Annex IV of the AHL related to Article 9 of the AHL for the categorisation of diseases according to the level of prevention and control, it was assessed with less than 1% certainty that EHV-1 fulfils the criteria as in Section 1 (category A), 1-5% for the criteria as in Section 2 (category B), 10-66% for the criteria as in Section 3 (category C), 66-90% for the criteria as in Section 4 (category D) and 33-90% for the criteria as in Section 5 (category E). The animal species to be listed for EHV-1 infection according to Article 8(3) criteria are the species belonging to the families of Equidae, Bovidae, Camelidae, Caviidae, Cervidae, Cricetidae, Felidae, Giraffidae, Leporidae, Muridae, Rhinocerontidae, Tapiridae and Ursidae.

Caprine herpesvirus 1 (CpHV-1) as a potential candidate for oncolytic virotherapy

Caprine Herpesvirus type 1 (CpHV-1) is a species-specific herpes virus able to induce apoptosis in several biological systems. In the present study we aimed to investigate the ability of CpHV-1 to reduce cells viability, to replicate and to cause cell death also in human cancer cell lines. We tested the CpHV-1 effects on HEL-299, Vero, MDA-MB-468, HeLa, U2OS, PC3, A549 and K562 neoplastic cell lines and on MDBK cells. Firstly, we evaluated the effect of CpHV-1 infection on cell viability by MTT assay and our data showed that CpHV-1 can induce a marked cytopathic effect (CPE) in most of cell lines tested, except for HEL-299, Vero and K562 cells. The reduction of cell viability was associated with a significant increase of viral production. We next investigated if CpHV-1 was able to induce cell death and so through western blotting analysis we evaluated cleaved caspase 3, LC3II and p62 protein levels after infection. Caspase 3 activation was detected in MDBK cells and, even if at different times p.i., also in MDA-MB-468, U2OS, and PC3 cell lines, while LC3II increase and concomitant p62 protein reduction were observed only in U2OS, and A549 cells, no significant alteration of these proteins was observed in the other cell lines tested. Finally, to confirm virus ability to trigger apoptosis we performed an Annexin-V apoptosis test after 24 h p.i. Although we need to further explore mechanisms underlying CpHV-1 treatment, this study could serve as the basis for the development of new treatment options aiming to fight several cancer types.

Programmed cell death: the battlefield between the host and alpha-herpesviruses and a potential avenue for cancer treatment

Programed cell death is an antiviral mechanism by which the host limits viral replication and protects uninfected cells. Many viruses encode proteins resistant to programed cell death to escape the host immune defenses, which indicates that programed cell death is more favorable for the host immune defense. Alpha-herpesviruses are pathogens that widely affect the health of humans and animals in different communities worldwide. Alpha-herpesviruses can induce apoptosis, autophagy and necroptosis through different molecular mechanisms. This review concisely illustrates the different pathways of apoptosis, autophagy, and necroptosis induced by alpha-herpesviruses. These pathways influence viral infection and replication and are a potential avenue for cancer treatment. This review will increase our understanding of the role of programed cell death in the host immune defense and provides new possibilities for cancer treatment.

Bovine herpesviruses induce different cell death forms in neuronal and glial-derived tumor cell cultures

Oncolytic viruses have the ability to infect tumor cells and leave healthy cells intact. In this study, bovine herpesvirus 1 (BHV1; Los Angeles, Cooper, and SV56/90 strains) and bovine herpesvirus 5 (BHV5; SV507/99 and GU9457818 strains) were used to infect two neuronal tumor cell lineages: neuro2a (mouse neuroblastoma cells) and C6 (rat glial cells). BHV1 and BHV5 strains infected both cell lines and positively correlated with viral antigen detection (p < 0.005). When neuro2a cells were infected by Los Angeles, SV507/99, and GU9457818 strains, 40 % of infected cells were under early apoptosis and necroptosis pathways. Infected C6 cells were >40 % in necroptosis phase when infected by BHV5 (GU9457818 strain). Blocking caspase activation did not interfere with cell death. However, when necroptosis was blocked, 60-80 % of both infected cells with either virus switched to early apoptosis pathway with no interference with virus replication. Moreover, reactive oxygen species production and mitochondrial membrane dysfunction were detected at high levels in both infected cell lines. In spite of apoptosis and necroptosis blockage, tumor necrosis factor alpha (TNFA) and virus transcription were positively correlated for all viral strains studied. Thus, these results contribute to the characterization of BHV1 and BHV5 as potential oncolytic viruses for non-human cells. Nonetheless, the mechanisms underlying their oncolytic activity in human cells are still to be determined.

Overcoming Barriers in Oncolytic Virotherapy with HDAC Inhibitors and Immune Checkpoint Blockade

Oncolytic viruses (OVs) target and destroy cancer cells while sparing their normal counterparts. These viruses have been evaluated in numerous studies at both pre-clinical and clinical levels and the recent Food and Drug Administration (FDA) approval of an oncolytic herpesvirus-based treatment raises optimism that OVs will become a therapeutic option for cancer patients. However, to improve clinical outcome, there is a need to increase OV efficacy. In addition to killing cancer cells directly through lysis, OVs can stimulate the induction of anti-tumour immune responses. The host immune system thus represents a "double-edged sword" for oncolytic virotherapy: on the one hand, a robust anti-viral response will limit OV replication and spread; on the other hand, the immune-mediated component of OV therapy may be its most important anti-cancer mechanism. Although the relative contribution of direct viral oncolysis and indirect, immune-mediated oncosuppression to overall OV efficacy is unclear, it is likely that an initial period of vigorous OV multiplication and lytic activity will most optimally set the stage for subsequent adaptive anti-tumour immunity. In this review, we consider the use of histone deacetylase (HDAC) inhibitors as a means of boosting virus replication and lessening the negative impact of innate immunity on the direct oncolytic effect. We also discuss an alternative approach, aimed at potentiating OV-elicited anti-tumour immunity through the blockade of immune checkpoints. We conclude by proposing a two-phase combinatorial strategy in which initial OV replication and spread is maximised through transient HDAC inhibition, with anti-tumour immune responses subsequently enhanced by immune checkpoint blockade.

Designing Herpes Viruses as Oncolytics

Oncolytic herpes simplex virus (oHSV) was one of the first genetically-engineered oncolytic viruses. Because herpes simplex virus (HSV) is a natural human pathogen that can cause serious disease, it is incumbent that it be genetically-engineered or significantly attenuated for safety. Here we present a detailed explanation of the functions of HSV-1 genes frequently mutated to endow oncolytic activity. These genes are non-essential for growth in tissue culture cells but are important for growth in post-mitotic cells, interfering with intrinsic antiviral and innate immune responses or causing pathology, functions dispensable for replication in cancer cells. Understanding the function of these genes leads to informed creation of new oHSVs with better therapeutic efficacy. Virus infection and replication can also be directed to cancer cells through tumor-selective receptor binding and transcriptional- or post-transcriptional miRNA-targeting, respectively. In addition to the direct effects of oHSV on infected cancer cells and tumors, oHSV can be 'armed' with transgenes that are: reporters, to track virus replication and spread; cytotoxic, to kill uninfected tumor cells; immune modulatory, to stimulate anti-tumor immunity; or tumor microenvironment altering, to enhance virus spread or to inhibit tumor growth. In addition to HSV-1, other alphaherpesviruses are also discussed for their oncolytic activity.