Equine herpesvirus type 1 modulates inflammatory host immune response genes in equine endothelial cells

Unmasking the ongoing challenge of equid herpesvirus- 1 (EHV-1): A comprehensive review

Equid herpesviruses (EHVs) are a group of highly impactful viral pathogens that affect horses, presenting a substantial risk to the global equine industry. Among these, equid herpesvirus-1 (EHV-1) primarily causes respiratory infections. However, its ability to spread to distant organs can lead to severe consequences such as abortion and neurological diseases. These viruses can enter a dormant phase, with minimal activity, and later reactivate to trigger active infections at any time. Recently, there has been a notable rise in the prevalence of a particularly devastating strains of EHV-1 known as equid herpesviral myeloencephalopathy (EHM). In the light of dynamic nature of EHV-1, this review provides a thorough overview of EHV-1 and explores how advances in viral biology affect the pathophysiology of viral infection. The information presented here is crucial for understanding the dynamics of EHV-1 infections and creating practical plans to stop the virus's global spread among equid populations.

Equine Endothelial Cells Show Pro-Angiogenic Behaviours in Response to Fibroblast Growth Factor 2 but Not Vascular Endothelial Growth Factor A

Understanding the factors which control endothelial cell (EC) function and angiogenesis is crucial for developing the horse as a disease model, but equine ECs remain poorly studied. In this study, we have optimised methods for the isolation and culture of equine aortic endothelial cells (EAoECs) and characterised their angiogenic functions in vitro. Mechanical dissociation, followed by magnetic purification using an anti-VE-cadherin antibody, resulted in EC-enriched cultures suitable for further study. Fibroblast growth factor 2 (FGF2) increased the EAoEC proliferation rate and stimulated scratch wound closure and tube formation by EAoECs on the extracellular matrix. Pharmacological inhibitors of FGF receptor 1 (FGFR1) (SU5402) or mitogen-activated protein kinase (MEK) (PD184352) blocked FGF2-induced extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and functional responses, suggesting that these are dependent on FGFR1/MEK-ERK signalling. In marked contrast, vascular endothelial growth factor-A (VEGF-A) had no effect on EAoEC proliferation, migration, or tubulogenesis and did not promote ERK1/2 phosphorylation, indicating a lack of sensitivity to this classical pro-angiogenic growth factor. Gene expression analysis showed that unlike human ECs, FGFR1 is expressed by EAoECs at a much higher level than both VEGF receptor (VEGFR)1 and VEGFR2. These results suggest a predominant role for FGF2 versus VEGF-A in controlling the angiogenic functions of equine ECs. Collectively, our novel data provide a sound basis for studying angiogenic processes in horses and lay the foundations for comparative studies of EC biology in horses versus humans.

Anti-inflammatory compounds reduce equine herpesvirus type 1 replication and cell-to-cell spread

Equine herpesvirus type 1 (EHV-1) is a highly transmissible pathogen that leads to a variety of clinical disease outcomes in infected horses. A major sequela that can occur after an EHV-1 infection is a neurological disease termed equine herpesvirus myeloencephalopathy (EHM). Clinical manifestations of EHM include fever, ataxia, incontinence, and partial to full paralysis, which may ultimately lead to the euthanization of the infected horse. To develop an effective treatment strategy for EHM, it is critical that the specific virus-host interactions that lead to EHM be investigated so that safe and effective therapeutic interventions can be developed and delivered. In this study, we examined the ability of four non-steroidal anti-inflammatory drugs (NSAIDs), a steroidal anti-inflammatory drug (dexamethasone), a Rho-kinase (ROCK) inhibitor, and a JAK/STAT inhibitor (AG490) to reduce EHV-1 virus yields and cell-to-cell spread. We show that the NSAID, flunixin meglumine (FM), and the JAK/STAT inhibitor, AG490, significantly reduced virus yields in endothelial and epithelial cell lines, and this inhibition was similar for two neurologic and two non-neurologic EHV-1 strains. In addition to reducing virus yields, AG490 and FM also significantly reduced the ability of EHV-1 to spread laterally from cell to cell.

Molecular characteristics and pathogenicity of an equid alphaherpesvirus 1 strain isolated in China

Equid alphaherpesvirus 1 (EHV-1) is prevalent in China, and causes notable economic damage to the equine industry. However, there is no information regarding the molecular characteristics and pathogenicity of the Chinese strains. Therefore, an EHV-1 strain, named YM2019, was isolated from the lung tissue of an aborted horse fetus in Xinjiang, China, and its genome and pathogenicity were analyzed. The full genome of the isolate was 150,267 base pairs in length, with 56.7% G + C content. Genetic and phylogenetic analysis showed that strain YM2019 (GenBank: MT063054) belonged to the ORF30 N752 genotype but displayed a high level of similarity with strain Ab4 (ORF30 D752, GenBank: AY665713) isolated in Britain. Fourteen unique amino acid mutations were found when comparing strain YM2019 with the reference strains Ab4 and V592 (ORF30 N752, GenBank: AY464052). Syrian hamsters infected with strain YM2019 exhibited severe respiratory and neurological clinical signs and died. Infection with strain YM2019 in Yili horses caused rhinopneumonitis, viremia, and neurological clinical signs such as hind limb lameness, prostration, and reduced movement. Here, we describe the features of an EHV-1 strain discovered in China, together with the complete genome sequence, and reveal that a nonneurovirulent strain (ORF30 N752) can also cause neurological signs in horses. The data will be useful in providing some reference for further research into the relationship between viral genotypes and pathogenicity.

Contribution of the immune response to the pathogenesis of equine herpesvirus-1 (EHV-1): Are there immune correlates that predict increased risk or protection from EHV-1 myeloencephalopathy?

Equine herpesvirus-1 (EHV-1) myeloencephalopathy (EHM) is a devastating consequence of EHV-1 infection that has significant economic consequences. However, clinical EHM is relatively rare and occurs in only approximately 10% of infected horses. While there is a positive correlation between the duration and magnitude of viremia and incidence of EHM, it is likely that a combination of host and viral factors determine whether EHM occurs. The identification of these factors is of high interest for the equine community and has been the topic of much research for vaccine development and to predict which horses might be most at risk for developing EHM. The aim of this review is to highlight host immunity contributions to EHM pathogenesis at different sites of EHV-1 infection to shed light on the different aspects and interdependence of the response to EHV-1 in the time course of infection.

Pathogenesis of Equid Alphaherpesvirus 1 Infection in the Central Nervous System of Mice

Equid alphaherpesvirus 1 (EHV-1) causes myeloencephalopathy in horses and occasionally in non-equid species. Although mouse models have been developed to understand EHV-1 pathogenesis, few EHV-1 strains have been identified as highly neurovirulent to mice. The aim of this study was to evaluate the pathogenesis of 2 neurovirulent EHV-1 strains in mice, and to characterize the inflammatory cells and expression of chemokines and the apoptosis marker caspase-3 in the brain of infected mice. C57BL/6J mice were inoculated intranasally with EHV-1 strains A4/72 or A9/92 and evaluated on 1, 2, and 3 days post inoculation (DPI). EHV-1-infected mice showed severe neurological signs at 3 DPI. Ultrastructural analysis revealed numerous viral nucleocapsids and fewer enveloped virions within degenerated and necrotic neurons and in the surrounding neuropil. Histologically, at 3 DPI, there was severe diffuse neuronal degeneration and liquefactive necrosis, prominent microgliosis, and perivascular cuffing composed of CD3+ cells (T cells) and Iba-1+ cells (macrophages), mainly in the olfactory bulb and ventral portions of the brain. In these areas, moderate numbers of neuroglial cells expressed CCL5 and CCL2 chemokines. Numerous neurons, including those in less affected areas, were immunolabeled for cleaved caspase-3. In conclusion, neurovirulent EHV-1 strains induced a fulminant necrotizing lymphohistiocytic meningoencephalitis in mice, with microgliosis and expression of chemokines and caspase-3. This model will be useful for understanding the mechanisms underlying the extensive neuropathology induced by these viral infections.

Equine herpesvirus 1 elicits a strong pro-inflammatory response in the brain of mice

Equine herpesvirus type 1 (EHV-1) is an emerging pathogen that causes encephalomyelitis in horses and non-equid species. Several aspects of the immune response in the central nervous system (CNS), mainly regarding the role of inflammatory mediators during EHV-1 encephalitis, remain unknown. Moreover, understanding the mechanisms underlying extensive neuropathology induced by viruses would be helpful to establish therapeutic strategies. Therefore, we aimed to evaluate some aspects of the innate immune response during highly neurovirulent EHV-1 infection. C57BL/6 mice infected intranasally with A4/72 and A9/92 EHV-1 strains developed a fulminant neurological disease at 3 days post-inoculation with high viral titres in the brain. These mice developed severe encephalitis with infiltration of monocytes and CD8⁺ T cells to the brain. The inflammatory infiltrate followed the detection of the chemokines CCL2, CCL3, CCL4, CCL5, CXCL2, CXCL9 and CXCL-10 in the brain. Notably, the levels of CCL3, CCL4, CCL5 and CXCL9 were higher in A4/72-infected mice, which presented higher numbers of inflammatory cells within the CNS. Pro-inflammatory cytokines, such as interleukins (ILs) IL-1α, IL-1β, IL-6, IL-12β, and tumour necrosis factor (TNF), were also detected in the CNS, and Toll-like receptor (TLR) TLR2, TLR3 and TLR9 genes were also upregulated within the brain of EHV-1-infected mice. However, no expression of interferon-γ (IFN-γ) and IL-12α, which are important for controlling the replication of other herpesviruses, was detected in EHV-1-infected mice. The results show that the activated innate immune mechanisms could not prevent EHV-1 replication within the CNS, but most likely contributed to the extensive neuropathology. The mouse model of viral encephalitis proposed here will also be useful to study the mechanisms underlying extensive neuropathology.

Transcriptomic Profiling of Equine and Viral Genes in Peripheral Blood Mononuclear Cells in Horses during Equine Herpesvirus 1 Infection

Equine herpesvirus 1 (EHV-1) affects horses worldwide and causes respiratory disease, abortions, and equine herpesvirus myeloencephalopathy (EHM). Following infection, a cell-associated viremia is established in the peripheral blood mononuclear cells (PBMCs). This viremia is essential for transport of EHV-1 to secondary infection sites where subsequent immunopathology results in diseases such as abortion or EHM. Because of the central role of PBMCs in EHV-1 pathogenesis, our goal was to establish a gene expression analysis of host and equine herpesvirus genes during EHV-1 viremia using RNA sequencing. When comparing transcriptomes of PBMCs during peak viremia to those prior to EHV-1 infection, we found 51 differentially expressed equine genes (48 upregulated and 3 downregulated). After gene ontology analysis, processes such as the interferon defense response, response to chemokines, the complement protein activation cascade, cell adhesion, and coagulation were overrepresented during viremia. Additionally, transcripts for EHV-1, EHV-2, and EHV-5 were identified in pre- and post-EHV-1-infection samples. Looking at micro RNAs (miRNAs), 278 known equine miRNAs and 855 potentially novel equine miRNAs were identified in addition to 57 and 41 potentially novel miRNAs that mapped to the EHV-2 and EHV-5 genomes, respectively. Of those, 1 EHV-5 and 4 equine miRNAs were differentially expressed in PBMCs during viremia. In conclusion, this work expands our current knowledge about the role of PBMCs during EHV-1 viremia and will inform the focus on future experiments to identify host and viral factors that contribute to clinical EHM.

Association of RANTES gene polymorphisms with susceptibility to childhood asthma: A meta-analysis

BACKGROUND

Previous investigations have illustrated that regulated upon activation, normal T-cell expressed and secreted (RANTES) polymorphisms are linked to susceptibility to childhood asthma; nevertheless, the findings continue to be controversial. Accordingly, we conducted the present meta-analysis to clarify the impact of RANTES genetic polymorphisms (-403G/A and -28C/G) on childhood asthma vulnerability.

METHODS

A search for published literature was performed using the PubMed, EMBASE, Chinese National Infrastructure, Cochrane Library, Scopus, Web of Science, and WanFang databases and selected in the form of PICOS (participants, interventions, comparisons, outcomes, and study design) to identify all eligible research works. The link between RANTES genetic polymorphisms and childhood asthma susceptibility was evaluated by a pooled odds ratio with a 95% confidence interval.

RESULTS

In total, 14 case-control studies were included in the analysis. No significant association existed between risk of childhood asthma and the -403G/A polymorphism subjected to any genetic framework in the overall population. In the stratified analysis, according to ethnicity, the -403G/A polymorphism was linked to augmented vulnerability to childhood asthma in Caucasians (allelic model: odds ratio [OR] = 1.63, 95% confidence interval [CI] = 1.04-2.57, P = .034; codominant model: OR = 2.20, 95% CI = 1.28-3.78, P = .004; dominant model: OR = 1.78, 95% CI = 1.01-3.13, P = .047; and recessive model: OR = 1.92, 95% CI = 1.11-3.30, P = .019). For the stratified analysis by atopic status, the -403G/A polymorphism was linked to augmented childhood asthma in the codominant (OR = 1.39, 95% CI = 1.02-1.91, P = .037) and dominant models (OR = 1.43, 95% CI = 1.02-2.01, P = .037) in atopic asthma. For the -28C/G polymorphism, there was a significant association between childhood asthma and the -28C/G variant (allelic model: OR = 1.33, 95% CI = 1.08-1.65, P = .009; codominant framework: OR = 2.14, 95% CI = 1.47-3.10, P < .001; dominant model: OR = 1.44, 95% CI = 1.07-1.93, P = .017; and recessive model: OR = 2.08, 95% CI = 1.44-3.02, P < .001). Stratified analysis based on ethnicity and the -28C/G polymorphism was linked to augmented vulnerability to childhood asthma in Asian and Caucasian populations. For the subgroup analysis by atopic status, no association was found in atopic and non-atopic asthma.

CONCLUSION

The present meta-analysis indicated that the RANTES -403G/A and -28C/G polymorphisms contributed to the development of childhood asthma.

Endothelial cells and angiogenesis in the horse in health and disease-A review

The cardiovascular system is the first functional organ in the embryo, and its blood vessels form a widespread conductive network within the organism. Blood vessels develop de novo, by the differentiation of endothelial progenitor cells (vasculogenesis) or by angiogenesis, which is the formation of new blood vessels from existing ones. This review presents an overview of the current knowledge on physiological and pathological angiogenesis in the horse including studies on equine endothelial cells. Principal study fields in equine angiogenesis research were identified: equine endothelial progenitor cells; equine endothelial cells and angiogenesis (heterogeneity, markers and assessment); endothelial regulatory molecules in equine angiogenesis; angiogenesis research in equine reproduction (ovary, uterus, placenta and conceptus, testis); angiogenesis research in pathological conditions (tumours, ocular pathologies, equine wound healing, musculoskeletal system and laminitis). The review also includes a table that summarizes in vitro studies on equine endothelial cells, either describing the isolation procedure or using previously isolated endothelial cells. A particular challenge of the review was that results published are fragmentary and sometimes even contradictory, raising more questions than they answer. In conclusion, angiogenesis is a major factor in several diseases frequently occurring in horses, but relatively few studies focus on angiogenesis in the horse. The challenge for the future is therefore to continue exploring new therapeutic angiogenesis strategies for horses to fill in the missing pieces of the puzzle.

EHV-1: A Constant Threat to the Horse Industry

Equine herpesvirus-1 (EHV-1) is one of the most important and prevalent viral pathogens of horses and a major threat to the equine industry throughout most of the world. EHV-1 primarily causes respiratory disease but viral spread to distant organs enables the development of more severe sequelae; abortion and neurologic disease. The virus can also undergo latency during which viral genes are minimally expressed, and reactivate to produce lytic infection at any time. Recently, there has been a trend of increasing numbers of outbreaks of a devastating form of EHV-1, equine herpesviral myeloencephalopathy. This review presents detailed information on EHV-1, from the discovery of the virus to latest developments on treatment and control of the diseases it causes. We also provide updates on recent EHV-1 research with particular emphasis on viral biology which enables pathogenesis in the natural host. The information presented herein will be useful in understanding EHV-1 and formulating policies that would help limit the spread of EHV-1 within horse populations.

Absence of relationship between type-I interferon suppression and neuropathogenicity of EHV-1

Equine herpesvirus-1 (EHV-1) infection is an important and highly prevalent disease in equine populations worldwide. Previously we have demonstrated that a neuropathogenic strain of EHV-1, T953, suppresses the host cell's antiviral type-I interferon (IFN) response in vitro. Whether or not this is unique to EHV-1 strains possessing the neuropathogenic genotype has been undetermined. Here, we examined whether there is any direct relationship between neuropathogenic genotype and the induced IFN-β response in equine endothelial cells (EECs) infected with 10 different strains of EHV-1. The extent of virus cell-to-cell spread following infection in EECs was also compared between the neuropathogenic and the non-neuropathogenic genotype of EHV-1. We then compared IFN-β and the total type-I IFN protein suppression between T953, an EHV-1 strain that is neuropathogenic and T445, an EHV-4 strain mainly associated only with respiratory disease. Data from our study revealed no relationship between the neuropathogenic genotype of EHV-1 and the induced IFN-β mRNA by the host cell. Results also indicate no statistically significant difference in plaque sizes of both genotypes of EHV-1 produced in EECs. However, while the T953 strain of EHV-1 was able to suppress IFN-β mRNA and type-I IFN biological activity at 12 h post-infection (hpi), EHV-4 weakly induces both IFN-β mRNA and type-I IFN biological activity. This finding correlated with a statistically significant difference in the mean plaque sizes produced by the two EHV subtypes in EECs. Our data help illuminate how EHV-1, irrespective of its genotype, evades the host cell's innate immune response thereby enabling viral spread to susceptible cells.