Characterization of the Ictalurid herpesvirus 1 immediate-early gene ORF24 and its potential role in transcriptional regulation in yeast.

Herpesviruses adhere to a precise temporal expression model in which immediate-early (IE) genes play a crucial role in regulating the viral life cycle. However, there is a lack of functional research on the IE genes in Ictalurid herpesvirus 1 (IcHV-1). In this study, we identified the IcHV-1 ORF24 as an IE gene via a metabolic inhibition assay, and subcellular analysis indicated its predominant localisation in the nucleus. To investigate its function, we performed yeast reporter assays using an ORF24 fusion protein containing the Gal4-BD domain and found that BD-ORF24 was able to activate HIS3/lacZ reporter genes without the Gal4-AD domain. Our findings provide concrete evidence that ORF24 is indeed an IE gene that likely functions as a transcriptional regulator during IcHV-1 infection. This work contributes to our understanding of the molecular mechanisms underlying fish herpesvirus IE gene expression.

Bovine Parainfluenza Virus 3 and Bovine Respiratory Syncytial Virus: Dominant Viral Players in Bovine Respiratory Disease Complex among Serbian Cattle.

Bovine respiratory disease complex, a complex respiratory ailment in cattle, results from a combination of viral and bacterial factors, compounded by environmental stressors such as overcrowding, transportation, and adverse weather conditions. Its impact extends beyond mere health concerns, posing significant economic threats to the cattle industry. This study presents an extensive investigation into viral pathogens associated with BRDC in Serbian cattle, utilizing serum samples and nasal swabs. A cross-sectional study was conducted in 2024 across 65 randomly selected dairy farms in Serbia, excluding farms with vaccinated cattle. The farms were categorized by their livestock count: small (≤50 animals), medium (51-200 animals), and large (>200 animals). Serum samples from adult cattle older than 24 months were tested for antibodies against BVDV, BHV-1, BRSV, and BPIV3. Nasal swab samples from the animals with respiratory signs were tested using PCR for viral genome detection. The results showed seropositivity for all four viruses across all of the farms, with BPIV3 exhibiting universal seropositivity. Medium-sized and large farms demonstrated higher levels of seropositivity for BRSV and BHV-1 compared to small farms (p < 0.05). Our true seroprevalence estimates at the animal level were 84.29% for BRSV, 54.08% for BVDV, 90.61% for BHV-1, and 84.59% for BPIV3. A PCR analysis of the nasal swabs revealed positive detections for BRSV (20%), BHV-1 (1.7%), BVDV (8%), and BPIV3 (10.9%). Influenza D virus was not found in any of the samples. This study provides critical insights into the prevalence and circulation of viral pathogens associated with BRDC in Serbian cattle, emphasizing the importance of surveillance and control measures to mitigate the impact of respiratory diseases in cattle populations.

Impact of the host immune response on the development of equine herpesvirus myeloencephalopathy in horses.

Herpesviruses establish a well-adapted balance with their host's immune system. Despite this co-evolutionary balance, infections can lead to severe disease including neurological disorders in their natural host. In horses, equine herpesvirus 1 (EHV-1) causes respiratory disease, abortions, neonatal foal death and myeloencephalopathy (EHM) in ~10 % of acute infections worldwide. Many aspects of EHM pathogenesis and protection from EHM are still poorly understood. However, it has been shown that the incidence of EHM increases to >70 % in female horses >20 years of age. In this study we used old mares as an experimental equine EHV-1 model of EHM to identify host-specific factors contributing to EHM. Following experimental infection with the neuropathogenic strain EHV-1 Ab4, old mares and yearling horses were studied for 21 days post-infection. Nasal viral shedding and cell-associated viremia were assessed by quantitative PCR. Cytokine/chemokine responses were evaluated in nasal secretions and cerebrospinal fluid (CSF) by Luminex assay and in whole blood by quantitative real-time PCR. EHV-1-specific IgG sub-isotype responses were measured by ELISA. All young horses developed respiratory disease and a bi-phasic fever post-infection, but only 1/9 horses exhibited ataxia. In contrast, respiratory disease was absent in old mares, but all old mares developed EHM that resulted in euthanasia in 6/9 old mares. Old mares also presented significantly decreased nasal viral shedding but higher viremia coinciding with a single fever peak at the onset of viremia. According to clinical disease manifestation, horses were sorted into an EHM group (nine old horses and one young horse) and a non-EHM group (eight young horses) for assessment of host immune responses. Non-EHM horses showed an early upregulation of IFN-α (nasal secretions), IRF7/IRF9, IL-1ß, CXCL10 and TBET (blood) in addition to an IFN-γ upregulation during viremia (blood). In contrast, IFN-α levels in nasal secretions of EHM horses were low and peak levels of IRF7, IRF9, CXCL10 and TGF-ß (blood) coincided with viremia. Moreover, EHM horses showed significantly higher IL-10 levels in nasal secretions, peripheral blood mononuclear cells and CSF and higher serum IgG3/5 antibody titres compared to non-EHM horses. These results suggest that protection from EHM depends on timely induction of type 1 IFN and upregulation cytokines and chemokines that are representative of cellular immunity. In contrast, induction of regulatory or TH-2 type immunity appeared to correlate with an increased risk for EHM. It is likely that future vaccine development for protection from EHM must target shifting this 'at-risk' immunophenotype.

Development and analytical validation of a novel quantitative PCR assay for the detection of Trachemys herpesvirus 1.

Emerging infectious diseases are a threat that contributes to the decline of global chelonian species. Herpesviruses are among the most impactful pathogens described in chelonians and are frequently associated with a range of presentations across hosts with the potential for severe morbidity and mortality. Trachemys herpesvirus 1 (TrHV1) has been reported in red-eared and yellow-bellied sliders (Trachemys scripta elegans and Trachemys scripta scripta, respectively) but is largely understudied. Invasive red-eared sliders may serve as a reservoir for transmission to sympatric native species. This study aimed to develop a sensitive and specific quantitative real-time PCR (qPCR) assay for the detection of TrHV1 DNA to aid in the characterization of the epidemiology of this virus in aquatic turtles. Two TaqMan-MGB FAM-dye labeled primer-probe sets were designed and evaluated using plasmid dilutions. The higher performing assay was specific for TrHV1 DNA and had a linear dynamic range of 1.0 × 107 to 1.0 × 101 copies per reaction with an R2 of 0.999, slope of -3.386, and efficiency of 97.39%. The limit of detection was 101 copies per reaction, and there was no loss of reaction efficiency in the presence of TrHV1-negative chelonian oral-cloacal DNA. Overall, the Trachemys herpesvirus 1 assay meets established criteria for acceptable qPCR assays and will be a valuable tool in characterizing the epidemiology of Trachemys herpesvirus 1 in chelonians.

HPV related p16INK4A and HSV in benign and potentially malignant oral mucosa pathologies.

BACKGROUND: The association of Human Papilloma Virus (HPV) and Human Syncytial Virus (HSV) infection with inflammatory and potentially malignant disorders of the oral cavity (OPMD) is unknown. The aim of this cross-sectional study was to stablish the expression of the p16INK4A and HSV proteins, to test potential correlation between those parameters in biopsies from clinically diagnosed oral lesions. METHODS: Immunochemical analysis of 211 formalin-fixed, paraffin-embedded (FFPE) blocks from 211 individuals was provided. The clinical diagnosis included in the research were Oral lichen planus (N = 30), Oral Leukoplakia (N = 13) Mucocele (N = 25), Erosion/ulceration/ inflammation of mucosa (N = 8), Overgrowth of mucosa (N = 135). RESULTS: Two hundred eleven analyzed FFPE samples resulted with the median age of 58.5 years (the average age 54.0 years and SD ± 17 years). The female/male ratio was 2.3 (69.7% vs 30.3% respectively). All the samples positive for HSV also expressed p16INK4A (p = 0.000), that's showed various levels of association with the diverse clinical diagnosis reaching the higher level in OM 49.1% (29 positive samples) and OLP 30.5% (18). p16INK4A was associated with OLP at 30.5% (18), and fibroma 30.5%. HSV expression was mostly present in fibroma at 47.6% (10 positive samples). CONCLUSION: HSV and p16INK4A positivity in relation to diagnosis of the biopsies showed statistically most often p16INK4A in OLP and fibroma. The results of co-expression of p16INK4A and HSV in mucocele and fibroma in oral mucosa suggest a cooperation between the molecular alterations induced by these two viruses. Squamous papilloma samples positive for p16INK4A were also positive for HSV, suggesting that the putative pro-oncogenic action of HSV could be an early event.

Development and evaluation of a time-resolved fluorescence labelled immunochromatographic strip assay for rapid and quantitative detection of bovine herpesvirus 1.

Bovine herpes virus 1 (BoHV-1) causes a wide variety of diseases in wild and domestic cattle. The most widely used method for viral identification is real-time PCR, which can only be performed in laboratories using sophisticated instruments by expert personnel. Herein, we developed an ultrasensitive time-resolved fluorescence lateral flow immunochromatographic strip (ICS) assay for detecting BoHV-1 in bovine samples using a monoclonal antibody against BoHV-1 labelled with fluorescent microspheres, which can be applied in any setting. The intact process from sample collection to final result can be achieved in 15 min. The limit of detection of the assay for BoHV-1 was 102 TCID50/100 µL. The coincidence rate of the ICS method and real-time PCR recommended by the World Organization for Animal Health (WOAH) was 100% for negative, 92.30% for positive, and 95.42% for total, as evaluated by the detection of 131 clinical samples. This detection method was specifically targeted to BoHV-1, not exhibiting cross-reactivity with other bovine pathogens including BoHV-5. We developed an ICS assay equipped with a portable instrument that offers a sensitive and specific platform for the rapid and reliable detection of BoHV-1 in the field. The Point-of-Care test of BoHV-1 is suitable for the screening and surveillance of BoHV-1 in dairy herds.

First molecular confirmation of cyprinid herpesvirus 1 (CyHV1) in diseased carp in Serbia.

Mass mortality of farmed 1 yr old common carp Cyprinus carpio occurred at a carp farm in April 2022. In addition to high mortality, diseased fish exhibited papillomatous growths on the skin and fins, characteristic of carp pox. To investigate a possible viral cause, tissue samples were collected and nucleic acid was extracted using standard procedures. In a pooled sample from the gills and kidneys, carp edema virus (CEV) was detected by real-time PCR. In a skin tissue sample with papillomatous growths, cyprinid herpesvirus 1 (CyHV1) was detected by a conventional PCR targeting a conserved region of the DNA polymerase of cyprinid herpesviruses. PCR products were visualized through agarose gel electrophoresis, and the presence of CyHV1 DNA was confirmed by Sanger sequencing. This represents the first molecular confirmation of CyHV1 in common carp in Serbia.

No vaccine interference between bovine coronavirus and bovine herpesvirus-1 in a randomized trial when coadministrating two intranasal modified-live viral vaccines to neonatal calves.

OBJECTIVE: Compare immune responses induced by 2 commercial intranasal (IN) modified-live viral (MLV) vaccines given individually or coadministered and evaluate prevention of infection and lung pathology following bovine herpesvirus-1 (BHV-1) challenge. ANIMALS: 36 male Holstein calves (ages, 5 to 12 days). METHODS: In a randomized complete block design, each calf received an IN injection of either vaccine diluent (Placebo), an MLV vaccine containing bovine herpesvirus-1 (BHV-1; N3), bovine coronavirus vaccine (BC), or both N3 and BC (BC + N3) with a booster 4 weeks later. Nasal secretions and blood were collected weekly. Three weeks after the booster, the calves were challenged with BHV-1, sampled for virus shedding, and euthanized 10 days later to quantify lung pathology. The study period was September 7, 2020, to April 6, 2021. RESULTS: Calves were seropositive for BHV-1 and BC before vaccination. No significant difference in BC-specific serum immunoglobin G and nasal immunoglobin A antibody responses in the BC versus BC + N3 group or BHV-1-specific serum immunoglobin G and nasal immunoglobin A antibody responses in the N3 versus BC + N3 group. Cytokine responses to BHV-1 and BC did not differ among groups. BHV-1 shedding after challenge was significantly reduced in N3 groups versus Placebo and BC. There was a significant reduction in lung pathology in the N3 + BC group versus Placebo. CLINICAL RELEVANCE: This study provides evidence an MLV vaccine containing BHV-1 and an MLV BC vaccine can be coadministered to neonatal calves without significantly altering immune responses to the 2 viruses or compromising the prevention of BHV-1 respiratory disease. Calves receiving the BC + N3 vaccine had a significant reduction in lung pathology after BHV-1 aerosol challenge.

Updated ACVIM consensus statement on equine herpesvirus-1.

Equine herpesvirus-1 (EHV-1) is a highly prevalent and frequently pathogenic infection of equids. The most serious clinical consequences of infection are abortion and equine herpesvirus myeloencephalopathy (EHM). The previous consensus statement was published in 2009 and considered pathogenesis, strain variation, epidemiology, diagnostic testing, vaccination, outbreak prevention and control, and treatment. A recent survey of American College of Veterinary Internal Medicine large animal diplomates identified the need for a revision to this original consensus statement. This updated consensus statement is underpinned by 4 systematic reviews that addressed key questions concerning vaccination, pharmaceutical treatment, pathogenesis, and diagnostic testing. Evidence for successful vaccination against, or effective treatment of EHV-1 infection was limited, and improvements in experimental design and reporting of results are needed in future studies of this important disease. This consensus statement also updates the topics considered previously in 2009.

Herpes Simplex Viral Infection Doubles the Risk of Dementia in a Contemporary Cohort of Older Adults: A Prospective Study.

Background: Evidence indicates that herpes simplex virus (HSV) participates in the pathogenesis of Alzheimer's disease (AD). Objective: We investigated AD and dementia risks according to the presence of herpesvirus antibodies in relation to anti-herpesvirus treatment and potential APOE ɛ4 carriership interaction. Methods: This study was conducted with 1002 dementia-free 70-year-olds living in Sweden in 2001-2005 who were followed for 15 years. Serum samples were analyzed to detect anti-HSV and anti-HSV-1 immunoglobulin (Ig) G, anti-cytomegalovirus (CMV) IgG, anti-HSV IgM, and anti-HSV and anti-CMV IgG levels. Diagnoses and drug prescriptions were collected from medical records. Cox proportional-hazards regression models were applied. Results: Cumulative AD and all-cause dementia incidences were 4% and 7%, respectively. Eighty-two percent of participants were anti-HSV IgG carriers, of whom 6% received anti-herpesvirus treatment. Anti-HSV IgG was associated with a more than doubled dementia risk (fully adjusted hazard ratio = 2.26, p = 0.031). No significant association was found with AD, but the hazard ratio was of the same magnitude as for dementia. Anti-HSV IgM and anti-CMV IgG prevalence, anti-herpesvirus treatment, and anti-HSV and -CMV IgG levels were not associated with AD or dementia, nor were interactions between anti-HSV IgG and APOE ɛ4 or anti-CMV IgG. Similar results were obtained for HSV-1. Conclusions: HSV (but not CMV) infection may be indicative of doubled dementia risk. The low AD incidence in this cohort may have impaired the statistical power to detect associations with AD.

Genome sequence of bubaline herpesvirus-1 associated with pustular vulvovaginitis in Indian water buffalo.

We report here the genome sequence of a bubaline herpesvirus 1 isolated from Indian water buffalo. The bubaline herpesvirus 1 strain S102_1 was isolated in 2021 from a Murrah buffalo heifer with clinical presentation of pustular vulvovaginitis.

Pharmacologic interventions for the treatment of equine herpesvirus-1 in domesticated horses: A systematic review.

BACKGROUND: Equine herpes virus type 1 (EHV-1) infection in horses is associated with upper respiratory disease, neurological disease, abortions, and neonatal death. REVIEW QUESTION: Does pharmacological therapy decrease either the incidence or severity of disease or infection caused by EHV-1 in domesticated horses? METHODS: A systematic review was preformed searching AGRICOLA, CAB Abstracts, Cochrane, PubMed, Web of Science, and WHO Global Health Index Medicus Regional Databases to identify articles published before February 15, 2021. Selection criteria were original research reports published in peer reviewed journals, and studies investigating in vivo use of therapeutic agents for prevention or treatment of EHV-1 in horses. Outcomes assessed included measures related to clinical outcomes that reflect symptomatic EHV-1 infection or virus infection. We evaluated risk of bias and performed a GRADE evaluation of the quality of evidence for interventions. RESULTS: A total of 7009 unique studies were identified, of which 9 met the inclusion criteria. Two studies evaluated valacyclovir or small interfering RNAs, and single studies evaluated the use of a Parapoxvirus ovis-based immunomodulator, human alpha interferon, an herbal supplement, a cytosine analog, and heparin. The level of evidence ranged between randomized controlled studies and observational trials. The risk of bias was moderate to high and sample sizes were small. Most studies reported either no benefit or minimal efficacy of the intervention tested. CONCLUSIONS AND CLINICAL IMPORTANCE: Our review indicates minimal or limited benefit either as a prophylactic or post-exposure treatment for any of the studied interventions in the mitigation of EHV-1-associated disease outcome.

Saikosaponin B2, Punicalin, and Punicalagin in Vitro Block Cellular Entry of Feline Herpesvirus-1.

In the realm of clinical practice, nucleoside analogs are the prevailing antiviral drugs employed to combat feline herpesvirus-1 (FHV-1) infections. However, these drugs, initially formulated for herpes simplex virus (HSV) infections, operate through a singular mechanism and are susceptible to the emergence of drug resistance. These challenges underscore the imperative to innovate and develop alternative antiviral medications featuring unique mechanisms of action, such as viral entry inhibitors. This research endeavors to address this pressing need. Utilizing Bio-layer interferometry (BLI), we meticulously screened drugs to identify natural compounds exhibiting high binding affinity for the herpesvirus functional protein envelope glycoprotein B (gB). The selected drugs underwent a rigorous assessment to gauge their antiviral activity against feline herpesvirus-1 (FHV-1) and to elucidate their mode of action. Our findings unequivocally demonstrated that Saikosaponin B2, Punicalin, and Punicalagin displayed robust antiviral efficacy against FHV-1 at concentrations devoid of cytotoxicity. Specifically, these compounds, Saikosaponin B2, Punicalin, and Punicalagin, are effective in exerting their antiviral effects in the early stages of viral infection without compromising the integrity of the viral particle. Considering the potency and efficacy exhibited by Saikosaponin B2, Punicalin, and Punicalagin in impeding the early entry of FHV-1, it is foreseeable that their chemical structures will be further explored and developed as promising antiviral agents against FHV-1 infection.

Feline herpesvirus-1-related multiple respiratory eosinophilic nodules in an adult cat receiving long-term oral prednisolone.

Case summary: A 10-year-old male castrated domestic shorthair cat was presented for evaluation of a 3-day history of increased inspiratory effort. The cat had received prednisolone 1 mg/kg PO q24h for 1 year due to chronic diarrhea. On physical examination, the patient exhibited severe stridor, intermittent open-mouth breathing and bilateral mucopurulent nasal discharge. Subcutaneous emphysema was palpated over the dorsal cervical region. Mild hypoventilation (PvCO2 55.1 mmHg; approximate reference interval 35-45 mmHg) was identified. Cervicothoracic radiographs showed marked gas tracking within cervical soft tissues with concurrent laryngeal thickening, pulmonary nodules, a bronchial pulmonary pattern, pneumomediastinum and aerophagia. The cat was hospitalized and treated overnight with oxygen and intravenous fluid therapy before anesthesia the next day. On laryngoscopy, a large tracheal mass was observed arising from the right subglottic region and was removed using biopsy forceps. CT revealed an additional mass at the level of the tracheal bifurcation causing marked luminal narrowing of the trachea and proximal main bronchi. The cat made a good initial recovery, although moderate stridor persisted. Five days later, the cat was re-examined due to recurrence of respiratory distress and orthopnea, and the owner elected euthanasia. Histopathology revealed severe nodular obstructive eosinophilic plasmacytic laryngotracheitis with intranuclear inclusion bodies positive for feline herpesvirus-1 on immunohistochemistry. Relevance and novel information: This report describes the presentation and management of a cat with respiratory distress secondary to intratracheal eosinophilic masses caused by feline herpesvirus-1. Although the outcome was ultimately unsatisfactory, to the authors' knowledge, this clinical presentation has not been previously reported.

A potential dual protection vaccine: Recombinant feline herpesvirus-1 expressing feline parvovirus VP2 antigen.

Recently, herpesvirus viral vectors that stimulate strong humoral and cellular immunity have been demonstrated to be the most promising platforms for the development of multivalent vaccines, because they contain various nonessential genes and exhibit long-life latency characteristics. Previously, we showed that the feline herpesvirus-1 (FHV-1) mutant WH2020-ΔTK/gI/gE, which was safe for felines and provided efficacious protection against FHV-1 challenge, can be used as a vaccine vector. Moreover, previous studies have shown that the major neutralizing epitope VP2 protein of feline parvovirus (FPV) can elicit high levels of neutralizing antibodies. Therefore, to develop a bivalent vaccine against FPV and FHV-1, we first generated a novel recombinant virus by CRISPR/Cas9-mediated homologous recombination, WH2020-ΔTK/gI/gE-VP2, which expresses the VP2 protein of FPV. The growth characteristics of WH2020-ΔTK/gI/gE-VP2 were similar to those of WH2020-ΔTK/gI/gE, and WH2020-ΔTK/gI/gE-VP2 was stable for at least 30 generations in CRFK cells. As expected, we found that the felines immunized with WH2020-ΔTK/gI/gE-VP2 produced FPV-neutralizing antibody titers (27.5) above the positive cutoff (26) on day 14 after single inoculation. More importantly, recombinant WH2020-ΔTK/gI/gE-VP2 exhibited severely impaired pathogenicity in inoculated and cohabiting cats. The kittens immunized with WH2020-ΔTK/gI/gE and WH2020-ΔTK/gI/gE-VP2 produced similar levels of FHV-specific antibodies and IFN-ß. Furthermore, felines immunized with WH2020-ΔTK/gI/gE-VP2 were protected against challenge with FPV and FHV-1. These data showed that WH2020-ΔTK/gI/gE-VP2 appears to be a potentially safe, effective, and economical bivalent vaccine against FPV and FHV-1 and that WH2020-ΔTK/gI/gE can be used as a viral vector to develop feline multivalent vaccines.

Development and application of a recombinase-aided amplification combined with a lateral flow dipstick assay for rapid visual detection of anguillid herpesvirus 1.

Eel (Anguilla sp.) is an important freshwater-cultured species with high economic value in China. Anguillid herpesvirus 1 (AngHV-1) has been proven to be the pathogen of "mucus sloughing and haemorrhagic septicaemia disease" in eels, resulting in significant mortality and substantial losses to the eel industry. Current diagnostic methods for detecting AngHV-1 are limited to laboratory-based tests, for example, conventional end-point PCR and qPCR. Therefore, there is an urgent need to develop an accurate, rapid, and simple detection method for on-site diagnosis of AngHV-1. In this study, we developed a recombinase-aided amplification combined lateral flow dipstick (RAA-LFD) assay for the detection of AngHV-1. The RAA-LFD assay can be performed within a temperature range of 18-45°C, with a reaction time of just 10 min for amplification. Importantly, the established RAA-LFD assay exhibited no reactivity with other common aquatic viral pathogens, indicating its high specificity. The limit of detection for this method is 102 copies of AngHV-1, which is more sensitive than the established conventional end-point PCR method similarly targeting ORF95. Clinical detection of the diseased samples demonstrated that the accuracy of RAA-LFD was significantly higher than that of the conventional end-point PCR. In conclusion, the developed RAA-LFD assay has proven to be a convenient, rapid, sensitive, and reliable tool for on-site diagnosis of AngHV-1. This advancement will be invaluable for the prevention and control of AngHV-1 in the eel farming industry.

Studying longitudinal neutralising antibody levels against Equid herpesvirus 1 in experimentally infected horses using a novel pseudotype based assay.

Infection with equid herpesvirus 1 (EHV-1), a DNA virus of the Herpesviridae family represents a significant welfare issue in horses and a great impact on the equine industry. During EHV-1 infection, entry of the virus into different cell types is complex due to the presence of twelve glycoproteins (GPs) on the viral envelope. To investigate virus entry mechanisms, specific combinations of GPs were pseudotyped onto lentiviral vectors. Pseudotyped virus (PV) particles bearing gB, gD, gH and gL were able to transduce several target cell lines (HEK293T/17, RK13, CHO-K1, FHK-Tcl3, MDCK I & II), demonstrating that these four EHV-1 glycoproteins are both essential and sufficient for cell entry. The successful generation of an EHV-1 PV permitted development of a PV neutralisation assay (PVNA). The efficacy of the PVNA was tested by measuring the level of neutralising serum antibodies from EHV-1 experimentally infected horses (n = 52) sampled in a longitudinal manner. The same sera were assessed using a conventional EHV-1 virus neutralisation (VN) assay, exhibiting a strong correlation (r = 0.82) between the two assays. Furthermore, PVs routinely require -80 °C for long term storage and a dry ice cold-chain during transport, which can impede dissemination and utilisation in other stakeholder laboratories. Consequently, lyophilisation of EHV-1 PVs was conducted to address this issue. PVs were lyophilised and pellets either reconstituted immediately or stored under various temperature conditions for different time periods. The recovery and functionality of these lyophilised PVs was compared with standard frozen aliquots in titration and neutralisation tests. Results indicated that lyophilisation could be used to stably preserve such complex herpesvirus pseudotypes, even after weeks of storage at room temperature, and that reconstituted EHV-1 PVs could be successfully employed in antibody neutralisation tests.

Comparison of antibody and antigen response to intranasal and intramuscular EHV-1 modified-live vaccination in healthy adult horses.

During neurological EHV-1 outbreaks, modified-live vaccines (MLV) are often administrated intranasally in an off-label fashion to healthy cohort horses in order to achieve rapid mucosal immunity. Thus, the goal of the present study was to determine if a commercially available EHV-1 MLV given intranasally to healthy horses would trigger a measurable systemic and/or mucosal antibody response. Eight healthy adult horses were given the EHV-1 MLV vaccine intranasally, while 8 healthy adult horses received the vaccine intramuscularly. An additional 8 healthy horses served as unvaccinated controls. EHV-1 specific antibodies (total IgG, IgG4/7, IgG1 and IgA) were measured in blood and nasal secretions prior to vaccine administration and 14- and 30-days post-vaccine administration. Further, nasal secretions and whole blood were tested for the presence of EHV-1 DNA by qPCR prior to and 5 days after vaccine administration. EHV-1 was detected by qPCR for the first 48 hours post-intranasal vaccine administration in nasal secretions in a total of three horses. Total EHV-1 IgG and IgG4/7 antibody values in serum increased only in horses receiving the intramuscular MLV. Antibody values at 14- and 30-days post vaccine administration were not different from values prior to vaccine administration in horses receiving the intranasal vaccine. The results support the intramuscular use of the EHV-1 MLV as recommended by the manufacturer. Intranasal vaccination with the study-specific EHV-1 MLV did not induce an increase in systemic or nasal antibodies, therefore, this vaccine route seems suboptimal and should not be used to vaccinate adult horses that have received multiple EHV-1 vaccinations and have pre-existing antibodies against EHV-1.

Viremia and nasal shedding for the diagnosis of equine herpesvirus-1 infection in domesticated horses.

BACKGROUND: Equine herpesvirus type 1 (EHV-1) infection is associated with upper respiratory disease, EHM, abortions, and neonatal death. RESEARCH QUESTIONS: Are nasal secretions a more sensitive biological sample compared to blood for the detection of EHV-1 infection? How long is EHV-1 detectable after primary infection by PCR? METHODS: MedLine and Web of Science searches identified original peer-reviewed reports evaluating nasal shedding and viremia using virus isolation methods or PCR published in English before October 9, 2023. RESULTS: Sixty experimental and 20 observational studies met inclusion criteria. EHV-1 detection frequency by qPCR in nasal secretions and blood from naturally-infected horses with fever and respiratory signs were 15% and 9%, respectively; qPCR detection rates in nasal secretions and blood from horses with suspected EHM were 94% and 70%, respectively. In experimental studies the sensitivity of qPCR matched or exceeded that seen for virus isolation from either nasal secretions or blood. Detection of nasal shedding typically occurred within 2 days after EHV-1 inoculation with a detection period of 3 to 7 days. Viremia lasted 2 to 7 days and was usually detected ≥1 days after positive identification of EHV-1 in nasal secretions. Nasal shedding and viremia decreased over time and remained detectable in some horses for several weeks after inoculation. CONCLUSIONS AND CLINICAL IMPORTANCE: Under experimental conditions, blood and nasal secretions have similar sensitivity for the detection of EHV-1 when horses are sampled on multiple consecutive days. In contrast, in observational studies detection of EHV-1 in nasal secretions was consistently more successful.

Relationship between equine herpesvirus-1 viremia and abortion or equine herpesvirus myeloencephalopathy in domesticated horses: A systematic review.

BACKGROUND: Equine herpes virus type 1 (EHV-1) infection in horses is associated with upper respiratory disease, neurological disease, abortions, and neonatal death. OBJECTIVE: To determine if there is an association between the level and duration of EHV-1 viremia and either abortion or equine herpesvirus myeloencephalopathy (EHM) in domesticated horses? METHODS: A systematic review was performed searching numerous databases to identify peer reviewed reports that evaluated viremia and EHM, or viremia and abortion published before January 19, 2021. Randomized controlled trials and observational studies were assessed for risk of bias or publication quality. RESULTS: A total of 189 unique studies were identified, of which 34 met the inclusion criteria. Thirty studies evaluated viremia and neurologic outcomes including 4 observational studies. Eight experimental studies examined viremia and abortion, which used the Ab4 and OH03 virus strains or recombinant Ab4 derivatives. Incidence rates for both EHM and abortion in experimental studies varied among the studies as did the level of evidence. Viremia was generally detectable before the onset of either EHM or abortion. Risk of bias was generally low to moderate, sample sizes were small, and multiple studies reported negative outcome data. CONCLUSIONS AND CLINICAL IMPORTANCE: The results of this study support that viremia is regularly present before EHM or abortion occurs. However, no inferences could be made about the relationship between the occurrence of either neurological signs or abortion and the magnitude or duration of viremia.