Genomic analysis for virulence determinants in feline herpesvirus type-1 isolates

Identification, Genetic Characterization, and Pathogenicity of Three Feline Herpesvirus Type 1 Isolates from Domestic Cats in China

(1) Background: Feline herpesvirus (FHV-1) is a significant pathogen in cats, causing respiratory and ocular diseases with consequential economic and welfare implications. (2) Methods: This study aimed to isolate and characterize FHV-1 from clinical samples and assess its pathogenicity. We collected 35 nasal and ocular swabs from cats showing symptoms of upper respiratory tract infection and FHV positivity detected by polymerase chain reaction (PCR). Viral isolation was carried out using feline kidney (F81) cell lines. Confirmation of FHV-1 presence was achieved through PCR detection, sequencing, electron microscopy, and indirect immunofluorescence assay. The isolated strains were further characterized by evaluating their titers, growth kinetics, and genetic characteristics. Additionally, we assessed the pathogenicity of the isolated strains in a feline model, monitoring clinical signs, viral shedding, and histopathological changes. (3) Results: Three strains of FHV-1 were isolated, purified, and identified. The isolated FHV-1 strains exhibited high homology among themselves and with domestic isolates and FHV-1 viruses from around the world. However, they showed varying degrees of virulence, with one strain (FHV-A1) causing severe clinical signs and histopathological lesions. (4) Conclusion: This study advances our understanding of the genetic and pathogenic characteristics of FHV-1 in China. These findings underscore FHV-A1 isolate as a potentially ideal candidate for establishing a challenge model and as a potential vaccine strain for vaccine development.

Phosphoproteomic landscape of pseudorabies virus infection reveals multiple potential antiviral targets

IMPORTANCE

Pseudorabies virus (PRV) is a kind of alpha herpesvirus that infects a wide range of animals and even human beings. Therefore, it is important to explore the mechanisms behind PRV replication and pathogenesis. By conducting a tandem mass tag-based phosphoproteome, this study revealed the phosphorylated proteins and cellular response pathways involved in PRV infection. Findings from this study shed light on the relationship between the phosphorylated cellular proteins and PRV infection, as well as guiding the discovery of targets for the development of antiviral compounds against PRV.

Surveillance for feline herpesvirus type 1 mutation and development of resistance in cats treated with antiviral medications

Feline herpesvirus type 1 (FHV-1) commonly causes ocular surface disease in cats and is treated with antiviral medications targeting viral DNA polymerase (UL30/42). Herein, we describe a method to assess the FHV-1 genome for mutation development and to assess the functional impact of mutations, if present. Fourteen shelter-housed domestic cats with FHV-1 ocular surface disease were assigned to one of four treatment groups: placebo (n = 3), cidofovir 0.5% ophthalmic solution (n = 3), famciclovir oral solution (n = 5), or ganciclovir 0.15% ophthalmic solution (n = 3). Swabs were collected before (day 1) and after (day 8) 1 week of twice-daily treatments to isolate viable FHV-1. Viral DNA was extracted for sequencing using Illumina MiSeq with subsequent genomic variant detection between paired day 1 and day 8 isolates. Plaque reduction assay was performed on paired isolates demonstrating non-synonymous variants. A total of 171 synonymous and 3 non-synonymous variants were identified in day 8 isolates. No variants were detected in viral UL23, UL30, or UL42 genes. Variant totals were not statistically different in animals receiving antiviral or placebo (p = 0.4997). A day 8 isolate from each antiviral treatment group contained a single non-synonymous variant in ICP4 (transcriptional regulator). These 3 isolates demonstrated no evidence of functional antiviral resistance when IC₅₀ was assessed. Most (10/14 pairs) day 1 and 8 viral isolate pairs from the same host animal were near-identical. While functional variants were not detected in this small sample, these techniques can be replicated to assess FHV-1 isolates suspected of having developed resistance to antiviral medications.

A review of evidence-based management of infectious ocular surface disease in shelter-housed domestic cats

Infectious ocular surface disease (IOSD) is a common problem in shelter-housed domestic cats and has a widespread negative impact on animal welfare. While the common etiological agents are well-described, addressing IOSD in large groups of animals presents a management challenge to the clinician and logistical challenges to shelter employees. Treatments, diagnostics, and prevention strategies that are effective in privately owned or experimental animals may be impractical or ineffective in the shelter environment. This review article focuses on the relative prevalence of etiological agents in feline IOSD, practical diagnostic testing protocols, prevention strategies, and treatment of IOSD in shelter-housed cats. Discrepancies between experimental laboratory-based studies and clinical trials assessing therapeutics for treatment of feline herpes virus are highlighted. Further high-quality clinical trials are necessary to determine optimal preventative and therapeutic protocols for IOSD in shelter-housed cats.

Nanoparticle ocular immunotherapy for herpesvirus surface eye infections evaluated in cat infection model

Ocular herpes simplex type 1 (HSV-1) infections can trigger conjunctivitis, keratitis, uveitis, and occasionally retinitis, and is a major cause of blindness worldwide. The infections are lifelong and can often recrudesce during periods of stress or immune suppression. Currently HSV-1 infections of the eye are managed primarily with anti-viral eye drops, which require frequent administration, can cause irritation, and may take weeks for full resolution of symptoms. We therefore evaluated the effectiveness of an ocular immune activating nanoparticle eye drop as a novel approach to treating HSV-1 infection, using a cat feline herpesvirus -1 (FHV-1) ocular infection model. In vitro studies demonstrated significant induction of both type I and II interferon responses by the liposome-dual TLR 3/9 agonist nanoparticles, along with suppression of FHV-1 replication. In cats with naturally occurring eye infections either proven or suspected to involve FHV-1, ocular nanoparticle treated animals experienced resolution of signs within several days of treatment, including resolution of keratitis and corneal ulcers. In a cat model of recrudescent FHV-1 infection, cats treated twice daily with immune nanoparticle eye drops experienced significant lessening of ocular signs of infection and significantly fewer episodes of viral shedding compared to control cats. Treatment was well-tolerated by all cats, without signs of drug-induced ocular irritation. We concluded therefore that non-specific ocular immunotherapy offers significant promise as a novel approach to treatment of HSV-1 and FHV-1 ocular infections.

Feline Coronavirus and Alpha-Herpesvirus Infections: Innate Immune Response and Immune Escape Mechanisms

Over time, feline viruses have acquired elaborateopportunistic properties, making their infections particularly difficult to prevent and treat. Feline coronavirus (FCoV) and feline herpesvirus-1 (FeHV-1), due to the involvement of host genetic factors and immune mechanisms in the development of the disease and more severe forms, are important examples of immune evasion of the host's innate immune response by feline viruses.It is widely accepted that the innate immune system, which providesan initial universal form of the mammalian host protection from infectious diseases without pre-exposure, plays an essential role in determining the outcome of viral infection.The main components of this immune systembranchare represented by the internal sensors of the host cells that are able to perceive the presence of viral component, including nucleic acids, to start and trigger the production of first type interferon and to activate the cytotoxicity by Natural Killercells, often exploited by viruses for immune evasion.In this brief review, we providea general overview of the principal tools of innate immunity, focusing on the immunologic escape implemented byFCoVand FeHV-1 duringinfection.

Current ocular microbiome investigations limit reproducibility and reliability: Critical review and opportunities

Enthusiasm for research describing microbial communities using next-generation sequencing (NGS) has outpaced efforts to standardize methodology. Without consistency in the way research is carried out in this field, the comparison of data between studies is near impossible and the utility of results remains limited. This holds true for bacterial microbiome research of the ocular surface, and other sites, in both humans and animals. In addition, the ocular surface remains under-explored when compared to other mucosal sites. Low bacterial biomass samples from the ocular surface lead to further technical challenges. Taken together, two major problems were identified: (1) Normalization of the workflow in studies utilizing NGS to investigate the ocular surface bacteriome is necessary in order to propel the field forward and improve research impact through cross-study comparisons. (2) Current microbiome profiling technology was developed for high bacterial biomass samples (such as feces or soil), posing a challenge for analyses of samples with low bacterial load such as the ocular surface. This article reviews the challenges and limitations currently facing ocular microbiome research and provides recommendations for minimum reporting standards for veterinary ophthalmologists and clinician scientists to limit inter-study variation, improve reproducibility, and ultimately render results from these studies more impactful. The move toward normalization of methodology will expedite and maximize the potential for microbiome research to translate into meaningful discovery and tangible clinical applications.