Feline Herpesvirus 1 Infection Research Articles

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.

Clinical evaluation of antiviral combination treatment in cats with feline herpesvirus-1 infection

Clinical evaluation of antiviral combination treatment in cats with feline herpesvirus-1 infection

A bacterium-like particle vaccine displaying protective feline herpesvirus 1 antigens can induce an immune response in mice and cats

Feline herpesvirus 1 (FHV-1) is a highly transmissible virus that mainly causes ocular and upper respiratory infections in cats and seriously threatens the health of domestic cats and captive or wild cats (such as tigers, cheetahs, and lions). Vaccination is crucial to reduce the incidence rate and mortality of cats infected with FHV-1. In this study, three bacterium-like particles (BLPs) displaying the gB, gC, and gD proteins of FHV-1 were constructed based on a gram-positive enhancer matrix-protein anchor (GEM-PA) surface display system. Indirect immunofluorescence assay, western blot, and electron microscopy results showed that gB, gC or gD protein of FHV-1 was successfully displayed on the surface of GEM particles. Additionally, we designed one more BLPs, designated gB&gC&gD-GEM, which consisted of a mixture of gB-GEM, gC-GEM, and gD-GEM at a protein content ratio of 1:1:1. Mice were immunized with the four BLPs mixed with Gel02 adjuvant, and the results indicated that neutralizing antibody level in the gB&gC&gD-GEM group was superior than those in the other groups. Moreover, gB&gC&gD-GEM significantly increased the secretion of cytokines, as well as the activation and maturation of B cells. It also boosted the production of central memory T cells among CD4 + and CD8 + T cells. Moreover, gB&gC&gD-GEM mixed with Gel02 adjuvant provoked an antibody response in cats. In conclusion, the BLPs vaccine prepared from gB&gC&gD-GEM induced specific humoral and cellular immune responses to FHV-1 and be used as a potential vaccine candidate for the control of FHV-1 infection in cats.

Relationship between the bacterial ocular surface microbiota and outcomes for cats with feline herpesvirus type 1 ocular surface disease.

Feline herpesvirus 1 (FHV-1) causes ocular surface disease in domestic cats. The purpose of this study was to assess the relationship between bacterial ocular surface microbiota and outcomes for cats with FHV-1 ocular surface disease. Twenty-two shelter-housed cats with confirmed FHV-1 ocular surface disease. Animals were grouped according to FHV-1 shedding and ocular clinical scores following intervention: worsened outcome (WorOut, n = 11) or improved outcome (ImpOut, n = 11). Scoring and conjunctival sampling were completed on Days 1 and 8 of twice daily antiviral treatment. Bacterial DNA was extracted and submitted for 16S rRNA gene sequencing. Real-time polymerase chain reaction was performed for selected bacterial species. Overall DNA concentration between groups was assessed. Bacterial microbiota relative abundance composition was significantly different between ImpOut and WorOut groups (weighted UniFrac p = .006). Alpha diversity was significantly higher in the ImpOut group compared with the WorOut group (Shannon p = .042, Simpson's p = .022, Pielou's p = .037). Differences in the relative abundance of various phyla and species were detected between groups. Total DNA concentration was higher in the WorOut group compared with the ImpOut group (p = .04). Feline GAPDH (p = .001) and Bilophila wadsworthia (p = .024) copy number was significantly higher in the ImpOut group compared with the WorOut group. The results highlight the important relationship between the bacterial ocular surface microbiota and FHV-1 infection outcomes in cats treated with antiviral medications. Low bacterial species diversity, higher overall DNA (presumed predominantly bacterial) load, and certain bacterial phyla/species were associated with poor outcomes for cats with FHV-1 ocular disease.

Development of immortalized feline respiratory epithelial cells in an air-liquid-interface culture system for feline herpesvirus-1 study

Feline herpesvirus-1 (FHV-1) is responsible for approximately 50% of diagnosed viral upper respiratory tract disease in cats. The virus infects and replicates in the epithelial cells located in upper respiratory tract. Commercial vaccines do not protect cats from the infection itself or development of latency. Previously, our lab developed a cell culture model using primary feline respiratory epithelial cells (pFRECs) to study respiratory innate immunity to FHV-1 and FHV-1 deletion mutants. However, the numbers of pFRECs that can be obtained per cat is limited. To improve the usage of respiratory epithelial 3D cultures in FHV-1 research, the present study immortalized feline respiratory epithelial cells (iFRECs) and characterized them morphologically and immunologically and evaluated the response to FHV-1 infection. Immortalization was achieved by transduction with Lenti-SV40T and Lenti-HPV E6/E7. Immortalized FRECs could be successfully subcultured for >20 passages, with positive gene expression of SV40T and HPV E6/E7. Immortalized FRECs expressed similar innate immunity-associated genes compared to pFRECs, including genes of Toll-like receptors (TLR1–9), interferon induced genes (OAS1, OAS3, IFI44, IFITM1, IFIT1), chemokines (CCL2, CCL3, CXCL8), pro-inflammatory and regulatory cytokines (IL-6, IL-4, IL-5, IL-12, and IL-18), and antimicrobials (DEFβ10, DEFβ4B). Finally, FHV-1 inoculation resulted in characteristic cytopathic effects starting at 24 hpi, with more than 80% cells detached and lysed by 72 hpi. Overall FHV-1 growth kinetics in iFRECs resembled the kinetics observed in pFRECs. In conclusion, we demonstrated that iFRECs are a useful tool to study feline respiratory disease including but not limited to FHV-1.

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.

Comparative Efficacy of Topical Ophthalmic Ganciclovir and Oral Famciclovir in Cats with Experimental Ocular Feline Herpesvirus-1 Epithelial Infection.

Purpose: To determine the comparative efficacy of ganciclovir ophthalmic gel and famciclovir oral tablets in cats with experimentally induced ocular feline herpesvirus-1 (FHV-1) epithelial infection. Methods: A randomized, placebo-controlled trial was performed using 16 nonvaccinated, specific pathogen-free cats with experimental FHV-1 infection induced by topical ocular inoculation. Cats received topical ganciclovir 0.15% ophthalmic gel (1 drop 3 times daily, n = 6 cats), oral famciclovir (90 mg/kg twice daily, n = 6), or topical artificial tear gel (1 drop 3 times daily, n = 4) for 14 days. Cats were monitored after inoculation for 30 days. Ophthalmic examinations were performed every 2 days and ocular disease scores calculated. In vivo confocal microscopy was performed, and corneal leukocyte infiltrates quantified. Ocular samples for FHV-1 quantitative polymerase chain reaction (qPCR) and virus isolation assays were collected every 3 days. Hemograms and serum biochemistry panels were performed at intervals. Results: Clinical ocular disease scores and corneal leukocyte infiltrates were significantly lower in the ganciclovir and famciclovir groups compared with placebo, but no significant differences were detected between the antiviral treatment groups. Ocular viral loads determined by qPCR were significantly lower in the ganciclovir group compared with the placebo group, but there were no significant differences between the other study groups. Hemograms and biochemistry panels were unremarkable. Conclusion: Topical application of ganciclovir gel 3 times daily was well-tolerated and displayed similar efficacy at reducing clinical ocular disease scores and corneal inflammation as twice daily oral famciclovir treatment in cats with experimental ocular FHV-1 infection.

MiR-101 inhibits feline herpesvirus 1 replication by targeting cellular suppressor of cytokine signaling 5 (SOCS5)

Feline viral rhinotracheitis is a prevalent disease among cats caused by feline herpesvirus 1 (FHV-1). microRNAs (miRNAs), which serve as important regulatory factors in the host, participate in the regulation of the host innate immune response to virus infection. However, the roles of miRNAs in the FHV-1 life cycle remain unclear. In this study, we found that a new miRNA, miR-101, could suppress FHV-1 replication. FHV-1 infection upregulated the expression level of miR-101 in a cGAS-dependent manner. Furthermore, miR-101 could significantly enhance type I interferon antiviral signaling by targeting suppressor of cytokine signaling 5 (SOCS5), a negative regulator of the JAK-STAT pathway. Likewise, knockdown of cellular SOCS5 also suppressed FHV-1 replication due to the enhancement of IFN-I-induced signaling cascades. Taken together, our data demonstrated a new strategy for miR-101-mediated defense against FHV-1 infection by enhancing IFN-I antiviral signaling and increased the knowledge of miRNAs regulating innate immune signaling pathways.

MiR-26a Inhibits Feline Herpesvirus 1 Replication by Targeting SOCS5 and Promoting Type I Interferon Signaling.

In response to viral infection, host cells activate various antiviral responses to inhibit virus replication. While feline herpesvirus 1 (FHV-1) manipulates the host early innate immune response in many different ways, the host could activate the antiviral response to counteract it through some unknown mechanisms. MicroRNAs (miRNAs) which serve as a class of regulatory factors in the host, participate in the regulation of the host innate immune response against virus infection. In this study, we found that the expression levels of miR-26a were significantly upregulated upon FHV-1 infection. Furthermore, FHV-1 infection induced the expression of miR-26a via a cGAS-dependent pathway, and knockdown of cellular cGAS significantly blocked the expression of miR-26a induced by poly (dA:dT) or FHV-1 infection. Next, we investigated the biological function of miR-26a during viral infection. miR-26a was able to increase the phosphorylation of STAT1 and promote type I IFN signaling, thus inhibiting viral replication. The mechanism study showed that miR-26a directly targeted host SOCS5. Knockdown of SOCS5 increased the phosphorylation of STAT1 and enhanced the type I IFN-mediated antiviral response, and overexpression of suppressor of the cytokine signalling 5 (SOCS5) decreased the phosphorylation of STAT1 and inhibited the type I IFN-mediated antiviral response. Meanwhile, with the knockdown of SOCS5, the upregulated expression of phosphorylated STAT1 and the anti-virus effect induced by miR-26a were significantly inhibited. Taken together, our data demonstrated a new strategy of host miRNAs against FHV-1 infection by enhancing IFN antiviral signaling.

Treatment of acute viral feline upper respiratory tract infections

The main causative agents of feline upper respiratory tract disease (FURTD) are feline herpesvirus-1 (FHV-1) and feline calicivirus (FCV). These viral infections are common, especially in multiple cat households. Severely affected cats often need to be hospitalized. Intensive symptomatic therapy is important in the management of cats with FURTD. The use of antiviral drugs is limited in cats, as they are often ineffective or toxic when given systemically. Antiviral drugs are, therefore, mainly used locally for the treatment of FHV-1-associated eye changes. Famciclovir, however, is an effective drug for systemic therapy in cats with FHV-1-related clinical signs. For FCV, only few antiviral drugs are available. In a controlled study, the use of immunoglobulins in cats with FHV-1 and/or FCV infection reduced clinical signs of FURTD significantly faster.

Recombinase Polymerase Amplification Assay—A Simple, Fast and Cost-Effective Alternative to Real Time PCR for Specific Detection of Feline Herpesvirus-1

Feline herpesvirus 1 (FHV-1), an enveloped dsDNA virus, is one of the major pathogens of feline upper respiratory tract disease (URTD) and ocular disease. Currently, polymerase chain reaction (PCR) remains the gold standard diagnostic tool for FHV-1 infection but is relatively expensive, requires well-equipped laboratories and is not suitable for field tests. Recombinase polymerase amplification (RPA), an isothermal gene amplification technology, has been explored for the molecular diagnosis of infectious diseases. In this study, an exo-RPA assay for FHV-1 detection was developed and validated. Primers targeting specifically the thymidine kinase (TK) gene of FHV-1 were designed. The RPA reaction was performed successfully at 39°C and the results were obtained within 20 min. Using different copy numbers of recombinant plasmid DNA that contains the TK gene as template, we showed the detection limit of exo-RPA was 102 copies DNA/reaction, the same as that of real time PCR. The exo-RPA assay did not cross-detect feline panleukopenia virus, feline calicivirus, bovine herpesvirus-1, pseudorabies virus or chlamydia psittaci, a panel of pathogens important in feline URTD or other viruses in Alphaherpesvirinae, demonstrating high specificity. The assay was validated by testing 120 nasal and ocular conjunctival swabs of cats, and the results were compared with those obtained with real-time PCR. Both assays provided the same testing results in the clinical samples. Compared with real time PCR, the exo-RPA assay uses less-complex equipment that is portable and the reaction is completed much faster. Additionally, commercial RPA reagents in vacuum-sealed pouches can tolerate temperatures up to room temperature for days without loss of activity, suitable for shipment and storage for field tests. Taken together, the exo-RPA assay is a simple, fast and cost-effective alternative to real time PCR, suitable for use in less advanced laboratories and for field detection of FHV-1 infection.

Use of a feline respiratory epithelial cell culture system grown at the air–liquid interface to characterize the innate immune response following feline herpesvirus 1 infection

Infection with feline herpesvirus-1 (FHV-1) accounts for 50% of viral upper respiratory diseases in domestic cats and is a significant cause of ocular diseases. Despite the clinical significance and high prevalence of FHV-1 infection, currently available vaccines cannot completely protect cats from infection and lifelong latency. FHV-1 infects via the mucous membranes and replicates in respiratory epithelial cells, but very little is known about the early innate immunity at this site. To address questions about immunity to FHV-1, feline respiratory epithelial cells cultured at air–liquid interface (ALI-FRECs) were established by collecting respiratory tracts from 6 healthy cats after euthanasia. Cells were isolated, cultured and characterized histologically and immunologically before infection with FHV-1. The expression of Toll-like receptors (TLRs), cytokine and chemokine responses were measured by real time PCR.ALI-FRECs morphologically resembled the natural airways of cats with multilayered columnar epithelial cells and cilia. Immunological properties of the natural airways were maintained in ALI-FRECs, as evidenced by the expression of TLRs, cytokines, chemokines, interferons, beta-defensins, and other regulatory genes. Furthermore, ALI-FRECs were able to support infection and replication of FHV-1, as well as modulate transcriptional regulation of various immune genes in response to infection. IL-1β and TNFα were increased in ALI-FRECs by 24hpi, whereas expression levels of IFN-α and TLR9 were not increased until 36hpi. In contrast, TLR3, GM-CSF and TGF-1β expression was down-regulated at 36hpi.The data presented show the development of a system ideal for investigating the molecular pathogenesis and immunity of FHV-1 or other respiratory pathogens.

The processivity factor complex of feline herpes virus-1 is a new drug target

Feline herpes virus-1 (FHV-1) is ubiquitous in the cat population and is a major cause of blindness for which antiviral drugs, including acyclovir, are not completely effective. Recurrent infections, due to reactivation of latent FHV-1 residing in the trigeminal ganglia, can lead to epithelial keratitis and stromal keratitis and eventually loss of sight. This has prompted the medical need for an antiviral drug that will specifically inhibit FHV-1 infection. A new antiviral target is the DNA polymerase and its associated processivity factor, which forms a complex that is essential for extended DNA strand synthesis. In this study we have cloned and expressed the FHV-1 DNA polymerase (f-UL30) and processivity factor (f-UL42) and demonstrated that both proteins are required to completely synthesize the 7249 nucleotide full-length DNA from the M13 primed-DNA template in vitro. Significantly, a known inhibitor of human herpes simplex virus-1 (HSV-1) processivity complex was shown to inhibit FHV-1 processive DNA synthesis in vitro and block infection of cells. This validates using f-UL42/f-UL30 as a new antiviral drug target to treat feline ocular herpes infection.

Üç kedide Feline Herpes Virus - 1 ( FHV - 1 ) ilişkili okuler lezyonlar ın Famciclovir ile sağaltımı

Feline herpesvirus-1 (FHV-1) associated ocular lesions and it’s treatment was presented in two adult cats and one kitten. Adult cats were showing corneal edema, conjunctivitis and corneal sequestrum while ocular discharge, conjunctivitis and keratitis was predominant in the kitten. Conjunctival swabs obtained from the cats were evaluated with PCR and found positive against FHV-1. Effectiveness of systemic anti-herpes drug, Famciclovir combination with L-lysine in the clinical management of FHV-1 were investigated. Famciclovir was found to be an effective drug in combination with the L-lysine in the treatment of FHV-1 infection. The treatment was well tolerated and the clinical signs were resolved in all cats

Efficacy of passively transferred antibodies in cats with acute viral upper respiratory tract infection

A commercial hyperimmune serum, containing antibodies against feline calicivirus (FCV), feline herpesvirus 1 (FHV-1), and feline panleukopenia virus, is available for treatment of cats with feline upper respiratory tract disease (FURTD), but its efficacy has not been rigorously evaluated in scientific studies. The aim of this randomised, placebo-controlled, double-blind clinical trial was to evaluate the efficacy of passive immunisation in cats with acute viral FURTD caused by FCV and/or FHV-1 infection. All cats received symptomatic treatment during the study period. Hyperimmune serum was administered to one group (n = 22) and an equivalent amount of saline was administered to the control group (n = 20) as placebo, for 3 consecutive days. In the treatment group, cats ≤12 weeks old received 2 mL, cats >12 weeks old received 4 mL, subcutaneously once daily and topically into eyes, nostrils, and mouth every 8 h. Clinical signs, including a ‘FURTD score’ and general health status, were recorded daily for 8 days and again on day 21. FCV shedding was determined by quantitative PCR on days 0 and 21.Clinical signs and health status in both groups improved significantly over time (P < 0.001). Cats receiving hyperimmune serum significantly improved in terms of ‘FURTD score’ (P = 0.046) and general health status (P = 0.032) by day 3, while cats in the placebo group only improved significantly by day 7. There was no significant difference in the number of cats shedding FCV between the two groups. Thus, administration of hyperimmune serum led to a more rapid improvement of clinical signs in cats with acute viral FURTD, but by day 7, clinical signs had improved equally in both groups.

Controlled release delivery of penciclovir via a silicone (MED-4750) polymer: kinetics of drug delivery and efficacy in preventing primary feline herpesvirus infection in culture

BackgroundHerpesviruses are ubiquitous pathogens that infect and cause recurrent disease in multiple animal species. Feline herpesvirus-1 (FHV-1), a member of the alphaherpesvirus family, causes respiratory illness and conjunctivitis, and approximately 80% of domestic cats are latently infected. Oral administration of famciclovir or topical application of cidofovir has been shown in masked, placebo-controlled prospective trials to reduce clinical signs and viral shedding in experimentally inoculated cats. However, to the authors’ knowledge, other drugs have not been similarly assessed or were not safe or effective. Likewise, to our knowledge, no drugs have been assessed in a placebo-controlled manner in cats with recrudescent herpetic disease. Controlled-release devices would permit long-term administration of these drugs and enhance compliance.MethodsWe therefore engineered implantable cylindrical devices made from silicone (MED-4750) impregnated with penciclovir, for long-term, steady-state delivery of this drug.ResultsOur data show that these devices release penciclovir with a burst of drug delivery until the tenth day of release, then at an average rate of 5.063 ± 1.704 μg per day through the next 50 days with near zero-order kinetics (in comparison to MED-4750-acyclovir devices, which show the same burst kinetics and average 2.236 ± 0.625 μg/day thereafter). Furthermore, these devices suppress primary infection of FHV-1 in a cell culture system.ConclusionsThe clinical deployment of these silicone-penciclovir devices may allow long-term treatment of FHV-1 infection with a single intervention that could last the life of the host cat.

Felid Herpesvirus Type 1 Infection in Cats: A Natural Host Model for Alphaherpesvirus Pathogenesis

Feline herpesvirus 1 (FeHV-1) is an alphaherpesvirus that causes feline viral rhinotracheitis, an important viral disease of cats on a worldwide basis. Acute FeHV-1 infection is associated with both upper respiratory and ocular signs. Following the acute phase of the disease lifelong latency is established, primarily in sensory neuronal cells. As is the case with human herpes simplex viruses, latency reactivation can result in recrudescence, which can manifest itself in the form of serious ocular lesions. FeHV-1 infection in cats is a natural host model that is useful for the identification of viral virulence genes that play a role in replication at the mucosal portals of entry or are mediators of the establishment, maintenance, or reactivation of latency. It is also a model system for defining innate and adaptive immunity mechanisms and for immunization strategies that can lead to better protection against this and other alphaherpesvirus infections.

Feline herpesvirus 1 infections in a domestic cat population in Ahvaz, Iran.

Summary Feline herpesvirus 1 (FeHV-1) and feline calicivirus (FCV), associated with upper respiratory tract disease, are highly prevalent in cats worldwide. With the aim of investigating the importance of FeHV-1 in a population of cats, samples were taken in a hospital in Ahvaz, south-west Iran, between June 2007 and June 2008. Oropharyngeal, nasal and ocular swabs were collected from 65 domestic cats, including 52 stray and 13 household animals and were tested for the presence of FeHV-1 DNA by polymerase chain reaction (PCR). The overall prevalence rate of FeHV-1 was 35.38%. There was a statistically significant association between the prevalence rate of FeHV-1 and the presence of respiratory signs. High prevalence of FeHV-1 infection strengthens the importance of applying hygienic and preventive measures in cats in the study area.

Detection of feline herpes virus 1 via polymerase chain reaction and immunohistochemistry in cats with ulcerative facial dermatitis, eosinophilic granuloma complex reaction patterns and mosquito bite hypersensitivity

Ulcerative dermatitis caused by feline herpes virus 1 (FHV-1) is an uncommon disease characterized by cutaneous ulcers secondary to epidermal, adnexal and dermal necrosis. Differential diagnoses for FHV-1 lesions include, but are not limited to, mosquito bite hypersensitivity and eosinophilic granuloma complex. Histopathological diagnosis of FHV-1 dermatitis is based on the detection of the intranuclear inclusion bodies. In cases where intranuclear inclusions are missing but clinical and histological findings are compatible with FHV-1 dermatitis, immunohistochemistry (IHC) and PCRs have been used. In this retrospective study, we evaluated the presence of FHV-1 by IHC and PCR in skin biopsies and compared the results of the two tests. Sixty-four skin biopsy specimens from cats with compatible lesions were reviewed and tested via PCR and IHC for evidence of FHV-1. Polymerase chain reaction was positive in 12 of 64 biopsies; PCR and IHC were positive only in two of 64 biopsies, and these cases were considered true positive cases. The higher number of PCR-positive cases was possibly attributed to amplification of viral DNA from a live attenuated vaccination, but a previous FHV-1 infection with subsequent amplification of latently inserted FHV-1 could not be excluded. If clinical signs and histopathology suggest FHV-1 infection in the absence of typical inclusion bodies, IHC is the preferred diagnostic test; PCR may be useful for initial screening, but due to false positives is not sufficient for a definitive diagnosis.

Evaluation of the effects of small interfering RNAs on in vitro replication of feline herpesvirus-1

To evaluate the ability of 5 small interfering RNAs (siRNAs) targeting mRNA of the feline herpesvirus-1 (FHV-1) DNA polymerase gene to reduce in vitro viral replication and gene expression of FHV-1, to evaluate combinations of these siRNAs with siRNAs that target the glycoprotein D gene of FHV-1, and to determine the combination or combinations of siRNAs that yield the greatest inhibition of in vitro viral replication. Cultured Crandell-Rees feline kidney (CRFK) cells. CRFK cells were transfected with siRNAs designed to target mRNA of the FHV-1 DNA polymerase gene. Effective treatment was determined by quantification of the inhibition of mRNA available for DNA polymerase translation, viral protein production, and viral replication. Combinations of 2 siRNAs that target mRNA of the FHV-1 DNA polymerase gene and 2 siRNAs that target the mRNA of the essential FHV-1 glycoprotein D gene were evaluated for the ability to inhibit viral replication. Verified by a reduction in viral gene expression, 2 of the 5 siRNAs designed to target mRNA of the FHV-1 DNA polymerase gene significantly suppressed viral replication. Two combinations of siRNAs that target mRNA of the FHV-1 DNA polymerase gene, the FHV-1 glycoprotein D gene, or both also significantly suppressed viral replication. Combinations of siRNAs that target mRNA of the FHV-1 DNA polymerase gene, FHV-1 glycoprotein D gene, or both could potentially be used as a treatment for the prevention of clinical disease associated with FHV-1 infection.