Novel mutation N588 residue in the NS1 protein of feline parvovirus greatly augments viral replication.

Feline parvovirus (FPV) infection is highly fatal in felines. NS1, which is a key nonstructural protein of FPV, can inhibit host innate immunity and promote viral replication, which is the main reason for the severe pathogenicity of FPV. However, the mechanism by which the NS1 protein disrupts host immunity and regulates viral replication is still unclear. Here, we identified an FPV M1 strain that is regulated by the NS1 protein and has more pronounced suppression of innate immunity, resulting in robust replication. We found that the neutralization titer of the FPV M1 strain was significantly lower than that of the other strains. Moreover, FPV M1 had powerful replication ability, and the FPV M1-NS1 protein had heightened efficacy in repressing interferon-stimulated genes (ISGs) expression. Subsequently, we constructed an FPV reverse genetic system, which confirmed that the N588 residue of FPV M1-NS1 protein is a key amino acid that bolsters viral proliferation. Recombinant virus containing N588 also had stronger ability to inhibit ISGs, and lower ISGs levels promoted viral replication and reduced the neutralization titer of the positive control serum. Finally, we confirmed that the difference in viral replication was abolished in type I IFN receptor knockout cell lines. In conclusion, our results demonstrate that the N588 residue of the NS1 protein is a critical amino acid that promotes viral proliferation by increasing the inhibition of ISGs expression. These insights provide a reference for studying the relationship between parvovirus-mediated inhibition of host innate immunity and viral replication while facilitating improved FPV vaccine production.IMPORTANCEFPV infection is a viral infectious disease with the highest mortality rate in felines. A universal feature of parvovirus is its ability to inhibit host innate immunity, and its ability to suppress innate immunity is mainly accomplished by the NS1 protein. In the present study, FPV was used as a viral model to explore the mechanism by which the NS1 protein inhibits innate immunity and regulates viral replication. Studies have shown that the FPV-NS1 protein containing the N588 residue strongly inhibits the expression of host ISGs, thereby increasing the viral proliferation titer. In addition, the presence of the N588 residue can increase the proliferation titer of the strain 5- to 10-fold without affecting its virulence and immunogenicity. In conclusion, our findings provide new insights and guidance for studying the mechanisms by which parvoviruses suppress innate immunity and for developing high-yielding FPV vaccines.

Prevalence of autoantibodies that bind to kidney tissues in cats and association risk with antibodies to feline viral rhinotracheitis, calicivirus, and panleukopenia.

BACKGROUND: The feline viral rhinotracheitis, calicivirus, and panleukopenia (FVRCP) vaccine, prepared from viruses grown in the Crandell-Rees feline kidney cell line, can induce antibodies to cross-react with feline kidney tissues. OBJECTIVES: This study surveyed the prevalence of autoantibodies to feline kidney tissues and their association with the frequency of FVRCP vaccination. METHODS: Serum samples and kidneys were collected from 156 live and 26 cadaveric cats. Antibodies that bind to kidney tissues and antibodies to the FVRCP antigen were determined by enzyme-linked immunosorbent assay (ELISA), and kidney-bound antibody patterns were investigated by examining immunofluorescence. Proteins recognized by antibodies were identified by Western blot analysis. RESULTS: The prevalences of autoantibodies that bind to kidney tissues in cats were 41% and 13% by ELISA and immunofluorescence, respectively. Kidney-bound antibodies were observed at interstitial cells, apical border, and cytoplasm of proximal and distal tubules; the antibodies were bound to proteins with molecular weights of 40, 47, 38, and 20 kDa. There was no direct link between vaccination and anti-kidney antibodies, but positive antibodies to kidney tissues were significantly associated with the anti-FVRCP antibody. The odds ratio or association in finding the autoantibody in cats with the antibody to FVRCP was 2.8 times higher than that in cats without the antibody to FVRCP. CONCLUSIONS: These preliminary results demonstrate an association between anti-FVRCP and anti-cat kidney tissues. However, an increase in the risk of inducing kidney-bound antibodies by repeat vaccinations could not be shown directly. It will be interesting to expand the sample size and follow-up on whether these autoantibodies can lead to kidney function impairment.

A pre- and during Pandemic Survey of Sars-Cov-2 Infection in Stray Colony and Shelter Cats from a High Endemic Area of Northern Italy.

Cats are susceptible to infection with severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2). Whilst a number of studies have been performed worldwide on owned cats, limited data are available on stray, colony or shelter cats. We investigated SARS-CoV-2 infection in a stray cat population before and during human outbreaks of SARS-CoV-2 in cities in the Lombardy region in northern Italy, a high endemic region for SARS-CoV-2, using serological and molecular methods. A cohort of different samples were collected from 241 cats, including frozen archived serum samples from 136 cats collected before the 2019 coronavirus disease (COVID-19) pandemic and serum, pharyngeal and rectal swab samples from 105 cats collected during the SARS-CoV-2 outbreak. All pre-pandemic samples tested seronegative for antibodies against the nucleocapsid of SARS-CoV-2 using indirect enzyme linked immunosorbent assay (ELISA) test, while one serum sample collected during the pandemic was seropositive. No serological cross-reactivity was detected between SARS-CoV-2 antibodies and antibodies against feline enteric (FECV) and infectious peritonitis coronavirus (FIPC), Feline Immunodeficiency Virus (FIV), Feline Calicivirus (FCV), Feline Herpesvirus-1 (FHV-1), Feline Parvovirus (FPV), Leishmania infantum, Anaplasma phagocytophilum, Rickettsia spp., Toxoplasma gondii or Chlamydophila felis. No pharyngeal or rectal swab tested positive for SARS-CoV-2 RNA on real time reverse transcription-polymerase chain reaction (rRT-PCR). Our data show that SARS-CoV-2 did infect stray cats in Lombardy during the COVID-19 pandemic, but with lower prevalence than found in owned cats. This should alleviate public concerns about stray cats acting as SARS-CoV-2 carriers.

Evaluation of an in-house indirect enzyme-linked immunosorbent assay of feline panleukopenia VP2 subunit antigen in comparison to hemagglutination inhibition assay to monitor tiger antibody levels by Bayesian approach.

BACKGROUND: Feline panleukopenia virus (FPV) is an etiologic pathogen of feline panleukopenia that infects all members of Felidae including tigers (Panthera tigris). Vaccinations against FPV among wild felid species have long been practiced in zoos worldwide. However, few studies have assessed the tiger immune response post-vaccination due to the absence of a serological diagnostic tool. To address these limitations, this study aimed to develop an in-house indirect enzyme-linked immunosorbent assay (ELISA) for the monitoring of tiger antibody levels against the feline panleukopenia vaccine by employing the synthesized subunit capsid protein VP2. An in-house horseradish peroxidase (HRP) conjugated rabbit anti-tiger immunoglobulin G (IgG) polyclonal antibody (HRP-anti-tiger IgG) was produced in this study and employed in the assay. It was then compared to a commercial HRP-conjugated goat anti-cat IgG (HRP-anti-cat IgG). Sensitivity and specificity were evaluated using the Bayesian model with preferential conditional dependence between HRP-conjugated antibody-based ELISAs and hemagglutination-inhibition (HI) tests. RESULTS: The posterior estimates for sensitivity and specificity of two indirect ELISA HRP-conjugated antibodies were higher than those of the HI test. The sensitivity and specificity of the indirect ELISA for HRP-anti-tiger IgG and HRP-anti-cat IgG were 86.5, 57.2 and 86.7%, 64.6%, respectively, while the results of the HI test were 79.1 and 54.1%. In applications, 89.6% (198/221) and 89.1% (197/221) of the tiger serum samples were determined to be seropositive by indirect ELISA testing against HRP-anti-tiger and HRP-anti-cat, respectively. CONCLUSION: To the best of our knowledge, the specific serology assays for the detection of the tiger IgG antibody have not yet been established. The HRP-anti-tiger IgG has been produced for the purpose of developing the specific immunoassays for tigers. Remarkably, an in-house indirect ELISA based on VP2 subunit antigen has been successfully developed in this study, providing a potentially valuable serological tool for the effective detection of tiger antibodies.

Molecular and serological investigation of cat viral infectious diseases in China from 2016 to 2019.

In order to analyse the prevalence of cat viral diseases in China, including feline parvovirus (FPV), feline calicivirus (FCV), feline herpesvirus 1 (FHV-1), feline leukaemia virus (FeLV), feline immunodeficiency virus (FIV) and feline infectious peritonitis virus (FIPV), a total of 1,326 samples of cats from 16 cities were investigated from 2016 to 2019. Collectively, 1,060 (79.9%) cats were tested positive for at least one virus in nucleotide detection, and the positive rates of cat exposure to FeLV, FPV, FHV-1, FCV, FIV and FIPV were 59.6%, 19.2%, 16.3%, 14.2%, 1.5% and 0.5%, respectively. The prevalence of FHV-1 and FPV was dominant in winter and spring. Cats from north China showed a higher positive rate of viral infection than that of cats from south China. The virus infection is not highly correlated with age, except that FPV is prone to occur within the age of 12 months. In the serological survey, the seroprevalences of 267 vaccinated cats to FPV, FCV and FHV-1 were 83.9%, 58.3% and 44.0%, respectively. Meanwhile, the seroprevalences of 39 unvaccinated cats to FPV, FCV and FHV-1 were 76.9% (30/39), 82.4% (28/34) and 58.6% (17/29), respectively. This study demonstrated that a high prevalence of the six viral diseases in China and the insufficient serological potency of FCV and FHV-1 remind the urgency for more effective vaccines.

Cellular microRNA, miR-1343-5p, modulates IFN-I responses to facilitate feline panleukopenia virus replication by directly targeting IRAK1 gene.

Feline panleukopenia is an acute, highly contagious, and fatal infectious disease caused by feline panleukopenia virus (FPV) and has led to severe consequences on pets, economically important animals, and the wildlife industry. MicroRNAs (miRNAs) play significant roles in the host-pathogen interaction by modulating cellular factors expression which are essential for viral replication or host innate immune response to infection. However, the role of host miRNA response in FPV infection remains to be discovered. In this study, we screened nine host miRNAs associated with FPV infection that were previously implicated in innate immunity or antiviral functions. We found that miR-1343-5p overexpression strongly promoted FPV-BJ04 genomic DNA. Subsequently, the expression of host miR-1343-5p was upregulated by FPV-BJ04 infection in vitro and in vivo. In addition, we demonstrated that miR-1343-5p was a negative regulator of the IFN-I signaling pathway, thereby promoting FPV infection. Bioinformatic analysis combined with molecular biological assay indicated that interleukin-1 receptor-associated kinase 1 (IRAK1) is a putative target of miR-1343-5p. Collectively, our findings emphasize the importance of miR-1343-5p in host defense against FPV, thus, enhancing our understanding of its pathogenic mechanism.

Construction and Immunogenicity of Virus-Like Particles of Feline Parvovirus from the Tiger.

Feline panleukopenia, caused by feline parvovirus (FPV), is a highly infectious disease characterized by leucopenia and hemorrhagic gastroenteritis that severely affects the health of large wild Felidae. In this study, tiger FPV virus-like particles (VLPs) were developed using the baculovirus expression system. The VP2 gene from an infected Siberian tiger (Panthera tigris altaica) was used as the target gene. The key amino acids of this gene were the same as those of FPV, whereas the 101st amino acid was the same as that of canine parvovirus. Indirect immunofluorescence assay (IFA) results demonstrated that the VP2 protein was successfully expressed. SDS-PAGE and Western blotting (WB) results showed that the target protein band was present at approximately 65 kDa. Electron micrograph analyses indicated that the tiger FPV VLPs were successfully assembled and were morphologically similar to natural parvovirus particles. The hemagglutination (HA) titer of the tiger FPV VLPs was as high as 1:218. The necropsy and tissue sections at the cat injection site suggested that the tiger FPV VLPs vaccine was safe. Antibody production was induced in cats after subcutaneous immunization, with a >1:210 hemagglutination inhibition (HI) titer that persisted for at least 12 months. These results demonstrate that tiger FPV VLPs might provide a vaccine to prevent FPV-associated disease in the tiger.

Feline Parvovirus Seroprevalence Is High in Domestic Cats from Disease Outbreak and Non-Outbreak Regions in Australia.

Multiple, epizootic outbreaks of feline panleukopenia (FPL) caused by feline parvovirus(FPV) occurred in eastern Australia between 2014 and 2018. Most affected cats were unvaccinated.We hypothesised that low population immunity was a major driver of re-emergent FPL. The aim ofthis study was to (i) determine the prevalence and predictors of seroprotective titres to FPV amongshelter-housed and owned cats, and (ii) compare the prevalence of seroprotection between a regionaffected and unaffected by FPL outbreaks. FPV antibodies were detected by haemagglutinationinhibition assay on sera from 523 cats and titres ≥1:40 were considered protective. Socioeconomicindices based on postcode and census data were included in the risk factor analysis. The prevalenceof protective FPV antibody titres was high overall (94.3%), even though only 42% of cats wereknown to be vaccinated, and was not significantly different between outbreak and non-outbreakregions. On multivariable logistic regression analysis vaccinated cats were 29.94 times more likelyto have protective FPV titres than cats not known to be vaccinated. Cats from postcodes of relativelyless socioeconomic disadvantage were 5.93 times more likely to have protective FPV titres. Thepredictors identified for FPV seroprotective titres indicate targeted vaccination strategies in regionsof socioeconomic disadvantage would be beneficial to increase population immunity. The criticallevel of vaccine coverage required to halt FPV transmission and prevent FPL outbreaks should bedetermined.

Regional adaptations and parallel mutations in Feline panleukopenia virus strains from China revealed by nearly-full length genome analysis.

Protoparvoviruses, widespread among cats and wild animals, are responsible for leukopenia. Feline panleukopenia virus (FPLV) in domestic cats is genetically diverse and some strains may differ from those used for vaccination. The presence of FPLV in two domestic cats from Hebei Province in China was identified by polymerase chain reaction. Samples from these animals were used to isolate FPLV strains in CRFK cells for genome sequencing. Phylogenetic analysis was performed to compare our isolates with available sequences of FPLV, mink parvovirus (MEV) and canine parvovirus (CPV). The isolated strains were closely related to strains of FPLV/MEV isolated in the 1960s. Our analysis also revealed that the evolutionary history of FPLV and MEV is characterized by local adaptations in the Vp2 gene. Thus, it is likely that new FPLV strains are emerging to evade the anti-FPLV immune response.

Prevalence of serum antibody titres against feline panleukopenia, herpesvirus and calicivirus infections in stray cats of Milan, Italy.

The aim of the study was to determine the seroprevalence of feline panleukopenia virus (FPV), feline herpesvirus type 1 (FHV-1) and feline calicivirus (FCV) in stray colony cats from Milan, Italy. Cats were divided in groups based on age, gender, reproductive status, health status and colony of origin. Blood samples were tested with an in-clinic ELISA test. The possible presence of a link between the antibody titre or the presence of seropositive results and the independent variables (age, gender, reproductive status, health status and colony location) was assessed by means of multinomial and univariate logistic regression models, respectively. Seroprevalence of 85.4% was reported for FCV. The diffusion of the other two pathogens in the cat population was much lower compared to FCV, with 45.7% and 37.1% seroprevalence observed for FPV and FHV-1, respectively. An increase of antibody titres from kitten to senior was generally observed for the three pathogens. Age was a statistically significant variable for FHV-1, with senior cats significantly associated with higher antibody titres and higher percentages of seropositive animals compared to younger age groups. Neutered cats had significantly higher antibody titres and showed significantly higher FHV-1 seroprevalences compared to sexually intact cats. Colonies from two of the nine administrative districts of Milan showed significantly higher FPV seroprevalences compared to the others. No other significant differences were observed. Our results, based on cats belonging to 70 different colonies located in urban areas far from each other, suggest that the three viruses circulate in the feline population of stray cats in Milan. The feline calicivirus represents the most common circulating pathogen, as observed also in other studies worldwide. Finally, our results suggest that stray cats may be not adequately protected against FPV, FHV-1 and FCV and vaccination could be a possible strategic solution, especially for FPV.

Anti-feline panleukopenia virus serum neutralizing antibody titer in domestic cats with the negative or low hemagglutination inhibition antibody titer.

To evaluate the accuracy of hemagglutination inhibition (HI) test as the index of feline panleukopenia virus (FPV)-protective ability, sera from 153 FPV-vaccinated cats aged ≥7 months with HI titer of <1:10-1:40, were examined for serum neutralizing (SN) antibody. SN antibody was detected (≥1:10) in 33 (62.3%) of 53 HI antibody-negative cats, and ranged <1:10-1:160. This suggests that FPV-antibody detection sensitivity of HI test is lower than SN test, and SN test is more suitable for the assessment of FPV-vaccine effect than HI test especially in cats with negative or low HI titer. SN titer was 1:32, FPV-protective threshold, or higher in all cats with HI titers of ≥1:20, suggesting it may be appropriate to set protective HI threshold at 1:20.

Antibody response to feline panleukopenia virus vaccination in cats with asymptomatic retrovirus infections: a pilot study.

OBJECTIVES: Currently, there are only a few studies on how immunocompromised cats, such as cats infected with feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV), respond to vaccination. Therefore, this study measured feline panleukopenia virus (FPV) antibodies in retrovirus-infected cats within a period of 28 days after FPV vaccination, and compared the immune response to that of non-infected cats. METHODS: Eight asymptomatic retrovirus-infected cats (four FeLV, four FIV), and non-infected age-matched control cats (n = 67) were vaccinated with a commercial FPV modified live virus (MLV). Pre- and post-vaccination antibody titres were measured by haemagglutination inhibition (HI) on days 0, 7 and 28. An HI titre ⩾1:40 was defined as protective. An adequate response to vaccination was defined as a four-fold titre increase or higher. Comparison of the immune response of retrovirus-infected and non-infected cats was performed. RESULTS: Pre-vaccination FPV antibody titres ⩾1:40 were present in 100% (n = 8/8; 95% confidence interval [CI] 62.8-100) of retrovirus-infected and in 77.6% (n = 52/67; 95% CI 66.2-86.0) of non-infected cats. An adequate response to vaccination (titre increase ⩾four-fold) was seen in 1/8 retrovirus-infected cats (12.5%; 95% CI 0.1-49.2) compared with 22/67 non-infected cats (32.8%; 95% CI 22.8-44.8). In cats with high pre-vaccination titres (⩾1:160), a four-fold titre increase or higher was observed in 1/8 retrovirus infected cats (12.5%; 95% CI 0.1-49.2) compared with 4/42 non-infected cats (9.5%; 95% CI 3.2-22.6). None of the eight retrovirus-infected cats developed illness or vaccination side effects after vaccination with MLV against FPV within the 28 days. There were no significant differences between groups: for pre-vaccination titres; for at least four-fold titre increases following vaccination in either all cats or the cats with high pre-vaccination titres; and concerning adverse effects. CONCLUSIONS AND RELEVANCE: All retrovirus-infected asymptomatic cats had pre-vaccination FPV antibodies indicating protection against panleukopenia. Response of retrovirus-infected cats to vaccination was similar to the response of non-infected cats.

[Feline panleukopenia - the important role of antibodies]. / Feline Panleukopenie ­ die wichtige Rolle von Antikörpern.

Feline panleukopenia is an important infectious disease. Despite vaccination, panleukopenia remains common, particularly in young kittens. Development of active immunity after primary vaccination is essential for protection. Therefore, vaccination against panleukopenia is a core vaccine. Efficacy of primary vaccination can be reduced by maternally derived antibodies that can persist up to 20 weeks and interfere with the vaccination. In adult cats, antibody development after vaccination can be reduced during chronic disease or immunosuppression. Approximately 30% of adult cats lack antibodies. Evaluation of antibody titres in kittens enables calculation of the ideal time point to initiate primary vaccinations with the goal to establish effective immunity. In adult cats, evaluation of antibody titres is a useful alternative to avoid unnecessary vaccinations and to create an individual vaccination schedule. Only cats lacking antibodies should be vaccinated. Evaluation of antibodies in private practice can be performed using a rapid in-house test.

Antibody response to feline panleukopenia virus vaccination in healthy adult cats.

OBJECTIVES: According to prior studies, between 25.0% and 92.8% of adult cats have antibodies against feline panleukopenia virus (FPV) and thus are likely protected against FPV infection. It is, however, unknown how healthy adult cats with different antibody titres react to FPV vaccination in the field. Therefore, the aim of the study was to measure antibody titres in healthy adult cats within a period of 28 days after vaccination against FPV and to evaluate factors that are associated with a lack of adequate response to vaccination. METHODS: One hundred and twelve healthy adult cats were vaccinated with a vaccine against FPV, feline herpesvirus and feline calicivirus. Antibodies against FPV were determined before vaccination (day 0), on day 7 and day 28 after vaccination by haemagglutination inhibition (HI). A HI titre ⩾1:40 was defined as protective. An adequate response to vaccination was defined as a four-fold titre increase. Uni- and multivariate statistical analysis was used to determine factors associated with an adequate response. RESULTS: Pre-vaccination antibody titres of ⩾1:40 were present in 64.3% (72/112; 95% confidence interval [CI] 55.1-72.6). Only 47.3% (53/112; 95% CI 37.8-57.0) of cats had an adequate response to vaccination. Factors associated with an adequate response to vaccination were lack of previous vaccination (odds ratio [OR] 15.58; 95% CI 1.4-179.1; P = 0.035), lack of antibodies (⩾1:40) prior to vaccination (OR 23.10; 95% CI 5.4-98.8; P <0.001) and breed (domestic shorthair cats; OR 7.40; 95% CI 1.4-38.4; P = 0.017). CONCLUSIONS AND RELEVANCE: As none of the cats with high pre-vaccination antibody titres (⩾1:160) had an at least four-fold increase in FPV antibody titres, measurement of antibodies rather than regular revaccinations should be performed. Thus, evaluation of FPV antibody titre in cats with previous vaccinations against FPV are recommended prior to revaccination.

Sequence analysis of feline immunoglobulin mRNAs and the development of a felinized monoclonal antibody specific to feline panleukopenia virus.

In response to immunization, B-cells generate a repertoire of antigen-specific antibodies. Antibody-based immunotherapies hold great promise for treating a variety of diseases in humans. Application of antibody-based immunotherapy in cats is limited by the lack of species-specific complete sequences for mRNAs encoding rearranged heavy and light chain immunoglobulins in B cells. To address this barrier, we isolated mRNAs from feline peripheral blood mononuclear cells (PBMCs), and used available immunoglobulin sequences and 5' and 3' RACE to clone and sequence heavy and light chain immunoglobulin mRNAs. We recovered mRNA from PBMCs from two cats, cloned and sequenced the variable and constant domains of the feline heavy chains of IgG1a (IGHG1a), IgG2 (IGHG2), and IgA (IGHA), and the light chains (lambda and kappa). Using these sequences, we prepared two bicistronic vectors for mammalian expression of a representative feline heavy (IGHG1a) together with a light (lambda or kappa) chain. Here we report novel feline Ig sequences, a technique to express antigen-specific felinized monoclonal antibodies, and the initial characterization of a functional felinized monoclonal antibody against feline panleukopenia virus.

Efficacy of feline anti-parvovirus antibodies in the treatment of canine parvovirus infection.

OBJECTIVE: This prospective, randomised, placebo-controlled, double-blinded study aimed to evaluate efficacy of commercially available feline anti-parvovirus antibodies in dogs with canine parvovirus infection. METHODS: First, cross-protection of feline panleukopenia virus antibodies against canine parvovirus was evaluated in vitro. In the subsequent prospective clinical trial, 31 dogs with clinical signs of canine parvovirus infection and a positive faecal canine parvovirus polymerase chain reaction were randomly assigned to a group receiving feline panleukopenia virus antibodies (n=15) or placebo (n=16). All dogs received additional routine treatment. Clinical signs, blood parameters, time to clinical recovery and mortality were compared between the groups. Serum antibody titres and quantitative faecal polymerase chain reaction were compared on days 0, 3, 7, and 14. RESULTS: In vitro, canine parvovirus was fully neutralised by feline panleukopenia virus antibodies. There were no detected significant differences in clinical signs, time to clinical recovery, blood parameters, mortality, faecal virus load, or viral shedding between groups. Dogs in the placebo group showed a significant increase of serum antibody titres and a significant decrease of faecal virus load between day 14 and day 0, which was not detectable in dogs treated with feline panleukopenia virus antibodies. CLINICAL SIGNIFICANCE: No significant beneficial effect of passively transferred feline anti-parvovirus antibodies in the used dosage regimen on the treatment of canine parvovirus infection was demonstrated.

Feline Panleucopenia Virus NS2 Suppresses the Host IFN-ß Induction by Disrupting the Interaction between TBK1 and STING.

Feline panleucopenia virus (FPV) is a highly infectious pathogen that causes severe diseases in pets, economically important animals and wildlife in China. Although FPV was identified several years ago, little is known about how it overcomes the host innate immunity. In the present study, we demonstrated that infection with the FPV strain Philips-Roxane failed to activate the interferon ß (IFN-ß) pathway but could antagonize the induction of IFN stimulated by Sendai virus (SeV) in F81 cells. Subsequently, by screening FPV nonstructural and structural proteins, we found that only nonstructural protein 2 (NS2) significantly suppressed IFN expression. We demonstrated that the inhibition of SeV-induced IFN-ß production by FPV NS2 depended on the obstruction of the IFN regulatory factor 3 (IRF3) signaling pathway. Further, we verified that NS2 was able to target the serine/threonine-protein kinase TBK1 and prevent it from being recruited by stimulator of interferon genes (STING) protein, which disrupted the phosphorylation of the downstream protein IRF3. Finally, we identified that the C-terminus plus the coiled coil domain are the key domains of NS2 that are required for inhibiting the IFN pathway. Our study has yielded strong evidence for the FPV mechanisms that counteract the host innate immunity.

Effect of high-dose ciclosporin on the immune response to primary and booster vaccination in immunocompetent cats.

Ciclosporin (Atopica oral solution for cats 100 mg/ml; Novartis Animal Health) was recently approved for use in cats with feline hypersensitivity dermatitis. The immunosuppressant effect of ciclosporin on the ability of cats to mount an immune response following vaccination was determined. Thirty-two healthy, immunocompetent adult cats (16 cats/group) were treated with either ciclosporin for 56 days at a dose of 24 mg/kg once daily or sham dosed. Prior to treatment, cats had an adequate antibody response to primary vaccination against feline calicivirus (FCV), feline herpesvirus-1 (FHV-1), feline panleukopenia virus (FPV), feline leukemia virus (FeLV) and rabies. Booster vaccination or novel vaccination with feline immunodeficiency virus (FIV) was administered 28 days after initiation of treatment with ciclosporin. There were no differences between the ciclosporin-treated and control cats for FCV and FPV antibody titers following booster vaccination. There were delays/reductions in antibody response to FHV-1, FeLV and rabies in treated cats; however, adequate protection was achieved in response to all booster vaccinations. Following primary vaccination with FIV, control cats showed a response, but treated cats showed no antibody production. Adverse events commonly associated with ciclosporin treatment, including diarrhea/loose stool, vomiting, salivation and regurgitation, were reported. In adult cats treated with 24 mg/kg/day of ciclosporin (more than three times the therapeutic dose), vaccine titer levels were adequate for protection following booster vaccination. In contrast, treated cats failed to mount a humoral response to a novel (FIV) vaccination, suggesting that memory B-cell immune responses remain intact during repeated high-dose ciclosporin administration in cats, but that primary immune responses are impaired.

Feline parvovirus infection and associated diseases.

Feline panleukopenia, caused by the single-stranded DNA virus feline parvovirus (FPV), is a highly contagious and often lethal disease of cats and other Felidae. FPV, but also canine parvovirus (CPV) can be isolated from both healthy and diseased cats. In Germany, CPV was detected in only approximately 10% of feline samples, but in Southeast Asia, reports estimated that up to approximately 80% of diseased cats were infected with CPV. Infection spreads rapidly, especially in cells with high mitotic activity, such as bone marrow, lymphoid tissue and intestinal crypt cells. Anorexia, vomiting, diarrhoea, neutropenia and lymphopenia are common in clinically affected cases. In utero or neonatal infection can result in cerebellar hypoplasia. Depending on the severity of clinical signs, mortality ranges from 25 to 100%. Effective vaccination and thorough disinfection are of the utmost importance in the prevention of disease transmission in multi-cat households and animal shelters. If clinical signs develop, supportive treatment should be commenced. The efficacy of feline recombinant interferon and FPV antibodies has not been clearly demonstrated. Commercially available vaccines should induce protective immunity when administered according to current guidelines. Recent studies suggest that in some kittens, maternally derived antibodies (MDA) can persist for much longer than has been previously recognised. FPV serum antibody tests are available, but protection status needs to be interpreted with caution in kittens with MDA and a negative titre in adult cats does not necessarily denote lack of protection.