Tumor-infiltrating lymphocytes (TILs) in feline melanocytic tumors: A preliminary investigation.

The presence and the role of tumor-infiltrating lymphocytes (TILs) in different types of tumors, but particularly in melanoma, has become more and more investigated during the last decade, both in human and veterinary medicine. Melanocytic tumors are quite rare in cats, with diffuse iris melanoma being the most commonly diagnosed in this species. The aim of this study was to characterize the lymphocytic infiltration in feline melanocytic tumors and to analyze their association with the histological features of malignancy recognized in these tumors, as well as with the expression of the most commonly used immunohistochemical markers. Thirty-eight feline melanocytic tumors were retrospectively selected; histological and immunohistochemical characterization of the tumors (histologic criteria of malignancy; S100, Melan A, and PNL2 expression) and of TILs (presence/absence, density, distribution, and grade; CD3, CD20 expression) were performed and associations between them tested. Results showed that TILs grade increased with cellular pleomorphism (P < 0.05) and, within the group of cutaneous melanocytic tumors, also with the mitotic count (P < 0.05). On the other hand, TILs grade was inversely associated with the percentage of neoplastic cells positive for Melan A (P < 0.05) and PNL2 (P < 0.05). Both CD3+ and CD20+ lymphocytes increased significantly with TILs grade and in association with mitotic count, when stratified in low/high quantity. This preliminary study suggests that TILs in feline melanoma may be associated with histologic features of malignancy and loss of melanocytic-specific markers, such as Melan A and PNL2. Further studies, with a larger cohort and follow-up information, are recommended.

Modified-Live Feline Calicivirus Vaccination Reduces Viral RNA Loads, Duration of RNAemia, and the Severity of Clinical Signs after Heterologous Feline Calicivirus Challenge.

Feline calicivirus (FCV) is a common cat virus causing clinical signs such as oral ulcerations, fever, reduced general condition, pneumonia, limping and occasionally virulent-systemic disease. Efficacious FCV vaccines protect against severe disease but not against infection. FCV is a highly mutagenic RNA virus whose high genetic diversity poses a challenge in vaccine design. The use of only one modified-live FCV strain over several decades might have driven the viral evolution towards more vaccine-resistant variants. The present study investigated the clinical signs, duration, and amount of FCV shedding, RNAemia, haematological changes and acute phase protein reaction in SPF cats after subcutaneous modified-live single strain FCV vaccination or placebo injection and two subsequent oronasal heterologous FCV challenge infections with two different field strains. Neither clinical signs nor FCV shedding from the oropharynx and FCV RNAemia were detected after vaccination. After the first experimental infection, vaccinated cats had significantly lower clinical scores, less increased body temperature and lower acute phase protein levels than control cats. The viral RNA loads from the oropharynx and duration and amount of RNAemia were significantly lower in the vaccinated animals. No clinical signs were observed in any of the cats after the second experimental infection. In conclusion, FCV vaccination was beneficial for protecting cats from severe clinical signs, reducing viral loads and inflammation after FCV challenge.

Serological Screening for Antibodies against SARS-CoV-2 in Dutch Shelter Cats.

The COVID-19 pandemic raised concerns that companion animals might be infected with, and could become a reservoir of, SARS-CoV-2. As cats are popular pets and susceptible to Coronavirus, we investigated the seroprevalence of SARS-CoV-2 antibodies in shelter cats housed in Dutch animal shelters during the COVID-19 pandemic. In this large-scale cross-sectional study, serum samples of shelter cats were collected during the second wave of human COVID-19 infections in The Netherlands. Seroprevalence was determined by using an indirect protein-based ELISA validated for cats, and a Virus Neutralization Test (VNT) as confirmation. To screen for feline SARS-CoV-2 shedding, oropharyngeal and rectal swabs of cats positive for ELISA and/or VNT were analyzed using PCR tests. In 28 Dutch animal shelters, 240 shelter cats were convenience sampled. Two of these cats (0.8%; CI 95%: 0.1-3.0%) were seropositive, as evidenced by the presence of SARS-CoV-2 neutralizing antibodies. The seropositive animals tested PCR negative for SARS-CoV-2. Based on the results of this study, it is unlikely that shelter cats could be a reservoir of SARS-CoV-2 or pose a (significant) risk to public health.

Antibodies to SARS-CoV-2 in dogs and cats, USA.

To provide more complete data on SARS-CoV-2 infections in dogs and cats in the U.S., we conducted a serosurvey on convenience serum samples from dogs (n=1336) and cats (n=956) collected from 48 states of the USA in 2020. An ELISA targeting the antibody against nucleocapsid identified eleven positive and two doubtful samples in cats, and five positive and five doubtful samples in dogs. A surrogate neutralization assay detecting antibodies blocking the attachment of the spike protein to ACE2 was positive with three of the ELISA positive and doubtful samples, and one of 463 randomly selected ELISA negative samples. These four positive samples were confirmed by SARS-CoV-2 virus neutralization testing. All were from cats, in New York, Florida, and New Jersey (n=2). The serosurvey results, one of the largest yet completed on dogs and cats globally, support the OIE and CDC positions that currently there is no evidence that pets play a role in the spread of SARS CoV-2 in humans.

Use of feline herpesvirus as a vaccine vector offers alternative applications for feline health.

Herpesviruses are attractive vaccine vector candidates due to their large double stranded DNA genome and latency characteristics. Within the scope of veterinary vaccines, herpesvirus-vectored vaccines have been well studied and commercially available vectored vaccines are used to help prevent diseases in different animal species. Felid alphaherpesvirus 1 (FHV-1) has been characterised as a vector candidate to protect against a range of feline pathogens. In this review we highlight the methods used to construct FHV-1 based vaccines and their outcomes, while also proposing alternative uses for FHV-1 as a viral vector.

Isolation and phylogenetic analysis of strains of feline calicivirus in Beijing, China.

Feline calicivirus (FCV) is a contagious cat pathogen that causes oral ulceration and/or upper respiratory disease. In this study, we collected 61 samples from a pet hospital in Beijing and used PCR or RT-PCR to detect FCV and feline herpesvirus 1 (FHV-1). Approximately 44.3% (27/61) of the samples were FCV positive, and 23.0% (14/61) were coinfected with FCV and FHV-1. FCV was isolated from 15 samples. One isolate was from a cat with virulent systemic disease (VSD) signs, and 14 isolates were from cats with stomatitis or upper respiratory diseases. The range of genome sequence identity among these isolates was 76.1-100.0%. Four of the isolates were considered to be of the same strain, with sequence identity ranging from 99.5 to 99.7%, and two isolates, BJ-280 and BJ-288, had completely identical sequences. The genomic sequence identity ranged from 76.0 to 88.5% between the 15 isolates and several reference strains, including the F4 and F9 vaccine strains. These results demonstrate that many FCV strains are co-circulating in Beijing. Due to the diversity of FCV in Beijing, it is necessary to monitor the current prevalence of the virus. This study provides more information for the development of effective measures to control FCV.

SARS-CoV-2 Infections and Viral Isolations among Serially Tested Cats and Dogs in Households with Infected Owners in Texas, USA.

Understanding the ecological and epidemiological roles of pets in the transmission of SARS-CoV-2 is critical for animal and human health, identifying household reservoirs, and predicting the potential enzootic maintenance of the virus. We conducted a longitudinal household transmission study of 76 dogs and cats living with at least one SARS-CoV-2-infected human in Texas and found that 17 pets from 25.6% of 39 households met the national case definition for SARS-CoV-2 infections in animals. This includes three out of seventeen (17.6%) cats and one out of fifty-nine (1.7%) dogs that were positive by RT-PCR and sequencing, with the virus successfully isolated from the respiratory swabs of one cat and one dog. Whole-genome sequences of SARS-CoV-2 obtained from all four PCR-positive animals were unique variants grouping with genomes circulating among people with COVID-19 in Texas. Re-sampling showed persistence of viral RNA for at least 25 d-post initial test. Additionally, seven out of sixteen (43.8%) cats and seven out of fifty-nine (11.9%) dogs harbored SARS-CoV-2 neutralizing antibodies upon initial sampling, with relatively stable or increasing titers over the 2-3 months of follow-up and no evidence of seroreversion. The majority (82.4%) of infected pets were asymptomatic. 'Reverse zoonotic' transmission of SARS-CoV-2 from infected people to animals may occur more frequently than recognized.

The implication of autoantibodies in early diagnosis and monitoring of plasmonic photothermal therapy in the treatment of feline mammary carcinoma.

Feline mammary carcinoma (FMC) shows great similarities to human breast cancer in the cellular and molecular levels. So, in cats as in humans, the role of immune responses is indicated to detect and follow up the development of tumors. As a new breast cancer therapeutic approach, Plasmonic Photothermal Therapy (PPTT) is an effective localized treatment for canine and feline mammary-carcinoma. Its systemic effect has not been inquired yet and needs many studies to hypothesis how the PPTT eradicates tumor cells. In this study, it is the first time to detect (P53, PCNA, MUC-1, and C-MYC) feline autoantibodies (AAbs), study the relationship between PCNA AAbs and mammary-tumors, and investigate the effect of PPTT on the humoral immune response of cats with mammary-carcinoma through detection of AAbs level before, during, and after the treatment. The four-AAbs panel was evaluated in serum of normal and clinically diagnosed cats with mammary tumors using Enzyme-Linked Immunosorbent Assay. The panel showed 100% specificity and 93.7% sensitivity to mammary tumors. The panel was evaluated in PPTT monotherapy, mastectomy monotherapy, and combination therapy. PPTT monotherapy decreased AAbs level significantly while mastectomy monotherapy and combination therapy had a nonsignificant effect on AAbs level.

Vaccine Development for Severe Fever with Thrombocytopenia Syndrome.

Severe fever with thrombocytopenia syndrome (SFTS), which is caused by SFTS virus (SFTSV), is a tick-borne emerging zoonosis with a high case-fatality rate. At present, there is no approved SFTS vaccine, although the development of a vaccine would be one of the best strategies for preventing SFTS. This article focused on studies aimed at establishing small animal models of SFTS that are indispensable for evaluating vaccine candidates, developing these vaccine candidates, and establishing more practical animal models for evaluation. Innate immune-deficient mouse models, a hamster model, an immunocompetent ferret model and a cat model have been developed for SFTS. Several vaccine candidates for SFTS have been developed, and their efficacy has been confirmed using these animal models. The candidates consist of live-attenuated virus-based, viral vector-based, or DNA-based vaccines. SFTS vaccines are expected to be used for humans and companion dogs and cats. Hence for practical use, the vaccine candidates should be evaluated for efficacy using not only nonhuman primates but also dogs and cats. There is no practical nonhuman primate model of SFTS; however, the cat model is available to evaluate the efficacy of these candidate SFTS vaccines on domesticated animals.

SARS-CoV-2 Infection and Antibody Response in a Symptomatic Cat from Italy with Intestinal B-Cell Lymphoma.

Since the coronavirus disease (COVID-19) pandemic was first identified in early 2020, rare cases of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection in pet cats have been reported worldwide. Some reports of cats with SARS-CoV-2 showed self-limiting respiratory or gastrointestinal disease after suspected human-to-feline transmission via close contact with humans with SARS-CoV-2. In the present study, we investigated a cat with SARS-CoV-2 that was presented to a private animal clinic in Northern Italy in May 2020 in a weak clinical condition due to an underlying intestinal B-cell lymphoma. The cat developed signs of respiratory tract disease, including a sneeze, a cough and ocular discharge, three days after an oropharyngeal swab tested positive for SARS-CoV-2 viral RNA using two real-time reverse transcriptase polymerase chain reaction (RT-qPCR) assays for the envelope (E) and RNA-dependent RNA polymerase (RdRp) gene. Thus, SARS-CoV-2 viral RNA was detectable prior to the onset of clinical signs. Five and six months after positive molecular results, the serological testing substantiated the presence of a SARS-CoV-2 infection in the cat with the detection of anti-SARS-CoV-2 receptor binding domain (RBD) immunoglobulin (IgG) antibodies and neutralizing activity in a surrogate virus neutralization assay (sVNT). To the best of our knowledge, this extends the known duration of seropositivity of SARS-CoV-2 in a cat. Our study provides further evidence that cats are susceptible to SARS-CoV-2 under natural conditions and strengthens the assumption that comorbidities may play a role in the development of clinical disease.

A comparative approach on the activation of the three complement system pathways in different hosts of Visceral Leishmaniasis after stimulation with Leishmania infantum.

Visceral Leishmaniasis is an infectious disease that affects mainly humans and dogs, with the latter being important reservoirs of the parasite. Conversely, cats are naturally resistant. The immune system can offer important explanation to this problematic as there is no evidence on the role that the complement system plays in cats. In this context, effect of the complement system from human, dog and cat sera on Leishmania infantum was evaluated. Activation of the classical, alternative and lectin pathways was assessed through hemolytic and ELISA assays. Lytic activity of the complement on the parasite's viability was investigated by Transmission Electron Microscopy and Flow Cytometry. Complement proteins were more consumed in dog serum on the classical and alternative pathways, leading to less hemolytic activity, and only in cat serum they were consumed on the lectin pathway when incubated with L. infantum. Lytic activity on the parasite's surface was more accentuated in human serum, and varied throughout the parasite's developmental stages.

Protective Immunity and Persistent Lung Sequelae in Domestic Cats after SARS-CoV-2 Infection.

Severe acute respiratory syndrome coronavirus 2 readily transmits between domestic cats. We found that domestic cats that recover from an initial infection might be protected from reinfection. However, we found long-term persistence of inflammation and other lung lesions after infection, despite a lack of clinical symptoms and limited viral replication in the lungs.

Feline allergic diseases: introduction and proposed nomenclature.

BACKGROUND: Feline allergic diseases present as challenging problems for clinicians, not least because of the number of reaction patterns of the feline skin, none of which are specific for allergy. Furthermore, there is some controversy over the nomenclature that should be used in their description. OBJECTIVES: To review the literature, assess the status of knowledge of the topic and the extent to which these diseases could be categorized as atopic in nature, and make recommendations concerning nomenclature. METHODS: Atopic diseases in humans and cats were researched. A comparison then was made of the essential features in the two species. RESULTS: There were sufficient similarities between human atopic diseases and the manifestations of feline diseases of presumed allergic aetiology to justify the use of "atopic" to describe some of the feline conditions affecting the skin, respiratory and gastrointestinal tract. However, none of the allergic skin diseases showed features consistent with atopic dermatitis as described in man and the dog. CONCLUSIONS AND CLINICAL IMPORTANCE: The term "Feline Atopic Syndrome" (FAS) is proposed to encompass allergic diseases of the skin, gastrointestinal tract and respiratory tract, and "Feline atopic skin syndrome" (FASS) proposed to describe allergic skin disease associated with environmental allergies. We are not aware of any adverse food reactions in cats that are attributable to causes other than immunological reactions against the food itself. We therefore propose an aetiological definition of "Food Allergy" (FA) to describe such cases.

Immunopathogenesis of the feline atopic syndrome.

BACKGROUND: Feline diseases of possible allergic origin with similar clinical phenotypes can have a varied underlying pathogenesis. Clinical phenotype, precise aetiology and underlying immunopathogenesis all need to be considered if advances in this neglected area of dermatology are to be made. OBJECTIVES: To document the status of research into the immunopathogenesis of the diseases that fall within the spectrum of the feline atopic syndrome (FAS ), to summarize the conclusions, identify the limitations and recommend future research directions. METHODS AND MATERIALS: A search of the literature was undertaken. The strengths and validity of the data and the contributions to our current understanding of the immunopathogenesis were analysed. Skin diseases of presumed allergic aetiology and asthma were assessed separately, as was the role of antibodies, cells and cytokines in each. RESULTS: The research varied in its quality and its impact often was limited by a failure to employ strict criteria in case selection. This reflected the difficulties of skin reaction patterns associated with a number of inciting causes. Research into feline asthma was handicapped by the difficulties of investigating clinical material, and much of the useful information was derived from experimental models. CONCLUSIONS AND CLINICAL IMPORTANCE: The evidence reviewed was supportive of a role for immunoglobulin (Ig)E in the pathogenesis of both feline atopic skin syndrome (FASS) and asthma, albeit not strongly so. The inflammation noted in both FASS and asthma is accompanied by eosinophils and lymphocytes, and these findings, together with the cytokine expression, are suggestive in some (not all) cats of T-helper type 2 immune dysregulation.

Pyometra and estrous cycle modulate the uterine expression of the kisspeptin system and angiogenic and immune factors in cats.

Failures in hypothalamic kisspeptin/Kiss1r signaling are associated with infertility, and in vitro studies have shown that kisspeptin can modulate angiogenesis and immune activity. Because there is no in vivo research on the functional relationship between these factors in the reproductive system, especially in domestic cats, we evaluated the expression profile of kisspeptin/Kiss1r and angiogenic and immunological mediators in the genital tract of cyclic cats and of those with pyometra. The uterus of cats in diestrus exhibited greater gene and protein expression of Kiss1, as well as Vegf, Pigf, Mif, and Il6. In contrast, Kiss1r presented greater expression in proestrus/estrus, similarly to that observed for the immunostaining of INFγ, MIF, TNFα, and IL10. These factors were positively correlated with Kiss1 and/or Kiss1r, and a positive correlation between Kiss1 and Kiss1r was also observed in the uterus of cats during the estrous cycle. Cats with pyometra showed greater immunostaining of Kiss1 and Kiss1r on the endometrial surface and reduced immunostaining of Kiss1 in deep glands, whereas there was a significant reduction in Vegf, Pigf, Mif, and Il6 mRNA, and an increase in Tnf mRNA. The findings reveal that there is a gene correlation between kisspeptin/Kiss1r and angiogenic and immune mediators in the uterus of the domestic cat, which is modulated by the estrous cycle, and that pyometra affects the expression of these mediators. This study suggests, for the first time, a functional relationship between the Kiss/Kiss1r system and angiogenic and immune mediators in the female genital tract.

High seroprevalence of feline morbilliviruses in free-roaming domestic cats in Chile.

Feline morbillivirus infections have gained increased attention due to repeated reports of their association with urinary tract disease in cats. In the present study, 112 serum samples from free-roaming domestic cats in Chile were tested for antibodies against feline morbillivirus genotypes 1 and 2 (FeMV-1 and FeMV-2) using an indirect immunofluorescence assay. In total, 63% of the animals showed antibodies against one or both FeMV genotypes. Antibodies directed exclusively against FeMV-2 were significantly more prevalent in male cats. The correlation of sex and FeMV-2 infection might give insight into potential routes of transmission. We provide, for the first time, serological data on FeMV in Chile.

Toxoplasma gondii Seropositivity and Associated Risk Factors in Cats (Felis catus) in Three Provinces in Northeastern China from 2013 to 2019.

Toxoplasma gondii is an important protozoan parasite that can infect a range of animals. Cats are the most important definitive hosts for T. gondii. Therefore, an assessment of the level of T. gondii infection in cats is of public health importance. As limited information about seroprevalence of T. gondii infection in cats in northeastern China was available, 854 serum samples, including 235 cats in Jilin province, 267 cats in Liaoning province, and 352 cats in Heilongjiang province, were examined by an indirect hemagglutination assay (IHA) test, between September 2013 and July 2019. The overall seroprevalence of T. gondii was 19.09% (163/854) at the cutoff 1:64, with 19.60% (69/352), 18.29% (43/235), and 19.10% (51/267) in Heilongjiang, Jilin and Liaoning, respectively. Logistic regression analysis showed that mode of life was highly related to T. gondii infection in cats at the investigation areas. These results could provide foundation data for prevention and control of T. gondii prevalence in these regions. Moreover, the results also suggested that the effective control strategies should continue to be performed.

Antigen detection: Insights into Toxocara and other ascarid infections in dogs and cats.

Detection of ascarid excreted or secreted (E/S) molecules is an alternative approach to the identification of infection by egg flotation. E/S molecules serve as direct markers for the ascarid nematode commonly found in cats and dogs (Toxocara spp., Toxascaris leonina and Baylisascaris procyonis). The nematode derived E/S material mixes with the intestinal contents of the host animal and is available for detection as a coproantigen in the host's faeces. Antigen capture immunological techniques allow sensitive coproantigen detection. Different patterns of antigen to egg agreement are demonstrated in an experimental Toxocara canis infection throughout the prepatent, patent, and post-treatment phases. Examination of faecal samples from a large field population of dogs and cats tested for both egg shedding and antigen indicates that more infections were identified by antigen. Host age influences the agreement of antigen and Toxocara egg results. Older dogs and cats were less likely to have a patent infection (egg positive and antigen positive) result pattern. An egg observation in the absence of antigen detection may indicate a spurious egg. The impact of spurious eggs was further examined by comparisons of cohorts of dogs separated by presence or absence of a pseudoparasite observation or by egg semi-quantification bin. Lastly, the antigen to egg agreement was calculated for other ascarid species.

Critically appraised topic on adverse food reactions of companion animals (9): time to flare of cutaneous signs after a dietary challenge in dogs and cats with food allergies.

BACKGROUND: At this time, elimination diets followed by oral food challenges (OFCs) represent the "gold standard" for diagnosing skin-manifesting food allergies (FA) in dogs and cats. Regrettably, there is no clear consensus on how long one should wait for clinical signs to flare after an OFC before diagnosing or ruling-out a FA in a dog or a cat. RESULTS: We searched two databases on October 23, 2019 to look for specific information on the time for a flare of clinical signs to occur during OFCs after elimination diets in dogs and cats with skin-manifesting FAs. Altogether, we reviewed the study results of nine papers that included 234 dogs and four articles containing data from 83 cats. As multiple OFCs could be done in the same patient and not all animals included were subjected to an OFC, we were able to compile 315 and 72 times to flare (TTF) after an OFC in dogs and cats, respectively. When regrouping all cases together, about 9% of dogs and 27% of cats exhibited a flare of clinical signs in the first day after an OFC; 21% of dogs and 29% of cats had such relapse by the end of the second day. The time needed for 50 and 90% of dogs to exhibit a deterioration of clinical signs (TTF50 and TTF90) was 5 and 14, respectively; in cats, these times were 4 and 7 days, respectively. By 14 days after an OFC, nearly all food-allergic patients from both species had had a relapse of clinical signs. These results are limited by the likely under-reporting of flares that occur on the first day immediately following an OFC, the time in which IgE-mediated acute allergic reactions typically develop. CONCLUSION: Veterinary clinicians performing an OFC need to wait for 14 and 7 days for more than 90% of dogs and cats with a skin-manifesting FA to have a flare of clinical signs, respectively.

Survey of Dirofilaria immitis antigen and antibodies to Leishmania infantum and Toxoplasma gondii in cats from Madeira Island, Portugal.

BACKGROUND: Dirofilaria immitis, Leishmania infantum and Toxoplasma gondii are zoonotic parasites which can affect domestic cats. Considering the lack of published data from the local feline population, this study aimed to assess infection with or exposure to these pathogens in cats from Madeira Island, Portugal. METHODS: One hundred and forty-one domestic cats (77 males and 64 females; median age: 2 years) were sampled at a veterinary medical centre in Funchal, from September 2018 to January 2019. Serum samples were tested for D. immitis antigen, with an enzyme-linked immunosorbent assay kit, and for antibodies to Leishmania spp. or to T. gondii, with the direct agglutination test and the modified agglutination test, respectively. RESULTS: Five cats (3.5%; 95% confidence interval, CI: 1.2-8.1) were positive to D. immitis; no cats were seropositive to Leishmania spp. (0%; 95% CI: 0-2.6%); and 43 cats (30.5%; 95% CI: 23.0-38.8%) were seropositive to T. gondii. Prevalence of the D. immitis antigen was significantly different between cats that received ectoparasiticides and those which did not (0 vs 12.2%; P = 0.009). Prevalence of antibodies to T. gondii was significantly different between juvenile and adult cats (12.8 vs 38.0%; P = 0.007). There were two cats concurrently positive to D. immitis and T. gondii, but no statistical association between these two dependent variables was found (P = 0.641). CONCLUSIONS: To our knowledge, this is the first report of the presence of parasites D. immitis and T. gondii in the feline population of Madeira Island. Knowledge on the epidemiological situation of these and other zoonotic pathogens should raise awareness, both at the veterinary medical and public health levels, and contribute to promoting prevention and control.