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The research relevance is determined by an insufficient study of morphological changes in the mesentery of cats with infectious peritonitis, even though their understanding is necessary to explain the mechanism of development of the main symptom of the disease – the effusion of fluid into the abdominal cavity. The research aims to establish gross and microscopic changes in the mesentery of the small intestine of cats with infectious peritonitis. The research employs gross and histological examination of the mesentery of the small intestine of cats at the infectious peritonitis. Slides of the mesentery were stained with haematoxylin and eosin. At dry and mixed forms of infectious peritonitis, gross and microscopic changes in the mesentery of the small intestine of cats are similar. In the mesentery grossly, small white spots were found, which protruded above the general surface and had a homogeneous appearance on the section. Microscopic changes in the mesentery of the small intestine of cats with dry and mixed forms of infectious peritonitis were also similar. When conducting histological studies, it was established that the mesothelium on the surface of the mesentery was necrotized or absent. The submesothelial layer of collagen fibres was necrotized or contained partially lysed and fragmented fibres. The loose fibrous connective tissue of the mesentery was swollen, necrotized in places, and infiltrated by lymphocytes, monocytes, and macrophages. Eosinophilic inclusion bodies were detected in the cytoplasm of some monocytes and macrophages. Foci of adipose tissue in the mesentery of the small intestine were infiltrated by lymphocytes and monocytes. Necrosis and destruction of their walls were found in blood vessels and destruction of endothelial cells in lymphatic vessels. Perivascular lymphoid nodules were markedly enlarged due to their swelling and an increase in the number of cells in them. In perivascular lymphoid nodules, expansion of lymphatic vessels and destruction of part of their endothelium cells were also established. Some of the lymphatic vessels of the mesentery were expanded and filled with lymph, which contained a significant number of lymphocytes, monocytes, and single neutrophils. The materials presented in the article are of practical value for anatomists, histologists and pathomorphologists, as well as for scientists who study the pathogenesis of infectious peritonitis in cats

The research relevance is determined by an insufficient study of morphological changes in the mesentery of cats with infectious peritonitis, even though their understanding is necessary to explain the mechanism of development of the main symptom of the disease – the effusion of fluid into the abdominal cavity. The research aims to establish gross and microscopic changes in the mesentery of the small intestine of cats with infectious peritonitis. The research employs gross and histological examination of the mesentery of the small intestine of cats at the infectious peritonitis. Slides of the mesentery were stained with haematoxylin and eosin. At dry and mixed forms of infectious peritonitis, gross and microscopic changes in the mesentery of the small intestine of cats are similar. In the mesentery grossly, small white spots were found, which protruded above the general surface and had a homogeneous appearance on the section. Microscopic changes in the mesentery of the small intestine of cats with dry and mixed forms of infectious peritonitis were also similar. When conducting histological studies, it was established that the mesothelium on the surface of the mesentery was necrotized or absent. The submesothelial layer of collagen fibres was necrotized or contained partially lysed and fragmented fibres. The loose fibrous connective tissue of the mesentery was swollen, necrotized in places, and infiltrated by lymphocytes, monocytes, and macrophages. Eosinophilic inclusion bodies were detected in the cytoplasm of some monocytes and macrophages. Foci of adipose tissue in the mesentery of the small intestine were infiltrated by lymphocytes and monocytes. Necrosis and destruction of their walls were found in blood vessels and destruction of endothelial cells in lymphatic vessels. Perivascular lymphoid nodules were markedly enlarged due to their swelling and an increase in the number of cells in them. In perivascular lymphoid nodules, expansion of lymphatic vessels and destruction of part of their endothelium cells were also established. Some of the lymphatic vessels of the mesentery were expanded and filled with lymph, which contained a significant number of lymphocytes, monocytes, and single neutrophils. The materials presented in the article are of practical value for anatomists, histologists and pathomorphologists, as well as for scientists who study the pathogenesis of infectious peritonitis in cats [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic caused by the coronavirus SARS-CoV-2 is continuing to spread globally. SARS-CoV-2 infections of feline and canine species have also been reported. However, it is not entirely clear to what extent natural SARS-CoV-2 infection of pet dogs and cats is in households. We have developed enzyme-linked immunosorbent assays (ELISAs) using recombinant SARS-CoV-2 nucleocapsid (N) protein and the receptor-binding-domain (RBD) of the spike protein, and the SARS-CoV-2 spike-pseudotyped vesicular stomatitis virus (VSV)-based neutralization assay to screen serum samples of 239 pet cats and 510 pet dogs in Minnesota in the early phase of the COVID-19 pandemic from mid-April to early June 2020 for evidence of SARS-CoV-2 exposures. A cutoff value was used to identify the seropositive samples in each experiment. The average seroprevalence of N- and RBD-specific antibodies in pet cats were 8% and 3%, respectively. Among nineteen (19) N-seropositive cat sera, fifteen (15) exhibited neutralizing activity and seven (7) were also RBD-seropositive. The N-based ELISA is also specific and does not cross react with antigens of common feline coronaviruses. In contrast, SARS-CoV-2 antibodies were detected at a very low percentage in pet dogs (~ 1%) and were limited to IgG antibodies against SARS-CoV-2 N protein with no neutralizing activities. Our results demonstrate that SARS-CoV-2 seropositive rates are higher in pet cats than in pet dogs in MN early in the pandemic and that SARS-CoV-2 N-specific IgG antibodies can detect SARS-CoV-2 infections in companion animals with higher levels of specificity and sensitivity than RBD-specific IgG antibodies in ELISA-based assays.

The COVID-19 pandemic caused by the coronavirus SARS-CoV-2 is continuing to spread globally. SARS-CoV-2 infections of feline and canine species have also been reported. However, it is not entirely clear to what extent natural SARS-CoV-2 infection of pet dogs and cats is in households. We have developed enzyme-linked immunosorbent assays (ELISAs) using recombinant SARS-CoV-2 nucleocapsid (N) protein and the receptor-binding-domain (RBD) of the spike protein, and the SARS-CoV-2 spike-pseudotyped vesicular stomatitis virus (VSV)-based neutralization assay to screen serum samples of 239 pet cats and 510 pet dogs in Minnesota in the early phase of the COVID-19 pandemic from mid-April to early June 2020 for evidence of SARS-CoV-2 exposures. A cutoff value was used to identify the seropositive samples in each experiment. The average seroprevalence of N- and RBD-specific antibodies in pet cats were 8% and 3%, respectively. Among nineteen (19) N-seropositive cat sera, fifteen (15) exhibited neutralizing activity and seven (7) were also RBD-seropositive. The N-based ELISA is also specific and does not cross react with antigens of common feline coronaviruses. In contrast, SARS-CoV-2 antibodies were detected at a very low percentage in pet dogs (~ 1%) and were limited to IgG antibodies against SARS-CoV-2 N protein with no neutralizing activities. Our results demonstrate that SARS-CoV-2 seropositive rates are higher in pet cats than in pet dogs in MN early in the pandemic and that SARS-CoV-2 N-specific IgG antibodies can detect SARS-CoV-2 infections in companion animals with higher levels of specificity and sensitivity than RBD-specific IgG antibodies in ELISA-based assays. [ABSTRACT FROM AUTHOR]

Feline coronavirus (FCoV) is a pathogenic virus commonly found in cats that causes a benign enteric illness and fatal systemic disease, feline infectious peritonitis. The development of serological diagnostic tools for FCoV is helpful for clinical diagnosis and epidemiological investigation. Therefore, this study aimed to develop an indirect enzyme-linked immunosorbent assay (iELISA) to detect antibodies against FCoV using histidine-tagged recombinant spike protein. FCoV S protein (1127–1400 aa) was expressed and used as an antigen to establish an ELISA. Mice and rabbits immunized with the protein produced antibodies that were recognized and bound to the protein. The intra-assay coefficient of variation (CV) was 1.15–5.04% and the inter-assay CV was 4.28–15.13%, suggesting an acceptable repeatability. iELISA did not cross-react with antisera against other feline viruses. The receiver operating characteristic curve analysis revealed an 86.7% sensitivity and 93.3% specificity for iELISA. Serum samples (n = 107) were tested for anti-FCoV antibodies, and 70.09% of samples were positive for antibodies against FCoV. The iELISA developed in our study can be used to measure serum FCoV antibodies due to its acceptable repeatability, sensitivity, and specificity. Additionally, field sample analysis data demonstrated that FCoV is highly prevalent in cat populations in Fujian province, China.

The receptor binding domain (RBD) of SARS-CoV-2 (SCoV2) has been used recently to identify the RBD sequences of feline coronavirus serotypes 1 (FCoV1) and 2 (FCoV2). Cats naturally infected with FCoV1 have been shown to possess serum reactivities with FCoV1 and SCoV2 RBDs but not with FCoV2 RBD. In the current study, COVID-19-vaccinated humans and FCoV1-infected laboratory cats were evaluated for interferon-gamma (IFNγ) and interleukin-2 (IL-2 ELISpot responses by their peripheral blood mononuclear cells (PBMC) to SCoV2, FCoV1, and FCoV2 RBDs. Remarkably, the PBMC from COVID-19-vaccinated subjects developed IFNγ responses to SCoV2, FCoV1, and FCoV2 RBDs. The most vaccinated subject (five vaccinations over 2 years) appeared to produce hyperreactive IFNγ responses to all three RBDs, including the PBS media control. This subject lost IFNγ responses to all RBDs at 9 months (9 mo) post-last vaccination. However, her IL-2 responses to FCoV1 and FCoV2 RBDs were low but detectable at 10 mo post-last vaccination. This observation suggests that initially robust IFNγ responses to SCoV2 RBD may be an outcome of robust inflammatory IFNγ responses to SCoV2 RBD. Hence, the T-cell responses of vaccine immunity should be monitored by vaccine immunogen-specific IL-2 production. The PBMC from chronically FCoV1-infected cats developed robust IFNγ responses to SCoV2 and FCoV2 RBDs but had the lowest IFNγ responses to FCoV1 RBD. The constant exposure to FCoV1 reinfection may cause the IFNγ responses to be downregulated to the infecting virus FCoV1 but not to the cross-reacting epitopes on the SCoV2 and FCoV2 RBDs., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Abstract: Feline coronavirus infection is common among domestic and exotic felid species and usually associated with mild or asymptomatic enteritis; however, feline infectious peritonitis (FIP) is a fatal disease of cats that is caused by systemic infection with a feline infectious peritonitis virus (FIPV), a variant of feline enteric coronavirus (FECV). Currently, there is no specific treatment approved for FIP despite the importance of FIP as the leading infectious cause of death in young cats. During the replication process, coronavirus produces viral polyproteins that are processed into mature proteins by viral proteases, the main protease (3C-like [3CL] protease) and the papain-like protease. Since the cleavages of viral polyproteins are an essential step for virus replication, blockage of viral protease is an attractive target for therapeutic intervention. Previously, we reported the generation of broad-spectrum peptidyl inhibitors against viruses that possess a 3C or 3CL protease. In this study, we further evaluated the antiviral effects of the peptidyl inhibitors against feline coronaviruses, and investigated the interaction between our protease inhibitor and a cathepsin B inhibitor, an entry blocker, against a feline coronavirus in cell culture. Herein we report that our compounds behave as reversible, competitive inhibitors of 3CL protease, potently inhibited the replication of feline coronaviruses (EC50 in a nanomolar range) and, furthermore, combination of cathepsin B and 3CL protease inhibitors led to a strong synergistic interaction against feline coronaviruses in a cell culture system. [Copyright &y& Elsevier]

Feline coronavirus (FCoV) is a pathogenic virus commonly found in cats that causes a benign enteric illness and fatal systemic disease, feline infectious peritonitis. The development of serological diagnostic tools for FCoV is helpful for clinical diagnosis and epidemiological investigation. Therefore, this study aimed to develop an indirect enzyme-linked immunosorbent assay (iELISA) to detect antibodies against FCoV using histidine-tagged recombinant spike protein. FCoV S protein (1127–1400 aa) was expressed and used as an antigen to establish an ELISA. Mice and rabbits immunized with the protein produced antibodies that were recognized and bound to the protein. The intra-assay coefficient of variation (CV) was 1.15–5.04% and the inter-assay CV was 4.28–15.13%, suggesting an acceptable repeatability. iELISA did not cross-react with antisera against other feline viruses. The receiver operating characteristic curve analysis revealed an 86.7% sensitivity and 93.3% specificity for iELISA. Serum samples (n = 107) were tested for anti-FCoV antibodies, and 70.09% of samples were positive for antibodies against FCoV. The iELISA developed in our study can be used to measure serum FCoV antibodies due to its acceptable repeatability, sensitivity, and specificity. Additionally, field sample analysis data demonstrated that FCoV is highly prevalent in cat populations in Fujian province, China. [ABSTRACT FROM AUTHOR]