Infection of cats with atypical feline coronaviruses harbouring a truncated form of the canine type I non-structural ORF3 gene

Feline Infectious Peritonitis: European Advisory Board on Cat Diseases Guidelines

Feline coronavirus (FCoV) is a ubiquitous RNA virus of cats, which is transmitted faeco-orally. In these guidelines, the European Advisory Board on Cat Diseases (ABCD) presents a comprehensive review of feline infectious peritonitis (FIP). FCoV is primarily an enteric virus and most infections do not cause clinical signs, or result in only enteritis, but a small proportion of FCoV-infected cats develop FIP. The pathology in FIP comprises a perivascular phlebitis that can affect any organ. Cats under two years old are most frequently affected by FIP. Most cats present with fever, anorexia, and weight loss; many have effusions, and some have ocular and/or neurological signs. Making a diagnosis is complex and ABCD FIP Diagnostic Approach Tools are available to aid veterinarians. Sampling an effusion, when present, for cytology, biochemistry, and FCoV RNA or FCoV antigen detection is very useful diagnostically. In the absence of an effusion, fine-needle aspirates from affected organs for cytology and FCoV RNA or FCoV antigen detection are helpful. Definitive diagnosis usually requires histopathology with FCoV antigen detection. Antiviral treatments now enable recovery in many cases from this previously fatal disease; nucleoside analogues (e.g., oral GS-441524) are very effective, although they are not available in all countries.

Development of Colorimetric Reverse Transcription Loop-Mediated Isothermal Amplification Assay for Detecting Feline Coronavirus

Simple Summary

Feline coronavirus infecting domestic cats can cause feline infectious peritonitis (FIP), a fatal infectious disease. Several relevant clinical diagnoses and molecular methods are complicated and often ambiguous for veterinarians. In this work developed a rapid, sensitive, specific, and easy-to-visualize colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay with a novel LAMP primer set that has high specificity was developed using neutral red as an indicator dye. This proposed procedure could reliably detect FCoV RNA from effusion fluids comparable to the conventional PCR method. Considering these advantages, the RT-LAMP developed here has great potential on FIP-associated FCoV surveillance. Together with other sophisticated molecular diagnostic tools, this method can further be exploited in clinical laboratories to inspect suspected cats with effusive FIP.

Abstract

Feline infectious peritonitis (FIP) is a worldwide fatal disease caused by a mutant feline coronavirus (FCoV). Simple and efficient molecular detection methods are needed. Here, sensitive, specific, rapid, and reliable colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP) was developed to detect the ORF1a/1b gene of FCoV from cats with suspected FIP using neutral red as an indicator. Novel LAMP primers were specifically designed based on the gene of interest. The isothermal assay could visually detect FCoV at 58 °C for 50 min. The RT-LAMP assay was highly specific and had no cross-reactivity with other related feline viruses. The detection limit of FCoV detection by RT-LAMP was 20 fg/µL. A blind clinical test (n = 81) of the developed RT-LAMP procedure was in good agreement with the conventional PCR method. In the light of its performance specificity, sensitivity, and easy visualization, this neutral-red-based RT-LAMP approach would be a fruitful alternative molecular diagnostic tool for veterinary inspection of FCoV when combined with nucleotide sequencing or specific PCR to affirm the highly virulent FIP-associated FCoV.

Identification and phylogenetic analysis of two canine coronavirus strains

Canine coronavirus (CCoV), a member of the genus Alphacoronavirus, is an enveloped, single-stranded positive-sense RNA virus that responsible for gastroenteritis in dogs. In this study, two CCoV isolates were successfully propagated from 53 CCoV-positive clinical specimens by serial passaging in A-72 cells. These two strains, CCoV JS1706 and CCoV JS1712, caused cytopathic effects in A-72 cells. The sizes of virus plaque formed by them differed in early passages. Electron microscopy revealed a large quantity of typical coronavirus particles with 80–120 nm in diameter in cell culture media and cytoplasm of infected cells, in which they appeared as inclusion bodies. RT-PCR analysis of S gene indicated that these two isolates were belonged to CCoV IIa subtype. Homology of RdRp, S, M and N proteins between the two strains were 100, 99.6, 99.2 and 100.0%, respectively, whereas they were 99.4–100%, 83.1–95.2%, 88.5–99.2% and 91.9–99.7% identity compared to CCoV II reference strains. Phylogenetic analysis of RdRp, S, M and N protein showed that they were closely related to CCoV II strains. These two subtype IIa isolates will be useful for evaluating the pathogenesis and evolution of CCoV and for developing diagnostic reagents and vaccines.

Clinical and molecular aspects of veterinary coronaviruses

Coronaviruses are a large group of RNA viruses that infect a wide range of animal species. The replication strategy of coronaviruses involves recombination and mutation events that lead to the possibility of cross-species transmission. The high plasticity of the viral receptor due to a continuous modification of the host species habitat may be the cause of cross-species transmission that can turn into a threat to other species including the human population. The successive emergence of highly pathogenic coronaviruses such as the Severe Acute Respiratory Syndrome (SARS) in 2003, the Middle East Respiratory Syndrome Coronavirus in 2012, and the recent SARS-CoV-2 has incentivized a number of studies on the molecular basis of the coronavirus and its pathogenesis. The high degree of interrelatedness between humans and wild and domestic animals and the modification of animal habitats by human urbanization, has favored new viral spreads. Hence, knowledge on the main clinical signs of coronavirus infection in the different hosts and the distinctive molecular characteristics of each coronavirus is essential to prevent the emergence of new coronavirus diseases. The coronavirus infections routinely studied in veterinary medicine must be properly recognized and diagnosed not only to prevent animal disease but also to promote public health.

First Complete Genome Sequence of a Feline Alphacoronavirus 1 Strain from Brazil

We identified a strain of Alphacoronavirus 1, FCoV-SB22, from a pool of fecal samples from domestic cats from a rural settlement in the municipality of Santa Bárbara, Pará, Brazil. The nucleotide identity with feline coronavirus was 91.5%.

We identified a strain of Alphacoronavirus 1, FCoV-SB22, from a pool of fecal samples from domestic cats from a rural settlement in the municipality of Santa Bárbara, Pará, Brazil. The nucleotide identity with feline coronavirus was 91.5%. The present study reports the first complete genome sequence of a feline coronavirus from Brazil.

Characterization of canine coronavirus spread among domestic dogs in Vietnam

Canine coronavirus (CCoV) is an important pathogen that causes enteritis in dogs, but there is no information on CCoV infection in Vietnam. To examine the prevalence of CCoV infection among Vietnamese dogs, 201 serum samples were analyzed by virus-neutralization (VN) test. The results showed that antibody against CCoV-II was present in 87 dogs (43.3%). To detect genes of CCoV, fecal samples collected from 30 diarrheic and 50 healthy dogs were examinated by RT-PCR, confirming that 2 diarrheic dogs and 5 healthy dogs were positive for CCoV. Nucleotide sequences of N-terminal region of spike (S) gene indicated that CCoV strains were divided into two subgenotypes, CCoV-IIa and -IIb, respectively. Furthemore, we succeeded in isolating CCoV/dog/HCM47/2015, the isolate was plaque-purified three times, and 3’-terminal one-third of the genome was analyzed. Interestingly, the plaque-purified virus had a large deletion in ORF3abc and E genes (1,165 nt), and a short deletion in ORF7b gene (60 nt), suggesting that these regions are not necessary for in vitro replication of CCoV. Next, the antigenicity between the isolated CCoV-IIb and the other CCoV-IIa was compared by VN test, revealing that antigenicty of the isolated CCoV is equal or higher than that of the other CCoV. In summary, two subgenotypes of CCoV-II are spreading among Vietnamese dogs. The isolated virus with a large deletion after in vitro passage may be useful for the development of vaccine, owing to its antigenicity and efficient viral growth in vitro.

Prevalence of canine coronavirus (CCoV) in dog in Japan: detection of CCoV RNA and retrospective serological analysis

We collected rectal swabs from dogs in Japan during 2011 to 2014, and canine coronavirus (CCoV) nucleocapsid gene was detected by RT-PCR. The relationship between CCoV infection and the manifestation of diarrhea symptoms was investigated, and a correlation was noted (df=1, χ²=8.90, P<0.005). The types of CCoV detected in samples from CCoV-infected dogs were CCoV-I in 88.9% and CCoV-II in 7.4%, respectively. We retrospectively investigated the seroprevalence of CCoV-I in dogs in Japan during 1998 to 2006. The sera were tested with a neutralizing antibody test. In the absence of CCoV-I laboratory strain, we used feline coronavirus (FCoV)-I that shares high sequence homology in the S protein with CCoV-I. 77.7% of the sera were positive for neutralizing anti-FCoV-I antibodies.

Full-length genome analysis of canine coronavirus type I

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The full-length genome of canine coronavirus type I was determined.

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Sequence analysis showed unique features with respect to canine coronavirus type II.

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By phylogeny, canine coronavirus type I formed a separate cluster.

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The results may contribute to the understanding of the Alphacoronavirus-1 evolution.

Canine coronavirus types I (CCoV-I) and II (CCoV-II) are usually responsible for mild enteritis in dogs. While the CCoV-II genome has been completely sequenced, to date there are no complete genomic sequence data available publicly for CCoV-I. Thus, the aim of the present study was to analyze the full-length genome of a CCoV-I prototype strain that had been recovered from a dog with diarrhea in Italy. CCoV-I strain 23/03 has a genome of 30,000 nucleotides, excluding the 3′ poly(A) tail, displaying the typical Alphacoronavirus-1 organization and the highest genetic relatedness to CCoV-II. However, two distinct features were observed in the CCoV-I genome: (i) the presence of an additional ORF between the spike (S) protein gene and ORF3a; (ii) the diversity of the S protein, which is more closely related to that of feline coronavirus type I and presents a furin cleavage site. The present study may contribute to a better understanding of the Alphacoronavirus-1 evolutionary pattern and may be paradigmatic of how coronaviruses evolve through gene losses, acquisition and exchanges among different members.

Characterisation of different forms of the accessory gp3 canine coronavirus type I protein identified in cats

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Accessory proteins of coronaviruses play a role in virus adaptation to a new host.

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Some FCoV harbour truncated gp3 proteins, an accessory protein peculiar of CCoV-I.

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Deletions of gp3 do not influence their basic features.

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Deletions impact the expression proteins levels in feline but not in canine cells.

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All proteins localise in the ER despite the absence of a specific retention signal.

ORF3 is a supplemental open reading frame coding for an accessory glycoprotein gp3 of unknown function, only present in genotype I canine strain (CCoV-I) and some atypical feline FCoV strains. In these latter hosts, the ORF3 gene systematically displays one or two identical deletions leading to the synthesis of truncated proteins gp3-Δ1 and gp3-Δ2. As deletions in CoV accessory proteins have already been involved in tissue or host switch, studies of these different gp3 proteins were conducted in canine and feline cell. All proteins oligomerise through covalent bonds, are N-glycosylated and are maintained in the ER in non-infected but also in CCoV-II infected cells, without any specific retention signal. However, deletions influence their level of expression. In canine cells, all proteins are expressed with similar level whereas in feline cells, the expression of gp3-Δ1 is higher than the two other forms of gp3. None of the gp3 proteins modulate the viral replication cycle of heterologous genotype II CCoV in canine cell line, leading to the conclusion that the gp3 proteins are probably advantageous only for CCoV-I and atypical FCoV strains.

Canine enteric coronaviruses: emerging viral pathogens with distinct recombinant spike proteins

Canine enteric coronavirus (CCoV) is an alphacoronavirus infecting dogs that is closely related to enteric coronaviruses of cats and pigs. While CCoV has traditionally caused mild gastro-intestinal clinical signs, there are increasing reports of lethal CCoV infections in dogs, with evidence of both gastrointestinal and systemic viral dissemination. Consequently, CCoV is now considered to be an emerging infectious disease of dogs. In addition to the two known serotypes of CCoV, novel recombinant variants of CCoV have been found containing spike protein N-terminal domains (NTDs) that are closely related to those of feline and porcine strains. The increase in disease severity in dogs and the emergence of novel CCoVs can be attributed to the high level of recombination within the spike gene that can occur during infection by more than one CCoV type in the same host.