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Field strain feline coronaviruses with small deletions in ORF7b associated with both enteric infection and feline infectious peritonitis.

ABSTRACT: Feline coronavirus (FCoV) varies greatly from causing subclinical or mild enteric infections to fatal feline infectious peritonitis (FIP). The open reading frame (ORF) 7b of FCoV has been speculated to play a determining role in virulence as deletions were found to be associated with avirulent viruses. To further clarify the correlation between this gene and FIP, clinical samples from 20 cats that had succumbed to wet-type FIP and 20 clinically healthy FCoV-infected cats were analysed. The ORF7b from the peritoneal/pleural effusions of FIP cats and from the rectal swabs of healthy cats was amplified. Of the 40 FCoVs analysed, 32 were found to have an intact 7b gene whereas eight showed deletions of either three or 12 nucleotides. Surprisingly, among the eight viruses with deletions, three were from FIP diseased cats. These results show that deletions in the ORF7b gene are not constrained to low pathogenicity/enteric biotypes but also associated with pathogenicity/FIP biotypes of FCoV.

SUBMITTER: Lin CN

PROVIDER: S-EPMC7129072 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature

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Field strain feline coronaviruses with small deletions in ORF7b associated with both enteric infection and feline infectious peritonitis.

Lin Chao-Nan CN Su Bi-Ling BL Huang Hui-Pi HP Lee Jih-Jong JJ Hsieh Min-Wei MW Chueh Ling-Ling LL

Journal of feline medicine and surgery 20081113 6

Feline coronavirus (FCoV) varies greatly from causing subclinical or mild enteric infections to fatal feline infectious peritonitis (FIP). The open reading frame (ORF) 7b of FCoV has been speculated to play a determining role in virulence as deletions were found to be associated with avirulent viruses. To further clarify the correlation between this gene and FIP, clinical samples from 20 cats that had succumbed to wet-type FIP and 20 clinically healthy FCoV-infected cats were analysed. The ORF7b ...[more]

PMID: 19013091

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Project description:Feline infectious peritonitis (FIP), one of the most important lethal infections of cats, is caused by feline infectious peritonitis virus (FIPV), the high-virulence biotype of feline coronaviruses (FCoVs). FIPVs are suggested to emerge from feline enteric coronaviruses (FECVs) by acquiring mutations in specific genes in the course of persistent infections. Although numerous studies identified mutations predicted to be responsible for the FECV-FIPV biotype switch, the presumed roles of specific genetic changes in FIP pathogenesis have not been confirmed experimentally. Reverse genetics systems established previously for serotype I and the less common serotype II FCoVs were based on cell culture-adapted FIPV strains which, however, were shown to be unsuitable for FIP pathogenesis studies in vivo To date, systems to produce and manipulate recombinant serotype I field viruses have not been developed, mainly because these viruses cannot be grown in vitro Here, we report the first reverse genetics system based on a serotype I FECV field isolate that is suitable to produce high-titer stocks of recombinant FECVs. We demonstrate that these recombinant viruses cause productive persistent infections in cats that are similar to what is observed in natural infections. The system provides an excellent tool for studying FCoVs that do not grow in standard cell culture systems and will greatly facilitate studies into the molecular pathogenesis of FIP. Importantly, the system could also be adapted for studies of other RNA viruses with large genomes whose production and characterization in vivo are currently hampered by the lack of in vitro propagation systems.IMPORTANCE The availability of recombinant serotype I FCoV field isolates that are amenable to genetic manipulation is key to studying the molecular pathogenesis of FIP, especially since previous studies using cell culture-adapted FIPVs had proven unsuccessful. To our knowledge, we report the first serotype I FECV field isolate-based reverse genetics system that allows the production of high-titer recombinant virus stocks that can be used for subsequent in vivo studies in cats. The system represents a milestone in FCoV research. It provides an essential tool for studying the molecular pathogenesis of FIP and, more specifically, the functions of specific gene products in causing a fundamentally different progression of disease following acquisition of specific mutations. The system developed in this study will also be useful for studying other coronaviruses or more distantly related RNA viruses with large genomes for which suitable in vitro culture systems are not available.

Project description:Background and aimQuestions about the origin of coronavirus and its introduction to human beings have persisted. The detection of a variety of coronavirus related to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in bats and pangolins led to the widespread belief that SARS-CoV-2 originated from wild ani-mals and was introduced to humans through an inter-mediate animal. Thus, coronaviruses from animals, especially those in close contact with humans, have attracted particular attention. This study aimed to phylogenetically analyze feline enteric coronavirus (FECV), feline infectious peritonitis virus (FIPV), and SARS-CoV-2 found in cats in Surabaya amid the COVID-19 pandemic. The results will provide a basis for developing basic preventive and pet healthcare strategies.Materials and methodsSamples were collected on physical examinations of domestic and Persian cats (males and females) from March 2020 to March 2022. Samples were collected if there were clinical signs of FECV and FIP based on a veterinarian's diagnosis in several clinics in Surabaya. Laboratory examinations in this study were performed by reverse-transcription-polymerase chain reaction (RT-PCR) with primers for conserved regions of FIP and FECV, DNA sequencing was performed with Applied Biosystem Genetic Analyzer protocol, homology analysis was performed using Basic Local Alignment Search Tool NCBI, phylogenetic analysis was carried out with BioEdit 7.2 software, and sequences were compared with references from GenBank.ResultsSamples were collected from ten cats showing clinical signs of FECV and FIP, based on a veterinarian's diagnosis. On RT-PCR examinations performed with specifically designed primers for detecting FIPV in blood, peritoneal fluid, and feces, only one sample showed positivity for FIPV (1/10), namely, a peritoneal sample from a domestic cat in Surabaya. Homology analysis of the FIPV Surabaya isolate showed 98% similarity with FECV and FIPV reported in GenBank (MT444152 and DQ010921, respectively). In phylogenetic analysis, the FIPV Surabaya isolate was clustered together with SARS-CoV-2 of Clade A (MT198653) from Spain, SARS-CoV-2 Clade A (MT192765) from the USA, SARS-CoV-2 Clade D (039888) from the USA, and SARS-CoV-2 Clade F (MT020781) from Finland.ConclusionThis study revealed a relationship between the SARS-CoV-2 viruses that infect humans and cats (FECV), which is an important finding for those keeping cats at home. However, this finding requires further comprehensive support from laboratory studies.

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Field strain feline coronaviruses with small deletions in ORF7b associated with both enteric infection and feline infectious peritonitis.

Publications

Field strain feline coronaviruses with small deletions in ORF7b associated with both enteric infection and feline infectious peritonitis.

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