Isolation and Genomic Characteristics of a Novel Pathogenicity Type I Feline Coronavirus in Mainland China

Feline coronavirus (FCoV) is an enveloped, positive-sense RNA virus, which is widespread among feline populations, and can cause a fatal serious disease called feline infectious peritonitis (FIP). According to the differences of antigen and genetic composition, FCoV consists of two genotypes, FCoV I and FCoV II. In this study, we have isolated and identified a FCoV I strain named HL2019. Based on the complete genome of HL2019, phylogenetic analysis showed that HL2019 strain formed in the cluster FCoV I which is more closed to human coronavirus 229E (HCoV 229E) and HCoV NL63, while the FCoV I stains is distantly related to FCoV II strains. Analyzing with RDP4 and Simplot software showed that the virus HL2019 is recombinant by the FCoV I China/ZJU1709 and FCoV I Netherlands/UU16 strains. Furthermore, the pathogenicity of HL2019 was evaluated in 9-12-month-old cats. Two of three challenged cats developed serious clinical signs and died at 28-day postchallenge (dpc). Real-time polymerase chain reaction (PCR) analysis showed that HL2019 has broad tissue tropism, especially in the duodenum with viral load up to 10⁴ copies/mg. In summary, our data show that we have successfully isolated a strain of FCoV I named HL2019 that is highly pathogenic to cats.