M gene analysis of canine coronavirus strains detected in Korea

Jeoung, Seok-Young; Ann, So-Yun; Kim, Hyun-Tae; Kim, Doo

Canine coronavirus (CCV) is an enveloped RNA virus with a positive-sense single-stranded genome of 27∼32 kb in length [21] . This virus belongs to group I of the Coronaviridae family that includes transmissible gastroenteritis virus (TGEV) of swine, porcine epidemic diarrhea virus, porcine respiratory coronavirus, feline infectious peritonitis virus, and human coronavirus 229E [23, 30] . The close antigenic relationship between feline coronavirus (FCoV) and CCV facilitates a potential for cross-species infection [3, 13, 16, 20] . For both FCoV and CCV, interspecies recombinations have been found by sequence analysis in different parts of the viral genome (e.g., the spike [S] gene encoding the 'spike' on the viral surface and the membrane [M] gene encoding the 'membrane' or 'integral membrane' protein) [10, 18, 19] . A new FCoV type, designated as FCoV type II, has emerged in the field due to recombination (in the S protein gene region) of FCoV type I and CCV [10] . Epidemiological investigations have shown that FCoV type I is the predominant field virus type in the UK, Austria, and Japan [1, 5, 11] . Furthermore, other studies have demonstrated that FCoV type I strains bind to feline aminopeptidase N (fAPN), a cell surface receptor in the lung, spleen, kidney, and gut while FCoV type II strains do not. The possible clinical and epidemiological impact of these findings is still unclear [5, 32] . In a recent study of S gene sequences obtained from field isolates, two types of CCV were identified. Pratelli et al. [24] [25] [26] [27] analyzed M gene sequences of CCV strains and found that the isolates belonged to two novel genetic clusters. The newly discovered FCoV-like CCV strain was different from typical CCV strains, and more closely related to FCoV strains than CCV strains [7] . Divergent FCoV-like CCV strains have emerged in particular from dog kennels and animal shelters. One study found that some FCoV-like CCV strains are more virulent than typical CCV strains and cause severe hemorrhagic diarrhea [4] . FCoV-like CCV stains have been found in Austria, Italy, and China [4, 26, 34] . Accurate genotyping for field CCV strains is undoubtedly important. However, only one molecular genetic study of Korean CCV strains has been performed to date [2] . Therefore, the present investigation was conducted to assess the molecular genetic features of CCV strains isolated in Korea. (Table 1) . Eight animals were male and 14 were female. The age of the dogs ranged from 5 to 31 weeks. Only 1 dog had received a CCV vaccination. Eleven dogs were vomiting and four had symptoms of respiratory disease such as coughing and nasal discharge. Canine parvovirus (CPV) was detected in all fecal samples in Table 3 . Sequence homology of nucleotides and deduced amino acids of the M gene in the Korean CCV isolates and reference strains which CCV was detected.