Complete nucleotide sequences were determined by cDNA cloning of peplomer (S), integral membrane (M) and nucleocapsid (N) genes of feline infectious peritonitis virus (FIPV) type I strain KU-2, UCD1 and Black, and feline enteric coronavirus (FECV) type II strain 79-1683. Only M and N genes were analyzed in strain KU-2 and strain 79-1683, which still had unknown nucleotide sequences. Deduced amino acid sequences of S, M and N proteins were compared in a total of 7 strains of coronaviruses, which included FIPV type II strain 79-1146, canine coronavirus (CCV) strain Insavc-1 and transmissible gastroenteritis virus of swine (TGEV) strain Purdue. Comparison of deduced amino acid sequences of M and N proteins revealed that both M and N proteins had an identity of at least 90% between FIPV type I and type II. The phylogenetic tree of the M and N protein-deduced amino acid sequences showed that FIPV type I and type II form a group with FECV type II, and that these viruses were evolutionarily distant from CCV and TGEV. On the other hand, when the S protein-deduced amino acid sequences was compared, identity of only about 45% was found between FIPV type I and type II. The phylogenetic tree of the S protein-deduced amino acid sequences indicated that three strains of FIPV type I form a group, and that it is a very long distance from the FIPV type II, FECV type II, CCV and TGEV groups.Key words: Feline infectious peritonitis virus, Feline enteric coronavirus, Amino acid sequence Feline infectious peritonitis virus (FIPV), family Coronaviridae, genus Coronavirus, causes a chronic, progressive, immunologically mediated disease in domestic and exotic cats.The family Coronaviridae is divided into 3 distinct antigenic groups on the basis of serologic tests (18). One group contains mouse hepatitis virus, neonatal calf diarrhea coronavirus, human coronavirus OC43, hemagglutinating encephalomyelitis virus of swine and rat coronavirus. The second group contains avian infectious bronchitis virus. The third group consists of human respiratory coronavirus 229E, transmissible gastroenteritis virus (TGEV) of swine, porcine respiratory coronavirus, canine coronavirus (CCV), FIPV and feline enteric coronavirus (FECV). By using monoclonal antibodies we have shown the existence of at least 2 serotypes of FIPV, and the antigenicity of type II strain of FIPV and FECV were closer to TGEV and CCV than to type I FIPV (7,8). Both types I and II FIPV cause infectious peritonitis in cats, and the pathogenicity of type II FIPV is greater than that of type I FIPV (25). However, in the field, the prevalence of FIPV type I is high, and about 70% of feline cases of FIP are due to infection with type I (9).FIPV is an enveloped RNA virus with a single-stranded positive-sense RNA genome and the virions consist of three main structural proteins, peplomer (S) glycoprotein, integral membrane (M) glycoprotein and nucleocapsid (N) protein. The virus genome is at least 20 kilobases

In a mouse infection model, Salmonella enterica serovar Typhimurium can reside and proliferate within phagocytes in deeper tissues (35,47) and it can follow up to induce macrophage death by a possible necrosis (19). This model has been studied as a model of typhoid fever infection in humans caused by S. enterica serovars Typhi and Paratyphi that remains a significant problem in developing countries (46). Three vaccines against typhoid fever are presently in use. Two are injected, and one is orally administered. The two injected vaccines consist of killed whole bacteria and capsular material (Vi antigen) (51). The one live oral vaccine strain, serovar Typhi Ty21a, is an attenuated strain of mutations in galE (a gene in the galactose utilization pathway that affects O-antigen production) (10) and rpoS ( S ) (48, 49). Generally, an oral vaccine is cheaper, easier, and safer to administer than an injected vaccine. In human field trials, the oral vaccination with serovar Typhi Ty21a proved to be safe and effective, but its efficacy varied considerably from trial to trial (9, 51). To develop more promising vaccine strains, researchers have carried out human trials to test various serovar Typhi vaccine candidate strains that harbor precise mutations in specific genes (29 In the mouse model, at least three distinct genetic loci (ity, lps, and xid) affect the ability of the animal to successfully resist systemic infections by serovar Typhimurium. The ity s (designating susceptible response) allele of BALB/c or C57BL/6 mice and the lps d (designating defective response) allele of C3H/HeJ mice are associated with increased susceptibility to infection (30,62) and decreased susceptibility to endotoxin lethality (44), respectively. The ity phenotype is linked to Nramp1 (61), which encodes a macrophage-specific phosphoglycoprotein that is required by the phagosomal membrane during phagocytosis (15,61). The increased susceptibility to infection is associated with a nonconservative amino acid sub-

cDNA clones spanning the entire region of the peplomer (S) gene of feline infectious peritonitis virus (FIPV) type I strain KU-2 were obtained and their complete nucleotide sequences were determined. A long open reading frame (ORF) encoding 1464 amino acid residues was found in the gene, which was 12 residues longer than the ORF of the FIPV type II strain 79-1146. The sequences of FIPV type I and mainly -tPV type II were compared. The homologies at the N- (amino acid residues 1-693) and C- (residues 694-1464) terminal halves were 29.8 and 60.7%, respectively. This was much lower than that between FIPV type II and other antigenically related coronaviruses, such as transmissible gastroenteritis virus of swine and canine coronavirus. This supported the serological relatedness of the viruses and confirmed that the peplomer protein of FIPV type I has distinct structural features that differ from those of antigenically related viruses.

and Aomori-2, were isolated from FIV-seropositive domestic cats in Japan, and their proviral DNAs were amplified by PCR. The nucleotide sequences of their env and gag genes were determined and compared with those of previously described isolates: U.S. and European isolates and one Japanese isolate, TM2. Phylogenetic analyses of complete env gene sequences demonstrate that worldwide isolates are classified into three subtypes: Japanese TM2, Japanese Shizuoka, and non-Japanese subtypes (U.S. and European isolates), with 20% amino acid distances from each other. This pattern indicates that an evolutionary radiation of these three subtypes of FIV occurred at approximately the same time. The sequence data of gag genes also confirmed these results. Furthermore, the Sendai-1 isolate was identified as an imported FIV isolate.

ABSTRACT. Canine coronavirus (CCoV) has been reported to cause acute diarrhea mainly in young pups. CCoV and feline coronavirus are classified as group 1 coronaviruses. However, it has recently been reported in the United Kingdom that the group 2 coronavirus gene, which is more closely related to the bovine coronavirus (BCoV) and human coronavirus strain OC43, has been detected in respiratory tract tissue samples from dogs with respiratory disease. In this study, we examined the prevalence of antibodies to group 2 coronaviruses in domestic dogs and cats in Japan by a neutralization test using BCoV. All 104 feline serum samples were negative (<1:5) for antiBCoV antibodies. In contrast, of the 898 canine serum samples, 160 (17.8%) were positive for anti-BCoV antibodies, and the antibody titers ranged from 1:5 to more than 1:640, with 1:160 being the most frequent. No correlation was found between the titers of the antiBCoV and anti-CCoV antibodies in the 198 serum samples of dogs with a known history of CCoV vaccination. We amplified, by RT-PCR, group 2 coronavirus-specific hemagglutination/esterase genes in the oral swabs of a total of 10 young pups presenting with or having recovered from respiratory signs, or having anti-BCoV antibodies, with the result that 2 pups were positive for the hemagglutination/ esterase genes. These results strongly suggest that an unknown group 2 coronavirus as well as the known enteritis-causing CCoV (group 1 coronavirus) is prevalent among domestic dogs in Japan. KEY WORDS: bovine coronavirus, canine coronavirus, group 2 coronavirus, respiratory disease.