The monoclonal antibody (MAb) 5B19.2, which has virus-neutralizing and fusion inhibition activities, binds to an epitope (S2A) consisting of nine hydrophobic amino acids in the S2 subunit of the mouse hepatitis virus (MHV) spike (S) protein. This suggests that the S2A epitope may be involved in binding the virus to the MHV receptor and/or in virus-cell fusion. Co-immunoprecipitation analyses demonstrated that while the binding of virus to the receptor was blocked by anti-S1 MAbs, it was not blocked by the S2A antiserum, indicating that S2A was not involved in receptor-binding. The S proteins prepared in this study with mutations in the S2A epitope were either fusogenic or nonfusogenic and their fusogenicity did not correlate with the hydrophobic feature of the S2A epitope. All of these wt and mutated S proteins were similarly transported onto the cell membrane independent of their fusogenicity capability. These results suggest that S2A may mediate the fusion activity of the MHV S protein during virus entry into cells.The spike (S) protein of mouse hepatitis virus (MHV), a member of the family Coronaviridae, forms a spike projecting from the virion surface. The spike comprises two molecules of the S protein, each of which is a heterodimer consisting of two non-covalently bound subunits, S1 and S2 (Sturman et al., 1985). The S1 subunit makes up the globular part of the spike and the S2 subunit is the stalk portion (De Groot et al., 1987).An important biological function of the S protein is binding to the virus receptor, which is a member of the carcinoembryonic antigen gene family (Dveksler et al., 1991). The receptor-binding domain is located in the N-terminal 330 amino acids of the S1 subunit (S1N330) (Kubo et al., 1994 ;Suzuki & Taguchi, 1996), rather than on subunit S2 Author for correspondence : Fumihiro Taguchi.Fax j81 423 46 1754. e-mail taguchi!ncnp.go.jp (Taguchi, 1995), as is expected from the topologies of these subunits. Although the receptor-binding site has been mapped to S1N330, it is possible that additional regions in S1 and\or S2 may play an important role in virus-receptor interactions. Another important function is cell-cell and virus-cell fusion (Collins et al., 1982 ;Taguchi et al., 1992). Various regions in S2 are involved in fusion activity (Bos et al., 1995 ; Gallagher, 1996 ; Gallagher et al., 1991 ;Luo & Weiss, 1998).Monoclonal antibody (MAb) 5B19.2, which is specific for S2, has been reported to have virus-neutralizing (VN) and fusion-inhibition (FI) activities (Collins et al., 1982). Its binding site, epitope A (S2A), is composed of nine hydrophobic amino acids, Leu " (Fig. 1). The S2A epitope is located upstream of heptad repeat 1 (Luytjes et al., 1989) and forms a major antigenic determinant in the S2 subunit (Daniel et al., 1993). Antibodies specific to this epitope play an important role in protection in mice (Koolen et al., 1990). Although MAb 5B19.2 was isolated from mice immunized with MHV-4 (JHM strain), it is cross-reactive with other MHV strains (Talbot & Buchmeier, 1985). ...

ABSTRACT. S1 gene sequences for infectious bronchitis virus (IBV) strains of the 4/91 genotype (commonly called 793B) isolated from field outbreaks in Japan were analyzed to ascertain the relationship to 4/91 vaccine strain.

To evaluate the immune response induced by Japanese rabies vaccine for veterinary use as international units (IU), we measured levels of rabies antibody in serum samples from dogs by the rapid fluorescent focus inhibition test (RFFIT). In dogs immunized with a reference vaccine (potency level of 3.1 IU/ml), prepared by the same method as that used to produce commercial vaccine, and its dilutions (1 : 2 or 1 : 4), neutralizing-antibody levels increased to 1.0-2.0 IU/ml over a period of 1 month and then decreased to 0.2-1.5 IU/ml over a period of 1 year after the first vaccination and showed a remarkable increase to 12-47 IU/ml after the second vaccination. Sixty-five (74.7%) of the 87 serum samples from domestic dogs that were tested were seropositive (> or =0.1 IU/ml). However, the seropositive rate in dogs less than 1-year old at the time of vaccination was low (57.1%), and the antibody levels in these dogs were not sufficiently high for the rabies antibody titre in serum to be maintained for 1-year. Levels of rabies antibody in all serum samples were also measured by the virus neutralizing test (VNT), and a strong correlation (r > 0.95) was found between the results of the RFFIT and those of the VNT.

The off-label use of third-generation cephalosporins (3GCs) during in ovo vaccination or vaccination of newly hatched chicks has been a common practice worldwide. CMY-2-producing Escherichia coli strains have been disseminated in broiler chicken production. The objective of this study was to determine the epidemiological linkage of blaCMY-2-positive plasmids among broilers both within and outside Japan, because the grandparent stock and parent stock were imported into Japan. We examined the whole-genome sequences of 132 3GC-resistant E. coli isolates collected from healthy broilers during 2002 to 2014. The predominant 3GC resistance gene was blaCMY-2, which was detected in the plasmids of 87 (65.9%) isolates. The main plasmid replicon types were IncI1-Iγ (n = 21; 24.1%), IncI (n = 12; 13.8%), IncB/O/K/Z (n = 28; 32.2%), and IncC (n = 22; 25.3%). Those plasmids were subjected to gene clustering, network analyses, and plasmid multilocus sequence typing (pMLST). The chromosomal DNA of isolates was subjected to MLST and single-nucleotide variant (SNV)-based phylogenetic analysis. MLST and SNV-based phylogenetic analysis revealed high diversity of E. coli isolates. The sequence type 429 (ST429) cluster harboring blaCMY-2-positive IncB/O/K/Z was closely related to isolates from broilers in Germany harboring blaCMY-2-positive IncB/O/K/Z. pST55-IncI, pST12-IncI1-Iγ, and pST3-IncC were prevalent in western Japan. pST12-IncI1-Iγ and pST3-IncC were closely related to plasmids detected in E. coli isolates from chickens in North America, whereas 26 IncB/O/K/Z types were related to those in Europe. These data will be useful to reveal the whole picture of transmission of CMY-2-producing bacteria inside and outside Japan.