Tatsuji Okabe

Molecular cloning of an Actinobacillus pleuropneumoniae outer membrane lipoprotein (Oml A) from serotype 5a

The gene encoding an outer membrane lipoprotein (OmIA) was cloned from Actinobacillus pleuropneumoniae strain NG-8 (serotype 5a). The deduced amino acid sequence of OmIA from strain NG-8 showed 61% identity to the OmIA from serotype 1 strain, which confers protective immunity to pigs. Southern blot analysis showed the presence of a sequence highly homologous to the omIA gene of strain NG-8 in strains of serotype 5a, 5b and 10. A specific serum against OmIA of NG-8 also detected a homologous protein in the strains of these serotypes. These data shows the presence of antigenic variability among A. pleuropneumoniae OmIA proteins.

Characterization of haemagglutinin from Bordetella bronchiseptica

In comparison with haemagglutinin (HA)-active strains of Bordetella bronchiseptica, the HA-deficient strains lacked a 150 kDa protein band on SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Adsorption of partially purified HA with bovine erythrocytes showed the loss of the 150 kDa band in the supernatant. This 150 kDa protein was purified by high-performance liquid chromatography using gel filtration columns. Electron microscopic examination revealed that the purified HA possessed a fine filamentous structure with dimensions of approximately 2 x 150 nm, which was considered to represent the filamentous haemagglutinin of B. bronchiseptica. Both the cell-free antigen obtained from the culture supernatant of phase-I strain of the bacteria and the bovine erythrocytes, which combined with crude HA showed an excellent protective activity of the challenge by virulent strain of B. bronchiseptica in mice.

A new protein with a particular thermoprecipitability in bovine milk.

Summary A new protein with a particular thermoprecipitability was isolated from bovine milk and tentatively termed milk pyroglobulin. The protein which was soluble at a relatively cold temperature was precipitated by raising the temperature to a certain degree depending on the concentration of the protein. The precipitate disappeared on recooling. This protein had the electrophoretic mobility of gamma globulin but did not carry either antigenic specificities of immunoglobulins or of free secretory component. The molecular weight was estimated to be approximately 60,000 in thin-layer gel filtration on Sephadex G-200 superfine gel, but the protein appeared to be convertible to molecules with a lower molecular weight of approximately 20,000 in the presence of bovine serum albumin. The presence of the albumin inhibited the thermoprecipitation as did α-lactalbumin but not IgG immunoglobulin from bovine colostrum. In SDS-polyacrylamide gel electrophoresis, the protein was separated into two components having a molecular weight of 19,000 and 10,000, respectively. Both components were thermoprecipitable and carried identical antigenic determinants.

Production of Monoclonal Antibody to Bovine Leukemia Virus Glycoprotein gp51 by in vitro Immunization

The monoclonal antibody against glycoprotein gp51 of bovine leukemia virus (BLV) envelope antigen was produced by in vitro immunization. This monoclonal antibody reacted with viral antigen was observed at the 69 kilodalton (kDa) glycoprotein. However, this monoclonal antibody was not involved in neutralizing. It was shown that in comparison with in vivo immunization, in vitro immunization has some advantages, namely a short immunization period and a small antigen quantity.

Protective Effects of Antibody against Intestinal Invasion by Escherichia coli

Seven Escherichia coli isolates from newborn calves with diarrhea were examined for enteropathogenic properties. One isolate penetrated into HeLa cells, four produced enterotoxin(s) and the remaining two possessed neither of these properties. Penetration of E. coli into HeLa cells was inhibited by antibody in bovine colostrum and in bovine and rabbit immune sera. The effective antibodies appeared to be mostly of the IgM class. The invasion by E. coli isolates was also examined by inoculation of the bacteria into the small intestine of E. coli‐immunized and non‐immunized guinea pigs. The isolate which penetrated into HeLa cells could penetrate the intestinal mucosa to be disseminated into various organs of non‐immunized guinea pigs but not of immunized guinea pigs, whereas no other isolates showed such pathogenicity in vivo. The inhibition of the invasion was observed when non‐immunized guinea pigs were inoculated with the bacteria together with colostral or serum antibody. The results show the importance of antibody in the local defense mechanism against E. coli invasion.