Parental and revertant Brucella canis induced changes in the rabbit.

Chronic brucellosis was produced in the rabbit by parental and penicillin-induced L-phase revertant of Brucella canis. Animals in the experimental groups were injected with 1.2 x 10(8) organisms/ml of appropriate strains by specified routes at intervals. At a maximum of 12 weeks postinfection, animals were killed and samples were taken for bacteriology, serology, histology, immunofluorescent and electron microscopy. Results revealed faecal shedding in some animals from 72 hours up to three weeks postinfection. High agglutinating antibody titres of 1:1280 were sustained in all infected animals. Histopathological and ultrastructural changes attributed to the invading organisms were apparent and evidence of mitochrondriopathic changes are provided. The implication and indirect role of L-phase in brucellosis are discussed.     

Evaluation of pseudorabies viral antigens in the agar gel immunodiffusion test.

Procedures designed to extract pseudorabies viral (PRV) antigens from PRV-infected tissue cultures were investigated to determine whether differences in extraction method had an effect upon the final concentrated antigenic product. All four of the preparations made from PRV-infected tissue culture cells (trypsin extract and disrupted cells) or entire PRV-infected cultures (polysorbate 80 extract and (NH4)2SO4 precipitate) contained relatively large amounts of the same antigen, whereas cell-free PRV-infected tissue culture fluids did not contain significant amounts of this antigen. Specific antibody directed against this antigen was present in all PRV antisera tested. Two other antigens were observed in some of the preparations, but PRV antisera varied in their ability to precipitate with these antigens. Therefore, the number of precipitation lines observed in agar gel immunodiffusion between PRV preparations and PRV-positive antisera depended both upon the extraction method used to obtain the antigen and upon the specificity of the selected antiserum.     

Studies on the mechanism of vaccinal immunity to Marek''s disease

Current knowledge of the nature of the antigens and of the host immune responses in vaccinal immunity to Marek's disease is reviewed. It is suggested that a two-step mechanism of resistance operates. The first step involves humoral and cell-mediated responses directed against viral antigens; the second step occurs after challenge with Marek's disease virus and consists of cellmediated responses directed against tumour cells.