Veterinary Microbiology, 20 (1989) 339-348 339 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands D i s c r i m i n a t i o n B e t w e e n Sheep Antibodies to Brucella melitensis and to Brucella ovis P. P L A C K E T T 1, L.A. C O R N E R ~ , T. FIFIS 1, A.J. RADFORD ~, J.L. R I P P E R 1, CHEN NAICHANG ~ and LIU YUMEI ~ ~C.S.I.R.O. Animal Health Research Laboratory, Private Bag No. 1, Parkville 3052, Vic. (Australia) 'Harbin Veterinary Research Institute, Maduan Street, Harbin (China) (Accepted for publication 16 March 1989) A B S T R A C T Plackett, P., Corner, L.A., Fifis, T., Radford, A.J., Ripper, J.L., Chen, N.-C. and Liu, Y.-M., 1989. Discrimination between sheep antibodies to Brucella melitensis and to Brucella ovis. Vet. Microbiol., 20: 339-348. When preparations containing smooth BruceUa abortus lipopolysaccharide (LPS) were used as antigens in an ELISA, strong positive reactions were obtained with sera from sheep infected with Brucella melitensis or with BruceUa ovis. Oxidation of the LPS with sodium metaperiodate greatly reduced the extent of the cross-reactions with antisera to B. ovis, with little effect on the reactions with antisera to smooth B. melitensis. Periodate oxidation of hot saline extract (HSX) antigen of B. ovis markedly reduced its reactivity in ELISA with anti-B, ovis sera and eliminated cross-reactivity with anti-B, melitensis sera. The reactivity of H S X was maintained after treat- ment with proteinase K. A simple ELISA system, in which replicate samples from a single serum dilution were tested in parallel against both B. ovis HSX antigen and periodate-oxidised smooth phase B. abortus LPS, was evaluated. It was found to discriminate well between antibodies induced by vaccination or virulent infection with B. melitensis strains and those induced by infection with B. ovis. I N T R O D U C T I O N In many parts of the world, both BruceUa melitensis and Brucella ovis are found in sheep populations. Live attenuated smooth strains of B. melitensis and of BruceUa suis are widely used as vaccines to control B. melitensis infec- tions of sheep and goats. These strains include B. melitensis Rev. 1, used in many countries, and B. melitensis Strain M5 and B. suis Strain $2, developed and extensively used in China. In a recent report, Blasco et al. (1987) con- firmed and extended earlier findings by other groups that Rev. I would protect rams against B. ovis infection. They also noted that vaccination induced sig- nificant levels of antibody to B. ovis as measured by ELISA. 0378~1135/89/$03.50 © 1989 Elsevier Science Publishers B.V.