Examination of bovine serum samples submitted from the field in connexion with the Brucellosis Eradication Scheme showed the value of immunodiffusion tests made with a diethyl ether-water extract of a smooth virulent strain of

Sera from cattle vaccinated with the killed strain-45/20 adjuvant vaccine frequently gave appreciable reactions when examined by standard tests, namely the serum agglutination, complement fixation and Rose Bengal plate tests. When these reactions were weak, the immunodiffusion test usually gave one or more precipitation lines, but these were formed only against sub-surface antigens. When these reactions were strong enough to suggest natural infection, a line against the smooth surface lipopolysaccharide antigen was present in addition. Infrequently, a similar line occurred in the absence of significant reactions to the standard tests.

Sera from cattle vaccinated with living strain 19 less frequently gave appreciable reactions in the standard tests. When the reactions were weak, immunoprecipitation lines were often formed against the sub-surface antigens but seldom against the lipopolysaccharide; when they were stronger, a line against the lipopolysaccharide was usually formed in addition.

Sera from unvaccinated cattle usually gave negative results in all tests, but several that gave marked reactions in the standard tests also gave precipitation lines with the sub-surface antigens and the lipopolysaccharide antigen. One sample gave two lines with sub-surface antigens, but was otherwise negative.

In immunodiffusion tests with sodium dodecyl sulphate extracts of the rough strain 45/20 a single precipitation arc was formed with some but not all of the sera that gave marked reactions in the standard tests.


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