A soluble acid-heat extracted Brucella vaccine: Immunological and physiological studies in guinea pigs, rabbits and calves. 143 p. Dissertation. 1959. -- A soluble-type vaccine was prepared by the acid-heat extraction of Brucella abortus Strain 2 308 and its metabolic by-products in Stuart• s medium. A comparison was made, in guinea pigs, of 2-day-old and 13-day-old cultures for the preparation of the immunogenic agent. Further comparisons were made in guinea pigs and calves of the 13-day-old culture and cell-free 13-day-old culture vaccine. The agent made from the 2-day-old culture produced no significant protection against various challenge levels of virulent Br. abortus Strain 2308. The agent prepared from 13-day-old cultures not only produced significant protection against homologous strain challenge but, produced insignificant serum-agglutination titers at effective dosage levels. The 13-day-old whole and cell-free culture vaccines gave similar results in guinea pigs. In calves the 13-day-old whole-culture vaccine produced higher transient serum-agglutination titers than the 13-day-old cell-free culture vaccine. Protective studies in calves were inconclusive due to inadequate infection in the control animals. The vaccine was shown to be essentially protein in nature and contained two distinct fractions on paper electrophoretic examination. The less mobile fraction apparently contained the agglutinogenic material and the more mobile fraction apparently contained the immunogenic material. Removal of the Brucella cells, prior to acid-heat extraction, decreased the less mobile fraction by more than one-half. The degree of serum agglutinin titer response was apparently contingent on this fraction, which indicated the agglutinogens were an index of metabolic byproducts, but this did not imply that they were an index of protection. Paper electrophoretic serum-protein patterns of 15 male and 15 female rabbits were studied. It was determined that: the serum fraction percentages of normal rabbits showed little variation, with no differences between sex or breed. The various pathologic conditions were indicated first by serum-protein patterns, and later diagnosed by histopathological examination of necropsy material. An additional 14 rabbits with a natural Eimeria stiedae infection were also investigated. The use of paper electrophoresis as an aid in the selection of normal animals for experimental investigation was demonstrated. The 13-day-old whole culture vaccine was employed in rabbits to study serum-agglutinin titer response. The results indicated that the maximum gamma globulin response followed the peak agglutinin response by seven to twenty-one days, this indicated a secondary response the nature of which was not determined. Female rabbits responded to the vaccine with higher initial titers than males and the titer decline was one and one-half times more rapid in the males than. in the females. Sex was shown to be the most significant factor in this finding. Castration and ovario-hysterectomy indicated that the above results could be reversed when an estrogenic hormone was given to the castrates and when testosterone was given to the ovario-hysterectomized animals. Insufficient data was available to elucidate the role of steroid hormones in the serum-agglutinin titer response. / Ph. D.