Determination of bovine lymphocyte responses to extracted proteins of Brucella abortus by using protein immunoblotting.

Isolation and identification of Brucella antigenic determinants important to cellular responses have been difficult. In this study, bovine peripheral blood mononuclear (PBM) cells from cattle vaccinated with Brucella abortus 19 proliferated to extracted bacterial proteins blotted onto nitrocellulose. Proteins were extracted from gamma-irradiated B. abortus 19 with a sodium dodecyl sulfate extraction buffer. The extracted proteins were separated electrophoretically by sodium dodecyl sulfate-polyacrylamide gel electrophoresis prior to electroblotting onto nitrocellulose. Nitrocellulose sections corresponding to individual lanes of the gel (containing all separated proteins) were then cultured with the PBM cells. Primary and secondary stimulation responses of the PBM cells with the whole protein blots were similar kinetically to the responses of the PBM cells stimulated with whole irradiated B. abortus 19 or with whole irradiated B. abortus 19 blotted onto nitrocellulose. Although lipopolysaccharide was determined to be associated with the extracted proteins and transferred onto the blots, the lipopolysaccharide did not stimulate cellular proliferation, as indicated by the antigen-specific secondary responses. Stimulating PBM cells with portions of the blot containing high (greater than 45,000)-, medium (25,000 to 45,000)- or low (25,000)-molecular-weight proteins demonstrated that the responding cells were specific only to the proteins of corresponding molecular weights. These results indicate that cellular responses to individual proteins can be studied without cloning the bacterial genes or purifying the individual proteins.

Plasmodium berghei malaria: effect of acute phase serum on immunity generated in rats by infection and by vaccination.

Acute phase serum (APS) given at the time of challenge with Plasmodium berghei inhibited the generation to immunity to the infecting plasmodia. Administered with a single dose of vaccine, it inhibited induction of immunity by the vaccine. Three weekly doses, the last given two weeks before infection, induced immunity. Administration of vaccine simultaneously with infection neither aggravated nor ameliorated the infection. These results indicate that the effect of administration of APS on immunity generated by immunization or infection is dose- and time-dependent. The depression of immunity induced by this serum is thus temporary, the host finally overcoming the depression and responding to the plasmodial antigen in the serum. The interaction of vaccine and infection observed indicates that the introduction of vaccine is not detrimental to the individual incubating infection; rather, the vaccine is rendered useless, the reducing the aggregate benefit of the immunization to the group.