Antibody in cattle experimentally infected with contagious bovine pleuropneumonia

Antibody responses in cattle experimentally infected with contagious bovine pleuropneumonia were assayed by the complement fixation (CF), plate agglutination (PA), and agar-gel diffusion precipitin (AGDP) tests. Sera were also fractionated by sucrose gradient centrifugation, by chromatography on diethylaminoethyl (DEAE)-cellulose columns, and by starch-block electrophoresis. Serum fractions were assayed for antibody by the CF and PA tests. Antibody was detected by the CF and PA tests from 7 days postinoculation (DPI) throughout the test period of 154 days. The AGDP test was the least sensitive and was negative after 28 DPI. By sucrose gradient centrifugal analysis, only 19S antibody could be detected in the 7 DPI sera, but 19 and 7S antibodies were found in the 14, 21, 28, 35, and 42 DPI sera. Only 7S antibody was found in sera subsequently collected until 154 DPI at the conclusion of the experiment. Results of chromatographic fractionation of sera on DEAE-cellulose columns showed that most of the CF antibody was adsorbed when 0.0175 m phosphate buffer (pH 6.3) was used for elution of proteins. Plate agglutination antibody activity was found in both immunoglobulin (Ig)G and IgM fractions from 7 to 42 DPI and only in the IgG fraction thereafter. By starch-block electrophoresis, the 14 DPI antibody was of beta mobility (IgM), whereas at 21 DPI the antibody mobility was gamma-beta. In the 28 and later DPI sera, CF antibody had gamma mobility.