Interaction of specifically purified isotypes of bovine antibody to Brucella abortus in the haemolysis in gel test and enzyme-linked immunosorbent assay

The detection limits for purified bovine IgM, IgG1 and IgG2 antibody to Brucella abortus in the haemolysis in gel test and in an enzyme-linked immunosorbent assay (ELISA) were established. The limits for IgM, IgG1 and IgG2, respectively, were: 5500, 60 and 4850 ng of antibody in the lytic test and 2750, 3.5 and 16 ng in the ELISA test. Bovine IgG2 produced lysis only in the presence of fresh, whole bovine serum.

Comparative efficacy of an experimental S45/20 bacterin and a reduced dose of strain 19 vaccine against bovine brucellosis

Yearling beef heifers were vaccinated with 2 doses of an experimental Brucella abortus S45/20 bacterin or a reduced dose of strain 19 (S19) vaccine, or were used as nonvaccinated controls. None of the vaccinated heifers was positive by the acidified plate, Rivanol, complement-fixation, or card tests 5 months after inoculation. Sixteen of 21 heifers given S45/20 bacterin with trehalose dimycolate adjuvant had delayed hypersensitivity when skin was tested 7 months after initial vaccination, whereas none of the S19 vaccinates or controls was reactive. After natural breeding, pregnant heifers were challenge exposed at 3.5 to 5 months of gestation with 2.5 X 10(7) viable B abortus S2308 organisms in the conjunctival sac. Abortions occurred as follows: 16/19 (84.2%) of heifers given S45/20 bacterin, 6/12 (50.0%) of heifers vaccinated with S19, and 17/18 (94.4%) of the nonvaccinated controls. Of the 10 heifers that calved normally, only 3 (1 in each group) were seropositive. A correlation was not seen between skin hypersensitivity and acquired resistance. Possible reasons for the poor protection with a reduced dose of S19 vaccine and the failure of S45/20 bacterin to enhance cellular resistance are discussed.

Application of indomethacin as a potentiator of lymphocyte blastogenesis in Brucella abortus exposed cattle

Lymphocytes from Brucella abortus field strain infected, strain 19 vaccinated, non-exposed and field strain infected, but immunologically unresponsive cattle were incubated with B. abortus antigen and indomethacin. There were significant increases (P less than 0.005) in the blastogenic responses, as measured by [3H] thymidine uptake, in cultures with indomethacin as compared to cultures without indomethacin. Lymphocyte blastogenic responses to B. abortus antigen were potentiated by indomethacin in both B. abortus exposed and non-exposed cultures. However, potentiation of sensitized lymphocyte blastogenic responses by indomethacin was significantly greater (P less than 0.005) than that in non-exposed lymphocytes. Additionally, indomethacin significantly potentiated Brucella-induced lymphocyte blastogenic responses in lymphocytes from anergic cattle.

The serological response of adult cattle to vaccination with reduced dose Brucella abortus S19, a trial under Zambian conditions

A total of 250 adult cows and 13 (young) heifers, all seronegative for brucellosis, were vaccinated with a reduced dose (3 X 10(9) Strain 19 (S-19) vaccine. Twelve months after vaccination all cattle were negative to the serological tests. The results obtained are similar to those found by other authors and support the use of reduced dose S19 under the local conditions found in Zambia.

Detection of brucella antibodies of different immunoglobulin classes in cow milk by enzyme-linked immunosorbent assay

Enzyme-linked immunosorbent assays were conducted on milk of cows from which Brucella abortus was isolated and that of noninfected controls. Horseradish peroxidase-labeled rabbit antibovine immunoglobulins IgG, IgG1, and IgA were used as conjugates. A heat-killed whole-cell suspension of B abortus strain 19 was used as the antigen. Differences in antibody profiles were observed in milk of cows from which B abortus was isolated and in milk of noninfected cows. Antibody profiles were similar in milk of cows infected with B abortus and that of cows from which B abortus strain 19 was isolated.

The cultural and pathological examination of bulls serologically positive for brucellosis

The genitalia from 34 bulls were examined for the presence of Brucella lesions using histological, bacteriological and serological methods. Tissue fluids extracted from the various genital organs and the serums were examined using the serum agglutination test (SAT), the Rose Bengal plate agglutination test (RBPT), the complement fixation test (CFT) and the indirect haemagglutination test (IHLT) for the presence of Brucella antibody. Titres to one or more of these tests were found in 17 bulls and B. abortus was cultured from 5 of these. The testing of tissue fluids from genital organs did not increase the number of serologically positive animals.

Comparison of an agar-gel immunodiffusion test with other serological methods for differentiating Brucella infected from vaccinated cattle

An agar-gel immunodiffusion test was compared with other serological tests for detection of antibodies in the sera of 48 cattle vaccinated with Brucella abortus strain 19. Two hundred forty-two sera were tested over a 12 month period, and addition of positive reactions for each test resulted in totals of 170 for the card test, 74 for the standard tube-agglutination test, 71 for the 2-mercaptoethanol test, 64 for the dithiothreitol test and 22 for the agar-gel immunodiffusion test.

Haemolysis in gel test for detecting bovine antibodies to Brucella abortus lipopolysaccharide

Optimal reagent parameters for a haemolysis in gel test for detection of bovine anti-Brucella abortus antibody were established. Using an alkali-treated crude lipopolysaccharide antigen attached to J-negative bovine erythrocytes, 0.125 mg of antigen, 0.1 ml of erythrocytes and 0.4 ml of guinea pig complement were required to perform 15 tests with appropriate serum controls. The haemolysis in gel test and an IgM radioimmunoassay (RIA) procedure were compared for their ability to detect the onset of increased serum antibody levels and antibody levels in sera diluted to extinction. While the RIA was more sensitive in amount of antibody detected, the haemolysis in gel test was equally able to detect initiation of antibody synthesis.

Antibodies to Brucella abortus in sera from Strain 19 vaccinated and non-vaccinated cows as determined by enzyme linked immunosorbent assay and conventional serologic methods

The sensitivity of an enzyme linked immunosorbent assay was compared with 4 other serologic methods for detecting antibodies in B. abortus vaccinated and non-vaccinated cows. Antibodies were detected by ELISA in sera from more than 93% of the culture positive cows, however, less than 55% of the infected animals were identified by any other serologic method. Similarly, antibodies were detected in 82% of the culture negative cows by the ELISA method.

A study of cattle infected with Brucella abortus and which showed aberrant serological reactions

Sixty cows, 48 of which had been vaccinated with live Brucella abortus strain 19 (S19) or with killed B. abortus strain 45/20 (S45/20) and 12 of which were unvaccinated animals, were challenged with B. abortus strain 544. Ten of the 27 cattle found to be infected after challenge showed aberrant serological reactions to the Rose Bengal Plate test, serum agglutination test and/or complement fixation test. These 10 cattle were all previously vaccinated with S19 or S45/20. It was concluded that infection in cattle vaccinated with S19 or S45/20 may be more difficult to detect than infection in animals that have no history of vaccination.

Comparison of the complement fixation test and the indirect hemolysis test for cattle vaccinated and infected with Brucella abortus

The complement fixation test (CFT) and indirect hemolysis test (IHLT) were applied to sera collected from 60 cattle challenged with Brucella abortus 544. Of the 60 cattle, 48 were vaccinated with either B. abortus 19 or B. abortus 45/20 as calves or as adults. The remaining 12 cattle were not vaccinated. Of the 27 sera from cattle found to be infected, 9 showed aberrant reactions to the CFT. The advantages of the IHLT for these cattle were as follows. After challenge, the titers to the IHLT became positive earlier than or at the same time as the titers to the CFT, they persisted longer than the titers to the CFT, and they failed to show prozone reactions, which are a problem with the CFT. An additional advantage was that before challenge and after vaccination with strain 19, the titers to the IHLT rose later and declined earlier than the titers to the CFT. We concluded that the CFT used in conjunction with the IHLT improves the detection of infected cattle.

Leukocyte migration-inhibition responses of nonvaccinated and vaccinated heifers to experimental infection with Brucella abortus

The leukocyte migration agarose technique was used to show the leukocyte migration-inhibition responses of nonvaccinated and vaccinated heifers to experimental infection with Brucella abortus. All heifers had increased leukocyte migration inhibition after exposure to B abortus. Nonvaccinated heifers which aborted had the highest responses. The responses of the vaccinated heifers were significantly (P less than 0.01) lower than those of nonvaccinated heifers. None of the vaccinated heifers aborted.

The serological response of cattle to vaccines against brucellosis, as measured by the brucellosis radioimmunoassay and other tests

Serum sample were obtained from 281 heifers vaccinated with Brucella abortus strain 19, and from 50 heifers that had received two injections of killed B. abortus strain 45/20 adjuvant (K45/20A) vaccine. The serological response measured by the brucellosis radioimmunoassay (RIA) was compared with responses measured by other tests. The serological responses of cattle during the first weeks after strain 19 vaccination were found to give little guide to the frequency of persistent reactions. In the case of strain 19, persistent reactions were considered to be those occurring 12 or more months after vaccination. In heifers vaccinated at the recommended age, small numbers of persistent reactions were given by the RIA (four in 374 sera), the complement fixation test using warm fixation (CFTW) (six in 383) and cold fixation (one in 185), the serum agglutination test (two in 222) and the indirect haemolysis test (IHLT) (two in 369). The Rose Bengal plate test gave 74 persistent reactions in 374 sera. Five of the 50 heifers gave particularly prolonged responses to K45/20A vaccine. In these animals the RIA and IHLT remained positive for longer than the CFTW.

Localization of brucella antigens that elicit a humoral immune response in Brucella abortus-infected cells

Localization of brucella antigens, to which brucella-infected cattle make antibodies, and the surface characteristics of Brucella abortus smooth strain 19 and rough strain 45/20 were studied by the use of monospecific antisera in absorption tests, electron microscopy, and electrophoretic mobility of organisms in microelectrophoresis. Antigenic determinants of electrophoretically defined antigen A5 were present on the surface of B. abortus rough strain 45/20 organisms, and protein moieties were most probably exposed on the surface of this strain in contrast with smooth strain 19 organisms. Several antigens distinct from the smooth lipopolysaccharide complex, to which brucella-infected cattle make antibodies, were not detected on the surface of smooth organisms. Agglutinating antibodies present in anti-B. abortus strain 19 serum did not bind to all areas on the surface of the smooth cells, suggesting the presence of different antigenic moieties on their surface. It is also postulated that the surface of B. abortus rough strain 45/20 displays receptors able to strongly bind immunoglobulin molecules, as well as other serum components.

The effect of challenge with virulent Brucella abortus on beef cattle vaccinated as calves or adults with either Brucella abortus strain 19 or 45/20

Groups of female calves were vaccinated subcutaneously with the standard dose of Brucella abortus strain 19 (S19) or with B. abortus 45/20 (S45/20). These calves and non-vaccinated control calves were mated at 15 months of age and challenged by way of the conjunctival sac with B. abortus strain 544 (S544). The incidence of abortion, stillbirths, weanling calves and healthy calves was observed after challenge and specimens were collected for culture at parturition and slaughter. Fifteen healthy calves were born to 18 animals vaccinated with S19, 12 were born to 18 animals vaccinated with S45/20 and 2 were born to 8 animals that were not vaccinated. B. abortus was isolated from 5 of the animals vaccinated with S19, 13 of the animals vaccinated with S45/20 and 9 of the 12 animals that were not vaccinated. Only one of the 5 infected animals vaccinated with S19 was vaccinated as an adult.

Brucellosis in free-living African buffalo (Syncerus caffer): a serological survey

The rose bengal and complement fixation tests were successfully applied to buffalo (Syncerus caffer) sera. An overall occurrence of 23% positive reactors was obtained, but Brucella infection does not appear to act as an effective culling agent in buffalo. Any eradication programme must take free-living buffalo into account as a possible source of re-infection for cattle.

Ultrastructural localization of characterized antigens of Brucella abortus and distribution among different biotypes

The distribution of characterized antigens in extracts of representative strains of Brucella abortus biotypes 1 to 9 was investigated by hemagglutination and precipitation reactivity. An antigen designated X was present in high concentrations in sodium dodecyl sulfate extracts of all smooth strains examined, but in low concentrations in the rough strain 45/20 extract. Antigen beta was demonstrable in 8 out of 12 smooth strains of B. abortus, but antigen gamma was detected in only 3 of these strains. Vaccine strain 19 extract contained beta antigen but no detectable gamma antigen, whereas both these antigens were present in rough strain 45/20 at slightly lower concentrations that in strain 544/W extract. Immunoenzyme histochemical studies performed with an electron microscope showed that antigens beta, gamma, and X were all situated in the outer membrane envelope of the cell wall of B. abortus 544/W.

The bovine immune response to Brucella abortus IV. Studies with a double immunodiffusion test for antibody against A2

A double immunodiffusion test for precipitins against Brucella antigen A2 was developed and applied to a variety of samples. The A2 precipitins were produced by a heifer infected with B. abortus strain 2308, cattle vaccinated with killed B. melitensis strain H38 or live B. abortus strain 19 and by a dog infected with B. canis. Precipitins were also detected in the second International Standard for anti-Brucella abortus serum, in several anti-B. canis sera and at low levels in one anti-B. ovis serum tested. Antisera produced in calves against Yersinia enterocolitica serotype 0:9 had no anti-A2 activity despite titers greater than or equal to 1/1024 and greater than or equal to 1/80 in standard Brucella agglutination and CF tests, respectively. The test for A2 precipitins lacked specificity as weak reactions were obtained with five of 295 sera from brucellosis-free herds. This test was relatively insensitive, detecting precipitins in only 16 of 24 sera from infected cattle and 27 of 54 sera positive by complement fixation and enzyme labelled antiglobulin tests performed with whole cell and smooth lipopolysaccharide antigens, respectively. The A2 precipitins were detected in nine sera from five cattle, in two infected herds, which were negative by agglutination and complement fixation tests.

Levamisole potentiation of antigen specific lymphocyte blastogenic response in Brucella abortus exposed but nonresponsive cattle

Incubation of Brucella abortus (field strain) infected and strain 19 vaccinated bovine peripheral blood lymphocytes with B. abortus antigen and levamisole caused a consistently significant increase in [3H] thymidine uptake when compared to cultures without levamisole. Levamisole did not potentiate B. abortus-induced blastogenic response of lymphocytes from non-exposed cattle. A dose response study showed that 10 micrograms/culture induced maximum potentiation of B. abortus-induced lymphocyte stimulation. Using the 10 micrograms/well concentration of levamisole, further studies were conducted to determine the net potentiation of the blastogenic responses in lymphocytes from B. abortus (field strain) infected cattle. B. abortus strain 19 vaccinated but nonresponsive and non-exposed cattle. Levamisole significantly potentiated the B. abortus-induced lymphocyte blastogenesis in lymphocytes from unresponsive cattle.

The bovine immune response to Brucella abortus. III. Preparation of antisera against a Brucella component precipitated by sera of some infected cattle

Two methods are described for the partial purification of a high molecular weight, heat-resistant component (CO1) of sonicates of smooth and rough Brucella abortus which is precipitated by sera of some infected cattle. Method 1, a combination of gel filtration chromatography and polyacrylamide gel electrophoresis, was used to prepare CO1 from sonicates of a smooth field strain of B. abortus. Method 2, a combination of gel filtration chromatography and heat treatment, was used to obtain CO1, from sonicates of rough B. abortus strain 45/20. Rabbit antisera produced against CO1 prepared by either method contained only CO1 precipitins but were negative in standard agglutination and complement fixation tests conducted with whole cell antigens. Evidence is presented that CO1 is identical to Brucella antigen A2, and it is proposed that in future the designation A2 be employed.