Enzyme immunoassay for detection of antibodies specific for staphylococcal alpha haemolysin in bovine milk

A field trial with an experimental vaccine against Staphylococcus aureus mastitis in cattle. 2. Antibody response

A Staphylococcus aureus vaccine containing whole, inactivated bacteria with pseudocapsule and alpha and beta toxoids with a mineral oil as adjuvant, was used in a field trial. Heifers were injected in the area of the supramammary lymph nodes with vaccine or placebo twice before calving and observed and sampled throughout their first lactation. Antibody response toward the pseudocapsule and the alpha toxin was significant in serum from the vaccinated cows. These antibody concentrations were significantly higher in serum and milk during the entire lactation compared with that of the controls. The antibody response to the beta toxin was moderate in serum from vaccinated cows; no differences in antibody concentrations in milk were significant between groups. The antibody response to the pseudocapsule consisted of the IgG1 and IgG2 isotypes, but, in milk, only the concentration of IgG1 was significantly increased in the vaccinated cows during the lactation compared with the control cows.

Use of 51Cr release to measure the cytotoxic effects of staphylococcal leukocidin and toxin neutralization on bovine leukocytes

Leukocidin toxin from Staphylococcus aureus produces specific cytolytic effects on neutrophils and macrophages. The most commonly used method for determination of leukocidin activity is microscopic examination for characteristic morphological changes in toxin-treated cells. The 51Cr release assay was modified to allow quantitation of the cytolytic effects of leukocidin on bovine peripheral blood neutrophils and lymphocytes. Toxin neutralization by serum and milk samples was quantitated by this method. The neutralizing abilities of the various samples were found to correlate with the levels of immunoglobulin G (IgG1) specific for leukocidin. Undiluted normal serum samples, however, were capable of partially preventing the cytotoxic effects of leukocidin. The assay was shown to be an effective means of quantitating the cytotoxic activity of leukocidin on neutrophils as well as demonstrating neutralization of cytotoxicity by milk and serum samples.

Immunogenic properties of Staphylococcus aureus and Streptococcus agalactiae administered separately and in combination to lactating cows

Composite bacterins of Staphylococcus aureus and Streptococcus agalactiae, or either bacterin alone, were administered systemically to groups of lactating cows. The response to each bacterin was unaffected by the simultaneous administration of the antigens when assessed by comparing the antibody levels in milk by enzyme-linked immunosorbent assay. There was no evidence of cross reactivity of the antigens studied, nor immunopotentiation by either bacteria.

Comparative effect of selected adjuvants on the response in the bovine mammary gland to staphylococcal and streptococcal antigens

The effect of 4 adjuvants on the response in the lactating bovine mammary gland to an antigenic stimulus was examined. Fifty four lactating Holstein Friesian cows were randomly allocated to 6 groups. Four of these groups received a staphylococcal and streptococcal bacterin-toxoid vaccine administered systemically in association with an adjuvant preparation. The adjuvants used were: aluminum hydroxide gel, Freund's incomplete adjuvant, a metabolizable lipid emulsion and Bordetella pertussis. Two further groups serving as controls received saline, or the vaccine suspended in saline only. The immunoglobulin G response specific for each of 3 vaccine antigens, was monitored in the milk by means of enzyme-linked immunosorbent assay for a period of 23 weeks. The results indicated that high levels of antibody may be maintained in the milk, throughout the average lactation, if cows are vaccinated in the region of the supramammary lymph node with an optimum dose of antigen emulsified in Freund's incomplete adjuvant.