Immunological response against Staphylococcus aureus bovine mastitis in heifers vaccinated with RC122 mutant strain

PELLEGRINO, M.; FROLA, I.; GIRAUDO J.; VIVAS, A.; RODRIGUEZ, N; BOGNI, C

Santiago de Chile

Congreso; XXVI World Buiatrics Congress; 2010

World Association for Buiatrics

Bovine Mastitis (BM) is an infectious disease with a strong economic impact in dairy farming. In Argentina, Staphylococcus aureus is the main infectious agent. Actually, the mains strategies to prevent BM are based on the control of the infection by reducing the entrance of pathogens to mammary gland. In a previous work, an avirulent mutant of S. aureus, RC122, was isolated and deeply characterized. The potentiality of this strain as immunogen in preventing BM was demonstrated by a three fold decrease on the infection probability of vaccinated heifers (VH) after challenge with the virulent parental strain. This finding was related to the significant increase of opsonic antibodies in blood and milk of VH. The aim of this work was to evaluate the efficacy of the RC122 strain on the lymphocytes proliferation, antibodies levels in calostrum and the role an IM dose on the protective effect. A vaccination scheme, including 3 subcutaneous (SC) doses (5x108cfu/ml) of the RC122 strain 30 d before and 30 d after pregnancy and 10 d before calving, were administrated to 6 heifers. Four animals were used as control. Twenty days after calving, one VH and one control heifer, were inoculated intramammary with 109 cfu/ml of heat killed avirulent mutant. Blood, milk and calostrum samples were taken before and after calving. The concentration of different isotypes of antibodies (total IgG, IgG1 and IgG2) was determined by ELISA. A blood lymphocyte antigen-specific proliferation assay was performed to determine the cellular immune response stimulated by the S. aureus RC122.This assay was based on cell thymidine [Methyl-3H] incorporation due to cell proliferation. The proliferative response was calculated as a stimulation index (SI).Results showed that the antibodies founded in blood and milk of VH were not enhanced by the IM dose administration. This might indicate that 3 SC doses before calving would be effective to stimulate antibody production on milk and calostrum. A significant increase in the SI was founded in VH compared with the control animals before and after calving. Moreover, according to immunological determinations it can be inferred that immunization with RC122 strain induces a clonal expansion of B lymphocytes, isotypes change on IgGs and differentiation and affinity maturation of B memory lymphocytes.These results allowed concluding that the proposed vaccination scheme can induce a humoral and cellular immunological response.