Immunological response to an experimental intramammary inoculation with a killed Staphylococcus aureus strain in vaccinated and non-vaccinated lactating dairy cows

Abstract

The objective of this study was to unravel the innate immunological response after administration of a novel vaccine (Startvac®, HIPRA, S.A., Amer, Spain), containing the inactivated Escherichia coli J5 strain and the Staphylococcus aureus SP 140 strain expressing Slime Associated Antigenic Complex (SAAC). In a challenge trial, the effect of vaccination on milk neutrophil viability and concentration as well as on the antigen-specific antibodies anti-SAAC and anti-J5 was determined and several clinical parameters were observed. Eight animals were included of which four were immunized at 45 days before the expected calving date followed by a second vaccination 35 days later. The other four cows serve as non-vaccinated controls. Fifteen days after calving, two contralateral quarters of each cow were inoculated with an inactive S. aureus isolate. Phosphate buffered saline was administered to the two control quarters. Blood samples are collected at 45 and 10 days before calving as well as at 15 days after calving just before the infection is induced. Quarter of each cow were inoculated with an inactive S. aureus isolate. Phosphate buffered saline was administered to the two control quarters. Blood samples are collected at 45 and 10 days before calving as well as at 15 days after calving just before the infection is induced. Quarter milk samples are collected at 2 hours before, and at 4, 12, 24 and 48 hours after challenge. During the entire trial bacteriological culture and somatic cell count of the milk of all four quarters was frequently evaluated, this to exclude interference with naturally occurring intramammary infections. In conclusion, vaccinated cows seem to develop a less severe inflammatory reaction after inoculation compared to non-vaccinated animals. Vaccination also increased the level of the antigenspecific antibodies anti-SAAC and anti-J5 in blood which might eventually result in a shorter duration of the infection. However, further research is definitely needed before final conclusions on the impact of prepartum vaccination on the cows' innate immune response and their udder health status shortly after calving can be drawn.