Vaccine development for the prevention of staphylococcal mastitis in dairy cows

Staphylococci are the most common and costly mammary disease of dairy cattle worldwide. Target of RNAIII Activating Protein (TRAP), a membrane associated 167AA protein, is highly conserved among staphylococci and was shown in Staphylococcus aureus to be involved in bacterial stress response. The aims of this study were to test the safety and efficacy of recombinant TRAP (rTRAP) vaccine in dairy animals. The vaccine was safe as 2–3 subcutaneous injections of rTRAP (54–100 μg) with adjuvant ISA 206 to cows and goats did not lead to any abnormal symptoms of sensitivity to the vaccine. The rTRAP vaccine was immunogenic and caused the induction of a humoral immune response that remained high for at least 160 d post second immunization. The rTRAP vaccine was efficacious; at parturition only 13.5% (5/37) heifers in the immunized group were infected with Staphylococcus chromogenes as compared to 42.9% (18/42) in the non-immunized group. Additionally, when cows were immunized in mid-lactation, the difference between somatic cell count (SCC) in immunized and control animals was profound (45 ± 7 vs. 470 ± 194, respectively). At the same time, the difference in milk yield was also evident (48.3 ± 1.4 L d−1 vs. 44.3 ± 0.9 L d−1, respectively). Put together, these studies indicate the value of the rTRAP vaccine in preventing new udder infections by staphylococci, which significantly lead to lowered SCC and some increase in milk yield. TRAP is conserved among all strains and species and is constitutively expressed in any strain of S. aureus or CNS tested so far, including those isolated from cows. TRAP may thus serve as a universal anti-staphylococcus vaccine.