Efficacy of immunization with a recombinant S. aureus vaccine formulated with liposomes and ODN-CpG against natural S. aureus intramammary infections in heifers and cows.

The aims of the present study were to evaluate the ability of a subunit vaccine composed of recombinant molecules of α-toxin, ß-toxin, FnBPA and ClfA, formulated with cationic liposomes and CpG-ODN, to confer protection against natural S. aureus intramammary infection (IMI) and to assess the antibody response against the vaccine components. A stringent criterion based on molecular identification of the isolates was used to define IMI. The proportion of animals that developed new S. aureus IMI was higher in the Control group compared with the Vaccine group (reduction of 60.7%), and time to new S. aureus IMI was higher for animals in the Vaccine group compared with animals in the Control group, although not statistically significant. Molecular identification of the isolates allowed the detection of S. aureus pulsotypes that appeared transiently in milk and others that were able to establish IMI, providing a new perspective to define parameters related to the definition of new IMI and cures. Specific IgG, IgG1 and IgG2 levels against the four recombinant proteins included in the vaccine were significantly increased in the vaccinated group and the recombinant α-toxin included in the vaccine generated antibodies that reduced significantly the haemolytic activity of native α-toxin. Data reported in the present study indicate a possible effect on both the proportion of animals developing new IMI and the time to new S. aureus IMI, but the incidence of disease within the study was too low to provide statistical confirmation.

Immune response and functional role of antibodies raised in heifers against a Staphylococcus aureus CP5 lysate and recombinant antigens vaccine formulated with Iscom Matrix adjuvant.

Staphylococcus aureus is the most frequently isolated pathogen from bovine intramammary infections worldwide. Commercially available vaccines for mastitis control are composed either of S. aureus lysates or inactivated whole-cells formulated with traditional adjuvants. We recently showed the ability of a S. aureus CP5 lysate vaccine adjuvanted with Iscom Matrix to generate a longer lasting specific antibody response in blood and milk, with improved opsonic capacity, compared with a S. aureus CP5 whole-cell formulation. The aim of the present study was to obtain an experimental immunogen composed of lysed cells of a CP5 S. aureus strain supplemented with recombinant clumping factor A, fibronectin binding protein A and ß-toxin formulated with Iscom Matrix, characterize the immune response generated when immunizing pregnant heifers and assess the functional role of antibodies raised against this immunogen in experimental models. Both a lysate vaccine and a lysate+recombinant antigens vaccine elicited antibodies that promoted neutrophil phagocytosis and inhibited internalization into mammary epithelial cells, in vitro. Incorporation of defined antigenic molecules to the lysate formulation elicited a strong specific humoral immune response against both lysate and recombinant antigens and was associated with higher expression of regulatory and pro-inflammatory cytokines. In addition, antibodies were efficient for blocking S. aureus binding to bovine fibrinogen and fibronectin, and neutralizing ß-toxin effect in vitro, placing these antigens as candidates to be included in a formulation directed to prevent staphylococcal bovine mastitis.