Genotypic and phenotypic detection of capsular polysaccharides in Staphylococcus aureus isolated from bovine intramammary infections in Argentina.

Staphylococcus aureus (n=157) isolated from intramammary infections in Argentine dairy areas were evaluated for presence of cap5 and cap8 loci. Isolates carrying cap5 and cap8 were serotyped using specific antisera. Sixty four percent of the isolates were genotyped as cap5 or cap8 and 50% of them expressed CP5 or 8.

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.

Evaluation of the humoral immune response to a multicomponent recombinant vaccine against S. aureus in healthy pregnant heifers.

Staphylococcus aureus is a worldwide pathogen that causes mastitis in dairy herds. Shortcomings in control programs have encouraged the development of vaccines against this pathogen. This study evaluated the vaccine candidate VacR, which included recombinant S. aureus protein clumping factor A (rClf), fibronectin binding protein A (rFnBP) and hemolysin beta (rBt), formulated with a novel immune-stimulating complex. Comparisons were made between healthy pregnant heifers that received either VacR (n=8; VacR group) or phosphate buffered saline (PBS) plus adjuvant (control group) SC in the supramammary lymph node area on days 45 and 15 before the expected calving date. Blood and foremilk samples were collected from 7 to 60days post-calving. After calving, heifers in the VacR group produced higher total IgG (IgGtotal) titers against each component, in both serum (rBt, 3.4×105; rClf, 3.1×105; rFnBP, 2.3×105) and milk (rBt, 2.6×104; rClf, 1.3×104; rFnBP, 1.1×104), than control heifers (P<0.0001). There were increased concentrations of IgG1 and IgG2 in VacR group (P<0.05), in both serum and milk. Humoral responses remained high throughout the period most susceptible to intramammary infections (P<0.01). Antibodies produced against S. aureus rClf and rFnBP reduced bacterial adherence to fibronectin and fibrinogen by 73% and 67%, respectively (P<0.001). Milk antibodies against these adhesins inhibited S. aureus invasion of a mammary epithelial cell line (MAC-T), resulting in 15.7% of bacteria internalized (P<0.0001). There was an approximately 6-fold reduction in the hemolysis titer for the native hemolysin in the VacR group compared to the control group (P<0.0001) and a significantly increase in the proportion of positive neutrophils (VacR, 29.7%; PBS, 13.1%) and the mean fluorescent index (VacR, 217.4; PBS, 152.6; P<0.01) in the VacR group. The results suggest that VacR is a valuable vaccine candidate against S. aureus infections, and merits further field trials and experimental challenges.

Which are important targets in development of S. aureus mastitis vaccine?

Staphylococcus aureus represents one of the leading causes of mastitis in dairy cows worldwide. S. aureus IMI have variable outcomes due to virulence of the strain involved, immune defenses of the host, and by antibiotic resistance. The difficulty in eradication and the increasing concerns on antibiotics usages underscore the interest in developing new tools to control S. aureus mastitis. Vaccination represents one of the most studied of these tools but, so far, no vaccine seems to provide reliable protection. This review summarizes current knowledge on the major vaccine targets, including surface proteins, capsular polysaccharides, biofilm, and toxins. Finally, the present status of vaccination against S. aureus and the future of vaccine design were discussed, including how differences among in vivo models may influence vaccines development.

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.

Genotypic and phenotypic detection of capsular polysaccharides in Staphylococcus aureus isolated from bovine intramammary infections in Argentina

Staphylococcus aureus (n=157) isolated from intramammary infections in Argentine dairy areas were evaluated for presence of cap5 and cap8 loci. Isolates carrying cap5 and cap8 were serotyped using specific antisera. Sixty four percent of the isolates were genotyped as cap5 or cap8 and 50% of them expressed CP5 or 8.