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

PUJATO, N.; CAMUSSONE, C.M.; RENNA, M.S.; PERRIG, M.S.; MOREIN, B.; CALVINHO, L.F.; MARCIPAR, I.S.

The Veterinary Journal

ELSEVIER SCI LTD

Año: 2018 vol. 235 p. 47 - 53

1090-0233

Staphylococcus aureus is a worldwide pathogen that causes mastitis in dairy herds. Shortcomings incontrol programs have encouraged the development of vaccines against this pathogen. This studyevaluated 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 immunestimulatingcomplex. Comparisons were made between healthy pregnant heifers that received eitherVacR (n = 8; VacR group) or phosphate buffered saline (PBS) plus adjuvant (control group) SC in thesupramammary lymph node area on days 45 and 15 before the expected calving date. Blood and foremilksamples were collected from 7 to 60 days post-calving.After calving, heifers in the VacR group produced higher total IgG (IgGtotal) titers against eachcomponent, in both serum (rBt, 3.4105; rClf, 3.1105; rFnBP, 2.3105) and milk (rBt, 2.6104; rClf,1.3104; rFnBP, 1.1104), than control heifers (P < 0.0001). There were increased concentrations of IgG1and IgG2 in VacR group (P < 0.05), in both serum and milk. Humoral responses remained high throughoutthe period most susceptible to intramammary infections (P < 0.01). Antibodies produced against S. aureusrClf and rFnBP reduced bacterial adherence tofibronectin andfibrinogen by 73% and 67%, respectively(P < 0.001). Milk antibodies against these adhesins inhibited S. aureus invasion of a mammary epithelialcell 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 controlgroup (P < 0.0001) and a significantly increase in the proportion of positive neutrophils (VacR, 29.7%; PBS,13.1%) and the meanfluorescent index (VacR, 217.4; PBS, 152.6; P < 0.01) in the VacR group. The resultssuggest that VacR is a valuable vaccine candidate against S. aureus infections, and merits furtherfieldtrials and experimental challenges.