Efficacy of novel staphylococcal surface associated protein vaccines against Staphylococcus aureus and non-aureus staphylococcal mastitis in dairy cows

Authors: VIDLUND, JESSICA - University Of Tennessee; GELALCHA, BENTI - University Of Tennessee; GILLESPIE, BARBARA - University Of Tennessee; Agga, Getahun; SCHNEIDER, LIESEL - University Of Tennessee; SWANSON, STEPHANIE - University Of Tennessee; FRADY, KINSLEY - University Of Tennessee; KERRO DEGO, OUDESSA - University Of Tennessee

Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2024
Publication Date: 1/27/2024
Citation: Vidlund, J., Gelalcha, B.D., Gillespie, B.E., Agga, G.E., Schneider, L., Swanson, S.M., Frady, K.D., Kerro Dego, O. 2024. Efficacy of novel staphylococcal surface associated protein vaccines against Staphylococcus aureus and non-aureus staphylococcal mastitis in dairy cows. Vaccine. https://doi.org/10.1016/j.vaccine.2024.01.067.
DOI: https://doi.org/10.1016/j.vaccine.2024.01.067

Interpretive Summary: Mastitis is the most economically devastating disease of dairy cattle, usually caused by bacterial infection of the udder. Staphylococcus is the most common bacteria that cause mastitis in dairy cows. Current staphylococcal mastitis control programs are not fully effective, and antibiotics are not sustainable because of limited success and the emergence of antimicrobial resistant bacteria. An effective vaccine that prevents clinical disease and production losses is critically needed. We developed staphylococcal surface associated proteins vaccines and evaluated their protective effects by experimental vaccination and challenge studies in dairy cows. Our results showed that these vaccines induced increased vaccine-specific antibody titers in sera and milk and conferred reduction of the incidence of staphylococcal mastitis over 300 days of lactation.

Technical Abstract: Mastitis is an inflammation of the mammary gland commonly caused by bacteria or fungi. Staphylococcus aureus is a major bacterium that causes mastitis in dairy cows. Non-aureus staphylococci are also increasingly reported, with Staphylococcus chromogenes being the most common species. Current staphylococcal mastitis control programs are not fully effective, and treatment with antibiotics is not sustainable. Non-antibiotic sustainable control tools, such as effective vaccines, are critically needed. We previously developed S. aureus surface-associated proteins (SASP) and S. chromogenes surface-associated proteins (SCSP) vaccines that conferred partial protective effects. We hypothesized that vaccination with SASP or SCSP would reduce the incidence of S. aureus mastitis throughout the lactation period. The objective of this study was to evaluate the efficacy of SASP and SCSP vaccines against S. aureus and non-aureus staphylococcal mastitis under natural exposure over 300 days of lactation. Pregnant Holstein dairy cows (n = 45) were enrolled and assigned to receive SASP (n = 15) or SCSP (n = 16) vaccines or unvaccinated control (n = 14). Cows were vaccinated with 1.2 mg of SASP or SCSP with Emulsigen-D adjuvant. Control cows were injected with phosphate-buffered saline with Emulsigen-D adjuvant. Three vaccine injections were given subcutaneously at 60, 40, and 20 days before the expected calving. Booster vaccinations were given at 120 and 240 days in milk. Cows were monitored for mastitis at quarter and cow levels, staphylococcal mastitis incidence, changes in serum and milk anti-SASP and anti-SCSP antibody titers, bacterial counts in milk, adverse reactions, milk yield and milk somatic cells count over 300 days of lactation. The SCSP vaccine conferred a significant reduction in the incidence of staphylococcal mastitis. Milk and serum anti-SASP and anti-SCSP antibody titers were increased in the vaccinated cows compared to unvaccinated control cows. Anti-SASP and anti-SCSP antibody titers decreased at about 120 days in milk, indicating the duration of immunity of about four months. In conclusion, the SASP and SCSP vaccines conferred partial protection from natural infection.