Comparison of Staphylococcus aureus surface protein extraction methods and immunogenicity

Reta Duguma Abdi; John R Dunlap; Barbara E Gillespie; Desta Beyene Ensermu; Raul Antonio Almeida; Oudessa Kerro Dego

doi:10.1016/j.heliyon.2019.e02528

Comparison of Staphylococcus aureus surface protein extraction methods and immunogenicity

Heliyon. 2019 Oct 23;5(10):e02528. doi: 10.1016/j.heliyon.2019.e02528. eCollection 2019 Oct.

Authors

Reta Duguma Abdi^{1

2}, John R Dunlap³, Barbara E Gillespie¹, Desta Beyene Ensermu¹, Raul Antonio Almeida¹, Oudessa Kerro Dego¹

Affiliations

¹ Department of Animal Science, The University of Tennessee, Knoxville, TN37966, United States.
² Department of Veterinary Biomedical Sciences, College of Veterinary Medicine, Long Island University, Greenvale, NY11548, United States.
³ Joint Institute for Advanced Materials (JIAM) Microscopy Center and Advanced Microscopy and Imaging Center, The University of Tennessee, Knoxville, TN, 37996, United States.

Abstract

Staphylococcus aureus is the major contagious bovine mastitis pathogen and has no effective vaccine. Strain variation and limited knowledge of common immunogenic antigen/s are among major constraints for developing effective vaccines. S. aureus cell surface proteins that are exposed to the host immune system constitute good vaccine candidates. The objective of this study was to compare two novel S. aureus surface protein extraction methods with biotinylation method and evaluate immune-reactivity of extracted proteins. Surface proteins were extracted from nine genetically distinct S. aureus strains from cases of bovine mastitis. After extraction, bacterial cell integrity was examined by Gram staining and electron microscopy to determine if extraction methods caused damage to cells that may release non-surface proteins. The extracted proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and evaluated for immune-reactivity using western blot. Results showed that all three extraction methods provided multiple protein bands on SDS-PAGE. Western blot result showed several immunoreactive surface proteins, in which some proteins strongly (well-resolved, thick, dark, and intense band) reacted across the nine strains tested. The three methods are valid for the extraction of surface proteins and hexadecane, and cholic acid methods are more feasible than biotinylation since both are easier, cheaper, and have minor effects on the bacterial cell. Strongly immune-reactive surface proteins may serve as potential candidates for a vaccine to control S. aureus mastitis in dairy cows.

Keywords: Bovine mastitis; Extraction; Immune-reactive; Immunology; Infectious disease; Microbiology; Staphylococcus aureus; Surface protein; Vaccines; Veterinary medicine.