title: Intramammary Immunization of Pregnant Mice with Staphylococcal Protein A Reduces the Post-Challenge Mammary Gland Bacterial Load but Not Pathology.
abstract: Protein A, encoded by the spa gene, is one of the major immune evading MSCRAMM of S. aureus, demonstrated to be prevalent in a significant percentage of clinical bovine mastitis isolates in Australia. Given its' reported significance in biofilm formation and the superior performance of S. aureus biofilm versus planktonic vaccine in the mouse mastitis model, it was of interest to determine the immunogenicity and protective potential of Protein A as a potential vaccine candidate against bovine mastitis using the mouse mastitis model. Pregnant Balb/c mice were immunised with Protein A emulsified in an alum-based adjuvant by subcutaneous (s/c) or intramammary (i/mam) routes. While humoral immune response of mice post-immunization were determined using indirect ELISA, cell-mediated immune response was assessed by estimation of interferon-gamma (IFN-γ) produced by protein A-stimulated splenocyte supernatants. Protective potential of Protein A against experimental mastitis was determined by challenge of immunized versus sham-vaccinated mice by i/mam route, based upon manifestation of clinical symptoms, total bacterial load and histopathological damage to mammary glands. Significantly (p<0.05) higher levels of IgG1 isotype were produced in mice immunized by the s/c route. In contrast, significantly higher levels of the antibody isotype IgG2a were produced in mice immunized by the i/mam route (p<0.05). There was significant reduction (p<0.05) in bacterial loads of the mammary glands of mice immunized by Protein A regardless of the route of immunization, with medium level of clinical symptoms observed up to day 3 post-challenge. However, Protein A vaccine failed to protect immunized mice post-challenge with biofilm producing encapsulated S. aureus via i/mam route, regardless of the route of immunization, as measured by the level of mammary tissue damage. It was concluded that, Protein A in its' native state was apparently not a suitable candidate for inclusion in a cell-free vaccine formulation against mastitis.
authors: Curtin Health Innovation Research Institute, Curtin University, Bentley, Perth, Western Australia, 6102, Australia.|College of Veterinary Sciences and Animal Husbandry, Central Agricultural University, Selesih, Aizawl, Mizoram, 796014, India.
authors: Jully
authors: J
authors: Gogoi-Tiwari
authors: Curtin Health Innovation Research Institute, Curtin University, Bentley, Perth, Western Australia, 6102, Australia.
authors: Vincent
authors: V
authors: Williams
authors: Curtin Health Innovation Research Institute, Curtin University, Bentley, Perth, Western Australia, 6102, Australia.|Department of Medicine and Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY, 10461, United States of America.
authors: Charlene Babra
authors: CB
authors: Waryah
authors: Curtin Health Innovation Research Institute, Curtin University, Bentley, Perth, Western Australia, 6102, Australia.
authors: Sangeetha
authors: S
authors: Mathavan
authors: School of Veterinary and Life Sciences, Murdoch University, Murdoch, Perth, Western Australia, 6150, Australia.
authors: Harish Kumar
authors: HK
authors: Tiwari
authors: Curtin Health Innovation Research Institute, Curtin University, Bentley, Perth, Western Australia, 6102, Australia.
authors: Paul
authors: P
authors: Costantino
authors: Curtin Health Innovation Research Institute, Curtin University, Bentley, Perth, Western Australia, 6102, Australia.
authors: Trilochan
authors: T
authors: Mukkur
mesh_terms: D000818:Animals; D058491:Bacterial Load; D001428:Bacterial Vaccines / Q000276:immunology*; D018441:Biofilms; D003208:Concanavalin A / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D007114:Immunization; D007074:Immunoglobulin G / Q000276:immunology; D007279:Injections, Subcutaneous; D007371:Interferon-gamma / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000276:immunology* / Q000382:microbiology*; D008413:Mastitis / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D011247:Pregnancy; D013154:Spleen / Q000166:cytology; D013205:Staphylococcal Protein A / Q000276:immunology*
chemical_list: D001428:Bacterial Vaccines; D007074:Immunoglobulin G; D013205:Staphylococcal Protein A; D003208:Concanavalin A; D007371:Interferon-gamma