Synthesis of conjugated PIA-rSesC and immunological evaluation against biofilm-forming Staphylococcus epidermidis

Purpose. Staphylococcus epidermidis is an opportunistic pathogen and a leading cause of morbidity and premature mortality in patients with medical device-related infections, which is a concern in hospitalized patients. Developing a strategy to raise opsonic antibodies against polysaccharide intracellular adhesin (PIA) could be promising for the elimination of colonizing and biofilm-forming S. epidermidis. Following the purification of truncated rSesC protein and PIA, for the first time, PIA was conjugated to rSesC as a carrier to increase the immunogenicity of PIA and its efficacy in mice was evaluated. The structure of the conjugate was analysed using the Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy (H1-NMR) methods. Afterwards, the immune response was evaluated by measuring the total IgG, IgG2a and IgG2b titres. Results. The immunization of mice with the PIA-rSesC conjugate raised the levels of opsonic antibodies, and the vaccinated mice were protected when challenged intravenously by wild-type S. epidermidis strain 1457. Further studies indicated that the conjugated vaccine was able to eliminate S. epidermidis biofilm formation in in vitro or in vivo assays. Conclusion. This study confirms the proposal that the immunization of mice with PIA-rSesC conjugate vaccine could protect against S. epidermidis infection.