Pseudomonas aeruginosa is an opportunistic pathogen that causes serious infections, is usually resistant to antimicrobial agents, and is the leading cause of morbidity and premature mortality in patients with cystic fibrosis (CF). Mucoid strains of P. aeruginosa produce a virulence factor known as alginate. Developing a strategy to raise opsonic antibodies against alginate could be promising for the treatment of P. aeruginosa infection in CF patients. Conjugation of alginate to a carrier protein is a good method for increasing the immunogenicity of alginate. We conjugated alginate to the outer membrane vesicle (OMV) of Neisseria meningitidis serogroup B, which is a safe carrier protein, and evaluated its efficacy in mice. To evaluate the immune response, total IgG, IgG1, IgG2a, and IgG2b titers were analyzed. Immunization of mice with the alginate-OMV conjugate raised the levels of opsonic antibodies, and the vaccinated mice were protected when challenged intranasally with P. aeruginosa. Further studies showed that the conjugated vaccine could eliminate P. aeruginosa from the lungs of infected mice. This study supports the proposal that immunization of mice with an alginate-OMV conjugate vaccine could be safe and protective against P. aeruginosa infection.

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Introduction: Biofilm forming Staphylococcus epidermidis is a main causative agent of infections related to medical devices. Purification and evaluation of Gly-TA polysaccharide from a biofilm-forming S. epidermidis as a putative vaccine candidate were the main goals of the current study. Methods: Taking advantage of size exclusion chromatography procedure, glycerol teichoic acid (Gly-TA) was purified from the above-mentioned strain and biochemical analyses including, Fourier Transform Infrared spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance spectroscopy (H1-NMR) were conducted for the recovered polysaccharide. Results: Following PCR confirmation of a S. epidermidis strain, Gly-TA was extracted and its biochemical compositions (i.e. N-acetyl glucose amine residues) were obtained. Conclusion: It is envisaged that Gly-TA polysaccharide could be considered as a putative vaccine to inhibit formation of biofilm by S. epidermidis.