Preparation of Pseudomonas aeruginosa alginate-flagellin immunoconjugate

Mucoid strains of Pseudomonas aeruginosa are closely associated with chronic pulmonary infections. In this report we describe a straightforward approach to conjugate high molecular weight alginate to type b-flagellin (FLB) and investigation of its bioactivity. The conjugation process was performed by using ADH and EDAC. The endotoxin was eliminated from the candidate vaccine by LPS removal resin followed by LAL test. The bioconjugate molecules were verified by simultaneously determination of polysaccharide/protein content followed by gel filtration chromatography and FTIR spectroscopy. Groups of eight BALB/c mice were injected intranasally with 5 μg (per each nostril) of purified alginate, FLB and conjugated alginate-FLB with two week intervals. The functional activity of the vaccine was evaluated by ELISA and opsonophagocytosis tests. Vaccination with the alginate-FLB conjugate induced a significant (P = 0.0033) rise in alginate specific IgG in mice. At all dilution ranges, the opsonic activity of the conjugate vaccine antisera was significantly higher than alginate alone (61.9% vs. 17.3% at 1:4 dilution; P = 0.0067). The alginate-FLB conjugate could elicit high specific antibodies titer against alginate by improving its immunogenicity. In addition, the antisera raised against conjugate vaccine act as a suitable opsonin for phagocytosis of the mucoid strains of P. aeruginosa.