Evaluation of PLGA nanoparticle-based conjugate vaccines incorporating lipopolysaccharide and alginate for inducing immunity against <i>P. aeruginosa</i> : a rabbit model study

A common Gram-negative bacterium, <i>Pseudomonas aeruginosa</i> poses a special risk to people with compromised immune systems, including those receiving chemotherapy, organ transplant recipients, and people with cystic fibrosis. The purpose of this study was to use PLGA nanoparticles conjugated with lipopolysaccharide (LPS) and alginate antigens to create an efficient nanovaccine against <i>P. aeruginosa</i>. The mass culture of <i>P. aeruginosa</i> was prepared and its lipopolysaccharide as well as its polysaccharide capsule (alginate) were extracted, purified and conjugated with PLGA NPs. Using a zeta sizer, Fourier-transform infrared spectroscopy, and atomic force microscopy, the conjugation process was verified. Then, vaccination was administered in two ways of intramuscular and intranasal to 48 New Zealand white male rabbits (each trial 24). The blood sampling was performed from marginal ear vein of the rabbits two weeks after the last administration to carry out the antibody titration and opsonophagocytosis assay. Then, to check the immunogenicity, the rabbits were challenged by injecting a direct dose of <i>P. aeruginosa</i>. In general, LPS-PLGA conjugate produced significantly higher immunogenicity compared to ALG-PLGA conjugate, pure antigens, and PLGA NPs in both ways of administration. It was also found that vaccination by intramuscular injection causes better immunity compared to intranasal vaccination.