Adjuvanted Vaccine Induces Functional Antibodies against Pseudomonas aeruginosa Filamentous Bacteriophages

Pseudomonas aeruginosa (Pa), a WHO priority 1 pathogen, resulted in approximately 559,000 deaths globally in 2019. Pa has a multitude of host-immune evasion strategies that enhance Pa virulence. Most clinical isolates of Pa are infected by a phage called Pf that has the ability to misdirect the host-immune response and provide structural integrity to biofilms. Previous studies demonstrate that vaccination against the coat protein (CoaB) of Pf4 virions can assist in the clearance of Pa from the dorsal wound model in mice. Here, a consensus peptide was derived from CoaB and conjugated to cross-reacting material 197 (CRM197). This conjugate was adjuvanted with a novel synthetic Toll-like receptor agonist (TLR) 4 agonist, INI-2002, and used to vaccinate mice. Mice vaccinated with CoaB-CRM conjugate and INI-2002 developed high anti-CoaB peptide-specific IgG antibody titers. Direct binding of the peptide-specific antibodies to whole-phage virus particles was demonstrated by ELISA. Furthermore, a functional assay demonstrated that antibodies generated from vaccinated mice disrupted the replicative cycle of Pf phages. The use of an adjuvanted phage vaccine targeting Pa is an innovative vaccine strategy with the potential to become a new tool targeting multi-drug-resistant Pa infections in high-risk populations.