Multicomponent vaccines for Pseudomonas aeruginosa

Boston Children'S Hospital, Boston MA

Investigators

Abstract

The goal of Research Project 2 in “Immunization against Multidrug-resistant Pathogens: Activating T Cell Immunity” Center of Excellence for Translational Research (IMPACT-CETR) is to develop a multicomponent Pseudomonas aeruginosa MAPS vaccine based on the serotype-independent P. aeruginosa biofilm polysaccharide Psl and its critical lipid epitope, combined with conserved protein antigens including the Th17- eliciting antigen PopB. Hospital-acquired P. aeruginosa respiratory infections are a significant threat, due in part to their prevalence, increasing rates of antibiotic resistance, and the relative dearth of new antibiotics in the development pipeline. Vaccine strategies to elicit opsonophagocytic killing (OPK) antibodies to the bacterial lipopolysaccharide or surface proteins have had varied success, but none has been broadly protective or FDA- approved for human use. This team showed that Th17 cells (CD4 helper T cells secreting the cytokine IL-17) confer antibody-independent protection against P. aeruginosa in mouse models of pneumonia, including a neutropenic model. Intranasal vaccination with the P. aeruginosa protein PopB mixed with the Th17 adjuvant curdlan stimulates protective Th17 responses in mice. Adding the OprF/I fusion protein to PopB improves protective efficacy against pneumonia in mice, and PopB induces IL-17 secretion in human whole blood taken after P. aeruginosa infection. A vaccine containing the biofilm polysaccharide Psl was constructed using the Multiple Antigen-Presenting System (MAPS) platform, which links biotinylated Psl with a pneumococcal carrier protein fused to the avidin homolog rhizavidin. This candidate elicits OPK antibodies to Psl after active immunization in rabbits and passive immunization in mice; a recently described critical lipid epitope on Psl is retained and immunogenic. A MAPS vaccine containing PopB induces high Th17 responses after subcutaneous immunization of mice with alum as adjuvant. The hypotheses of this project are that: 1) site-selective coupling of vaccine protein antigens to Psl using MAPS will optimize immune responses to T and B cell epitopes; and 2) combining PopB with antigens that induce protective antibodies (Psl, the type 3 secretion system protein PcrV, and the OprF/I fusion protein) will improve the protective efficacy of PopB both in potency and in broadness of protection, with pulmonary tissue-resident memory (TRM) Th17 cells being critical for maximal protection against pneumonia. Aim 1 is to use MAPS to select the optimal combination and composition of vaccine antigens and adjuvants, and test naturally occurring vs synthetic Psl, both linked to PopB-containing fusion proteins. Studies will measure protective efficacy in mice for mucosal and systemic antibodies and T-cell responses. Aim 2 will identify mechanisms of protection using immunophenotyping and single-cell transcriptomics in transgenic mice deficient in antibody and Th17 responses. Aim 3 will test the immunogenicity of the lead vaccine candidate in nonhuman primates. Successful completion of this project will provide preclinical data to support the advancement of this vaccine to future Phase 1 clinical studies.