Preclinical Immunogenicity and Efficacy of Optimized O25b O-Antigen Glycoconjugates To Prevent MDR ST131 E. coli Infections
Laurent Chorro, Zheng-Hui Li, Ling Chu, Suddham Singh, Jianxin Gu, Jin Hwan Kim, Kaushik Dutta, Rosalind Pan, Srinivas Kodali, Duston Ndreu, Axay Patel, Julio C. Hawkins, Chris Ponce, Natalie Silmon de Monerri, David Keeney, Arthur Illenberger, C Hal Jones, Lubomira Andrew, Jason Lotvin, A. Krishna Prasad, Isis Kanevsky, Kathrin U. Jansen, Annaliesa S. Anderson, Robert G. K. Donald
Abstract
carrier protein cross-linking (single-end versus cross-linked "lattice") and conjugation chemistry (reductive amination chemistry in dimethyl sulfoxide [RAC/DMSO] versus ((2-((2-oxoethyl)thio)ethyl)carbamate [eTEC] linker). Using opsonophagocytic assays (OPAs) to measure serum functional antibody responses to vaccination, we observed that higher-molecular-mass O25b long-chain lattice conjugates showed improved immunogenicity in mice compared with long- or short-chain O antigens conjugated via single-end attachment. The lattice conjugates protected mice from lethal challenge with acapsular O25b ST131 strains as well as against hypervirulent O25b isolates expressing K5 or K100 capsular polysaccharides. A single 1-μg dose of long-chain O25b lattice conjugate constructed with both chemistries also elicited robust serum IgG and OPA responses in cynomolgus macaques. Our findings show that key properties of the O-antigen carrier protein conjugate such as saccharide epitope density and degree of intermolecular cross-linking can significantly enhance functional immunogenicity.