A core glycolipid vaccine elicits cross-reactive antibodies against Salmonella spp. and protects against invasive nontyphoidal Salmonella disease in mice

Abstract

Background Enteric fever caused by Salmonella enterica serovars Typhi and Paratyphi A in addition to gastroenteritis and invasive disease, predominantly attributable to nontyphoidal Salmonella serovars Typhimurium and Enteritidis, are major causes of death and disability across the globe. A broad-spectrum vaccine that protects against disease caused by typhoidal and nontyphoidal serovars of Salmonella is not available for humans but would prevent a considerable burden of disease worldwide. Methods We previously developed a broad-spectrum vaccine for Gram-negative bacteria that is based on the inner core domain of detoxified Escherichia coli O111, Rc (J5) mutant lipooligosaccharide, a highly conserved antigen across Gram-negative bacteria, complexed with an outer membrane protein of group B Neisseria meningitidis. In this study, mice and rabbits were immunized with the J5 core/outer membrane protein subunit vaccine. We assessed the cross-reactivity of antisera with various Salmonella species lipopolysaccharides and the protective efficacy of passive and active immunization with J5 vaccine against experimental nontyphoidal Salmonella infection in mice. Results Vaccination with J5 induced IgG responses that strongly recognized lipopolysaccharide from both typhoidal and nontyphoidal Salmonella and imparted a survival benefit against lethal heterologous challenges with S. Typhimurium and S. Enteritidis. Additionally, passive transfer studies with rabbit hyperimmune sera raised against the J5 vaccine revealed that anti-core antibodies were protective against lipopolysaccharide challenge in D-galactosamine-sensitized mice. Conclusions Our findings support the development of core glycolipids as a novel Salmonella vaccine candidate. Further investigation is warranted to determine the efficacy of the J5 core/outer membrane protein vaccine against other Salmonella serovars of concern.