Invasive African Salmonella Typhimurium induces bactericidal antibodies against O-antigens

•Invasive endemic Typhimurium D23580 induced bactericidal anti-OAg antibody response.•D23580 mutants lacking OAg did not elicit bactericidal antibodies.•Purified anti-D23580 OAg antibody was bactericidal when added to human serum.•Results support the development of OAg-based vaccine against invasive NTS in Africa.

Nontyphoidal Salmonella are a major and emerging cause of fatal invasive disease in Africa, and are genetically distinct from those found elsewhere in the world. Understanding the targets of protective immunity to these African Salmonellae is key to vaccine development. We immunized mice and rabbits with heat-inactivated wild-type African invasive Salmonella Typhimurium D23580 and rough mutants lacking O-antigen. Wild-type Salmonella, unlike rough bacteria, induced a large bactericidal antibody response mainly against O-antigen. Bactericidal ability of anti-O-antigen antibodies was confirmed following purification by affinity chromatography. The current findings support the development of an O-antigen conjugate vaccine against invasive nontyphoidal Salmonellae for Africa.