A TonB dependent transporter YncD of Salmonella enterica Serovar Typhi is associated with iron acquisition and possesses vaccine potential

Abstract

Abstract Background Multiple TonB dependent transporters (TBDTs) contribute to bacterial virulence because of the importance roles that their substrates play in bacterial growth, and possess vaccine potential. A putative TBDT, YncD, had been identified as one of in vivo induced antigens during human infection of typhoid fever, and is involved in the pathogenicity of Salmonella enterica Serovar Typhi. The present study was aimed to determine the function and immunogenicity of YncD. Methods Homologous recombination method was used to construct an yncD-deletion mutant and cirA-iroN-fepA-deletion mutant from the wild-type S. Typhi Ty2. The growth of mutants and the wild-type strain were assessed in iron-deficient medium, as well as in human macrophage cells. Recombinant YncD protein was expressed and purified using Ni-NTA affinity chromatography and anion exchange. A mouse model was the used to evaluate the immunogenicity and protection efficacy of the recombinant YncD. Results Our results showed that YncD is associated with the iron-uptake of S. Typhi. The yncD-deletion mutant displayed impaired growth in the iron-deficient medium, comparable to that the cirA-iroN-fepA-deletion mutant did. The mutation of yncD also markedly decreased bacterial growth within human macrophage cells. Moreover, subcutaneous immunization of mice with the recombinant YncD elicited high levels of specific anti-YncD IgG, which protected the immunized mice against the intraperitoneal challenge of S. Typhi, and decreased bacterial burdens in the livers and spleens of the infected mice. Conclusion Our results showed that YncD is involved in the iron-uptake of S. Typhi and possesses immunogenicity.