Inactivation of the htps A gene affects capsule development and pathogenicity of Streptococcus suis .

Streptococcus suis serotype 2 (S. suis2) is an important swine pathogen and also an emerging zoonotic agent. HtpsA has been reported as an immunogenic cell surface protein on the bacterium. In the present study, we constructed an isogenic mutant strain ofhtpsA, namely Delta htpsA, to study its role in the development and virulence ofS. suis2. Our results showed that the mutant strain lost its typical encapsulated structure with decreased concentrations of sialic acid. Furthermore, the survival rate in whole blood, the anti-phagocytosis by RAW264.7 murine macrophage, and the adherence ability to HEp-2 cells were all significantly affected in the Delta htpsA. In addition, the deletion ofhtpsA sharply attenuated the virulence ofS. suis2 in an infection model of mouse. RNA-seq analysis revealed that 126 genes were differentially expressed between the Delta htpsA and the wild-type strains, including 28 upregulated and 98 downregulated genes. Among the downregulated genes, many were involved in carbohydrate metabolism and synthesis of virulence-associated factors. Taken together,htpsA was demonstrated to play a role in the morphological development and pathogenesis of the highly virulentS. suis2 05ZYH33 strain.