Thioredoxin reductase contributes to stress response and pathogenicity of Streptococcus suis type 2

Abstract:

[Background] The thioredoxin reductase (TRR), one of the key components in the thioredoxin system, plays a key role in the oxidative stress response, homeostasis, and infection of pathogens.[Objective] To examine the role of TRR in the infection of Streptococcus suis type 2 (SS2), a zoonotic pathogen. [Methods] The trr-deleted mutant (Δtrr) and complementation strain (cΔtrr) of SS2 were constructed by homologous recombination on the basis of the wild-type (WT) strain HA9801. The Gram staining, plate counting, and cell and mouse infection assays were employed to examine the morphological characteristics, stress resistance, and infection process of the strains. [Results] The deletion of trr showed no effect on the morphological or growth characteristics of SS2, while it enhanced the tolerance to heat, oxidative, and acid stress conditions compared with WT. Δtrr presented reduced adhesion on murine epithelial cells and invasion capacity in cerebrovascular endothelial cells. It was easily to be phagocytosed and presented lower pathogenicity in RAW264.7 cells and mice. [Conclusion] TRR is involved in the stress responses, adhesion, and invasion and serves as a novel virulence factor for SS2.