Identification of in-vivo induced genes of Streptococcus suis serotype 2 specially expressed in infected human.

Streptococcus suis (S. suis) serotype 2 usually cause infection in swine. Recently, two large-scale outbreaks in China with severe streptococcal toxic shock syndrome (STSS) and high mortality raised worldwide concern to human S. suis infection. To reveal the molecular pathogenesis of S. suis 2 during human infection, in-vivo induced antigen technology (IVIAT) was applied to identify the in-vivo induced genes (ivi genes) of S. suis 05ZYH33. The ivi genes are specifically expressed or up-regulated in-vivo and always associated with the in-vivo survival and pathogenicity of pathogens. In present study, convalescent sera from S. suis 05ZYH33 infected patients were pooled and fully adsorbed with in-vitro grown S. suis 05ZYH33 and Escherichia coli BL21 (DE3). Genomic expression library of 05ZYH33 was repeatedly screened with colony immunoblot assay using adsorbed sera. Finally, 19 genes were assessed as ivi genes of 05ZYH33. Fifteen of 19 genes encode proteins with biological functions in substance transport and metabolism, cell structure biogenesis, cell cycle control, replication, translation and other functions. The 4 remaining genes encode proteins with unknown functions. Of the 19 ivi genes, five (SSU05_0247, 0437, 1577, 1664 and 2144) encode proteins with no immunoreactivity to control sera from healthy individuals never exposed to 05ZYH33. The successful identification of ivi genes not only sheds light on understanding the pathogenesis of S. suis 05ZYH33 during its human infection, but also provides potential targets for the developments of new vaccines, therapeutic drugs and diagnostic reagents against human S. suis infection.