HtpS, a novel immunogenic cell surface-exposed protein of Streptococcus suis, confers protection in mice


  • Editor: Akio Nakane

Correspondence: Jiaqi Tang, Department of Epidemiology, Research Institute for Medicine of Nanjing Command, 293 East Zhongshan Road, Nanjing 210002, China. Tel.: +86 25 8452 6002; fax: +86 25 8450 7094; e-mail:
Present address: Zhuqing Shao, School of Life Science, Nanjing University, Nanjing 210093, China.


Streptococcal histidine triad protein was identified recently as a cell surface-associated protein family. Five members of this family (PhtA, PhtB, PhtD, PhtE and HtpA), derived from Streptococcus pneumoniae and Streptococcus pyogenes, have been shown as antigens that confer protection to the host on infection. In this report, a gene sequence highly homologous to htpA and phtD (designated htpS, the histidine triad protein of Streptococcus suis) was identified from S. suis 2 Chinese strain 05ZYH33. Our data revealed that htpS is extremely conserved in S. suis 2 and widely distributed in 83% (29/35) of 35 S. suis serotypes. It was also demonstrated by Western blot and flow cytometry that HtpS is a cell surface-associated protein that was expressed during S. suis 2 infection. An antibody against HtpS could increase the deposition of human complement 3 on S. suis 2 and also enhance the clearance of S. suis 2 in whole blood. In addition, mice could be immunized against S. suis 2 infection and were well protected after immunization with recombinant HtpS.