Differential activation of the Toll-like receptor 2/6 complex by lipoproteins of Streptococcus suis serotypes 2 and 9

P.J. Wichgers, J.M.J. Rebel, M.A. Smits, J.P. van Putten, H.E. Smith

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Streptococcus suis causes invasive infections in pigs and occasionally in humans. Worldwide, S. suis serotype 2 is most frequently isolated from diseased piglets, but the less virulent serotype 9 is emerging, at least in Europe. We compared the activation of human Toll-like receptors (hTLRs) by S. suis serotype 2 and 9 strains to better understand the role of the innate immune response in fighting S. suis infections. Neither live nor heat-killed log phase grown S. suis activated the hTLR1/2, hTLR2/6 and hTLR4/MD-2 complexes. However, the hTLR2/6 complex was specifically activated by both serotypes after disruption of the cell wall synthesis using penicillin. Activation levels of the hTLR2/6 complex were higher for serotype 9 strains compared to serotype 2 strains suggesting intrinsic differences in cell wall composition between both serotypes. The hTLR2/6 activating fractions decreased in molecular size after digestion with proteinase K and were sensitive for lipoprotein lipase digestion and NaOH hydrolysis, indicating lipoprotein(s) as active component(s). Overall, our results indicate that S. suis lipoproteins activate TLR2/6 but not TLR1/2 and that the clinically different serotypes 2 and 9 display differential release of TLR ligand when cell wall integrity is compromised
Original languageEnglish
Pages (from-to)363-370
JournalVeterinary Microbiology
Issue number2-4
Publication statusPublished - 2010



  • bacterial lipoproteins
  • type-2 strains
  • recognition
  • virulence
  • humans
  • identification
  • resistance
  • stimulate
  • cytokine
  • binding

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