Lgt processing is an essential step in Streptococcus suis lipoprotein mediated innate immune activation
Wichgers, P.J. ; Rebel, J.M.J. ; Smits, M.A. ; Putten, J.P. van; Smith, H.E. - \ 2011
PLoS One 6 (2011)7. - ISSN 1932-6203
bacterial lipoproteins - lipid modification - virulence - serotype-2 - identification - pneumoniae - proteins - type-2 - prelipoproteins - polysaccharide
Background Streptococcus suis causes invasive infections in pigs and occasionally in humans. The host innate immune system plays a major role in counteracting S. suis infections. The main components of S. suis able to activate the innate immune system likely include cell wall constituents that may be released during growth or after cell wall integrity loss, however characterization of these components is still limited. Methology/Principal Findings A concentrated very potent innate immunity activating supernatant of penicillin-treated S. suis was SDS-PAGE fractionated and tested for porcine peripheral blood mononucleated cell (PBMC) stimulating activity using cytokine gene transcript analysis. More than half of the 24 tested fractions increased IL-1ß and IL-8 cytokine gene transcript levels in porcine PBMCs. Mass spectrometry of the active fractions indicated 24 proteins including 9 lipoproteins. Genetic inactivation of a putative prolipoprotein diacylglyceryl transferase (Lgt) gene resulted in deficient lipoprotein synthesis as evidenced by palmitate labeling. The Lgt mutant showed strongly reduced activation of porcine PBMCs, indicating that lipoproteins are dominant porcine PBMC activating molecules of S. suis. Conclusion/Significance This study for the first time identifies and characterizes lipoproteins of S. suis as major activators of the innate immune system of the pig. In addition, we provide evidence that Lgt processing of lipoproteins is required for lipoprotein mediated innate immune activation
Lipoprotein signal peptidase of Streptococcus suis serotype 2
Greeff, A. de; Buijs, H. ; Alphen, L. van; Smith, H.E. - \ 2003
Microbiology 149 (2003)6. - ISSN 1350-0872 - p. 1399 - 1407.
temperature-sensitive mutant - complete genome sequence - germ-free pigs - ii lsp gene - nucleotide-sequence - bacillus-subtilis - virulence genes - tonsillar specimens - tagged mutagenesis - lipid modification
This paper reports the complete coding sequence for a proliprotein signal peptidase (SP-ase) of Streptococcus suis, Lsp. This is believed to be the first SP-ase described for S. suis. SP-ase II is involved in the removal of the signal peptide from glyceride-modified prolipoproteins. By using in vitro transcription/translation systems, it was shown that the lsp gene was transcribed in vitro. Functionality of Lsp in Escherichia coli was demonstrated by using an in vitro globomycin resistance assay, to show that expression of Lsp in E. coli increased the globomycin resistance. An isogenic mutant of S. suis serotype 2 unable to produce Lsp was constructed and shown to process lipoproteins incorrectly, including an S. suis homologue of the pneumococcal PsaA lipoprotein. Five piglets were inoculated with a mixture of both strains in an experimental infection, to determine the virulence of the mutant strain relative to that of the wild-type strain in a competitive challenge experiment. The data showed that both strains were equally virulent, indicating that the knockout mutant of lsp is not attenuated in vivo.