Inactivation of Streptococcus pyogenes extracellular cysteine protease significantly decreases mouse lethality of serotype M3 and M49 strains.

Abstract

Cysteine proteases have been implicated as important virulence factors in a wide range of prokaryotic and eukaryotic pathogens, but little direct evidence has been presented to support this notion. Virtually all strains of the human bacterial pathogen Streptococcus pyogenes express a highly conserved extracellular cysteine protease known as streptococcal pyrogenic exotoxin B (SpeB). Two sets of isogenic strains deficient in SpeB cysteine protease activity were constructed by integrational mutagenesis using nonreplicating recombinant plasmids containing a truncated segment of the speB gene. Immunoblot analyses and enzyme assays confirmed that the mutant derivatives were deficient in expression of enzymatically active SpeB cysteine protease. To test the hypothesis that the cysteine protease participates in host mortality, we assessed the ability of serotype M3 and M49 wild-type strains and isogenic protease-negative mutants to cause death in outbred mice after intraperitoneal inoculation. Compared to wild-type parental organisms, the serotype M3 speB mutant lost virtually all ability to cause mouse death ( P Ͻ 0.00001), and similarly, the virulence of the M49 mutant was detrimentally altered ( P Ͻ 0.005). The data unambiguously demonstrate that the streptococcal enzyme is a virulence factor, and thereby provide additional evidence that microbial cysteine proteases are critical in host-pathogen interactions.

Group A Streptococcal Cysteine Protease Degrades C3 (C3b) and Contributes to Evasion of Innate Immunity

“…Lukomski et al (28,29) reported that the ⌬speB mutant was effectively cleared by neutrophils in mice and not recovered from their blood after subcutaneous infection. In further investigations, they demonstrated that SpeB is required for dissemination of S. pyogenes from the initial infection site, resulting in severe infectious diseases including necrosis; however, how SpeB contributes to evasion of the host innate immunity has not been clear.…”

Naturally occurring single amino acid replacements in a regulatory protein alter streptococcal gene expression and virulence in mice

“…Importantly, the highest frequency of SNPs was found in the gene encoding regulator of proteinase B (RopB, also known as Rgg) (13). RopB is a key positive transcriptional regulator of the gene encoding streptococcal proteinase B (SpeB), a secreted extracellular cyste-ine proteinase and proven virulence factor (24)(25)(26). RopB directly regulates speB and also appears to influence expression of several other genes encoding proteins involved in virulence and metabolic functions (27)(28)(29).…”

Streptococcus didelphis sp. nov., a streptococcus with marked catalase activity isolated from opossums (Didelphis virginiana) with suppurative dermatitis and liver fibrosis.

“…GAS invasiveness is attributed mainly to elaboration of streptococcal pyrogenic exotoxin B (SpeB), a conserved cysteine protease expressed by virtually all Streptococcus pyogenes strains (Burns et al, 1998 ;Lukomski et al, 1997Lukomski et al, , 1998 Table 5. For a newly identified strain of Streptococcus to be described as S. didelphis, it has to be β-haemolytic, catalase-positive on initial passage on non-blood-containing media after growth on blood-containing media and a full length of 16S rRNA gene of the new isolate may not differ from S. didelphis 16S rRNA gene sequence by 1n5%.…”