title: Invasive M1T1 group A Streptococcus undergoes a phase-shift in vivo to prevent proteolytic degradation of multiple virulence factors by SpeB.
abstract: A globally disseminated strain of M1T1 group A Streptococcus (GAS) has been associated with severe infections in humans including necrotizing fasciitis and toxic shock syndrome. Recent clinicoepidemiologic data showed a striking inverse relationship between disease severity and the degree to which M1T1 GAS express the streptococcal cysteine protease, SpeB. Electrophoretic 2-D gel analysis of the secreted M1T1 proteome, coupled with MALDI-TOF mass spectroscopy, revealed that expression of active SpeB caused the degradation of the vast majority of secreted GAS proteins, including several known virulence factors. Injection of a SpeB+/SpeA- M1T1 GAS strain into a murine subcutanous chamber model of infection selected for a stable phase-shift to a SpeB-/SpeA+ phenotype that expressed a full repertoire of secreted proteins and possessed enhanced lymphocyte-stimulating capacity. The proteome of the SpeB-in vivo phase-shift form closely matched the proteome of an isogenic speB gene deletion mutant of the original M1T1 isolate. The absence or the inactivation of SpeB allowed proteomic identification of proteins in this M1T1 clone that are not present in the previously sequenced M1 genome including SpeA and another bacteriophage-encoded novel streptodornase allele. Further proteomic analysis of the M1T1 SpeB+ and SpeB- phase-shift forms in the presence of a cysteine protease inhibitor demonstrated differences in the expression of several proteins, including the in vivo upregulation of SpeA, which occurred independently of SpeB inactivation.
authors.affiliation: Department of Microbiology, University of Tennessee-Health Sciences Center (UTHSC) Memphis, TN, USA.
authors.forename: Ramy K
authors.initials: RK
authors.lastname: Aziz
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Pabst
authors.forename: Arthur
authors.initials: A
authors.lastname: Jeng
authors.forename: Rita
authors.initials: R
authors.lastname: Kansal
authors.forename: Donald E
authors.initials: DE
authors.lastname: Low
authors.forename: Victor
authors.initials: V
authors.lastname: Nizet
authors.forename: Malak
authors.initials: M
authors.lastname: Kotb
mesh_terms: D000818:Animals; D001426:Bacterial Proteins; D003546:Cysteine Endopeptidases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D004195:Disease Models, Animal; D019115:Fasciitis, Necrotizing / Q000382:microbiology; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012772:Shock, Septic / Q000382:microbiology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013297:Streptococcus pyogenes / Q000145:classification / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity*; D014158:Transcription, Genetic; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D003546:Cysteine Endopeptidases; C042477:streptopain