Streptococcal pyrogenic exotoxin B causes mitochondria damage to polymorphonuclear cells preventing phagocytosis of group A streptococcus.
The streptococcal pyrogenic exotoxin B (SpeB) is known to be involved in group A streptococcus (GAS) survival in blood, but the detailed mechanism is not clear. For clarification of this issue, speB isogenic mutants of strains M6 and M49 were constructed by using an integrational plasmid and confirmed by Southern blot analysis. The resistance to phagocytosis of wild-type strains and their speB isogenic mutants was analyzed. The results demonstrated a five-fold increase in phagocytosis of speB mutants compared to that of wild-type strains in whole blood, but no significant difference in plasma. To further clarify whether this effect is due to a functional SpeB protein, recombinant SpeB (r-SpeB) and a SpeB mutant protein lacking proteinase activity (r-C192S) were purified and incubated with a speB mutant in whole blood. The results showed a two- to threefold increase in resistance to phagocytosis when the M6 speB mutant was incubated with r-SpeB, but not with r-C192S. Incubation with the wild-type strain, speB mutant, or the r-SpeB protein did not affect the total cell number of polymorphonuclear (PMN) cells in whole blood under laboratory conditions. However, the PMN cells' mitochondria showed decreasing dehydrogenase activity and loss of membrane potential after r-SpeB treatment. These data indicate that SpeB could cause the mitochondria damage to the PMN cells, preventing immune clearance at an early infectious stage.
Chiang-Ni
Chuan
C
Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Wang
Chih-Hung
CH
Tsai
Pei-Jane
PJ
Chuang
Woei-Jer
WJ
Lin
Yee-Shin
YS
Lin
Ming-T
MT
Liu
Ching-Chuan
CC
Wu
Jiunn-Jong
JJ
D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D045744:Cell Line, Tumor; D005098:Exotoxins / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D006801:Humans; D008564:Membrane Potentials; D008928:Mitochondria / Q000201:enzymology / Q000473:pathology*; D016254:Mutagenesis, Insertional; D009504:Neutrophils / Q000276:immunology* / Q000382:microbiology; D010088:Oxidoreductases / Q000032:analysis; D010587:Phagocytosis; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification; D013297:Streptococcus pyogenes / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*
D001426:Bacterial Proteins; D005098:Exotoxins; D011994:Recombinant Proteins; C027951:erythrogenic toxin; D010088:Oxidoreductases