Close Correlation of Streptococcal DNase B (sdaB) Alleles with emm Genotypes in Streptococcus pyogenes

Abstract

Streptococcal DNases are major exoenzymes and possible virulence factors in Streptococcus pyogenes and are classified into four types: DNase A, B, C and D. Among these DNases, DNase B, which is also designated as mitogenic factor (MF) or streptococcal pyrogenic exotoxin F (speF) (3,4), is dominant, although its role in the pathogenesis of S. pyogenes has not been well elucidated. S. pyogenes strains commonly express DNase B, but the other three DNases are not frequently expressed and thus DNase B has a major share of total DNase activity in most strains (5,7,8). Determination of antibody titers to DNase B has been used to confirm a clinical diagnosis of a previous S. pyogenes infection and the level of anti-DNase B antibody in invasive cases was significantly lower than those in healthy individuals (1).The present study was undertaken to determine Abstract: DNase B is a major nuclease and a possible virulence factor in Streptococcus pyogenes. The allelic diversity of streptococcal DNase B (sdaB) gene was investigated in 83 strains with 14 emm genotypes. Of the 15 alleles identified, 11 alleles carried only synonymous nucleotide substitutions. On the other hand, 4 alleles had a non-synonymous substitution other than synonymous substitutions, resulting in the substitution of a single amino acid. The distribution of each allele was generally emm genotype-specific. Only sdaB7 was found in both emm2 and emm4. The promoter region was highly conserved and DNase B protein was similarly expressed in all alleles.

Immunity to Sda1 Protects against Infection by Sda1+ and Sda1− Serotypes of Group A Streptococcus

“…The NETs degradation inhibition assay showed that, similar to the M1 culture supernatant, the supernatant from M3.11 culture degraded NETs and the degradation was prevented by rabbit anti-Sda1 IgG (Figure 5B). To confirm Sda1 anti-serum can recognize other GAS DNases, recombinant DNase B, a DNase frequently expressed in most GAS strains [28], was generated. Western blot revealed that Sda1 antiserum cross-reacted with the recombinant DNase B (26.7 kD) (Figure 5C).…”