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Infection and Immunity, September 2000, p. 5018-5025, Vol. 68, No. 9
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Genetic Polymorphisms of Group B Streptococcus scpB Alter Functional Activity of a Cell-Associated Peptidase That Inactivates C5a

John F. Bohnsack,1 Shinji Takahashi,2 Laura Hammitt,1 Dylan V. Miller,1 Adrienne A. Aly,1 and Elisabeth E. Adderson3,*

Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee 381053; Departments of Pediatrics and Pathology, University of Utah School of Medicine, Salt Lake City, Utah 841321; and Department of Microbiology, Joshi-Eiyoh University, Sakado, Saitama 350-0288, Japan2

Received 4 October 1999/Returned for modification 29 November 1999/Accepted 2 June 2000

Many group B Streptococcus agalactiae strains and other pathogenic streptococci express a cell-associated peptidase that inactivates C5a (C5a-ase), the major neutrophil chemoattractant produced by activation of the complement cascade. Type III group B streptococci (GBS) can be classified genotypically into three restriction digest pattern types. Functional C5a-ase activity of GBS correlates with this genetic typing; therefore, we sought to identify a genetic basis for this phenomenon. Southern hybridization confirms that all type III GBS contain scpB, the gene encoding GBS C5a-ase. GBS strains with high C5a-ase functional activity and those with no or very low activity both express immunoreactive C5a-ase. The scpB sequence of strain I30, which has high C5a-ase activity, is 98.2% homologous to the previously reported serotype II GBS scpB sequence. The scpB sequences of strains I25 and GW, which have low or no C5a-ase activity, are identical. The predicted I25 and GW C5a-ase proteins share a four-amino-acid deletion affecting the protease histidine active-site consensus motif. Recombinant I30 C5a-ase has good functional activity, whereas recombinant I25 C5a-ase has low activity. These data demonstrate that functional C5a-ase differences between type III GBS strains are attributable to a genetic polymorphism of scpB. The ubiquitous expression of C5a-ase, irrespective of functional activity, suggests that C5a-ase may have a second, as yet unidentified, function.


* Corresponding author. Mailing address: Department of Infectious Diseases, St. Jude Children's Research Hospital, 332 N. Lauderdale St., Memphis, TN 38105-2794. Phone: (901) 495-3459. Fax: (901) 495-3099. E-mail: Elisabeth.Adderson{at}STJUDE.org.


Infection and Immunity, September 2000, p. 5018-5025, Vol. 68, No. 9
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.



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