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Infection and Immunity, February 2000, p. 744-751, Vol. 68, No. 2
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Absence of SpeB Production in Virulent Large Capsular Forms of Group A Streptococcal Strain 64

Roberta Raeder,1 Evlambia Harokopakis,2 Susan Hollingshead,2 and Michael D. P. Boyle1,*

Department of Microbiology and Immunology, Medical College of Ohio, Toledo, Ohio 43613-5806,1 and Department of Microbiology, University of Alabama Birmingham, Birmingham, Alabama 352942

Received 26 August 1999/Returned for modification 6 October 1999/Accepted 28 October 1999

Passage in human blood of group A streptococcal isolate 64p was previously shown to result in the enhanced expression of M and M-related proteins. Similarly, when this isolate was injected into mice via an air sac model for skin infection, organisms recovered from the spleens showed both increased expression of M and M-related proteins and increased skin-invasive potential. We show that these phenotypic changes were not solely the result of increased transcription of the mRNAs encoding the M and M-related gene products. Rather, the altered expression was associated with posttranslational modifications of the M and M-related proteins that occur in this strain, based on the presence or absence of another virulence protein, the streptococcal cysteine protease SpeB. The phenotypic variability also correlates with colony size variation. Large colonies selected by both regimens expressed more hyaluronic acid, which may explain differences in colony morphology. All large-colony variants were SpeB negative and expressed three distinct immunoglobulin G (IgG)-binding proteins in the M and M-related protein family. Small-colony variants were SpeB positive and bound little IgG through their M and M-related proteins because these proteins, although made, were degraded or altered in profile by the SpeB protease. We conclude that passage in either human blood or a mouse selects for a stable, phase-varied strain of group A streptococci which is altered in many virulence properties.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, Medical College of Ohio, 3055 Arlington Ave., Toledo, OH 43613-5806. Phone: (419) 383-4336. Fax: (419) 383-3002. E-mail: Mboyle{at}mco.edu.

Infection and Immunity, February 2000, p. 744-751, Vol. 68, No. 2
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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