What role do streptococcal pyrogenic exotoxins (SPEs) have in group A streptococcal (GAS) infections?

Updated: Sep 07, 2018
  • Author: Zartash Zafar Khan, MD, FACP; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Answer

The family of streptococcal pyrogenic exotoxins (SPEs) includes SPEs A, B, C, and F. These toxins are responsible for the rash of scarlet fever. Other pathogenic effects caused by these substances include pyrogenicity, cytotoxicity, and enhancement of susceptibility to endotoxin. SPE B is a precursor of a cysteine protease, another determinant of virulence. [12]

Group A streptococcal isolates associated with streptococcal TSS encode certain SPEs (ie, A, C, F) capable of functioning as superantigens. These antigens induce a marked febrile response, induce proliferation of T lymphocytes, and induce synthesis and release of multiple cytokines, including tumor necrosis factor, interleukin-1 beta, and interleukin-6. This activity is attributed to the ability of the superantigen to simultaneously bind to the V-beta region of the T-cell receptor and to class II major histocompatibility antigens of antigen-presenting mononuclear cells, resulting in widespread, nonspecific T-cell proliferation and increased production of interleukin-2.


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