Cloning, expression and interaction of human T-cell receptors with the bacterial superantigen SSA.

DE MARZÍ MC, FERNÁNDEZ MM, SUNDBERG EJ, MOLINERO L, ZWIRNER NW, LLERA AS, MARIUZZA RA, MALCHIODI EL.

EUROPEAN JOURNAL OF BIOCHEMISTRY

European Society of Immunology

Año: 2004 vol. 271 p. 4075 - 4083

0014-2956

Superantigens (SAgs) are a class of disease-causing and immunostimulatory proteins of bacterial or viral origin that activate a large number of T-cells through interaction with the Vâ domain of T cell receptors (TCRs).  Recombinant TCR b chains were constructed with human variable domains Vb5.2, Vb1 and Vb2.1, expressed as inclusion bodies, refolded and purified.  The Streptococcus pyogenes SAg SSA-1 was cloned and expressed as a soluble periplasmic protein.  SSA-1 was obtained both as a monomer and a dimer that has an intermolecular disulfide bond.  We analyzed the biological activity of the recombinant SAgs by proliferation assays. The results suggest that SSA dimerization occludes the TCR interaction site.  Naturally occurring SSA dimerization was also observed in supernatants of S. pyogenes isolates. A SSA mutant (SSAC26S) was produced to eliminate the Cys responsible for dimerization.  Affinity assays using a resonant biosensor showed that both the mutant and monomeric wild type SSA have affinity for human Vb5.2 and Vb1 with KD from 9 to 11 ìM with a fast kass and a moderately fast kdiss.  In spite of the reported stimulation of Vb2.1 bearing T-cell by SSA, we observed no measurable interaction.