IDENTIFICATION OF STAPHYLOCOCCAL-ENTEROTOXIN-B SEQUENCES IMPORTANT FOR INDUCTION OF LYMPHOCYTE-PROLIFERATION BY USING SYNTHETIC PEPTIDE-FRAGMENTS OF THE TOXIN

A series of 13 synthetic peptides, approximately 30 amino acids each, which spanned the entire sequence of staphylococcal enterotoxin B (SEB ) were tested to evaluate their effects on T-cell proliferation in a c ulture system containing elutriated human peripheral blood lymphocytes incubated with a specific ratio of mononuclear cells. Four peptide re gions were found to inhibit SEB-induced proliferation; they included s equences 1 to 30 (previously thought to be involved in major histocomp atibility complex class II binding), 61 to 92 (sequences which relate to the T-cell receptor site), 93 to 112 (a linear sequence correspondi ng to the cysteine loop), and 130 to 160 (containing a highly conserve d sequence, KKKVTAQEL). Antisera raised to this last peptide were capa ble of neutralizing SEB-induced proliferation. Antisera raised against the peptides which overlapped this sequence also were somewhat inhibi tory. Neutralizing antisera were not produced from any other peptide s equence tested. To determine if any of these effects were nonspecific with regard to SEB-induced proliferation, the peptides were tested for inhibition of phorbol dibutyryl ester-induced proliferation, and only the sequence 93 to 112 (corresponding to the cysteinyl loop region) w as consistently inhibitory (40%). Of the regions which displayed inhib ition of SEB-induced proliferation, the peptide 130 to 160 inhibited b inding of I-125-SEB to lymphocytes. These data suggest that the resiud es containing and surrounding the sequence KKKVTAQEL may be critical i n the SEB-induced proliferation and may be useful for developing neutr alizing antisera to SEB.