A peptide based on the CDR1 of a pathogenic anti-DNA antibody is more efficient than its analogs in inhibiting autoreactive T cells

A peptide based on the sequence of the complementarity determining regions 1 (pCDR1) of a pathogenic murine monoclonal anti-DNA antibody (5G12) that bears the 16/6 Id, was synthesized. This peptide was shown to be immunodominant in BALB/c mice, and induced a mild lupus-like disease upon immunization. Furthermore, the pCDR1 when injected in a soluble form was capable of inhibiting the proliferation of lymph node cells primed to either the peptide or the anti-DNA, 16/6 Id antibodies of either murine (5C12) or human (16/6 Id) origin. We have designed and synthesized 39 analogs based on pCDRI with single amino acid substitutions. Out of the above, two analogs, namely, Asp14 and Ser16 inhibited the proliferative responses of a pCDR1-specific T cell line to its stimulating peptide by more than 50%. These two analogs were therefore further studied. Administration of analog Ser16 concomitant with the immunization with pCDR1 inhibited efficiently the proliferative responses of lymph node cells to pCDR1, although pCDR1 was more efficient in its inhibitory capacity. Neither of the analogs were capable of inhibiting significantly the proliferative responses to the human monoclonal anti-DNA antibody with the 16/6 Id whereas pCDR1 did so efficiently. Thus, pCDR1 is more efficient than all its tested analogs in immunomodulating SLE associated immune responses.