DEPENDENCE OF THE MURINE-ANTIBODY RESPONSE TO AN ANTI-CD4 CDR2 V-H PEPTIDE ON IMMUNOGEN FORMULATION

A peptide corresponding to the second complementarity determining regi on of the heavy chain (CDR2 V-H) from a murine anti-CD4 monoclonal ant ibody, designated L202, was synthesized by solid phase methodology in a number of different antigenic forms, for the purpose of comparing th e effectiveness of different adjuvant-carrier systems in the induction of a murine antibody response against the immunizing peptide and pare nt antibody molecule. Two of the synthetic constructs contained the pa lmitoyl and lmitoyl-cysteinyl-S-(2,3-palmitoyloxy)-propanediol (PAM(3) Cys) moieties, respectively, attached to the peptide amino terminus wi th the immunogen comprising liposomal formulations of each. A third im munogen consisted of the CDR2 V-H peptide admired with the PAM(3)Cys n on-covalently and incorporated into liposomes (PAM(3)Cys + CDR2 V-H). A fourth composition comprised the CDR2 V-H peptide conjugated to KLH via the sulfhydryl of an added N terminal cysteine (KLH-CDR2 V-H) and injected with Complete Freund's adjuvant (CFA). A fifth immunogen cons isted of the CDR2V(H) peptide synthesized on an octameric, branched po lylysine core as a multiple antigenic peptide (MAP-CDR2 V-H) injected in the presence of Freund's adjuvant. Groups of five mice were injecte d intramuscularly with each of these immuno ens and bled at two week i ntervals. The highest anti-peptide gamma-immunoglobulin (IgG) response s (against uncoupled peptide by ELISA) after 56 days were obtained wit h mice receiving the PAM(3)Cys-CDR2 V-H peptide. However, when screene d against the CDK2 V-H peptide present as the MAP derivative by ELISA, IgG raised against the cognate MAP-CDR2 peptide was much more reactiv e than IgG raised against the liposomal PAM(3)Cys-CDR2 V-H immunogen. In either case, IgG raised against the KLH-CDR2 V-H conjugate was poor ly reactive. These differences in reactivity to the two forms of the C DR2 V-H peptide by ELISA did not correspond to major differences in re activities to the intact L202 Ab by ELISA. Although the IgG against th e MAP immunogen was slightly more reactive than the other antisera aga inst the L202 Ab, all titers were less than 1:100. These data illustra te some limitations of using anti-peptide responses as indicators of p otential reactivity against the native protein, but suggest that alter nate formulations including lipoidal peptides are more effective than corresponding KLH-peptide conjugates in eliciting Ab responses against poorly immunogenic epitopes.