Preparation and Conformational Properties of Benzylpenicilloyl-oligo-L-lysine Conjugates

Potency of hexavalent and decavalent anaphylactogens: affinity enhancement by epitope clusters

Two deca-L-lysine conjugates, one carrying ten, the other carrying six D-benzylpenicilloyl haptenic groups as epitope models, were used as elicitors of passive cutaneous anaphylaxis in guinea pigs. It was found that equal haptenic doses yielded virtually indistinguishable responses, i.e., the potencies were close to 10:6. Interpretation of these data appears possible by using established immunochemical concepts of preequilibria and equilibria in free solution as starting point. The discussion is simplified due to the fact that the two conjugates being decavalent and hexavalent, respectively, in free solution, are both hexavalent on cell membranes. It was found that the clusters of haptenic groups displayed by the conjugates enhance the affinity for antibody binding and that the haptenic densities are directly related to potencies. Epitope clusters of enhanced affinity interacting with cell-bound antibody may be significant and useful in a number of ways.

Chain-length dependence for secondary structure formation of homo-oligopeptides from epsilon-tert.-butyloxycarbonyl-L-lysine with a lipophilic C-terminal group

A solid-state and solution analysis of the homo-oligopeptides from epsilon-tert.-butyloxycarbonyl-L-lysine with p-oxymethylbenzylcholestan-3 beta-yl succinate as C-terminal group, using infrared absorption and circular dichroism, is described. The occurrence of intermolecular beta-structure is seen in the solid state and in solvents of low polarity, e.g. methylene chloride, for peptides of intermediate size (from pentamer to decamer). Conversely, the eicosapeptide exhibits a high percentage of alpha-helical structure both in the solid state and in 2,2,2-trifluoroethanol. The influence of the C-terminal group on the conformational preferences of the epsilon-blocked homo-oligolysines in the solid state and in organic solvents appears negligible.

Induction of immunological tolerance to the penicilloyl antigenic determinant--IV. The effect of BPO-oligolysines and cholestanol-bearing BPO-oligolysines on murine IgE responses

Penta-, deca- and eicosalysine carriers were synthesized in solution and conjugated with benzylpenicillin to give BPO-conjugates of high haptenic density. Each oligolysine conjugate was prepared in two forms--with a free C-terminus and with an esterified C-terminus carrying via a benzylester bridge in essence a lipophilic cholestanol moiety [p-oxymethylbenzylcholestan-3 beta-yl succinate (OSuco group)]. Decalysines that carried a single haptenic BPO group and succinyl groups on the other amino functions were also prepared. Suppression of IgE responses was studied in BALB/c mice. It was found that BPO-specific suppression could be induced by injecting OSuco-bearing deca- or eicosalysine conjugates before immunization with BPO-Asc in A1(OH)3. The pentalysine conjugate was only slightly effective as were all OSuco-deficient conjugates. Ongoing IgE responses were only slightly suppressed and OSuco-bearing conjugates were not more effective than OSuco-deficient derivatives. When the monohaptenic OSuco-bearing decalysine, which exhibited weak tolerogenic effects on primary as well as on ongoing responses, was applied under conditions that favour suppressor T-cell induction, a pronounced unresponsiveness resulted. Direct evidence for suppressor T-cell involvement in the abrogation of anti-BPO responses by OSuco-bearing BPO-conjugates was obtained from cell transfer experiments. The study shows that relatively small haptenic conjugates, the lower limit of effectiveness being approximately represented by decalysine conjugates, may be effective tolerogens depending on the immune status.