CARRIER DESIGN - CYTOTOXICITY AND IMMUNOGENICITY OF SYNTHETIC BRANCHED POLYPEPTIDES WITH POLY(L-LYSINE) BACKBONE

Several synthetic branched polypeptides have been evaluated for in vit ro toxicity and for immunogenicity. Preliminary investigations were ca rried out on the effect of these compounds on haematologic and serum p arameters of mice in vivo. The polymers contain poly[Lys] backbone and short side chains composed of about three DL-Ala residues and one oth er amino acid residue (X) either at the end of the branches {poly[Lys- (X(i)-DL-Ala(m))], XAK} or at position next to the backbone {poly[Lys- (DL-Ala(m)-X(i))], AXK}. Cytotoxicity was analyzed in three systems us ing rat liver, mouse spleen and HeLa cells. Our data clearly suggest t hat there is a strong correlation between charge and cell killing acti vity of branched polypeptides. Thus polypeptides of amphoteric charact er are basically non-toxic, while compounds with predominantly cationi c groups were found to be toxic or highly toxic. Immunogenicity and an tigenicity of polypeptides were studied in three mouse strains (BALB/c , CBA, C57/B1). In contrast to the most immunogenic, cationic polypept ide X = D-Leu (D-UK), the glutamic acid containing analogues (EAK, D-E AK) induced IgG type immune responses only in BALB/c mice. The differe nce in the potency of EAK compared to D-EAK to elicit IgG type antibod ies suggests that the introduction of chain terminating D-amino acids can enhance antigenicity. These results demonstrate the value of branc hed polypeptides in studying chemical structure-biological function co rrelations required for drug delivery and/or for constructing syntheti c vaccine.