HUMAN IMMUNE-RESPONSE TO CATIONIZED PROTEINS .2. CHARACTERIZATION OF INTERACTION OF CATIONIZED DIPHTHERIA TOXOID WITH HUMAN MONONUCLEAR-CELLS

Cationized diphtheria toxoid (cDT) has previously been shown to be more effective than the native protein as an inducer of human antigen-specific T cell responses. In the present study, biotin-labeled antigen and flow cytometric analysis were used to examine the possibility that enhanced immunogenicity of cDT may be a consequence of preferential binding to antigen-presenting cells. Strong binding of cDT, relative to native antigen, was noted for both monocytes and B cells. Characteristics of binding were similar for both cell types, including rapid saturation, temperature independence, and inhibition by unlabeled cationized proteins. Although both B cells and monocytes bound cDT, only monocytes were effective in triggering T cell proliferation, possibly as a result of slow internalization of bound antigen by B cells. Definition of the target structures for cationized proteins may allow for the design of more efficient vaccines, which would be specifically targeted to antigen-presenting cells in vivo. © 1993 Academic Press. All rights reserved.