Delivery of synthetic peptides by anti-class II MHC monoclonal antibodies induces specific adjuvant-free IgG responses in vivo.

Two synthetic peptides from different regions of the glycoprotein D of herpes simplex virus (HSV) have been used to determine whether or not anti-peptide IgG responses can be generated in the absence of adjuvant. Based on an earlier demonstration (Carayanniotis and Barber, 1987) that protein antigens could be made immunogenic in the absence of adjuvant, if coupled to MAbs specific for the recipient's class II major histocompatibility complex (MHC) antigens, the HSV synthetic peptides were photocoupled to avidin and mixed with biotinylated anti-class II or control antibodies. Peptide-specific IgG responses were obtained when avidin-peptide conjugates coupled to an anti-I-Ak MAb were injected into (H-2k x H-2b) F1 mice, but not when injected into H-2b mice. The same avidin-peptide conjugates were non-immunogenic when coupled to a control anti-influenza virus nucleoprotein antibody or biotinylated bovine serum albumin. These data indicate that targeting synthetic peptides to class II bearing cells in vivo can elicit peptide-specific IgG responses without the need for adjuvant. These findings offer a new approach to the design and delivery of adjuvant-independent vaccine agents based on synthetic peptide antigens.