Immunization with peptide antigens

The requirement of multifunctional peptide complexes is perhaps most obvious for the development of subunit peptide vaccines. Successful immunizations with peptide antigens cannot be achieved without the inclusion of a bystander T-helper cell determinant in the chemical entity (4) or in the immunizing cocktail (5). For outbred animals and humans, multiple peptide epitopes, representing determinants of more than one major histocompatibility complex (MHC) proteins, are used to overcome subunit vaccine unresponsiveness, and this also improves antigen presentation in inbred animals (6). 

Fig. 8.10 Titers of antibodies at day 50 induced by plant-derived CTB-2L21 recombinant protein. Balb/c mice were intraperitoneally immunized with leaf extract from CTB-2L21 transgenic plants. Animals were boosted at days 21 and 35. Each mouse received 20 pg of CTB-2L21 recombinant protein. Individual samples of mouse serum were titrated against 2L21 synthetic peptide,VP2 protein and a control peptide (amino acids 122-135 of hepatitis B virus surface antigen). Titers were expressed as the highest serum dilution to yield twice the absorbance mean of preimmune sera. M1-M6 mice 1 to 6 2L21 epitope from the VP2 protein of the canine parvovirus CTB cholera toxin B VP2 protein of the canine parvovirus that includes the 2L21 epitope.

The results clearly show (49) that Immune sera raised to each of the synthetic peptides (6 6r 1 amino acids In size) contain antibodies that bind specifically to native Mb (Table I). Thus Immunization with a peptide representing a single antigenic site, at least when native Mb Is the Immunizing antigen. Is effective In eliciting antibodies that will bind specifically to native Mb and exclusively to the peptide used In Immunization (Table I). 

Table VI. Specificity of monoclonal antibodies from immunization with free peptide representing surface regions that are non-antigenic in whole Mb...

As described above, the haptenised protein or hapten protein complex has to be presented to the immune system for the system to be aware of it as an antigen. With intracellular antigens, this requires expression of fragment of the hap ten-protein complex on the cell surface via major his toco mpatibility complex (MHC) molecules. These can bind almost any peptide (Fig. 7.78). 

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