A crucial step in using peptides as antigens is their coupling to carrier proteins. Peptides are designed to be good epitopes by themselves; however they fail to elicit a strong antibody response. The reason for this is that the epitopes are able to bind to the B-cells, but are too small to contain additional motifs required to associate with class II molecules and T-cell receptors. The carrier proteins, once coupled to the peptides, provide these additional motifs and generate a strong antibody response.
The most common carrier proteins are bovine serum albumin (BSA; 67kDa) and keyhole limpet hemocyanin (KLH; 4.5x105-1.3x107Da). In addition, we offer HyperCarrier™, a cationized BSA that has been treated with ethylene diamine, which substitutes anionic carboxyl groups with cationic aminoethyl-amide groups. The use of cationized BSA is known to elicit greater immunogenic response compared to normal BSA (1-3).
The carrier proteins are coupled to haptens, including peptides and small proteins, with the use of protein cross-linkers. For a full range of protein cross-linkers and accessories, see the "Modifications & Cross-Linking" section.
1. Muckerheide, A., et al. (1987) J. Immunol. 138: 833.
2. Muckerheide, A., et al. (1987) J. Immunol. 138: 2800.
3. Domen, P.L., et al. (1987) J. Immunol. 139: 3195.