A peptide vaccine is a subunit vaccine based on any peptide that serves to immunize an organism against a pathogen. Peptide vaccines are often synthetic vaccines and mimic naturally occurring proteins from pathogens.  These vaccines are very specific and efficient in evoking immune response. Conventional peptide vaccines are prepared through purification methods. Peptide vaccines are prepared through recombinant technology. Example: cholera vaccine and FMDV vaccine.
In addition to infectious pathogens, peptide vaccines can be utilised as therapeutic cancer vaccines, where peptides from tumor associated antigens are used to induce effective anti-tumor T-cell response. Synthetic long peptides (SLP) have shown promising successful results.
Peptide vaccines through recombinant DNA technology
A small discrete portion (domain) of an antigenic protein can act as an effective subunit vaccine. This small part of the antigen is a peptide, consisting of a small chain of amino acids, and this forms a single epitope (antibody binding region). Short peptides which constitute epitopes, will be immunogenic and could be used as peptide vaccines. For example, FMDV Protein-1 (VPI) is an immunogenic peptide. It has been chemically synthesized and tested for elicitation of immune response.
However, too small peptides are sometimes not sufficiently immunogenic, example peptides containing only 15 to 20 amino acids are less immunogenic than larger peptides. Sometimes when the peptide epitope is too small, it requires a carrier protein like adjuvant, to make it more immunogenic.
- A single epitope (15 to 20 amino acids long) may not be sufficiently immunogenic.
- To be effective, an epitope must consist of a stretch of amino acids sufficiently long to elect immune response.
- Peptide must assume the same configuration as the antigenic determinant of the original antigenic protein. However, epitope configuration may change during purification.
- Patarroyo, Manuel Elkin (1990). "Studies in owl monkeys leading to the development of a synthetic vaccine against the asexual blood stages of Plasmodium falciparum". American Journal of Tropical Medicine and Hygiene. 43, 4 (4): 339–354. doi:10.4269/ajtmh.1990.43.339. PMID 2240362.
- "Synthetic peptide vaccines". World Health Organization. Retrieved 24 July 2015.
- Melief, Cornelis J.M.; van der Burg, Sjoerd H. (May 2008). "Immunotherapy of established (pre)malignant disease by synthetic long peptide vaccines". Nature Reviews Cancer. 8 (5): 351–360. doi:10.1038/nrc2373. ISSN 1474-175X. PMID 18418403.