Vaccines are most commonly composed of attenuated or inactivated disease-causing pathogens. While they are generally effective, they can cause complications in immunocompromised patients and have a shorter shelf-life. Since most T lymphocytes recognize specific amino acid sequences on an antigen, synthetic peptide vaccines represent a cost effective alternative to traditional vaccines; however, for them to be effective, these immunogenic sequences need to be identified.
In the quest to find immunogenic epitopes on proteins, there are two main bottlenecks: (1) the three-dimensional structure of proteins may "hide" the most immunogenic sequences and (2) there might be multiple antigenic epitopes on a target protein. Peptide libraries can address both of these bottlenecks by spanning multiple combinations of peptides in parallel. In addition, peptide pooling can also facilitate epitope discovery for vaccines. For the latter, multiple immunostimulatory epitopes are combined to determine which combinations best stimulate lymphocytes.
Predicting vaccine performance is an important step in the development of new vaccines. While human challenge is typically the most informative measure for determining vaccine efficacy, this is not always possible or ethical, especially when dealing with vaccines for the treatment of infectious diseases. In addition, part of predicting how effective a vaccine will be depends on a thorough understanding of the cellular interactions that mediate the immune response. In this regard, peptide libraries can elucidate how well a vaccine will work in patients.