In silico predicted mycobacterial epitope elicits in vitro T-cell responses

• Epitope-based design strategies offer a rational alternative to traditional vaccines.
• Immunoinformatics tools were used to predict epitopes within the protein Ag85B.
• A contiguous 28 amino acid multi-epitope cluster (Ep85B) was identified.
• Ep85B confers 99% population coverage in tuberculosis-endemic regions.
• Ep85B induces significant proliferation of CD4+ and memory CD4+ T-cells in vitro.

Epitope-based vaccines permit the selection of only a specific subset of epitopes to induce the necessary immune response, thus providing a rational alternative to conventional design approaches. Using a range of immunoinformatics tools, we identified a novel, contiguous 28 amino acid multi-epitope cluster within the highly conserved secretory protein Ag85B of Mycobacterium tuberculosis, the causative agent of TB. This cluster, named Ep85B, is composed of epitopes which bind to three HLA Class I and 15 Class II molecules, and harbors the potential to generate 99% population coverage in TB-endemic regions. We experimentally evaluated the capacity of Ep85B to elicit T-cell immune responses using whole blood cells and, as predicted, observed significant increases in populations of both CD4+ and memory CD4+ CD45RO+ T-cells. Our results demonstrate the practical utility of an epitope-based design methodology – a strategy that, following further evaluation, may serve as an additional tool for the development of novel vaccine candidates against TB and other diseases.