Tuberculosis kills more people than any other infection in the world. There is currently no vaccine that can prevent infection with Mycobacterium tuberculosis (Mtb), the causative bacterial pathogen. In order to rationally develop an effective vaccine, it will be important to identify which of the >4000 genes in the Mtb genome encode proteins (antigens) likely to be recognized by host cells of the adaptive immune system, triggering a protective anti-bacterial response. To identify these antigens in an unbiased and high-throughput way, these researchers employ a two-pronged approach.
- The first approach uses a mycobacterial genetic transposon mutagenesis screen to identify mutations in genes that confer a selective advantage in the face of protective immune pressure. The researchers use Transit software to analyze Tn Seq results to identify the genes with over-represented mutations in the context of immune vs naive mice. They will subsequently experimentally validate the candidate antigens by synthesizing peptide libraries from these genes and determining whether these trigger adaptive immune responses in cells from Mtb-infected mice.
- The second approach is a bioinformatic/computational approach to predicting amino acid sequences in the Mtb proteome that are likely to be "epitopes", specific targets of adaptive immune cells, such as T or B cells. There are several alogrithms available that scan protein databases to identify 10-20 amino acid peptide sequences. An advanced version of this epitope prediction software known as BOTA was recently published. The researchers intend to apply the BOTA software to the Mtb proteome to identify the sequences most likely to be epitopes in the context of mouse infection. They will similarly experimentally validate our candidates in vivo as described above.
By using these two orthogonal approaches and focusing on hits identified by both, the researchers aim to discover new antigenic targets of the adaptive immune repsonse in TB, that may be further explored as potential candidates for a new TB vaccine.