A standardized BioBrick toolbox for the assembly of sequences in mycobacteria

For more than 25 years, recombinant Mycobacterium bovis BCG has been genetically engineered for use as a vehicle for antigen expression and immunomodulation, typically through introducing or deleting a gene from BCG genome. However, BCG transformation efficacy is still unpredictable, and cloning and expression of sequences from mycobacteria is difficult to predict due to the lack of standardization. To overcome such limitations, we have employed the BioBrick format to construct a toolbox of several mycobacterial parts, including coding sequences, reporter genes, selective markers, promoters, and other regulatory sequences. Additionally, we have developed and characterized BioBrick-compatible episomal vectors that are able to replicate in M. bovis BCG to enable expression of heterologous antigens. The availability of a BCG Biobrick toolbox will enable any coding sequence to be optimally expressed in BCG. We believe that this mycobacterial toolbox represents a standardized and useful kit to enhance the efficacy and use of recombinant BCG.