Previously, in our design of a novel TB booster vaccine, we employed a highly attenuated replicating bacterium as a vaccine vector, Lm ΔactA ΔinlB prfA*, a Listeria monocytogenes with deletions in two major virulence genes (actA and inlB) and a single amino acid substitution (G155S) in PrfA (positive regulatory factor A) resulting in constitutive overexpression of PrfA and PrfA-dependent genes, a modification exploited to enhanced vaccine efficacy (17). This evidence concerns the gene ACTA1 and tuberculosis.