Furthermore, the use of a Lm vector lacking fosX such as Lm3Dx allows the complete abandonment of exogenous antibiotic resistance genes during cloning with recombination plasmids containing fosX. Secondly, we aimed to ensure insertion of the sag1 gene into the actA locus, thus allowing for strong antigen expression in vivo to be regulated by the natural actA promotor, which is strongly activated by prfA during in vivo infection (Radoshevich and Cossart, 2018). The gene discussed is ACTA1; the disease is infection.