RELA and infection: Preliminary studies in calves with the relA and pknG deletion mutants (ΔrelA and ΔpknG) revealed immunization with ΔrelA elicited an immune response that cleared infection, as assessed by screening tissues for the presence of ΔrelA, whereas, immunization with pknG elicited an immune response that only impaired establishment of an infection with ΔpknG (Park et al., 2011).