Unlike infection with attenuated strains of Yp, infection of mice and brown Norway rats with wild-type Yp suppresses several genes including genes for antigen processing and presentation, T-cell receptor (TCR)-signaling, NF-kB signaling, and natural killer (NK) cell function.39 The length of time after infection with Yp or stage of disease affects gene expression, with genes for Th1 immune response induced only at the initial or the recovery stage.39,40 To our knowledge, there are no host transcriptomics studies following vaccination with F1/V subunit vaccine. The gene discussed is NFKB1; the disease is infection.