Low titer CC-RIX mice with superior virologic containment at day 2 post-infection had a higher mean frequency of CD44+ CD4 and CD8 T cells in the spleen prior to infection (Fig 2A and 2B), in addition to an increased proportion of CD4 T cells that express Ki67 (Fig 2C), which signals recent proliferation. The gene discussed is CD4; the disease is infection.