Although low doses of LCMV-DOC (2×102–2×103 PFU) induce potent CD8+ T cell-mediated immunity and are cleared in immunocompetent hosts, infection with intermediate and high doses (2×104–2×106 PFU) results in virus persistence due to the exhaustion of the virus-specific CD8+ T cell response [30], [31]. The gene discussed is CD8A; the disease is infection.