Increased type I interferon (IFN) levels in the CNS after IAV infection might have contributed to some level of protection towards SFV infection in the CNS, suggesting that early control of SFV replication in the CNS during IAV→SFV infection led to reduced adaptive response, given the lower number of CD8+ T cells recruited to the brain in IAV→SFV infection. This evidence concerns the gene CD8A and infection.