Mice with impairments in multiple PRR pathways, such as Trif–/– (TIR-domain-containing adapter-inducing interferon-β; selective TLR3 and TLR4 adaptor; [38]), Myd88–/–Trif–/– (all TLR signalling affected; [38]), Myd88–/–Mavs–/– [39], Tlr7–/–Mavs–/– [32] or Tlr3–/–Tlr7–/– [38], are more susceptible to PR8 infection with reduced anti-viral responses and increased viral loads. The gene discussed is MYD88; the disease is infection.