To determine the PRRs and cytokine levels following the infection of the H5N6 viruses at the early stage, we further tested the expression of TLR3, TLR7, MDA5 mRNA and a set of representative cytokines in the brains and lungs of chickens at 24 h postinfection using qRT-PCR (Figure 4A,B). The gene discussed is TLR3; the disease is infection.