TNF and hepatitis A virus infection: Activation of the TLR4-myeloid differentiation primary response gene 88 (MyD88)-NFκB signaling pathway, an important pathway associated with the inflammatory response and hepatitis/hepatitis fibrosis, can lead to the release of downstream inflammatory factors and induce the production of interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-α.