Therefore, we hypothesized that the high level of TNF-α and IFN-α caused by the attenuated PDCoV HNZK-02-P150 infection might activate the host immune defenses and inhibit PDCoV proliferation in the target tissues, which is consistent with the attenuated pathogenicity of PDCoV HNZK-02-P150 in piglets. Here, TNF is linked to infection.