Neutralization tests
Considering the S protein of CoVs can induce neutralizing antibodiesin vivo (Wen et al., 2018), we attempted to analyze the relationship between OD450nmvalues tested by S-iELISA and neutralization titers. As shown in Fig 6, 6 ELISA-positive sera had different level of virus neutralization activity and the higher OD450nm value and the higher neutralization antibody, indicating that OD450nm values of pig serum might positively correlated with virus neutralization activity.