Immunostaining for the viral spike protein further confirmed that pretreatment with the ApoE neutralizing antibody could protect cells from Delta virus infection, as revealed by the reduced percentage of cells infected by the SARS‐CoV‐2 Delta strain in both hACE2‐HEK cells (Figure 4G) and Calu‐3 cells (Figure 4H) pretreated with the ApoE neutralizing antibody, compared with that in cells pretreated with a control IgG. Here, APOE is linked to viral infectious disease.