Compared with prototype PEDV CV777, PEDV S INDEL Iowa106 is antigenically closer to the highly virulent PEDV PC22A in the S protein-based phylogenetic tree (Fig. 3 ) and antigenic map (Fig. 4) . We reported that convalescent antisera obtained from S INDEL-infected pigs cross-reacts with the highly virulent PEDV PC22A strain in twoway CCIF and VN assays (Tables 1 and 2, Fig. 4) (Lin et al., 2015b) . However, these in vitro immunological assays only examined the IgG antibodies in serum and may not reflect lactogenic antibodies in vivo challenge conditions.