Fig. 2.

Detection of PRRSV-specific antibodies in serum by ELISA. Positive responses were classified as the S/P ratio of ≥0.4 (horizontal red line). Serum samples were collected from the pigs at DPFV 0 (A), 7 (B), 14 (C), 21 (D), 28 (E), 35 (F), 42 (G), 49 (H) 51 (I), 53 (J), 55 (K), 57 (L), 59 (M), 61 (N) and 63 (O). *First vaccination; **second vaccination for groups 3 and 4; ***second vaccination for groups 5 and 6; ****third vaccination for groups 3 and 4; *****challenge. Data are mean ± SEM titer of 5 or 10 pigs in each group. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)