Viremia of pigs immunized with recombinant adenoviruses and challenged with the PRRSV FMV09-1155278 strain. Pigs were challenged intranasally with 2 × 105 TCID50 of PRRSV FMV09-1155278 strain at day 49 post primary immunization. The PRRSV loads were determined at 0, 5, 7 and 10 days post-challenge by quantitative real-time RT-PCR and expressed as TCID50/mL. Data are expressed as the mean + SEM (n = 6 pigs for all groups but the M-GP5m group with 5 pigs). When 2 sets of data are labeled with superscripts of different letters at the same sampling day, it indicates that these sets of data are statistically different (P < 0.05).