Fig 2.

PB1-F2 expression is differentially regulated in a strain-specific manner. (A) MDCK cells were infected with OH07, rMx/MOM, or rPR8 virus at an MOI of 2. At the indicated times p.i., the cells were immunostained with NP and PB1-F2 antibodies, followed by Alexa Fluor-conjugated secondary antibodies. (B) MDCK, A549, and PK-15 cells were infected with OH07, rMx/MOM, or rPR8 virus at an MOI of 2, and at 12 h p.i., the cells were immunostained for NP and PB1-F2. The percentage of NP-expressing cells also expressing PB1-F2 was determined and plotted on a graph. Statistically significant groups (P < 0.05) compared to PR8-infected samples are denoted with asterisks. The error bars indicate standard deviations. (C) Sample lysates (400 μg) from mock- or pOH07/PB1-F2/3×FLAG-transfected BHK-T7 cells and OH07-infected (MOI = 5; 12 h p.i.) MDCK cells (left) or serial dilutions of pOH07/PB1-F2/pET21 bacterially expressed purified protein ranging from 25 to 400 ng (right) were separated on SDS-PAGE, transferred to nitrocellulose membranes, and immunoblotted with antibodies against OH07 PB1-F2 or β-actin, as indicated, followed by AP-conjugated secondary antibodies.