We first examined the expression level of PLSCR1 in the tissues of C57BL/6 mice by performing western blot. The results show that PLSCR1 is ubiquitously expressed in various tissues examined and has relatively high expression level in lung, the target organ of influenza virus (Figure 1C). We then used 103 pfu H1N1 SIV to infect C57BL/6J mice intranasally and examined PLSCR1 levels at different time points post infection. The results show that PLSCR1 expression is markedly decreased when examined at 1 day post infection (dpi) (Figure 1D). PLSCR1 expression continues to decrease to less than 5% at 5 dpi, then gradually returns to the normal level by 14 dpi (Figure 1D and 1E). This dynamic change of PLSCR1 expression suggests that PLSCR1 might play an essential role in SIV infection in vivo .Figure 1. PLSCR1 Expression after H1N1 SIV Infection. (A)The similarity of PLSCR1 between different species.(B)The identity percentage of nucleoprotein of influenza virus between the isolated strain from the diseased pigs and human.(C)Western blots showed that PLSCR1 expression in various tissues of C57BL/6 mice on day 42.(D)PLSCR1 and ILDR1protein levels in lung are modulated after swine influenza A virus (SIV) infection. The lungs were dissected from C57BL6/J mice that were either mock- or SIV-infected at multiple days p.i. as indicated. (E and F)The area of the PLSCR1 and ILDR1 peak, in relation to the standard curve, was determined using ImageJ software. Bars represent mean±s.d. *P<0.05**P < 0.01;***P < 0.001.