Figure 5

Pretreatment with serine protease inhibitors reduced viral propagation in infected C57Bl/6J mice. C57BL/6J mice were pre-treated with the AEBSF and then infected intra-nasally with 2 × 10³ FFU of either the H1N1 or the H7N7 virus. Propagation of the two viruses in the lungs was measured by determining virus NP by ELISA and HA mRNA by real-time PCR. Uninfected mice were used as controls for the NP background signal (A, B). Pretreatment of C57Bl/6J mice with AEBSF prior to infection with H1N1 (A; n = 3) or H7N7 (B; n = 3) showed significant reduction (P < 0.05) in the levels of viral antigen at day 6 p.i compared to untreated infected mice (n = 3). All measurements were carried out in triplicates for two successive measurements on two independent days. Analysis of RNA extracted from lungs of C57Bl/6J mice that were treated with AEBSF prior to infection with H1N1 (C) revealed a significant drop in the levels of viral HA1 transcript by real-time PCR compared to untreated infected mice (n = 3 for each group). However, no significant differences in the levels of the HA transcripts were observed between the AEBSF-treated and the untreated H7N7-infected mice (D; n = 3 for each group). All real-time PCR measurements were carried out in triplicates in one experiment and the cycle threshold values of the triplicate measurements where similar. Mean values +/- 1 SD are represented.