Figure 1.

Sequence analysis and in vitro characterization of recombinant H7N1 viruses.

Note: (a) Sequence analysis of NS1 of H7N1 from turkeys (n = 65) and chickens (n = 28) in 1999–2000 deposited in GISAID (retrieval date 16-01-2024). Variations in NS1 length are shown as number and percentage of total sequences analysed in different years. Sequence analysis was performed using Geneious Prime. (b) Alignment and amino acid differences of the NS1 protein of the viruses used for this study. (c) Turkey embryonic kidney (TEK) cells were infected at a MOI 0.001 and virus titres were determined at 1, 8, 24, 48 and 72 h post infection (hpi) by plaque assay performed on MDCK II cells. Titres were calculated as pfu/ml and are presented as the mean and standard deviation of three independent experiments performed in duplicate. Data were analysed by one-way ANOVA with post hoc Tukey test. Asterisks indicate significant differences (*= p < 0.05, **= p < 0.01, ***= p < 0.001, ****= p < 0.0001); ns = no significant differences. (d) NS1 protein was detected after infection of TEK cells at a MOI of 0.1 for 24 h at 37°C. Detection was performed using rabbit polyclonal sera (D. Marc, INRAE, Nouzilly, France) and ECL substrate. The Western blot image was acquired using Quantity One software version 4.4 (Biorad, Germany). (e) Image J was used to calculate NS1 expression levels and data are presented as NS1/NP ratio.