Fig. 1

The relationship between tonsil and serum viral level in pigs infected with the NVSL or KS06 PRRS virus isolate. a Serum viral load, calculated as area under the Wood’s curve from the day of infection until euthanasia at 42 days post infection (dpi), compared to viral level in tonsil at 42 dpi. Solid black symbols indicate samples selected for RNA-sequencing and NanoString gene expression analyses (except one sample noted in red, which was used only for RNA-seq). The correlation of tonsil viral level at 42 dpi with VLTotal was 0.14 (p = 0.01). b Serum viremia level at 42 dpi compared to tonsil viral level at 42 dpi. Of the 337 pigs, 168 had a non-zero tonsil viral level (non-zero on the x axis), although they had non-detectable levels of serum viremia at 42 dpi (zero on the y axis), 80.9% of the NVSL-infected pigs and 22.8% of the KS06-infected pigs. A total of 53 tonsil samples (shown as “Selected”) were selected for gene expression analyses based on high or low PRRSV level (at least one standard deviation from the mean) in the tonsil (High and Low-TVclass) and RIN scores of the extracted RNA