Figure 6

Comparative reactivity of N from various PRRSV strains with the mAb SDOW17. The PRRSV N genes from genotype 1 PRRSV strains of different subtypes (¹ = classical subtype 1, ^1′ = Russian subtype 1, ² = subtype 2, ³ = subtype 3) with an alanine (A), a valine (B), a serine (C), or a threonine (D) at position 90 were cloned in pcDNA6/V5-His and expressed in BHK-21 cells. N expression was monitored 24 h after lipofection by flow cytometry using the SDOW17 and SR30 mAbs. The gate of N-positive cells was determined according to the density plot obtained with the cells transfected with the empty plasmid, pCDNA6-Δ (E). The percentage of SDOW17 reactivity compared with the SR30 reactivity is indicated for each SDOW17 panel (A–D). The mean values from 2 independent experiments performed in triplicate are plotted, with error bars showing the standard deviation and with the amino acid at position 90 shown at the bottom of each bar (F). The N proteins of the different strains were grouped according to the ratio of SDOW17 to SR30 detection (% of reactivity). Black, light grey and dark grey bars represent the strains with less than 25%, between 25 and 75%, and more than 75% N detection by SDOW17 versus SR30, respectively. The differences between groups were assessed statistically by the Mann–Whitney U test (*p < 0.05; **p < 0.01).