GBP5 and infection: The objectives of this study were to investigate: (1) mechanisms of PRRSV persistence in nursery pigs by studying the tonsil transcriptome at 42 days after infection with one of two PRRSV isolates, NVSL and KS06; (2) the effect of PRRSV level on the tonsil transcriptome at 42 dpi; and (3) the effect of genotype at a genetic marker for the GBP5 resistance gene (WUR) on the tonsil transcriptome at 42 dpi.