The overexpression of genes related to TNF-alpha signalling via NF-κB, IL-6/JAK/STAT3 signalling, IL-2/STAT5 signalling, IFN-γ and IFN-α responses in caruncles demonstrates the activation of a strong proinflammatory response after infection with the high-virulence isolate, which was not observed in heifers infected with the low-virulence isolate. This evidence concerns the gene IFNA1 and infection.