An intronic polymorphism in the porcine IRF7 gene is associated with better health and immunity of the host during Sarcocystis infection, and affects interferon signalling

Summary Interferon regulatory factor 7 (IRF7), as a key regulator of type I interferon response, playsan important role during innate response against viral infection. Although well conservedacross species, the structure of IRF7 and its function during parasite infection are not welldocumented in farm animals, such as the pig. To bridge this gap, we have determined theporcine IRF7 gene structure and identified two intronic single nucleotide polymorphisms(SNPs), SNP g.748G>C and SNP g.761A>G, in commercial pig breeds. The distribution ofSNP g.761A>G in multiple breeds suggested that it was in Hardy–Weinberg equilibriumand allowed us to map it at the top of SSC2. We found that during Sarcocystis miescherianainfection, the G allele was associated with high lymphocyte levels (P G enhances the transactivation activity of IRF7, possibly by improvingIRF7 transcript splicing of intron-3. These findings would suggest that IRF7, as a tran-scriptional regulator, is involved in the defence mechanism against a larger spectrum ofpathogens, and in more host species, than initially anticipated.Keywords genetic association, innate immunity, intron, IRF7, pig, sarcosystis