Polymorphisms In Pulmonary Innate Immune System Genes Of Swine

Modern pigs are unusually susceptible to severe infectious pneumonia. We hypothesize that single nucleotide polymorphisms (SNPs) in innate immune system genes impair resistance to infection or promote injurious inflammatory responses in swine. The objective of this study was to characterize SNPs that code for amino acid substitutions in porcine surfactant protein-A and -D (SP-A, SP-D), complement component C3d (C3d), and Toll-like receptor 2 (TLR-2). For each gene, RT-PCR products that cover the entire coding region were subjected to single-strand conformational polymorphism (SSCP) analysis. RT-PCR was performed on total RNA extracted from the lungs of randomly chosen diseased pigs submitted to the Animal Health Laboratory, University of Guelph, for diagnostic investigation. Pigs were screened for SNPs by comparing silver-stained banding patterns of digested, single-stranded RT-PCR products separated by SSCP gel electrophoresis. Several different banding patterns were observed in digests of SP-A, SP-D and TLR-2, whereas C3d digests appeared uniform. Sequence comparisons of RT-PCR products representing different banding patterns revealed three coding SNPs in the C-type lectin domain of SP-A. The C-type lectin domain of SP-A has an important role in binding microbial surface carbohydrates and these results suggest that pigs may differ in their innate ability to recognize and defend against some respiratory pathogens. Supported by OMAF, Ontario Pork, and the Ontario Veterinary College