Submitted to: Porcine Reproductive and Respiratory Syndrome International Symposium
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2005
Publication Date: 12/1/2005
Citation: Lunney, J.K., Petry, D., Boyd, P., Kuhar, D.J., Blankenship, E., Johnson, R. 2005. Differential immunity in pigs with high and low responses to prrsv. In: Proceedings of the Porcine Reproductive and Respiratory Syndrome International Symposium, December 2-3, 2005, St. Louis, MO. #44. Available: http://www.prrssymposium.org/Documents/2005%20International%20PRRS%20Symposium%20-%20Proceedings.pdf
Technical Abstract: Duroc/Hampshire (HD) crossbred pigs (100) and NE Index line (I) pigs (100) were infected with porcine reproductive and respiratory syndrome virus (PRRSv) and evaluated for resistance/susceptibility. Controls (100/line) were uninfected littermates to each infected pig. Viremia (V), weight change (WT'), and rectal temperature at 0, 4, 7, and 14 days post-infection (dpi) were recorded. Lung, bronchial lymph node (BLN), and blood were collected at necropsy (14dpi). Line differences, and line by treatment interactions across days, indicated genetic variation in responses to PRRSv (Petry et al., 2005). Principal component analyses were used to rank pigs for phenotypic response to PRRSv. Pigs classed as low (L) responders had high WT', low V, and few lung lesions; high (H) responders had low WT', high V, and many lesions. I pigs had a quicker response to PRRSv than HD pigs as indicated by the differences in viremia in L class pigs. RNA from frozen lung and BLN tissue of the 7 highest and lowest responders per line, and their littermates, were extracted. cDNA expression of 12 specific innate and Th1 immune markers was evaluated in a 2*2*2 factorial design. HD pigs had a greater magnitude of difference in expression than I pigs. Significant under-expression of L pigs for certain immune genes, relative to controls, was detected in lung and BLN, particularly in I. Serum levels of the immune cytokines affirmed the lung differences. Low pre-infection serum levels of the innate cytokine, interleukin-8, were significantly associated with PRRSV resistant, L pigs. Following infection, low expression of interferon-gamma in cDNA and in serum was also correlated with resistance. These data are critical for genetic association studies to fine map candidate genes and to determine causative alleles.