GENETIC AND BIOLOGICAL DETERMINANTS OF RESPIRATORY DISEASES OF RUMINANTS
Location: Genetics, Breeding, & Animal Health
Title: Reduced OPP susceptibility in naturally exposed lambs with homozygous TMEM154 K35 genotypes
Submitted to: American Association for Immunology
Publication Type: Abstract Only
Publication Acceptance Date: February 24, 2012
Publication Date: May 4, 2012
Citation: Chitko Mckown, C.G., Leymaster, K.A., Heaton, M.P., Clawson, M.L., Harhay, G.P. 2012. Reduced OPP susceptibility in naturally exposed lambs with homozygous TMEM154 K35 genotypes [abstract]. Immunology 2012. The 99th Annual Meeting of the American Association for Immunology, May 4-8, 2012, Boston, Massachusetts. Page 275. Abstract No. 170.3. Poster No. P1246.
Ovine progressive pneumonia virus (OPPV) is a small ruminant lentivirus of the retroviridae family that infects sheep worldwide. Our research group recently identified a mutation (K35) within ovine gene TMEM154 that associated with reduced susceptibility to OPPV. The ancestral state for TMEM154 is E35. The mechanism responsible for reduced OPPV susceptibility is unknown. Lambs that were homozygous K35 (n = 64), homozygous E35 (n = 58), or heterozygous E35K (n = 80) and born to OPPV sero-positive ewes were produced to test the association of E35K with OPPV susceptibility. Lambs were bled one week post-weaning and every 5 weeks thereafter to determine serological status. At 7 months of age, lambs were co-mingled with a flock of sero-positive mature ewes during a 35-day breeding season to re-expose lambs to OPPV as naturally occurs during breeding in infected flocks. Mature ewes were removed after breeding and lambs were again bled at 5-week intervals. At 7 months of age, 11% of homozygous K35 lambs were sero-positive for OPPV, compared to about 25% of lambs with one or two copies of the susceptible E35 ancestral allele. Two months after re-exposure to the infected ewes, 25% of homozygous K35 lambs were sero-positive, compared to 42% of heterozygous E35K lambs and 38% of homozygous E35 lambs. This study confirms that homozygous K35 lambs are less susceptible to OPPV infection and provides the first evidence of dominance of the E35 allele relative to K35.