Porcine TLR2 and TLR6: identification and their involvement in Mycoplasma hyopneumoniae infection.

We successfully cloned and sequenced porcine toll-like receptor (TLR2) and TLR6 cDNA from porcine alveolar macrophages stimulated with 10 microg/ml lipopolysaccharide (LPS). The open reading frames (ORFs) of the porcine TLR2 and TLR6 cDNA were shown to be 2358 and 2391 bp in length and to encode 785 and 796 amino acids, respectively. The predicted amino acid sequence of porcine TLR2 was 72.3% homologous to human TLR2 and 61.0% homologous to murine TLR2. That of porcine TLR6 was 74.4% homologous to human TLR6 and 66.1% homologous to murine TLR6. Porcine TLR2 and TLR6 genes were both mapped to porcine chromosome 8 (TLR2: SSC8q21.1 --> 21.5; TLR6: SSC8p11.1 --> p21.1) by fluorescence in situ hybridization (FISH) and radiation hybrid mapping. Western blot analysis confirmed that TLR2 and TLR6 proteins were both expressed in porcine alveolar macrophages. Further, antiporcine TLR2 and TLR6 antibodies synergistically blocked tumor necrosis factor-alpha (TNF-alpha) production by porcine alveolar macrophages stimulated with Mycoplasma hyopneumoniae. These results indicated that both TLR2 and TLR6 are important in the recognition of M. hyopneumoniae in porcine alveolar macrophages and will be useful in understanding innate immunity against M. hyopneumoniae.