Molecular identification and functional expression of porcine Toll-like receptor (TLR) 3 and TLR7.

To investigate porcine Toll-like receptors (TLR) responding to viral pathogen associated molecular patterns, the full-length cDNA of porcine TLR3 and TLR7 were identified and characterized. Porcine TLR3 and TLR7 cDNA encode 904- and 1050-amnio-acid polypeptides, respectively. Both porcine TLR3 and TLR7 contain typical functional TLR domains and share about 80% sequence identity to other mammalian orthologues. Tissue expression profiles showed that TLR3 was highly expressed in kidney, duodenum, spleen and liver, and moderately expressed in bone marrow, lung, and skin. Conversely, TLR7 was moderately and constitutively expressed in all tissues evaluated. Stimulation of mammalian cells transfected with porcine TLR3 and TLR7 constructs with TLR3 and TLR7 agonists [poly (I:C) and imiquimod (R837), respectively], and adenovirus elicited activation of interferon regulatory factors (IRFs). These data provide molecular and functional information for porcine TLR3 and TLR7, and implicate their role in mediating immune protection against porcine viral diseases.