Toll-like receptor 3 (TLR3) recognizes double-stranded RNA (dsRNA), a PAMP associated with viral infection. The ligand of choice for TLR3 is polyinosinic-polycytidylic acid (usually abbreviated as poly(I:C) or poly(rI):poly(rC)), a synthetic analog of dsRNA. Poly(I:C) comprises a strand of inosine poly(I) homopolymer annealed to a strand of cytidine poly(C) homopolymer. Poly(I) and poly(C) are prepared by enzymatic synthesis of IDP or CDP with polynucleotide phosphorylase (PNPase). Since each strand is synthesized enzymatically, the size of each one and of the annealed product vary significantly. InvivoGen is the only company to provide poly(I:C) in two different sizes:
• Poly(I:C) high molecular weight (HMW): average size of 1.5-8 kb.
• Poly(I:C) low molecular weight (LMW): average size of 0.2-1 kb
InvivoGen also provides poly(I:C) in biotin and fluorescently-labeled forms, in VacciGradeTM form (certified sterile and endotoxin-free per LAL validation), plus polyadenylic–polyuridylic acid (usually abbreviated poly(A:U)), a synthetic dsRNA analog that signals exclusively through TLR3.
InvivoGen synthetic dsRNA analogs are functionally validated for TLR3 potency using HEK-Blue™ TLR3 Cells and are certified to be free of microbial contaminants (e.g. endotoxin or bacterial-membrane components) that can activate other TLR receptors, such as TLR2 or TLR4.