Toll-like receptor 3 (TLR3) recognizes double-stranded RNA (dsRNA), a PAMP associated with viral infections.
The ligand of choice for TLR3 is a synthetic analog of dsRNA known as polyinosinic-polycytidylic acid (poly(I:C) or poly(rI):poly(rC)). 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, and of the annealed product, can 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, and in VacciGrade™ form (certified sterile and endotoxin-free). Additionally, we offer the synthetic dsRNA analog, polyadenylic–polyuridylic acid (poly(A:U)), which signals exclusively through TLR3.
InvivoGen’s 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.
COVID-19 related research
Type I interferons (IFNα/β) are the prototypical antiviral cytokines. Inducers of these cytokines, such as the synthetic dsRNA TLR3 agonist, Poly (I:C), can be used to study the innate immune response to SARS-CoV-2.