Discordant biological and toxicological species responses to TLR3 activation.
Toll-like receptors (TLRs) are highly conserved type 1 membrane proteins that initiate a multiplicity of transient gene transcriptions, resulting in innate and adaptive immune responses. These essential immune responses are triggered by common TLR pattern recognition receptors of microbial products expressed through the cytoplasmic carboxy-terminal Toll/IL-1 domain. Toll/IL-1 adapter protein cascades are induced by an activated Toll/IL-1 to induce transient transcription responses. All TLRs, with the exception of TLR3, use an MyD88 adapter to Toll/IL-1 to initiate a proinflammatory cascade. TLR3 uses the toll receptor 3/4 induction factor adapter to initiate a different cytosolic adapter cascade with double-stranded RNA agonists. This non-MyD88 pathway induces both NF-κB and type 1 interferon responses. By using a TLR3-restricted double-stranded RNA agonist, rintatolimod, we demonstrate significant unexpected differences in toxic responses between rats and primates. The mechanism of this differential response is consistent with a relative down-regulation of the NF-κB inflammatory cytokine induction pathway in the cynomolgus monkey and humans, but not observed systemically in rat. Our findings suggest evaluation of TLR3 agonists in drug therapy.
Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee. Electronic address: bill.mitchell@vanderbilt.edu.
William M
WM
Mitchell
AIT Strategies, Franconia, New Hampshire.
Christopher F
CF
Nicodemus
Hemispherx BioPharma, Inc., Philadelphia, Pennsylvania.
William A
WA
Carter
Hemispherx BioPharma, Inc., Philadelphia, Pennsylvania.
Joseph C
JC
Horvath
Hemispherx BioPharma, Inc., Philadelphia, Pennsylvania.
David R
DR
Strayer
D000595:Amino Acid Sequence; D000818:Animals; D004285:Dogs; D015673:Fatigue Syndrome, Chronic / Q000188:drug therapy; D006801:Humans; D007249:Inflammation / Q000276:immunology / Q000378:metabolism*; D008252:Macaca fascicularis; D020714:Maximum Tolerated Dose; D008969:Molecular Sequence Data; D011070:Poly I-C / Q000494:pharmacology*; D011072:Poly U / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D013045:Species Specificity; D051196:Toll-Like Receptor 3 / Q000037:antagonists & inhibitors*
D051196:Toll-Like Receptor 3; D011072:Poly U; C047490:poly(I).poly(c12,U); D011070:Poly I-C