The Imidazoquinoline Toll-Like Receptor-7/8 Agonist Hybrid-2 Potently Induces Cytokine Production by Human Newborn and Adult Leukocytes

Ganapathi, Lakshmivan Haren, SimonDowling, DavidBergelson, IlanaShukla, Nikunj M.Malladi, Subbalakshmi S.Balakrishna, RajalakshmiTanji, HiromiOhto, UmeharuShimizu, ToshiyukiDavid, Sunil A.Levy, Ofer2015-09-012015Ganapathi, L., S. Van Haren, D. J. Dowling, I. Bergelson, N. M. Shukla, S. S. Malladi, R. Balakrishna, et al. 2015. “The Imidazoquinoline Toll-Like Receptor-7/8 Agonist Hybrid-2 Potently Induces Cytokine Production by Human Newborn and Adult Leukocytes.” PLoS ONE 10 (8): e0134640. doi:10.1371/journal.pone.0134640. http://dx.doi.org/10.1371/journal.pone.0134640.1932-6203http://nrs.harvard.edu/urn-3:HUL.InstRepos:21461918Background: Newborns and young infants are at higher risk for infections than adults, and manifest suboptimal vaccine responses, motivating a search for novel immunomodulators and/or vaccine adjuvants effective in early life. In contrast to most TLR agonists (TLRA), TLR8 agonists such as imidazoquinolines (IMQs) induce adult-level Th1-polarizing cytokine production from human neonatal cord blood monocytes and are candidate early life adjuvants. We assessed whether TLR8-activating IMQ congeners may differ in potency and efficacy in inducing neonatal cytokine production in vitro, comparing the novel TLR7/8-activating IMQ analogues Hybrid-2, Meta-amine, and Para-amine to the benchmark IMQ resiquimod (R848). Methods: TLRA-induced NF-κB activation was measured in TLR-transfected HEK cells. Cytokine production in human newborn cord and adult peripheral blood and in monocyte-derived dendritic cell cultures were measured by ELISA and multiplex assays. X-ray crystallography characterized the interaction of human TLR8 with Hybrid-2. Results: Hybrid-2 selectively activated both TLR7 and 8 and was more potent than R848 in inducing adult-like levels of TNF-α, and IL-1β. Consistent with its relatively high in vitro activity, crystallographic studies suggest that absence in Hybrid-2 of an ether oxygen of the C2-ethoxymethyl substituent, which can engage in unfavorable electrostatic and/or dipolar interactions with the carbonyl oxygen of Gly572 in human TLR8, may confer greater efficacy and potency compared to R848. Conclusions: Hybrid-2 is a selective and potent TLR7/8 agonist that is a candidate adjuvant for early life immunization.en-USThe Imidazoquinoline Toll-Like Receptor-7/8 Agonist Hybrid-2 Potently Induces Cytokine Production by Human Newborn and Adult LeukocytesJournal Article2015-09-0110.1371/journal.pone.0134640