loxoribine and gardiquimod

Norovirus infections are a significant health and economic burden globally, accounting for hundreds of millions of cases of acute gastroenteritis every year. In the absence of an approved norovirus vaccine, there is an urgent need to develop antivirals to treat chronic infections and provide prophylactic therapy to limit viral spread during epidemics and pandemics. Toll-like receptor (TLR) agonists have been explored widely for their antiviral potential, and several are progressing through clinical trials for the treatment of human immunodeficiency virus (HIV) and hepatitis B virus (HBV) and as adjuvants for norovirus viruslike particle (VLP) vaccines. However, norovirus therapies in development are largely direct-acting antivirals (DAAs) with fewer compounds that target the host. Our aim was to assess the antiviral potential of TLR7 agonist immunomodulators on norovirus infection using the murine norovirus (MNV) and human Norwalk replicon models. TLR7 agonists R-848, Gardiquimod, GS-9620, R-837, and loxoribine were screened using a plaque reduction assay, and each displayed inhibition of MNV replication (50% effective concentrations [EC

Topics: Aminoquinolines; Animals; Antiviral Agents; Caliciviridae Infections; Cell Line; Guanosine; Humans; Imidazoles; Imiquimod; Mice; Pteridines; RAW 264.7 Cells; Toll-Like Receptor 7; Virus Replication

Using a yeast-based assay, a previously unsuspected antiprion activity was found for imiquimod (IQ), a potent Toll-like receptor 7 (TLR7) agonist already used for clinical applications. The antiprion activity of IQ was first detected against yeast prions [PSI (+) ] and [URE3], and then against mammalian prion both ex vivo in a cell-based assay and in vivo in a transgenic mouse model for prion diseases. In order to facilitate structure-activity relationship studies, we conducted a new synthetic pathway which provides a more efficient means of producing new IQ chemical derivatives, the activity of which was tested against both yeast and mammalian prions. The comparable antiprion activity of IQ and its chemical derivatives in the above life forms further emphasizes the conservation of prion controlling mechanisms throughout evolution. Interestingly, this study also demonstrated that the antiprion activity of IQ and IQ-derived compounds is independent from their ability to stimulate TLRs. Furthermore, we found that IQ and its active chemical derivatives inhibit the protein folding activity of the ribosome (PFAR) in vitro.

Topics: Aminoquinolines; Animals; Cell Line; Drug Evaluation, Preclinical; Glutathione Peroxidase; Guanosine; Humans; Imidazoles; Imiquimod; Membrane Glycoproteins; Mice; Peptide Termination Factors; Prion Diseases; Prions; Protein Folding; PrPSc Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Structure-Activity Relationship; Toll-Like Receptor 7; Toll-Like Receptor 8

Imidazoquinolone compounds, such as resiquimod are Toll-like receptor (TLR) 7/8 ligands representing novel immune response modifiers undergoing clinical testing. Resiquimod has been reported to modulate conventional human monocyte-derived DC (moDC) differentiation, but the role of TLR7 and TLR8 is unclear. We directly dissected the TLR7- and TLR8-dependency by employing selective TLR7 ligands and resiquimod-coculture experiments with inhibitory oligonucleotides (iODN) suppressing TLR7, TLR7+8 or TLR7+8+9. Selective TLR7 ligands did not affect conventional moDC differentiation as analyzed by CD14/CD1a expression. iODN experiments confirmed that resiquimod's effects during DC differentiation were antagonized only with TLR8 iODNs. Direct comparison of resiquimod DC with TLR7- and control-DC revealed significantly higher T-cell costimulatory molecule and MHC class II expression. Resiquimod DC promoted significantly stronger allogeneic T-cell proliferation and stronger naïve CD4(+) T-cell proliferation. These results indicate the relevance of TLR8 for human monocyte-derived DC differentiation and maturation and may be relevant for clinical trials employing resiquimod.

Topics: Aminoquinolines; Base Sequence; Cell Differentiation; Cell Proliferation; Dendritic Cells; Guanosine; HEK293 Cells; HLA-D Antigens; Humans; Imidazoles; In Vitro Techniques; Interleukin-3 Receptor alpha Subunit; Ligands; Monocytes; Oligodeoxyribonucleotides, Antisense; T-Lymphocytes, Helper-Inducer; Toll-Like Receptor 7; Toll-Like Receptor 8; Toll-Like Receptor 9; Transfection