Flunarizine prevents hepatitis C virus membrane fusion in a genotype-dependent manner by targeting the potential fusion peptide within E1.

UNLABELLED: To explore mechanisms of hepatitis C viral (HCV) replication we screened a compound library including licensed drugs. Flunarizine, a diphenylmethylpiperazine used to treat migraine, inhibited HCV cell entry in vitro and in vivo in a genotype-dependent fashion. Analysis of mosaic viruses between susceptible and resistant strains revealed that E1 and E2 glycoproteins confer susceptibility to flunarizine. Time of addition experiments and single particle tracking of HCV demonstrated that flunarizine specifically prevents membrane fusion. Related phenothiazines and pimozide also inhibited HCV infection and preferentially targeted HCV genotype 2 viruses. However, phenothiazines and pimozide exhibited improved genotype coverage including the difficult to treat genotype 3. Flunarizine-resistant HCV carried mutations within the alleged fusion peptide and displayed cross-resistance to these compounds, indicating that these drugs have a common mode of action. CONCLUSION: These observations reveal novel details about HCV membrane fusion; moreover, flunarizine and related compounds represent first-in-class HCV fusion inhibitors that merit consideration for repurposing as a cost-effective component of HCV combination therapies.

OmpA-mediated rickettsial adherence to and invasion of human endothelial cells is dependent upon interaction with α2ß1 integrin.

Rickettsia conorii, a member of the spotted fever group (SFG) of the genus Rickettsia and causative agent of Mediterranean spotted fever, is an obligate intracellular pathogen capable of infecting various mammalian cell types. SFG rickettsiae express two major immunodominant surface cell antigen (Sca) proteins, OmpB (Sca5) and OmpA (Sca0). While OmpB-mediated entry has been characterized, the contribution of OmpA has not been well defined. Here we show OmpA expression in Escherichia coli is sufficient to mediate adherence to and invasion of non-phagocytic human endothelial cells. A recombinant soluble C-terminal OmpA protein domain (954-1735) with predicted structural homology to the Bordetella pertussis pertactin protein binds mammalian cells and perturbs R. conorii invasion by interacting with several mammalian proteins including ß1 integrin. Using functional blocking antibodies, small interfering RNA transfection, and mouse embryonic fibroblast cell lines, we illustrate the contribution of α2ß1 integrin as a mammalian ligand involved in R. conorii invasion of primary endothelial cells. We further demonstrate that OmpA-mediated attachment to mammalian cells is in part dependent on a conserved non-continuous RGD motif present in a predicted C-terminal 'pertactin' domain in OmpA.Our results demonstrate that multiple adhesin-receptor pairs are sufficient in mediating efficient bacterial invasion of R. conorii.