One of the most promising viral targets in current hepatitis B virus (HBV) drug development is the core protein due to its multiple roles in the viral life cycle. Here we investigated the differences in the mode of action and antiviral activity of representatives of six different capsid assembly modifier (CAM) scaffolds: three from the well-characterized scaffolds heteroarylpyrimidine (HAP), sulfamoylbenzamide (SBA), and phenylpropenamide (PPA), and three from novel scaffolds glyoxamide-pyrrolamide (GPA), pyrazolyl-thiazole (PT), and dibenzo-thiazepin-2-one (DBT). The target activity and antiviral efficacy of the different CAMs were tested in biochemical and cellular assays. Analytical size exclusion chromatography and transmission electron microscopy showed that only the HAP compound induced formation of aberrant non-capsid structures (class II mode of action), while the remaining CAMs did not affect capsid gross morphology (class I mode of action). Intracellular lysates from the HepAD38 cell line, inducibly replicating HBV, showed no reduction in the quantities of intracellular core protein or capsid after treatment with SBA, PPA, GPA, PT, or DBT compounds; however HAP-treatment led to a profound decrease in both. Additionally, immunofluorescence staining of compound-treated HepAD38 cells showed that all non-HAP CAMs led to a shift in the equilibrium of HBV core antigen (HBcAg) towards complete cytoplasmic staining, while the HAP induced accumulation of HBcAg aggregates in the nucleus. Our study demonstrates that the novel scaffolds GPA, PT, and DBT exhibit class I modes of action, alike SBA and PPA, whereas HAP remains the only scaffold belonging to class II inhibitors.

Persistence of HIV through integration into host DNA in CD4 + T cells presents a major barrier to virus eradication. Viral integration may be curtailed when CD8 + T cells are triggered to kill infected CD4 + T cells through recognition of histocompatibility leukocyte antigen (HLA) class I-bound peptides derived from incoming virions. However, this has been reported only in individuals with ''beneficial'' HLA alleles that are associated with superior HIV control. Through interrogation of the pre-integration immunopeptidome, we obtain proof of early presentation of a virion-derived HLA-A*02:01-restricted epitope, FLGKIWPSH (FH9), located in Gag Spacer Peptide 2 (SP2). FH9-specific CD8 + T cell responses are detectable in individuals with primary HIV infection and eliminate HIV-infected CD4 + T cells prior to virus production in vitro. Our data show that non-beneficial HLA class I alleles can elicit an effective antiviral response through early presentation of HIV virion-derived epitopes and also demonstrate the importance of SP2 as an immune target.

A fully automated microfluidic system was developed to screen for novel anti-HBV capsid assembly modulators. High-resolution dose–response curves were generated using convection-dominated Taylor–Aris dispersion of the screening compounds.

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