RESUMEN
BACKGROUND AND AIMS: Therapies for chronic hepatitis B virus (HBV) infection are urgently needed because of viral integration, persistence of viral antigen expression, inadequate HBV-specific immune responses, and treatment regimens that require lifelong adherence to suppress the virus. Immune mobilizing monoclonal T Cell receptors against virus (ImmTAV) molecules represent a therapeutic strategy combining an affinity-enhanced T Cell receptor with an anti-CD3 T Cell-activating moiety. This bispecific fusion protein redirects T cells to specifically lyse infected cells expressing the target virus-derived peptides presented by human leukocyte antigen (HLA). APPROACH AND RESULTS: ImmTAV molecules specific for HLA-A*02:01-restricted epitopes from HBV envelope, polymerase, and core antigens were engineered. The ability of ImmTAV-Env to activate and redirect polyclonal T cells toward cells containing integrated HBV and cells infected with HBV was assessed using cytokine secretion assays and imaging-based killing assays. Elimination of infected cells was further quantified using a modified fluorescent hybridization of viral RNA assay. Here, we demonstrate that picomolar concentrations of ImmTAV-Env can redirect T cells from healthy and HBV-infected donors toward hepatocellular carcinoma (HCC) cells containing integrated HBV DNA resulting in cytokine release, which could be suppressed by the addition of a corticosteroid in vitro. Importantly, ImmTAV-Env redirection of T cells induced cytolysis of antigen-positive HCC cells and cells infected with HBV in vitro, causing a reduction of hepatitis B e antigen and specific loss of cells expressing viral RNA. CONCLUSIONS: The ImmTAV platform has the potential to enable the elimination of infected cells by redirecting endogenous non-HBV-specific T cells, bypassing exhausted HBV-specific T cells. This represents a promising therapeutic option in the treatment of chronic hepatitis B, with our lead candidate now entering trials.
Asunto(s)
Virus de la Hepatitis B/inmunología , Hepatitis B Crónica/tratamiento farmacológico , Receptores de Antígenos de Linfocitos T/uso terapéutico , Proteínas Recombinantes de Fusión/farmacología , Linfocitos T/efectos de los fármacos , Anticuerpos Monoclonales/genética , Anticuerpos Monoclonales/inmunología , Anticuerpos Monoclonales/farmacología , Anticuerpos Monoclonales/uso terapéutico , Complejo CD3/antagonistas & inhibidores , Línea Celular Tumoral , Epítopos/inmunología , Antígeno HLA-A2/inmunología , Antígenos de Superficie de la Hepatitis B/inmunología , Virus de la Hepatitis B/aislamiento & purificación , Hepatitis B Crónica/inmunología , Hepatitis B Crónica/virología , Hepatocitos , Humanos , Inmunoconjugados/genética , Inmunoconjugados/inmunología , Inmunoconjugados/farmacología , Inmunoconjugados/uso terapéutico , Activación de Linfocitos/efectos de los fármacos , Cultivo Primario de Células , Receptores de Antígenos de Linfocitos T/genética , Receptores de Antígenos de Linfocitos T/inmunología , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/inmunología , Proteínas Recombinantes de Fusión/uso terapéutico , Linfocitos T/inmunologíaRESUMEN
The Mre11-Rad50 nuclease-ATPase is an evolutionarily conserved multifunctional DNA double-strand break (DSB) repair factor. Mre11-Rad50's mechanism in the processing, tethering, and signaling of DSBs is unclear, in part because we lack a structural framework for its interaction with DNA in different functional states. We determined the crystal structure of Thermotoga maritima Rad50(NBD) (nucleotide-binding domain) in complex with Mre11(HLH) (helix-loop-helix domain), AMPPNP, and double-stranded DNA. DNA binds between both coiled-coil domains of the Rad50 dimer with main interactions to a strand-loop-helix motif on the NBD. Our analysis suggests that this motif on Rad50 does not directly recognize DNA ends and binds internal sites on DNA. Functional studies reveal that DNA binding to Rad50 is not critical for DNA double-strand break repair but is important for telomere maintenance. In summary, we provide a structural framework for DNA binding to Rad50 in the ATP-bound state.
Asunto(s)
Proteínas Bacterianas/química , Enzimas Reparadoras del ADN/química , Proteínas de Unión al ADN/química , ADN/química , Modelos Moleculares , Complejos Multiproteicos/química , Thermotoga maritima/enzimología , Secuencia de Aminoácidos , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Secuencia de Bases , Sitios de Unión/genética , Cristalografía , ADN/metabolismo , Enzimas Reparadoras del ADN/genética , Enzimas Reparadoras del ADN/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Datos de Secuencia Molecular , Conformación Proteica , Estructura Terciaria de Proteína , Saccharomyces cerevisiae , Alineación de Secuencia , Análisis de Secuencia de ADN , Homeostasis del Telómero/genéticaRESUMEN
Nuclear actin-related proteins (Arps) are subunits of several chromatin remodelers, but their molecular functions within these complexes are unclear. We report the crystal structure of the INO80 complex subunit Arp8 in its ATP-bound form. Human Arp8 has several insertions in the conserved actin fold that explain its inability to polymerize. Most remarkably, one insertion wraps over the active site cleft and appears to rigidify the domain architecture, while active site features shared with actin suggest an allosterically controlled ATPase activity. Quantitative binding studies with nucleosomes and histone complexes reveal that Arp8 and the Arp8-Arp4-actin-HSA sub-complex of INO80 strongly prefer nucleosomes and H3-H4 tetramers over H2A-H2B dimers, suggesting that Arp8 functions as a nucleosome recognition module. In contrast, Arp4 prefers free (H3-H4)(2) over nucleosomes and may serve remodelers through binding to (dis)assembly intermediates in the remodeling reaction.