title: Optimized Replicating Renilla Luciferase Reporter HIV-1 Utilizing Novel Internal Ribosome Entry Site Elements for Native Nef Expression and Function.
abstract: We previously developed replication-competent reporter HIV-1 (referred to herein as LucR.T2A reporter viruses), utilizing a "ribosome skipping" T2A peptide strategy to link Renilla luciferase (LucR) with Nef expression. The demonstrated utility for HIV-1 vaccine and transmission study applications included measurement of neutralizing antibody (NAb) activity in vaccine sera, improved cell-mediated virus inhibition assays, such as T cell-mediated virus inhibition and antibody-dependent cell-mediated cytotoxicity (ADCC) assays, and humanized mouse models. Herein, we extend our prior work and introduce reporter virus technology for applications that require fully functional Nef. We demonstrate that in CD4(+) T cells productively infected with LucR.T2A reporter viruses, T2A peptide-driven Nef expression and function, such as down-regulation of surface CD4 and MHC-I, were impaired. We overcame this limitation of LucR.T2A reporter viruses and achieved physiological Nef expression and function by engineering novel LucR reporter HIV-1 comprising 11 different internal ribosome entry site (IRES) elements chosen for size and relative activity. A range of Nef expression was observed in 293T cells transfected with the different LucR.IRES reporter virus constructs. Iteratively, we identified IRES reporter genomes that expressed Nef closest to physiological levels and produced virus with infectivity, titers, and replication kinetics similar to nonreporter viruses. Our results demonstrated that LucR reporter activity was stable over multiple replication cycles in peripheral blood mononuclear cells (PBMCs). Furthermore, we analyzed Nef functionality, i.e., down-modulation of MHC-I and CD4, following infection of T cell lines and PBMCs. Unlike LucR.T2A reporter virus, one of the redesigned LucR.IRES reporter viruses [containing the modified encephalomyocarditis virus (EMCV) 6ATR IRES element, "6ATRi"] demonstrated Nef expression and function similar to parental "nonreporter" virus. In a previously validated (nef-independent) T cell-based NAb neutralization assay, LucR.6ATRi reporter virus performed indistinguishably from LucR.T2A reporter virus. In summary, reporter viruses comprising the "6ATRi" element promise to augment HIV-1 vaccine and transmission research approaches requiring a sensitive reporter readout combined with wild-type Nef function.
authors.affiliation: 1 Department of Medicine, University of Alabama at Birmingham , Birmingham, Alabama.
authors.forename: Michael O
authors.initials: MO
authors.lastname: Alberti
authors.affiliation: 1 Department of Medicine, University of Alabama at Birmingham , Birmingham, Alabama.
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Jones
authors.affiliation: 1 Department of Medicine, University of Alabama at Birmingham , Birmingham, Alabama.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Miglietta
authors.affiliation: 1 Department of Medicine, University of Alabama at Birmingham , Birmingham, Alabama.
authors.forename: Haitao
authors.initials: H
authors.lastname: Ding
authors.affiliation: 1 Department of Medicine, University of Alabama at Birmingham , Birmingham, Alabama.
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Bakshi
authors.affiliation: 1 Department of Medicine, University of Alabama at Birmingham , Birmingham, Alabama.
authors.forename: Tara G
authors.initials: TG
authors.lastname: Edmonds
authors.affiliation: 1 Department of Medicine, University of Alabama at Birmingham , Birmingham, Alabama.|2 Department of Microbiology, University of Alabama at Birmingham , Birmingham, Alabama.|3 Center for AIDS Research, University of Alabama at Birmingham , Birmingham, Alabama.|4 Birmingham Veterans Affairs Medical Center , Research Service, Birmingham, Alabama.
authors.forename: John C
authors.initials: JC
authors.lastname: Kappes
authors.affiliation: 1 Department of Medicine, University of Alabama at Birmingham , Birmingham, Alabama.|3 Center for AIDS Research, University of Alabama at Birmingham , Birmingham, Alabama.|4 Birmingham Veterans Affairs Medical Center , Research Service, Birmingham, Alabama.
authors.forename: Christina
authors.initials: C
authors.lastname: Ochsenbauer
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000821:virology; D015536:Down-Regulation; D020869:Gene Expression Profiling; D017930:Genes, Reporter; D015497:HIV-1 / Q000235:genetics / Q000502:physiology*; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis; D006801:Humans; D000067556:Internal Ribosome Entry Sites; D049410:Luciferases, Renilla / Q000032:analysis* / Q000235:genetics; D014176:Protein Biosynthesis; D014779:Virus Replication; D054311:nef Gene Products, Human Immunodeficiency Virus / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D015395:Histocompatibility Antigens Class I; D000067556:Internal Ribosome Entry Sites; D054311:nef Gene Products, Human Immunodeficiency Virus; C514837:nef protein, Human immunodeficiency virus 1; D049410:Luciferases, Renilla