title: Griffithsin tandemers: flexible and potent lectin inhibitors of the human immunodeficiency virus.
abstract: BACKGROUND
  The lectin griffithsin (GRFT) is a potent antiviral agent capable of prevention and treatment of infections caused by a number of enveloped viruses and is currently under development as an anti-HIV microbicide. In addition to its broad antiviral activity, GRFT is stable at high temperature and at a broad pH range, displays little toxicity and immunogenicity, and is amenable to large-scale manufacturing. Native GRFT is a domain-swapped homodimer that binds to viral envelope glycoproteins and has displayed mid-picomolar activity in cell-based anti-HIV assays. Previously, we have engineered and analyzed several monomeric forms of this lectin (mGRFT) with anti-HIV EC50 values ranging up to 323 nM. Based on our previous analysis of mGRFT, we hypothesized that the orientation and spacing of the carbohydrate binding domains GRFT were key to its antiviral activity.
  
  
  RESULTS
  Here we present data on engineered tandem repeats of mGRFT (mGRFT tandemers) with antiviral activity at concentrations as low as one picomolar in whole-cell anti-HIV assays. mGRFT tandemers were analyzed thermodynamically, both individually and in complex with HIV-1 gp120. We also demonstrate by dynamic light scattering and cryo-electron microscopy that mGRFT tandemers do not aggregate HIV virions. This establishes that, although the intra-virion crosslinking of HIV envelope glycoproteins is likely integral to their activity, the antiviral activity of these lectins is not due to virus aggregation caused by inter-virion crosslinking.
  
  
  CONCLUSIONS
  The engineered tandemer constructs of mGRFT may provide novel and powerful agents for prevention of infection by HIV and other enveloped viruses.
authors.affiliation: Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA. tinoush@umd.edu.|Protein Structure Section, Macromolecular Crystallography Laboratory, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA. tinoush@umd.edu.|Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20740, USA. tinoush@umd.edu.
authors.forename: Tinoush
authors.initials: T
authors.lastname: Moulaei
authors.affiliation: Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA. AAlexandre@csir.co.za.
authors.forename: Kabamba B
authors.initials: KB
authors.lastname: Alexandre
authors.affiliation: Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA. kuriansh@mail.nih.gov.|Basic Science Program, Leidos Biomedical Research, Inc., Frederick National Laboratory, Frederick, MD, 21702, USA. kuriansh@mail.nih.gov.
authors.forename: Shilpa R
authors.initials: SR
authors.lastname: Shenoy
authors.affiliation: Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, 20892, USA. meyersonj@mail.nih.gov.
authors.forename: Joel R
authors.initials: JR
authors.lastname: Meyerson
authors.affiliation: Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA. Lauren.HaughKrumpe@nih.gov.|Basic Science Program, Leidos Biomedical Research, Inc., Frederick National Laboratory, Frederick, MD, 21702, USA. Lauren.HaughKrumpe@nih.gov.
authors.forename: Lauren Rh
authors.initials: LR
authors.lastname: Krumpe
authors.affiliation: Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA. brian.constantine@nih.gov.
authors.forename: Brian
authors.initials: B
authors.lastname: Constantine
authors.affiliation: Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA. wilsonje@mail.nih.gov.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wilson
authors.affiliation: Imquest BioSciences, Frederick, MD, 21704, USA. rbuckheit@imquestbio.com.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Buckheit
authors.affiliation: Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA. mcmahon@ncifcrf.gov.
authors.forename: James B
authors.initials: JB
authors.lastname: McMahon
authors.affiliation: Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, 20892, USA. subramas@mail.nih.gov.
authors.forename: Sriram
authors.initials: S
authors.lastname: Subramaniam
authors.affiliation: Protein Structure Section, Macromolecular Crystallography Laboratory, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA. wlodawer@nih.gov.
authors.forename: Alexander
authors.initials: A
authors.lastname: Wlodawer
authors.affiliation: Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA. okeefeba@mail.nih.gov.
authors.forename: Barry R
authors.initials: BR
authors.lastname: O'Keefe
mesh_terms: D000998:Antiviral Agents / Q000737:chemistry* / Q000494:pharmacology*; D002460:Cell Line; D015497:HIV-1 / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D037121:Plant Lectins / Q000737:chemistry* / Q000494:pharmacology*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000998:Antiviral Agents; D037121:Plant Lectins; D011994:Recombinant Proteins; C499654:griffithsin protein, Griffithsia