title: Cryo-electron microscopy and single molecule fluorescent microscopy detect CD4 receptor induced HIV size expansion prior to cell entry.
abstract: Viruses are often thought to have static structure, and they only remodel after the viruses have entered target cells. Here, we detected a size expansion of virus particles prior to viral entry using cryo-electron microscopy (cryo-EM) and single molecule fluorescence imaging. HIV expanded both under cell-free conditions with soluble receptor CD4 (sCD4) targeting the CD4 binding site on the HIV-1 envelope protein (Env) and when HIV binds to receptor on cellular membrane. We have shown that the HIV Env is needed to facilitate receptor induced virus size expansions, showing that the 'lynchpin' for size expansion is highly specific. We demonstrate that the size expansion required maturation of HIV and an internal capsid core with wild type stability, suggesting that different HIV compartments are linked and are involved in remodelling. Our work reveals a previously unknown event in HIV entry, and we propose that this pre-entry priming process enables HIV particles to facilitate the subsequent steps in infection.
authors.affiliation: Deakin University, Victoria 3216, Australia; CSIRO Australian Animal Health Laboratory, Victoria 3220, Australia.
authors.forename: Son
authors.initials: S
authors.lastname: Pham
authors.affiliation: ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, New South Wales 3220, Australia.
authors.forename: Thibault
authors.initials: T
authors.lastname: Tabarin
authors.affiliation: Deakin University, Victoria 3216, Australia; CSIRO Australian Animal Health Laboratory, Victoria 3220, Australia.
authors.forename: Megan
authors.initials: M
authors.lastname: Garvey
authors.affiliation: Deakin University, Victoria 3216, Australia; CSIRO Australian Animal Health Laboratory, Victoria 3220, Australia.
authors.forename: Corinna
authors.initials: C
authors.lastname: Pade
authors.affiliation: ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, New South Wales 3220, Australia.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Rossy
authors.affiliation: CSIRO Australian Animal Health Laboratory, Victoria 3220, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Monaghan
authors.affiliation: CSIRO Australian Animal Health Laboratory, Victoria 3220, Australia.
authors.forename: Alex
authors.initials: A
authors.lastname: Hyatt
authors.affiliation: ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, New South Wales 3220, Australia.
authors.forename: Till
authors.initials: T
authors.lastname: Böcking
authors.affiliation: CSIRO Australian Animal Health Laboratory, Victoria 3220, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Leis
authors.affiliation: ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, New South Wales 3220, Australia. Electronic address: k.gaus@unsw.edu.au.
authors.forename: Katharina
authors.initials: K
authors.lastname: Gaus
authors.affiliation: Deakin University, Victoria 3216, Australia; CSIRO Australian Animal Health Laboratory, Victoria 3220, Australia. Electronic address: j.mak@deakin.edu.au.
authors.forename: Johnson
authors.initials: J
authors.lastname: Mak
mesh_terms: D015704:CD4 Antigens / Q000378:metabolism*; D020285:Cryoelectron Microscopy; D015658:HIV Infections / Q000378:metabolism / Q000821:virology*; D015497:HIV-1 / Q000502:physiology* / Q000648:ultrastructure; D006801:Humans; D008856:Microscopy, Fluorescence; D053586:Virus Internalization
chemical_list: D015704:CD4 Antigens
keywords: Cryo-EM; Entry; HIV-1; Pre-entry priming; Retrovirus; Single molecule fluorescent imaging; Structural rearrangement; Super-resolution microscopy; Tomography; dSTORM