Visualization of HIV T Cell Virological Synapses and Virus-Containing Compartments by Three-Dimensional Correlative Light and Electron Microscopy

J Virol. 2017 Jan 3;91(2):e01605-16. doi: 10.1128/JVI.01605-16. Print 2017 Jan 15.


Virological synapses (VS) are adhesive structures that form between infected and uninfected cells to enhance the spread of HIV-1. During T cell VS formation, viral proteins are actively recruited to the site of cell-cell contact where the viral material is efficiently translocated to target cells into heterogeneous, protease-resistant, antibody-inaccessible compartments. Using correlative light and electron microscopy (CLEM), we define the membrane topography of the virus-containing compartments (VCC) where HIV is found following VS-mediated transfer. Focused ion beam scanning electron microscopy (FIB-SEM) and serial sectioning transmission electron microscopy (SS-TEM) were used to better resolve the fluorescent Gag-containing structures within the VCC. We found that small punctate fluorescent signals correlated with single viral particles in enclosed vesicular compartments or surface-localized virus particles and that large fluorescent signals correlated with membranous Gag-containing structures with unknown pathological function. CLEM imaging revealed distinct pools of newly deposited viral proteins within endocytic and nonendocytic compartments in VS target T cells.

Importance: This study directly correlates individual virus-associated objects observed in light microscopy with ultrastructural features seen by electron microscopy in the HIV-1 virological synapse. This approach elucidates which infection-associated ultrastructural features represent bona fide HIV protein complexes. We define the morphology of some HIV cell-to-cell transfer intermediates as true endocytic compartments and resolve unique synapse-associated viral structures created by transfer across virological synapses.

Keywords: Gag; HIV-1; T cells; correlative light and electron microscopy; endosome; focused ion beam electron microscopy; transmission electron microscopy; virological synapses; virus dissemination.

MeSH terms

  • CD4-Positive T-Lymphocytes / ultrastructure*
  • CD4-Positive T-Lymphocytes / virology*
  • HIV Infections / virology*
  • HIV-1 / physiology*
  • HIV-1 / ultrastructure*
  • Host-Pathogen Interactions*
  • Humans
  • Virion / physiology
  • Virus Internalization
  • Virus Replication
  • Virus Uncoating