Fig. 3: Ultrastructural identification of HTNV virions at different stages of the viral life cycle in primary human CD8⁺ T cells.

CD8⁺ T cells were infected with HTNV for 72 h and then fixed with 2% glutaraldehyde and analyzed by TEM. a Representative images of uninfected CD8⁺ T cells (I); representative images at high magnification revealed the presence of virus-like particles contained within multivesicular bodies (MBVs) (II and III, yellow arrows); the presence of vesicles secreted from the T cells (IV, black arrows). b Distribution of vesicle structures containing virion particles in the cytoplasm of HTNV-infected CD8⁺ T cells. Viral entry occurred first by virion attachment to the cell surface (I). Nucleocapsids are assembled in the vesicles, and some microvesicles formed in the vesicles (II). The nucleocapsids budded into the smooth vesicles and acquired viral envelopes (III). These nucleocapsids were not yet enclosed by an envelope, as shown by the light-colored structure in the core. As the nucleocapsids replicated, after which the ribosomes attached to the surface of the vesicles decreased initially and gradually disappeared completely (IV). At 96 h after infection, CD8⁺ T cell necrosis was detected, along with an increase in mature viral particles in the cytoplasm (V). The red arrows represent the virus. c Schematic illustration of the life cycle of hantaviruses in primary CD8⁺ T cells. Steps 1–5 correspond to the same stages in b.