Fig. 6: CHIKV nsP3 assembles into tubular structures that define the architecture of alpha-granules.

a Transmission electron microscopy of human fibroblasts infected with CHIKV 21 strain (MOI of 10) for 24 h (upper panel) or stably expressing the CHIKV nsP3 (lower panel). Longitudinal (left) and transversal (right) views of the nsP3 tubes are shown. Images are representative of two independent experiments. Scale bars, 500 nm (mock panels) and 200 nm (infection and nsP3-overexpression panels). b Transmission electron microscopy of human fibroblasts transfected with empty plasmid (mock) or MAYV, OONV or EEEV nsP3 plasmids. Scale bars, 500 nm. c The left panel shows a micrograph corresponding to a section of alpha granules perpendicularly cutting a bundle of HSs. A 0.2 µm2 is depicted. 16 HSs are present and numbered within the 0.2 µm2 square. The scaffold numbered as 13 is superposed to three concentric circles of the dimensions obtained for the HSs (see Fig. 1) including the internal channel (green circle), the MDs (blue circle), the and external density around the tube (red circle). Circles diameter and area were calculated with ImageJ for each one of the 16 HSs in the image (bottom panels). Scale bar, 20 nm. Data are presented as mean ± SD from one experiment. Source data are provided as a Source Data file. d Human fibroblasts were infected with CHIKV 21 strain for 24 h. Cells were immunostained with an anti-Capsid or anti-nsP3 specific Ab. Viral genomic RNA was detected using a CHIKV-genome specific fluorescent RNA probes. Co-localization analysis was performed using JACoP plugin implemented in ImageJ37. Scale bars, 20 µm. Images are representative of 2 independent experiments.