Figure 3

Electron Micrographs Showing Virus Internalization by Clathrin- or Caveolar/Raft-Mediated Endocytosis

(A and B) Semliki Forest virus, a 70 nm diameter enveloped alphavirus, is internalized by clathrin-coated pits (A) and vesicles (B) for endocytosis and infection. Here, the virus is interacting with a BHK-21 cell.

(C and D) Simian virus 40, a small 50 nm diameter nonenveloped DNA virus, binds to gangliosides in the plasma membrane of CV-1 cells and enters via caveolae (C) and tight-fitting small vesicles. The viruses are transported through caveosomes to the ER, where many accumulate in smooth membrane domains (D). Scale bar in (A) and (C) = 100 nm, (B) = 200 nm, and (D) = 250 nm. (A), (C), and (D) are courtesy of J. Kartenbeck and A.H. (B) is reproduced from Helenius et al. (1980), The Journal of Cell Biology, 1980, volume 84, pp. 404–420 by copyright permission of The Rockefeller University Press.