Site-selective nucleation and controlled growth of gold nanostructures in tobacco mosaic virus nanotubulars

Site-selective biomineralization of Au nanostructures in the interior channel of Tobacco Mosaic Virus (TMV) is achieved by mutating threonine 103 in TMV to cysteine (T103C-TMV) to introduce the strong coordination interaction between the arrayed sulfhydryl ligands and gold species. By finely tuning the reaction conditions, Au nanoparticle chains and Au nanorods are successfully and exclusively synthesized inside the T103C-TMV nanotubes.

Understanding internalization of rotavirus VP6 nanotubes by cells: towards a recombinant vaccine

Rotavirus VP6 nanotubes are an attractive option for a recombinant vaccine against rotavirus disease. Protection against rotavirus infection and an adjuvant effect have been observed upon immunization with VP6 nanotubes. However, little information exists on how VP6 nanotubes interact with cells and trigger an immune response. In this work, the interaction between VP6 nanotubes and different cell lines was characterized. VP6 nanotubes were not cytotoxic to any of the animal or human cell lines tested. Uptake of nanotubes into cells was cell-line-dependent, as only THP1 and J774 macrophage cells internalized them. Moreover, the size and spatial arrangement of VP6 assembled into nanotubes allowed their uptake by macrophages, as double-layered rotavirus-like particles also displaying VP6 in their surface were not taken up. The internalization of VP6 nanotubes was inhibited by methyl-β-cyclodextrin, but not by genistein, indicating that nanotube entry is specific, depends on the presence of cholesterol in the plasma membrane, and does not require the activity of tyrosine kinases. The information generated here expands our understanding of the interaction of protein nanotubes with cells, which is useful for the application of VP6 nanotubes as a vaccine.

Mechanism of membranous tunnelling nanotube formation in viral genome delivery

In internal membrane-containing viruses, a lipid vesicle enclosed by the icosahedral capsid protects the genome. It has been postulated that this internal membrane is the genome delivery device of the virus. Viruses built with this architectural principle infect hosts in all three domains of cellular life. Here, using a combination of electron microscopy techniques, we investigate bacteriophage PRD1, the best understood model for such viruses, to unveil the mechanism behind the genome translocation across the cell envelope. To deliver its double-stranded DNA, the icosahedral protein-rich virus membrane transforms into a tubular structure protruding from one of the 12 vertices of the capsid. We suggest that this viral nanotube exits from the same vertex used for DNA packaging, which is biochemically distinct from the other 11. The tube crosses the capsid through an aperture corresponding to the loss of the peripentonal P3 major capsid protein trimers, penton protein P31 and membrane protein P16. The remodeling of the internal viral membrane is nucleated by changes in osmolarity and loss of capsid-membrane interactions as consequence of the de-capping of the vertices. This engages the polymerization of the tail tube, which is structured by membrane-associated proteins. We have observed that the proteo-lipidic tube in vivo can pierce the gram-negative bacterial cell envelope allowing the viral genome to be shuttled to the host cell. The internal diameter of the tube allows one double-stranded DNA chain to be translocated. We conclude that the assembly principles of the viral tunneling nanotube take advantage of proteo-lipid interactions that confer to the tail tube elastic, mechanical and functional properties employed also in other protein-membrane systems.