Punching holes into Herpes Viruses
The mechanical properties of various forms of herpes virus shells are finally elucidated.
A joint international research effort by Dr. Wouter Roos and Dr. Gijs Wuite from the VU University Amsterdam and Dr. Kerstin Radtke and Dr. Beate Sodeik from the Medizinische Hochschule Hannover has led to the first description of the mechanics of so-called nuclear herpes virus capsids. These viral particles are complex icosahedral protein shells covering and shielding the genetic material of herpes viruses, and are purified from the nuclei of infected cells. The results of this research were published online on June 1st, 2009 in the prestigious journal Proceedings of the National Academy of Sciences USA.
Nuclear Herpes Simplex Virus particles measure only 125 nanometers (approximately one ten-thousandth of a millimeter), therefore, the structure and surface of individual particles can only be studied with methods that have a resolution that is higher than that of a light microscope. With the help of an Atomic Force Microscope, one can now "feel" the particles and image them by scanning systematically over the surface, like the needle on a record player. From these measurements, researchers can assemble a detailed topographic relief of individual viral structures. This can be done in liquid under conditions mimicking living cells. Most importantly, this system allows the mechanical manipulation of particles, as one really touches them.
The researchers used this approach to gain new insights into the mechanics of these viral particles: they punched holes into them, one by one. The force needed to do this gave information about the elastic and mechanical properties of the herpes virus particles. They showed that they are strengthened during the assembly by packaging of the viral DNA into the shell. This reinforcement of the virus probably occurs at the twelve corner points of its icosahedral shell. The unravelling of this viral stabilisation mechanism could open new possibilities to fight herpes infections but could also provide new ways to employ viral particles as nano-containers for delivering drugs or genetic material.