Gold nanoparticles help to develop a new method for tracking viruses

Enteroviruses are pathogenic viruses infecting humans. This group consists of polioviruses, coxsackieviruses, echoviruses and rhinoviruses. Enteroviruses are the most common causes of flu, but they also cause serious symptoms such as heart muscle infections and paralysis. Recently, enteroviruses have been linked with chronic diseases such as diabetes.

The infection mechanisms and infectious pathways of enteroviruses are still rather poorly known. Previous studies in the group of Dr. Varpu Marjomäki at the NSC have focused on the cellular factors that are important for the infection caused by selected enteroviruses. The mechanistic understanding of virus opening and the release of the viral genome in cellular structures for starting new virus production is still largely lacking. Furthermore, the knowledge of infectious processes in tissues is hampered by the lack of reliable tools for detecting virus infection.

The newly developed method involves a chemical modification of a known thiol-stabilized gold nanoparticle, the so-called Au102 cluster that was first synthesized and structurally solved by the group of Roger D Kornberg in 2007 and later characterized at NSC by the groups of prof. Hannu Häkkinen and prof. Mika Pettersson in collaboration with Kornberg. The organic thiol surface of the Au102 particles is modified by attaching linker molecules that make a chemical bond to sulfur-containing cysteine residues that are part of the surface structure of the virus. Several tens of gold particles can bind to a single virus, and the binding pattern shows up as dark tags reflecting the overall shape and structure of the virus. The gold particles allow for studies on the structural changes of the viruses during their lifespan.

The study showed also that the infectivity of the viruses is not compromised by the attached gold particles which indicates that the labeling method does not interfere with the normal biological functions of viruses inside cells. This facilitates new investigations on the virus structures from samples taken from inside cells during the various phases of the virus infection, and gives possibilities to obtain new information on the mechanisms of virus uncoating (opening and release of the genome). The new method allows also for tracking studies of virus pathways in tissues. This is important for further understanding of acute and chronic symptoms caused by viruses. Finally, the method is expected to be useful for developing of new antiviral vaccines that are based on virus-like particles.

The method was developed at the NSC as a wide cross-disciplinary collaboration between chemists, physicists and biologists. Researchers involved in the work are Tanja Lahtinen, Kirsi Salorinne, Jaakko Koivisto and Mika Pettersson from the Department of Chemistry, Sami Malola from the Department of Physics and Mari Martikainen and Varpu Marjomäki from the Department of Biology and Environmental Science. The research was coordinated by Docent Varpu Marjomäki and the Scientific Director of NSC, professor Hannu Häkkinen.

The research was funded by the Academy of Finland and the TEKES FiDiPro -project NOVAC (Novel methods for vaccination and virus detection).