Observing HIV on a live stream

AIDS is caused by human immunodeficiency viruses (HIV) that put immune cells— »T helper cells«—out of action. Instead of controlling other immune system cells in the defence against pathogens, infected T helper cells produce large quantities of new human immunodeficiency viruses. With the help of ultra-high-resolution imaging, an international research team including scientists from the University of Jena, has now managed to observe the spread of human immunodeficiency viruses amongst living T helper cells in real time.

The research team is using super-resolution STED fluorescence microscopy (see box on p. 55) to provide direct proof for the first time that the AIDS pathogen creates a certain lipid environment for replication. »This gives us a few starting points when it comes to investigating how to potentially prevent this reproduction,« says Prof. Dr Christian Eggeling, who conducts research and teaches at the Friedrich Schiller University Jena, the Leibniz Institute of Photonic Technology, and the University of Oxford.

Together with his colleague Dr Jakub Chojnacki and a team of researchers directed by Prof. Dr Delphine Muriaux and Prof. Dr. Cyril Favard at the University of Montpellier Christian Eggeling hase been examining the plasma membrane of infected T helper cells. The researchers have been focusing on the »gate« through which the human immunodeficiency virus buds from the cell after multiplying inside. The »Gag« protein, which coordinates the processes involved in the assembly of newly produced virus particles, was used as a marker by tagging it with a green-fluorescent molecule. »Where this protein accumulates, the decisive processes take place that lead to the viruses releasing themselves and infecting other cells,« explains Christian Eggeling. In order to decifer these processes, the researchers examined the diffusion of the lipid molecules to and at the place where the »Gag« proteins gather, i.e. where the virus particle buds. During the budding process, the virus particles exit the cell through the plasma membrane and receive their lipid coating. By employing different types of red-fluorescent labeled lipids, Eggeling and his colleagues have now discovered that only certain lipids from the cell membrane interact with the human immunodeficiency virus. Although these lipids were already known, the research team has managed to directly observe this interaction in living cells for the first time.