Left: Infected cell imaged with CARS microscopy showing lipid droplets and membranes. Right: Two-photon fluorescence image of the same cell. The fluorescent protein visualised by this technique confirms viral infection.
National Physical Laboratory (NPL), working with the University of Edinburgh, has developed a technique that makes it possible to watch the infection of individual cells by viruses in real time.
It is hoped that by observing how different properties of the cells are affected at different stages of an infection, it will be possible to monitor the effects of new treatments.
This imaging works on a molecular level, revealing the spread of the virus through the cell by imaging the viral proteins (using a technique called 'two-photon fluorescence'). The changes in the cell's membrane are also observed (using a technique called 'Coherent Anti-Stokes Raman Scattering'), giving a high resolution image of the cell's shape, and showing how this is altered by the virus. These two techniques are used together and allow these changes to be observed simultaneously in a cell, in real time.
The virus in this study (a cytomegalovirus) was altered to express a fluorescent protein, which is visible when using this technique. This protein could be seen in a higher concentration in the nucleus of the infected cell, compared to the surrounding cytosol. The nucleus of the cell expanded, and the cell itself became more rounded.
Researchers are particularly interested in the effect the virus has on the host cell's metabolic functions. These results have shown how the lipid storage mechanisms of the host cell are recruited as part of the viral infection and replication cycle.
The research is now progressing to investigate this technique using live cells, rather than fixed samples.
