In our research, we study the morphology and cellular interactions of viruses by using super-resolution fluorescence microscopy and advanced image analysis tools. We are interested in understanding why many viruses form particles that vary in size and shape, ranging from small spheres to long filamentous structures that can reach many microns in length, because this is not well understood.

On the cover of the December 11 issue of Biophysical Reports, we show a graphical representation of the spherical and filamentous forms of the influenza virus. The image shows three filamentous viruses (foreground and background) as well as a spherical particle (middle) in which the viral membrane has ruptured. The surface glycoproteins of the viruses can be seen extending away from the viral membrane on each virus particle.

In the research article, we used a pressure vessel model and microscopy to investigate the relationship between virus particle dimensions and engineering stress and concluded that viral filaments offer an optimal shape that allows viruses to have a larger volume than they could in any alternative geometry. In this way, viruses can produce larger particles without exceeding the critical stress that would result in rupture of their membrane. A filamentous morphology may offer an advantage to the virus by increasing the ability of the virus to penetrate mucus layers, increasing its resilience to UV radiation, or increasing its ability to evade antibodies because of the increased number of surface proteins per virion.

Virus structure is of interest not only in the context of how viruses assemble, but also because morphological variations in virus shape may correlate with infectivity and pathogenicity. Our work offers insight into the possible purpose of filamentous virus morphology and may also be applicable to a wide range of other biological entities, including bacteria and fungi.

You can find more information on our work at https://warwick.ac.uk/fac/sci/med/research/biomedical/labs/nrobb/robblab/ and https://holdenlab.github.io/projects/mcmahon_andrew/.

— Andrew McMahon, Swetha Vijayakrishnan, Hafez El Sayyed, Danielle Groves, Michaela J. Conley, Edward Hutchinson, and Nicole Robb