New Assay Fast-Tracks Virucidal Testing

An innovative technique that can quickly determine if a virus is contagious has the potential to transform future pandemic responses. Viral capsid pores can be as small as 0.6 nm in diameter. In this technique, scientists coupled a dye capable of penetrating the viral capsid with a molecule that cannot, allowing for rapid assessment of viral infectivity.

The assay, known as FAIRY (Fluorescence Assay for vIRal IntegritY), can rapidly screen viruses against virucidal antivirals in a matter of minutes. This makes it possible to assess the efficacy of antiviral treatments, such as disinfectants that interrupt the infection chain.

On average, every four years a new virus is discovered that has pandemic potential, and there are many more already known viruses that could cross the species barrier. Yet to best of our knowledge there is currently no assay capable of identifying whether a sample contains intact or non-intact viruses, and therefore shows whether it is infectious or non-infectious, without cell cultivation that could take weeks.”

Dr. Samuel Jones, Study Lead Researcher, School of Chemistry, University of Birmingham

Viral infectivity is currently determined using cultured cells, which is the gold standard method. However, this method requires specialized staff to perform the testing, takes many days to show results, and requires a cultivatable cell line, which is unavailable for all viruses.

The requirement to employ cultured cells restricts the antivirals that can be used in current methods, which adds another layer of difficulty to the search for novel disinfectant solutions.

The novel technique makes use of a dye that, in most cases, can enter viruses through holes in the capsid, the protein shell that encases the genetic material (DNA or RNA). Since this dye is conjugated to a bigger molecule, the capsid pores are unable to allow it to pass through. A fluorescent signal is produced when the dye attaches itself to viral DNA or RNA.

The outcome of the assay indicates whether or not the virus is infectious and intact.

The researchers have used Herpes simplex virus (HSV-2), respiratory syncytial virus (RSV), cytomegalovirus (CMV), human rhinovirus-8 (HRV-8), human coronavirus OC43 (OC43), chikungunya virus (CHIKV), dengue virus 1 and dengue virus 2, zika virus, and enterovirus 71 (EV71) to assess the assay's efficacy.

These viruses demonstrate the full potential of the FAIRY assay, encompassing both enveloped and non-enveloped viruses as well as DNA and RNA viruses. Numerous substances with broad-spectrum virucidal activity, such as hydrogen peroxide, ethanol, isopropanol, and other antivirals, were used to treat the viruses.

These tests' results demonstrated the FAIRY assay's potential for the quick investigation of virucides that demolish viral capsids.

This simple, low-cost, assay uses ready-made consumables, and can rapidly screen multiple disinfectants and viruses, in a single microplate assay, for their ability to neutralize viral infectivity. It could have screened every disinfectant for antiviral activity during the SARS-CoV-2 pandemic and so deliver a more rapid response during the next pandemic.”

Dr. Samuel Jones, Study Lead Researcher, School of Chemistry, University of Birmingham