The emergence of several SARS-CoV-2 variants has been all over the news in recent weeks. We asked our colleagues Allison R. McMullen, Molecular Scientific Affairs Manager and Jamie E. Phillips, Sr. Scientific Affairs Manager POC to help us understand exactly what a variant is and if it could impact COVID-19 testing.
Allison R. McMullen, Ph.D, D(ABMM), Scientific Affairs Manager
Jamie E. Phillips, MS, PhD, Sr. Scientific Affairs Manager
Coronaviruses, like SARS-CoV-2, constantly evolve and, as a result, genetic changes are expected to arise over time leading to different virus variants. As of January 2021, multiple variants of SARS-CoV-2 have been identified including those from the United Kingdom (UK), South Africa and Brazil. The extent to which these new variants have spread, whether differences in COVID-19 disease exist among variants, and the broad efficacy of vaccines and targeted immunotherapies, remain largely unknown at this time.
Each molecular assay that Roche produces for SARS-CoV-2 is designed to target conserved regions of the genome and utilizes a dual target design. This dual target design was chosen to dramatically increase the likelihood of viral sequence detection from at least one target- in other words, if a change occurs in one target, the other will still be positive. Because the assays target conserved regions, these areas are much less likely to change. But what does this actually mean? Let's use an analogy . . . this one is for all you car lovers out there. Let’s think about a car and if you change a piece of the engine, the car may no longer run. The same is true for viruses, if they mutate (change) in an area that is essential for replication then they are no longer able to replicate and make more viruses. However, if the car is repainted, then the car still runs just fine, but may look a little bit different. Thus, for this example, Roche targets the engine of the virus, the conserved regions, because typically the virus changes very little in the areas needed for replication.
Ongoing surveillance is essential to determine the potential impact of variants on the performance of our assays. As such, Roche regularly monitors the NCBI and GISAID databases and assess, using in silico (computer modeling) analyses, the inclusivity of sequences used for our current portfolio of SARS-CoV-2 EUA assays.
Based on comprehensive sequence analyses of all SARS-CoV-2 variants in publicly-available databases (more than 300,000 sequences to date), no performance impacts are anticipated for any Roche EUA SARS-CoV-2 assay (molecular1 or serological2) due to the observed nucleotide mutations.