A Multiplex PCR Assay for Identifying All Major SARS-CoV-2 Variants

Background Variants of Concern (VOC) of SARS-CoV-2, including the Alpha, Beta, Gamma, and Delta, threaten to prolong the pandemic leading to more global morbidity and mortality. Genome sequencing is the mainstay of tracking the development and evolution of the virus, but is costly, slow, and not easily accessible. Methods A multiplex qRT-PCR assay for SARS-CoV-2 was developed, which identifies all VOC as well as other mutations of interest in the viral genome, eight mutations total, using single nucleotide discriminating molecular beacons in a two-tube assay. The sensitivity and specificity of the assay was tested using in vitro-transcribed targets. Twenty-six SARS-CoV-2 positive patient samples were blinded, then tested using this assay and compared with deep sequencing results. Findings The presented variant molecular beacon assay showed high accuracy when testing in vitro-transcribed targets, down to a limit of detection of five copies of the viral RNA, with 100% specificity. When testing patient samples, the assay was in full agreement with results from deep sequencing with a sensitivity and specificity of 100% (26/26). Using this accurate genotyping, the SARS-CoV-2 samples were classified as the appropriate variants, and of the twenty-six samples two were identified as VOC Alpha, eight as VOC Delta, and two as Epsilon. Interpretation We have developed a qRT-PCR assay for the identification of currently circulating VOC of SARS-CoV-2 as well as other important mutations in its Spike protein coding sequence. This assay can be easily implemented on broadly available five-color thermal cyclers and will help track the spread of these variants.