Classification of Omicron BA.1, BA.1.1 and BA.2 sublineages by TaqMan assay consistent with whole genome analysis data

Abstract

AbstractObjectiveRecently, the Omicron strain of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread and replaced the previously dominant Delta strain. Several Omicron sublineages (BA.1, BA.1.1 and BA.2) have been identified, with in vitro and preclinical reports showing that the pathogenicity and therapeutic efficacy differs between BA.1 and BA.2. We sought to develop a TaqMan assay to identify these subvariants.MethodsA TaqMan assay was constructed for rapid identification and genotyping of Omicron sublineages. We analyzed three characteristic mutations of the spike gene, Δ69–70, G339D and Q493R, by TaqMan assay. The accuracy of the TaqMan assay was examined by comparing its results with the results of whole genome sequencing (WGS) analysis.ResultsA total of 169 SARS-CoV-2 positive samples were analyzed by WGS and TaqMan assay. The 127 samples determined as BA.1/BA.1.1 by WGS were all positive for Δ69–70, G339D and Q493R by TaqMan assay. Forty-two samples determined as BA.2 by WGS were negative for Δ69–70 but positive for G339D and Q493R by TaqMan. The concordance rate between WGS and the TaqMan assay was 100% (169/169).ConclusionTaqMan assays targeting characteristic mutations are useful for identification and discrimination of Omicron sublineages.