Analytical Sensitivity of the SalivaDirect™ Assay on the Liberty16 for detecting SARS-CoV-2 B.1.1.529 Omicron

The newly emerged Omicron variant of SARS-CoV-2 has numerous mutations that are not found in other variants of concern (VOCs). Despite acquiring extended functions in adapting to the host-cell environment, the viral genetic variation exerts a potential negative impact on a molecular test, which in turn, compromises public health and safety. The Liberty16 has been clinically validated as a flexible and accessible device system for running the affordable SalivaDirect real time PCR detection assay for SARS-CoV-2 especially in low resource settings. Preliminary, based on in-silico sequence analysis, we found that Omicrons mutation at position 28,311 overlaps with the CDC 2019-nCoV_N1 probe binding region. In order to verify the performance of CDC 2019-nCoV-N1 primers-probe set in detecting the Omicron variant of SARS-CoV-2, plasmids containing Wuhan/WH01/2019 (wild-type) and B.1.1.529 (Omicron) sequences were serially diluted and subsequently directed for SalivaDirect RT-qPCR detection on Liberty16 using commercially procured reagents. Our findings provide analytical support for reports that the mutations in the Omicron variant have little or no impact on SalivaDirect assay in terms of amplification efficiency and detection sensitivity using either standard and the recently reported fast Liberty16 SalivaDirect thermal cycling protocols.