Simplified point-of-care full SARS-CoV-2 genome sequencing using nanopore technology

Pembaur, A.; Sallard, E.; Weil, P. P.; Ortelt, J.; Ahmad-Nejad, P.; Postberg, J.

Background: The scale of the ongoing SARS-CoV-2 pandemic warrants the urgent establishment a global decentralized surveillance and warning system to recognize local outbreaks and the emergence of novel variants-of-concern. Among the available deep-sequencing technologies, nanopore-sequencing could be an important cornerstone, since it is mobile, scalable and acquisition investments are comparably low. Therefore, streamlined and efficient nanopore-sequencing protocols need to be developed and optimized for SARS-CoV-2 variants identification, in particular for smaller hospital laboratories with lower throughput. Results: We adapted and simplified existing workflows using the midnight 1,200 bp amplicon split primer sets for PCR, which produce tiled overlapping amplicons covering almost all of the SARS-CoV-2 genome. Subsequently, we applied the Oxford Nanopore Rapid barcoding protocol and the portable MinION Mk1C sequencer in combination with the ARTIC bioinformatics pipeline. We tested the simplified and less time-consuming workflow on confirmed SARS-CoV-2-positive specimens from clinical routine and identified pre-analytical parameters, which may help to decrease the rate of sequencing failures. Duration of the complete pipeline was approx. 7 hrs for one specimen and approx. 11 hrs for 12 multiplexed barcoded specimens. Conclusions: The adapted protocol contains less processing steps. Diagnostic CT values are the principal criteria for specimen selection. Subsequent to diagnostic qRT-PCR, multiplex library preparation, quality controls, nanopore sequencing and the bioinformatic pipeline can be completely conducted within one working-day.