Genomic surveillance revealed prevalence of unique SARS-CoV- 2 variants bearing mutation in the RdRp gene among Nevada patients

ABSTRACT Patients with signs of COVID-19 were tested with CDC approved diagnostic RT-PCR for SARS-CoV-2 using RNA extracted from nasopharyngeal/nasal swabs. In order to determine the variants of SARS-CoV-2 circulating in the state of Nevada, 200 patient specimens from positively identified cases were sequenced through our robust protocol for sequencing SARS-CoV-2 genomes from the nasopharyngeal or nasal swabs. This protocol enabled the identification of specific nucleotide variants including those coding for D614G and clades defining mutations. Additionally, these sequences were used for determining the phylogenetic relationships of SARS-CoV-2 genomes of public health importance occurring in the state of Nevada. Our study reports the occurrence of a novel variant in the nsp12 (RdRp-RNA dependent RNA Polymerase) protein at residue 323 (314aa of orf1b) to Phenylalanine (F) from Proline (P), present in the original isolate of SARS-CoV-2 (Wuhan-Hu-1). This 323F variant is found at a very high frequency (46% of the tested specimen) in Northern Nevada, possibly because the virus accumulated this mutation while circulating in the community and the shelter in place orders restricted the introduction and spread of other variants into this region. Structural modeling of the RdRp with P323F variant did not show any significant difference in protein conformation, but the phenotypic effect is unknown and an area of active investigation. In conclusion, our results highlight the introduction and spread of specific SARS-CoV-2 variants at very high frequency within a distinct geographic location that is important for clinical and public health perspectives in understanding the evolution and transmission of SARS-CoV-2. IMPORTANCE SARS-COV-2 genomes accumulate nucleotide mutations while passing in the human population and these mutations may confer phenotypic differences including altered immune response and anti-viral drug resistance. We developed a robust workflow to sequence SARS-CoV-2 directly from the nasal/nasopharyngeal swabs containing even a very low viral loads (>35 Ct value samples). Our protocol does not rely on amplicon based sequencing strategies nor the need of passing the virus into tissue culture thus reduces the possibility of an introduction of laboratory-adapted mutations. Sequences of SARS-CoV-2 from the patients of the state of Nevada during early months of the pandemic identified a rare mutation in the RdRp protein (P323F). This mutation occurred at a very high frequency in the variants of SARS-CoV-2 circulating Northern Nevada. Identification of such variants is important for clinical and public health perspectives in understanding transmission mediated evolution of SARS-CoV-2 variants and their implications on therapeutics and diagnostics.