ABSTRACT
In the ongoing COVID-19 pandemic, detecting the appearance and spread of variants of concern (VOC) is a critical capability in the fight to quell the virus and return to normalcy. Genomic surveillance of the emergence, propagation, and geographical spread of VOCs is thus an important tool for public health officials and government leaders to make policy decisions and advise the public. As part of our role as a major SARS-CoV-2 diagnostic testing facility in New York City, the Pandemic Response Lab (PRL) has been performing genomic surveillance on the large number of positive samples processed by the facility on a daily basis from throughout the New York metropolitan area. Here we describe the development and optimization of a high-throughput SARS-CoV-2 genome sequencing facility at PRL serving New York City.
ABSTRACT
The SARS Coronavirus 2 (SARS-CoV-2) pandemic presents new scientific and scale-up challenges for diagnostic capabilities worldwide. The gold standard diagnostic for SARS-CoV-2 infection is a reverse transcription/quantitative PCR (RT-qPCR) which targets the viral genome, an assay that has now been performed on millions of patient specimens worldwide regardless of symptomatic status. Recently Zhang et al. suggested the possibility that the SARS-CoV-2 N gene could integrate into host cell DNA through the action of the LINE-1 retrotransposon, a mobile element that is potentially active in human somatic cells, thereby calling into question the veracity of N-gene based RT-qPCR for detection of SARS-CoV-2 infection. Accordingly, we assessed the potential impact of these purported integration events on nasal swab specimens tested at our clinical laboratory. Using an N-gene based RT-qPCR assay, we tested 768 arbitrarily selected specimens and identified 2 samples which resulted in a positive detection of viral sequence in the absence of reverse transcriptase, a necessary but not sufficient signal consistent with possible integration of the SARS-CoV-2 N gene into the host genome. Regardless of possible viral N gene integration into the genome, in this small subset of samples, all patients were still positive for SARS-CoV-2 infection, as indicated by a much lower Ct value for reactions performed in the presence of reverse transcriptase (RT) versus reactions performed without RT. Moreover, one of the two positives observed in the absence of RT also tested positive when using primers targeting ORF1ab, a gene closer to the 5 end of the genome. These data are inconsistent with the N gene integration hypothesis suggested by the studies by Zhang et al., and importantly, our results suggest little to no practical impact of possible SARS-CoV-2 genome integration events on RT-qPCR testing. COMPETING INTEREST STATEMENTThe authors of this study are employees of the Pandemic Response Lab (PRL)/ReOpen Diagnostics, a private company performing SARS-CoV-2 RT-qPCR based testing, an area of interest of this study.
ABSTRACT
Wide-scale SARS-CoV-2 genome sequencing is critical to tracking viral evolution during the ongoing pandemic. Variants first detected in the United Kingdom, South Africa, and Brazil have spread to multiple countries. We developed the software tool, Variant Database (VDB), for quickly examining the changing landscape of spike mutations. Using VDB, we detected an emerging lineage of SARS-CoV-2 in the New York region that shares mutations with previously reported variants. The most common sets of spike mutations in this lineage (now designated as B.1.526) are L5F, T95I, D253G, E484K or S477N, D614G, and A701V. This lineage was first sequenced in late November 2020 when it represented <1% of sequenced coronavirus genomes that were collected in New York City (NYC). By February 2021, genomes from this lineage accounted for ~32% of 3288 sequenced genomes from NYC specimens. Phylodynamic inference confirmed the rapid growth of the B.1.526 lineage in NYC, notably the sub-clade defined by the spike mutation E484K, which has outpaced the growth of other variants in NYC. Pseudovirus neutralization experiments demonstrated that B.1.526 spike mutations adversely affect the neutralization titer of convalescent and vaccinee plasma, indicating the public health importance of this lineage.
