Sensitive Recovery of Complete SARS-CoV-2 Genomes from Clinical Samples by Use of Swift Biosciences' SARS-CoV-2 Multiplex Amplicon Sequencing Panel

Efficacy of parainfluenza virus 5 (PIV5)-vectored intranasal COVID-19 vaccine as a single dose primer and booster against SARS-CoV-2 variants

Immunization with COVID-19 vaccines has greatly reduced COVID-19-related deaths and hospitalizations from SARS-CoV-2 infection, but waning immunity and the emergence of variants capable of immune escape indicate the need for annual vaccine updates or development of different SARS-CoV-2 vaccine platforms. Parainfluenza virus 5 (PIV5)-vectored intranasal COVID-19 vaccine with the ancestral spike (S) protein (CVXGA1) has been shown to be a promising next-generation COVID-19 vaccine preclinically and is currently being evaluated in humans. This work investigates the immunogenicity and efficacy of CVXGA1 and other PIV5-vectored vaccine candidates expressing additional SARS-CoV-2 nucleoprotein (N) antigen or SARS-CoV-2 variant S proteins of beta, delta, gamma, and omicron variants against homologous and heterologous challenges in hamsters. A single intranasal dose of CVXGA1 induces neutralizing antibodies (nAbs) against SARS-CoV-2 WA1 (ancestral), delta variant, and omicron variant and protects against both homologous and heterologous virus challenges. Compared to mRNA COVID-19 vaccine, neutralizing antibody titers induced by CVXGA1 were well maintained over time. When administered as a booster following two doses of an mRNA COVID-19 vaccine, PIV5-vectored vaccines expressing the S protein from WA1 (CVXGA1), delta, or omicron variants generate higher levels of cross-reactive nAbs than three doses of mRNA vaccine. Our data indicate that an intranasal PIV5-vectored COVID-19 vaccine can serve as a booster vaccine against emerging variants.

IMPORTANCE

With emerging new variants of concern (VOC), SARS-CoV-2 continues to be a major threat to human health. Approved COVID-19 vaccines have been less effective against these emerging VOCs. This work demonstrates the protective efficacy and strong boosting effect of an intranasal viral-vectored vaccine against SARS-CoV-2 variants in hamsters. Our intranasal vaccine can act as an effective booster for individuals already 58 vaccinated against SARS-CoV-2.

SARS-CoV-2 genomic surveillance using self-collected saliva specimens during occupational testing programs

Continually emerging SARS-CoV-2 variants pose challenges to clinical and public health interventions, necessitating sustainable approaches to real-time variant monitoring. This case study describes an innovative SARS-CoV-2 screening and surveillance program that demonstrates the utility of sequencing-based variant monitoring using self-collected saliva specimens. We conducted saliva-based SARS-CoV-2 screening in occupational settings in Omaha, Nebraska from December 2021 through November 2022. 8,372 saliva specimens collected from 1,480 participants were tested for SARS-CoV-2 RNA by extraction-free PCR, with 334 positive samples referred for whole-genome sequencing analysis. Program utilization, quality metrics, and sequencing outputs were compared across sites. Specimen quality was high across program settings, demonstrating the suitability of self-collected saliva specimens for PCR and genomic surveillance testing. Virus RNA sequencing successfully determined the variant strain in 83 and 67% of SARS-CoV-2-positive saliva samples collected in two program settings, demonstrating the successful integration of SARS-CoV-2 sequencing for variant determination into screening programs in occupational settings using self-collected saliva with an extraction-free qRT-PCR testing method. We further demonstrate that the sensitivity and efficiency of variant analysis is dependent on the PCR cycle threshold (Ct) cutoff of the diagnostic assay virus gene target. Use of an optimized Ct value cutoff for sequencing referral is recommended. Community-based saliva testing programs can be utilized to enhance variant monitoring, and could be considered in the risk identification of other respiratory infections. This approach offers the advantages of a non-invasive specimen collection, no need for supervised collection by a healthcare worker, supply chain resiliency, distributable access, and scalability.

Protocol for the creation and characterization of SARS-CoV-2 variant testing panels using remnant clinical samples for diagnostic assay testing

The emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Alpha variant in 2020 demonstrated the need for reanalysis of diagnostic tests to ensure detection of emerging variants. Here, we present a protocol for creating and characterizing SARS-CoV-2 variant testing panels using remnant clinical samples for diagnostic assay testing. We describe steps for characterizing SARS-CoV-2 remnant clinical samples and preparing them into pools and their use in preparing varying quantities of virus. We then detail procedures for verifying variant detection using the resulting sample panel. For complete details on the use and execution of this protocol, please refer to Rao et al.1,2.

Comparison of RT-PCR and antigen test sensitivity across nasopharyngeal, nares, and oropharyngeal swab, and saliva sample types during the SARS-CoV-2 omicron variant

Limited data highlight the need to understand differences in SARS-CoV-2 omicron (B.1.1.529) variant viral load between the gold standard nasopharyngeal (NP) swab, mid-turbinate (MT)/anterior nasal swabs, oropharyngeal (OP) swabs, and saliva. MT, OP, and saliva samples from symptomatic individuals in Atlanta, GA, in January 2022 and longitudinal samples from a small familial cohort were tested by both RT-PCR and ultrasensitive antigen assays. Higher concentrations in the nares were observed in the familial cohort, but a dominant sample type was not found among 39 cases in the cross-sectional cohort. The composite of positive MT or OP assay for both RT-PCR and antigen assay trended toward higher diagnostic yield but did not achieve significant difference. Our data did not identify a singular preferred sample type for SARS-CoV-2 testing, but higher levels of saliva nucleocapsid, a trend toward higher yield of composite OP/MT result, and association of apparent MT or OP predominance with symptoms warrant further study.

Viral Resistance Analyses From the Remdesivir Phase 3 Adaptive COVID-19 Treatment Trial-1 (ACTT-1)

BACKGROUND

Remdesivir is approved for treatment of coronavirus disease 2019 (COVID-19) in nonhospitalized and hospitalized adult and pediatric patients. Here we present severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resistance analyses from the phase 3 ACTT-1 randomized placebo-controlled trial conducted in adult participants hospitalized with COVID-19.

METHODS

Swab samples were collected at baseline and longitudinally through day 29. SARS-CoV-2 genomes were sequenced using next-generation sequencing. Phenotypic analysis was conducted directly on participant virus isolates and/or using SARS-CoV-2 subgenomic replicons expressing mutations identified in the Nsp12 target gene.

RESULTS

Among participants with both baseline and postbaseline sequencing data, emergent Nsp12 substitutions were observed in 12 of 31 (38.7%) and 12 of 30 (40.0%) participants in the remdesivir and placebo arms, respectively. No emergent Nsp12 substitutions in the remdesivir arm were observed in more than 1 participant. Phenotyping showed low to no change in susceptibility to remdesivir relative to wild-type Nsp12 reference for the substitutions tested: A16V (0.8-fold change in EC50), P323L + V792I (2.2-fold), C799F (2.5-fold), K59N (1.0-fold), and K59N + V792I (3.4-fold).

CONCLUSIONS

The similar rate of emerging Nsp12 substitutions in the remdesivir and placebo arms and the minimal change in remdesivir susceptibility among tested substitutions support a high barrier to remdesivir resistance development in COVID-19 patients. Clinical Trials Registration. NCT04280705.

Implementation of California COVIDNet - a multi-sector collaboration for statewide SARS-CoV-2 genomic surveillance

Introduction

The SARS-CoV-2 pandemic represented a formidable scientific and technological challenge to public health due to its rapid spread and evolution. To meet these challenges and to characterize the virus over time, the State of California established the California SARS-CoV-2 Whole Genome Sequencing (WGS) Initiative, or "California COVIDNet". This initiative constituted an unprecedented multi-sector collaborative effort to achieve large-scale genomic surveillance of SARS-CoV-2 across California to monitor the spread of variants within the state, to detect new and emerging variants, and to characterize outbreaks in congregate, workplace, and other settings.

Methods

California COVIDNet consists of 50 laboratory partners that include public health laboratories, private clinical diagnostic laboratories, and academic sequencing facilities as well as expert advisors, scientists, consultants, and contractors. Data management, sample sourcing and processing, and computational infrastructure were major challenges that had to be resolved in the midst of the pandemic chaos in order to conduct SARS-CoV-2 genomic surveillance. Data management, storage, and analytics needs were addressed with both conventional database applications and newer cloud-based data solutions, which also fulfilled computational requirements.

Results

Representative and randomly selected samples were sourced from state-sponsored community testing sites. Since March of 2021, California COVIDNet partners have contributed more than 450,000 SARS-CoV-2 genomes sequenced from remnant samples from both molecular and antigen tests. Combined with genomes from CDC-contracted WGS labs, there are currently nearly 800,000 genomes from all 61 local health jurisdictions (LHJs) in California in the COVIDNet sequence database. More than 5% of all reported positive tests in the state have been sequenced, with similar rates of sequencing across 5 major geographic regions in the state.

Discussion

Implementation of California COVIDNet revealed challenges and limitations in the public health system. These were overcome by engaging in novel partnerships that established a successful genomic surveillance program which provided valuable data to inform the COVID-19 public health response in California. Significantly, California COVIDNet has provided a foundational data framework and computational infrastructure needed to respond to future public health crises.

Convergence of immune escape strategies highlights plasticity of SARS-CoV-2 spike

The global spread of the SARS-CoV-2 virus has resulted in emergence of lineages which impact the effectiveness of immunotherapies and vaccines that are based on the early Wuhan isolate. All currently approved vaccines employ the spike protein S, as it is the target for neutralizing antibodies. Here we describe two SARS-CoV-2 isolates with unusually large deletions in the N-terminal domain (NTD) of the spike. Cryo-EM structural analysis shows that the deletions result in complete reshaping of the NTD supersite, an antigenically important region of the NTD. For both spike variants the remodeling of the NTD negatively affects binding of all tested NTD-specific antibodies in and outside of the NTD supersite. For one of the variants, we observed a P9L mediated shift of the signal peptide cleavage site resulting in the loss of a disulfide-bridge; a unique escape mechanism with high antigenic impact. Although the observed deletions and disulfide mutations are rare, similar modifications have become independently established in several other lineages, indicating a possibility to become more dominant in the future. The observed plasticity of the NTD foreshadows its broad potential for immune escape with the continued spread of SARS-CoV-2.

Efficacy of primary series AZD1222 (ChAdOx1 nCoV-19) vaccination against SARS-CoV-2 variants of concern: Final analysis of a randomized, placebo-controlled, phase 1b/2 study in South African adults (COV005)

COVID-19 vaccine efficacy (VE) has been observed to vary against antigenically distinct SARS-CoV-2 variants of concern (VoC). Here we report the final analysis of VE and safety from COV005: a phase 1b/2, multicenter, double-blind, randomized, placebo-controlled study of primary series AZD1222 (ChAdOx1 nCoV-19) vaccination in South African adults aged 18-65 years. South Africa's first, second, and third waves of SARS-CoV-2 infections were respectively driven by the ancestral SARS-CoV-2 virus (wild type, WT), and SARS-CoV-2 Beta and Delta VoCs. VE against asymptomatic and symptomatic infection was 90.6% for WT, 6.7% for Beta and 77.1% for Delta. No cases of severe COVID-19 were documented ahead of unblinding. Safety was consistent with the interim analysis, with no new safety concerns identified. Notably, South Africa's Delta wave occurred ≥ 9 months after primary series vaccination, suggesting that primary series AZD1222 vaccination offers a good durability of protection, potentially due to an anamnestic response. Clinical trial identifier: CT.gov NCT04444674.

Dynamics of SARS-CoV-2 VOC Neutralization and Novel mAb Reveal Protection against Omicron

New variants of SARS-CoV-2 continue to emerge and evade immunity. We isolated SARS-CoV-2 temporally across the pandemic starting with the first emergence of the virus in the western hemisphere and evaluated the immune escape among variants. A clinic-to-lab viral isolation and characterization pipeline was established to rapidly isolate, sequence, and characterize SARS-CoV-2 variants. A virus neutralization assay was applied to quantitate humoral immunity from infection and/or vaccination. A panel of novel monoclonal antibodies was evaluated for antiviral efficacy. We directly compared all variants, showing that convalescence greater than 5 months post-symptom onset from ancestral virus provides little protection against SARS-CoV-2 variants. Vaccination enhances immunity against viral variants, except for Omicron BA.1, while a three-dose vaccine regimen provides over 50-fold enhanced protection against Omicron BA.1 compared to a two-dose. A novel Mab neutralizes Omicron BA.1 and BA.2 variants better than the clinically approved Mabs, although neither can neutralize Omicron BA.4 or BA.5. Thus, the need remains for continued vaccination-booster efforts, with innovation for vaccine and Mab improvement for broadly neutralizing activity. The usefulness of specific Mab applications links with the window of clinical opportunity when a cognate viral variant is present in the infected population.

SARS-CoV-2 RNA Is Readily Detectable at Least 8 Months after Shedding in an Isolation Facility

Environmental monitoring of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for research and public health purposes has grown exponentially throughout the coronavirus disease 2019 (COVID-19) pandemic. Monitoring wastewater for SARS-CoV-2 provides early warning signals of virus spread and information on trends in infections at a community scale. Indoor environmental monitoring (e.g., swabbing of surfaces and air filters) to identify potential outbreaks is less common, and the evidence for its utility is mixed. A significant challenge with surface and air filter monitoring in this context is the concern of "relic RNA," noninfectious RNA found in the environment that is not from recently deposited virus. Here, we report detection of SARS-CoV-2 RNA on surfaces in an isolation unit (a university dorm room) for up to 8 months after a COVID-19-positive individual vacated the space. Comparison of sequencing results from the same location over two time points indicated the presence of the entire viral genome, and sequence similarity confirmed a single source of the virus. Our findings highlight the need to develop approaches that account for relic RNA in environmental monitoring. IMPORTANCE Environmental monitoring of SARS-CoV-2 is rapidly becoming a key tool in infectious disease research and public health surveillance. Such monitoring offers a complementary and sometimes novel perspective on population-level incidence dynamics relative to that of clinical studies by potentially allowing earlier, broader, more affordable, less biased, and less invasive identification. Environmental monitoring can assist public health officials and others when deploying resources to areas of need and provides information on changes in the pandemic over time. Environmental surveillance of the genetic material of infectious agents (RNA and DNA) in wastewater became widely applied during the COVID-19 pandemic. There has been less research on other types of environmental samples, such as surfaces, which could be used to indicate that someone in a particular space was shedding virus. One challenge with surface surveillance is that the noninfectious genetic material from a pathogen (e.g., RNA from SARS-CoV-2) may be detected in the environment long after an infected individual has left the space. This study aimed to determine how long SARS-CoV-2 RNA could be detected in a room after a COVID-positive person had been housed there.

Combining Community Wastewater Genomic Surveillance with State Clinical Surveillance: A Framework for SARS-CoV-2 Public Health Practice

This study aimed to develop a framework for combining community wastewater surveillance with state clinical surveillance for the confirmation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants within the community and to provide recommendations on how to expand on such research and apply the findings in public health responses. Wastewater samples were collected weekly from 17 geographically resolved locations in Louisville/Jefferson County, Kentucky (USA), from February 10 to December 13, 2021. Genomic surveillance and quantitative reverse transcription PCR (RT-qPCR) platforms were used to screen for SARS-CoV-2 in wastewater, and state clinical surveillance was used for confirmation. The study results highlighted an increased epidemiological value of combining community wastewater genomic surveillance and RT-qPCR with conventional case-auditing methods. The spatial scale and temporal frequency of wastewater sampling provided promising sensitivity and specificity for gaining public health screening insights about SARS-CoV-2 emergence, seeding, and spread in communities. Improved national surveillance systems are needed against future pathogens and variants, and wastewater-based genomic surveillance exhibits great potential when coupled with clinical testing. This paper presents evidence that complementary wastewater and clinical testing are cost-effectively enhanced when used in combination, as they provide a strong tool for a joint public health framework. Future pathogens of interest may be examined in either a targeted fashion or using a more global approach where all pathogens are monitored. This study has also provided novel insights developed from evidence-based public health practices.

Genetic diversity and evolutionary convergence of cryptic SARS- CoV-2 lineages detected via wastewater sequencing

Wastewater-based epidemiology (WBE) is an effective way of tracking the appearance and spread of SARS-COV-2 lineages through communities. Beginning in early 2021, we implemented a targeted approach to amplify and sequence the receptor binding domain (RBD) of SARS-COV-2 to characterize viral lineages present in sewersheds. Over the course of 2021, we reproducibly detected multiple SARS-COV-2 RBD lineages that have never been observed in patient samples in 9 sewersheds located in 3 states in the USA. These cryptic lineages contained between 4 to 24 amino acid substitutions in the RBD and were observed intermittently in the sewersheds in which they were found for as long as 14 months. Many of the amino acid substitutions in these lineages occurred at residues also mutated in the Omicron variant of concern (VOC), often with the same substitutions. One of the sewersheds contained a lineage that appeared to be derived from the Alpha VOC, but the majority of the lineages appeared to be derived from pre-VOC SARS-COV-2 lineages. Specifically, several of the cryptic lineages from New York City appeared to be derived from a common ancestor that most likely diverged in early 2020. While the source of these cryptic lineages has not been resolved, it seems increasingly likely that they were derived from long-term patient infections or animal reservoirs. Our findings demonstrate that SARS-COV-2 genetic diversity is greater than what is commonly observed through routine SARS-CoV-2 surveillance. Wastewater sampling may more fully capture SARS-CoV-2 genetic diversity than patient sampling and could reveal new VOCs before they emerge in the wider human population.

Clinical Performance Characteristics of the Swift Normalase Amplicon Panel for Sensitive Recovery of Severe Acute Respiratory Syndrome Coronavirus 2 Genomes

Amplicon-based sequencing methods are central in characterizing the diversity, transmission, and evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but need to be rigorously assessed for clinical utility. Herein, we validated the Swift Biosciences' SARS-CoV-2 Swift Normalase Amplicon Panels using remnant clinical specimens. High-quality genomes meeting our established library and sequence quality criteria were recovered from positive specimens, with 95% limit of detection of 40.08 SARS-CoV-2 copies/PCR. Breadth of genome recovery was evaluated across a range of CT values (11.3 to 36.7; median, 21.6). Of 428 positive samples, 413 (96.5%) generated genomes with <10% unknown bases, with a mean genome coverage of 13,545× ± SD 8382×. No genomes were recovered from PCR-negative specimens (n = 30) or from specimens positive for non-SARS-CoV-2 respiratory viruses (n = 20). Compared with whole-genome shotgun metagenomic sequencing (n = 14) or Sanger sequencing for the spike gene (n = 11), pairwise identity between consensus sequences was 100% in all cases, with highly concordant allele frequencies (R2 = 0.99) between Swift and shotgun libraries. When samples from different clades were mixed at varying ratios, expected variants were detected even in 1:99 mixtures. When deployed as a clinical test, 268 tests were performed in the first 23 weeks, with a median turnaround time of 11 days, ordered primarily for outbreak investigations and infection control.

Rapid Detection and Characterization of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Omicron Variant in a Returning Traveler

We describe rapid detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant using targeted spike single-nucleotide polymorphism polymerase chain reaction and viral genome sequencing. This case occurred in a fully vaccinated and boosted returning traveler with mild symptoms who was identified through community surveillance rather than clinical care.

Dynamics of SARS-CoV-2 VOC neutralization and novel mAb reveal protection against Omicron

To evaluate SARS-CoV-2 variants we isolated SARS-CoV-2 temporally during the pandemic starting with first appearance of virus in the Western hemisphere near Seattle, WA, USA, and isolated each known major variant class, revealing the dynamics of emergence and complete take-over of all new cases by current Omicron variants. We assessed virus neutralization in a first-ever full comparison across variants and evaluated a novel monoclonal antibody (Mab). We found that convalescence greater than 5-months provides little-to-no protection against SARS-CoV-2 variants, vaccination enhances immunity against variants with the exception of Omicron BA.1, and paired testing of vaccine sera against ancestral virus compared to Omicron BA.1 shows that 3-dose vaccine regimen provides over 50-fold enhanced protection against Omicron BA.1 compared to a 2-dose regimen. We also reveal a novel Mab that effectively neutralizes Omicron BA.1 and BA.2 variants over clinically-approved Mabs. Our observations underscore the need for continued vaccination efforts, with innovation for vaccine and Mab improvement, for protection against variants of SARS-CoV-2.

Summary

We isolated SARS-CoV-2 temporally starting with emergence of virus in the Western hemisphere. Neutralization analyses across all variant lineages show that vaccine-boost regimen provides protection against Omicron BA.1. We reveal a Mab that protects against Omicron BA.1 and BA.2 variants.

Replicating RNA platform enables rapid response to the SARS-CoV-2 Omicron variant and elicits enhanced protection in naïve hamsters compared to ancestral vaccine

BACKGROUND

In late 2021, the SARS-CoV-2 Omicron (B.1.1.529) variant of concern (VoC) was reported with many mutations in the viral spike protein that were predicted to enhance transmissibility and allow viral escape of neutralizing antibodies. Within weeks of the first report of B.1.1.529, this VoC has rapidly spread throughout the world, replacing previously circulating strains of SARS-CoV-2 and leading to a resurgence in COVID-19 cases even in populations with high levels of vaccine- and infection-induced immunity. Studies have shown that B.1.1.529 is less sensitive to protective antibody conferred by previous infections and vaccines developed against earlier lineages of SARS-CoV-2. The ability of B.1.1.529 to spread even among vaccinated populations has led to a global public health demand for updated vaccines that can confer protection against B.1.1.529.

METHODS

We rapidly developed a replicating RNA vaccine expressing the B.1.1.529 spike and evaluated immunogenicity in mice and hamsters. We also challenged hamsters with B.1.1.529 and evaluated whether vaccination could protect against viral shedding and replication within respiratory tissue.

FINDINGS

We found that mice previously immunized with A.1-specific vaccines failed to elevate neutralizing antibody titers against B.1.1.529 following B.1.1.529-targeted boosting, suggesting pre-existing immunity may impact the efficacy of B.1.1.529-targeted boosters. Furthermore, we found that our B.1.1.529-targeted vaccine provides superior protection compared to the ancestral A.1-targeted vaccine in hamsters challenged with the B.1.1.529 VoC after a single dose of each vaccine.

INTERPRETATION

Our data suggest that B.1.1.529-targeted vaccines may provide superior protection against B.1.1.529 but pre-existing immunity and timing of boosting may need to be considered for optimum protection.

FUNDING

This research was supported in part by the Intramural Research Program, NIAID/NIH, Washington Research Foundation and by grants 27220140006C (JHE), AI100625, AI151698, and AI145296 (MG).

SARS-CoV-2 VOC type and biological sex affect molnupiravir efficacy in severe COVID-19 dwarf hamster model

SARS-CoV-2 variants of concern (VOC) have triggered infection waves. Oral antivirals such as molnupiravir promise to improve disease management, but efficacy against VOC delta was questioned and potency against omicron is unknown. This study evaluates molnupiravir against VOC in human airway epithelium organoids, ferrets, and a lethal Roborovski dwarf hamster model of severe COVID-19-like lung injury. VOC were equally inhibited by molnupiravir in cells and organoids. Treatment reduced shedding in ferrets and prevented transmission. Pathogenicity in dwarf hamsters was VOC-dependent and highest for delta, gamma, and omicron. All molnupiravir-treated dwarf hamsters survived, showing reduction in lung virus load from one (delta) to four (gamma) orders of magnitude. Treatment effect size varied in individual dwarf hamsters infected with omicron and was significant in males, but not females. The dwarf hamster model recapitulates mixed efficacy of molnupiravir in human trials and alerts that benefit must be reassessed in vivo as VOC evolve.

Molnupiravir was the first orally available SARS-CoV-2 antiviral approved for outpatient use against SARS-CoV-2, but its efficacy against variants of concern, especially delta, was questioned. Here the authors evaluate molnupiravir against variant of concern in numerous models, including human airway epithelium organoids, ferrets and Roborovski dwarf hamsters.

An outbreak of infection due to severe acute respiratory corona virus-2 in a neonatal unit from a low and middle income setting

Introduction

The provision of kangaroo mother care (KMC) involving continuous skin-to-skin care (SSC) is an important intervention in neonatal care, which is recommended even when women are infected with severe acute respiratory syndrome coronavirus (SARS-CoV-2). We report on a nosocomial outbreak of SARS-CoV-2 infections in a KMC ward.

Methods

Contact tracing was conducted following the diagnosis of SARS-CoV-2 in a mother lodging in the KMC ward. All mother-newborn dyads in the KMC and healthcare workers (HCW) were tested for SARS-CoV-2 within 24-72 h of diagnosing the index case. Nasopharyngeal swab samples were obtained and tested from contacts, with a nucleic acid amplification test (NAAT) assay. Next-generation sequencing was done on positive samples. The secondary attack rate (SAR) was calculated assuming that the mother who presented with symptoms was the source of infection.

Results

Twelve (70.6%) of 17 mothers and 8 (42.1%) of 19 neonates who were in the KMC ward with the index case were found to be positive with SARS-CoV-2. Seven (87.5%) of the 8 neonates who tested positive had mothers who also tested positive. Seventy-five percent (9/12) of the mothers and 62.5% (5/8) of the neonates who tested positive were asymptomatic. Eight (27.6%) of 29 HCW were found to be positive and were all asymptomatic. One neonate died from Acinetobacter baumannii sepsis, and his post-mortem lung histopathology showed features compatible with SARS-CoV-2 pneumonia. The sequencing of 13 specimens, which included 1 mother-newborn dyad, indicated clustering to the same phylogenetic lineage with identical mutations. In assessing for factors contributing to this outbreak, it was found that spaces between beds were less than 1 m and mothers had their meals around the same table at the same time.

Conclusion

We report on a nosocomial outbreak of SARS-CoV-2 in a KMC ward, affecting a high number of mothers and neonates, and to a lesser extent HCWs. Although it is difficult to point to the index case as the source of this outbreak, as asymptomatic individuals can spread infection, the inadequate adherence to non-pharmaceutical interventions was assessed to have contributed to the spread of infection. This highlights the need for awareness and adherence to mitigation strategies to avoid SARS-CoV-2 outbreaks.

A Method for Variant Agnostic Detection of SARS-CoV-2, Rapid Monitoring of Circulating Variants, and Early Detection of Emergent Variants Such as Omicron

The rapid emergence of SARS-CoV-2 variants raised public health questions concerning the capability of diagnostic tests to detect new strains, the efficacy of vaccines, and how to map the geographical distribution of variants to understand transmission patterns and loads on healthcare resources. Next-generation sequencing (NGS) is the primary method for detecting and tracing new variants, but it is expensive, and it can take weeks before sequence data are available in public repositories. This article describes a customizable reverse transcription PCR (RT-PCR)-based genotyping approach which is significantly less expensive, accelerates reporting, and can be implemented in any lab that performs RT-PCR. Specific single-nucleotide polymorphisms (SNPs) and indels were identified which had high positive-percent agreement (PPA) and negative-percent agreement (NPA) compared to NGS for the major genotypes that circulated through September 11, 2021. Using a 48-marker panel, testing on 1,031 retrospective SARS-CoV-2 positive samples yielded a PPA and NPA ranging from 96.3 to 100% and 99.2 to 100%, respectively, for the top 10 most prevalent World Health Organization (WHO) lineages during that time. The effect of reducing the quantity of panel markers was explored, and a 16-marker panel was determined to be nearly as effective as the 48-marker panel at lineage assignment. Responding to the emergence of Omicron, a genotyping panel was developed which distinguishes Delta and Omicron using four highly specific SNPs. The results demonstrate the utility of the condensed panel to rapidly track the growing prevalence of Omicron across the US in December 2021 and January 2022.

Efficacy of Parainfluenza Virus 5 (PIV5)-vectored Intranasal COVID-19 Vaccine as a Single Dose Vaccine and as a Booster against SARS-CoV-2 Variants

Immunization with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines has greatly reduced coronavirus disease 2019 (COVID-19)-related deaths and hospitalizations, but waning immunity and the emergence of variants capable of immune escape indicate the need for novel SARS-CoV-2 vaccines. An intranasal parainfluenza virus 5 (PIV5)-vectored COVID-19 vaccine CVXGA1 has been proven efficacious in animal models and blocks contact transmission of SARS-CoV-2 in ferrets. CVXGA1 vaccine is currently in human clinical trials in the United States. This work investigates the immunogenicity and efficacy of CVXGA1 and other PIV5-vectored vaccines expressing additional antigen SARS-CoV-2 nucleoprotein (N) or SARS-CoV-2 variant spike (S) proteins of beta, delta, gamma, and omicron variants against homologous and heterologous challenges in hamsters. A single intranasal dose of CVXGA1 induces neutralizing antibodies against SARS-CoV-2 WA1 (ancestral), delta variant, and omicron variant and protects against both homologous and heterologous virus challenges. Compared to mRNA COVID-19 vaccine, neutralizing antibody titers induced by CVXGA1 were well-maintained over time. When administered as a boost following two doses of a mRNA COVID-19 vaccine, PIV5-vectored vaccines expressing the S protein from WA1 (CVXGA1), delta, or omicron variants generate higher levels of cross-reactive neutralizing antibodies compared to three doses of a mRNA vaccine. In addition to the S protein, the N protein provides added protection as assessed by the highest body weight gain post-challenge infection. Our data indicates that PIV5-vectored COVID-19 vaccines, such as CVXGA1, can serve as booster vaccines against emerging variants.

Genetic Diversity and Evolutionary Convergence of Cryptic SARS-CoV-2 Lineages Detected Via Wastewater Sequencing

Wastewater-based epidemiology (WBE) is an effective way of tracking the appearance and spread of SARS-COV-2 lineages through communities. Beginning in early 2021, we implemented a targeted approach to amplify and sequence the receptor binding domain (RBD) of SARS-COV-2 to characterize viral lineages present in sewersheds. Over the course of 2021, we reproducibly detected multiple SARS-COV-2 RBD lineages that have never been observed in patient samples in 9 sewersheds located in 3 states in the USA. These cryptic lineages contained between 4 to 24 amino acid substitutions in the RBD and were observed intermittently in the sewersheds in which they were found for as long as 14 months. Many of the amino acid substitutions in these lineages occurred at residues also mutated in the Omicron variant of concern (VOC), often with the same substitution. One of the sewersheds contained a lineage that appeared to be derived from the Alpha VOC, but the majority of the lineages appeared to be derived from pre-VOC SARS-COV-2 lineages. Specifically, several of the cryptic lineages from New York City appeared to be derived from a common ancestor that most likely diverged in early 2020. While the source of these cryptic lineages has not been resolved, it seems increasingly likely that they were derived from immunocompromised patients or animal reservoirs. Our findings demonstrate that SARS-COV-2 genetic diversity is greater than what is commonly observed through routine SARS-CoV-2 surveillance. Wastewater sampling may more fully capture SARS-CoV-2 genetic diversity than patient sampling and could reveal new VOCs before they emerge in the wider human population.

Author Summary

During the COVID-19 pandemic, wastewater-based epidemiology has become an effective public health tool. Because many infected individuals shed SARS-CoV-2 in feces, wastewater has been monitored to reveal infection trends in the sewersheds from which the samples were derived. Here we report novel SARS-CoV-2 lineages in wastewater samples obtained from 3 different states in the USA. These lineages appeared in specific sewersheds intermittently over periods of up to 14 months, but generally have not been detected beyond the sewersheds in which they were initially found. Many of these lineages may have diverged in early 2020. Although these lineages share considerable overlap with each other, they have never been observed in patients anywhere in the world. While the wastewater lineages have similarities with lineages observed in long-term infections of immunocompromised patients, animal reservoirs cannot be ruled out as a potential source.

High-resolution analysis of long-term serum antibodies in humans following convalescence of SARS-CoV-2 infection

Long-term antibody responses to SARS-CoV-2 have focused on responses to full-length spike protein, specific domains within spike, or nucleoprotein. In this study, we used high-density peptide microarrays representing the complete proteome of SARS-CoV-2 to identify binding sites (epitopes) targeted by antibodies present in the blood of COVID-19 resolved cases at 5 months post-diagnosis. Compared to previous studies that evaluated epitope-specific responses early post-diagnosis (< 60 days), we found that epitope-specific responses to nucleoprotein and spike protein have contracted, and that responses to membrane protein have expanded. Although antibody titers to full-length spike and nucleoprotein remain steady over months, taken together our data suggest that the population of epitope-specific antibodies that contribute to this reactivity is dynamic and evolves over time. Further, the spike epitopes bound by polyclonal antibodies in COVID-19 convalescent serum samples aligned with known target sites that can neutralize viral activity suggesting that the maintenance of these antibodies might provide rapid serological immunity. Finally, the most dominant epitopes for membrane protein and spike showed high diagnostic accuracy providing novel biomarkers to refine blood-based antibody tests. This study provides new insights into the specific regions of SARS-CoV-2 targeted by serum antibodies long after infection.

Molecular Analysis of SARS-CoV-2 Lineages in Armenia

The sequencing of SARS-CoV-2 provides essential information on viral evolution, transmission, and epidemiology. In this paper, we performed the whole-genome sequencing of SARS-CoV-2 using nanopore and Illumina sequencing to describe the circulation of the virus lineages in Armenia. The analysis of 145 full genomes identified six clades (19A, 20A, 20B, 20I, 21J, and 21K) and considerable intra-clade PANGO lineage diversity. Phylodynamic and transmission analysis allowed to attribute specific clades as well as infer their importation routes. Thus, the first two waves of positive case increase were caused by the 20B clade, the third peak caused by the 20I (Alpha), while the last two peaks were caused by the 21J (Delta) and 21K (Omicron) variants. The functional analyses of mutations in sequences largely affected epitopes associated with protective HLA loci and did not cause the loss of the signal in PCR tests targeting ORF1ab and N genes as confirmed by RT-PCR. We also compared the performance of nanopore and Illumina short-read sequencing and showed the utility of nanopore sequencing as an efficient and affordable alternative for large-scale molecular epidemiology research. Thus, our paper describes new data on the genomic diversity of SARS-CoV-2 variants in Armenia in the global context of the virus molecular genomic surveillance.

COVID-19 Cases and Disease Severity in Pregnancy and Neonatal Positivity Associated With Delta (B.1.617.2) and Omicron (B.1.1.529) Variant Predominance

This study examines infections, illness severity, vaccinations, and early neonatal infections among obstetric patients during the pre-Delta, Delta, and Omicron periods of the COVID-19 pandemic.

Host-pathogen dynamics in longitudinal clinical specimens from patients with COVID-19

Rapid dissemination of SARS-CoV-2 sequencing data to public repositories has enabled widespread study of viral genomes, but studies of longitudinal specimens from infected persons are relatively limited. Analysis of longitudinal specimens enables understanding of how host immune pressures drive viral evolution in vivo. Here we performed sequencing of 49 longitudinal SARS-CoV-2-positive samples from 20 patients in Washington State collected between March and September of 2020. Viral loads declined over time with an average increase in RT-QPCR cycle threshold of 0.87 per day. We found that there was negligible change in SARS-CoV-2 consensus sequences over time, but identified a number of nonsynonymous variants at low frequencies across the genome. We observed enrichment for a relatively small number of these variants, all of which are now seen in consensus genomes across the globe at low prevalence. In one patient, we saw rapid emergence of various low-level deletion variants at the N-terminal domain of the spike glycoprotein, some of which have previously been shown to be associated with reduced neutralization potency from sera. In a subset of samples that were sequenced using metagenomic methods, differential gene expression analysis showed a downregulation of cytoskeletal genes that was consistent with a loss of ciliated epithelium during infection and recovery. We also identified co-occurrence of bacterial species in samples from multiple hospitalized individuals. These results demonstrate that the intrahost genetic composition of SARS-CoV-2 is dynamic during the course of COVID-19, and highlight the need for continued surveillance and deep sequencing of minor variants.

De novo emergence of a remdesivir resistance mutation during treatment of persistent SARS-CoV-2 infection in an immunocompromised patient: a case report

SARS-CoV-2 remdesivir resistance mutations have been generated in vitro but have not been reported in patients receiving treatment with the antiviral agent. We present a case of an immunocompromised patient with acquired B-cell deficiency who developed an indolent, protracted course of SARS-CoV-2 infection. Remdesivir therapy alleviated symptoms and produced a transient virologic response, but her course was complicated by recrudescence of high-grade viral shedding. Whole genome sequencing identified a mutation, E802D, in the nsp12 RNA-dependent RNA polymerase, which was not present in pre-treatment specimens. In vitro experiments demonstrated that the mutation conferred a ~6-fold increase in remdesivir IC₅₀ but resulted in a fitness cost in the absence of remdesivir. Sustained clinical and virologic response was achieved after treatment with casirivimab-imdevimab. Although the fitness cost observed in vitro may limit the risk posed by E802D, this case illustrates the importance of monitoring for remdesivir resistance and the potential benefit of combinatorial therapies in immunocompromised patients with SARS-CoV-2 infection.

Here, the authors identify and validate the emergence of a SARS-CoV-2 resistance mutation to Remdesivir, associated with virological recrudesce in an immunocompromised patient with persistent COVID-19.

Mutations in viral nucleocapsid protein and endoRNase are discovered to associate with COVID19 hospitalization risk

SARS-CoV-2 is spreading worldwide with continuously evolving variants, some of which occur in the Spike protein and appear to increase viral transmissibility. However, variants that cause severe COVID-19 or lead to other breakthroughs have not been well characterized. To discover such viral variants, we assembled a cohort of 683 COVID-19 patients; 388 inpatients ("cases") and 295 outpatients ("controls") from April to August 2020 using electronically captured COVID test request forms and sequenced their viral genomes. To improve the analytical power, we accessed 7137 viral sequences in Washington State to filter out viral single nucleotide variants (SNVs) that did not have significant expansions over the collection period. Applying this filter led to the identification of 53 SNVs that were statistically significant, of which 13 SNVs each had 3 or more variant copies in the discovery cohort. Correlating these selected SNVs with case/control status, eight SNVs were found to significantly associate with inpatient status (q-values < 0.01). Using temporal synchrony, we identified a four SNV-haplotype (t19839-g28881-g28882-g28883) that was significantly associated with case/control status (Fisher's exact p = 2.84 × 10-11). This haplotype appeared in April 2020, peaked in June, and persisted into January 2021. The association was replicated (OR = 5.46, p-value = 4.71 × 10-12) in an independent cohort of 964 COVID-19 patients (June 1, 2020 to March 31, 2021). The haplotype included a synonymous change N73N in endoRNase, and three non-synonymous changes coding residues R203K, R203S and G204R in the nucleocapsid protein. This discovery points to the potential functional role of the nucleocapsid protein in triggering "cytokine storms" and severe COVID-19 that led to hospitalization. The study further emphasizes a need for tracking and analyzing viral sequences in correlations with clinical status.

Trajectory of Viral RNA Load Among Persons With Incident SARS-CoV-2 G614 Infection (Wuhan Strain) in Association With COVID-19 Symptom Onset and Severity

IMPORTANCE

The SARS-CoV-2 viral trajectory has not been well characterized in incident infections. These data are needed to inform natural history, prevention practices, and therapeutic development.

OBJECTIVE

To characterize early SARS-CoV-2 viral RNA load (hereafter referred to as viral load) in individuals with incident infections in association with COVID-19 symptom onset and severity.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study was a secondary data analysis of a remotely conducted study that enrolled 829 asymptomatic community-based participants recently exposed (<96 hours) to persons with SARS-CoV-2 from 41 US states from March 31 to August 21, 2020. Two cohorts were studied: (1) participants who were SARS-CoV-2 negative at baseline and tested positive during study follow-up, and (2) participants who had 2 or more positive swabs during follow-up, regardless of the initial (baseline) swab result. Participants collected daily midturbinate swab samples for SARS-CoV-2 RNA detection and maintained symptom diaries for 14 days.

EXPOSURE

Laboratory-confirmed SARS-CoV-2 infection.

MAIN OUTCOMES AND MEASURES

The observed SARS-CoV-2 viral load among incident infections was summarized, and piecewise linear mixed-effects models were used to estimate the characteristics of viral trajectories in association with COVID-19 symptom onset and severity.

RESULTS

A total of 97 participants (55 women [57%]; median age, 37 years [IQR, 27-52 years]) developed incident infections during follow-up. Forty-two participants (43%) had viral shedding for 1 day (median peak viral load cycle threshold [Ct] value, 38.5 [95% CI, 38.3-39.0]), 18 (19%) for 2 to 6 days (median Ct value, 36.7 [95% CI, 30.2-38.1]), and 31 (32%) for 7 days or more (median Ct value, 18.3 [95% CI, 17.4-22.0]). The cycle threshold value has an inverse association with viral load. Six participants (6%) had 1 to 6 days of viral shedding with censored duration. The peak mean (SD) viral load was observed on day 3 of shedding (Ct value, 33.8 [95% CI, 31.9-35.6]). Based on the statistical models fitted to 129 participants (60 men [47%]; median age, 38 years [IQR, 25-54 years]) with 2 or more SARS-CoV-2-positive swab samples, persons reporting moderate or severe symptoms tended to have a higher peak mean viral load than those who were asymptomatic (Ct value, 23.3 [95% CI, 22.6-24.0] vs 30.7 [95% CI, 29.8-31.4]). Mild symptoms generally started within 1 day of peak viral load, and moderate or severe symptoms 2 days after peak viral load. All 535 sequenced samples detected the G614 variant (Wuhan strain).

CONCLUSIONS AND RELEVANCE

This cohort study suggests that having incident SARS-CoV-2 G614 infection was associated with a rapid viral load peak followed by slower decay. COVID-19 symptom onset generally coincided with peak viral load, which correlated positively with symptom severity. This longitudinal evaluation of the SARS-CoV-2 G614 with frequent molecular testing serves as a reference for comparing emergent viral lineages to inform clinical trial designs and public health strategies to contain the spread of the virus.

NGSocomial Infections: High-Resolution Views of Hospital-Acquired Infections Through Genomic Epidemiology

Hospital outbreak investigations are high-stakes epidemiology. Contacts between staff and patients are numerous; environmental and community exposures are plentiful; and patients are highly vulnerable. Having the best data is paramount to understanding an outbreak in order to stop ongoing transmission and prevent future outbreaks. In the past 5 years, the high-resolution view of transmission offered by analyzing pathogen whole-genome sequencing (WGS) is increasingly part of hospital outbreak investigations. Concerns over speed and actionability, assay validation, liability, cost, and payment models lead to further opportunities for work in this area. Now accelerated by funding for COVID-19, the use of genomics in hospital outbreak investigations has firmly moved from the academic literature to more quotidian operations, with associated concerns involving regulatory affairs, data integration, and clinical interpretation. This review details past uses of WGS data in hospital-acquired infection outbreaks as well as future opportunities to increase its utility and growth in hospital infection prevention.

De novo emergence of a remdesivir resistance mutation during treatment of persistent SARS-CoV-2 infection in an immunocompromised patient: A case report

SARS-CoV-2 remdesivir resistance mutations have been generated in vitro but have not been reported in patients receiving treatment with the antiviral agent. We present a case of an immunocompromised patient with acquired B-cell deficiency who developed an indolent, protracted course of SARS-CoV-2 infection. Remdesivir therapy alleviated symptoms and produced a transient virologic response, but her course was complicated by recrudescence of high-grade viral shedding. Whole genome sequencing identified a mutation, E802D, in the nsp12 RNA-dependent RNA polymerase, which was not present in pre-treatment specimens. In vitro experiments demonstrated that the mutation conferred a ∼6-fold increase in remdesivir IC50 but resulted in a fitness cost in the absence of remdesivir. Sustained clinical and virologic response was achieved after treatment with casirivimab-imdevimab. Although the fitness cost observed in vitro may limit the risk posed by E802D, this case illustrates the importance of monitoring for remdesivir resistance and the potential benefit of combinatorial therapies in immunocompromised patients with SARS-CoV-2 infection.

Whole-Genome Sequencing of SARS-CoV-2: Assessment of the Ion Torrent AmpliSeq Panel and Comparison with the Illumina MiSeq ARTIC Protocol

Fast and effective methods are needed for sequencing of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genome to track genetic mutations and to identify new and emerging variants during the ongoing pandemic. The objectives were to assess the performance of the SARS-CoV-2 AmpliSeq research panel and S5 plug-in analysis tools for whole-genome sequencing analysis of SARS-CoV-2 and to compare the results with those obtained with the MiSeq-based ARTIC analysis pipeline, using metrics such as depth, coverage, and concordance of single-nucleotide variant (SNV) calls. A total of 191 clinical specimens and a single cultured isolate were extracted and sequenced with AmpliSeq technology and analysis tools. Of the 191 clinical specimens, 83 (with threshold cycle [C_T] values of 15.58 to 32.54) were also sequenced using an Illumina MiSeq-based method with the ARTIC analysis pipeline, for direct comparison. A total of 176 of the 191 clinical specimens sequenced on the S5XL system and prepared using the SARS-CoV-2 research panel had nearly complete coverage (>98%) of the viral genome, with an average depth of 5,031×. Similar coverage levels (>98%) were observed for 81/83 primary specimens that were sequenced with both methods tested. The sample with the lowest viral load (C_T value of 32.54) achieved 89% coverage using the MiSeq method and failed to sequence with the AmpliSeq method. Consensus sequences produced by each method were identical for 81/82 samples in areas of equal coverage, with a single difference present in one sample. The AmpliSeq approach is as effective as the Illumina-based method using ARTIC v3 amplification for sequencing SARS-CoV-2 directly from patient specimens across a range of viral loads (C_T values of 15.56 to 32.54 [median, 22.18]). The AmpliSeq workflow is very easily automated with the Ion Chef and S5 instruments and requires less training and experience with next-generation sequencing sample preparation than the Illumina workflow.

Oral prodrug of remdesivir parent GS-441524 is efficacious against SARS-CoV-2 in ferrets

Remdesivir is an antiviral approved for COVID-19 treatment, but its wider use is limited by intravenous delivery. An orally bioavailable remdesivir analog may boost therapeutic benefit by facilitating early administration to non-hospitalized patients. This study characterizes the anti-SARS-CoV-2 efficacy of GS-621763, an oral prodrug of remdesivir parent nucleoside GS-441524. Both GS-621763 and GS-441524 inhibit SARS-CoV-2, including variants of concern (VOC) in cell culture and human airway epithelium organoids. Oral GS-621763 is efficiently converted to plasma metabolite GS-441524, and in lungs to the triphosphate metabolite identical to that generated by remdesivir, demonstrating a consistent mechanism of activity. Twice-daily oral administration of 10 mg/kg GS-621763 reduces SARS-CoV-2 burden to near-undetectable levels in ferrets. When dosed therapeutically against VOC P.1 gamma γ, oral GS-621763 blocks virus replication and prevents transmission to untreated contact animals. These results demonstrate therapeutic efficacy of a much-needed orally bioavailable analog of remdesivir in a relevant animal model of SARS-CoV-2 infection.

Remdesivir is an approved antiviral treatment for COVID-19, but it needs to be administered intravenously. Here, Cox et al. show that GS-621763, a prodrug of remdesivir parent nucleoside GS-441524 has good oral bioavailability and inhibits SARS-CoV-2 and variants of concerns in ferrets.

Clinical and Infection Prevention Applications of SARS-CoV-2 Genotyping: an IDSA/ASM Consensus Review Document

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged into a world of maturing pathogen genomics, with more than 2 million genomes sequenced at the time of writing. The rise of more transmissible variants of concern that impact vaccine and therapeutic effectiveness has led to widespread interest in SARS-CoV-2 evolution. Clinicians are also eager to take advantage of the information provided by SARS-CoV-2 genotyping beyond surveillance purposes. Here, we review the potential role of SARS-CoV-2 genotyping in clinical care. The review covers clinical use cases for SARS-CoV-2 genotyping, methods of SARS-CoV-2 genotyping, assay validation and regulatory requirements, and clinical reporting for laboratories, as well as emerging issues in clinical SARS-CoV-2 sequencing. While clinical uses of SARS-CoV-2 genotyping are currently limited, rapid technological change along with a growing ability to interpret variants in real time foretells a growing role for SARS-CoV-2 genotyping in clinical care as continuing data emerge on vaccine and therapeutic efficacy.

Clinical and Infection Prevention Applications of SARS-CoV-2 Genotyping: An IDSA/ASM Consensus Review Document

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged into a world of maturing pathogen genomics, with >2 million genomes sequenced at this writing. The rise of more transmissible variants of concern that affect vaccine and therapeutic effectiveness has led to widespread interest in SARS-CoV-2 evolution. Clinicians are also eager to take advantage of the information provided by SARS-CoV-2 genotyping beyond surveillance purposes. Here, we review the potential role of SARS-CoV-2 genotyping in clinical care. The review covers clinical use cases for SARS-CoV-2 genotyping, methods of SARS-CoV-2 genotyping, assay validation and regulatory requirements, clinical reporting for laboratories, and emerging issues in clinical SARS-CoV-2 sequencing. While clinical uses of SARS-CoV-2 genotyping are currently limited, rapid technological change along with a growing ability to interpret variants in real time foretell a growing role for SARS-CoV-2 genotyping in clinical care as continuing data emerge on vaccine and therapeutic efficacy.

Specific allelic discrimination of N501Y and other SARS-CoV-2 mutations by ddPCR detects B.1.1.7 lineage in Washington State

Real-time epidemiological tracking of variants of concern (VOCs) can help limit the spread of more contagious forms of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), such as those containing the N501Y mutation. Typically, genetic sequencing is required to be able to track VOCs in real-time. However, sequencing can take time and may not be accessible in all laboratories. Genotyping by RT-ddPCR offers an alternative to rapidly detect VOCs through discrimination of specific alleles such as N501Y, which is associated with increased transmissibility and virulence. Here we describe the first cases of the B.1.1.7 lineage of SARS-CoV-2 detected in Washington State by using a combination of reverse-transcription polymerase chain reaction (RT-PCR), RT-ddPCR, and next-generation sequencing. We initially screened 1035 samples positive for SARS-CoV-2 by our CDC-based laboratory-developed assay using ThermoFisher's multiplex RT-PCR COVID-19 assay over four weeks from late December 2020 to early January 2021. S gene target failures (SGTF) were subsequently assayed by RT-ddPCR to confirm four mutations within the S gene associated with the B.1.1.7 lineage: a deletion at amino acid (AA) 69-70 (ACATGT), deletion at AA 145, (TTA), N501Y mutation (TAT), and S982A mutation (GCA). All four targets were detected in two specimens; follow-up sequencing revealed a total of 9 mutations in the S gene and phylogenetic clustering within the B.1.1.7 lineage. Next, we continued screening samples for SGTF detecting 23 additional B.1.1.7 variants by RT-ddPCR and confirmed by sequencing. As VOCs become increasingly prevalent, molecular diagnostic tools like RT-ddPCR can be utilized to quickly, accurately, and sensitively distinguish more contagious lineages of SARS-CoV-2.

Fast SARS-CoV-2 Variant Detection Using Snapback Primer High-Resolution Melting

SARS-CoV-2, the virus responsible for COVID-19, emerged in late 2019 and has since spread throughout the world, infecting over 200 million people. The fast spread of SARS-CoV-2 showcased the need for rapid and sensitive testing methodologies to help track the disease. Over the past 18 months, numerous SARS-CoV-2 variants have emerged. Many of these variants are suggested to be more transmissible as well as less responsive to neutralization by vaccine-induced antibodies. Viral whole-genome sequencing is the current standard for tracking these variants. However, whole-genome sequencing is costly and the technology and expertise are limited to larger reference laboratories. Here, we present the feasibility of a fast, inexpensive methodology using snapback primer-based high-resolution melting to test for >20 high-consequence SARS-CoV-2 spike mutations. This assay can distinguish between multiple variant lineages and be completed in roughly 2 h for less than $10 per sample.

Assessment of a Program for SARS-CoV-2 Screening and Environmental Monitoring in an Urban Public School District

IMPORTANCE

Scalable programs for school-based SARS-CoV-2 testing and surveillance are needed to guide in-person learning practices and inform risk assessments in kindergarten through 12th grade settings.

OBJECTIVES

To characterize SARS-CoV-2 infections in staff and students in an urban public school setting and evaluate test-based strategies to support ongoing risk assessment and mitigation for kindergarten through 12th grade in-person learning.

DESIGN, SETTING, AND PARTICIPANTS

This pilot quality improvement program engaged 3 schools in Omaha, Nebraska, for weekly saliva polymerase chain reaction testing of staff and students participating in in-person learning over a 5-week period from November 9 to December 11, 2020. Wastewater, air, and surface samples were collected weekly and tested for SARS-CoV-2 RNA to evaluate surrogacy for case detection and interrogate transmission risk of in-building activities.

MAIN OUTCOMES AND MEASURES

SARS-CoV-2 detection in saliva and environmental samples and risk factors for SARS-CoV-2 infection.

RESULTS

A total of 2885 supervised, self-collected saliva samples were tested from 458 asymptomatic staff members (mean [SD] age, 42.9 [12.4] years; 303 women [66.2%]; 25 Black or African American [5.5%], 83 Hispanic [18.1%], 312 White [68.1%], and 35 other or not provided [7.6%]) and 315 students (mean age, 14.2 [0.7] years; 151 female students [48%]; 20 Black or African American [6.3%], 201 Hispanic [63.8%], 75 White [23.8%], and 19 other race or not provided [6.0%]). A total of 46 cases of SARS-CoV-2 (22 students and 24 staff members) were detected, representing an increase in cumulative case detection rates from 1.2% (12 of 1000) to 7.0% (70 of 1000) among students and from 2.1% (21 of 1000) to 5.3% (53 of 1000) among staff compared with conventional reporting mechanisms during the pilot period. SARS-CoV-2 RNA was detected in wastewater samples from all pilot schools as well as in air samples collected from 2 choir rooms. Sequencing of 21 viral genomes in saliva specimens demonstrated minimal clustering associated with 1 school. Geographical analysis of SARS-CoV-2 cases reported district-wide demonstrated higher community risk in zip codes proximal to the pilot schools.

CONCLUSIONS AND RELEVANCE

In this study of staff and students in 3 urban public schools in Omaha, Nebraska, weekly screening of asymptomatic staff and students by saliva polymerase chain reaction testing was associated with increased SARS-CoV-2 case detection, exceeding infection rates reported at the county level. Experiences differed among schools, and virus sequencing and geographical analyses suggested a dynamic interplay of school-based and community-derived transmission risk. Collectively, these findings provide insight into the performance and community value of test-based SARS-CoV-2 screening and surveillance strategies in the kindergarten through 12th grade educational setting.

Anti-SARS-CoV-2 Antibody Levels Measured by the AdviseDx SARS-CoV-2 Assay Are Concordant with Previously Available Serologic Assays but Are Not Fully Predictive of Sterilizing Immunity

With the availability of widespread SARS-CoV-2 vaccination, high-throughput quantitative anti-spike protein serological testing will likely become increasingly important. Here, we investigated the performance characteristics of the recently FDA-authorized semiquantitative anti-spike protein AdviseDx SARS-CoV-2 IgG II assay compared to the FDA-authorized anti-nucleocapsid protein Abbott Architect SARS-CoV-2 IgG, Roche Elecsys anti-SARS-CoV-2-S, EuroImmun anti-SARS-CoV-2 enzyme-linked immunosorbent assay (ELISA), and GenScript surrogate virus neutralization assays and examined the humoral response associated with vaccination, natural protection, and vaccine breakthrough infection. The AdviseDx assay had a clinical sensitivity at 14 days after symptom onset or 10 days after PCR detection of 95.6% (65/68; 95% confidence interval [CI], 87.8 to 98.8%), with two discrepant individuals seroconverting shortly thereafter. The AdviseDx assay demonstrated 100% positive percent agreement with the four other assays examined using the same symptom onset or PCR detection cutoffs. Using a recently available WHO international standard for anti-SARS-CoV-2 antibody, we provide assay unit conversion factors to international units for each of the assays examined. We performed a longitudinal survey of healthy vaccinated individuals, finding that median AdviseDx immunoglobulin levels peaked 7 weeks after first vaccine dose at approximately 4,000 IU/ml. Intriguingly, among the five assays examined, there was no significant difference in antigen binding level or neutralizing activity between two seropositive patients protected against SARS-CoV-2 infection in a previously described fishing vessel outbreak and five health care workers who experienced vaccine breakthrough of SARS-CoV-2 infection, all with variants of concern. These findings suggest that protection against SARS-CoV-2 infection cannot currently be predicted exclusively using in vitro antibody assays against wild-type SARS-CoV-2 spike. Further work is required to establish protective correlates for SARS-CoV-2 infection.

A SARS-CoV-2 Nucleocapsid Variant that Affects Antigen Test Performance

More than one year into a global pandemic, SARS-CoV-2 is now defined by a variety of rapidly evolving variant lineages. Several FDA authorized molecular diagnostic tests have been impacted by viral variation, while no reports of viral variation affecting antigen test performance have occurred to date. While determining the analytical sensitivity of the Quidel Sofia SARS Antigen FIA test (Sofia 2), we uncovered a high viral load specimen that repeatedly tested negative by this antigen test. Whole genome sequencing of the specimen uncovered two mutations, T205I and D399N, present in the nucleocapsid protein of the isolate. All six SARS-CoV-2 positive clinical specimens available in our laboratory with a D399N nucleocapsid mutation and C_T < 31 were not detected by the Sofia 2 but detected by the Abbott BinaxNOW COVID-19 Ag Card, while clinical specimens with the T205I mutation were detected by both assays. Testing of recombinant SARS-CoV-2 nucleocapsid with these variants demonstrated an approximate 1000-fold loss in sensitivity for the Quidel Sofia SARS Antigen FIA test associated with the D399N mutation, while the BinaxNOW and Quidel Quickvue SARS Antigen tests were unaffected by the mutation. The D399N nucleocapsid mutation has been relatively uncommon to date, appearing in only 0.02% of genomes worldwide at time of writing. Our results demonstrate how routine pathogen genomics can be integrated into the clinical microbiology laboratory to investigate diagnostic edge cases, as well as the importance of profiling antigenic diversity outside of the spike protein for SARS-CoV-2 diagnostics.

Variants of concern are overrepresented among post-vaccination breakthrough infections of SARS-CoV-2 in Washington State

Across 20 vaccine breakthrough cases detected at our institution, all 20 (100%) infections were due to variants of concern (VOCs) and had a median Ct of 20.2 (IQR, 17.1–23.3). When compared with 5174 contemporaneous samples sequenced in our laboratory, VOCs were significantly enriched among breakthrough infections (P < .05).

A SARS-CoV-2 Nucleocapsid Variant that Affects Antigen Test Performance

More than one year into a global pandemic, SARS-CoV-2 is now defined by a variety of rapidly evolving variant lineages. Several FDA authorized molecular diagnostic tests have been impacted by viral variation, while no reports of viral variation affecting antigen test performance have occurred to date. While determining the analytical sensitivity of the Quidel Sofia SARS Antigen FIA test (Sofia 2), we uncovered a high viral load specimen that repeatedly tested negative by this antigen test. Whole genome sequencing of the specimen uncovered two mutations, T205I and D399N, present in the nucleocapsid protein of the isolate. All six SARS-CoV-2 positive clinical specimens available in our laboratory with a D399N nucleocapsid mutation and C_T < 31 were not detected by the Sofia 2 but detected by the Abbott BinaxNOW COVID-19 Ag Card, while clinical specimens with the T205I mutation were detected by both assays. Testing of recombinant SARS-CoV-2 nucleocapsid with these variants demonstrated an approximate 1000-fold loss in sensitivity for the Quidel Sofia SARS Antigen FIA test associated with the D399N mutation, while the BinaxNOW and Quidel Quickvue SARS Antigen tests were unaffected by the mutation. The D399N nucleocapsid mutation has been relatively uncommon to date, appearing in only 0.02% of genomes worldwide at time of writing. Our results demonstrate how routine pathogen genomics can be integrated into the clinical microbiology laboratory to investigate diagnostic edge cases, as well as the importance of profiling antigenic diversity outside of the spike protein for SARS-CoV-2 diagnostics.

Rapid High-Throughput Whole-Genome Sequencing of SARS-CoV-2 by Using One-Step Reverse Transcription-PCR Amplification with an Integrated Microfluidic System and Next-Generation Sequencing

The long-lasting global COVID-19 pandemic demands timely genomic investigation of SARS-CoV-2 viruses. Here, we report a simple and efficient workflow for whole-genome sequencing utilizing one-step reverse transcription-PCR (RT-PCR) amplification on a microfluidic platform, followed by MiSeq amplicon sequencing.

The long-lasting global COVID-19 pandemic demands timely genomic investigation of SARS-CoV-2 viruses. Here, we report a simple and efficient workflow for whole-genome sequencing utilizing one-step reverse transcription-PCR (RT-PCR) amplification on a microfluidic platform, followed by MiSeq amplicon sequencing. The method uses Fluidigm integrated fluidic circuit (IFC) and instruments to amplify 48 samples with 39 pairs of primers, including 35 custom-designed primer pairs and four additional primer pairs from the ARTIC network protocol v3. Application of this method on RNA samples from both viral isolates and clinical specimens demonstrates robustness and efficiency in obtaining the full genome sequence of SARS-CoV-2.

SARS-CoV-2 ORF6 Disrupts Bidirectional Nucleocytoplasmic Transport through Interactions with Rae1 and Nup98

RNA viruses that replicate in the cytoplasm often disrupt nucleocytoplasmic transport to preferentially translate their own transcripts and prevent host antiviral responses. The Sarbecovirus accessory protein ORF6 has previously been shown to be a major inhibitor of interferon production in both severe acute respiratory syndrome coronavirus (SARS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, we show SARS-CoV-2-infected cells display an elevated level of nuclear mRNA accumulation compared to mock-infected cells. We demonstrate that ORF6 is responsible for this nuclear imprisonment of host mRNA, and using a cotransfected reporter assay, we show this nuclear retention of mRNA blocks expression of newly transcribed mRNAs. ORF6's nuclear entrapment of host mRNA is associated with its ability to copurify with the mRNA export factors, Rae1 and Nup98. These protein-protein interactions map to the C terminus of ORF6 and can be abolished by a single amino acid mutation in Met58. Overexpression of Rae1 restores reporter expression in the presence of SARS-CoV-2 ORF6. SARS-CoV ORF6 also interacts with Rae1 and Nup98. However, SARS-CoV-2 ORF6 more strongly copurifies with Rae1 and Nup98 and results in significantly reduced expression of reporter proteins compared to SARS-CoV ORF6, a potential mechanism for the delayed symptom onset and presymptomatic transmission uniquely associated with the SARS-CoV-2 pandemic. We also show that both SARS-CoV and SARS-CoV-2 ORF6 block nuclear import of a broad range of host proteins. Together, these data support a model in which ORF6 clogs the nuclear pore through its interactions with Rae1 and Nup98 to prevent both nuclear import and export, rendering host cells incapable of responding to SARS-CoV-2 infection.IMPORTANCE SARS-CoV-2, the causative agent of coronavirus disease 2019 (COVID-19), is an RNA virus with a large genome that encodes multiple accessory proteins. While these accessory proteins are not required for growth in vitro, they can contribute to the pathogenicity of the virus. We demonstrate that SARS-CoV-2-infected cells accumulate poly(A) mRNA in the nucleus, which is attributed to the accessory protein ORF6. Nuclear entrapment of mRNA and reduced expression of newly transcribed reporter proteins are associated with ORF6's interactions with the mRNA export proteins Rae1 and Nup98. SARS-CoV ORF6 also shows the same interactions with Rae1 and Nup98. However, SARS-CoV-2 ORF6 more strongly represses reporter expression and copurifies with Rae1 and Nup98 compared to SARS-CoV ORF6. Both SARS-CoV ORF6 and SARS-CoV-2 ORF6 block nuclear import of a wide range of host factors through interactions with Rae1 and Nup98. Together, our results suggest ORF6's disruption of nucleocytoplasmic transport prevents infected cells from responding to the invading virus.

Novel Multiplexed Amplicon-Based Sequencing to Quantify SARS-CoV-2 RNA from Wastewater

The application of wastewater-based epidemiology (WBE) to support the global response to the COVID-19 pandemic has shown encouraging outcomes. The accurate, sensitive, and high-throughput detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in municipal wastewater is critical for WBE. Here, we present a novel approach based on multiplexed amplicon-based sequencing, namely the ATOPlex platform, for detecting SARS-CoV-2. The ATOPlex platform is capable of quantifying SARS-CoV-2 RNA at concentrations that are at least 1 order of magnitude lower than the detection limit of reverse transcription quantitative polymerase chain reaction (RT-qPCR). Robust and accurate phylogenetic placement can be done at viral concentrations 4 times lower than the detection limit of RT-qPCR. We further found that the solid fraction in wastewater harbors a considerable amount of viral RNA, highlighting the need to extract viral RNA from the solid and liquid fractions of wastewater. This study delivers a highly sensitive, phylogenetically informative, and high-throughput analytical workflow that facilitates the application of WBE.

Cross-reactive memory T cells and herd immunity to SARS-CoV-2

Immunity is a multifaceted phenomenon. For T cell-mediated memory responses to SARS-CoV-2, it is relevant to consider their impact both on COVID-19 disease severity and on viral spread in a population. Here, we reflect on the immunological and epidemiological aspects and implications of pre-existing cross-reactive immune memory to SARS-CoV-2, which largely originates from previous exposure to circulating common cold coronaviruses. We propose four immunological scenarios for the impact of cross-reactive CD4+ memory T cells on COVID-19 severity and viral transmission. For each scenario, we discuss its implications for the dynamics of herd immunity and on projections of the global impact of SARS-CoV-2 on the human population, and assess its plausibility. In sum, we argue that key potential impacts of cross-reactive T cell memory are already incorporated into epidemiological models based on data of transmission dynamics, particularly with regard to their implications for herd immunity. The implications of immunological processes on other aspects of SARS-CoV-2 epidemiology are worthy of future study.