Intra-host non-synonymous diversity at a neutralizing antibody epitope of SARS-CoV-2 spike protein N-terminal domain

The significance of recurrent de novo amino acid substitutions that emerged during chronic SARS-CoV-2 infection: an observational study

BACKGROUND

De novo amino acid substitutions (DNS) frequently emerge among immunocompromised patients with chronic SARS-CoV-2 infection. While previous studies have reported these DNS, their significance has not been systematically studied.

METHODS

We performed a review of DNS that emerged during chronic SARS-CoV-2 infection. We searched PubMed until June 2023 using the keywords "(SARS-CoV-2 or COVID-19) and (mutation or sequencing) and ((prolonged infection) or (chronic infection) or (long term))". We included patients with chronic SARS-CoV-2 infection who had SARS-CoV-2 sequencing performed for at least 3 time points over at least 60 days. We also included 4 additional SARS-CoV-2 patients with chronic infection of our hospital not reported previously. We determined recurrent DNS that has appeared in multiple patients and determined the significance of these mutations among epidemiologically-significant variants.

FINDINGS

A total of 34 cases were analyzed, including 30 that were published previously and 4 from our hospital. Twenty two DNS appeared in ≥3 patients, with 14 (64%) belonging to lineage-defining mutations (LDMs) of epidemiologically-significant variants and 10 (45%) emerging among chronically-infected patients before the appearance of the corresponding variant. Notably, nsp9-T35I substitution (Orf1a T4175I) emerged in all three patients with BA.2.2 infection in 2022 before the appearance of Variants of Interest that carry nsp9-T35I as LDM (EG.5 and BA.2.86/JN.1). Structural analysis suggests that nsp9-T35I substitution may affect nsp9-nsp12 interaction, which could be critical for the function of the replication and transcription complex.

INTERPRETATION

DNS that emerges recurrently in different chronically-infected patients may be used as a marker for potential epidemiologically-significant variants.

FUNDING

Theme-Based Research Scheme [T11/709/21-N] of the Research Grants Council (See acknowledgements for full list).

Epidemiology of COVID-19 outbreaks in aged care facilities during postvaccine period: a systematic review and meta-analysis

OBJECTIVE

We aimed to define the epidemiology of COVID-19 outbreaks in aged care facilities (ACFs) during the postvaccine period, including vaccine effectiveness (VE) for this high-risk group.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Ovid Medline, Ovid Embase, Scopus, Web of Science and Cochrane databases were searched through 1 September 2023.

ELIGIBILITY CRITERIA

Any original observational studies and trials reporting data on COVID-19 outbreaks among the partially/fully vaccinated residents from ACFs during or after the worldwide implementation of vaccine roll-out.

DATA EXTRACTION AND SYNTHESIS

We estimated the attack rate, case fatality rate, mortality rate and VE during postvaccine period. Random effect model was adopted for meta-analysis. Quality assessment on all included studies was performed using the Meta Quality Appraisal Tool.

RESULTS

38 articles were included from 12 countries reporting 79 outbreaks with 1708 confirmed cases of COVID-19 from 78 ACFs. The pooled attack rate was 28% (95% CI 20% to 37%) among the fully vaccinated residents. Two-thirds (62.5%) of the index cases were unvaccinated healthcare professionals (eg, physicians, nurses) and caregivers. Unvaccinated residents had a significantly higher rates (12%) (95% CI 7% to 19%) of mortality compared with the vaccinated residents (2%) (95% CI% 1 to 4%) and the post-COVID-19 vaccine estimates for case fatality rate (13% vs 23%) and hospitalisation rate (17% vs 37%) were substantially lower. VE in preventing disease among residents in ACFs was 73% (95% CI 49% to 86). Overall, the included studies were heterogeneous in nature, however, the risk of bias was low to moderate.

CONCLUSIONS

Our study reaffirmed the impact of vaccination as a key public health measure to minimise the burden of COVID-19 in ACFs. Facilities with higher crowding indexes should be prioritised for vaccination and should advocate for higher vaccination targets among staff and residents as a critical intervention strategy to minimise disease burden in this vulnerable population.

Toehold switch plus signal amplification enables rapid detection

Recent world events have led to an increased interest in developing rapid and inexpensive clinical diagnostic platforms for viral detection. Here, the development of a cell-free toehold switch-based biosensor, which does not require upstream amplification of target RNA, is described for the detection of RNA viruses. Toehold switches were designed to avoid interfering secondary structure in the viral RNA binding region, mutational hotspots, and cross-reacting sequences of other coronaviruses. Using these design criteria, toehold switches were targeted to a low mutation region of the SARS-CoV-2 genome nonstructural protein 2 (nsp2). The designs were tested in a cell-free system using trigger RNA based on the viral genome and a highly sensitive fluorescent reporter gene, mNeonGreen. The detection sensitivity of our best toehold design, CSU 08, was in the low picomolar range of target (trigger) RNA. To increase the sensitivity of our cell-free biosensor to a clinically relevant level, we developed a modular downstream amplification system that utilizes toehold switch activation of tobacco etch virus (TEV) protease expression. The TEV protease cleaves a quenched fluorescent reporter, both increasing the signal fold change between control and sample and increasing the sensitivity to a clinically relevant low femtomolar range for target RNA detection.

From viral democratic genomes to viral wild bunch of quasispecies

The tremendous majority of RNA genomes from pathogenic viruses analyzed and deposited in databases are consensus or "democratic" genomes. They represent the genomes most frequently found in the clinical samples of patients but do not account for the huge genetic diversity of coexisting genomes, which is better described as quasispecies. A viral quasispecies is defined as the dynamic distribution of nonidentical but closely related mutants, variants, recombinant, or reassortant viral genomes. Viral quasispecies have collective behavior and dynamics and are the subject of internal interactions that comprise interference, complementation, or cooperation. In the setting of SARS-CoV-2 infection, intrahost SARS-CoV-2 genetic diversity was recently notably reported for immunocompromised, chronically infected patients, for patients treated with monoclonal antibodies targeting the viral spike protein, and for different body compartments of a single patient. A question that deserves attention is whether such diversity is generated postinfection from a clonal genome in response to selection pressure or is already present at the time of infection as a quasispecies. In the present review, we summarize the data supporting that hosts are infected by a "wild bunch" of viruses rather than by multiple virions sharing the same genome. Each virion in the "wild bunch" may have different virulence and tissue tropisms. As the number of viruses replicated during host infections is huge, a viral quasispecies at any time of infection is wide and is also influenced by host-specific selection pressure after infection, which accounts for the difficulty in deciphering and predicting the appearance of more fit variants and the evolution of epidemics of novel RNA viruses.

Nanopore sequencing technology and its applications

Since the development of Sanger sequencing in 1977, sequencing technology has played a pivotal role in molecular biology research by enabling the interpretation of biological genetic codes. Today, nanopore sequencing is one of the leading third-generation sequencing technologies. With its long reads, portability, and low cost, nanopore sequencing is widely used in various scientific fields including epidemic prevention and control, disease diagnosis, and animal and plant breeding. Despite initial concerns about high error rates, continuous innovation in sequencing platforms and algorithm analysis technology has effectively addressed its accuracy. During the coronavirus disease (COVID-19) pandemic, nanopore sequencing played a critical role in detecting the severe acute respiratory syndrome coronavirus-2 virus genome and containing the pandemic. However, a lack of understanding of this technology may limit its popularization and application. Nanopore sequencing is poised to become the mainstream choice for preventing and controlling COVID-19 and future epidemics while creating value in other fields such as oncology and botany. This work introduces the contributions of nanopore sequencing during the COVID-19 pandemic to promote public understanding and its use in emerging outbreaks worldwide. We discuss its application in microbial detection, cancer genomes, and plant genomes and summarize strategies to improve its accuracy.

The Four Ws of the Fourth Dose COVID-19 Vaccines: Why, Who, When and What

With the emergence of SARS-CoV-2 variants, vaccine breakthrough is a major public health concern. With evidence of reduced neutralizing antibody activity against Omicron variants and fading antibody level after the third-dose booster vaccine, there are suggestions of a fourth-dose booster vaccine. In this review, the benefits of a fourth-dose booster is evaluated from four perspectives, including the effectiveness of the booster dose against virus variants (Why), susceptible groups of individuals who may benefit from additional booster dose (Who), selection of vaccine platforms to better enhance immunity (What) and appropriate intervals between the third and fourth booster dose (When). In summary, a fourth dose can temporarily boost the immune response against SARS-CoV-2 variants and can be considered for specific groups of individuals. A heterologous vaccine strategy using mRNA vaccine in individuals primed with inactivated vaccine may boost immunity against variants. The timing of the fourth dose should be individualized but an interval of 4 months after the third-dose booster is appropriate. A universal fourth booster dose is not necessary.

Host Cell Entry and Neutralization Sensitivity of SARS-CoV-2 Lineages B.1.620 and R.1

The spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) facilitates viral entry into host cells and is the key target for neutralizing antibodies. The SARS-CoV-2 lineage B.1.620 carries fifteen mutations in the S protein and is spread in Africa, the US and Europe, while lineage R.1 harbors four mutations in S and infections were observed in several countries, particularly Japan and the US. However, the impact of the mutations in B.1.620 and R.1 S proteins on antibody-mediated neutralization and host cell entry are largely unknown. Here, we report that these mutations are compatible with robust ACE2 binding and entry into cell lines, and they markedly reduce neutralization by vaccine-induced antibodies. Our results reveal evasion of neutralizing antibodies by B.1.620 and R.1, which might have contributed to the spread of these lineages.

High-Integrity Sequencing of Spike Gene for SARS-CoV-2 Variant Determination

For tiling of the SARS-CoV-2 genome, the ARTIC Network provided a V4 protocol using 99 pairs of primers for amplicon production and is currently the widely used amplicon-based approach. However, this technique has regions of low sequence coverage and is labour-, time-, and cost-intensive. Moreover, it requires 14 pairs of primers in two separate PCRs to obtain spike gene sequences. To overcome these disadvantages, we proposed a single PCR to efficiently detect spike gene mutations. We proposed a bioinformatic protocol that can process FASTQ reads into spike gene consensus sequences to accurately call spike protein variants from sequenced samples or to fairly express the cases of missing amplicons. We evaluated the in silico detection rate of primer sets that yield amplicon sizes of 400, 1200, and 2500 bp for spike gene sequencing of SARS-CoV-2 to be 59.49, 76.19, and 92.20%, respectively. The in silico detection rate of our proposed single PCR primers was 97.07%. We demonstrated the robustness of our analytical protocol against 3000 Oxford Nanopore sequencing runs of distinct datasets, thus ensuring high-integrity sequencing of spike genes for variant SARS-CoV-2 determination. Our protocol works well with the data yielded from versatile primer designs, making it easy to determine spike protein variants.

Limited spread of a rare spike E484K-harboring SARS-CoV-2 in Marseille, France

We detected SARS-CoV-2 of PANGO lineage R.1 with the spike substitution E484K in three patients. Eleven other sequences in France and 8,831 worldwide were available from GISAID, 92% originating from Japan. The three genome sequences from our institute were phylogenetically closest to another from Guinea-Conakry, where one of the patients had travelled. These viruses did not exhibit any unusual features in cell culture. Spike structural predictions indicated a 1.3-time higher transmissibility index than for the globally spread B.1.1.7 variant but also an affinity loss for gangliosides that might have slowed dissemination. The spread of new SARS-CoV-2 mutants/variants is still not well understood and therefore difficult to predict, and this hinders implementation of effective preventive measures, including adapted vaccines.

Antibody Response of BNT162b2 and CoronaVac Platforms in Recovered Individuals Previously Infected by COVID-19 against SARS-CoV-2 Wild Type and Delta Variant

Vaccinating recovered patients previously infected by COVID-19 with mRNA vaccines to boost their immune response against wild-type viruses (WT), we aimed to investigate whether vaccine platform and time of vaccination affect immunogenicity against the SARS-CoV-2 WT and Delta variant (DV). Convalescent patients infected by COVID-19 were recruited and received one booster dose of the BNT162b2 (PC-B) or CoronaVac (PC-C) vaccines, while SARS-CoV-2 naïve subjects received two doses of the BNT162b2 (CN-B) or CoronaVac (CN-C) vaccines. The neutralizing antibody in sera against the WT and DV was determined with live virus neutralization assay (vMN). The vMN geometric mean titre (GMT) against WT in recovered individuals previously infected by COVID-19 reduced significantly from 60.0 (95% confidence interval (CI), 46.5-77.4) to 33.9 (95% CI, 26.3-43.7) at 6 months post recovery. In the PC-B group, the BNT162b2 vaccine enhanced antibody response against WT and DV, with 22.3-fold and 20.4-fold increases, respectively. The PC-C group also showed 1.8-fold and 2.2-fold increases for WT and DV, respectively, after receiving the CoronaVac vaccine. There was a 10.6-fold increase in GMT in the CN-B group and a 1.3-fold increase in the CN-C group against DV after full vaccination. In both the PC-B and PC-C groups, there was no difference between GMT against WT and DV after vaccination. Subjects in the CN-B and CN-C groups showed inferior GMT against DV compared with GMT against WT after vaccination. In this study, one booster shot effectively enhanced the pre-existing neutralizing activity against WT and DV in recovered subjects.

Lessons learned 1 year after SARS-CoV-2 emergence leading to COVID-19 pandemic

Without modern medical management and vaccines, the severity of the Coronavirus Disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) might approach the magnitude of 1894-plague (12 million deaths) and 1918-A(H1N1) influenza (50 million deaths) pandemics. The COVID-19 pandemic was heralded by the 2003 SARS epidemic which led to the discovery of human and civet SARS-CoV-1, bat SARS-related-CoVs, Middle East respiratory syndrome (MERS)-related bat CoV HKU4 and HKU5, and other novel animal coronaviruses. The suspected animal-to-human jumping of 4 betacoronaviruses including the human coronaviruses OC43(1890), SARS-CoV-1(2003), MERS-CoV(2012), and SARS-CoV-2(2019) indicates their significant pandemic potential. The presence of a large reservoir of coronaviruses in bats and other wild mammals, culture of mixing and selling them in urban markets with suboptimal hygiene, habit of eating exotic mammals in highly populated areas, and the rapid and frequent air travels from these areas are perfect ingredients for brewing rapidly exploding epidemics. The possibility of emergence of a hypothetical SARS-CoV-3 or other novel viruses from animals or laboratories, and therefore needs for global preparedness should not be ignored. We reviewed representative publications on the epidemiology, virology, clinical manifestations, pathology, laboratory diagnostics, treatment, vaccination, and infection control of COVID-19 as of 20 January 2021, which is 1 year after person-to-person transmission of SARS-CoV-2 was announced. The difficulties of mass testing, labour-intensive contact tracing, importance of compliance to universal masking, low efficacy of antiviral treatment for severe disease, possibilities of vaccine or antiviral-resistant virus variants and SARS-CoV-2 becoming another common cold coronavirus are discussed.

A Global Mutational Profile of SARS-CoV-2: A Systematic Review and Meta-Analysis of 368,316 COVID-19 Patients

Since its first detection in December 2019, more than 232 million cases of COVID-19, including 4.7 million deaths, have been reported by the WHO. The SARS-CoV-2 viral genomes have evolved rapidly worldwide, causing the emergence of new variants. This systematic review and meta-analysis was conducted to provide a global mutational profile of SARS-CoV-2 from December 2019 to October 2020. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA), and a study protocol was lodged with PROSPERO. Data from 62 eligible studies involving 368,316 SARS-CoV-2 genomes were analyzed. The mutational data analyzed showed most studies detected mutations in the Spike protein (n = 50), Nucleocapsid phosphoprotein (n = 34), ORF1ab gene (n = 29), 5′-UTR (n = 28) and ORF3a (n = 25). Under the random-effects model, pooled prevalence of SARS-CoV-2 variants was estimated at 95.1% (95% CI; 93.3–96.4%; I² = 98.952%; p = 0.000) while subgroup meta-analysis by country showed majority of the studies were conducted ‘Worldwide’ (n = 10), followed by ‘Multiple countries’ (n = 6) and the USA (n = 5). The estimated prevalence indicated a need to continuously monitor the prevalence of new mutations due to their potential influence on disease severity, transmissibility and vaccine effectiveness.

Mutational Hotspot in the SARS-CoV-2 Spike Protein N-Terminal Domain Conferring Immune Escape Potential

Global efforts are being made to monitor the evolution of SARS-CoV-2, aiming for early identification of genotypes providing increased infectivity or virulence. However, viral lineage-focused tracking might fail in early detection of advantageous mutations emerging independently across phylogenies. Here, the emergence patterns of Spike mutations were investigated in sequences deposited in local and global databases to identify mutational hotspots across phylogenies and we evaluated their impact on SARS-CoV-2 evolution. We found a striking increase in the frequency of recruitment of diverse substitutions at a critical residue (W152), positioned in the N-terminal domain (NTD) of the Spike protein, observed repeatedly across independent phylogenetic and geographical contexts. These mutations might have an impact on the evasion of neutralizing antibodies. Finally, we found that NTD is a region exhibiting particularly high frequency of mutation recruitments, suggesting an evolutionary path in which the virus maintains optimal efficiency of ACE2 binding combined with the flexibility facilitating the immune escape. We conclude that adaptive mutations, frequently present outside of the receptor-binding domain, can emerge in virtually any SARS-CoV-2 lineage and at any geographical location. Therefore, surveillance should not be restricted to monitoring defined lineages alone.

False COVID-19 cases due to contamination by inactivated virus vaccine

A false-positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse-transcription polymerase chain reaction result can lead to unnecessary public health measures. We report 2 individuals whose respiratory specimens were contaminated by an inactivated SARS-CoV-2 vaccine strain (CoronaVac), likely at vaccination premises. Incidentally, whole genome sequencing of CoronaVac showed adaptive deletions on the spike protein, which do not result in observable changes of antigenicity.

One-Year Update on Salivary Diagnostic of COVID-19

Background: Coronavirus disease 2019 (COVID-19) is a global health problem, which is challenging healthcare worldwide. In this critical review, we discussed the advantages and limitations in the implementation of salivary diagnostic platforms of COVID-19. The diagnostic test of COVID-19 by invasive nasopharyngeal collection is uncomfortable for patients and requires specialized training of healthcare professionals in order to obtain an appropriate collection of samples. Additionally, these professionals are in close contact with infected patients or suspected cases of COVID-19, leading to an increased contamination risk for frontline healthcare workers. Although there is a colossal demand for novel diagnostic platforms with non-invasive and self-collection samples of COVID-19, the implementation of the salivary platforms has not been implemented for extensive scale testing. Up to date, several cross-section and clinical trial studies published in the last 12 months support the potential of detecting SARS-CoV-2 RNA in saliva as a biomarker for COVID-19, providing a self-collection, non-invasive, safe, and comfortable procedure. Therefore, the salivary diagnosis is suitable to protect healthcare professionals and other frontline workers and may encourage patients to get tested due to its advantages over the current invasive methods. The detection of SARS-CoV-2 in saliva was substantial also in patients with a negative nasopharyngeal swab, indicating the presence of false negative results. Furthermore, we expect that salivary diagnostic devices for COVID-19 will continue to be used with austerity without excluding traditional gold standard specimens to detect SARS-CoV-2.

COVID-19 Outbreak Associated with a SARS-CoV-2 R.1 Lineage Variant in a Skilled Nursing Facility After Vaccination Program - Kentucky, March 2021

Although COVID-19 mRNA vaccines demonstrated high efficacy in clinical trials (1), they were not 100% efficacious. Thus, some infections postvaccination are expected. Limited data are available on effectiveness in skilled nursing facilities (SNFs) and against emerging variants. The Kentucky Department for Public Health (KDPH) and a local health department investigated a COVID-19 outbreak in a SNF that occurred after all residents and health care personnel (HCP) had been offered vaccination. Among 83 residents and 116 HCP, 75 (90.4%) and 61 (52.6%), respectively, received 2 vaccine doses. Twenty-six residents and 20 HCP received positive test results for SARS-CoV-2, the virus that causes COVID-19, including 18 residents and four HCP who had received their second vaccine dose >14 days before the outbreak began. An R.1 lineage variant was detected with whole genome sequencing (WGS). Although the R.1 variant has multiple spike protein mutations, vaccinated residents and HCP were 87% less likely to have symptomatic COVID-19 compared with those who were unvaccinated. Vaccination of SNF populations, including HCP, is critical to reduce the risk for SARS-CoV-2 introduction, transmission, and severe outcomes in SNFs. An ongoing focus on infection prevention and control practices is also essential.