ORCID Profile
0000-0001-6522-138X
Current Organisation
University of Oxford
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Publisher: American Society for Microbiology
Date: 20-04-2022
DOI: 10.1128/JCM.02283-21
Abstract: Tools to detect SARS-CoV-2 variants of concern and track the ongoing evolution of the virus are necessary to support public health efforts and the design and evaluation of novel COVID-19 therapeutics and vaccines. Although next-generation sequencing (NGS) has been adopted as the gold standard method for discriminating SARS-CoV-2 lineages, alternative methods may be required when processing s les with low viral loads or low RNA quality.
Publisher: Oxford University Press (OUP)
Date: 24-05-2021
Abstract: Convalescent plasma containing neutralizing antibody to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is under investigation for coronavirus disease 2019 (COVID-19) treatment. We report erse virological characteristics of UK intensive care patients enrolled in the Immunoglobulin Domain of the REMAP-CAP randomized controlled trial that potentially influence treatment outcomes. SARS-CoV-2 RNA in nasopharyngeal swabs collected pretreatment was quantified by PCR. Antibody status was determined by spike-protein ELISA. B.1.1.7 was differentiated from other SARS-CoV-2 strains using allele-specific probes or restriction site polymorphism (SfcI) targeting D1118H. Of 1274 subjects, 90% were PCR positive with viral loads 118–1.7 × 1011IU/mL. Median viral loads were 40-fold higher in those IgG seronegative (n = 354 28%) compared to seropositives (n = 939 72%). Frequencies of B.1.1.7 increased from & % in November 2020 to 82% of subjects in January 2021. Seronegative in iduals with wild-type SARS-CoV-2 had significantly higher viral loads than seropositives (medians 5.8 × 106 and 2.0 × 105 IU/mL, respectively P = 2 × 10−15). High viral loads in seropositive B.1.1.7-infected subjects and resistance to seroconversion indicate less effective clearance by innate and adaptive immune responses. SARS-CoV-2 strain, viral loads, and antibody status define subgroups for analysis of treatment efficacy.
Publisher: Cold Spring Harbor Laboratory
Date: 05-03-2021
DOI: 10.1101/2021.02.24.21251989
Abstract: Treatment of COVID-19 patients with convalescent plasma containing neutralising antibody to SARS-CoV-2 is under investigation as a means of reducing viral loads, ameliorating disease outcomes, and reducing mortality. However, its efficacy might be reduced in those infected with the emerging B.1.1.7 SARS-CoV-2 variant. Here, we report the erse virological characteristics of UK patients enrolled in the Immunoglobulin Domain of the REMAP-CAP randomised controlled trial. SARS-CoV-2 viral RNA was detected and quantified by real-time PCR in nasopharyngeal swabs obtained from study subjects within 48 hours of admission to intensive care unit. Antibody status was determined by spike-protein ELISA. B.1.1.7 strain was differentiated from other SARS-CoV-2 strains by two novel typing methods detecting the B.1.1.7-associated D1118H mutation with allele-specific probes and by restriction site polymorphism (SfcI). Of 1260 subjects, 90% were PCR-positive with viral loads in nasopharyngeal swabs ranging from 72 international units [IUs]/ml to 1.7×10 11 IU/ml. Median viral loads were 45-fold higher in those who were seronegative for IgG antibodies (n=314 28%) compared to seropositives (n=804 72%), reflecting in part the latter group’s possible later disease stage on enrolment. Frequencies of B.1.1.7 infection increased from early November ( %) to December 2020 ( %). Anti-SARS-CoV-2 seronegative in iduals infected with wild-type SARS-CoV-2 had significantly higher viral loads than seropositives (medians of 1.2×10 6 and 3.4 ×10 4 IU/ml respectively p=2×10 −9 ). However, viral load distributions were elevated in both seropositive and seronegative subjects infected with B.1.1.7 (13.4×10 6 and 7.6×10 6 IU/ml p=0.18). High viral loads in seropositive B.1.1.7-infected subjects are consistent with increased replication capacity and/or less effective clearance by innate or adaptive immune response of B.1.1.7 strain than wild-type. As viral genotype was associated with erse virological and immunological phenotypes, metrics of viral load, antibody status and infecting strain should be used to define subgroups for analysis of treatment efficacy.
Publisher: Springer Science and Business Media LLC
Date: 06-10-2021
DOI: 10.1038/S41467-021-25982-W
Abstract: Several COVID-19 vaccines have shown good efficacy in clinical trials, but there remains uncertainty about the efficacy of vaccines against different variants. Here, we investigate the efficacy of ChAdOx1 nCoV-19 (AZD1222) against symptomatic COVID-19 in a post-hoc exploratory analysis of a Phase 3 randomised trial in Brazil (trial registration ISRCTN89951424). Nose and throat swabs were tested by PCR in symptomatic participants. Sequencing and genotyping of swabs were performed to determine the lineages of SARS-CoV-2 circulating during the study. Protection against any symptomatic COVID-19 caused by the Zeta (P.2) variant was assessed in 153 cases with vaccine efficacy (VE) of 69% (95% CI 55, 78). 49 cases of B.1.1.28 occurred and VE was 73% (46, 86). The Gamma (P.1) variant arose later in the trial and fewer cases ( N = 18) were available for analysis. VE was 64% (−2, 87). ChAdOx1 nCoV-19 provided 95% protection (95% CI 61%, 99%) against hospitalisation due to COVID-19. In summary, we report that ChAdOx1 nCoV-19 protects against emerging variants in Brazil despite the presence of the spike protein mutation E484K.
Publisher: Research Square Platform LLC
Date: 12-07-2021
DOI: 10.21203/RS.3.RS-654257/V1
Abstract: Background Emerging evidence shows the substantial real-world impact of authorised vaccines against COVID-19 and provides insight into the potential role of vaccines in curbing the pandemic. However, there remains uncertainty about the efficacy of vaccines against different variants of the virus. Here we assessed efficacy of ChAdOx1 nCoV-19 (AZD1222) against lineages of SARS-CoV-2 circulating in Brazil from June 2020 until early 2021. Methods Participants aged 18 and above were enrolled into a randomised phase 3 trial of ChAdOx1 nCoV-19 vaccine against symptomatic SARS-CoV-2 infection. Participants received two doses of ChAdOx1 nCoV-19 or control (1st dose: Men ACWY vaccine, 2nd dose: normal saline). Nasopharyngeal and oropharyngeal swabbing was performed if participants developed symptoms of COVID-19 (cough, shortness of breath, fever .8°C, ageusia, anosmia). Swabs were tested by nucleic acid lification (NAAT) for SARS-CoV-2, sequenced, and viral load determined. For those s les where a genotype could not be ascertained from sequencing, allele specific PCR was performed. The efficacy analysis included symptomatic COVID-19 in seronegative participants with a NAAT positive swab more than 14 days after a second dose of vaccine. Participants were unblinded after the vaccine was authorised for use, and the control participants offered vaccination. Infections occurring after unblinding were excluded from analysis. Vaccine efficacy was calculated as 100% x (1 – relative risk (RR)), where RR was estimated from a robust Poisson model. The trial is registered at ISRCTN89951424. Findings 9433 participants were eligible for inclusion in the pre-specified primary efficacy population, having reached more than 14 days after a second dose of ChAdOx1 nCoV-19, of whom 307 were NAAT+, in this post-hoc analysis. From June 2020 to February 2021, the two most frequently identified lineages were P.2 (N=153) and B.1.1.28 (N=49). P.1 emerged during the study (N=18) but became dominant only after study unblinding. Viral loads were highest amongst those with P.1 infection. Vaccine efficacy (VE) for B.1.1.33 (88.2%, 95%CI 5, 99), B.1.1.28 (73%, 95% CI, 46, 86), P.2 (69% 95% CI, 55, 78) and P.1 (64%, 95% CI, -2, 87) was estimated. In participants who had received two doses of vaccine, one COVID-19 hospitalisation occurred in the ChAdOx1 nCoV-19 group and 18 in the control group, with VE against hospitalisation 95% (95% CI 61, 99). There were 2 COVID-19 deaths in the control group and none in the vaccine group. Interpretation ChAdOx1 nCoV-19 provides high efficacy against hospitalisation, severe disease and death from COVID-19 in Brazil and there is strong evidence of protection being maintained against P.2, despite the presence of the spike protein mutation E484K. Real world effectiveness studies are ongoing in Brazil to further establish protection against P.1 and other emerging variants.
Publisher: Cold Spring Harbor Laboratory
Date: 02-11-2021
DOI: 10.1101/2021.11.01.21265384
Abstract: Tools to detect SARS-Coronavirus-2 variants of concern and track the ongoing evolution of the virus are necessary to support public health efforts and the design and evaluation of novel COVID-19 therapeutics and vaccines. Although next-generation sequencing (NGS) has been adopted as the gold standard method for discriminating SARS-CoV-2 lineages, alternative methods may be required when processing s les with low viral loads or low RNA quality. An allele-specific probe polymerase chain reaction (ASP-PCR) targeting lineage-specific single nucleotide polymorphisms (SNPs) was developed and used to screen 1,082 s les from two clinical trials in the United Kingdom and Brazil. Probit regression models were developed to compare ASP-PCR performance against 1,771 NGS results for the same cohorts. In idual SNPs were shown to readily identify specific variants of concern. ASP-PCR was shown to discriminate SARS-CoV-2 lineages with a higher likelihood than NGS over a wide range of viral loads. Comparative advantage for ASP-PCR over NGS was most pronounced in s les with Ct values between 26-30 and in s les that showed evidence of degradation. Results for s les screened by ASP-PCR and NGS showed 99% concordant results. ASP-PCR is well-suited to augment but not replace NGS. The method can differentiate SARS-COV-2 lineages with high accuracy and would be best deployed to screen s les with lower viral loads or that may suffer from degradation. Future work should investigate further destabilization from primer:target base mismatch through altered oligonucleotide chemistry or chemical additives.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Jeremy Ratcliff.