Your browser doesn't support javascript.
Show: 20 | 50 | 100
Results 1 - 11 de 11
Filter
2.
Nat Immunol ; 22(5): 620-626, 2021 05.
Article in English | MEDLINE | ID: covidwho-1387432

ABSTRACT

The immune response to SARS-CoV-2 is critical in controlling disease, but there is concern that waning immunity may predispose to reinfection. We analyzed the magnitude and phenotype of the SARS-CoV-2-specific T cell response in 100 donors at 6 months following infection. T cell responses were present by ELISPOT and/or intracellular cytokine staining analysis in all donors and characterized by predominant CD4+ T cell responses with strong interleukin (IL)-2 cytokine expression. Median T cell responses were 50% higher in donors who had experienced a symptomatic infection, indicating that the severity of primary infection establishes a 'set point' for cellular immunity. T cell responses to spike and nucleoprotein/membrane proteins were correlated with peak antibody levels. Furthermore, higher levels of nucleoprotein-specific T cells were associated with preservation of nucleoprotein-specific antibody level although no such correlation was observed in relation to spike-specific responses. In conclusion, our data are reassuring that functional SARS-CoV-2-specific T cell responses are retained at 6 months following infection.


Subject(s)
Antigens, Viral/immunology , CD4-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/immunology , COVID-19/immunology , Immunity, Cellular , SARS-CoV-2/immunology , Adult , Aged , Antibodies, Viral/blood , CD4-Positive T-Lymphocytes/metabolism , CD4-Positive T-Lymphocytes/virology , CD8-Positive T-Lymphocytes/metabolism , CD8-Positive T-Lymphocytes/virology , COVID-19/blood , COVID-19/virology , Female , Host-Pathogen Interactions , Humans , Interleukin-2/blood , Male , Middle Aged , Phenotype , SARS-CoV-2/pathogenicity , Time Factors , Young Adult
3.
International Review of Financial Analysis ; 77:101820, 2021.
Article in English | ScienceDirect | ID: covidwho-1293870

ABSTRACT

We show that during the weeks following the initiation of the COVID-19 pandemic, the United States equity market was inefficient. This is demonstrated by showing that utility maximizing agents over the time period ranging from mid-February to late March 2020 can generate statistically significant profits by utilizing only historical price and virus related data to forecast future equity ETF returns. We generalize Merton’s optimal portfolio problem using a novel method based upon a likelihood ratio in order to construct a dynamic trading strategy for utility maximizing agents. These strategies are shown to have statistically significant profitability and strong risk and performance statistics during the COVID-19 time-frame.

4.
Mar Policy ; 132: 104646, 2021 Oct.
Article in English | MEDLINE | ID: covidwho-1272613

ABSTRACT

The COVID-19 global pandemic and subsequent implementation of measures to reduce contact within the community have affected fisheries worldwide, yet few studies have reported the impacts on recreational fisheries. This study investigates boat-based recreational fishing in Western Australia from March to August 2020, where COVID-19 measures relevant to recreational fishers included various travel restrictions, and social and physical distancing measures. Information from surveys of licensed recreational fishers and fisheries compliance officers, and camera footage from key boat ramps is presented. A lower proportion of Perth metropolitan fishers went fishing compared with regional fishers. Metropolitan fishers also reported fewer days fished and lower participation in demersal and shore-based line fishing than regional fishers. In contrast, compliance officers observed more fishing activity in both metropolitan and regional locations. Fishing plans were mostly affected by travel restrictions with more metropolitan fishers affected compared with regional fishers. Daily recreational vessel retrievals at key boat ramps varied between locations, with metropolitan fishers initially unable to travel to regional centres. There was no decline in vessel retrievals at metropolitan boat ramps during the most rigid restrictions and northern regional boat ramps experienced substantial increases in recreational vessel activity once travel restrictions eased. Studies of this kind highlight the value of utilising established recreational fishing monitoring programmes to provide a responsive and scientific basis for policymakers to address societal behavioural changes associated with atypical events such as COVID-19.

6.
Sex Transm Infect ; 97(3): 209-214, 2021 05.
Article in English | MEDLINE | ID: covidwho-1189914

ABSTRACT

OBJECTIVES: We comparatively evaluated two HIV and syphilis blood sampling kits (dried blood spot (DBS) and mini tube (MT)) as part of an online STI postal sampling service that included tests for chlamydia and gonorrhoea. We aimed to see how the blood collection systems compared regarding sample return rates and result rates. Additionally, we aimed to observe differences in false-positive results and describe a request-to-result ratio (RRR)-the required number of kit requests needed to obtain one successful result. METHODS: We reviewed data from an online postal STI kit requesting service for a client transitioning from MT to DBS blood collection systems. We described service user baseline characteristics and compared kit requests, kit and blood sample return rates, and the successful resulting rates for HIV and syphilis for MT and DBS. Pearson's χ2 and Fisher's exact test were used to determine statistical differences, and statistical formulae were applied to produce CIs for differences in proportions. RESULTS: 5670 STI postal kit requests from a Midlands region were reviewed from 6 September 2016-2 January 2019 (1515 MT and 4155 DBS). Baseline characteristics between the two groups were comparable (68.0% female, 74.0% white British and 87.5% heterosexual, median age 26 years). Successful processing rates for DBS were 94.6% and 54.4% for MT (p<0.001) with a percentage difference of 40.2% (95% CI 36.9% to 43.4%). The RRR for MT was 2.9 cf. 1.6 for DBS. False-positive results for MT samples were 5.2% (HIV) and 0.4% (syphilis), and those for DBS were 0.4% (HIV) and 0.0% (syphilis). CONCLUSIONS: This comparative analysis demonstrated the superior successful processing rates for postal DBS collection systems compared with MT. Reasons for this included insufficient volumes, high false-positive rates and degradation of blood quality in MT samples. A postal sampling service using DBS to screen for HIV, syphilis and other blood-borne viruses could be a viable alternative.

7.
EBioMedicine ; 65: 103259, 2021 Mar.
Article in English | MEDLINE | ID: covidwho-1116568

ABSTRACT

BACKGROUND: SARS-CoV-2 serology is used to identify prior infection at individual and at population level. Extended longitudinal studies with multi-timepoint sampling to evaluate dynamic changes in antibody levels are required to identify the time horizon in which these applications of serology are valid, and to explore the longevity of protective humoral immunity. METHODS: Healthcare workers were recruited to a prospective cohort study from the first SARS-CoV-2 epidemic peak in London, undergoing weekly symptom screen, viral PCR and blood sampling over 16-21 weeks. Serological analysis (n =12,990) was performed using semi-quantitative Euroimmun IgG to viral spike S1 domain and Roche total antibody to viral nucleocapsid protein (NP) assays. Comparisons were made to pseudovirus neutralizing antibody measurements. FINDINGS: A total of 157/729 (21.5%) participants developed positive SARS-CoV-2 serology by one or other assay, of whom 31.0% were asymptomatic and there were no deaths. Peak Euroimmun anti-S1 and Roche anti-NP measurements correlated (r = 0.57, p<0.0001) but only anti-S1 measurements correlated with near-contemporary pseudovirus neutralising antibody titres (measured at 16-18 weeks, r = 0.57, p<0.0001). By 21 weeks' follow-up, 31/143 (21.7%) anti-S1 and 6/150 (4.0%) anti-NP measurements reverted to negative. Mathematical modelling revealed faster clearance of anti-S1 compared to anti-NP (median half-life of 2.5 weeks versus 4.0 weeks), earlier transition to lower levels of antibody production (median of 8 versus 13 weeks), and greater reductions in relative antibody production rate after the transition (median of 35% versus 50%). INTERPRETATION: Mild SARS-CoV-2 infection is associated with heterogeneous serological responses in Euroimmun anti-S1 and Roche anti-NP assays. Anti-S1 responses showed faster rates of clearance, more rapid transition from high to low level production rate and greater reduction in production rate after this transition. In mild infection, anti-S1 serology alone may underestimate incident infections. The mechanisms that underpin faster clearance and lower rates of sustained anti-S1 production may impact on the longevity of humoral immunity. FUNDING: Charitable donations via Barts Charity, Wellcome Trust, NIHR.


Subject(s)
Antibodies, Neutralizing/blood , Antibodies, Viral/blood , COVID-19/blood , Coronavirus Nucleocapsid Proteins/immunology , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/immunology , Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , COVID-19/diagnosis , Health Personnel/statistics & numerical data , Humans , Immunoglobulin A/blood , Immunoglobulin G/blood , Phosphoproteins/immunology , Protein Domains/immunology
8.
Nat Med ; 27(2): 279-288, 2021 02.
Article in English | MEDLINE | ID: covidwho-1065913

ABSTRACT

More than 190 vaccines are currently in development to prevent infection by the novel severe acute respiratory syndrome coronavirus 2. Animal studies suggest that while neutralizing antibodies against the viral spike protein may correlate with protection, additional antibody functions may also be important in preventing infection. Previously, we reported early immunogenicity and safety outcomes of a viral vector coronavirus vaccine, ChAdOx1 nCoV-19 (AZD1222), in a single-blinded phase 1/2 randomized controlled trial of healthy adults aged 18-55 years ( NCT04324606 ). Now we describe safety and exploratory humoral and cellular immunogenicity of the vaccine, from subgroups of volunteers in that trial, who were subsequently allocated to receive a homologous full-dose (SD/SD D56; n = 20) or half-dose (SD/LD D56; n = 32) ChAdOx1 booster vaccine 56 d following prime vaccination. Previously reported immunogenicity data from the open-label 28-d interval prime-boost group (SD/SD D28; n = 10) are also presented to facilitate comparison. Additionally, we describe volunteers boosted with the comparator vaccine (MenACWY; n = 10). In this interim report, we demonstrate that a booster dose of ChAdOx1 nCoV-19 is safe and better tolerated than priming doses. Using a systems serology approach we also demonstrate that anti-spike neutralizing antibody titers, as well as Fc-mediated functional antibody responses, including antibody-dependent neutrophil/monocyte phagocytosis, complement activation and natural killer cell activation, are substantially enhanced by a booster dose of vaccine. A booster dose of vaccine induced stronger antibody responses than a dose-sparing half-dose boost, although the magnitude of T cell responses did not increase with either boost dose. These data support the two-dose vaccine regime that is now being evaluated in phase 3 clinical trials.


Subject(s)
Antibody Formation/immunology , COVID-19 Vaccines/immunology , COVID-19/immunology , Immunization, Secondary , SARS-CoV-2/immunology , Adolescent , Adult , Antibodies, Neutralizing/immunology , Dose-Response Relationship, Drug , Genetic Vectors/immunology , Humans , Middle Aged , Spike Glycoprotein, Coronavirus/immunology , Time Factors , Young Adult
10.
Sci Immunol ; 5(54)2020 12 23.
Article in English | MEDLINE | ID: covidwho-999191

ABSTRACT

Understanding the nature of immunity following mild/asymptomatic infection with SARS-CoV-2 is crucial to controlling the pandemic. We analyzed T cell and neutralizing antibody responses in 136 healthcare workers (HCW) 16-18 weeks after United Kingdom lockdown, 76 of whom had mild/asymptomatic SARS-CoV-2 infection captured by serial sampling. Neutralizing antibodies (nAb) were present in 89% of previously infected HCW. T cell responses tended to be lower following asymptomatic infection than in those reporting case-definition symptoms of COVID-19, while nAb titers were maintained irrespective of symptoms. T cell and antibody responses were sometimes discordant. Eleven percent lacked nAb and had undetectable T cell responses to spike protein but had T cells reactive with other SARS-CoV-2 antigens. Our findings suggest that the majority of individuals with mild or asymptomatic SARS-CoV-2 infection carry nAb complemented by multispecific T cell responses at 16-18 weeks after mild or asymptomatic SARS-CoV-2 infection.


Subject(s)
Antibodies, Neutralizing/immunology , Asymptomatic Infections , COVID-19/immunology , T-Lymphocytes/immunology , Antibodies, Neutralizing/blood , Antibodies, Viral/blood , Antibodies, Viral/immunology , Case-Control Studies , Cross-Sectional Studies , Humans , SARS-CoV-2/immunology
11.
Emerg Infect Dis ; 26(12): 2970-2973, 2020 12.
Article in English | MEDLINE | ID: covidwho-792953

ABSTRACT

Dried blood spot (DBS) samples can be used for the detection of severe acute respiratory syndrome coronavirus 2 spike antibodies. DBS sampling is comparable to matched serum samples with a relative 98.1% sensitivity and 100% specificity. Thus, DBS sampling offers an alternative for population-wide serologic testing in the coronavirus pandemic.


Subject(s)
COVID-19/diagnosis , Dried Blood Spot Testing/methods , Antibodies, Viral/immunology , COVID-19 Serological Testing/methods , Case-Control Studies , Dried Blood Spot Testing/economics , Humans , Predictive Value of Tests , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/immunology , Spike Glycoprotein, Coronavirus/isolation & purification
SELECTION OF CITATIONS
SEARCH DETAIL
...