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Tag: immunity
February 17, 2021
CD8+ T Cell Responses in COVID-19 Convalescent Individuals Target Conserved Epitopes from Multiple Prominent SARS-CoV-2 Circulating Variants
[Pre-print, not peer-reviewed] A study assessing whether CD8+ T-cells from COVID-19 convalescent individuals (n=30) can recognize SARS-CoV-2 variant epitopes showed that only one of the three most prominent variants (the B.1.351 variant, first described in South Africa) had a mutation that overlapped with a low-prevalence CD8+ epitope. Out of 45 mutations assessed, this mutation was…
SARS-CoV-2 Variants Show Resistance to Neutralization by Many Monoclonal and Serum-Derived Polyclonal Antibodies
[Pre-print, not peer-reviewed] Most convalescent sera from people who had recovered from COVID-19 and virtually all Pfizer-BioNTech mRNA vaccine-induced immune sera were shown to have diminished neutralizing activity against engineered SARS-CoV-2 strains including a chimeric strain combining a strain identified in Washington state with a B.1.351 spike gene (Wash SA-B.1.351 strain), or recombinant viruses containing…
February 16, 2021
Persistence of SARS-CoV-2 Specific B- and T-Cell Responses in Convalescent COVID-19 Patients 6-8 Months after the Infection
Anti-SARS-CoV-2 antibodies were detected in 85% of 119 samples collected from 88 COVID-19 convalescent donors within 4 weeks post symptom onset. IgM/IgA levels declined after 1 month, while IgG levels remained relatively stable and were detected in 80% of samples up to 6-8 months irrespective of disease severity. SARS-CoV-2-specific memory B- and T-cell responses developed…
Longitudinal Analysis of Antibody Response Following SARS-CoV-2 Infection in Pregnancy: From the First Trimester to Delivery
In a cohort of 17 SARS-CoV-2 PCR-positive pregnant women followed from the end of the first trimester to delivery, IgG non-neutralizing antibodies (nNAbs) were detected in 71% (12 of 17), while neutralizing antibodies (NAbs) were detected in 53% of individuals (9 of the 12 who seroconverted with IgG nNAbs). Levels of NAbs remained stable throughout…
Discrete SARS-CoV-2 Antibody Titers Track with Functional Humoral Stability
There may be a distinct threshold of immune activity, defined by the level of antibodies, in response to SARS-CoV-2 infection that is required to elicit a vigorous humoral and cellular response necessary to prevent subsequent re-infection. These conclusions were based on a community-based surveillance study of 120 SARS-CoV-2 convalescent patients, which found that sustained functional…
S-Variant SARS-CoV-2 Lineage B1.1.7 Is Associated with Significantly Higher Viral Loads in Samples Tested by ThermoFisher TaqPath RT-QPCR
Individuals infected with the SARS-CoV-2 B.1.1.7 variant (first described in the UK) may have considerably higher viral loads, which could potentially explain the higher transmissibility of this variant. Analysis of 641 SARS-CoV-2 PCR positive samples in the UK from October to November 2020 showed that samples suspected to have the B.1.1.7 variant, identified by a…
February 11, 2021
Lasting Antibody and T Cell Responses to SARS-CoV-2 in COVID-19 Patients Three Months after Infection
In a longitudinal study of 25 convalescent SARS-CoV-2 positive patients, approximately 65% of patients had detectable T cell responses 3-4 months post-symptom onset (PSO) despite all patients seroconverting. All patients had detectable IgG against the nucleocapsid (N) and spike (S) protein as well as detectable IgG and IgM responses against the receptor-binding domain (RBD); all…
Impact of COVID-19 Vaccination Program on Healthcare Worker Infections in an Academic Hospital
An academic hospital in Virginia reported a 25% decrease in health care worker (HCW) SARS-CoV-2 infections 6 days after beginning employee immunizations. Vaccines included both the Pfizer vaccine initiated on December 12, 2020 and the Moderna vaccine initiated on December 28, 2020. After achieving 60% vaccination coverage of the 1st dose, infections decreased by 50%….
SARS-CoV-2 Antibody Prevalence in England Following the First Peak of the Pandemic
A large serosurvey in England (REACT-2 Study) estimated the nationwide seroprevalence of SARS-CoV-2 to be 6%, corresponding to an estimated 3.4 million people with prior infection. Seroprevalence was determined from a representative cohort of over 100,000 adults (>18 years old). Prevalence was 2- to 3-fold higher among healthcare workers compared with non-essential workers, and higher…
Citywide Serosurveillance of the Initial SARS-CoV-2 Outbreak in San Francisco
[Pre-print, not peer reviewed] SARS-CoV-2 serosurveillance using remnant samples from routine blood draws in two major hospital networks in San Francisco estimated a seroprevalence of 4.2% in the period between March and June 2020. Seroprevalence was higher among those who were uninsured; individuals identifying as Hispanic, Black, or African; males; and individuals who experience homelessness….
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