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Tag: immunity
March 9, 2021
Serological Evidence of Human Infection with SARS-CoV-2: A Systematic Review and Meta-Analysis
Seroprevalence of SARS-CoV-2-specific antibodies varied dramatically across WHO regions, according to a systematic review and meta-analysis including over 5 million participants from 400 serosurveys. The Southeast Asia region had the highest seroprevalence (20%), while the Western Pacific region, including Australia and New Zealand, had the lowest (1.7%). In a subset of serosurveys with higher quality…
March 8, 2021
Robust SARS-CoV-2-Specific T Cell Immunity Is Maintained at 6 Months Following Primary Infection
Functional SARS-CoV-2-specific T cell responses were retained 6 months after initial SARS-CoV-2 infection among 100 convalescent donors between March and April 2020. Interferon (IFN)-γ ELISPOT analysis was used to determine the magnitude of the T cell response. Cell responses were present among all donors and characterized by predominant CD4+ T cell responses with strong interleukin…
Comparison of IgG and Neutralizing Antibody Responses after One or Two Doses of COVID-19 MRNA Vaccine in Previously Infected and Uninfected Persons
[Pre-print, not peer-reviewed] A community-based, home-collected, longitudinal serosurvey of 290 participants before and after vaccination with either the Moderna or Pfizer/BioNTech vaccines found that a prior outpatient COVID-19 diagnosis was associated with strong anti-spike RBD IgG and in vitro neutralizing responses after one vaccine dose. Median IgG concentration and percent neutralization after one dose were…
March 5, 2021
SARS-CoV-2 Variant with Higher Affinity to ACE2 Shows Reduced Sera Neutralization Susceptibility
[Pre-print, not peer-reviewed] An in vitro study of newly-emerging SARS-CoV-2 mutations in the receptor binding domain (RBD) of the viral spike protein found in the P.1 variant (first described in Brazil) demonstrated increased angiotensin-converting enzyme 2 (ACE2) affinity for the mutant RBD and reduced neutralization ability of immune sera induced from prior strains. RBD mutations…
Time Series Analysis and Mechanistic Modelling of Heterogeneity and Sero-Reversion in Antibody Responses to Mild SARS-CoV-2 Infection
A prospective serology cohort study among UK healthcare workers found that by 21 weeks, 22% (31 of 143) of those previously positive for anti-SARS-CoV-2 spike (S1) antibodies reverted to being S1 negative, while only 4% (6 of 150) of those previously positive for anti-SARS-CoV-2 nucleocapsid (NP) antibodies reverted to being NP negative, which the authors…
Resistance of SARS-CoV-2 Variants to Neutralization by Monoclonal and Serum-Derived Polyclonal Antibodies
Most convalescent sera from people who had recovered from mild COVID-19 (n=29) and virtually all Pfizer-BioNTech mRNA vaccine-induced immune sera (n=24) 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…
March 3, 2021
Increased Resistance of SARS-CoV-2 Variant P.1 to Antibody Neutralization
[Pre-print, not peer-reviewed] Reduced neutralization titers against the P.1 SARS-CoV-2 variant were found in both convalescent plasma (6.5-fold) and plasma from individuals who received an mRNA vaccine (2.2-2.8-fold). The P.1 variant completely resisted neutralization by multiple neutralizing monoclonal antibodies. Using a VSV-based SARS-CoV-2 pseudovirus with all 10 mutations of the P.1 variant, the authors note…
March 2, 2021
Long-Term SARS-CoV-2-Specific Immune and Inflammatory Responses Across a Clinically Diverse Cohort of Individuals Recovering from COVID-19
[Pre-print, not peer-reviewed] A longitudinal study in California found that SARS-CoV-2-specific T cell responses remained largely stable up to 9 months following SARS-CoV-2 infection (n=70). Stronger CD4+ T cell responses were associated with initial disease severity as well as neutralizing antibody levels, whereas pre-existing lung disease predicted long-term CD8+ T cell responses. While 36% of…
Reduced Antibody Cross-Reactivity Following Infection with B.1.1.7 than with Parental SARS-CoV-2 Strains
[Pre-print, not peer-reviewed] Convalescent sera from patients infected with the SARS-CoV-2 B.1.1.7 variant demonstrated reduced activity against reference strains from earlier in the pandemic. Neutralizing activity of sera isolated from patients that had confirmed infection by the SARS-CoV-2 B.1.1.7 variant (n=29) was reduced against a parental reference strain isolated from Wuhan by 3.4-fold. In contrast,…
March 1, 2021
Antibodies with Potent and Broad Neutralizing Activity against Antigenically Diverse and Highly Transmissible SARS-CoV-2 Variants
[Pre-print, not peer-reviewed] A study identifying the structural and functional determinants of serum with broad neutralization of SARS-CoV-2 determined that combinations of two antibodies with broadly neutralizing activity decrease the in vitro generation of escape mutants. The structural characteristics of four monoclonal receptor-binding domain-targeting antibodies isolated from three early-outbreak convalescent donors with broadly neutralizing polyclonal…
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