Characterisation of a putative oxidoreductase in Escherichia coli: YdgJ

Antibiotic resistance is one of the main challenges faced by humanity in the 21st century. In 2016, the Bolt lab identified by a genetic screen an uncharacterised putative oxidoreductase called YdgJ that conferred resistance to the antibiotic nalidixic acid in Escherichia coli. This protein was isolated and purified for in vitro study, and further genetic analysis of YdgJ was carried out in parallel. The genetic analysis revealed that the YdgJ gene did not convey nalidixic resistance, contrary to earlier experiments. Surprisingly, expression of YdgJ protein caused increased sensitivity to ROS. We predicted that YdgJ would bind to cofactor NAD(P), but this could not be confirmed experimentally. We gained evidence that the YdgJ protein formed a trimeric structure, in agreement with predictions from bioinformatics. Overall, the mechanism of action of YdgJ could not be uncovered, but several clues hinted towards a role in ROS detoxification or cell metabolism. Further experiments will be required to reach a full understanding of the YdgJ gene and its associated product

Characterisation of a putative oxidoreductase in Escherichia coli: YdgJ

Antibiotic resistance is one of the main challenges faced by humanity in the 21st century. In 2016, the Bolt lab identified by a genetic screen an uncharacterised putative oxidoreductase called YdgJ that conferred resistance to the antibiotic nalidixic acid in Escherichia coli. This protein was isolated and purified for in vitro study, and further genetic analysis of YdgJ was carried out in parallel. The genetic analysis revealed that the YdgJ gene did not convey nalidixic resistance, contrary to earlier experiments. Surprisingly, expression of YdgJ protein caused increased sensitivity to ROS. We predicted that YdgJ would bind to cofactor NAD(P), but this could not be confirmed experimentally. We gained evidence that the YdgJ protein formed a trimeric structure, in agreement with predictions from bioinformatics. Overall, the mechanism of action of YdgJ could not be uncovered, but several clues hinted towards a role in ROS detoxification or cell metabolism. Further experiments will be required to reach a full understanding of the YdgJ gene and its associated product

Two doses of the SARS-CoV-2 BNT162b2 vaccine enhance antibody responses to variants in individuals with prior SARS-CoV-2 infection

Understanding the impact of prior infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on the response to vaccination is a priority for responding to the coronavirus disease 2019 (COVID-19) pandemic. In particular, it is necessary to understand how prior infection plus vaccination can modulate immune responses against variants of concern. To address this, we sampled 20 individuals with and 25 individuals without confirmed previous SARS-CoV-2 infection from a large cohort of health care workers followed serologically since April 2020. All 45 individuals had received two doses of the Pfizer-BioNTech BNT162b2 vaccine with a delayed booster at 10 weeks. Absolute and neutralizing antibody titers against wild-type SARS-CoV-2 and variants were measured using enzyme immunoassays and pseudotype neutralization assays. We observed antibody reactivity against lineage A, B.1.351, and P.1 variants with increasing antigenic exposure, through either vaccination or natural infection. This improvement was further confirmed in neutralization assays using fixed dilutions of serum samples. The impact of antigenic exposure was more evident in enzyme immunoassays measuring SARS-CoV-2 spike protein–specific IgG antibody concentrations. Our data show that multiple exposures to SARS-CoV-2 spike protein in the context of a delayed booster expand the neutralizing breadth of the antibody response to neutralization-resistant SARS-CoV-2 variants. This suggests that additional vaccine boosts may be beneficial in improving immune responses against future SARS-CoV-2 variants of concern

HLA-DR polymorphism in SARS-CoV-2 infection and susceptibility to symptomatic COVID-19

SARS-CoV-2 infection results in different outcomes ranging from asymptomatic infection to mild or severe disease and death. Reasons for this diversity of outcome include differences in challenge dose, age, gender, comorbidity and host genomic variation. Human leukocyte antigen (HLA) polymorphisms may influence immune response and disease outcome. We investigated the association of HLAII alleles with case definition symptomatic COVID-19, virus-specific antibody and T-cell immunity. A total of 1364 UK healthcare workers (HCWs) were recruited during the first UK SARS-CoV-2 wave and analysed longitudinally, encompassing regular PCR screening for infection, symptom reporting, imputation of HLAII genotype and analysis for antibody and T-cell responses to nucleoprotein (N) and spike (S). Of 272 (20%) HCW who seroconverted, the presence of HLA-DRB1*13:02 was associated with a 6·7-fold increased risk of case definition symptomatic COVID-19. In terms of immune responsiveness, HLA-DRB1*15:02 was associated with lower nucleocapsid T-cell responses. There was no association between DRB1 alleles and anti-spike antibody titres after two COVID vaccine doses. However, HLA DRB1*15:01 was associated with increased spike T-cell responses following both first and second dose vaccination. Trial registration: NCT04318314 and ISRCTN15677965