Viral Load Dynamics in SARS-CoV-2 Omicron Breakthrough Infections.

To determine viral dynamics in Omicron breakthrough infections, we measured severe acute respiratory syndrome coronavirus 2 RNA in 206 double-vaccinated or boostered individuals. During the first 3 days following the onset of symptoms, viral loads were significantly higher (cycle threshold [Ct], 21.76) in vaccinated compared to boostered (Ct, 23.14) individuals (P = .029). However, by performing a longitudinal analysis on 32 individuals over 14 days, no difference in the viral load trajectory was observed between double-vaccinated and boostered patients. Our results indicate that booster immunization results in a reduction in detectable viral loads without significantly changing viral load dynamics over time.

No substantial preexisting B cell immunity against SARS-CoV-2 in healthy adults.

Preexisting immunity against SARS-CoV-2 may have critical implications for our understanding of COVID-19 susceptibility and severity. The presence and clinical relevance of a preexisting B cell immunity remain to be fully elucidated. Here, we provide a detailed analysis of the B cell immunity to SARS-CoV-2 in unexposed individuals. To this end, we extensively investigated SARS-CoV-2 humoral immunity in 150 adults sampled pre-pandemically. Comprehensive screening of donor plasma and purified IgG samples for binding and neutralization in various functional assays revealed no substantial activity against SARS-CoV-2 but broad reactivity to endemic betacoronaviruses. Moreover, we analyzed antibody sequences of 8,174 putatively SARS-CoV-2-reactive B cells at a single cell level and generated and tested 158 monoclonal antibodies. None of these antibodies displayed relevant binding or neutralizing activity against SARS-CoV-2. Taken together, our results show no evidence of competent preexisting antibody and B cell immunity against SARS-CoV-2 in unexposed adults.

Staurosporine resistance in inflammatory neutrophils is associated with the inhibition of caspase- and proteasome-mediated Mcl-1 degradation.

Apoptosis resistance in activated neutrophils is known to be associated with collateral damage of surrounding tissue, as well as immune and organ dysfunction. Thus, the safe removal of neutrophils by apoptosis induction represents a prerequisite for the resolution of inflammation. Here, we report that intrinsic apoptosis resistance in human neutrophils, isolated from severely injured patients, is based on enhanced stabilization of antiapoptotic myeloid cell leukemia 1 and subsequent impairment of downstream apoptotic pathways. Whereas extrinsic apoptosis induction by the activation of Fas death receptor on inflammatory neutrophils was accompanied by caspase- and proteasome-mediated myeloid cell leukemia 1 degradation, intrinsic apoptosis induction by staurosporine led to a significant stabilization of myeloid cell leukemia 1 protein, which impeded on truncated forms of B cell lymphoma 2-associated X protein and B cell lymphoma 2 homology domain 3-interacting domain death translocation and subsequent cytochrome c release from the mitochondria. We show further that profound inhibition of myeloid cell leukemia 1 degradation is based on the inhibition of caspases and sustained activation of kinases involved in cell survival, such as Akt. Accordingly, impeded myeloid cell leukemia 1 phosphorylation on Ser159 by glycogen synthase kinase 3 and protein ubiquitination has been demonstrated. Inhibition of myeloid cell leukemia 1 activity markedly increased sensitivity to staurosporine-induced cell death. Altogether, these results provide new insights into the mechanisms underlying myeloid cell leukemia 1-mediated apoptosis resistance to staurosporine under inflammatory situations and should be considered for the development of novel therapeutic strategies.