Non-classical CD45RBlo memory B-cells are the majority of circulating antigen-specific B-cells following mRNA vaccination and COVID-19 infection. (preprint)

Resting memory B-cells can be divided into classical and non-classical groups based on differential expression of markers such as CD27 and CD11c, while activated memory B-cells express a combination of markers, making their ontogeny hard to determine. Here by longitudinal analysis of COVID-19, bacterial sepsis, and BNT162b2 mRNA vaccine recipients by mass cytometry and CITE-seq we describe a three-branch structure of resting B-cell memory consisting of “classical” CD45RB+ memory and two branches of CD45RBlo memory further defined by expression of CD23 and CD11c respectively. Stable differences in CD45RB upon activation allowed tracking of activated B-cells and plasmablasts derived from CD45RB+ classical and CD45RBlo non-classical memory B-cells. In both COVID-19 patients and mRNA vaccination, CD45RBlo B-cells formed the majority of SARS-CoV2 specific memory B-cells and correlated with serum antibodies while CD45RB+ memory was most strongly activated by bacterial Sepsis. These results suggest that diverse non-classical CD45RBlo memory B-cells consisting of branches of CD11c+Tbet+ and CD23+ fractions form a critical part of responses to viral infection and vaccination.

Classification of patients with COVID-19 by blood RNA endotype: A prospective cohort study (preprint)

Background: Although the development of vaccines has considerably reduced the severity of COVID-19, its incidence is still high. Hence, a targeted approach based on RNA endotypes of a population should be developed to help design biomarker-based therapies for COVID-19. Objectives: We evaluated the major RNAs transcribed in blood cells during COVID-19 using PCR to further elucidate its pathogenesis and determine predictive phenotypes in COVID-19 patients. Study design: In a discovery cohort of 40 patients with COVID-19, 26,354 RNAs were measured on day 1 and day 7. Five RNAs associated with disease severity and prognosis were derived. In a validation cohort of 153 patients with COVID-19 treated in the intensive care unit, we focused on prolactin (PRL), and toll-like receptor 3 (TLR3) among RNAs, which have a strong association with prognosis, and evaluated the accuracy for predicting survival of PRL-to-TL3 ratios (PRL/TLR3) with the areas under the ROC curves (AUC). The validation cohort was divided into two groups based on the cut-off value in the ROC curve with the maximum AUC. The two groups were defined by high PRL/TLR3 (n=47) and low PRL/TLR3 groups (n=106) and the clinical outcomes were compared. Results: In the validation cohort, the AUC for PRL/TLR3 was 0.79, showing superior prognostic ability compared to severity scores such as APACHE II and SOFA. The high PRL/TLR3 group had a significantly higher 28-day mortality than the low PRL/TLR3 group (17.0% vs 0.9%, P<0.01). Conclusions: A new RNA endotype classified using high PRL/TLR3 was associated with mortality in COVID-19 patients.

High-flow Nasal Cannula Oxygen Therapy as Initial Respiratory Management for Severe COVID-19-induced Respiratory Failure: a Single-center Observational Study (preprint)

Background: The efficacy and safety of high-flow nasal cannula (HFNC) oxygen therapy in severe respiratory failure, especially induced by COVID-19, has not been fully elucidated. We aimed to examine the usefulness of HFNC compared to invasive mechanical ventilation (IMV) as initial respiratory management for severe COVID-19-induced respiratory failure.Methods: In this retrospective observational study, we enrolled and categorized the patients with COVID-19-induced severe respiratory failure who were intolerant of conventional oxygen therapy into two groups: 1) patients who initially received HFNC (HFNC group) and 2) patients who initially underwent IMV (IMV group). The primary outcome was in-hospital mortality. The secondary outcomes were ventilator-free days within 28 days, intensive care unit (ICU)-free days within 28 days, and respiratory failure days defined as the length from day 1 to achieving successful weaning from both HFNC and IMV.Results: We analyzed 182 patients (HFNC group, n=81; IMV group, n=101). There was no difference in in-hospital mortality between the two groups (19% in the HFNC group vs. 25% in the IMV group, p=0.37). Initial use of HFNC was not associated with mortality in the univariate analysis (OR, 0.69; CI, 0.34–1.42; p=0.31) and inverse probability of treatment weighting analysis using propensity scoring (OR, 1.01; CI, 0.37–2.77; p=0.984). Ventilator-free days within 28 days were significantly longer in the HFNC group than those in the IMV group (median, 22 days [interquartile range (IQR), 2–28 days] vs. median, 14 days [IQR, 0–20 days], p<0.001). ICU-free days within 28 days were significantly longer in the HFNC group than those in the IMV group (median, 23 days [IQR, 0–28 days] vs. median, 15 days [IQR, 0–20 days], p<0.001). Respiratory failure days were relatively shorter in the HFNC group, but the difference was not statistically significant (p=0.071).Conclusions: Among patients with severe COVID-19-induced respiratory failure, HFNC compared to IMV resulted in a statistically significant increase in ventilator-free and ICU-free days within 28 days without increasing in-hospital mortality. This study showed the potential for HFNC to be an effective alternative to IMV as initial respiratory management for severe COVID-19-induced respiratory failure.