Clinical predictors of donor antibody titre and correlation with recipient antibody response in a COVID-19 convalescent plasma clinical trial.

BACKGROUND: Convalescent plasma therapy for COVID-19 relies on transfer of anti-viral antibody from donors to recipients via plasma transfusion. The relationship between clinical characteristics and antibody response to COVID-19 is not well defined. We investigated predictors of convalescent antibody production and quantified recipient antibody response in a convalescent plasma therapy clinical trial. METHODS: Multivariable analysis of clinical and serological parameters in 103 confirmed COVID-19 convalescent plasma donors 28 days or more following symptom resolution was performed. Mixed-effects regression models with piecewise linear trends were used to characterize serial antibody responses in 10 convalescent plasma recipients with severe COVID-19. RESULTS: Donor antibody titres ranged from 0 to 1 : 3892 (anti-receptor binding domain (RBD)) and 0 to 1 : 3289 (anti-spike). Higher anti-RBD and anti-spike titres were associated with increased age, hospitalization for COVID-19, fever and absence of myalgia (all P < 0.05). Fatigue was significantly associated with anti-RBD (P = 0.03). In pairwise comparison amongst ABO blood types, AB donors had higher anti-RBD and anti-spike than O donors (P < 0.05). No toxicity was associated with plasma transfusion. Non-ECMO recipient anti-RBD antibody titre increased on average 31% per day during the first three days post-transfusion (P = 0.01) and anti-spike antibody titre by 40.3% (P = 0.02). CONCLUSION: Advanced age, fever, absence of myalgia, fatigue, blood type and hospitalization were associated with higher convalescent antibody titre to COVID-19. Despite variability in donor titre, 80% of convalescent plasma recipients showed significant increase in antibody levels post-transfusion. A more complete understanding of the dose-response effect of plasma transfusion amongst COVID-19-infected patients is needed.

Deep groundwater and potential subsurface habitats beneath an Antarctic dry valley.

The occurrence of groundwater in Antarctica, particularly in the ice-free regions and along the coastal margins is poorly understood. Here we use an airborne transient electromagnetic (AEM) sensor to produce extensive imagery of resistivity beneath Taylor Valley. Regional-scale zones of low subsurface resistivity were detected that are inconsistent with the high resistivity of glacier ice or dry permafrost in this region. We interpret these results as an indication that liquid, with sufficiently high solute content, exists at temperatures well below freezing and considered within the range suitable for microbial life. These inferred brines are widespread within permafrost and extend below glaciers and lakes. One system emanates from below Taylor Glacier into Lake Bonney and a second system connects the ocean with the eastern 18 km of the valley. A connection between these two basins was not detected to the depth limitation of the AEM survey (∼350 m).

Duration of antimicrobial therapy for nosocomial pneumonia: possible strategies for minimizing antimicrobial use in intensive care units.

OBJECTIVE: To review published data evaluating shorter courses of antibiotic therapy for nosocomial pneumonia and provide recommendations for minimizing antimicrobial use in intensive care units. DATA SOURCE: Literature was identified through MEDLINE (1966 through 6/2002) and a manual search of critical care, infectious disease, and pharmacy journals was conducted to identify relevant abstracts. DATA SYNTHESIS: Antibiotic use may be decreased by discontinuing therapy after 3 days in patients with low likelihood of nosocomial pneumonia. In addition, clinical guidelines or invasive diagnostic procedures may be effectively instituted to reduce duration of antibiotic therapy. CONCLUSION: Shorter-course antibiotic therapy may be beneficial in decreasing lengths of hospital and intensive care units stays, antimicrobial resistance, and total hospital costs. Further research is needed to determine the optimal duration of therapy in patients with nosocomial pneumonia.

Polarization of light from a pulsed dye laser: effects of solvent viscosity.

A pulsed dye laser is polarized by insertion of a tilted glass plate in the cavity. The degree of polarization depends upon the cavity losses for light of the two polarizations, and we have measured the dependence for lasers in which the dye (Rh 6G) is dissolved in solvents of various viscosities. It is found that the polarization is less for higher viscosity solvents. A rate equation model is used to make numerical estimates of the effect, and these are compared with the experimental data.