Serum KL-6 and surfactant protein D in children with 2009 pandemic H1N1 influenza infection

Pulmonary surfactants and the respiratory-renal connection in steroid-sensitive nephrotic syndrome of childhood

Steroid-sensitive nephrotic syndrome (SSNS) in childhood is usually due to minimal change disease (MCD). Unlike many glomerular conditions, SSNS/MCD is commonly precipitated by respiratory infections. Of interest, pulmonary inflammation releases surfactants in circulation which are soluble agonists of SIRPα, a podocyte receptor that regulates integrin signaling. Here, we characterized this pulmonary-renal connection in MCD and performed studies to determine its importance. Children with SSNS/MCD in relapse but not remission had elevated plasma surfactants and urinary SIRPα. Sera from relapsing subjects triggered podocyte SIRPα signaling via tyrosine phosphatase SHP-2 and nephrin dephosphorylation, a marker of podocyte activation. Further, addition of surfactants to MCD sera from patients in remission replicated these findings. Similarly, nasal instillation of toll-like receptor 3 and 4 agonists in mice resulted in elevated serum surfactants and their binding to glomeruli triggering proteinuria. Together, our data document a critical pulmonary-podocyte signaling pathway involving surfactants and SIRPα signaling in SSNS/MCD.

Analysis of Early Biomarkers Associated with the Development of Critical Respiratory Failure in Coronavirus Disease 2019 (COVID-19)

Certain biomarkers predict death due to acute respiratory distress syndrome in COVID-19 patients. We retrospectively analyzed biomarkers associated with time to mechanical ventilation for respiratory failure due to COVID-19 (time-to-mechanical ventilation) in 135 consecutive patients in our hospital. We analyzed biomarkers that were elevated immediately (at admission) and later (3 days after admission) using Cox proportional hazards regression analysis. Independent biomarkers of time-to-mechanical ventilation were high C-reactive protein (CRP), interleukin (IL)-6, and Krebs von den Lungen-6 (KL-6) concentrations at admission and elevated CRP, high-mobility group box-1 protein (HMGB-1), and d-dimer levels and low platelets 3 days after admission. Receiver operating characteristic analysis for detecting the association between independent biomarkers associated with time-to-event in multivariate analyses and the start of mechanical ventilation revealed that these biomarkers had area under the curve values higher than 0.700. The present study suggests that CRP was the only biomarker associated with time-to-mechanical ventilation both at admission and 3 days after admission. Moreover, IL-6 (an inflammatory cytokine), HMGB-1 (a late inflammatory mediator), and KL-6 (reflecting injury and/or remodeling of type II pneumocytes) were associated with outcomes in COVID-19 as reported previously. In conclusion, increased CRP, IL-6, KL-6, HMGB-1, and d-dimer levels and decreased platelet counts were associated with the start of mechanical ventilation due to COVID-19.

Serum surfactant protein D (SP-D) is a prognostic marker of poor outcome in patients with A/H1N1 virus infection

Introduction

Surfactant protein D (SP-D) plays an important role in the innate responses against pathogens and its production is altered in lung disorders.

Methods

We studied the circulating levels of SP-D in 37 patients with acute respiratory distress syndrome due to the A/H1N1 virus infection and in 40 healthy controls. Cox logistic regression models were constructed to explore the association of SP-D levels and risk of death.

Results

Mortality rate after a 28-day was 32.42 %. Significant higher levels of SP-D were detected in A/H1N1 patients with fatal outcome (p < 0.05). After adjusting for confounding variables, levels of SP-D ≥250 ng/mL were associated with increased the risk of death (HR = 8.27, 95 % CI 1.1–64.1, p = 0.043).

Conclusions

Our results revealed that higher circulating levels of SP-D are associated with higher mortality risk in critically ill A/H1N1 patients. SP-D might be a predictive factor of poor outcomes in viral pneumonia.

Factors influencing the measurement of plasma/serum surfactant protein D levels by ELISA

Background

Extensive variations in human surfactant protein D (SP-D) levels in circulation as measured by ELISA exist in the published literature. In order to determine the source of these variations, factors influencing the measurement by ELISA were explored.

Materials and Methods

Peripheral blood from healthy individuals was collected into various vacutainers during the same blood draw. Recombinant SP-D was diluted into different matrices and used for a standard curve. Samples were analyzed by capture ELISA using one of two distinct detection antibodies.

Results

The type of matrix had some effects on detection of recombinant SP-D. The type of anticoagulant used and dilution factor had very little effect, except for in plasma collected in EDTA vacutainers. The extent of variation in published values seemed to be due to the ELISA configuration employed, and, in agreement with this, we found that by switching the detection antibody, there was a 50% decrease in the extrapolated SP-D value of serum and plasma samples. Storage of samples resulted in slight changes in measured SP-D levels.

Conclusions

The ELISA configuration employed to measure circulating levels of SP-D has a significant effect on the extrapolated values. In both configurations tested, the use of EDTA as a coagulant resulted in inconsistent values, and we, therefore, suggest the avoidance of this anticoagulant when assaying for SP-D by ELISA. While the demonstrated effects of several factors on measurement of SP-D may not account for all the disparities amongst the previous studies, they stress that variations in methodologies for measuring the same protein can result in very inconsistent results.