Cilia-related gene signature in the nasal mucosa correlates with disease severity and outcomes in critical respiratory syncytial virus bronchiolitis

Background

Respiratory syncytial virus (RSV) can cause life-threatening respiratory failure in infants. We sought to characterize the local host response to RSV infection in the nasal mucosa of infants with critical bronchiolitis and to identify early admission gene signatures associated with clinical outcomes.

Methods

Nasal scrape biopsies were obtained from 33 infants admitted to the pediatric intensive care unit (PICU) with critical RSV bronchiolitis requiring non-invasive respiratory support (NIS) or invasive mechanical ventilation (IMV), and RNA sequencing (RNA-seq) was performed. Gene expression in participants who required shortened NIS (</= 3 days), prolonged NIS (> 3 days), and IMV was compared.

Findings

Increased expression of ciliated cell genes and estimated ciliated cell abundance, but not immune cell abundance, positively correlated with duration of hospitalization in infants with critical bronchiolitis. A ciliated cell signature characterized infants who required NIS for > 3 days while a basal cell signature was present in infants who required NIS for </= 3 days, despite both groups requiring an equal degree of respiratory support at the time of sampling. Infants who required invasive mechanical ventilation had increased expression of genes involved in neutrophil activation and cell death.

Interpretation

Increased expression of cilia-related genes in clinically indistinguishable infants with critical RSV may differentiate between infants who will require prolonged hospitalization and infants who will recover quickly. Validation of these findings in a larger cohort is needed to determine whether a cilia-related gene signature can predict duration of illness in infants with critical bronchiolitis. The ability to identify which infants with critical RSV bronchiolitis may require prolonged hospitalization using non-invasive nasal samples would provide invaluable prognostic information to parents and medical providers.

777. Implementation of Antimicrobial Impregnated Catheters to Reduce Central Line Associated Bloodstream Infections (CLABSI) in a Pediatric Setting

Background

Antimicrobial impregnated catheters (AIC) are one strategy to prevent CLABSI with existing data for central lines required for short duration, however, the strength of evidence, particularly for children, is lacking. Recent 3-year CLABSI data at our institution show 60 (51%) infections occurred in central lines within 8 weeks of insertion, suggesting an opportunity for evaluation of an intervention targeting this time frame. We implemented AIC to evaluate their effectiveness in reducing CLABSI standardized infection ratio (SIR) in patients requiring central venous access for less than 8 weeks. We also monitored for complications (malfunction, line exchange, fungal infection).

Methods

A stepped wedge observational design was used to implement Minocycline + Rifampin impregnated catheters in a rolling fashion across the institution. Children > 3kg were eligible if admitted to a participating unit and required central venous access through a peripherally inserted central catheter (PICC), non-tunneled catheter, or tunneled non-cuffed femoral catheter for < 8 weeks. Units, prioritized based on CLABSI SIR, were added to the intervention monthly until AIC were used throughout the institution. A multidisciplinary team (infectious diseases and infection control experts, CLABSI leaders, unit-based physicians and nurses, proceduralists, supply chain) met weekly to facilitate implementation, assess for CLABSI and monitor for complications.

Figure 1. Study design.

This figure describes the stepped wedge study design where units were phased into the invention on a rolling monthly basis allowing for comparison between and within units. The shaded boxes represent time periods when units were using antimicrobial impregnated catheters and the white boxes represent time periods when units were using standard non-impregnated catheters.

Results

AIC were systematically implemented over a 7-month period. The institution’s CLABSI SIR decreased from 0.80 to 0.59 during this timeframe. There were no NHSH defined CLABSI in patients with an AIC during the intervention. Obstacles included shortage of catheters due to supply chain disruption, adjustment of technique for line insertion and cracked/broken lines. Infections and complications were reviewed by the multidisciplinary team and compared to historical rates with non-impregnated lines.

This figure shows the institution’s rolling 12-month SIR during the intervention period.

Conclusion

CLABSI SIR decreased at our institution during the intervention period. While many efforts likely led to this reduction (optimizing maintenance bundle, unit based CLABSI initiatives), we believe the use of AIC contributed to this improvement. There were no pediatric-specific safety events identified during implementation.

Disclosures

Ravi Jhaveri, MD, AstraZeneca (Consultant)Dynavax (Consultant)Elsevier (Other Financial or Material Support, Editorial stipend as Co-EiC, Clinical Therapeutics)Hologic (Consultant)Seqirus (Consultant)

Age-related Differences in the Nasal Mucosal Immune Response to SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected more than 180 million people since the onset of the pandemic. Despite similar viral load and infectivity rates between children and adults, children rarely develop severe illness. Differences in the host response to the virus at the primary infection site are among the mechanisms proposed to account for this disparity. Our objective was to investigate the host response to SARS-CoV-2 in the nasal mucosa in children and adults and compare it with the host response to respiratory syncytial virus (RSV) and influenza virus. We analyzed clinical outcomes and gene expression in the nasal mucosa of 36 children with SARS-CoV-2, 24 children with RSV, 9 children with influenza virus, 16 adults with SARS-CoV-2, and 7 healthy pediatric and 13 healthy adult controls. In both children and adults, infection with SARS-CoV-2 led to an IFN response in the nasal mucosa. The magnitude of the IFN response correlated with the abundance of viral reads, not the severity of illness, and was comparable between children and adults infected with SARS-CoV-2 and children with severe RSV infection. Expression of ACE2 and TMPRSS2 did not correlate with age or presence of viral infection. SARS-CoV-2–infected adults had increased expression of genes involved in neutrophil activation and T-cell receptor signaling pathways compared with SARS-CoV-2–infected children, despite similar severity of illness and viral reads. Age-related differences in the immune response to SARS-CoV-2 may place adults at increased risk of developing severe illness.

Transverse bunch-by-bunch feedback system for time-resolved experiments at PLS-II

A description of the upgraded bunch-by-bunch feedback system for time-resolved experiments at Pohang Light Source II (PLS-II) is provided. The bunch-by-bunch feedback system has been upgraded to increase the single-bunch current in the hybrid fill pattern of the PLS-II facility. The project is part of the SPring-8 and PLS-II collaboration. The main features of the upgrade are to employ a single 500 MHz analog-to-digital converter (ADC) instead of the previous four 125 MHz interleaved ADCs for 500 MHz rate, to replace a single-loop two-dimensional feedback with two independent one-dimensional feedback loops, to implement the tune measurement function with a single bunch, and mainly to implement single-bunch and stretcher control. The realization of a 400 mA hybrid fill pattern including a 10 mA single bunch demonstrates the precision of the upgraded bunch-by-bunch feedback system.

Immune response to SARS-CoV-2 in the nasal mucosa in children and adults

Rationale:

Despite similar viral load and infectivity rates between children and adults infected with SARS-CoV-2, children rarely develop severe illness. Differences in the host response to the virus at the primary infection site are among the proposed mechanisms.

Objectives:

To investigate the host response to SARS-CoV-2, respiratory syncytial virus (RSV), and influenza virus (IV) in the nasal mucosa in children and adults.

Methods:

Clinical outcomes and gene expression in the nasal mucosa were analyzed in 36 children hospitalized with SARS-CoV-2 infection, 24 children with RSV infection, 9 children with IV infection, 16 adults with mild to moderate SARS-CoV-2 infection, and 7 healthy pediatric and 13 healthy adult controls.

Results:

In both children and adults, infection with SARS-CoV-2 leads to an interferon response in the nasal mucosa. The magnitude of the interferon response correlated with the abundance of viral reads and was comparable between symptomatic children and adults infected with SARS-CoV-2 and symptomatic children infected with RSV and IV. Cell type deconvolution identified an increased abundance of immune cells in the samples from children and adults with a viral infection. Expression of ACE2 and TMPRSS2 - key entry factors for SARS-CoV-2 - did not correlate with age or presence or absence of viral infection.

Conclusions:

Our findings support the hypothesis that differences in the immune response to SARS-CoV-2 determine disease severity, independent of viral load and interferon response at the primary infection primary site.

Biochemical characterization and microsequencing of a 205-kDa synovial protein stimulatory for T cells and reactive with rheumatoid factor containing sera

Synovial fluid (SF) was found to possess stimulatory capacity for the proliferation of T cell clones derived from patients with rheumatoid arthritis (RA) when cultured together with IL-2. Using chromatography technique and gel electrophoresis, a synovial fluid protein with an apparent m.w. of 205 kDa (p205) was isolated that demonstrated a bioactivity analogous to that obtained with native synovial fluid. After electroelution, p205 dissociated into 70-kDa fragment(s). Upon IEF, it appeared as a single band with an isoelectric point of 6.5, suggesting a noncovalently bound trimer complex. Amino acid sequences of the whole protein and of tryptic peptides were determined by N terminal sequencing. The N terminal amino acid sequence of the 70-kDa fragment and of the tryptic peptides showed no identity to recently described protein sequences. One peptide matched, in 11 amino acid residues, with the human IgG1-4 constant heavy chain and rheumatoid factor (RF) binding region. The p205 induced the proliferation of peripheral blood T cells and long term T cell cultures that had been raised by alternate stimulation with IL-2 and p205. In a similar approach, synovial lining cells were shown to release a protein with biochemical characteristics similar to the synovial fluid-derived p205. Western blot analysis revealed the binding of RF-containing sera to p205, which was diminished by absorption with an RF reagent. These observations suggest that p205 is expressed by synovial cells and may be a target for T and B cells in RA.

Biochemical characterization and microsequencing of a 205-kDa synovial protein stimulatory for T cells and reactive with rheumatoid factor containing sera

Synovial fluid (SF) was found to possess stimulatory capacity for the proliferation of T cell clones derived from patients with rheumatoid arthritis (RA) when cultured together with IL-2. Using chromatography technique and gel electrophoresis, a synovial fluid protein with an apparent m.w. of 205 kDa (p205) was isolated that demonstrated a bioactivity analogous to that obtained with native synovial fluid. After electroelution, p205 dissociated into 70-kDa fragment(s). Upon IEF, it appeared as a single band with an isoelectric point of 6.5, suggesting a noncovalently bound trimer complex. Amino acid sequences of the whole protein and of tryptic peptides were determined by N terminal sequencing. The N terminal amino acid sequence of the 70-kDa fragment and of the tryptic peptides showed no identity to recently described protein sequences. One peptide matched, in 11 amino acid residues, with the human IgG1-4 constant heavy chain and rheumatoid factor (RF) binding region. The p205 induced the proliferation of peripheral blood T cells and long term T cell cultures that had been raised by alternate stimulation with IL-2 and p205. In a similar approach, synovial lining cells were shown to release a protein with biochemical characteristics similar to the synovial fluid-derived p205. Western blot analysis revealed the binding of RF-containing sera to p205, which was diminished by absorption with an RF reagent. These observations suggest that p205 is expressed by synovial cells and may be a target for T and B cells in RA.