Objective. To determine whether serum amyloid A (SAA) is internalized by and processed in macrophages en route to deposition as extracellular amyloid.Methods. SAA was tracked in cultures of peritoneal macrophages, using a pulse-chase protocol. Conclusion. The results of this study provide direct evidence that SAA internalized by and processed in macrophages forms extracellular amyloid. Based on the presence of 125 I-AA protein in macrophage lysates prior to the appearance of extracellular TxR-labeled amyloid, it was concluded that cleavage of SAA to AA occurs intracellularly.

Murine serum amyloid A1.1 (SAA1.1) has been conjugated with the fluorophore Texas Red (TxR), and its interaction with peritoneal macrophages has been visualized by scanning confocal microscopy. Binding of TxR±SAA to cell surfaces was inhibited by an excess of unlabelled SAA indicating the involvement of saturable receptors. Internalized TxR±SAA was seen initially as small punctate signals which in some cells evolved into a fine fluorescent network, a pattern typical of tubular endosomes. Colocalization of TxR±SAA with Cy5-labelled low density lipoprotein (LDL) but not with Oregon Green-labelled transferrin suggested that SAA trafficked through endosomes and lysosomes for degradation rather than through recycling compartments. Consistent with this catabolic pathway, macrophages loaded with TxR±SAA lost fluorescence within several days after being shifted to a fluorophore-free medium. In sharp contrast to this, cells maintained under amyloid-forming conditions, i.e. in the presence of unlabelled SAA and amyloidenhancing factor (AEF) before and after treatment with TxR±SAA, remained brightly fluorescent over the course of 5 days. Immunocytochemistry verified the accumulation of SAA within macrophages. These findings support the hypothesis that a decreased catabolism of internalized SAA plays a role in AA amyloid pathogenesis.

Background Although intravenous immunoglobulin (IVIG) is effective therapy for Kawasaki disease, 10-20% of patients have recrudescent fever as a sign of persistent inflammation and require additional treatment. We aimed to compare infliximab with a second infusion of IVIG for treatment of resistant Kawasaki disease.Methods In this multicentre comparative effectiveness trial, patients (aged 4 weeks to 17 years) with IVIG resistant Kawasaki disease and fever at least 36 h after completion of their first IVIG infusion were recruited from 30 hospitals across the USA. Patients were randomly assigned (1:1) to second IVIG (2 g/kg over 8-12 h) or intravenous infliximab (10 mg/kg over 2 h without premedication), by using a randomly permuted block randomisation design with block size of two or four. Patients with fever 24 h to 7 days following completion of first study treatment crossed over to receive the other study treatment. The primary outcome measure was resolution of fever at 24 h after initiation of study treatment with no recurrence of fever attributed to Kawasaki disease within 7 days post-discharge. Secondary outcome measures included duration of fever from enrolment, duration of hospitalisation after randomisation, and changes in markers of inflammation and coronary artery Z score. Efficacy was analysed in participants who received treatment and had available outcome values. Safety was analysed in all randomised patients who did not withdraw consent. This clinical trial is registered with ClinicalTrials.gov, NCT03065244.

Key Points Question How did the incidence and nature of Kawasaki disease (KD) in the United States change during the COVID-19 pandemic? Findings In this cohort study of 3922 children with KD, cases of KD across the United States fell by 28% and remained low during periods of COVID-19–related masking and school closure. In the San Diego region, there was a disproportionate decline in KD cases in children aged 1 to 5 years, male children, and Asian children, and clinical features including strawberry tongue, enlarged cervical lymph node, and subacute periungual desquamation were rare. Meaning These findings suggest that social behavior is associated with exposure to the agent(s) that trigger KD and are consistent with a respiratory portal of entry for the agent(s).

ObjectivesWe evaluated the performance and time to result for pathogen identification (ID) and antimicrobial susceptibility testing (AST) of the Accelerate Pheno™ system (AXDX) compared with standard of care (SOC) methods. We also assessed the hypothetical improvement in antibiotic utilization if AXDX had been implemented.MethodsClinical samples from patients with monomicrobial Gram-negative bacteraemia were tested and compared between AXDX and the SOC methods of the VERIGENE® and Bruker MALDI Biotyper® systems for ID and the VITEK® 2 system for AST. Additionally, charts were reviewed to calculate theoretical times to antibiotic de-escalation, escalation and active and optimal therapyResultsID mean time was 21 h for MALDI-TOF MS, 4.4 h for VERIGENE® and 3.7 h for AXDX. AST mean time was 35 h for VITEK® 2 and 9.0 h for AXDX. For ID, positive percentage agreement was 95.9% and negative percentage agreement was 99.9%. For AST, essential agreement was 94.5% and categorical agreement was 93.5%. If AXDX results had been available to inform patient care, 25% of patients could have been put on active therapy sooner, while 78% of patients who had therapy optimized during hospitalization could have had therapy optimized sooner. Additionally, AXDX could have reduced time to de-escalation (16 versus 31 h) and escalation (19 versus 31 h) compared with SOC. ConclusionsBy providing fast and reliable ID and AST results, AXDX has the potential to improve antimicrobial utilization and enhance antimicrobial stewardship.