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Background The goal of antimicrobial stewardship is to optimize antimicrobial therapy and clinical outcomes while minimizing the unintended consequences of antimicrobial use. With the majority of antibiotics prescribed in the outpatient setting, optimizing antimicrobial prescribing across the care continuum is necessary. We aimed to evaluate the effect of antimicrobial stewardship interventions on the rate of inappropriate antibiotic prescribing in three adult primary care clinics affiliated with a tertiary care hospital. Methods Antibiotic prescriptions were identified by filtering common antibiotics prescribed prior to and post intervention. Prescriptions were excluded if they were prescribed pre-procedure or if the patient had a recent hospitalization within 30 days of the outpatient visit. Appropriateness of antibiotics was determined by indication, agent, dose and duration. Institutional guidelines were created for most common infections treated in the pre-intervention period. Education to outpatient providers was completed in two in-person visits. Results A total of 258 prescriptions were reviewed between the pre- and post-intervention periods. The majority of patients were female (73-76%) and the median age was similar between both cohorts. The most common infection treated during the pre-intervention period was urinary tract infection, whereas skin and soft tissue infection was most common in the post-intervention period. During the baseline period, the inappropriate prescribing rate was 61%. After intervention, the rate was reduced to 55%. Conclusion The use of outpatient antimicrobial stewardship guidelines and provider education to reinforce knowledge demonstrated reductions in inappropriate antibiotic prescribing. Disclosures All Authors: No reported disclosures.

Background: Serological tests are crucial tools for assessments of SARS-CoV-2 exposure, infection and potential immunity. Their appropriate use and interpretation require accurate assay performance data. Method: We conducted an evaluation of 10 lateral flow assays (LFAs) and two ELISAs to detect anti-SARS-CoV-2 antibodies. The specimen set comprised 128 plasma or serum samples from 79 symptomatic SARS-CoV-2 RT-PCR-positive individuals; 108 pre-COVID-19 negative controls; and 52 recent samples from individuals who underwent respiratory viral testing but were not diagnosed with Coronavirus Disease 2019 (COVID-19). Samples were blinded and LFA results were interpreted by two independent readers, using a standardized intensity scoring system. Results: Among specimens from SARS-CoV-2 RT-PCR-positive individuals, the percent seropositive increased with time interval, peaking at 81.8–100.0% in samples taken >20 days after symptom onset. Test specificity ranged from 84.3–100.0% in pre-COVID-19 specimens. Specificity was higher when weak LFA bands were considered negative, but this decreased sensitivity. IgM detection was more variable than IgG, and detection was highest when IgM and IgG results were combined. Agreement between ELISAs and LFAs ranged from 75.7–94.8%. No consistent cross-reactivity was observed. Conclusion: Our evaluation showed heterogeneous assay performance. Reader training is key to reliable LFA performance, and can be tailored for survey goals. Informed use of serology will require evaluations covering the full spectrum of SARS-CoV-2 infections, from asymptomatic and mild infection to severe disease, and later convalescence. Well-designed studies to elucidate the mechanisms and serological correlates of protective immunity will be crucial to guide rational clinical and public health policies.

Neuroblastoma, an embryonal cancer of neural crest origin, shows metastases frequently at diagnosis. In this issue of Cancer Cell, Delloye-Bourgeois and colleagues demonstrate that neuroblastoma cell lines and patient-derived xenografts engraft and adopt a metastatic program in chick embryos. They identify Sema3C as a candidate switch that regulates metastatic spread.

Amplification of epidermal growth factor receptor (EGFR) and its active mutant EGFRvIII occurs frequently in glioblastoma (GBM). While EGFR and EGFRvIII play critical roles in pathogenesis, targeted therapy with EGFR-tyrosine kinase inhibitors (TKIs) or antibodies has only shown limited efficacy in patients. Here we discuss signaling pathways mediated by EGFR/EGFRvIII, current therapeutics, and novel strategies to target EGFR/EGFRvIII-amplified GBM.

ATP-dependent chromatin remodeling, which repositions and restructures nucleosomes, is essential to all DNA-templated processes. The INO80 chromatin remodeling complex is an evolutionarily conserved complex involved in diverse cellular processes, including transcription, DNA repair, and replication. The functional diversity of the INO80 complex can, in part, be attributed to specialized activities of distinct subunits that compose the complex. Furthermore, structural analyses have identified biochemically discrete subunit modules that assemble along the Ino80 ATPase scaffold. Of particular interest is the Saccharomyces cerevisiae Arp5-Ies6 module located proximal to the Ino80 ATPase and the Rvb1-Rvb2 helicase module needed for INO80-mediated in vitro activity. In this study we demonstrate that the previously uncharacterized Ies2 subunit is required for Arp5-Ies6 association with the catalytic components of the INO80 complex. In addition, Arp5-Ies6 module assembly with the INO80 complex is dependent on distinct conserved domains within Arp5, Ies6, and Ino80, including the spacer region within the Ino80 ATPase domain. Arp5-Ies6 interacts with chromatin via assembly with the INO80 complex, as IES2 and INO80 deletion results in loss of Arp5-Ies6 chromatin association. Interestingly, ectopic addition of the wild-type Arp5-Ies6 module stimulates INO80-mediated ATP hydrolysis and nucleosome sliding in vitro. However, the addition of mutant Arp5 lacking unique insertion domains facilitates ATP hydrolysis in the absence of nucleosome sliding. Collectively, these results define the requirements of Arp5-Ies6 assembly, which are needed to couple ATP hydrolysis to productive nucleosome movement.

Neuroblastoma (NB) is a malignant tumor that accounts for ~15% of all pediatric cancer mortality. Nearly half of patients present with high-risk disease that has poor outcome, and the proto-oncogene MYCN is amplified in 45% of high-risk cases. Further, relapsed neuroblastoma demonstrates frequent activation of mitogen activated protein kinase (MAPK) signaling, including mutations in tumor suppressor NF1 and epigenetic silencing of the gene. Human induced pluripotent stem cells (iPSCs) represent a valuable tool by which to further dissect the genetic requirements of high-risk NB. Human iPSCs are superior to genetically engineered mouse models (GEMMs) at capturing the telomere biology and chromosomal landscape of primary human neuroblastoma. Further, they can be genetically manipulated to determine the genetic drivers of the disease. As proof of principle, we first differentiated normal human iPSCs toward trunk neural crest cells (NCC), the putative cells of origin for NB. We subsequently introduced established genetic drivers of NB (MYCN, ALK) and orthotopically implanted the resulting trunk NCCs into the renal capsules of immunocompromised mice. Three months post injection, tumors developed in 60% of MYCN/ALK mice, 10% in MYCN alone, and no tumors developed in ALK alone or empty vector. Tumors were transplantable and expressed markers typically found in NB, while lacking markers of other tumors such as rhabdomyosarcoma, Ewing sarcoma, and lymphoma. To show we can use our model to evaluate candidate drivers of NB, we knocked out NF1 in MYCN trunk NCCs using CRISPR/Cas9 and implanted these cells orthotopically in mice. 80% of mice with MYCN/NF1 modified cells developed tumors while NF1 knockout alone did not. Thus, we have generated the first human iPSC model of NB driven by MYCN and have shown the utility of our model in validating cooperating mutations. MH and TZ contributed equally to this work.

Background Although natural regulatory T cells (nTregs) can suppress osteoclastogenesis, the role of TGF-β-induced CD4+Foxp3+ Tregs (iTregs) in osteoclastogenesis remains unknown. Objective To determine the effects of iTregs on osteoclastogenesis in vitro and on bone erosion in vivo in collagen-induced arthritis (CIA). Methods Osteoclastogenesis was induced in bone marrow CD11b+ cells with receptor activator of nuclear factor κ B (NF-κB) ligand (RANKL) and macrophage colony stimulating factor. Graded doses of Tregs were added to inhibit osteoclastogenesis. Transwell and antibody blockade experiments were performed to assess the roles for cell contact and soluble cytokines. NF-κB activation was determined by western blot. iTregs or nTregs were adoptively transferred to mice with CIA to assess in vivo effects on disease incidence and bone erosion, the latter determined by CT scanning. Results Both nTregs and iTregs greatly suppressed osteoclastogenesis in vitro, but only iTregs sustained this effect when interleukin-6 was present. iTregs, but not nTregs, significantly suppressed development of CIA. Bone erosions in iTregs-treated mice were diminished compared with untreated mice or nTregs-treated mice. Treatment with iTregs, but not with nTregs, dramatically decreased NF-κB p65/p50 levels in osteoclasts in vitro and p65/50 and RANKL expression by synovial tissues in vivo. Conclusion iTregs may be therapeutically beneficial in rheumatoid arthritis and related diseases associated with bone erosions.