462. Differences in the Humoral Response to SARS-CoV-2 Infection in Children vs. Adult

Background One of the most striking observations of the COVID-19 pandemic has been the difference in infection among children vs. adults. Overall, children with SARS-CoV-2 infection generally had milder disease compared to adults, though the cause is not clear. The objective of this study was to compare the humoral response to infection in children vs. adults of a same family. Methods We performed a prospective cohort study at Sainte-Justine University Health Center in Montreal, Canada from July 2020 to March 2021. Children with a positive SARS-CoV-2 PCR were recruited from the COVID-19 clinic (index case), enrollment was offered to all household members. Serum IgG against SARS-CoV-2 native S1/S2 spike proteins was measured using the Diasorin (Liaison XL) assay, 4-6 months following a positive PCR. A mean antibody threshold of 15 Arbitrary unit per ml (AU/ml) was considered seropositive, with 94.4% positive agreement to plaque reduction neutralization tests (PRNT90) at a 1:40 ratio. Antibody titer was compared between children and adults. Results 111 participants (52 adults and 59 children) were recruited from 50 separate families. Characteristic of participants and their clinical symptoms are described in Table 1. Among all participants, 76.3% children were SARS-CoV-2 seropositive vs. 51.9% of adults (p=0.007). Median antibody titer was significantly higher in children vs. adults (82.8 AU, [IQR: 18.4-130], vs 17.0 AU, [IQR: 6.8-77.8], p=0.006); findings were similar among SARS-CoV-2 PCR positive participants only. Overall, 13 participants were PCR positive but seronegative, 7 were PCR negative and seropositive, while 61 were both PCR positive and seropositive. Older participants and those with any comorbidity. Among the PCR positive group, the seropositive participants were younger (median age 31±17 vs 19±17 years, p=0.003) and more likely to have comorbidity (69% vs 29%, p=0.007). Conclusion These results suggest that children have a stronger antibody response to SARS-CoV-2 infection than adults, and that older age and presence of comorbidity are associated with a less robust humoral response. Further work on the differences in response between children and adults may help elucidate mechanisms underlying the severity of disease Disclosures Olivier Drouin, MDCM MsC MPH, Covis Pharma (Research Grant or Support)

999. Nasal Mucosal Cytokines: Potential Biomarkers for Pediatric Pneumonia Severity and Etiology

Background Community acquired pneumonia (CAP) is a leading cause of mortality in children < 5 years, but our understanding of disease pathogenesis remains limited. The objective of this study was to define the local host immune response in the respiratory tract by measuring nasal mucosal cytokine (NMC) concentrations (conc.). We hypothesized that NMC represent a potential biomarker to help assessing disease severity and pathogen classification. Methods We leveraged nasopharyngeal (NP) samples and clinical data from an observational multicenter study [Children’s Hospital’s Initiative for Research in Pneumonia (CHIRP)] conducted between 2015 and 2018. We measured conc. of 92 NMC using the Olink immunoassay. NMC conc. were compared by severity-defined by need for hospitalization, mild (outpatient) and severe (inpatient), and by identified pathogen using Mann-Whitney U test. Results This substudy included 182 children with CAP (mild=61; severe=121) and 30 healthy controls (HC). The pathogens identified included: 101 viruses; 32 bacteria (pyogenic=10; atypical=22); 12 with >1 pathogen; and 37 with no pathogen. Children with severe CAP had greater CCL23 and MCP-3 conc. than those with mild disease (p=0.012; p=0.011 respectively). When comparing NMC profiles of children with CAP of viral and bacterial etiology, the viral group had greater conc. of proinflammatory cytokines IL-6 and TNF, (p=0.0002; p=0.0098 respectively). Further subgroup analysis showed that CAP secondary to influenza virus had greater conc. of IL-6, TNF, and antiviral INF-γ and IP-10 compared with CAP caused by pyogenic bacteria. IL-6 and MCP1-4 were significantly increased in the influenza group compared to the atypical bacteria group. Quantification of NMC in children with CAP based on disease severity NMC nasal mucosal cytokine; CAP: community acquired pneumonia; NPX: normalized protein expression, arbitrary unit used in Olink assay that is log 2 scale. Mann-Whitney test was used to determine differences between mild and severe pneumonia Quantification of NMC in children with CAP based on pathogen classification NMC: nasal mucosal cytokine; CAP: community acquired pneumonia; NPX: normalized protein expression, arbitrary unit used in Olink assay that is log 2 scale. Mann-Whitney test was used to determine differences between bacterial CAP and viral CAP. Conclusion Children with severe CAP had higher monocyte chemoattractant NMC conc. than children with mild disease. Children with viral CAP, particularly influenza, had a more robust mucosal response including both proinflammatory and antiviral NMC than children with bacterial CAP. These findings show differences in NMC conc. based on etiology and disease severity. Further studies are needed to determine whether NMC are reliable predictive biomarkers of CAP etiology and severity. Disclosures Lilliam Ambroggio, PhD, MPH, Pfizer Inc (Grant/Research Support) Asuncion Mejias, MD, PhD, MsCS, Janssen (Grant/Research Support, Advisor or Review Panel member)Merck (Grant/Research Support, Advisor or Review Panel member)Roche (Advisor or Review Panel member)Sanofi (Advisor or Review Panel member) Octavio Ramilo, MD, Adagio (Consultant)Bill & Melinda Gates Foundation (Grant/Research Support)Janssen (Grant/Research Support)Lilly (Consultant)Merck (Consultant, Grant/Research Support)NIH (Grant/Research Support)Pfizer (Consultant)SANOFI (Board Member)

Wearable Inertial Measurement Unit to Accelerometer-Based Training Monotony and Strain during a Soccer Season: A within-Group Study for Starters and Non-Starters

The purpose of this study was to analyze the intragroup differences in weekly training monotony (TM) and training strain (TS) between starter and non-starter male professional soccer players at accelerometry based variables throughout the periods of a season. TM and TS of different accelerations and decelerations zones for twenty-one players were followed for forty-eight weeks. Regardless of group, players obtained the highest mean TM (starters = 3.3 ± 0.6, non-starters = 2.2 ± 1.1, in arbitrary unit, AU) and TS (starters = 1288.9 ± 265.2, non-starters = 765.4 ± 547.5, AU) scores in the pre-season for accelerations at Zone 1 (<2 m/s2). The results also indicated that both groups exhibited similar TM and TS scores in accelerations at Zones 2 (2 to 4 m/s2) and 3 (>4 m/s2) across the entire season. While the starters showed the highest TM and TS scores at deceleration Zone 1 (<−2 m/s2) in the end-season, the non-starters exhibited the highest scores at the deceleration Zone 1 in pre-season. It seems that in pre-season, coaches applied higher levels of training with greater emphasis on deceleration for non-starters. This tendency was reduced over time for non-starters, while starters presented higher values of deceleration Zone 1. These results highlight the variations in TM and TS across the different periods of a full season according to match starting status among professional soccer players, and the results suggest that non-starter players should receive higher levels of load to compensate for non-participation in matches throughout a soccer season.

Intertheoretic Comparisons of Choice-Worthiness

In this chapter we consider the extent to which different theories are unit-comparable, and what makes them comparable when they are. We consider three arguments for the conclusion that intertheoretic comparisons are always impossible: the appeal to cases argument, the swamping argument, and the arbitrary unit arguments. We argue against all three arguments. We distinguish between structural and non-structural accounts of intertheoretic comparisons. We argue in favour of non-structural accounts: we argue that intertheoretic comparisons are grounded in substantive facts about the theories themselves (rather than merely statistical properties of their choice worthiness function). We discuss a number of possible accounts of intertheoretic comparisons, ultimately arguing in favour of a ‘universal scale’ account.

P4612Elevated pentraxin-3 level is associated with impaired post procedural myocardial perfusion assessed by quantitative blush evaluator in patients with acute STEMI undergoing primary PCI

Background Long Pentraxin-3 (PTX3) has been known as an emerging cardiac biomarker and has potential diagnostic and prognostic value in coronary heart disease. Whether plasma PTX3 level is associated with post procedural myocardial perfusion assessed by quantitative blush evaluator (QuBE) in acute ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI) is unknown. Purpose This study sought to evaluate the association between plasma PTX3 level and post procedural myocardial perfusion assessed by QuBE in patients with acute STEMI undergoing primary PCI. Methods We enrolled 217 patients with acute STEMI who underwent primary PCI (men=191, women=26). Post procedural myocardial perfusion was evaluated using QuBE. PTX3 level was measured at admission by an ELISA method. We used 0.33 ng/mL for PTX3 level as a cut off point for future worse clinical outcome as shown by previous study. Impairment of myocardial perfusion was defined as QuBE <9 arbitrary unit as also shown by previous studies. Results Plasma PTX3 level had an inverse correlation with QuBE score (r=−0.64, p<0.001). Patients in elevated PTX3 group (≥0.33 ng/mL; N=80) had lower median QuBE score compared with lower PTX3 group (<0.33ng/mL; N=137), with QuBE score (8.6 arbitrary unit vs. 15.1 arbitrary unit, P<0.001). Multivariate logistic analysis showed that plasma PTX3 level ≥0.33 ng/mL (OR=7.65, p<0.001) along with Diabetes Mellitus (OR=2.30, p=0.04), and Killip class II-IV (OR=2.57, p=0.04) were independent predictors of impaired myocardial perfusion, as shown by QuBE score <9 arbitrary unit. Analysis between PTX3 and low QuBE score Variables Multivariate OR (95% CI) P value PTX3 ≥0.33 ng/mL 7.65 (3.37–17.36) <0.001 Diabetes Mellitus 2.30 (1.01–5.23) 0.04 Hypertension 1.15 (0.47–2.82) 0.75 Killip class II-IV 2.57 (1.04–6.35) 0.04 IRA LAD 3.79 (1.64–8.78) 0.002 Thrombus grade 4 & 5 3.36 (1.06–11.98) 0.04 Post PPCI TIMI flow <3 5.29 (2.09–13.36) 0.001 PTX3, pentraxin-3; QuBE, quantitative blush evaluator; IRA, infarct related artery. Conclusions Patients with acute STEMI with high plasma PTX3 level were associated with reduced myocardial perfusion after primary PCI shown by low QuBE score. Elevated PTX3 level may be used as a marker for persistent impairment of myocardial perfusion after primary PCI in STEMI

Effects of Submaximal Performances on Critical Speed and Power: Uses of an Arbitrary-Unit Method with Different Protocols

The effects of submaximal performances on critical speed (SCrit) and critical power (PCrit) were studied in 3 protocols: a constant-speed protocol (protocol 1), a constant-time protocol (protocol 2) and a constant-distance protocol (protocol 3). The effects of submaximal performances on SCrit and PCrit were studied with the results of two theoretical maximal exercises multiplied by coefficients lower or equal to 1 (from 0.8 to 1 for protocol 1; from 0.95 to 1 for protocols 2 and 3): coefficient C1 for the shortest exercises and C2 for the longest exercises. Arbitrary units were used for exhaustion times (tlim), speeds (or power-output in cycling) and distances (or work in cycling). The submaximal-performance effects on SCrit and PCrit were computed from two ranges of tlim (1–4 and 1–7). These effects have been compared for a low-endurance athlete (exponent = 0.8 in the power-law model of Kennelly) and a high-endurance athlete (exponent = 0.95). Unexpectedly, the effects of submaximal performances on SCrit and PCrit are lower in protocol 1. For the 3 protocols, the effects of submaximal performances on SCrit, and PCrit, are low in many cases and are lower when the range of tlim is longer. The results of the present theoretical study confirm the possibility of the computation of SCrit and PCrit from several submaximal exercises performed in the same session.