Search

Background Cytokines play a major role in the immune response to viral infections, contributing to viral clearance but also mediating immunopathology following infection. We sought to define and compare systemic cytokine responses in infants hospitalized with COVID-19 versus RSV infection (RSVi). Methods Prospective study of convenience cohort of infants hospitalized with PCR confirmed SARS-CoV-2 or RSVi, as well as pre-pandemic healthy controls (HC). Blood samples were obtained at enrollment and cytokine analysis performed using a 92-cytokine inflammation panel (Olink platform). Statistical analyses were performed in R environment. Results We enrolled 26 infants with COVID-19, 77 with RSVi, and 18 healthy infants as a comparator control group. Oxygen requirement was significantly more frequent in infants with RSVi (p=0.02), while presence of comorbidities was significantly more common in infants with COVID-19 (p=0.01). No statistical differences were identified in terms of length of stay, admission to pediatric intensive care unit, need for mechanical ventilation, and lymphocyte counts (Table 1). Principal component analysis (PCA) revealed clustering of the global cytokine profiles differentiating HC from infants with COVID-19 and RSVi (Figure 1A). Multiple comparison analysis among the three groups yielded 49 significantly different cytokines clustered in three groups. A first cluster that included cytokines such as CCL11, CCL19 and TNFSF12 were lower in both COVID-19 and RSVi compared to HC; a second cluster with CCL8, CXCL8 and CASP8 that were mildly increased in both COVID-19 and RSVi; and a third cluster that included IL6, IL17C and IFN-ɣ were markedly increased in both viral groups compared with HC (ANOVA padj< 0.05) (Figure 1B). Direct comparison between COVID-19 and RSVi (padj< 0.05 and FC >1.5) identified 7 statistically different cytokines. CCL8, CXCL1, CCL20 concentrations were increased in COVID-19, while SIRT2, STAMBP, MMP10 and EIF4EBP1 concentrations were increased in RSVi (Figure 1C-D). Table 1.Demographic and clinical characteristics*Comparisons among RSV, COVID-19 and HC**Comparisons between RSV and COVID-19a 14 out of the 26 patients were tested for coinfectionHC: Healthy control; LOS: length of stay; PICU: pediatric intensive care unit. Comorbidities included prematurity, congenital heart disease, sickle cell disease, overweight, eczema, gastroesophageal reflux. Continuous variables displayed as medians with 25%-75% interquartile ranges (IQ). Mann-Whitney test was used to determine differences between two groups; Kruskal-Wallis test was used to determine differences between three groups. Categorical data expressed as numbers (and percentages) and analyzed by Fisher’s exact test or Chi square test.Figure 1.Cytokines’ concentrations in hospitalized infants with COVID-19 versus RSV infection. A. Principal Component Analysis (PCA) Plot. Each dot represents an individual patient sample, and similar samples are clustered together according to their cytokine profiles. B. Heat map displaying serum cytokine concentrations in healthy controls (HC), COVID-19 and RSVi. Red represents increased concentrations while blue represents decreased concentrations compared with the HC. C. Heat map and D. Bar plots displaying the differences in serum cytokine concentrations between COVID-19 and RSVi. Conclusion Analysis of systemic cytokine profiles identified shared but also distinct cytokine responses in infants with SARS-CoV-2 and RSVi suggesting important differences in the pathogenesis of these viral infections. Disclosures Amy Leber, PhD, BioFire: Advisor/Consultant|BioFire: Grant/Research Support|Biorad: Advisor/Consultant|Cepheid: Grant/Research Support Asuncion Mejias, MD, PhD, MsCS, Janssen: Advisor/Consultant|Janssen: Grant/Research Support|Merck: Advisor/Consultant|Merck: Grant/Research Support|Roche: Advisor/Consultant|Sanofi-Pasteur: Advisor/Consultant|Sanofi-Pasteur: Honoraria Octavio Ramilo, MD, Adagio: Advisor/Consultant|Bill & Melinda Gates Foundation: Grant/Research Support|Janssen: Advisor/Consultant|Janssen: Grant/Research Support|Lilly: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|NIH: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Sanofi: Advisor/Consultant|Sanofi: Honoraria.

Background The factors associated with severe COVID-19 in pediatric patients remain poorly understood. We sought to determine whether mucosal innate immunity cytokines were associated with disease severity in children and adolescents with acute COVID-19. Methods Single-center, prospective study including children and adolescents < 21 years of age hospitalized because of symptomatic COVID-19 from 3/2020 to 1/2021, and age, sex and race matched pre-pandemic (2016-2019) healthy controls. Nasopharyngeal (NP) samples were obtained at enrollment for measurement of SARS-CoV-2 viral loads by rt-PCR and cytokine concentrations using a 92-plex inflammation/antiviral panel (Olink). Disease severity was assessed by the need for supplemental oxygen or PICU admission, and patients classified as severe and non-severe based on these two parameters. Statistical analyses were performed in R studio and Benjamini-Hochberg applied to adjust for multiple comparisons. Results Of the 75 children with acute COVID-19 (median IQR age: 3.4 [0.2-15.3] years), 28 (37%) were classified as severe COVID-19 (19 PICU; 25 supplemental oxygen) and 47 (63%) were non-severe. Children with severe COVID-19 were predominantly male and had an underlying condition more frequently than those with non-severe disease (79% vs 49% respectively; p< 0.01, Table 1). SARS-CoV-2 viral loads were comparable between groups, yet patients with severe COVID-19 had significantly higher concentrations of C-reactive protein (p=0.04), more frequent lymphopenia (p=0.03) and cardiac involvement (p=0.04), and received COVID-19 directed therapies more commonly (p< 0.001). Comparative analyses identified 24 cytokines that were significantly different between children with acute COVID-19 versus 45 healthy controls. Of those, concentrations of IFN-γ (p=0.004), CXCL10 (p=0.01), CXCL11 (p=0.02) and CCL19 (p=0.02) were significantly lower in children with severe versus those with non-severe COVID-19 (Fig 1). Table 1.Demographic and clinical characteristics in children with symptomatic COVID-19*Bolded p-values indicates statistical significance. Abbreviations: N, number. CRP, C-Reactive protein; PICU, pediatric intensive care unit.**Other including the following underlying conditions: prematurity, endocrine conditions, immunocompromising conditions, prematurity, trisomy 21 and complex care. Ł Lymphopenia defined as an ALC of 12 months of age Continuous variables displayed as medians and 25%-75% interquartile ranges (IQR), Mann-Whitney test was used to determine differences between two groups; Kruskal-Wallis & Dunn’s multiple test correction was used to determine differences between three groups (p-values*). Categorical data expressed as numbers and proportions (in parenthesis) and analyzed by Fisher’s exact test or Chi square test. Figure 1.Nasal mucosal concentrations of antiviral/regulatory cytokines in children with symptomatic COVID-19 according to disease severity Conclusion Mucosal concentrations of antiviral/regulatory cytokines were decreased in children with severe COVID-19. These findings suggest that impaired mucosal innate immune responses might favor SARS-CoV-2 disease progression and severity in children. Disclosures Amy Leber, PhD, BioFire: Advisor/Consultant|BioFire: Grant/Research Support|Biorad: Advisor/Consultant|Cepheid: Grant/Research Support Octavio Ramilo, MD, Adagio: Advisor/Consultant|Bill & Melinda Gates Foundation: Grant/Research Support|Janssen: Advisor/Consultant|Janssen: Grant/Research Support|Lilly: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|NIH: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Sanofi: Advisor/Consultant|Sanofi: Honoraria Asuncion Mejias, MD, PhD, MsCS, AstraZeneca: Honoraria|Janssen: Advisor/Consultant|Janssen: Grant/Research Support|Merck: Advisor/Consultant|Merck: Grant/Research Support|Roche: Advisor/Consultant|Sanofi-Pasteur: Advisor/Consultant|Sanofi-Pasteur: Honoraria.

Background RSV is the most frequent etiology of pediatric lower respiratory tract infection. Most children hospitalized for RSV are previously healthy without known risk factors. Children with mild disease managed as outpatients (OP) have higher viral loads than those hospitalized with severe disease. OP children have higher concentrations of the mucosal interferon (IFN), IFNλ2/3, and IP-10, but no differences in IFNλ1. We examined how RSV replication impacts cytokine production kinetics in the nasal mucosa. Methods Primary infant human nasal epithelial (iHNE) cells were collected from nasopharyngeal swabs and cultured on an air-liquid interface. Cultures were infected with 0.1 or 0.001 multiplicity of infection (MOI) of RSV-A, or mock infected. Concentrations of IFN-related (IFNα2, β, γ, λ1, λ2/3, and IP-10) and inflammatory (IL-1β, -6, -12, and TNFα) cytokines secreted to the apical and basolateral surfaces were quantified via immunoassay. Kinetics according to viral inocula were compared by ANOVA with Dunn post-hoc testing of the area under the curve (AUC) for each cytokine. Peak concentrations were compared according to MOI and secretion surface by 2-way ANOVA. Results AUC of IFNs in both surfaces of RSV infected cells were significantly higher than those of mock infected. The 0.1 MOI RSV inoculum resulted in significantly higher AUCs for all IFN cytokines on both surfaces than the 0.001 MOI. Peak IFNλ1 concentrations were higher on the apical than basolateral side; peak IFNλ2/3 concentrations were higher on the basolateral side than apical. AUCs of inflammatory cytokines in RSV infection were significantly higher on the basolateral, but not apical, surfaces than mock; all basolateral inflammatory cytokines were higher in the 0.1 MOI than the 0.001 MOI. Conclusion Higher RSV inoculum induces higher concentrations of IFN-related cytokines on both sides of epithelial cells, and higher concentrations of inflammatory cytokines on the basolateral side. Differential secretion of IFNλ1 and IFNλ2/3 to the apical and basolateral surfaces suggests they may play different roles in immune response during RSV infection. These data support viral replication as an important factor influencing RSV pathogenesis and severity through cytokine production. Disclosures 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)

Background Children with COVID-19 may develop severe disease. In hospitalized adults, detection of plasma SARS-CoV-2 RNAemia ranges from 19% to 42% and has been associated with worse clinical outcomes. A similar association in children remains unexplored. We determined the frequency of SARS-CoV-2 RNAemia in children hospitalized with COVID-19 and evaluated its potential association with severe disease. Methods Single center prospective study that enrolled hospitalized children and adolescents ≤21 years old with COVID-19 from March 2020-April 2021 at Nationwide Children’s Hospital, Columbus, OH. Nasopharyngeal (NP) and blood samples were obtained and SARS-CoV-2 RNA was quantified using a real time PCR assay targeting the N1 gene. Pertinent demographic, clinical, laboratory, and outcome data were evaluated. Results We enrolled a convenience sample of 103 hospitalized children (median age, 9 years; range, 3 days-21 years) who had confirmed SARS-CoV-2 infection and both NP and blood samples obtained (Table 1). Overall, 27 (26%) patients with COVID-19 had SARS-CoV-2 RNAemia. Compared with patients who had undetectable RNAemia, those with SARS-CoV-2 RNAemia had significantly higher nasopharyngeal RNA loads (8.1 vs. 4.9 log10 copies/mL; p=0.0006), fever (78 vs 54%; p=0.02), receipt of supplemental oxygen (37% vs 14%; p=0.02), and treatment with anti-COVID-19 medications (30% vs 12%; p=0.04). In addition, patients with SARS-CoV-2 RNAemia were more likely to require intensive care (40%% vs. 20%, p= 0.04) and had longer hospitalization (2.56 vs 2.15 days; p=0.03). There were no COVID-19 related deaths. Table 1. Demographic, clinical, laboratory and virology characteristics of study patients Conclusion The frequency of SARS-CoV-2 RNAemia in pediatric patients was 26% and its finding was associated with worse clinical in-hospital outcomes, similar to that reported in adults. Testing for SARS-CoV-2 RNAemia in children may help identify those who could benefit from more intensive supportive care as well as antiviral and anti-inflammatory medications. Disclosures 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) 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)

Background The mechanisms associated with COVID-19 in children are not well understood. We sought to define the differences in nasopharyngeal (NP) cytokine profiles according to clinical presentation in children with COVID-19. Methods Single-center, prospective study in 137 children and adolescents < 21 years of age hospitalized with COVID-19, and 35 age, sex and race matched pre-pandemic (2016-2019) healthy controls. Children with COVID-19 were categorized according to their clinical presentation in: COVID-19-symptomatic; COVID-19-screening, and multisystem inflammatory syndrome (MIS-C). NP swabs were obtained within 24 hours of admission to measure SARS-CoV-2 loads by rt-PCR, and a 92-cytokine panel. Unsupervised and supervised analysis adjusted for multiple comparisons were performed. Results From 3/2020 to 1/2021, we enrolled 76 COVID-19-symptomatic children (3.5 [0.2-15.75] years); 45 COVID-19-screening (11.1 [4.2-16.1] years), and 16 MIS-C (11.2 [5.9-14.6] years). Median NP SARS-CoV-2 loads were higher in COVID-19-symptomatic versus screening and MIS-C (6.8 vs 3.5 vs 2.82 log10 copies/mL; p< 0.001). Statistical group comparisons identified 15 cytokines that consistently differed between groups and were clustered in three functional categories: (1) antiviral/regulatory, (2) pro-inflammatory/chemotactic, and (3) a combination of (1) and (2); (Fig 1). All 15 cytokines were higher in COVID-19-symptomatic versus controls (p< 0.05). Similarly, and except for TNF, CCL3, CCL4 and CCL23, which were comparable in COVID-19-symptomatic and screening patients, the remaining cytokines were higher in symptomatic children (p< 0.05). PDL-1 (p=0.01) and CCL3 (p=0.03) were the only cytokines significantly decreased in children with MIS-C versus symptomatic COVID-19 children. The 15 cytokines identified by multiple comparisons were correlated using Person’s in R software. Red reflects a positive correlation and blue a negative correlation with the intensity of the color indicating the strength of the association. Conclusion Children with symptomatic COVID-19 demonstrated higher viral loads and greater mucosal cytokines concentrations than those identified via screening, whereas in MIS-C concentrations of regulatory cytokines were decreased. Simultaneous evaluation of viral loads and mucosal immune responses using non-invasive sampling could aid with the stratification of children and adolescents with COVID-19 in the clinical setting. Disclosures 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) 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).

Background The burden associated with RSV infection is substantial. Although RSV initially infects the upper respiratory tract, there is limited information of the mucosal concentrations of antibodies (Abs) directed to RSV specific proteins and whether patient’s age and disease severity influence production of mucosal Abs. Methods From 2017 to2019 we enrolled previously healthy children < 2 years of age hospitalized with RSV infection and obtained acute and convalescent (day; D30) nasopharyngeal (NP) samples to measure preF and postF specific IgG and IgA Abs by ELISA. Demographic and clinical data were collected and analyzed according to Abs responses. Results We enrolled 77 children (median [IQR] age: 2.8 [1.5-5.2] months; 49 % females) within the first 24 hours of hospitalization. Of those 25 (33%) patients required PICU care. A significant increase in convalescent IgG preF Abs titers was detected in 62 (81%) children, while IgA preF titers significantly increased in all but one child on D30. The magnitude of the increase was 56-fold higher for preF IgA versus preF IgG (p< 0.0001). PostF IgG and IgA titers were also increased on D30 but at significant lower levels. Infants < 3 months of age compared with those >3-24 months had significantly higher baseline preF and postF IgG Abs titers (p < 0.001) but not IgA antibodies. D30 preF and post F IgG titers were higher in children > 6 months of age (p < 0.0001) but only preF titers fold change significantly correlated with age (r=0.4, p< 0.0001). These correlations were not identified with IgA preF antibodies. There were no statistical differences in antibody titers at baseline and on D30 according to breastfeeding, and disease severity as defined by the need for PICU care. Conclusion Children hospitalized with RSV infection demonstrated significantly increased titers of mucosal preF and post F IgG and IgA specific Abs in convalescent samples. Baseline IgG Abs where higher in younger infants, which likely reflects maternally acquired antibodies. Age significantly correlated with Abs production, suggesting a more robust immune response in older children. Disclosures Mark E. Peeples, PhD, Janssen (Research Grant or Support)Pfizer (Research Grant or Support) 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) 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)

Background Neonatal HSV infection is associated with significant morbidity and mortality. Neonates with HSV infection can present with skin, eye, and mouth (SEM), central nervous system disease (CNS), and disseminated disease (DIS). We hypothesize that host immune responses may contribute to differences in disease presentation and outcomes. To address this knowledge gap, we analyzed host transcriptional immune profiles of neonates with HSV infection. Methods Infants < 6 weeks of age (24 (86%) < 4 weeks; 4 (14%) 4-6 weeks old) with neonatal HSV, and healthy infant controls (HC) were enrolled at Children’s Medical Center (Dallas, TX), and Nationwide Children’s Hospital (Columbus, OH) from 2007-2018. Whole blood samples were analyzed by RNA-seq. Modular analyses were performed to identify the immune pathways that were activated or suppressed according to each HSV disease category. Results Of the 28 infants with HSV infection, 9 had SEM (median [IQR] age: 14 [14-28] days), 10 CNS (age: 18 [15-29] days), and 9 DIS (age: 10 [7-10] days). Three infants with DIS died within 5 days of diagnosis. Statistical group comparisons between 13 HC and 18 infants with HSV disease (training set) identified 1,322 differentially expressed genes (neonatal HSV biosignature). This biosignature was validated in the remaining 10 infants with HSV disease (test set), and was characterized by significant overexpression of interferon (INF), inflammation, neutrophils, and monocyte genes and under-expression of T-cell genes. Further analysis according to HSV disease category confirmed overexpression of neutrophil and inflammation genes in infants with SEM, CNS and DIS (Fig 1). On the other hand, overexpression of INF and plasma cell genes, and further suppression of monocytes, cytotoxic/NK cells, and T-cell genes were only evident in children with DIS. Fig 1: Modular immune pathways according to HSV disease category Modules are groups of genes that shared a similar function. Each dot represents a transcriptional module with red indicating overexpression and blue underexpression in relation to healthy controls. The number and color intensity on the dot indicate the percentage of differentially expressed transcripts within a module. SEM: skin, eye mouth; CNS: central nervous system; DIS: disseminated HSV disease. Conclusion Transcriptional profiles of infants with HSV infection exhibited marked activation of the innate immune response irrespective of disease classification. Children with DIS showed more profound dysregulation and suppression of cellular immune responses. Transcriptional profiling may aid unravel mechanisms associated with clinical outcomes in neonatal HSV and inform future therapeutic and preventive strategies. Disclosures 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) 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)

Background Despite the high burden associated with RSV infection in young children the factors that determine disease severity are not well understood. The objective of this study was to assess the association of mucosal cytokine profiles, RSV loads (VL) and RSV disease severity. Methods Single-center, prospective study in previously healthy infants with mild (outpatients; OP), moderate (inpatient-IP; ward) or severe (IP-PICU) RSV infection. Mid-turbinate swabs were obtained to measure VL by PCR, and cytokine concentrations (conc.) using a 13-plex panel that included type I (IFN-α2), II (IFN-γ), and III (IFN-λ2/λ3) interferons (IFN), and inflammatory cytokines. Multivariable analyses were performed to identify factors predictive of disease severity. Results From 2014 to 2019 we enrolled 219 infants: 78 with mild RSV infection (OP; median [IQR] age, 6 [3.4–10.5] mo.), 101 with moderate disease (3.5 [1.3–8.3] mo.), and 40 with severe disease (2.3 [1.5–5.7] mo.). Duration of symptoms at enrollment was 4 (3–5) days and comparable between OP and IP, yet RSV VL in OP were significantly higher than in IP (8.1 [7.4–8.6] vs 7.4 [6.4–8.1] log10 copies/mL; p< 0.01) with no differences between ward and PICU infants. Median conc. of IFN-α2, IFN-γ, and IFN-λ2/λ3 were significantly higher in OP vs IP irrespective of hospitalization unit (Table 1). IP-10 conc. were also higher in OP and in ward patients vs PICU patients (p< 0.0001) and were independently associated with lower odds of supplemental O2 needs (OR, 95% CI: 0.4 [0.22–0.69]; p< 0.01) and PICU admission (0.4 [0.23–0.67]; p=0.001). In addition, higher IFN-λ2/λ3 conc. were nearly associated with lower odds of prolonged O2 use (OR: 0.35 [0.11–1.07]; p=0.07), and prolonged hospitalization (OR: 0.42 [0.16–1.03]; p=0.06). Conclusion Infants with mild RSV infection had higher RSV VL and higher conc. of IP-10 and type-I, III IFN than those hospitalized with severe disease. These findings suggest that IP-10 and mucosal IFNs are associated with protection against severe RSV disease and could be used as biomarkers for patient stratification in the clinical setting. Disclosures Octavio Ramilo, MD, Bill & Melinda Gates Foundation (Grant/Research Support)Janssen (Grant/Research Support, Advisor or Review Panel member)Medimmune (Grant/Research Support)Merck (Advisor or Review Panel member)NIH/NIAID (Grant/Research Support)Pfizer (Consultant, Advisor or Review Panel member)Sanofi/Medimmune (Consultant, Advisor or Review Panel member) Asuncion Mejias, MD, PhD, MsCS, Janssen (Grant/Research Support, Advisor or Review Panel member)Merck (Advisor or Review Panel member)Roche (Advisor or Review Panel member)

Background Differences in clinical presentation and viral loads according to age in young children with RSV, and their correlation with disease severity are poorly defined. The aim of this study was to define age-dependent the differences in demographic, clinical factors and viral loads between children < 2 years of age with mild RSV infection evaluated as outpatients versus those hospitalized with severe RSV infection. Figure 1. Sign and Symptoms according to disease severity and age in infants with RSV infection. Most relevant signs and symptoms were stratified in outpatients (orange) vs inpatients (blue) by age in (A) < 3 months, (B) between 3 and 6 months, and (C) > 6 to 24 months of age. The Y axis represents the signs and symptoms in the two disease severity groups and the X axis the frequency of that specific symptom (%). Numbers next to bars represent the exact number of patients with that specific sign/symptom. Comparisons by Fisher exact test. Symbol (*) indicate significant 2-sided p values Figure 2. Viral load differences according to age in infants with RSV infection. The Y axis represents RSV loads in log10 copies/mL and the X axis differences in viral loads in outpatients (orange) and inpatients (blue) in the three age groups. Comparisons by Mann Whitney test. Methods Previously healthy children < 2 years old with mild (outpatients) and severe (inpatients) RSV infection were enrolled and nasopharyngeal swabs were obtained for RSV typing and quantitation by real-time PCR. Patients were stratified by age (0-< 3, 3-6, and >6-24 months) and multivariable analyses were performed to identify clinical and viral factors associated with severe disease. Results From 2014-2018 we enrolled 534 children with RSV infection: 130 outpatients and 404 inpatients. Median duration of illness was 4 days for both groups, yet viral loads were higher in outpatients than inpatient in the three age groups (Fig 1). Wheezing was more frequent in outpatients of older age (>3 months) than in inpatients (p< 0.01), while fever was more common in inpatients that outpatients (p< 0.01) and increased with age (Fig 2). Adjusted analyses confirmed that increased work of breathing and fever were consistently associated with hospitalization irrespective of age, while wheezing in infants >3 months, and higher RSV loads in children >6-24 months were independently associated with reduced disease severity. Conclusion Age had a significant impact defining the interactions among viral loads, specific clinical manifestations and disease severity in children with RSV infection. These observations highlight the importance of patient stratification when evaluating interventions against RSV. Disclosures Octavio Ramilo, MD, Bill & Melinda Gates Foundation (Grant/Research Support)Janssen (Grant/Research Support, Advisor or Review Panel member)Medimmune (Grant/Research Support)Merck (Advisor or Review Panel member)NIH/NIAID (Grant/Research Support)Pfizer (Consultant, Advisor or Review Panel member)Sanofi/Medimmune (Consultant, Advisor or Review Panel member) Asuncion Mejias, MD, PhD, MsCS, Janssen (Grant/Research Support, Advisor or Review Panel member)Merck (Advisor or Review Panel member)Roche (Advisor or Review Panel member)

Background The management approach to febrile infants remain challenging. Despite new advances in rapid diagnostic testing, febrile infants with a viral infection could receive prolonged antimicrobial treatment due to concerns for co-existing serious bacterial infection (SBI). We sought to decrease the duration of antibiotic treatment in febrile infants less than 8 weeks of age hospitalized on inpatient infectious disease service following sepsis evaluation, who have enterovirus, parechovirus, or respiratory viruses detected, from average 30 hours to 24 hours and sustain for six months. Figure 1. Antibiotic Treatment Duration of Infants Underfoing Evaluation for Sepsis Figure 2. Length of Stay in Infants Underfoing Sepsis Evaluation Methods A new management guideline that defined “low-risk” infants, as well as inclusion and exclusion criteria, was created to monitor the accurate duration of parenteral treatment and length of hospitalization. Respiratory viruses were detected by a multiplex PCR assay. We created a QlikSense App for further clinical characterization of patients and follow-up. This management guideline was adapted as a quality improvement division initiative. Control charts were used to assess the impact of the interventions. Figure 3. Readmissions in Infants Underfoing Sepsis Evaluation Results The management guideline was developed and implemented by pediatric infectious disease faculty. Febrile infants < 8 weeks of age were included if they had both documented viral infections and sepsis evaluation. 178 infants were admitted with fevers in 2018 and 148 infants were admitted in 2019. The mean inpatient antibiotic treatment duration decreased from 27.7 hours in 2018 to 24.9 hours in 2019 (P > 0.05) (Figure 1). There was no significant difference in length of hospitalization or 30-day readmission rates (Figure 2 and 3). There was no reported readmission for SBI. Conclusion Antibiotic treatment could be discontinued in clinically stable infants with a documented viral infection after 24 hours of negative blood, CSF, and urine bacterial culture incubation so as not to receive unnecessary prolonged inpatient treatment that may increase side effects. In addition to possible decreased treatment side effects our protocol led to decreased patient care costs with no documented changes in readmission rates. Disclosures Octavio Ramilo, MD, Bill & Melinda Gates Foundation (Grant/Research Support)Janssen (Grant/Research Support, Advisor or Review Panel member)Medimmune (Grant/Research Support)Merck (Advisor or Review Panel member)NIH/NIAID (Grant/Research Support)Pfizer (Consultant, Advisor or Review Panel member)Sanofi/Medimmune (Consultant, Advisor or Review Panel member)

Background Respiratory syncytial virus (RSV) is a leading cause of hospitalization for infants. Several vaccine strategies for RSV are being developed. Among those, live attenuated vaccine (LAV) represent an attractive alternative for young children as they mimic natural infection and induce protective immunity without causing enhanced disease. However, markers of reactogenicity and/or innate immune protection in the respiratory mucosa are not well defined. The objective of this study was to assess mucosal markers, including innate immune cytokine profiles and RSV loads (VL), and their potential association with protection from severe disease in infants with natural RSV infection. Methods Single-center, prospective study in previously healthy infants with mild (outpatients; OP) and severe (inpatients; IP) RSV infection, and aged-matched healthy controls (HC). Nasopharyngeal (NP) swabs were obtained at enrollment in all subjects to measure VL by PCR, and cytokine concentrations (conc.) using a 13-plex panel that included: Type-I, type-II, and type-III IFN, and inflammatory cytokines. Cytokine conc. and VL were compared according to hospitalization status (OP vs. IP). Results From 2014 to 2017 we enrolled 105 infants: 48 with severe RSV infection (IP; median IQR age: 2.3 [1.1–5.5] months), 36 with mild disease (OP; 6.4 [3.8–9.3] months), and 20 HC (4.9 [2.8–7.2] months). The median duration of symptoms at enrollment was 4 days for both IP and OP. IL-1β, TNF-α, and IL-10 were detected more frequently in RSV infants than in HC (39% vs. 5%, respectively), but median conc. in IP and OP were not different (P > 0.05). Detection and/or conc. of IFN-β, IP-10, IFN-γ and type III IFN (IFN-λ1, IFN-λ2/3) were significantly greater in OP vs. IP, who also had higher VL (Table 1). In addition, IP-10 (r = 0.6; P < 0.001) and IFN-λ conc. (r = 0.55, P < 0.0001) significantly correlated with RSV VL. Conclusion Infants with mild RSV infection had higher VL and a more robust type-I, -II, and -III IFN responses than those hospitalized with severe disease. These findings suggest that increase conc. of mucosal IFNs are associated with protection against severe RSV infection, and could potentially be used as surrogate markers to help the development of LAV for RSV infection in young children. Disclosures Octavio Ramilo, MD, Bill & Melinda Gates Foundation: Research Grant; Janssen: Research Grant; Merck: Advisory Board; NIH: Research Grant; Ohio Children’s Hospital Association (OCHA): Research Grant; Pfizer: Advisory Board, Consultant, Lectures; Sanofi/Medimmune: Advisory Board.

Background Worldwide, pneumonia is the leading cause of death in children Methods We conducted a prospective, multicenter, observational study of CAP among previously healthy children aged 2 months through 18 years in six children’s hospitals in Ohio. Blood, pleural fluid, and nasopharyngeal swabs were collected for pathogen detection by culture and/or molecular diagnostics. Patient clinical management including antibiotic therapy and respiratory support, followed the standard of care at each study site. Follow-up information regarding clinical outcomes was collected via a survey 6–8 weeks after enrollment. Results We enrolled 441 children (n = 380, 86% hospitalized) with CAP from 2015 to 2018. Median age was 5 years (IQR: 2.1–8.9y). Intensive care and respiratory support were required for 15% and 49% of children, respectively. Consolidation and pleural effusion were identified in 26% and 21%, respectively. Among hospitalized children, 99% received antibiotics during hospitalization, and 91% continued antibiotic treatment at discharge. There were no children with any kind of sequelae or deaths from CAP, but 4.4% were readmitted within 30 days after discharge. Pathogens were identified in 64% patients; including pyogenic bacteria in 4%, atypical bacteria in 9%, and viruses in 56%. A total of 18 (4%) children had both bacterial (9 pyogenic and 9 mycoplasma) and viral pathogens. Among children with a virus detected (n = 245), 17% had more than one virus. The most commonly detected bacteria were M. pneumoniae (n = 39) and S. pneumoniae (n = 10). Rhinovirus was the most common virus detected (RV; n = 81, 28%), followed by respiratory syncytial virus (RSV; n = 75, 26%). Conclusion In this multicenter cohort, the most commonly detected viruses in children with CAP were RV and RSV, and M. pneumoniae and S. pneumoniae among bacteria. Clinical outcomes in children with CAP were overall good, but there was a high burden of hospitalization and antibiotic use. Disclosures Octavio Ramilo, MD, Bill & Melinda Gates Foundation: Research Grant; Janssen: Research Grant; Merck: Advisory Board; NIH: Research Grant; Ohio Children’s Hospital Association (OCHA): Research Grant; Pfizer: Advisory Board, Consultant, Lectures; Sanofi/Medimmune: Advisory Board.

Background Previous studies suggest that RSV increases NP bacterial colonization and may facilitate infection. However, the role of NP colonization with potentially pathogenic bacteria (PPB) in the pathogenesis of RSV bronchiolitis is not well understood. We sought to determine the frequency, type, and density of NP PPB detection in infants with RSV infection compared with healthy controls (HC), and its association with clinical outcomes. Methods Single-center, prospective study of previously healthy infants with RSV infection and age-matched HC. Inpatients (IP) were enrolled within 24 hours of hospitalization, outpatients (OP) at the ED or primary clinics and HC at well-child visits. RSV infection and the following PPB: [S. pneumoniae, M. catarrhalis, H. influenzae, and S. aureus] were detected and quantified by PCR. We compared demographic, clinical characteristics, and outcomes of care according to NP PPB detection. Results From 2010 to 2018, we enrolled 815 infants: 664 with RSV infection [IP, 560; OP, 104] and 151 HC. RSV+ OP (6.1 [3.7–10.7] months) and HC (6.9 [3.8–10.8] months) were older than IP (2.5 [1.4–5.4] months; P < 0.001). Identification of ≥1 PPB was 89% in RSV+ infants [IP, 88%; OP, 90%] versus 63% of HC (P < 0.0001). While H. influenzae or >1 PPB detection was higher in RSV infection (P < 0.001), S. aureus detection predominated in HC (P < 0.05; Figure 1). Frequency of S. pneumoniae detection was comparable between groups; however, S. pneumoniae loads were one log higher in RSV+ infants versus HC (P = 0.001) adjusted for antibiotic use. Differences in colonization rates remained different in RSV+ infants versus HC across age ranges (6–12, and >12–24 months; Figure 2). Last, RSV patients (both IP and OP) with S. pneumoniae or H. influenzae detection had fever more frequently (70%–74% vs. 25%–47%; P < 0.0001), higher clinical disease severity scores (P = 0.01), and higher blood neutrophil counts (34%–36% vs. 16%–19%; P < 0.001), versus those with M. catarrhalis, S. aureus detection or PCR negative. In addition, NP detection of H. influenzae in RSV children was associated with higher frequency of atelectasis/consolidation by chest X-ray (P < 0.005). Conclusion These data suggest that NP colonization with PPB is high in infants with RSV infection independent of age, and that specific bacteria, namely S. pneumoniae and H. influenzae, are associated with enhanced clinical disease severity. Disclosures A. Leber, Nationwide Children’s Hospital: Research Contractor, Research support. O. Ramilo, Janssen Scientific Affairs, LLC: Consultant, Consulting fee. A. Mejias, Janssen: Grant Investigator and Scientific Advisor, Consulting fee and Research grant. Abbvie: CME talks, Speaker honorarium.

Background Studies suggest that RSV infection early in life is associated with the development of recurrent wheezing, yet, information on large population-based studies among US full-term healthy infants is incomplete. The objective of this study was to evaluate the risk of developing post-RSV recurrent wheezing/asthma during childhood among full-term infants in a US commercially insured population. Methods Retrospective, observational study used data from Truven MarketScan Commercial Claims and Encounters Database (January 1, 2000–December 31, 2016) to identify full-term infants with and without a RSV diagnosis in the first year of life (RSV and non-RSV cohorts respectively). Infants were excluded if they had any of the following: prematurity (

Background While 10% of the population may report a penicillin (PCN) allergy, it has been shown that 90% of these patients are not allergic and may still be able to take PCN safely. Inaccurate reporting of a PCN allergy may lead to prescription of other non-B-lactam or broader spectrum antibiotics. Inpatients with reported antibiotic allergy status have been shown to have inappropriate antibiotic prescribing, increase microbiologic resistance, and suboptimal patient outcomes. Our goal was to evaluate antibiotic prescribing patterns for children with CAP in the setting of reported antibiotic allergy. Methods The Children’s Hospital’s Initiative for Research in Pneumonia (CHIRP) study enrolled inpatient and outpatient children ≥2 months to 18 years of age with a diagnosis of CAP from six participating sites. Demographic data, allergy status, antimicrobial therapy, and clinical outcomes were collected. Overall prevalence of reported antibiotic allergy and alternative therapy used in setting of reported allergy were analyzed. Results A total of 470 subjects were included, enrolled from October 2015 to December 2017. The mean age was 6.3 years (range: 3 months to 18.9 years), 45% were females. Sixty-three (13.4%) subjects self-reported one or more antibiotic allergies. Twenty-seven subjects reported amoxicillin (AMOX) allergy, nine with PCN allergy, nine with amox/clavulanate (AMOX/CLAV) allergy, and 11 with ampicillin (AMP) or ampicillin/sulbactam allergy. Cephalosporin allergy was reported in seven subjects. Of the 47 subjects who reported AMOX or AMP allergy, 37 (79%) were treated with ceftriaxone, a broad-spectrum agent. In the 47 subjects with reported AMOX or AMP allergy, five (10.6%) were prescribed AMOX at discharge. Of the three subjects with reported levofloxacin allergy, two were treated with levofloxacin during hospitalization for CAP as well as at the time of discharge. Conclusion Most subjects with reported AMOX allergy were treated with alternative and broader-spectrum antibiotics. In our cohort, 10.6% still received the antibiotic despite the allergy labeling. Better confirmation of allergy history to hone appropriate antimicrobial therapy appears to be indicated. Disclosures D. Cohen, Nationwide Children’s Hospital: Research Contractor, Research support. A. Mejias, Janssen: Grant Investigator and Scientific Advisor, Consulting fee and Research grant. Abbvie: CME talks, Speaker honorarium. O. Ramilo, Janssen Scientific Affairs, LLC: Consultant, Consulting fee. Sanofi: Scientific Advisor, Consulting fee. Merck: Scientific Advisor, Consulting fee and Speaker honorarium. Janssen: Grant Investigator and Scientific Advisor, Consulting fee, Grant recipient and Speaker honorarium. Pfizer: Consultant, Consulting fee and Speaker honorarium.

Background RSV remains a leading cause for hospitalization of infants. The mechanisms associated with the ability of RSV to suppress the induction of an adequate immune response are not well understood and represent a challenge for vaccine development. Myeloid-derived-suppressor cells (MDSCs) have been shown to suppress CD8+ T cells in patients with malignancies. These immature myeloid cells are divided into three groups: granulocytic, monocytic, and undifferentiated. Of those, monocytic MDSCs (M-MDSCs) are considered to be key regulators of inflammatory responses during acute infections. Their potential role in the immunopathogenesis of RSV infection in infants is yet to be defined. Methods Single-center, prospective cohort study in previously healthy infants hospitalized with severe RSV lower respiratory tract infection (LRTI) and age-matched healthy controls (HC). Nasopharyngeal swabs for RSV detection and blood samples for cell immunophenotyping were analyzed at enrollment (D1), 1-month (D30), and 6-months (D180) follow-up visits. Disease severity was assessed using a clinical disease severity score (CDSS), duration of supplemental O2, and duration of hospitalization. Results We enrolled 39 infants with RSV LRTI (median [IQR] age: 3.3 [1.5–5.2] months) and 5 HC (5.9 [4.5–7.2] months). Infants with RSV infection demonstrated an expansion of M-MDSCs during the acute infection (D1) that resolved to numbers comparable to those in HC at follow-up visits (Figure 1A). In addition, numbers of CD8+ T cells were significantly reduced during the acute infection (D1) in RSV-infected infants, but also returned to the HC baseline on D30 and D180 (Figure 1B). Finally, the increase in M-MDSCs numbers and decrease in CD8+ T-cell numbers were associated with worse clinical outcomes as defined by duration of supplemental oxygen (>1 day), hospitalization (>48 hours), and clinical disease severity score (CDSS, > 9) (Figure 2). Conclusion These findings suggest that an expansion of M-MDSCs may play a role in T-cell suppression in children with severe RSV disease. As new vaccines are being developed, it is critical to elucidate the immune suppressive mechanisms associated with RSV infection. Disclosures Octavio Ramilo, MD, Bill & Melinda Gates Foundation: Research Grant; Janssen: Research Grant; Merck: Advisory Board; NIH: Research Grant; Ohio Children’s Hospital Association (OCHA): Research Grant; Pfizer: Advisory Board, Consultant, Lectures; Sanofi/Medimmune: Advisory Board.

Background Almost all children are infected with RSV by 2 yrs of age, yet

Background Macrolide-resistant Mycoplasma pneumoniae (MRMp) has emerged in the last 2 decades, with rates as high as 93% in Asia. Rates in the United Stated vary from 3.5 to 13.2%. By sequencing we identified our local resistance rate of 1.8% (9/477) in isolates collected from October 2015 to December 2017. Previous reports described increased morbidity in patients with MRMp. We evaluated the clinical characteristics of children infected with MRMp in Central Ohio. Methods Of the 9 MRMp isolates identified, clinical data were available in 7 cases. We performed a case–control (1:3) analysis, where Mp patients were matched by month and year of presentation. Retrospective analysis of electronic health records (HER) was performed to identify clinical and treatment characteristics. Continuous variables are shown as medians and inter-quartile ranges (IQR), and categorical variables as percentages. For comparisons T, Mann–Whitney U, and Fisher’s exact tests were used as appropriate. Results Both groups had similar demographics with no differences in age and gender. Median age (IQR) was 8.5 years (6–17) for the MRMp and 8 (IQR 3.5–11.5) for the Macrolide-susceptible Mp (MSMp). Duration of symptoms at presentation was similar, median (IQR) of 11 (4–14) days for MRMp, and 8 (6.25–13.25) days for MSMp (P = 0.7). All patients with MRMp had fever compared with 17 (81%) of the MSMp (P = 0.07). Tmax was similar in both groups (P = 0.11). All patients (100%) had cough. There were no differences in the frequency of oxygen requirement, fatigue, shortness of breath, sore throat, nasal congestion, rash, headache and chest radiographic findings. There were similar rates of hospitalization with 4 (57%) in the MRMp and 8 (38%) in the MSMp (P = 0.42). Among hospitalized children, there were no differences in duration hospitalization, median (IQR) 6 (1.25–21.25) days for MRMp and 2 (1–2.75) for MSMp (P = 0.31). None required invasive ventilation. One MRMp patient had encephalitis; this was the only patient requiring intensive care compared with none MSMp (P = 0.25). All patients were initially treated with azithromycin, but 2 (12%) of the MRMp were switched to levofloxacin (P = 0.06). Conclusion We did not identify significant differences in clinical characteristics between patients with MRMp and MSMp. This could be related to our low local rate of MRMp. Disclosures O. Ramilo, Janssen Scientific Affairs, LLC: Consultant, Consulting fee. Sanofi: Scientific Advisor, Consulting fee. Merck: Scientific Advisor, Consulting fee and Speaker honorarium. Janssen: Grant Investigator and Scientific Advisor, Consulting fee, Grant recipient and Speaker honorarium. Pfizer: Consultant, Consulting fee and Speaker honorarium. A. Leber, Nationwide Children’s Hospital: Research Contractor, Research support.

Background HPeV have been associated with severe disease in young infants. Of the 17 genotypes described, HPeV 1 and 3 have been the most frequently reported. The epidemiology and clinical features associated with different genotypes have not been well defined. We analyzed the prevalence, genotypes, and clinical manifestations and outcomes of HPeV in infants ≤ 60 days evaluated at Nationwide Children’s Hospital, Columbus, Ohio. Methods We retrospectively reviewed EMRs of all infants ≤ 60 days undergoing sepsis evaluation with a positive HPeV PCR from any site between July 2013 and September 2016. All available HPeV CSF, blood, and superficial site specimens were typed by PCR or Sanger sequencing (types assigned per GenBank®). Results Of 1,265 patients tested, 131 (10%) were positive for HPeV in at least one site, of which 100 had available isolates for genotyping. Median age was 30 days (IQR 19–39), 55% were male. HPeV3 was identified in 87 (87%), HPeV4 in 6, HPeV1 in 5, and HPeV5 and 6 were identified in one infant each. For comparisons we grouped types 1, 4, 5 and 6 into HPeV0 (n = 13). The circulation of HPeV peaked in the months of July to October independent of the type. However, while HPeV0 were identified only in second half of the year, HPeV3 was detected year round. HPeV3 patients had higher temperatures (P < 0.05). There were no significant differences between HPeV3 vs. HPeV0 in age, gender, presenting symptoms, length of stay, PICU admission and CBC. ALT values were higher in HPeV0 patients (P < 0.01). CSF indices were also similar in both groups. Of the positive CSF isolates for HPeV, 43% had no pleocytosis; all CSF isolates typed were HPeV3. HPeV4 was found in blood and superficial sites. HPeV1, 5 and 6 were only found in superficial sites and more commonly with coinfections (enterovirus [EV], rhinovirus, group B streptococcus). There were 4 PICU admissions, 3 of them had HPeV3 and 1 had HPeV1 (patient also had Rhinovirus/EV bronchiolitis). All patients recovered at the time of discharge. Conclusion HPeV was commonly identified in infants ≤ 60 days undergoing sepsis evaluation. HPeV3 was the most common type in this age group. HPeV4 also caused viremia, while other infrequent types were identified with coinfections. Disclosures O. Ramilo, Abbvie: Board Member, Consulting fee; Regeneron: Board Member, Consulting fee; Janssen: Board Member and Investigator, Consulting fee and Research grant; NIH: Grant Investigator, Research grant; A. Leber, BioFIre Diagnostics: Research Contractor and Scientific Advisor, Research support, Speaker honorarium and Travel expenses

Background All infants under two months of age evaluated for fever or sepsis undergo routine work up at Nationwide Children’s Hospital that includes blood, CSF, and mucosal site PCRs for enteroviruses (EV). We sought to determine the local EV prevalence, clinical characteristics and viral correlates of disease severity in this large population. Methods EMRs of all infants 4–60 days of age evaluated for fever or sepsis from January 2015 to September 2016 were reviewed. An in-house developed real-time PCR was used for EV detection. We analyzed cycle threshold values for positive samples. Results Of the 713 patients tested, 151 (21%) patients were positive for EV in at least one site. Majority of the patients (76%) presented between the months of June and October. Median age was 24 days (IQR 16–37). Median length of stay (LOS) was 40.82 hours (IQR 33.4–47.5). 122 (81%) had fever and 27 (18%) had a rash on admission. Median duration of antibiotic treatment was 2 days (IQR 1.5–2) and median hospital charges were 13,169 USD. CBC values and transaminases were normal. 75 (49%) patients had EV PCR positive in CSF, 120 (79%) in superficial sites, and 109 (72%) in blood and 51 (34%) patients had positive EV PCR in all three sites. 5 patients were admitted to PICU (3.3%), of which 2 had EV detected in CSF. Two patients required pressor support and 3 had seizures. All patients recovered and had no complications at discharge. Among CSF positive patients, median CSF WBC count was 50 (IQR 5–360 cells/µl). Median PCR cycle threshold (Ct) values were: 35.88 (IQR 34.1–37.5) for CSF, 32.54 (IQR 30–36.42) for blood, and 34.58 (31.96–37.36) for superficial sites. CSF and blood Ct values in PICU patients were not significantly different. Ct values in CSF or blood had no significant correlation with length of stay. 55 patients (36%) had coinfections – 53 viral (parechovirus, parainfluenza and rhinovirus/EV [these cannot be distinguished by testing method]), and 2 bacterial (group B Streptococcus and coagulase negative staphylococcus bacteremia). Conclusion EV was commonly identified in infants undergoing sepsis evaluation. Almost half of the patients had EV meningitis. Although, there were no serious complications, 3% of patients required PICU admission. Bacterial coinfection rates were low. Disclosures O. Ramilo, Abbvie: Board Member, Consulting fee; Regeneron: Board Member, Consulting fee; Janssen: Board Member and Investigator, Consulting fee and Research grant; NIH: Grant Investigator, Research grant; A. Leber, BioFIre Diagnostics: Research Contractor and Scientific Advisor, Research support, Speaker honorarium and Travel expenses

Background RSV is the leading cause of hospitalization for bronchiolitis in infants and young children worldwide. Second-hand smoke (SHS) exposure has been associated with increased morbidity in children with respiratory infections. The objectives of this study were to explore the association between SHS measured by hair nicotine and disease severity in infants with RSV infection, and to define its impact on the blood transcriptional immune profiles. Methods Single-center, prospective study of previously healthy infants presenting to the Emergency Department with RSV bronchiolitis with and without SHS exposure assessed by hair nicotine levels. Exclusion criteria included: prematurity; chronic medical conditions, and insufficient hair. Clinical outcomes were assessed using a clinical disease severity score (CDSS; ranging from 0 to 15) and care provided (hospitalization and intensive care). Blood samples from patients and healthy controls were obtained at enrollment for gene expression profiling, and differences in profiles stratified by SHS exposure. Results A total of 70 infants with RSV were enrolled (median age 2.7 months; 44 (62.8%) males; 44 (62.8%) white). Hair nicotine was detected in 45 (64.2%) infants with RSV while 25 RSV+ infants had undetectable hair nicotine levels. Demographic variables were not significantly different between SHS exposed and nonexposed infants. Median nicotine concentrations in infants with severe (CDSS >10) vs. mild RSV disease (CDSS < 5) were 5.3 and 2.1ng/mg (P = 0.49). In addition, blood transcriptional profiles in RSV infants exposed to SHS vs. nonexposed, were characterized by significantly greater overexpression of genes related to inflammation, apoptosis and cell death, and greater suppression of T and B cell-related genes (Figure 1). Conclusion In otherwise healthy infants with RSV infection exposure to SHS was associated with greater inflammation and blunted T and B cell responses. Although not statistically significant, hair nicotine levels were higher in patients with more severe RSV bronchiolitis. Disclosures O. Ramilo, Abbvie: Board Member, Consulting fee; Regeneron: Board Member, Consulting fee; Janssen: Board Member and Investigator, Consulting fee and Research grant; NIH: Grant Investigator, Research grant; A. Mejias, Janssen: Investigator and Scientific Advisor, Consulting fee and Research support; Abbvie: Consultant and Scientific Advisor, Speaker honorarium; Novartis: CME lecture, Speaker honorarium; NIH: Investigator, Research grant

Background Mycoplasma pneumoniae(Mp) is one of the most common causes of LRTI in school aged children, with estimates of up to 20% of cases of community-acquired pneumonia (CAP). Macrolides are the drug of choice for treating Mp infections, but in the last 2 decades there has been emergence of resistance worldwide. Reported rates in USA vary from 3.5 up to 10.8%, but rates in Ohio are unknown. Currently there is no well-established, standardized method for detecting macrolide resistance and antibiotic treatment is empiric because of these limitations. Our goal was to determine the frequency of macrolide resistance in children with Mp respiratory infections in central Ohio. Methods A convenience sample of Mp positive PCR identified by our laboratory-developed assay, obtained from both inpatient and outpatient settings, were selected. These were then cultured using Remel’s SP4 glucose broth and then incubated at 35°C until isolates grew, or for a maximum of 4 weeks. All samples that yield positive cultures were then sequenced for the domain V of the 23S rRNA (nucleotide 1937–2154, accession no. X68422) using Sanger methods and sequences were compared with corresponding region of wildtype reference strain (ATCC 15322). Results For the period of October 2015-March 2017, culture was attempted in 433 PCR-positive samples, and 347 (80%) yield an isolate. Sequencing was performed in those 347 samples and was successful in 334 (96%). A macrolide resistance mutation was detected in 10 samples (3%). From the 10 mutations detected, 7 (70%) were the A2063G mutation, and 3 (30%) were A2064G. We also detected a deletion in A2065 of unknown significance in 3 samples (0.9%). Conclusion In this pediatric population, culture was successful in 80% of PCR positive samples, thus providing isolates for sequencing to be able to assess our local resistance. Our overall Mp resistance was 3%, suggesting that empiric treatment with macrolides is still appropriate in Central Ohio. Additional studies are needed to correlate the presence of these resistance mutations with phenotypic susceptibility testing and clinical outcomes. Disclosures O. Ramilo, Abbvie: Board Member, Consulting fee; Regeneron: Board Member, Consulting fee; Janssen: Board Member and Investigator, Consulting fee and Research grant; NIH: Grant Investigator, Research grant; A. Leber, BioFIre Dia gnostics: Research Contractor and Scientific Advisor, Research support, Speaker honorarium and Travel expenses

Background Interferons (IFN) play a major role in regulating innate and adaptive immune responses. Studies in adults and older children demonstrated significant correlations between IFN gene expression and antibody responses to influenza vaccines. However, there is still an incomplete understanding of the role of IFN in the ontogeny of the infant immune system and how they affect the immune response to vaccines in this population. Our objective with this study is to define longitudinal age-related changes in interferon gene expression and the changes induced by routine vaccinations. Methods We enrolled 2 cohorts of healthy children: 81 children aged < 2 years evaluated at one-time point to assess age-dependent changes in IFN gene expression; and 47 < 1 year olds evaluated at three times, before vaccination (day (d) 0) and d7 and d30 post-vaccination. Peripheral blood samples were collected to measure: (a) immune transcriptional profiles by microarrays; (b) immune cell populations by flow cytometry, and (c) antibody titers to PCV13, Hib and DTaP in the vaccination cohort. Results Analysis of first cohort demonstrated significant underexpression of IFN genes (n = 120) in infants aged Conclusion IFN gene expression at baseline is markedly reduced in infants Disclosures O. Ramilo, Abbvie: Board Member, Consulting fee; Regeneron: Board Member, Consulting fee; Janssen: Board Member and Investigator, Consulting fee and Research grant; NIH: Grant Investigator, Research grant

Symptomatic Infection vs Asymptomatic Detection S. Heinonen1, N.M. Suarez1, T. Jartti2, S. Oliva3, C. Garcia4, O. Ramilo1 and A. Mejias1 1Center for Vaccines and Immunity, The Research Institute at Nationwide Children’s Hospital, Columbus, OH, USA; 2Department of Pediatrics, Turku University Hospital, Turku, Finland; 3Hospital Materno Infantil, Malaga’s University, Malaga, Spain; 4Division of Pediatric Infectious Diseases, University of Texas Southwestern Medical Center, Dallas, TX, USA