GII.4 variants cause the highest burden of norovirus acute gastroenteritis (AGE) in children aged <2 years. In a phase 2b trial (NCT05281094), infants 5 months of age received two doses of a GI.1/GII.4c virus-like particle vaccine candidate (N=1425) or placebo (N=1399). Over 6-months, 23 vaccine and 29 placebo recipients experienced GII.4 moderate/severe AGE resulting in a vaccine efficacy of 13% (95% CI: -53%, 50%; mFAS). Lack of protection coincided with narrow surrogate neutralizing antibody titer (sNAbT) breadth post-vaccination. Post-GII.4 AGE of any severity, sNAbT to heterotypic GII.4 variants was higher in vaccinees compared to placebo recipients at ~13 months of age, indicating multiple variant exposures improved sNAbT breadth. Phase 2 trial data from children and adults suggest that GII.4 pre-existing immunity may be a pre-requisite for developing broad GII.4 sNAbT necessary for protection. Consequently, future infant norovirus vaccines should strategically prioritize enhancement of sNAb titer and breadth in naïve populations.

Trypanophobia, an intense fear of needles in a medical setting, affects 33% to 66% of children and up to 10% of the total population, hundreds of millions of people. Additionally, many side effects result from traditional needle injections, such as a high risk of infection and contamination. Finding an alternative to traditional hypodermic vaccine delivery is vital for patients worldwide. Microneedles are small arrays of needles that penetrate a small area with restricted depth. They cause minor inflammation and damage to the dermal layers compared to traditional needles and were engineered to penetrate the epidermis to convey a drug directly into the subepidermal vesicular without reaching nerve endings and blood vessels which cause the pain associated with needles. This study aimed to develop water-soluble microneedles from hyaluronic acid that include both proteins OVA and BSA. The microneedle we developed demonstrated significant protein delivery in human umbilical vein endothelial cells and is expected to be a new method of vaccine delivery in the future.

BACKGROUND. HIV-1-specific broadly neutralizing monoclonal antibodies (bNAbs) have emerged as promising interventions with the potential to effectively treat and prevent HIV-1 infections. We conducted a phase I clinical trial evaluating the potent CD4-binding site-specific (CD4bs-specific) bNAbs VRC01LS and VRC07-523LS in people with HIV-1 (PWH) not receiving antiretroviral therapy (ART). METHODS. Participants received a single intravenous 40 mg/kg dose of either VRC01LS (n = 7) or VRC07-523LS (n = 9) and did not initiate ART for a minimum of 14 days. The primary study objective was to evaluate safety and tolerability; the secondary study objectives were to evaluate pharmacokinetics (PK) and the impact of administered bNAbs on viral loads (VL) and CD4(+) T cell counts in the absence of ART. RESULTS. This trial enrolled 16 PWH aged 20 to 57 years. Both bNAbs were safe and well tolerated. Mild local reactogenicity was only reported in participants who received VRC07-523LS, while both bNAbs were associated with mild systemic symptoms. Maximum serum concentrations (C-max) following VRC01LS or VRC07-523LS were 1,566 +/- 316 and 1,295 +/- 376 mu g/mL, respectively. VRC07-523LS administration significantly decreased VL in 8 out of 9 participants, with an average decline of 1.7 +/- 0.8 log(10) copies/mL within 14 days after administration. In contrast, VRC01LS administration resulted in a smaller average decline (0.8 +/- 0.8 log(10) copies/mL), and 3 out of 7 participants showedno change in VL. Postinfusion maximum decline in VL correlated with post hoc baseline in vitro viral susceptibility results for both bNAbs. CONCLUSION. The results of this trial support inclusion of potent CD4bs-specific bNAbs, such as VRC07-523LS, into next-generation treatment regimens for HIV-1. TRIAL REGISTRATION. ClinicalTrials.gov NCT02840474.

INTRODUCTION:As no standard case definitions for respiratory syncytial virus-associated lower respiratory tract disease (RSV-LRTD) in adults are available, this study analyzed definitions for severe RSV-LRTD from previously published data in hospital and community cohorts of adults with RSV-associated symptoms. METHODS:The frequency, sensitivity, and specificity of acute respiratory disease symptoms among hospitalized and community cohorts of adults with RSV were analyzed. RSV-LRTD signs/symptoms assessed included shortness of breath (dyspnea), cough and/or fever, wheezing/rales/rhonchi (abnormal lung sounds by auscultation), sputum production, tachypnea, hypoxemia, and pleuritic chest pain. RESULTS:Dyspnea and tachypnea provided the best differentiation between hospitalized and community RSV-positive cases. The severe RSV-LRTD case definition yielding one of the highest and best-balanced sensitivity and specificity was dyspnea paired with either abnormal lung sounds by auscultation, hypoxemia, tachypnea, cough and/or fever, sputum, or chest pain. CONCLUSIONS:Dyspnea alone, and in combination with certain other lower respiratory tract disease signs/symptoms, was a leading symptomatic indicator for severe RSV outcomes. These results contribute to the harmonization of case definitions for RSV disease.

Background An mRNA-based respiratory syncytial virus (RSV) vaccine, mRNA-1345, is under clinical investigation to address RSV disease burden in older adults.Methods Based on a randomized, observer-blind, placebo-controlled design, this phase 1 dose-ranging study evaluated the safety, reactogenicity, and immunogenicity of mRNA-1345 in adults aged 65 to 79 years. Participants were randomized to receive 1 dose of mRNA-1345 (12.5, 25, 50, 100, or 200 mu g) or placebo and matched mRNA-1345 booster or placebo at 12 months.Results Overall, 298 participants received the first injection and 247 received the 12-month booster injection. mRNA-1345 was generally well tolerated after both injections, with the most frequently reported solicited adverse reactions being injection site pain, fatigue, headache, arthralgia, and myalgia. Reactogenicity was higher after the booster injection but with severity, time to onset, and duration similar to the first injection. A single mRNA-1345 injection boosted RSV-A and RSV-B neutralizing antibody titers and prefusion F binding antibody (preF bAb) concentrations at 1 month (geometric mean fold rises: RSV-A, 10.2-16.5; RSV-B, 5.3-12.5; preF bAb, 7.2-12.1). RSV antibody levels remained above baseline through 12 months, indicating immune persistence. A 12-month booster injection also increased RSV-A and RSV-B neutralizing antibody titers and preF bAb concentrations; titers after booster injection were numerically lower than those after the first dose, with overlapping 95% CIs.Conclusions mRNA-1345 was well tolerated and immunogenic following a single injection and a 12-month booster.Clinical Trials Registration NCT04528719 (ClinicalTrials.gov). Older adults and those with comorbidities are at increased risk of severe RSV. We assessed the safety and immunogenicity of mRNA-1345, an RSV vaccine, in adults aged 65 to 79 years. mRNA-1345 was well tolerated and immunogenic following a single injection and 12-month booster.

Background Respiratory syncytial virus (RSV) represents a global health concern, including in older adults. This study assessed the safety and immunogenicity of mRNA-1345, an investigational mRNA RSV vaccine, in adults aged ≥60 years of Japanese descent. Methods In this phase 1, randomized, observer-blind, placebo-controlled study, participants were randomized to receive one injection of mRNA-1345 100 μg or placebo. Solicited local and systemic adverse reactions (ARs) were collected within 7 days following injection. Unsolicited adverse events (AEs) were collected up to 28 days after injection; AEs of special interest, medically attended AEs, and serious AEs were collected through end of study. Immunogenicity was assessed at baseline and months 1, 2, 3, and 6 following injection. Results Twenty-five adults of Japanese descent aged ≥60 years received one injection of mRNA-1345 100 μg (n = 21) or placebo (n = 4). mRNA-1345 was well-tolerated; the most common local and systemic solicited ARs were injection site pain, and fatigue and myalgia, respectively, which were generally mild to moderate and transient. No serious AEs were reported. Neutralizing (nAb) and binding (bAb) antibodies were detectable at baseline, consistent with prior RSV exposure. mRNA-1345 boosted RSV nAb titers and preF bAb concentrations 1 month post-injection (geometric mean fold rise: RSV-A nAb, 11.2; RSV-B nAb, 6.6; preF bAb, 9.1). Titers among mRNA-1345 recipients remained above baseline through 6 months. Conclusions mRNA-1345 100 μg was well-tolerated among older adults of Japanese descent and induced nAbs and bAbs which were durable through 6 months, supporting its continued development. Trial registration ClinicalTrials.gov, NCT04528719.

Transcriptomics analyses play pivotal roles in understanding the complex regulatory networks that govern cellular processes. The abundance of rRNAs, which account for 80%-90% of total RNA in eukaryotes, limits the detection and investigation of other transcripts. While mRNAs and long noncoding RNAs have poly(A) tails that are often used for positive selection, investigations of poly(A)(-) RNAs, such as circular RNAs, histone mRNAs, and small RNAs, typically require the removal of the abundant rRNAs for enrichment. Current approaches to deplete rRNAs for downstream molecular biology investigations are hampered by restrictive RNA input masses and high costs. To address these challenges, we developed rRNA Removal by RNaseH (rRRR), a method to efficiently deplete rRNAs from a wide range of human, mouse, and rat RNA inputs and of varying qualities at a cost 10- to 20-fold cheaper than other approaches. We used probe-based hybridization and enzymatic digestion to selectively target and remove rRNA molecules while preserving the integrity of non-rRNA transcripts. Comparison of rRRR to two commercially available approaches showed similar rRNA depletion efficiencies and comparable off-target effects. Our developed method provides researchers with a valuable tool for investigating gene expression and regulatory mechanisms across a wide range of biological systems at an affordable price that increases the accessibility for researchers to enter the field, ultimately advancing our understanding of cellular processes.

BACKGROUNDBroadly neutralizing monoclonal antibodies (bNAbs) represent a promising strategy for HIV-1 immunoprophylaxis and treatment. 10E8VLS and VRC07-523LS are bNAbs that target the highly conserved membrane-proximal external region (MPER) and the CD4-binding site of the HIV-1 viral envelope glycoprotein, respectively.METHODSIn this phase 1, open-label trial, we evaluated the safety and pharmacokinetics of 5 mg/kg 10E8VLS administered alone, or concurrently with 5 mg/kg VRC07-523LS, via s.c. injection to healthy non-HIV-infected individuals.RESULTSEight participants received either 10E8VLS alone (n = 6) or 10E8VLS and VRC07-523LS in combination (n = 2). Five (n = 5 of 8, 62.5%) participants who received 10E8VLS experienced moderate local reactogenicity, and 1 participant (n = 1/8, 12.5%) experienced severe local reactogenicity. Further trial enrollment was stopped, and no participant received repeat dosing. All local reactogenicity resolved without sequelae. 10E8VLS retained its neutralizing capacity, and no functional anti-drug antibodies were detected; however, a serum t1/2 of 8.1 days was shorter than expected. Therefore, the trial was voluntarily stopped per sponsor decision (Vaccine Research Center, National Institute of Allergy and Infectious Diseases [NIAID], NIH). Mechanistic studies performed to investigate the underlying reason for the reactogenicity suggest that multiple mechanisms may have contributed, including antibody aggregation and upregulation of local inflammatory markers.CONCLUSION10E8VLS resulted in unexpected reactogenicity and a shorter t1/2 in comparison with previously tested bNAbs. These studies may facilitate identification of nonreactogenic second-generation MPER-targeting bNAbs, which could be an effective strategy for HIV-1 immunoprophylaxis and treatment.TRIAL REGISTRATIONClinicaltrials.gov, accession no. NCT03565315.FUNDINGDivision of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH.

Influenza A virus subtype H2N2, which caused the 1957 influenza pandemic, remains a global threat. A recent phase 1 clinical trial investigating a ferritin nanoparticle vaccine displaying H2 hemagglutinin (HA) in H2-naive and H2-exposed adults enabled us to perform comprehensive structural and biochemical characterization of immune memory on the breadth and diversity of the polyclonal serum antibody response elicited. We temporally map the epitopes targeted by serum antibodies after vaccine prime and boost, revealing that previous H2 exposure results in higher responses to the variable HA head domain. In contrast, initial responses in H2-naive participants are dominated by antibodies targeting conserved epitopes. We use cryoelectron microscopy and monoclonal B cell isolation to describe the molecular details of cross-reactive antibodies targeting conserved epitopes on the HA head, including the receptor-binding site and a new site of vulnerability deemed the medial junction. Our findings accentuate the impact of pre-existing influenza exposure on serum antibody responses post-vaccination.

Background Respiratory syncytial virus (RSV) presents a global health concern. A lipid nanoparticle-encapsulated mRNA-based RSV vaccine (mRNA-1345) that encodes the membrane-anchored RSV prefusion-stabilized F glycoprotein is under clinical investigation.Methods This phase 1 dose escalation study was based on a randomized, observer-blind, placebo-controlled design, and it assessed the safety and immunogenicity of mRNA-1345 in healthy adults aged 18 to 49 years. Participants were randomized to receive 1 dose of mRNA-1345 (50, 100, or 200 mu g) or placebo or 3 doses of mRNA-1345 (100 mu g) or placebo 56 days apart.Results mRNA-1345 was well tolerated at all dose levels. The most common solicited adverse reactions were pain, headache, fatigue, myalgia, or chills, which were all generally mild to moderate. At 1 month postinjection, a single injection of mRNA-1345 boosted RSV neutralizing antibody titers (geometric mean fold rise: RSV-A, 20.0-23.5; RSV-B, 11.7-16.0) and RSV prefusion binding antibody concentrations (geometric mean fold rise, 16.1-21.8), with no apparent dose response. Antibody levels remained above baseline through 6 months. Sequential doses of 100 mu g were well tolerated but did not further boost antibody levels.Conclusions A single mRNA-1345 injection demonstrated an acceptable safety profile in younger adults and induced a durable neutralizing antibody response, supporting its continued development.Clinical Trials Registration ClinicalTrials.gov NCT04528719. Respiratory syncytial virus presents a global health concern. We assessed the safety and immunogenicity of an mRNA-based vaccine, mRNA-1345, in healthy adults aged 18 to 49 years. mRNA-1345 vaccine was well tolerated and immunogenic in younger adults.

An mRNA-based RSV vaccine, mRNA-1345, is under clinical investigation to address RSV disease burden in older adults.

Ebola virus disease (EVD) is a filoviral infection caused by virus species of the Ebolavirus genus including Zaire ebolavirus (EBOV) and Sudan ebolavirus (SUDV). We investigated the safety and immunogenicity of a heterologous prime-boost regimen involving a chimpanzee adenovirus 3 vectored Ebola vaccine [either monovalent (cAd3-EBOZ) or bivalent (cAd3-EBO)] prime followed by a recombinant modified vaccinia virus Ankara EBOV vaccine (MVA-EbolaZ) boost in two phase 1/1b randomized open-label clinical trials in healthy adults in the United States (US) and Uganda (UG). Trial US (NCT02408913) enrolled 140 participants, including 26 EVD vaccine-naïve and 114 cAd3-Ebola-experienced participants (April-November 2015). Trial UG (NCT02354404) enrolled 90 participants, including 60 EVD vaccine-naïve and 30 DNA Ebola vaccine-experienced participants (February-April 2015). All tested vaccines and regimens were safe and well tolerated with no serious adverse events reported related to study products. Solicited local and systemic reactogenicity was mostly mild to moderate in severity. The heterologous prime-boost regimen was immunogenic, including induction of durable antibody responses which peaked as early as two weeks and persisted up to one year after each vaccination. Different prime-boost intervals impacted the magnitude of humoral and cellular immune responses. The results from these studies demonstrate promising implications for use of these vaccines in both prophylactic and outbreak settings.

BackgroundRespiratory syncytial virus (RSV) can cause substantial morbidity and mortality among older adults. An mRNA-based RSV vaccine, mRNA-1345, encoding the stabilized RSV prefusion F glycoprotein, is under clinical investigation.MethodsIn this ongoing, randomized, double-blind, placebo-controlled, phase 2-3 trial, we randomly assigned, in a 1:1 ratio, adults 60 years of age or older to receive one dose of mRNA-1345 (50 mu g) or placebo. The two primary efficacy end points were the prevention of RSV-associated lower respiratory tract disease with at least two signs or symptoms and with at least three signs or symptoms. A key secondary efficacy end point was the prevention of RSV-associated acute respiratory disease. Safety was also assessed.ResultsOverall, 35,541 participants were assigned to receive the mRNA-1345 vaccine (17,793 participants) or placebo (17,748). The median follow-up was 112 days (range, 1 to 379). The primary analyses were conducted when at least 50% of the anticipated cases of RSV-associated lower respiratory tract disease had occurred. Vaccine efficacy was 83.7% (95.88% confidence interval [CI], 66.0 to 92.2) against RSV-associated lower respiratory tract disease with at least two signs or symptoms and 82.4% (96.36% CI, 34.8 to 95.3) against the disease with at least three signs or symptoms. Vaccine efficacy was 68.4% (95% CI, 50.9 to 79.7) against RSV-associated acute respiratory disease. Protection was observed against both RSV subtypes (A and B) and was generally consistent across subgroups defined according to age and coexisting conditions. Participants in the mRNA-1345 group had a higher incidence than those in the placebo group of solicited local adverse reactions (58.7% vs. 16.2%) and of systemic adverse reactions (47.7% vs. 32.9%); most reactions were mild to moderate in severity and were transient. Serious adverse events occurred in 2.8% of the participants in each trial group.ConclusionsA single dose of the mRNA-1345 vaccine resulted in no evident safety concerns and led to a lower incidence of RSV-associated lower respiratory tract disease and of RSV-associated acute respiratory disease than placebo among adults 60 years of age or older. (Funded by Moderna; ConquerRSV ClinicalTrials.gov number, NCT05127434.) In a placebo-controlled, phase 2-3 trial, one dose of mRNA-1345 led to a lower incidence of RSV disease among adults 60 years of age or older. Solicited local and systemic adverse reactions occurred more often with the vaccine.

Circular RNAs (circRNAs) are single-stranded RNAs that are covalently closed and lack free ends. While relatively little is known about the roles of circRNAs in innate immunity, several studies suggest that endogenous circRNAs are immunosuppressive in nature. But whether engineered circRNAs produced exogenously and then delivered into cells are immunostimulatory has been a debated question in recent years. In this perspective, we review and compare the investigations on engineered circRNA immunogenicity. We discuss the possible factors that may alter the immunogenic potential of a circRNA, such as its generation, purification, primary sequence, secondary structure, and RNA modifications. We also suggest approaches for designing a circRNA with immunostimulatory or immune-evasive properties and recommend future areas for the field to investigate. A clear understanding of the immune effects from engineered circRNAs would offer insight into fundamental principles of how cells differentiate between self and non-self RNAs as well as provide a foundation for translating circRNAs into therapies.

Influenza vaccines could be improved by platforms inducing cross-reactive immunity. Immunodominance of the influenza hemagglutinin (HA) head in currently licensed vaccines impedes induction of cross-reactive neutralizing stem-directed antibodies. A vaccine without the variable HA head domain has the potential to focus the immune response on the conserved HA stem. This first-in-human dose-escalation open-label phase 1 clinical trial (NCT03814720) tested an HA stabilized stem ferritin nanoparticle vaccine (H1ssF) based on the H1 HA stem of A/New Caledonia/20/1999. Fifty-two healthy adults aged 18 to 70 years old enrolled to receive either 20 μg of H1ssF once (n = 5) or 60 μg of H1ssF twice (n = 47) with a prime-boost interval of 16 weeks. Thirty-five (74%) 60-μg dose participants received the boost, whereas 11 (23%) boost vaccinations were missed because of public health restrictions in the early stages of the COVID-19 pandemic. The primary objective of this trial was to evaluate the safety and tolerability of H1ssF, and the secondary objective was to evaluate antibody responses after vaccination. H1ssF was safe and well tolerated, with mild solicited local and systemic reactogenicity. The most common symptoms included pain or tenderness at the injection site (n = 10, 19%), headache (n = 10, 19%), and malaise (n = 6, 12%). We found that H1ssF elicited cross-reactive neutralizing antibodies against the conserved HA stem of group 1 influenza viruses, despite previous H1 subtype head-specific immunity. These responses were durable, with neutralizing antibodies observed more than 1 year after vaccination. Our results support this platform as a step forward in the development of a universal influenza vaccine.

Current yearly seasonal influenza vaccines primarily induce an antibody response directed against the immunodominant but continually diversifying hemagglutinin (HA) head region. These antibody responses provide protection against the vaccinating strain but little cross-protection against other influenza strains or subtypes. To focus the immune response on subdominant but more conserved epitopes on the HA stem that might protect against a broad range of influenza strains, we developed a stabilized H1 stem immunogen lacking the immunodominant head displayed on a ferritin nanoparticle (H1ssF). Here, we evaluated the B cell response to H1ssF in healthy adults ages 18 to 70 in a phase 1 clinical trial (NCT03814720). We observed both a strong plasmablast response and sustained elicitation of cross-reactive HA stem-specific memory B cells after vaccination with H1ssF in individuals of all ages. The B cell response was focused on two conserved epitopes on the H1 stem, with a highly restricted immunoglobulin repertoire unique to each epitope. On average, two-thirds of the B cell and serological antibody response recognized a central epitope on the H1 stem and exhibited broad neutralization across group 1 influenza virus subtypes. The remaining third recognized an epitope near the viral membrane anchor and was largely limited to H1 strains. Together, we demonstrate that an H1 HA immunogen lacking the immunodominant HA head produces a robust and broadly neutralizing HA stem-directed B cell response.

In a phase 2 safety and immunogenicity study of a chikungunya virus virus-like particle (CHIKV VLP) vaccine in an endemic region, of 400 total participants, 78 were found to be focus reduction neutralizing antibody seropositive at vaccination despite being ELISA seronegative at screening, of which 39 received vaccine. This post hoc analysis compared safety and immunogenicity of CHIKV VLP vaccine in seropositive (n = 39) versus seronegative (n = 155) vaccine recipients for 72 weeks post-vaccination. There were no differences in solicited adverse events, except injection site swelling in 10.3% of seropositive versus 0.6% of seronegative recipients (p = 0.006). Baseline seropositive vaccine recipients had stronger post-vaccination luciferase neutralizing antibody responses versus seronegative recipients (peak geometric mean titer of 3594 and 1728, respectively) persisting for 72 weeks, with geometric mean fold increases of 3.1 and 13.2, respectively. In this small study, CHIKV VLP vaccine was well-tolerated and immunogenic in individuals with pre-existing immunity. ClinicalTrials.gov Identifier: NCT02562482.

Abstract Background Respiratory syncytial virus (RSV), human metapneumovirus (hMPV), and parainfluenza virus type 3 (PIV3) are common respiratory illnesses in children. Two investigational vaccines, mRNA-1345, encoding the RSV prefusion stabilized F (preF) glycoprotein, and mRNA-1653, encoding the hMPV and PIV3 F glycoproteins, are in clinical trials. Methods Two phase 1, randomized, observer-blind, placebo-controlled trials in children aged 12-59 months assessed safety and immunogenicity of mRNA-1345 (NCT04528719) and mRNA-1653 (NCT04144348). In the mRNA-1345 trial, RSV-seropositive children (N=46) were randomized to receive 3 doses of mRNA-1345 (15 µg or 30 µg) or placebo 2 months apart. In the mRNA-1653 trial, hMPV- and PIV3-seropositive children (N=27) were randomized to receive 2 doses of mRNA-1653 (10 µg or 30 µg) or placebo 2 months apart. Interim data through Month (M) 5 for mRNA-1345 and M3 for mRNA-1653 are reported. Results mRNA-1345 and mRNA-1653 were well-tolerated. The most frequently reported solicited local adverse reaction (AR) was tenderness at injection site (mRNA-1345, 35.7%-71.4%; placebo, 26.7%-42.9% and mRNA-1653, 44.4%-60.0%; placebo, 12.5%-30.0%); solicited systemic ARs (mRNA-1345, 12.5%-53.3%; placebo, 33.3%-50.0% and mRNA-1653, 33.3%-55.6%; placebo, 12.5%-60.0%) were mostly grade 1/2. One mRNA-1345 injection boosted RSV neutralizing antibody (nAb) titers (geometric mean fold rise [GMFR] over baseline: RSV-A=18.9-34.9; RSV-B=7.2-14.3) and RSV preF and postF binding antibody (bAb) concentrations (GMFR: preF=13.9-26.5; postF=9.3-16.0); additional injections did not further elevate antibody levels (Fig 1A and 2A). One mRNA-1653 injection boosted hMPV and PIV3 nAb titers (GMFR over baseline: hMPV-A=2.9-6.1; hMPV-B=6.2-13.2; PIV3=2.8-3.0) and preF and postF bAb concentrations (GMFR: hMPV preF=5.3-6.1; postF=4.6-6.5 and PIV3 preF=13.9-14.2; postF=11.0-12.1); a second injection did not further increase antibody levels (Fig 1B,C and 2B,C). In both trials, bAb responses were generally preF biased. Conclusion In seropositive children aged 12-59 months, mRNA-1345 and mRNA-1653 were well-tolerated and boosted RSV and hMPV plus PIV3 antibodies, respectively, supporting their continued development and that of a combination RSV and hMPV vaccine. Disclosures Matthew D. Snape, MBBS, MD, FRCPCH, FPM, FMedSci, Moderna Biotech UK, Inc.,: Employee|Moderna Biotech UK, Inc.,: Stocks/Bonds Sabine Schnyder Ghamloush, MD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Grace L. Chen, MD, MPH, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Rakesh Dhar, MD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Runa Mithani, PharmD, Moderna, Inc: Employee|Moderna, Inc: Stocks/Bonds Vinicius Righi, PharmD, MBA, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Louie Morsy, BS, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Archana Kapoor, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Bethany Girard, Ph.D., Moderna, Inc.: salary|Moderna, Inc.: Stocks/Bonds Laila El Asmar, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds Christine A. Shaw, PhD, Moderna, Inc.: Employee|Moderna, Inc.: Stocks/Bonds

Severe COVID-19 is characterized by persistent lung inflammation, inflammatory cytokine production, viral RNA, and sustained interferon (IFN) response all of which are recapitulated and required for pathology in the SARS-CoV-2 infected MISTRG6-hACE2 humanized mouse model of COVID-19 with a human immune system 1-20 . Blocking either viral replication with Remdesivir 21-23 or the downstream IFN stimulated cascade with anti-IFNAR2 in vivo in the chronic stages of disease attenuated the overactive immune-inflammatory response, especially inflammatory macrophages. Here, we show SARS-CoV-2 infection and replication in lung-resident human macrophages is a critical driver of disease. In response to infection mediated by CD16 and ACE2 receptors, human macrophages activate inflammasomes, release IL-1 and IL-18 and undergo pyroptosis thereby contributing to the hyperinflammatory state of the lungs. Inflammasome activation and its accompanying inflammatory response is necessary for lung inflammation, as inhibition of the NLRP3 inflammasome pathway reverses chronic lung pathology. Remarkably, this same blockade of inflammasome activation leads to the release of infectious virus by the infected macrophages. Thus, inflammasomes oppose host infection by SARS-CoV-2 by production of inflammatory cytokines and suicide by pyroptosis to prevent a productive viral cycle.