Single-Dose Nirsevimab for Prevention of RSV in Preterm Infants.

BACKGROUND: Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants, and a need exists for prevention of RSV in healthy infants. Nirsevimab is a monoclonal antibody with an extended half-life that is being developed to protect infants for an entire RSV season with a single intramuscular dose. METHODS: In this trial conducted in both northern and southern hemispheres, we evaluated nirsevimab for the prevention of RSV-associated lower respiratory tract infection in healthy infants who had been born preterm (29 weeks 0 days to 34 weeks 6 days of gestation). We randomly assigned the infants in a 2:1 ratio to receive nirsevimab, at a dose of 50 mg in a single intramuscular injection, or placebo at the start of an RSV season. The primary end point was medically attended RSV-associated lower respiratory tract infection through 150 days after administration of the dose. The secondary efficacy end point was hospitalization for RSV-associated lower respiratory tract infection through 150 days after administration of the dose. RESULTS: From November 2016 through November 2017, a total of 1453 infants were randomly assigned to receive nirsevimab (969 infants) or placebo (484 infants) at the start of the RSV season. The incidence of medically attended RSV-associated lower respiratory tract infection was 70.1% lower (95% confidence interval [CI], 52.3 to 81.2) with nirsevimab prophylaxis than with placebo (2.6% [25 infants] vs. 9.5% [46 infants]; P<0.001) and the incidence of hospitalization for RSV-associated lower respiratory tract infection was 78.4% lower (95% CI, 51.9 to 90.3) with nirsevimab than with placebo (0.8% [8 infants] vs. 4.1% [20 infants]; P<0.001). These differences were consistent throughout the 150-day period after the dose was administered and across geographic locations and RSV subtypes. Adverse events were similar in the two trial groups, with no notable hypersensitivity reactions. CONCLUSIONS: A single injection of nirsevimab resulted in fewer medically attended RSV-associated lower respiratory tract infections and hospitalizations than placebo throughout the RSV season in healthy preterm infants. (Funded by AstraZeneca and Sanofi Pasteur; ClinicalTrials.gov number, NCT02878330.).

Safety and Antiviral Effects of Nebulized PC786 in a Respiratory Syncytial Virus Challenge Study.

BACKGROUND: PC786 is a nebulized nonnucleoside respiratory syncytial virus (RSV) polymerase inhibitor designed to treat RSV, which replicates in the superficial layer of epithelial cells lining the airways. METHODS: Fifty-six healthy volunteers inoculated with RSV-A (Memphis 37b) were randomly dosed with either nebulized PC786 (5 mg) or placebo, twice daily for 5 days, from either 12 hours after confirmation of RSV infection or 6 days after virus inoculation. Viral load (VL), disease severity, pharmacokinetics, and safety were assessed until discharge. RSV infection was confirmed by reverse-transcription quantitative polymerase chain reaction with any positive value (intention-to-treat infected [ITT-I] population) or RSV RNA ≥1 log10 plaque-forming unit equivalents (PFUe)/mL (specific intention-to-treat infection [ITT-IS] population) in nasal wash samples. RESULTS: In the ITT-I population, the mean VL area under the curve (AUC) was lower in the PC786 group than the placebo group (274.1 vs 406.6 log10 PFUe/mL × hour; P = .0359). PC786 showed a trend toward reduction of symptom score and mucous weight. In ITT-IS (post hoc analysis), the latter was statistically significant as well as VL AUC (P = .0126). PC786 showed an early time to maximum plasma concentration, limited systemic exposure, and long half-life and consequently a 2-fold accumulation over the 5-day dosing period. PC786 was well tolerated. CONCLUSIONS: Nebulized PC786 demonstrated a significant antiviral effect against RSV, warranting further clinical study. CLINICAL TRIALS REGISTRATION: ClinicalTrials.gov: NCT03382431; EudraCT: 2017-002563-18.

Prevention of Respiratory Syncytial Virus Infection in Healthy Adults by a Single Immunization of Ad26.RSV.preF in a Human Challenge Study.

BACKGROUND: Respiratory syncytial virus (RSV) is a significant cause of severe lower respiratory tract disease in children and older adults, but has no approved vaccine. This study assessed the potential of Ad26.RSV.preF to protect against RSV infection and disease in an RSV human challenge model. METHODS: In this double-blind, placebo-controlled study, healthy adults aged 18-50 years were randomized 1:1 to receive 1 × 1011 vp Ad26.RSV.preF or placebo intramuscularly. Twenty-eight days postimmunization, volunteers were challenged intranasally with RSV-A (Memphis 37b). Assessments included viral load (VL), RSV infections, clinical symptom score (CSS), safety, and immunogenicity. RESULTS: Postchallenge, VL, RSV infections, and disease severity were lower in Ad26.RSV.preF (n = 27) vs placebo (n = 26) recipients: median VL area under the curve (AUC) quantitative real-time polymerase chain reaction: 0.0 vs 236.0 (P = .012; predefined primary endpoint); median VL-AUC quantitative culture: 0.0 vs 109; RSV infections 11 (40.7%) vs 17 (65.4%); median RSV AUC-CSS 35 vs 167, respectively. From baseline to 28 days postimmunization, geometric mean fold increases in RSV A2 neutralizing antibody titers of 5.8 and 0.9 were observed in Ad26.RSV.preF and placebo, respectively. Ad26.RSV.preF was well tolerated. CONCLUSIONS: Ad26.RSV.preF demonstrated protection from RSV infection through immunization in a human challenge model, and therefore could potentially protect against natural RSV infection and disease. CLINICAL TRIALS REGISTRATION: NCT03334695; CR108398, 2017-003194-33 (EudraCT); VAC18193RSV2002.

Respiratory Syncytial Virus Disease Severity Is Associated with Distinct CD8+ T-Cell Profiles.

Rationale: Respiratory syncytial virus (RSV) causes significant morbidity and mortality in infants worldwide. Although T-helper type 2 (Th2) cell pathology is implicated in severe disease, the mechanisms underlying the development of immunopathology are incompletely understood.Objectives: We aimed to identify local immune responses associated with severe RSV in infants. Our hypothesis was that disease severity would correlate with enhanced Th2 cellular responses.Methods: Nasal aspirates were collected from infants hospitalized with severe (admitted to the pediatric ICU) or moderate (maintained in the general ward) RSV disease at 5 to 9 days after enrollment. The immune response was investigated by evaluating T-lymphocyte cellularity, cytokine concentration, and viral load.Measurements and Main Results: Patients with severe disease had increased proportions of CD8 (cluster of differentiation 8)-positive T cells expressing IL-4 (Tc2) and reduced proportions of CD8+ T cells expressing IFNγ (Tc1). Nasal aspirates from patients with severe disease had reduced concentrations of IL-17. Patients with greater frequencies of Tc1, CD8+ T cells expressing IL-17 (Tc17), and CD4+ T cells expressing IL-17 (Th17) had shorter durations of hospitalization.Conclusions: Severe RSV disease was associated with distinct T-cell profiles. Tc1, Tc17, and Th17 were associated with shorter hospital stay and may play a protective role, whereas Tc2 cells may play a previously underappreciated role in pathology.

Drug Resistance Assessment Following Administration of Respiratory Syncytial Virus (RSV) Fusion Inhibitor Presatovir to Participants Experimentally Infected With RSV.

BACKGROUND: Presatovir is an oral respiratory syncytial virus (RSV) fusion inhibitor targeting RSV F protein. In a double-blind, placebo-controlled study in healthy adults experimentally infected with RSV (Memphis-37b), presatovir significantly reduced viral load and clinical disease severity in a dose-dependent manner. METHODS: Viral RNA from nasal wash samples was amplified and the F gene sequenced to monitor presatovir resistance. Effects of identified amino acid substitutions on in vitro susceptibility to presatovir, viral fitness, and clinical outcome were assessed. RESULTS: Twenty-eight treatment-emergent F substitutions were identified. Of these, 26 were tested in vitro; 2 were not due to lack of recombinant virus recovery. Ten substitutions did not affect presatovir susceptibility, and 16 substitutions reduced RSV susceptibility to presatovir (2.9- to 410-fold). No substitutions altered RSV susceptibility to palivizumab or ribavirin. Frequency of phenotypically resistant substitutions was higher with regimens containing lower presatovir dose and shorter treatment duration. Participants with phenotypic presatovir resistance had significantly higher nasal viral load area under the curve relative to those without, but substitutions did not significantly affect peak viral load or clinical manifestations of RSV disease. CONCLUSIONS: Emergence of presatovir-resistant RSV occurred during therapy but did not significantly affect clinical efficacy in participants with experimental RSV infection.

A Randomized, Placebo-Controlled, Respiratory Syncytial Virus Human Challenge Study of the Antiviral Efficacy, Safety, and Pharmacokinetics of RV521, an Inhibitor of the RSV-F Protein.

Effective treatments for respiratory syncytial virus (RSV) infection are lacking. Here, we report a human proof-of-concept study for RV521, a small-molecule antiviral inhibitor of the RSV-F protein. In this randomized, double-blind, placebo-controlled trial, healthy adults were challenged with RSV-A Memphis-37b. After infection was confirmed (or 5 days after challenge virus inoculation), subjects received RV521 (350 mg or 200 mg) or placebo orally every 12 h for 5 days. The primary endpoint was area under the curve (AUC) for viral load, as assessed by reverse transcriptase quantitative PCR (RT-qPCR) of nasal wash samples. The primary efficacy analysis set included subjects successfully infected with RSV who received ≥1 dose of study drug. A total of 66 subjects were enrolled (n = 22 per group); 53 were included in the primary analysis set (RV521 350 mg: n = 16; 200 mg: n = 18; placebo: n = 19). The mean AUC of RT-qPCR-assessed RSV viral load (log10 PFU equivalents [PFUe]/ml · h) was significantly lower with RV521 350 mg (185.26; standard error [SE], 31.17; P = 0.002) and 200 mg (224.35; SE, 37.60; P = 0.007) versus placebo (501.39; SE, 86.57). Disease severity improved with RV521 350 mg and 200 mg versus placebo (P = 0.002 and P = 0.009, respectively, for AUC total symptom score [score × hours]). Daily nasal mucus weight was significantly reduced (P = 0.010 and P = 0.038 for RV521 350 mg and 200 mg, respectively, versus placebo). All treatment-emergent adverse events were grade 1 or 2. No subjects discontinued due to adverse events. There was no evidence of clinically significant viral resistance, and only three variants were detected. RV521 effectively reduced RSV viral load and disease severity in humans and was well tolerated. (This study has been registered at ClinicalTrials.gov under registration no. NCT03258502.).

Altered gut microbiota in infants is associated with respiratory syncytial virus disease severity.

BACKGROUND: Respiratory syncytial virus (RSV) is the number one cause of lower respiratory tract infections in infants. There are still no vaccines or specific antiviral therapies against RSV, mainly due to the inadequate understanding of RSV pathogenesis. Recent data suggest a role for gut microbiota community structure in determining RSV disease severity. Our objective was to determine the gut microbial profile associated with severe RSV patients, which could be used to help identify at-risk patients and develop therapeutically protective microbial assemblages that may stimulate immuno-protection. RESULTS: We enrolled 95 infants from Le Bonheur during the 2014 to 2016 RSV season. Of these, 37 were well-babies and 58 were hospitalized with RSV. Of the RSV infected babies, 53 remained in the pediatric ward (moderate) and 5 were moved to the pediatric intensive care unit at a later date (severe). Stool samples were collected within 72 h of admission; and the composition of gut microbiota was evaluated via 16S sequencing of fecal DNA. There was a significant enrichment in S24_7, Clostridiales, Odoribacteraceae, Lactobacillaceae, and Actinomyces in RSV (moderate and severe) vs. controls. Patients with severe RSV disease had slightly lower alpha diversity (richness and evenness of the bacterial community) of the gut microbiota compared to patients with moderate RSV and healthy controls. Beta diversity (overall microbial composition) was significantly different between all RSV patients (moderate and severe) compared to controls and had significant microbial composition separating all three groups (control, moderate RSV, and severe RSV). CONCLUSIONS: Collectively, these data demonstrate that a unique gut microbial profile is associated with RSV disease and with severe RSV disease with admission to the pediatric intensive care unit. More mechanistic experiments are needed to determine whether the differences observed in gut microbiota are the cause or consequences of severe RSV disease.

Elevated Levels of Type 2 Respiratory Innate Lymphoid Cells in Human Infants with Severe Respiratory Syncytial Virus Bronchiolitis.

Rationale: Studies of the immune responses at the site of respiratory syncytial virus (RSV) infection are sparse despite nearly five decades of research into understanding RSV disease.Objectives: To investigate the role of mucosal innate immune responses to RSV and respiratory viral load in infants hospitalized with the natural disease.Methods: Cytokines, viral load, and type 2 innate lymphoid cell (ILC2) levels in nasal aspirates, collected within 24 hours of enrollment, from infants hospitalized with RSV infection were quantified.Measurements and Main Results: RSV severity in infants was categorized based on admission to the general ward (moderate) or the pediatric ICU (severe). Evaluable subjects included 30 patients with severe and 63 patients with moderate disease (median age, 74 d; range, 9-297 d). ILC2s were found in the nasal aspirates of patients with severe disease (0.051% of total respiratory CD45+ cells) to a significantly greater extent than in patients with moderate disease (0.018%, P = 0.004). Levels of IL-4, IL-13, IL-33, and IL-1ß were significantly higher in nasal aspirates of patients with severe disease compared with those of patients with moderate disease. Factors associated with disease severity were gestational age (odds ratio, 0.49; 95% confidence interval, 0.29-0.82; P = 0.007) and IL-4 (odds ratio, 9.67; 95% confidence interval, 2.45-38.15; P = 0.001).Conclusions: This study shows, for the first time, that elevated levels of ILC2s is associated with infant RSV severity. The findings highlight the dominance of type-2 responses to RSV infection in infants and suggest an important role of ILC2 in shaping the immune response early during RSV infection.

SENTINEL1: Two-Season Study of Respiratory Syncytial Virus Hospitalizations among U.S. Infants Born at 29 to 35 Weeks' Gestational Age Not Receiving Immunoprophylaxis.

OBJECTIVE: The SENTINEL1 observational study characterized confirmed respiratory syncytial virus hospitalizations (RSVH) among U.S. preterm infants born at 29 to 35 weeks' gestational age (wGA) not receiving respiratory syncytial virus (RSV) immunoprophylaxis (IP) during the 2014 to 2015 and 2015 to 2016 RSV seasons. STUDY DESIGN: All laboratory-confirmed RSVH at participating sites during the 2014 to 2015 and 2015 to 2016 RSV seasons (October 1-April 30) lasting ≥24 hours among preterm infants 29 to 35 wGA and aged <12 months who did not receive RSV IP within 35 days before onset of symptoms were identified and characterized. RESULTS: Results were similar across the two seasons. Among infants with community-acquired RSVH (N = 1,378), 45% were admitted to the intensive care unit (ICU) and 19% required invasive mechanical ventilation (IMV). There were two deaths. Infants aged <6 months accounted for 78% of RSVH observed, 84% of ICU admissions, and 91% requiring IMV. Among infants who were discharged from their birth hospitalization during the RSV season, 82% of RSVH occurred within 60 days of birth hospitalization discharge. CONCLUSION: Among U.S. preterm infants 29 to 35 wGA not receiving RSV IP, RSVH are often severe with almost one-half requiring ICU admission and about one in five needing IMV.

Respiratory syncytial virus-A dynamics and the effects of lumicitabine, a nucleoside viral replication inhibitor, in experimentally infected humans.

Background: Respiratory syncytial virus (RSV) causes high morbidity, with mortality rates approaching or exceeding that of influenza in adult and infant patient populations, respectively. Lumicitabine (ALS-008176 or JNJ-64041575) is an oral nucleoside analogue prodrug in clinical development to treat RSV infections. This prodrug converts to plasma-circulating ALS-8112, and then to the 5'-active nucleoside triphosphate (NTP) form within host cells. We conducted an RSV-A challenge study in healthy adults to evaluate lumicitabine's activity during an active RSV infection. Objectives: To develop a semi-mechanistic mathematical model describing RSV kinetics, and the pharmacokinetics (PK) and pharmacodynamics (PD) of lumicitabine during treatment. Methods: Nasopharyngeal viral load and concentrations of ALS-8112 and ALS-8144 (uridine metabolite) were measured frequently over the study duration. Population viral kinetic and PK/PD models were developed using NONMEM. The RSV life-cycle was described using a target-cell-limited model that included a physiological delay. Results: The estimated clearances of ALS-8112 and ALS-8144 were 54.2 and 115 L/h/70 kg, respectively. A semi-physiological model was linked to predict ALS-8112 conversion to active intracellular NTP. Extensive and rapid RSV reduction occurred after lumicitabine treatment (EC50 = 1.79 µM), with >99% viral inhibition at 2 h after loading dose. Simulated NTP exposures and time to EC50 attainment suggested that rapid therapeutic effects and reduced dosing frequency are achievable in adult and paediatric patients. Conclusions: The semi-mechanistic model characterizes RSV kinetics and the antiviral effectiveness of lumicitabine in an adult challenge population. This model is applicable to guide dose selection in adult and paediatric patients.

Vaccination strategies against respiratory syncytial virus.

Respiratory syncytial virus (RSV) is the most common cause of US infant hospitalization. Additionally, RSV is responsible for 10,000 deaths annually among the elderly across the United States, and accounts for nearly as many hospitalizations as influenza. Currently, several RSV vaccine candidates are under development to target different age groups. To evaluate the potential effectiveness of age-specific vaccination strategies in averting RSV incidence, we developed a transmission model that integrates data on daily infectious viral load and changes of behavior associated with RSV symptoms. Calibrating to RSV weekly incidence rates in Texas, California, Colorado, and Pennsylvania, we show that in all states considered, an infected child under 5 y of age is more than twice as likely as a person over 50 y of age to transmit the virus. Geographic variability in the effectiveness of a vaccination program across states arises from interplay between seasonality patterns, population demography, vaccination uptake, and vaccine mechanism of action. Regardless of these variabilities, our analysis showed that allocating vaccine to children under 5 y of age would be the most efficient strategy per dose to avert RSV in both children and adults. Furthermore, due to substantial indirect protection, the targeting of children is even predicted to reduce RSV in the elderly more than directly vaccinating the elderly themselves. Our results can help inform ongoing clinical trials and future recommendations on RSV vaccination.

Antiviral Activity of Oral JNJ-53718678 in Healthy Adult Volunteers Challenged With Respiratory Syncytial Virus: A Placebo-Controlled Study.

Background: Respiratory syncytial virus (RSV) disease has no effective treatment. JNJ-53718678 is a fusion inhibitor with selective activity against RSV. Methods: After confirmation of RSV infection or 5 days after inoculation with RSV, participants (n = 69) were randomized to JNJ-53718678 75 mg (n = 15), 200 mg (n = 17), 500 mg (n = 18), or placebo (n = 17) orally once daily for 7 days. Antiviral effects were evaluated by assessing RSV RNA viral load (VL) area under the curve (AUC) from baseline (before the first dose) until discharge, time-to-peak VL, duration of viral shedding, clinical symptoms, and quantity of nasal secretions. Results: Mean VL AUC was lower for individuals treated with different doses of JNJ-53718678 versus placebo (203.8-253.8 vs 432.8 log10 PFUe.hour/mL). Also, mean peak VL, time to peak VL, duration of viral shedding, mean overall symptom score, and nasal secretion weight were lower in each JNJ-53718678-treated group versus placebo. No clear exposure-response relationship was observed. Three participants discontinued due to treatment-emergent adverse events of grade 2 and 1 electrocardiogram change (JNJ-53718678 75 mg and 200 mg, respectively) and grade 2 urticaria (placebo). Conclusions: JNJ-53718678 at all 3 doses substantially reduced VL and clinical disease severity, thus establishing clinical proof of concept and the compound's potential as a novel RSV treatment. Clinical trials registration: ClinicalTrials.gov: NCT02387606; EudraCT number: 2014-005041-41.

Activity of Oral ALS-008176 in a Respiratory Syncytial Virus Challenge Study.

BACKGROUND Respiratory syncytial virus (RSV) infection is a cause of substantial morbidity and mortality. There is no known effective therapy. METHODS We conducted a randomized, double-blind, clinical trial in healthy adults inoculated with RSV. Participants received the oral nucleoside analogue ALS-008176 or placebo 12 hours after confirmation of RSV infection or 6 days after inoculation. Treatment was administered every 12 hours for 5 days. Viral load, disease severity, resistance, and safety were measured throughout the 28-day study period, with measurement beginning before inoculation. The primary end point was the area under the curve (AUC) for viral load, which was assessed immediately before administration of the first dose through the 12th day after inoculation in participants infected with RSV. RESULTS A total of 62 participants received placebo or one of three ALS-008176 dosing regimens: 1 loading dose of 750 mg followed by 9 maintenance doses of 500 mg (group 1), 1 loading dose of 750 mg followed by 9 maintenance doses of 150 mg (group 2), or 10 doses of 375 mg (group 3). In the 35 infected participants (23 of whom were treated with ALS-008176), the AUCs for viral load for groups 1, 2, and 3 and the placebo group were 59.9, 73.7, 133.4, and 500.9 log10 plaque-forming-unit equivalents × hours per milliliter, respectively (P≤0.001). The time to nondetectability on polymerase-chain-reaction assay (P<0.001), the peak viral load (P≤0.001), the AUC for symptom score (P<0.05), and the AUC for mucus weight were lower in all groups receiving ALS-008176 than in the placebo group. Antiviral activity was greatest in the two groups that received a loading dose--viral clearance was accelerated (P≤0.05), and the AUC for viral load decreased by 85 to 88% as compared with the placebo group. Within this small trial, no viral rebound or resistance was identified. There were no serious adverse events, and there was no need for premature discontinuation of the study drug. CONCLUSIONS In this RSV challenge study, more rapid RSV clearance and a greater reduction of viral load, with accompanying improvements in the severity of clinical disease, were observed in the groups treated with ALS-008176 than in the placebo group. (Funded by Alios BioPharma; ClinicalTrials.gov number, NCT02094365.).

Rat Lungworm Infection Associated with Central Nervous System Disease - Eight U.S. States, January 2011-January 2017.

Angiostrongyliasis is caused by infection and migration to the brain of larvae of the parasitic nematode Angiostrongylus cantonensis, or rat lungworm. Adult A. cantonensis reside in the lungs of the definitive wild rodent host, where they produce larvae passed in feces, which are then ingested by snails and slugs (gastropods). Human infection typically occurs when gastropods containing mature larvae are inadvertently ingested by humans. Although human infection often is asymptomatic or involves transient mild symptoms, larval migration to the brain can lead to eosinophilic meningitis, focal neurologic deficits, coma, and death. The majority of cases of human angiostrongyliasis occur in Asia and the Pacific Islands, including Hawaii, but autochthonous and imported cases have been reported in the continental United States (1,2), underscoring the importance of provider recognition to ensure prompt identification and treatment. The epidemiologic and clinical features of 12 angiostrongyliasis cases in the continental United States were analyzed. These cases were identified through A. cantonensis polymerase chain reaction (PCR) testing (3) of cerebrospinal fluid (CSF) submitted to CDC from within the continental United States. Six cases were likely a result of autochthonous transmission in the southern United States. All 12 patients had CSF pleocytosis and eosinophilia, consistent with eosinophilic meningitis. Health care providers need to be aware of the possibility of angiostrongyliasis in patients with eosinophilic meningitis, especially in residents in the southern United States or persons who have traveled outside the continental United States and have a history of ingestion of gastropods or contaminated raw vegetables.

Identifying Gaps in Respiratory Syncytial Virus Disease Epidemiology in the United States Prior to the Introduction of Vaccines.

Respiratory syncytial virus (RSV) causes lower respiratory tract illness frequently. No effective antivirals or vaccines for RSV are approved for use in the United States; however, there are at least 50 vaccines and monoclonal antibody products in development, with those targeting older adults and pregnant women (to protect young infants) in phase 2 and 3 clinical trials. Unanswered questions regarding RSV epidemiology need to be identified and addressed prior to RSV vaccine introduction to guide the measurement of impact and future recommendations. The Centers for Disease Control and Prevention (CDC) convened a technical consultation to gather input from external subject matter experts on their individual perspectives regarding evidence gaps in current RSV epidemiology in the United States, potential studies and surveillance platforms needed to fill these gaps, and prioritizing efforts. Participants articulated their individual views, and CDC staff synthesized individuals' input into this report.

Angiostrongylus cantonensis Eosinophilic Meningitis in an Infant, Tennessee, USA.

Angiostrongylus cantonensis, the rat lungworm, is the most common infectious cause of eosinophilic meningoencephalitis worldwide. This parasite is endemic to Southeast Asia and the Pacific Islands, and its global distribution is increasing. We report A. cantonensis meningoencephalitis in a 12-month-old boy in Tennessee, USA, who had not traveled outside of southwestern Tennessee or northwestern Mississippi.

Preclinical Characterization of PC786, an Inhaled Small-Molecule Respiratory Syncytial Virus L Protein Polymerase Inhibitor.

Although respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants and young children, attempts to develop an effective therapy have so far proved unsuccessful. Here we report the preclinical profiles of PC786, a potent nonnucleoside RSV L protein polymerase inhibitor, designed for inhalation treatment of RSV infection. PC786 demonstrated a potent and selective antiviral activity against laboratory-adapted or clinical isolates of RSV-A (50% inhibitory concentration [IC50], <0.09 to 0.71 nM) and RSV-B (IC50, 1.3 to 50.6 nM), which were determined by inhibition of cytopathic effects in HEp-2 cells without causing detectable cytotoxicity. The underlying inhibition of virus replication was confirmed by PCR analysis. The effects of PC786 were largely unaffected by the multiplicity of infection (MOI) and were retained in the face of established RSV replication in a time-of-addition study. Persistent anti-RSV effects of PC786 were also demonstrated in human bronchial epithelial cells. In vivo intranasal once daily dosing with PC786 was able to reduce the virus load to undetectable levels in lung homogenates from RSV-infected mice and cotton rats. Treatment with escalating concentrations identified a dominant mutation in the L protein (Y1631H) in vitro In addition, PC786 potently inhibited RSV RNA-dependent RNA polymerase (RdRp) activity in a cell-free enzyme assay and minigenome assay in HEp-2 cells (IC50, 2.1 and 0.5 nM, respectively). Thus, PC786 was shown to be a potent anti-RSV agent via inhibition of RdRp activity, making topical treatment with this compound a novel potential therapy for the treatment of human RSV infections.

Oral GS-5806 activity in a respiratory syncytial virus challenge study.

BACKGROUND: Respiratory syncytial virus (RSV) is a common cause of infant hospitalizations and is increasingly recognized as a cause of considerable morbidity and mortality. No accepted antiviral treatment exists. METHODS: We conducted a double-blind, placebo-controlled study of GS-5806, an oral RSV-entry inhibitor, in healthy adults who received a clinical challenge strain of RSV intranasally. Participants were monitored for 12 days. At the time of a positive test for RSV infection or 5 days after inoculation, whichever occurred first, participants were randomly assigned to receive GS-5806 or placebo in one of seven sequential cohorts. Cohorts 1 to 4 received a first dose of 50 mg of GS-5806 and then 25 mg daily for the next 4 days, cohort 5 received a first dose of 50 mg and then 25 mg daily for the next 2 days, cohort 6 received one 100-mg dose, and cohort 7 received a first dose of 10 mg and then 5 mg daily for the next 4 days. Dose selection for cohorts 5, 6, and 7 occurred after an interim analysis of data for cohorts 1 to 4. The primary end point was the area under the curve (AUC) for the viral load, which was assessed after administration of the first dose through the 12th day after inoculation. Secondary end points were mucus weight and symptom scores. RESULTS: Among the 54 participants in cohorts 1 to 4 who were infected with RSV, active treatment was associated with a lower viral load (adjusted mean, 250.7 vs. 757.7 log10 plaque-forming-unit equivalents [PFUe] × hours per milliliter; P<0.001), lower total mucus weight (mean, 6.9 g vs. 15.1 g; P=0.03), and a lower AUC for the change from baseline in symptom scores (adjusted mean, -20.2 vs. 204.9 × hours; P=0.005). The results were similar in cohorts 5, 6, and 7. Adverse events, including low neutrophil counts and increased levels of alanine aminotransferase, were more common among participants receiving GS-5806. CONCLUSIONS: Treatment with GS-5806 reduced the viral load and the severity of clinical disease in a challenge study of healthy adults. (Funded by Gilead Sciences; ClinicalTrials.gov number, NCT01756482.).

Respiratory Syncytial Virus Disease Is Mediated by Age-Variable IL-33.

Respiratory syncytial virus (RSV) is the most common cause of infant hospitalizations and severe RSV infections are a significant risk factor for childhood asthma. The pathogenic mechanisms responsible for RSV induced immunopathophysiology remain elusive. Using an age-appropriate mouse model of RSV, we show that IL-33 plays a critical role in the immunopathogenesis of severe RSV, which is associated with higher group 2 innate lymphoid cells (ILC2s) specifically in neonates. Infection with RSV induced rapid IL-33 expression and an increase in ILC2 numbers in the lungs of neonatal mice; this was not observed in adult mice. Blocking IL-33 with antibodies or using an IL-33 receptor knockout mouse during infection was sufficient to inhibit RSV immunopathogenesis (i.e., airway hyperresponsiveness, Th2 inflammation, eosinophilia, and mucus hyperproduction); whereas administration of IL-33 to adult mice during RSV infection was sufficient to induce RSV disease. Additionally, elevated IL-33 and IL-13 were observed in nasal aspirates from infants hospitalized with RSV; these cytokines declined during convalescence. In summary, IL-33 is necessary, either directly or indirectly, to induce ILC2s and the Th2 biased immunopathophysiology observed following neonatal RSV infection. This study provides a mechanism involving IL-33 and ILC2s in RSV mediated human asthma.

Prolonged viral replication and longitudinal viral dynamic differences among respiratory syncytial virus infected infants.

BackgroundLongitudinal respiratory syncytial virus (RSV) dynamics have not been well studied despite the existence of factors favoring prolonged RSV replication including high mutation rates allowing rapid evolution and potential escape from immune control. We therefore measured viral load in previously RSV-naive infants over prolonged time spans.MethodsDuring 2014-2015, quantitative nasal aspirates were collected from 51 RSV-PCR+ infants. Multiple parallel assessments of viral loads were quantified at each collected time point using a well-validated real-time quantitative reverse transcriptase polymerase chain reaction assay. After observing viral load rebound phenomenon in some infants, the viral dynamics of 27 infants with sufficient longitudinal viral load data points were analyzed using the pre-defined criteria for viral rebound. Additional analyses were performed comparing age with viral rebound, viral clearance rates, and viral load area-under-the-curve (AUCVL).ResultsThe 51 infants (303 nasal aspirate samples; mean of 5.9 per patient) exhibited slower than expected viral clearance. Lower age trended toward slower viral clearance and greater AUCVL. Six infants had detectable viral loads ≥1 month after symptom onset. Ten of twenty-seven evaluable subjects exhibited viral rebound and this rebound was age-dependent (P=0.0259). All but one rebounder were <70 days old.ConclusionInfants struggle to control primary RSV infections allowing prolonged viral replication and previously undescribed viral rebound; likely representing viral mutational immune escape.