Recent Trends in RSV Immunoprophylaxis: Clinical Implications for the Infant

Risk Factors Associated with Severe RSV Infection in Infants: What Is the Role of Viral Co-Infections?

The respiratory syncytial virus (RSV) represents the leading cause of viral lower respiratory tract infections (LRTI) in children worldwide and is associated with significant morbidity and mortality rates. The clinical picture of an RSV infection differs substantially between patients, and the role of viral co-infections is poorly investigated. During two consecutive winter seasons from October 2018 until February 2020, we prospectively included children up to 2 years old presenting with an acute LRTI, both ambulatory and hospitalized. We collected clinical data and tested nasopharyngeal secretions for a panel of 16 different respiratory viruses with multiplex RT-qPCR. Disease severity was assessed with traditional clinical parameters and scoring systems. A total of 120 patients were included, of which 91.7% were RSV positive; 42.5% of RSV-positive patients had a co-infection with at least one other respiratory virus. We found that patients suffering from a single RSV infection had higher pediatric intensive care unit (PICU) admission rates (OR = 5.9, 95% CI = 1.53 to 22.74), longer duration of hospitalization (IRR = 1.25, 95% CI = 1.03 to 1.52), and a higher Bronchiolitis Risk of Admission Score (BRAS) (IRR = 1.31, 95% CI = 1.02 to 1.70) compared to patients with RSV co-infections. No significant difference was found in saturation on admission, O2 need, or ReSViNET-score. In our cohort, patients with a single RSV infection had increased disease severity compared to patients with RSV co-infections. This suggests that the presence of viral co-infections might influence the course of RSV bronchiolitis, but heterogeneity and small sample size in our study prevents us from drawing strong conclusions. IMPORTANCE RSV is worldwide the leading cause of serious airway infections. Up to 90% of children will be infected by the age of 2. RSV symptoms are mostly mild and typically mimic a common cold in older children and adolescents, but younger children can develop severe lower respiratory tract disease, and currently it is unclear why certain children develop severe disease while others do not. In this study, we found that children with a single RSV infection had a higher disease severity compared to patients with viral co-infections, suggesting that the presence of a viral co-infection could influence the course of an RSV bronchiolitis. As preventive and therapeutic options for RSV-associated disease are currently limited, this finding could potentially guide physicians to decide which patients might benefit from current or future treatment options early in the course of disease, and therefore, warrants further investigation.

A Candidate Therapeutic Monoclonal Antibody Inhibits Both HRSV and HMPV Replication in Mice

Human metapneumovirus (HMPV) and human respiratory virus (HRSV) are two leading causes of acute respiratory tract infection in young children. While there is no licensed drug against HMPV, the monoclonal antibody (mAb) Palivizumab is approved against HRSV for prophylaxis use only. Novel therapeutics against both viruses are therefore needed. Here, we describe the identification of human mAbs targeting these viruses by using flow cytometry-based cell sorting. One hundred and two antibodies were initially identified from flow cytometry-based cell sorting as binding to the fusion protein from HRSV, HMPV or both. Of those, 95 were successfully produced in plants, purified and characterized for binding activity by ELISA and neutralization assays as well as by inhibition of virus replication in mice. Twenty-two highly reactive mAbs targeting either HRSV or HMPV were isolated. Of these, three mAbs inhibited replication in vivo of a single virus while one mAb could reduce both HRSV and HMPV titers in the lung. Overall, this study identifies several human mAbs with virus-specific therapeutic potential and a unique mAb with inhibitory activities against both HRSV and HMPV.

Recent Progress in the Discovery and Development of Monoclonal Antibodies against Viral Infections

Monoclonal antibodies (mAbs), the new revolutionary class of medications, are fast becoming tools against various diseases thanks to a unique structure and function that allow them to bind highly specific targets or receptors. These specialized proteins can be produced in large quantities via the hybridoma technique introduced in 1975 or by means of modern technologies. Additional methods have been developed to generate mAbs with new biological properties such as humanized, chimeric, or murine. The inclusion of mAbs in therapeutic regimens is a major medical advance and will hopefully lead to significant improvements in infectious disease management. Since the first therapeutic mAb, muromonab-CD3, was approved by the U.S. Food and Drug Administration (FDA) in 1986, the list of approved mAbs and their clinical indications and applications have been proliferating. New technologies have been developed to modify the structure of mAbs, thereby increasing efficacy and improving delivery routes. Gene delivery technologies, such as non-viral synthetic plasmid DNA and messenger RNA vectors (DMabs or mRNA-encoded mAbs), built to express tailored mAb genes, might help overcome some of the challenges of mAb therapy, including production restrictions, cold-chain storage, transportation requirements, and expensive manufacturing and distribution processes. This paper reviews some of the recent developments in mAb discovery against viral infections and illustrates how mAbs can help to combat viral diseases and outbreaks.

Murine Neonatal Oxidant Lung Injury: NRF2-Dependent Predisposition to Adulthood Respiratory Viral Infection and Protection by Maternal Antioxidant

NRF2 protects against oxidant-associated airway disorders via cytoprotective gene induction. To examine if NRF2 is an important determinant of respiratory syncytial virus (RSV) susceptibility after neonate lung injury, Nrf2-deficient (Nrf2^−/−) and wild-type (Nrf2^+/+) mice neonatally exposed to hyperoxia were infected with RSV. To investigate the prenatal antioxidant effect on neonatal oxidative lung injury, time-pregnant Nrf2^−/− and Nrf2^+/+ mice were given an oral NRF2 agonist (sulforaphane) on embryonic days 11.5–17.5, and offspring were exposed to hyperoxia. Bronchoalveolar lavage and histopathologic analyses determined lung injury. cDNA microarray analyses were performed on placenta and neonatal lungs. RSV-induced pulmonary inflammation, injury, oxidation, and virus load were heightened in hyperoxia-exposed mice, and injury was more severe in hyperoxia-susceptible Nrf2^−/− mice than in Nrf2^+/+ mice. Maternal sulforaphane significantly alleviated hyperoxic lung injury in both neonate genotypes with more marked attenuation of severe neutrophilia, edema, oxidation, and alveolarization arrest in Nrf2^−/− mice. Prenatal sulforaphane altered different genes with similar defensive functions (e.g., inhibition of cell/perinatal death and inflammation, potentiation of angiogenesis/organ development) in both strains, indicating compensatory transcriptome changes in Nrf2^−/− mice. Conclusively, oxidative injury in underdeveloped lungs NRF2-dependently predisposed RSV susceptibility. In utero sulforaphane intervention suggested NRF2-dependent and -independent pulmonary protection mechanisms against early-life oxidant injury.

Alveolar-like Macrophages Attenuate Respiratory Syncytial Virus Infection

Respiratory Syncytial Virus (RSV) is the leading cause of acute lower respiratory infections in young children and infection has been linked to the development of persistent lung disease in the form of wheezing and asthma. Despite substantial research efforts, there are no RSV vaccines currently available and an effective monoclonal antibody targeting the RSV fusion protein (palivizumab) is of limited general use given the associated expense. Therefore, the development of novel approaches to prevent RSV infection is highly desirable to improve pediatric health globally. We have developed a method to generate alveolar-like macrophages (ALMs) from pluripotent stem cells. These ALMs have shown potential to promote airway innate immunity and tissue repair and so we hypothesized that ALMs could be used as a strategy to prevent RSV infection. Here, we demonstrate that ALMs are not productively infected by RSV and prevent the infection of epithelial cells. Prevention of epithelial infection was mediated by two different mechanisms: phagocytosis of RSV particles and release of an antiviral soluble factor different from type I interferon. Furthermore, intratracheal administration of ALMs protected mice from subsequent virus-induced weight loss and decreased lung viral titres and inflammation, indicating that ALMs can impair the pathogenesis of RSV infection. Our results support a prophylactic role for ALMs in the setting of RSV infection and warrant further studies on stem cell-derived ALMs as a novel cell-based therapy for pulmonary viral infections.

Preventive Strategies for Respiratory Syncytial Virus Infection in Young Infants

Respiratory syncytial virus (RSV) is the leading cause of acute viral lower respiratory tract infections in young children, with the peak of severe disease occurring in infants younger than 6 months of age. Most infants who develop severe RSV infection are born full-term and previously healthy; however, premature infants represent an especially vulnerable population at high risk of developing serious sequelae because of RSV. Despite the high disease burden, the pathogenesis of the disease is not completely understood, treatment options are limited to supportive care, and no licensed vaccines are available.The young age of children affected by severe disease and incomplete understanding of the disease pathogenesis, along with prior vaccine failures, have represented major obstacles to RSV vaccine development. Nevertheless, the increasingly recognized burden associated with RSV in low-middle income countries, where RSV represents the second cause of infant mortality, has made the development of preventive strategies for RSV a global health priority. Increased awareness, together with a better understanding of the viral structure and identification of new viral targets, has led to the development of newer RSV vaccines and monoclonal antibodies to confer protection to both preterm and term infants who represent the most vulnerable population for severe RSV disease.

Monoclonal Antibodies for Prevention of Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is the leading cause of hospitalizations in infants worldwide. Palivizumab, a humanized monoclonal antibody against the RSV F protein, is the only licensed agent for prevention of severe RSV infection in high-risk infants. Palivizumab is administered intramuscularly, every month during the RSV season, usually 5 doses are required. In recent years, the resolution of the structure of the RSV F protein, with identification of potent neutralizing epitopes, and new technologies for production of monoclonal antibodies (mAbs) have facilitated the development of new alternative strategies for the prevention of RSV infections. One promising approach is a new generation of mAbs directed to new neutralizing epitopes and with prolonged half life. These enhanced mAbs are expected to provide adequate protection during the complete RSV season with a single intramuscular (IM) dose. The long-term goal of this approach is to provide passive immunization for the prevention of RSV lower respiratory tract infection to all infants (preterm and full term) in the first months of life before their initial exposure to RSV.

Immunogenicity and efficacy of mRNA COVID-19 vaccine MRT5500 in preclinical animal models

Emergency use authorization of COVID vaccines has brought hope to mitigate pandemic of coronavirus disease 2019 (COVID-19). However, there remains a need for additional effective vaccines to meet the global demand and address the potential new viral variants. mRNA technologies offer an expeditious path alternative to traditional vaccine approaches. Here we describe the efforts to utilize an mRNA platform for rational design and evaluations of mRNA vaccine candidates based on the spike (S) glycoprotein of SARS-CoV-2. Several mRNA constructs of S-protein, including wild type, a pre-fusion stabilized mutant (2P), a furin cleavage-site mutant (GSAS) and a double mutant form (2P/GSAS), as well as others, were tested in animal models for their capacity to elicit neutralizing antibodies (nAbs). The lead 2P/GSAS candidate was further assessed in dose-ranging studies in mice and Cynomolgus macaques, and for efficacy in a Syrian golden hamster model. The selected 2P/GSAS vaccine formulation, designated MRT5500, elicited potent nAbs as measured in neutralization assays in all three preclinical models and more importantly, protected against SARS-CoV-2-induced weight loss and lung pathology in hamsters. In addition, MRT5500 elicited T_H1-biased responses in both mouse and non-human primate (NHP), thus alleviating a hypothetical concern of potential vaccine-associated enhanced respiratory diseases known associated with T_H2-biased responses. These data position MRT5500 as a viable vaccine candidate for entering clinical development.

Saudi experts' recommendation for RSV prophylaxis in the era of COVID-19: Consensus from the Saudi Pediatric Pulmonology Association

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis and viral pneumonia in pediatrics worldwide. In the Kingdom of Saudi Arabia (KSA), the prevalence of RSV is 23.5% in pediatric patients with acute lower respiratory tract illness. Coronavirus disease (COVID-19) poses critical public health and socioeconomic challenges in KSA. The Saudi Pediatric Pulmonology Association (SPPA), a subsidiary of the Saudi Thoracic Society (STS), developed a task force to determine the potential challenges and barriers to the RSV immunoprophylaxis program during the era of COVID-19 and to compose a practical, nationwide, and multidisciplinary approach to address these challenges. Some of the recommendations to manage these challenges include increasing the number of RSV immunoprophylaxis clinics, drive-thru visits, home-care services, and swift referrals to the RSV immunoprophylaxis program specialists. Additional training is required for healthcare personnel to add RSV immunoprophylaxis to the regular immunization schedule.

The journey to a respiratory syncytial virus vaccine

OBJECTIVE

The high burden associated with respiratory syncytial virus (RSV) has made the development of RSV vaccine(s) a global health high priority. This review summarizes the journey to an RSV vaccine, the different strategies and challenges associated with the development of preventive strategies for RSV, and the diverse products that are undergoing clinical testing.

DATA SOURCES

Studies on RSV biology, immunology, epidemiology, and monoclonal antibodies (mAbs) and vaccines were searched using MEDLINE. We also searched PATH.org and ClinicalTrials.gov for updated information regarding the status of RSV vaccines and mAbs undergoing clinical trials.

STUDY SELECTIONS

We selected relevant studies conducted in infants and young children, pregnant women, and elderly population for the prevention of RSV infection.

RESULTS

Identification of a safe and immunogenic vaccine has been an important but elusive initiative for more than 60 years for different reasons, including the legacy of formalin-inactivated vaccine, our limited understanding of the immune response to RSV and how it relates to clinical disease severity, or the need for different end points according to the different vaccine platforms. Nevertheless, there are currently 39 vaccines and mAbs under development and 19 undergoing clinical trials.

CONCLUSION

Over the past decade, there have been significant advances in our knowledge of RSV molecular and structural biology and in understanding the human immune response to RSV. Despite the barriers, there are several promising mAbs and RSV vaccines undergoing clinical trials that hope to offer protection to the most vulnerable populations.

Emerging small and large molecule therapeutics for respiratory syncytial virus

Introduction: Respiratory syncytial virus (RSV) causes lower respiratory tract infections and can lead to morbidity and mortality in the infant, elderly and immunocompromised. There is no vaccine and therapeutic interventions are limited. RSV disease research has yielded the development of several prophylactic and therapeutic treatments. Several promising candidates are currently under investigation.Areas covered: Small and large molecule approaches to RSV treatment were examined and categorized by their mechanism of action using data from PubMed, clinicaltrials.gov, and from the sponsoring organizations publicly available pipeline information. These results are prefaced by an overview of RSV to provide the context for rational therapy development.Expert opinion: While small molecule drugs show promise for RSV treatment, we believe that large molecule therapy using anti-RSV G and F protein monoclonal antibodies (mAbs) will most efficaciously and safely ameliorate RSV disease.

Rhein Suppresses Lung Inflammatory Injury Induced by Human Respiratory Syncytial Virus Through Inhibiting NLRP3 Inflammasome Activation via NF-κB Pathway in Mice

Rhein is one of active anthraquinone components in traditional Chinese herbal medicine Rheum palmatum L., possessing anti-inflammatory, antioxidant, antitumor, antiviral, and hepatoprotective activities. Human respiratory syncytial virus (RSV), a common virus, is able to result in pneumonia and bronchitis, which usually can be seen in infants. However, so far the effects of Rhein on RSV-induced pneumonia are still unknown. As the NLRP3 inflammasome is activated excessively, it is able to lead to inflammatory response and tissue injury in most viral infection process (including RSV infection) of respiratory tract. Therefore, we designed experiments to reveal whether Rhein can treat RSV-induced pneumonia by inhibiting NLRP3 inflammasome activation. In present research, we established the pneumonia model of BALB/C mice caused by RSV. First of all, the pathology of lung tissue and the weight of mice were evaluated, and the corresponding lung index was calculated. Additionally, the expression of pro-inflammatory mediators in serum and lung tissues, and related proteins (NLRP3, ASC and Caspase-1) of NLRP3 inflammasome and NF-κB pathway were detected by Enzyme-linked immunosorbent assay (ELISA), Real-time PCR (RT-PCR), Immunohistochemistry (IHC), and Western blot (WB), respectively. The determination of lung index and lung tissue pathological evaluation revealed that Rhein was able to alleviate lung infection and injury caused by RSV. The results of ELISA showed that Rhein was able to reduce the release of pro-inflammatory cytokines in the serum and lung tissues of RSV-induced BALB/c mice, including IL-1β, IL-6, TNF-α, IL-18, and IL-33. Additionally, it was revealed that Rhein inhibited the immune inflammatory response of RSV-infected mice, which was likely to be associated with the inhibition the NLRP3 inflammasome activation via NF-κB pathway. To sum up, our results indicated that Rhein may inhibit RSV-induced pulmonary inflammatory response effectively; meanwhile, it is emphasized that Rhein therapy is likely to be a promising treatment on the RSV-infected lung inflammation and avoidance of lung tissue damage.