Respiratory syncytial virus, recurrent wheeze and asthma: A narrative review of pathophysiology, prevention and future directions

Confronting the challenge: a regional perspective by the Latin American pediatric infectious diseases society (SLIPE) expert group on respiratory syncytial virus-tackling the burden of disease and implementing preventive solutions

Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory infections in children around the world. The post-pandemic era has resulted in a notable increase in reported cases of RSV infections, co-circulation of other respiratory viruses, shifts in epidemiology, altered respiratory season timing, and increased healthcare demand. Low- and middle-income countries are responsible for the highest burden of RSV disease, contributing significantly to health expenses during respiratory seasons and RSV-associated mortality in children. Until recently, supportive measures were the only intervention to treat or prevent RSV-infection, since preventive strategies like palivizumab are limited for high-risk populations. Advances in new available strategies, such as long-acting monoclonal antibodies during the neonatal period and vaccination of pregnant women, are now a reality. As the Regional Expert Group of the Latin American Pediatric Infectious Diseases Society (SLIPE), we sought to evaluate the burden of RSV infection in Latin America and the Caribbean (LAC) region, analyze current strategies to prevent RSV infection in children, and provide recommendations for implementing new strategies for preventing RSV infection in children in LAC region.

Helminth induced monocytosis conveys protection from respiratory syncytial virus infection in mice

BACKGROUND

Respiratory syncytial virus (RSV) infection in infants is a major cause of viral bronchiolitis and hospitalisation. We have previously shown in a murine model that ongoing infection with the gut helminth Heligmosomoides polygyrus protects against RSV infection through type I interferon (IFN-I) dependent reduction of viral load. Yet, the cellular basis for this protection has remained elusive. Given that recruitment of mononuclear phagocytes to the lung is critical for early RSV infection control, we assessed their role in this coinfection model.

METHODS

Mice were infected by oral gavage with H. polygyrus. Myeloid immune cell populations were assessed by flow cytometry in lung, blood and bone marrow throughout infection and after secondary infection with RSV. Monocyte numbers were depleted by anti-CCR2 antibody or increased by intravenous transfer of enriched monocytes.

RESULTS

H. polygyrus infection induces bone marrow monopoiesis, increasing circulatory monocytes and lung mononuclear phagocytes in a IFN-I signalling dependent manner. This expansion causes enhanced lung mononuclear phagocyte counts early in RSV infection that may contribute to the reduction of RSV load. Depletion or supplementation of circulatory monocytes prior to RSV infection confirms that these are both necessary and sufficient for helminth induced antiviral protection.

CONCLUSIONS

H. polygyrus infection induces systemic monocytosis contributing to elevated mononuclear phagocyte numbers in the lung. These cells are central to an anti-viral effect that reduces the peak viral load in RSV infection. Treatments to promote or modulate these cells may provide novel paths to control RSV infection in high risk individuals.

Human Milk Oligosaccharides and Respiratory Syncytial Virus Infection in Infants

In infants worldwide, respiratory syncytial virus (RSV) is the leading cause of lower respiratory infections, including bronchiolitis, which is a major source of infant mortality. Bronchiolitis is the most common lower respiratory infection and the major cause of hospitalization in the first 6 mo of life. Infant responses to RSV infection are highly diverse, with symptoms varying from asymptomatic or mild to so severe as to require mechanical ventilation. Breastfed infants present a lower incidence and less severe forms of RSV lower respiratory infections. Among the multitude of human milk bioactive compounds, human milk oligosaccharides (hMOSs) are strong candidates for having a protective effect against RSV. hMOS reduces the viral load and the inflammatory signaling in cultured RSV-infected respiratory human cells. In addition to this direct effect, indirect mechanisms, notably gut microbiota composition and metabolism, have been proposed to mediate the protective effect of hMOS. Intake of infant formula containing synthetic hMOS has been shown to increase Bifidobacterium abundance and that of its metabolites, especially acetate, in infant feces and to reduce lower respiratory tract infections during the first year of life. Breastfeeding and the use of hMOS are promising approaches to protect against and treat RSV disease. Here, we review current evidence on the role of hMOS with regard to RSV infection and disease, attending to knowledge gaps and future research directions.

Towards personalized medicine for the treatment of equine asthma

Although horses with asthma share similar clinical signs, the heterogeneity of the disease in terms of severity, triggering factors, inflammatory profile, and pathological features has hindered our ability to define biologically distinct subgroups. The recognition of phenotypes and endotypes could enable the development of precision medicine, including personalized, targeted therapy, to benefit affected horses. While in its infancy in horses, this review outlines the phenotypes of equine asthma and discusses how knowledge gained from targeted therapy in human medicine can be applied to evaluate the potential opportunities for personalized medicine in equine asthma and to suggest avenues for research to advance this emerging field.

New Vaccines for Chronic Respiratory Patients

Chronic respiratory diseases (CRD) are responsible for more than four million deaths worldwide and have become especially prevalent in developed countries. Although the current therapies help manage daily symptoms and improve patients' quality of life, there is a major need to prevent exacerbations triggered mainly by respiratory infections. Therefore, CRD patients are a prime target for vaccination against infectious agents. In the present manuscript we review the state of the art of available vaccines specifically indicated in patients with CRDs. In addition to pneumococcus, influenza, pertussis, and SARS-CoV-2 vaccines, recently added immunization options like vaccines and monoclonal antibodies against respiratory syncytial virus, are particularly interesting in CRD patients. As new products reach the market, health authorities must be agile in updating immunization recommendations and in the programming of the vaccination of vulnerable populations such as patients with CRDs. Organizational and educational strategies might prove useful to increase vaccine uptake by CRD patients.

The full value of immunisation against respiratory syncytial virus for infants younger than 1 year: effects beyond prevention of acute respiratory illness

Respiratory syncytial virus (RSV) is a leading cause of severe respiratory illness and death among children worldwide, particularly in children younger than 6 months and in low-income and middle-income countries. Feasible and cost-effective interventions to prevent RSV disease are not yet widely available, although two new products aimed at preventing RSV disease-long-acting monoclonal antibodies and maternal vaccines-have been licensed within the past 2 years. The primary target of these products is reduction of the substantial burden of RSV-associated acute lower respiratory tract infections (LRTI) in infants younger than 1 year. However, other important public health benefits might also accrue with the prevention of RSV-associated LRTI during the first year of life. Mounting evidence shows that preventing RSV-associated LRTI in infants younger than 1 year could prevent secondary pneumonia caused by other pathogens, reduce recurrent hospitalisations due to other respiratory diseases in later childhood, decrease all-cause infant mortality, ameliorate the burden of respiratory diseases on health-care systems, reduce inappropriate antibiotic use, and possibly improve lung health beyond infancy. We herein review current evidence and suggest approaches to better assess the magnitude of these potential secondary effects of RSV prevention, which, if proven substantial, are likely to be relevant to policy makers in many countries as they consider the use of these new products.

RSV Disease Burden in Primary Care in Italy: A Multi-Region Pediatric Study, Winter Season 2022-2023

INTRODUCTION

Human respiratory syncytial virus (RSV) is one of the most frequent causes of respiratory infections in children under 5 years of age, but its socioeconomic impact and burden in primary care settings is still little studied.

METHODS

During the 2022/2023 winter season, 55 pediatricians from five Italian regions participated in our community-based study. They collected a nasal swab for RSV molecular test from 650 patients under the age of 5 with acute respiratory infections (ARIs) and performed a baseline questionnaire. The clinical and socioeconomic burden of RSV disease in primary care was evaluated by two follow-up questionnaires completed by the parents of positive children on Days 14 and 30.

RESULTS

RSV laboratory-confirmed cases were 37.8% of the total recruited ARI cases, with RSV subtype B accounting for the majority (65.4%) of RSV-positive swabs. RSV-positive children were younger than RSV-negative ones (median 12.5 vs. 16.5 months). The mean duration of symptoms for all children infected by RSV was 11.47 ± 6.27 days. We did not observe substantial differences in clinical severity between the two RSV subtypes, but RSV-A positive patients required more additional pediatric examinations than RSV-B cases. The socioeconomic impact of RSV infection was considerable, causing 53% of children to be absent from school, 46% of parents to lose working days, and 25% of families to incur extra costs.

CONCLUSIONS

Our findings describe a baseline of the RSV disease burden in primary care in Italy before the introduction of upcoming immunization strategies.

Innate Lymphoid Cells and Their Role in the Immune Response to Infections

Over the past decade, a group of lymphocyte-like cells called innate lymphoid cells (ILCs) has gained considerable attention due to their crucial role in regulating immunity and tissue homeostasis. ILCs, lacking antigen-specific receptors, are a group of functionally differentiated effector cells that act as tissue-resident sentinels against infections. Numerous studies have elucidated the characteristics of ILC subgroups, but the mechanisms controlling protective or pathological responses to pathogens still need to be better understood. This review summarizes the functions of ILCs in the immunology of infections caused by different intracellular and extracellular pathogens and discusses their possible therapeutic potential.

Clinical Predictors of Severe Exacerbations in Pediatric Patients With Recurrent Wheezing

Introduction Wheezing is common in preschool-aged children, affecting about half of all children within their first six years of life. Children who have recurrent wheezing experience disease-related morbidity, including increased emergency visits and hospitalizations. Early-life lower respiratory tract viral infections are linked to recurrent wheezing and eventual asthma onset. Identifying high-risk children is crucial, with the frequency and severity of wheezing episodes being good predictors of long-term outcomes. Aim To identify predictors of severe exacerbations in children with recurrent wheezing. Methods We conducted a retrospective cohort study involving 168 pediatric patients with recurrent wheezing followed up at our outpatient clinic. The outcome of interest was the occurrence of a severe exacerbation, defined as any exacerbation requiring hospitalization and the need for supplemental oxygenation or ventilatory support. Results The median age of the first wheezing exacerbation was five months, with a predominance of the male gender. Approximately two-thirds of the patients had a family history of atopy. Comorbid allergic rhinitis and atopic dermatitis were present in 15.4% and 16.7% of patients, respectively. Twenty percent of patients had a severe wheezing exacerbation as the first form of presentation, and 30% presented at least one severe exacerbation from the first presentation to the last follow-up. Patients with severe exacerbations were younger at the first episode (median age 4 months, IQR 2-7, versus 7 months, IQR 4-12, p=0.027) and more frequently had a family history of atopy (71.7% versus 55.6%, p=0.050). In this cohort, patients who initially presented with a severe episode are at increased risk of incident severe exacerbations during follow-up, HR 2.24 (95%CI 1.01-4.95). Conclusions We know that the severity of exacerbations in children with recurrent wheezing correlates with the long-term outcomes of the disease. Therefore, preventing severe exacerbations can positively impact the prognosis of these patients. In this analysis, we found independent predictors of severe exacerbations to be the first clinical episode before the age of three months and a family history of atopy. We also found that patients whose initial presentation was severe have a higher risk of new severe exacerbations. Therefore, these subgroups of patients should be closely monitored by pediatricians.

Comparing the Clinical Courses of Children With Human Rhinovirus/Enterovirus to Children With Other Respiratory Viruses in the Outpatient Setting

BACKGROUND

While infections caused by rhinoviruses and enteroviruses are common among children, the entirety of their clinical impact remains elusive. We compared the clinical outcomes of children with rhinovirus/enterovirus infections to other common respiratory viruses in outpatient settings.

METHODS

We conducted a retrospective analysis of nasopharyngeal samples singly positive for human rhinovirus/enterovirus (HRV/ENT), influenza A/B (FLU) or respiratory syncytial virus (RSV) from patients ≤17 years submitted for clinical testing via multiplex polymerase chain reaction between 2016 and 2019. We evaluated the following outpatient outcomes: days of respiratory symptoms before testing; visits for respiratory symptoms; receipt of a breathing treatment; receipt of antibiotics and hospital admission. Statistical analyses were conducted controlling for age and comorbid conditions.

RESULTS

There were 1355 positive samples included in this analysis (HRV/ENT: n = 743, FLU: n = 303 and RSV: n = 309). Compared to HRV/ENT, children with FLU had 28% fewer days of respiratory symptoms (β: -0.32; 95% confidence interval: -0.46 to -0.18; P < 0.001), fewer visits for respiratory symptoms, and significantly decreased odds of receiving a breathing treatment or antibiotics, and admission to the hospital. Children with RSV had a similar number of days of respiratory symptoms, outpatient visits and odds of hospital admission, but significantly increased odds of receiving a breathing treatment and antibiotics compared to those with HRV/ENT.

CONCLUSION

Clinicians should have a high level of vigilance when managing children with positive respiratory viral testing for HRV/ENT given the potential for clinical outcomes similar to and, in some instances, worse than known highly pathogenic viruses.

New Insights on Respiratory Syncytial Virus Prevention

Respiratory syncytial virus (RSV) is a well-known infant pathogen transmitted mainly by droplets. It is a leading cause of upper respiratory tract infections in children, usually with a mild course of illness. RSV has also been a threat to older people, especially those with underlying medical conditions. For a long time, prevention was limited to passive immunoprophylaxis with palivizumab for high-risk infants. There was a strong need to find other treatment or prevention methods against RSV infections. In addition, after the coronavirus disease 2019 (COVID-19) pandemic, some significant changes in RSV epidemiology have been observed. Researchers noticed the shift in RSV seasonality and age distribution and the increased number of cases in older infants and adults. All of these made the need to find other medical options even stronger. Fortunately, two protein-based vaccines against RSV have successfully passed all phases of clinical trials and have been approved for use by adults and older people. One of them is also approved for infants from birth to 6 months of age (after maternal immunisation during pregnancy) and for pregnant women between 24 and 36 weeks of pregnancy. Also, a new passive immunisation option named nirsevimab (a highly potent monoclonal antibody with a long half-life) is now available for the paediatric group. In this review, we will discuss the previous and current RSV prevention methods in the light of structural discoveries of RSV antigens.

2022 Year in Review: Pediatric Asthma

Asthma is the most common chronic disease in children. Asthma is a heterogeneous disease characterized by variable, reversible airway obstruction and hyper-responsive airways. There is a high economic burden due to a child having poorly controlled asthma with one or more asthma exacerbations resulting in an emergency department visit or hospitalization in a year. Publications on diagnosis, treatment, and management of pediatric asthma are ongoing with over 2,549 papers published from January-November 2022. The intent of this paper is to summarize 8 key topics that have prompted discussions with local, regional, and national asthma experts due to a shift in clinical practice or lessons learned from the recent pandemic that may have future application.

The dysfunction of Tfh cells promotes pediatric recurrent respiratory tract infections development by interfering humoral immune responses

Recurrent respiratory tract infections (RRTIs) are one of the most common pediatric diseases. Although the pathogenesis of pediatric RRTIs remains unknown, ineffective B cell-dominated humoral immunity has been considered as the core mechanism. During the course of pediatric RRTIs, B cell-dominated humoral immunity has changed from "protector" of respiratory system to "bystander" of respiratory tract infections. Under physiological condition, Tfh cells are essential for B cell-dominated humoral immunity, including regulating GC formation, promoting memory B cell (MB)/plasma cell (PC) differentiation, inducting immunoglobulin (Ig) class switching, and selecting affinity-matured antibodies. However, in disease states, Tfh cells are dysfunctional, which can be reflected by phenotypes and cytokine production. Tfh cell dysfunctions can cause the disorders of B cell-dominated humoral immunity, such as promoting B cell presented apoptosis, abrogating total Ig production, reducing MB/PC populations, and delaying affinity maturation of antigens-specific antibodies. In this review, we focused on the functions of B and Tfh cells in the homeostasis of respiratory system, and specifically discussed the disorders of humoral immunity and aberrant Tfh cell responses in the disease process of pediatric RRTIs. We hoped to provide some clues for the prevention and treatment of pediatric RRTIs.

Natural killer cells in the lung: potential role in asthma and virus-induced exacerbation?

Asthma is a chronic inflammatory airway disorder whose pathophysiological and immunological mechanisms are not completely understood. Asthma exacerbations are mostly driven by respiratory viral infections and characterised by worsening of symptoms. Despite current therapies, asthma exacerbations can still be life-threatening. Natural killer (NK) cells are innate lymphoid cells well known for their antiviral activity and are present in the lung as circulating and resident cells. However, their functions in asthma and its exacerbations are still unclear. In this review, we will address NK cell activation and functions, which are particularly relevant for asthma and virus-induced asthma exacerbations. Then, the role of NK cells in the lungs at homeostasis in healthy individuals will be described, as well as their functions during pulmonary viral infections, with an emphasis on those associated with asthma exacerbations. Finally, we will discuss the involvement of NK cells in asthma and virus-induced exacerbations and examine the effect of asthma treatments on NK cells.

Advances in the Relationship between Respiratory Viruses and Asthma

Several studies have reported that viral infection is closely associated with the onset, progression, and exacerbation of asthma. The purpose of this review is to summarize the role that viral infections have in the pathogenesis of asthma onset and exacerbations, as well as discuss interrelated protective and risk factors of asthma and current treatment options. Furthermore, we present current knowledge of the innate immunological pathways driving host defense, including changes in the epithelial barrier. In addition, we highlight the importance of the genetics and epigenetics of asthma and virus susceptibility. Moreover, the involvement of virus etiology from bronchiolitis and childhood wheezing to asthma is described. The characterization and mechanisms of action of the respiratory viruses most frequently related to asthma are mentioned.

Back to the Basics: Usefulness of Naturally Aged Mouse Models and Immunohistochemical and Quantitative Morphologic Methods in Studying Mechanisms of Lung Aging and Associated Diseases

Aging-related molecular and cellular alterations in the lung contribute to an increased susceptibility of the elderly to devastating diseases. Although the study of the aging process in the lung may benefit from the use of genetically modified mouse models and omics techniques, these approaches are still not available to most researchers and produce complex results. In this article, we review works that used naturally aged mouse models, together with immunohistochemistry (IHC) and quantitative morphologic (QM) methods in the study of the mechanisms of the aging process in the lung and its most commonly associated disorders: cancer, chronic obstructive pulmonary disease (COPD), and infectious diseases. The advantage of using naturally aged mice is that they present characteristics similar to those observed in human aging. The advantage of using IHC and QM methods lies in their simplicity, economic accessibility, and easy interpretation, in addition to the fact that they provide extremely important information. The study of the aging process in the lung and its associated diseases could allow the design of appropriate therapeutic strategies, which is extremely important considering that life expectancy and the number of elderly people continue to increase considerably worldwide.

Surveillance of Influenza and Other Airborne Transmission Viruses during the 2021/2022 Season in Hospitalized Subjects in Tuscany, Italy

Winter in the northern hemisphere is characterized by the circulation of influenza viruses, which cause seasonal epidemics, generally from October to April. Each influenza season has its own pattern, which differs from one year to the next in terms of the first influenza case notification, the period of highest incidence, and the predominant influenza virus subtypes. After the total absence of influenza viruses in the 2020/2021 season, cases of influenza were again recorded in the 2021/2022 season, although they remained below the seasonal average. Moreover, the co-circulation of the influenza virus and the SARS-CoV-2 pandemic virus was also reported. In the context of the DRIVE study, oropharyngeal swabs were collected from 129 Tuscan adults hospitalized for severe acute respiratory infection (SARI) and analyzed by means of real-time polymerase chain reaction (RT-PCR) for SARS-CoV-2 and 21 different airborne pathogens, including influenza viruses. In total, 55 subjects tested positive for COVID-19, 9 tested positive for influenza, and 3 tested positive for both SARS-CoV-2 and the A/H3N2 influenza virus. The co-circulation of different viruses in the population requires strengthened surveillance that is no longer restricted to the winter months. Indeed, constant, year-long monitoring of the trends of these viruses is needed, especially in at-risk groups and elderly people.

Respiratory Syncytial Virus Infection: Treatments and Clinical Management

Respiratory syncytial virus (RSV) is a major healthcare concern, especially for immune-compromised individuals and infants below 5 years of age. Worldwide, it is known to be associated with incidences of morbidity and mortality in infants. Despite the seriousness of the issue and continuous rigorous scientific efforts, no approved vaccine or available drug is fully effective against RSV. The purpose of this review article is to provide insights into the past and ongoing efforts for securing effective vaccines and therapeutics against RSV. The readers will be able to confer the mechanism of existing therapies and the loopholes that need to be overcome for future therapeutic development against RSV. A methodological approach was applied to collect the latest data and updated results regarding therapeutics and vaccine development against RSV. We outline the latest throughput vaccination technologies and prophylactic development efforts linked with RSV. A range of vaccination approaches with the already available vaccine (with limited use) and those undergoing trials are included. Moreover, important drug regimens used alone or in conjugation with adjuvants or vaccines are also briefly discussed. After reading this article, the audience will be able to understand the current standing of clinical management in the form of the vaccine, prophylactic, and therapeutic candidates against RSV. An understanding of the biological behavior acting as a reason behind the lack of effective therapeutics against RSV will also be developed. The literature indicates a need to overcome the limitations attached to RSV clinical management, drugs, and vaccine development that could be explained by dealing with the challenges of current study designs with continuous improvement and further work and approval on novel therapeutic applications.

Prevention and Treatment Strategies for Respiratory Syncytial Virus (RSV)

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract disease, especially in young children. Despite its global impact on healthcare, related to its high prevalence and its association with significant morbidity, the current therapy is still mostly supportive. Moreover, while more than 50 years have passed since the first trial of an RSV vaccine (which unfortunately caused enhanced RSV disease), no vaccine has been approved for RSV prevention. In the last two decades, our understanding of the pathogenesis and immunopathology of RSV have continued to evolve, leading to significant advancements in RSV prevention strategies. These include both the development of new potential vaccines and the successful implementation of passive immunization, which, together, will provide coverage from infancy to old age. In this review, we provide an update of the current treatment options for acute disease (RSV-specific and -non-specific) and different therapeutic approaches focusing on RSV prevention.