Prior respiratory syncytial virus infection reduces vaccine-mediated Th2-skewed immunity, but retains enhanced RSV F-specific CD8 T cell responses elicited by a Th1-skewing vaccine formulation

Mucosal vaccines with STING-agonist liposomal formulations inhibit RSV (respiratory syncytial virus) replication in cotton rats

Respiratory syncytial virus (RSV) is responsible for severe lower respiratory tract infections (LRTI) in immunocompromised individuals. While recent breakthroughs in vaccine design have led to approved vaccines for the elderly, these vaccines are all administered through the parenteral route. Vaccine administration through the mucosal route could protect the viral route of entry and can be advantageous over injected vaccines. There is however a lack of safe and efficacious mucosal adjuvants that can facilitate both mucosal and systemic immune responses. Here, we present preclinical data based on liposomal nanoparticles, NanoSTING, that encapsulate the endogenous STING-agonist 2'3'-cGAMP (cyclic guanosine adenosine monophosphate) as adjuvant for prefusion protein-based intranasal vaccines against RSV. NanoSTING significantly increased the immunogenicity of well-documented RSV prefusion protein antigens DS-CaV1, sc9-10 DS-CaV1, and SC-TM after a single intranasal dose, when compared to the protein-only and naked-cGAMP adjuvanted groups. Two doses of NanoSTING adjuvanted vaccines yielded robust secretory IgA titers at the mucosal surfaces and induced potent Th1 T-cell responses in the lungs of vaccinated mice. Both NanoSTING-sc9-10 DS-CaV1 and NanoSTING-SCTM vaccines protect against viral replication at the upper (nose) and lower (lung) respiratory tract of RSV-challenged cotton rats. The ability of our mucosal vaccines against RSV to elicit immunity in the respiratory tract can prevent the establishment of infection in individuals and potentially prevent disease transmission.

Trends and Dynamics of Respiratory Viruses in Hospitalized Children of Fuzhou: Insights Into the Impact of COVID-19 Pandemic Control Measures

Purpose

This study aimed to investigate the prevalence of common respiratory viruses among children with acute respiratory infections in Fuzhou from 2017 to 2023, considering the varying Corona Virus Disease 2019 (COVID-19) epidemic control measures in place.

Patients and Methods

This study retrospectively analyzed the detection of respiratory viruses in children diagnosed with acute respiratory infections at a tertiary hospital in Fuzhou during the study period. The analysis covers three distinct phases: Phase I (2017-2019), Phase II (2020-2022), and Phase III (2023). The subjects of this study included adenovirus (ADV), influenza A virus (Flu A), influenza B virus (Flu B), parainfluenza virus types 1, 2, and 3 (PIV-1, PIV-2, PIV-3), and respiratory syncytial virus (RSV).

Results

A total of 24,838 throat swab samples were collected, resulting in an overall positive detection rate of 17.87% (4439/24,838). The positive detection rates of respiratory viruses among hospitalized children in Phases I, II, and III were 18.51%, 18.27%, and 15.90%, respectively, demonstrating a statistically significant decreasing trend over the years (P < 0.001). Among the detected viruses, RSV, PIV-3, and Flu A were the most prevalent. RSV infections was most common in children under six years of age. Seasonal trends for Flu A, PIV-3, and RSV varied throughout the outbreak; specifically, the detection rate of Flu A increased during March and April in 2023, while RSV detection rebounded sharply from April to June. The incidence of mixed respiratory virus infections was 0.40% (100/24,838), the most common being PIV-3 and RSV.

Conclusion

Using COVID-19 safety rules has helped stop the spread of some viruses in kids. But these rules have not made much difference in how often RSV and PIV-3 viruses show up.

Mucosal Immunization with an Influenza Vector Carrying SARS-CoV-2 N Protein Protects Naïve Mice and Prevents Disease Enhancement in Seropositive Th2-Prone Mice

Background/Objectives: Intranasal vaccination enhances protection against respiratory viruses by providing stimuli to the immune system at the primary site of infection, promoting a balanced and effective response. Influenza vectors with truncated NS1 are a promising vaccine approach that ensures a pronounced local CD8+ T-cellular immune response. Here, we describe the protective and immunomodulating properties of an influenza vector FluVec-N carrying the C-terminal fragment of the SARS-CoV-2 nucleoprotein within a truncated NS1 open reading frame. Methods: We generated several FluVec-N recombinant vectors by reverse genetics and confirmed the vector's genetic stability, antigen expression in vitro, attenuation, and immunogenicity in a mouse model. We tested the protective potential of FluVec-N intranasal immunization in naïve mice and seropositive Th2-prone mice, primed with aluminium-adjuvanted inactivated SARS-CoV-2. Immune response in immunized and challenged mice was analyzed through serological methods and flow cytometry. Results: Double intranasal immunization of naïve mice with FluVec-N reduced weight loss and viral load in the lungs following infection with the SARS-CoV-2 beta variant. Mice primed with alum-adjuvanted inactivated coronavirus experienced substantial early weight loss and eosinophilia in the lungs during infection, demonstrating signs of enhanced disease. A single intranasal boost immunization with FluVec-N prevented the disease enhancement in primed mice by modulating the local immune response. Protection was associated with the formation of specific IgA and the early activation of virus-specific effector and resident CD8+ lymphocytes in mouse lungs. Conclusions: Our study supports the potential of immunization with influenza vector vaccines to prevent respiratory diseases and associated immunopathology.

Lung ILC2s are activated in BALB/c mice born to immunized mothers despite complete protection against respiratory syncytial virus

Activated lung ILC2s produce large quantities of IL-5 and IL-13 that contribute to eosinophilic inflammation and mucus production following respiratory syncytial virus infection (RSV). The current understanding of ILC2 activation during RSV infection, is that ILC2s are activated by alarmins, including IL-33, released from airway epithelial cells in response to viral-mediated damage. Thus, high levels of RSV neutralizing maternal antibody generated from maternal immunization would be expected to reduce IL-33 production and mitigate ILC2 activation. Here we report that lung ILC2s from mice born to RSV-immunized dams become activated despite undetectable RSV replication. We also report, for the first time, expression of activating and inhibitory Fcgamma receptors on ILC2s that are differentially expressed in offspring born to immunized versus unimmunized dams. Alternatively, ex vivo IL-33-mediated activation of ILC2s was mitigated following the addition of antibody: antigen immune complexes. Further studies are needed to confirm the role of Fcgamma receptor ligation by immune complexes as an alternative mechanism of ILC2 regulation in RSV-associated eosinophilic lung inflammation.

Recent advances in the prevention of respiratory syncytial virus in pediatrics

PURPOSE OF REVIEW

Respiratory syncytial virus (RSV) is a ubiquitous virus and the leading cause of pediatric hospitalization in the United States. Prevention strategies are key for reducing the burden of RSV. Several new agents aimed at preventing RSV in infants and children were FDA-approved in 2023, and many more are in the development pipeline. This review highlights new developments in RSV prevention in pediatric patients and the important safety considerations for clinical trials.

RECENT FINDINGS

Two new preventive therapies were FDA approved in 2023; a maternal vaccine (Abrysvo) and a mAb (Beyfortus) have both demonstrated reduction in medically attended lower respiratory tract infections in infants and children. Evaluation of ongoing clinical trials demonstrates that the field is expanding further to include direct immunization of infants and children utilizing a variety of delivery modalities. While these developments present the optimistic prospect of RSV prevention in a range of ages, acute and long-term risks must be carefully evaluated.

SUMMARY

Prevention of RSV is more accessible than ever, but careful consideration must be given to risks associated with new and developing prevention strategies. Rigor of clinical trials including longitudinal outcomes of agents in development and postmarketing surveillance of newly approved therapies will be of paramount importance to ensure long-term safety of new RSV prevention strategies.

Exacerbated lung inflammation following secondary RSV exposure is CD4+ T cell-dependent and is not mitigated in infant BALB/c mice born to PreF-vaccinated dams

Respiratory syncytial virus (RSV) is the leading cause of childhood hospitalizations due to bronchiolitis in children under 5 years of age. Moreover, severe RSV disease requiring hospitalization is associated with the subsequent development of wheezing and asthma. Due to the young age in which viral protection is needed and risk of vaccine enhanced disease following direct infant vaccination, current approaches aim to protect young children through maternal immunization strategies that boost neutralizing maternal antibody (matAb) levels. However, there is a scarcity of studies investigating the influence of maternal immunization on secondary immune responses to RSV in the offspring or whether the subsequent development of wheezing and asthma is mitigated. Toward this goal, our lab developed a murine model of maternal RSV vaccination and repeat RSV exposure to evaluate the changes in immune response and development of exacerbated lung inflammation on secondary RSV exposure in mice born to immunized dams. Despite complete protection following primary RSV exposure, offspring born to pre-fusion F (PreF)-vaccinated dams had exaggerated secondary ILC2 and Th2 responses, characterized by enhanced production of IL-4, IL-5, and IL-13. These enhanced type 2 cellular responses were associated with exaggerated airway eosinophilia and mucus hyperproduction upon re-exposure to RSV. Importantly, depletion of CD4+ T cells led to complete amelioration of the observed type 2 pathology on secondary RSV exposure. These unanticipated results highlight the need for additional studies that look beyond primary protection to better understand how maternal immunization shapes subsequent immune responses to repeat RSV exposure.

Immune escaping of the novel genotypes of human respiratory syncytial virus based on gene sequence variation

Purpose

Immune escaping from host herd immunity has been related to changes in viral genomic sequences. The study aimed to understand the diverse immune responses to different subtypes or genotypes of human respiratory syncytial virus (RSV) in pediatric patients.

Methods

The genomic sequences of different subtypes or RSV genotypes, isolated from Beijing patients, were sequenced and systematically analyzed. Specifically, the antiviral effects of Palivizumab and the cross-reactivity of human sera from RSV-positive patients to different subtypes or genotypes of RSV were determined. Then, the level of 38 cytokines and chemokines in respiratory and serum samples from RSV-positive patients was evaluated.

Results

The highest nucleotide and amino acid variations and the secondary and tertiary structure diversities among different subtypes or genotypes of RSV were found in G, especially for genotype ON1 with a 72bp-insertion compared to NA1 in subtype A, while more mutations of F protein were found in the NH-2 terminal, including the antigenic site II, the target of Palivizumab, containing one change N276S. Palivizumab inhibited subtype A with higher efficiency than subtype B and had stronger inhibitory effects on the reference strains than on isolated strains. However, RSV-positive sera had stronger inhibitory effects on the strains in the same subtypes or genotypes of RSV. The level of IFN-α2, IL-1α, and IL-1β in respiratory specimens from patients with NA1 was lower than those with ON1, while there were higher TNFα, IFNγ, IL-1α, and IL-1β in the first serum samples from patients with ON1 compared to those with BA9 of subtype B.

Conclusions

Diverse host immune responses were correlated with differential subtypes and genotypes of RSV in pediatric patients, demonstrating the impact of viral genetics on host immunity.