Evolution of protection after maternal immunization for respiratory syncytial virus in cotton rats

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.

Estimating the prevalence of six common respiratory viral infections in Zhangzhou, China using nasopharyngeal swabs in adults and throat swabs in Children

Acute respiratory viral infections are a major public health concern worldwide, causing significant morbidity and economic burden. Understanding the epidemiological characteristics of these infections is crucial for effective control and prevention measures. The study aimed to investigate the epidemiology of six common respiratory viral infections in Zhangzhou, Fujian Province, China. Clinical and demographic information, along with throat swabs from children and nasopharyngeal swabs from adults, were collected from 19,523 patients from Jan 2023 to Aug 2024 in Zhangzhou, Fujian Province, China. Multiplex RT-PCR was performed to detected six respiratory viral pathogens. At least one virus was detected in 6911 cases, the positivity rate was 35.40%. A total of 440 cases of mixed infection with two or more viruses were detected, and the positivity rate of co-infection was 2.25%. Age-specific analysis revealed that RSV predominantly affected children aged 0-3 years, while FluA had a broader age distribution, with significant incidences in elderly (≥ 60 years old). Seasonal peaks in viral detection were observed in Mar and Jul 2023, as well as Apr 2024. Overall, there was no statistically significant difference in viral detection rates between sexes, with the exception of the 6-14 years age group, where males exhibited a higher rate. Co-infections were more prevalent during the summer months and were particularly common among children aged 1-3 years. The study highlights the distinct age, sex, and seasonal patterns of six common respiratory viral infections in Zhangzhou, China. These findings emphasize the need for targeted age-specific and seasonal public health interventions to effectively prevent and control these infections.

The Development of Animal Models for Respiratory Syncytial Virus (RSV) Infection and Enhanced RSV Disease

The development of immunoprophylactic products against respiratory syncytial virus (RSV) has resulted in notable advancements, leading to an increased demand for preclinical experiments and placing greater demands on animal models. Nevertheless, the field of RSV research continues to face the challenge of a lack of ideal animal models. Despite the demonstration of efficacy in animal studies, numerous RSV vaccine candidates have been unsuccessful in clinical trials, primarily due to the lack of suitable animal models. The most commonly utilized animal models for RSV research are cotton rats, mice, lambs, and non-human primates. These animals have been extensively employed in mechanistic studies and in the development and evaluation of vaccines and therapeutics. However, each model only exemplifies some, but not all, aspects of human RSV disease. The aim of this study was to provide a comprehensive summary of the disease symptoms, viral replication, pathological damage, and enhanced RSV disease (ERD) conditions across different RSV animal models. Furthermore, the advantages and disadvantages of each model are discussed, with the intention of providing a valuable reference for related RSV research.

Preclinical animal models to evaluate therapeutic antiviral antibodies

Despite the availability of effective preventative vaccines and potent small-molecule antiviral drugs, effective non-toxic prophylactic and therapeutic measures are still lacking for many viruses. The use of monoclonal and polyclonal antibodies in an antiviral context could fill this gap and provide effective virus-specific medical interventions. In order to develop these therapeutic antibodies, preclinical animal models are of utmost importance. Due to the variability in viral pathogenesis, immunity and overall characteristics, the most representative animal model for human viral infection differs between virus species. Therefore, throughout the years researchers sought to find the ideal preclinical animal model for each virus. The most used animal models in preclinical research include rodents (mice, ferrets, …) and non-human primates (macaques, chimpanzee, ….). Currently, antibodies are tested for antiviral efficacy against a variety of viruses including different hepatitis viruses, human immunodeficiency virus (HIV), influenza viruses, respiratory syncytial virus (RSV), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and rabies virus. This review provides an overview of the current knowledge about the preclinical animal models that are used for the evaluation of therapeutic antibodies for the abovementioned viruses.

The Respiratory Syncytial Virus (RSV) G Protein Enhances the Immune Responses to the RSV F Protein in an Enveloped Virus-Like Particle Vaccine Candidate

Respiratory syncytial virus (RSV) is a serious human respiratory pathogen, but no RSV vaccine has been licensed. Many vaccine candidates are focused on the viral F protein since the F protein is more conserved than the viral G protein across RSV strains and serotypes; thus, the F protein is thought more likely to induce a broader range of protection from infection. However, it is the G protein that binds the likely receptor, CX3CR1, in lung ciliated epithelial cells, raising the question of the importance of the G protein in vaccine candidates. Using virus-like particle (VLP) vaccine candidates, we have directly compared VLPs containing only the prefusion F protein (pre-F), only the G protein, or both glycoproteins. We report that VLPs containing both glycoproteins bind to anti-F-protein-specific monoclonal antibodies differently than do VLPs containing only the prefusion F protein. In RSV-naive cotton rats, VLPs assembled with only the pre-F protein stimulated extremely weak neutralizing antibody (NAb) titers, as did VLPs assembled with G protein. However, VLPs assembled with both glycoproteins stimulated quite robust neutralizing antibody titers, induced improved protection of the animals from RSV challenge compared to pre-F VLPs, and induced significantly higher levels of antibodies specific for F protein antigenic site 0, site III, and the AM14 binding site than did VLPs containing only the pre-F protein. These results indicate that assembly of pre-F protein with G protein in VLPs further stabilized the prefusion conformation or otherwise altered the conformation of the F protein, increasing the induction of protective antibodies. IMPORTANCE Respiratory syncytial virus (RSV) results in significant disease in infants, young children, and the elderly. Thus, development of an effective vaccine for these populations is a priority. Most ongoing efforts in RSV vaccine development have focused on the viral fusion (F) protein; however, the importance of the inclusion of G in vaccine candidates is unclear. Here, using virus-like particles (VLPs) assembled with only the F protein, only the G protein, or both glycoproteins, we show that VLPs assembled with both glycoproteins are a far superior vaccine in a cotton rat model compared with VLPs containing only F protein or only G protein. The results show that the presence of G protein in the VLPs influences the conformation of the F protein and the immune responses to F protein, resulting in significantly higher neutralizing antibody titers and better protection from RSV challenge. These results suggest that inclusion of G protein in a vaccine candidate may improve its effectiveness.

Correlative outcomes of maternal immunization against RSV in cotton rats

Maternal anti-respiratory syncytial virus (RSV) antibodies protect neonates from RSV disease throughout first weeks of life. Previous studies of maternal immunization in cotton rats showed that a single immunization during pregnancy of RSV-primed dams with virus-like particles (VLPs) assembled with pre-fusion F protein and the wild type G protein boosted their RSV serum antibody concentration and protected pups early in life against RSV challenge. We extended these findings by evaluating responses to RSV infection in litters from two consecutive pregnancies of immunized dams. Using an RSV-primed population of VLP-vaccinated and unvaccinated dams, we defined correlations between dams' and litters' RSV neutralizing antibodies (NA); between litters' NA and protection; and between litter's NA and their lung expression of selected cytokines, of a first or of a second pregnancy. Lung pathology was also evaluated. We found positive correlation between the NA titers in the dams at delivery and the NA in their first and second litters and negative correlations between the litters' NA and protection from RSV challenge. Vaccination of dams modulated the mRNA expression for IFNγ and IL-6 and lung pathology in the first and in the second litter at different times after birth, even in the absence of detectable NA. Maternal RSV vaccination enhanced the levels of antibodies transferred to offspring and their protection from challenge. Importantly, maternal vaccination also impacted the immunological and inflammatory response of the offspring's lungs well into maturity, and after the antiviral effect of maternally transferred NA waned or was no longer detectable.