Antigenicity and immunogenicity of unique prefusion-mimic F proteins presented on enveloped virus-like particles

An oral vaccine based on the Ad5 vector with a double-stranded RNA adjuvant protects mice against respiratory syncytial virus

A safe and effective vaccine is urgently needed to prevent acute respiratory infections caused by respiratory syncytial virus (RSV). Oral administration offers several advantages, including ease of delivery, minimal stress for vaccine recipients, and greater safety than the systemic injection. In this study, we developed an oral vaccine candidate based on the human adenovirus serotype 5 (Ad5) vector, Ad5-PreF-DS2, encoding a prefusion protein of RSV with a dsRNA as an endogenous adjuvant. We evaluated the immunogenicity and protective efficacy of oral immunization against an RSV challenge in mice, comparing it with those of IM and IN immunizations. Subsequently, we performed an in-depth analysis of the B cell immune response to the oral vaccine. Our findings indicate that oral vaccines elicited a robust antibody response, T-cell response, and B-cell response, and provide effective protection against RSV infection in mice. Importantly, dsRNA adjuvants significantly enhanced T-cell immune responses and increased neutralizing antibody levels when administered via oral vaccination (P < 0.05). These preclinical data demonstrate the capacity of an oral vaccine to induce protective immunity against RSV and support further development of RSV vaccine.

The Central Conserved Peptides of Respiratory Syncytial Virus G Protein Enhance the Immune Response to the RSV F Protein in an Adenovirus Vector Vaccine Candidate

Respiratory syncytial virus (RSV) is a serious human respiratory pathogen that commonly affects children, older adults, and immunocompromised individuals. At present, the design of licensed vaccines focuses on the incorporation of the pre-fusion protein (PreF protein) of RSV, as this protein has the ability to induce antibodies that offer a high level of protection. Moreover, the G protein contains the CX3C motif that binds the chemokine receptor CX3CR1 in respiratory epithelial cells, which plays an essential role in viral infection. Therefore, incorporating the G antigen into vaccine design may prove more advantageous for RSV prevention. In this study, we developed a human adenoviral vector-based RSV vaccine containing highly neutralizing immunogens, a modified full-length PreF protein fused with the central conserved peptides of the G protein (Gcc) from both RSV subgroups trimerized via a C-terminal foldon, and evaluated its immune response in mice through intranasal (i.n.) immunization. Our results showed that immunization with Ad5-PreF-Qa-Gcc elicited a balanced Th1/Th2 immune response and robust mucosal immunity with higher neutralizing antibody titers against RSV Long and RSV B1. Importantly, immunization with Ad5-PreF-Qa-Gcc enhanced CD4+ CD25+ FoxP3+ Treg cell response and protected the mice against RSV infection. Our data demonstrate that the combination of Gcc and the PreF antigen is a viable strategy for developing effective RSV vaccines.

Efficacy and safety of respiratory syncytial virus vaccination during pregnancy to prevent lower respiratory tract illness in newborns and infants: a systematic review and meta-analysis of randomized controlled trials

To evaluate the effectiveness and safety of respiratory syncytial virus (RSV) vaccination during pregnancy in preventing lower respiratory tract infection (LRTI) in infants and neonates, we conducted a systematic search of randomized controlled trials (RCTs) in five databases (PubMed, Embase and Cochrane Library, Web of Science, Cochrane Center Register of Controlled trial) until 1 May 2023. We performed a meta-analysis of the eligible trials using RevMan5.4.1 software. Our analysis included six articles and five RCTs. The meta-analysis revealed significant differences in the incidences of LRTI [risk ratio (RR): 0.64; 95% confidence interval (CI): 0.43, 0.96; p = 0.03)] and severe LRTI (RR: 0.37; 95% CI: 0.18, 0.79; p = 0.01) between the vaccine group and the placebo group for newborns and infants. These differences were observed at 90, 120, and 150 days after birth (p = 0.003, p = 0.05, p = 0.02, p = 0.03, p = 0.009, p = 0.05). At 180 days after birth, there was a significant difference observed in the incidence of LRTI between the two groups (RR: 0.43; 95% CI: 0.21, 0.90; p = 0.02). The safety results showed a significant difference in the incidence of common adverse events between the two groups (RR: 1.08; 95% CI: 1.04, 1.12; p < 0.0001). However, there was no significant difference observed in the incidence of serious adverse events (RR: 1.05; 95% CI: 0.97, 1.15; p = 0.23), common and serious adverse events (RR: 1.02; 95% CI: 0.96, 1.10; p = 0.23), or common and serious adverse events among pregnant women and newborns and infants (RR: 0.98; 95% CI: 0.93, 1.04; p = 0.52). In conclusion, maternal RSV vaccination is an effective and safe immunization strategy for preventing LRTI in postpartum infants, with greater efficacy observed within the first 150 days after birth.

Respiratory Viruses and Virus-like Particle Vaccine Development: How Far Have We Advanced?

With technological advancements enabling globalization, the intercontinental transmission of pathogens has become much easier. Respiratory viruses are one such group of pathogens that require constant monitoring since their outbreak leads to massive public health crises, as exemplified by the influenza virus, respiratory syncytial virus (RSV), and the recent coronavirus disease 2019 (COVID-19) outbreak caused by the SARS-CoV-2. To prevent the transmission of these highly contagious viruses, developing prophylactic tools, such as vaccines, is of considerable interest to the scientific community. Virus-like particles (VLPs) are highly sought after as vaccine platforms for their safety and immunogenicity profiles. Although several VLP-based vaccines against hepatitis B and human papillomavirus have been approved for clinical use by the United States Food and Drug Administration, VLP vaccines against the three aforementioned respiratory viruses are lacking. Here, we summarize the most recent progress in pre-clinical and clinical VLP vaccine development. We also outline various strategies that contributed to improving the efficacy of vaccines against each virus and briefly discuss the stability aspect of VLPs that makes it a highly desired vaccine platform.

Virus-like particles coexpressing the PreF and Gt antigens of respiratory syncytial virus confer protection in mice

Aims: The purpose of this study was to assess the protective efficacy of virus-like particles (VLPs) co-expressing the pre-fusogenic (PreF) and G protein with tandem repeats (Gt) antigens of respiratory syncytial virus (RSV) in mice. Materials & methods: VLP constructs expressing PreF, Gt or both were used to immunize mice, and the protective efficacies were evaluated using antibody responses, neutralizing antibody titers, T-cell responses, histopathological assessment and plaque assay. Results: PreF+Gt VLP immunization elicited strong RSV-specific antibody responses and pulmonary T-cell responses that contributed to lessening virus titer and inflammation. Conclusion: Our findings suggest that coexpressing PreF and Gt antigens elicits better protection than either one alone. This combinatorial approach could assist in future RSV vaccine development.