Intranasal influenza-vectored COVID-19 vaccine restrains the SARS-CoV-2 inflammatory response in hamsters

Immunogenicity of intranasal vaccine based on SARS-CoV-2 spike protein during primary and booster immunizations in mice

Mucosal immunity plays a crucial role in combating and controlling the spread of highly mutated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Recombinant subunit vaccines have shown safety and efficacy in clinical trials, but further investigation is necessary to evaluate their feasibility as mucosal vaccines. This study developed a SARS-CoV-2 mucosal vaccine using spike (S) proteins from a prototype strain and the omicron variant, along with a cationic chitosan adjuvant, and systematically evaluated its immunogenicity after both primary and booster immunization in mice. Primary immunization through intraperitoneal and intranasal administration of the S protein elicited cross-reactive antibodies against prototype strains, as well as delta and omicron variants, with particularly strong effects observed after mucosal vaccination. In the context of booster immunization following primary immunization with inactivated vaccines, the omicron-based S protein mucosal vaccine resulted in a broader and more robust neutralizing antibody response in both serum and respiratory mucosa compared to the prototype vaccine, enhancing protection against different variants. These findings indicate that mucosal vaccination with the S protein has the potential to trigger a broader and stronger antibody response during primary and booster immunization, making it a promising strategy against respiratory pathogens.

Virus-Mimetic Extracellular-Vesicle Vaccine Boosts Systemic and Mucosal Immunity via Immune Recruitment

Mucosal vaccines can prevent viruses from infecting the respiratory mucosa, rather than only curtailing infection and protecting against the development of disease symptoms. The SARS-CoV-2 spike receptor-binding domain (RBD) is a compelling vaccine target but is undermined by suboptimal mucosal immunogenicity. Here, we report a SARS-CoV-2-mimetic extracellular-vesicle vaccine developed using genetic engineering and dendritic cell membrane budding. After mucosal immunization, the vaccine recruits antigen-presenting cells rapidly initiating a strong innate immune response. Notably, it obviates the need for adjuvants and can induce germinal center formation through both intramuscular and intratracheal vaccination. It not only elicits high levels of RBD-specific antibodies but also stimulates extensive cellular immunity in the respiratory mucosa. A sequential immunization strategy, starting with an intramuscular injection followed by an intratracheal booster, significantly bolsters mucosal immunity with high levels of IgA and tissue-resident memory T cell responses, thereby establishing a formidable defense against pseudovirus infection.

Towards broad-spectrum protection: the development and challenges of combined respiratory virus vaccines

In the post-COVID-19 era, the co-circulation of respiratory viruses, including influenza, SARS-CoV-2, and respiratory syncytial virus (RSV), continues to have significant health impacts and presents ongoing public health challenges. Vaccination remains the most effective measure for preventing viral infections. To address the concurrent circulation of these respiratory viruses, extensive efforts have been dedicated to the development of combined vaccines. These vaccines utilize a range of platforms, including mRNA-based vaccines, viral vector vaccines, and subunit vaccines, providing opportunities in addressing multiple pathogens at once. This review delves into the major advancements in the field of combined vaccine research, underscoring the strategic use of various platforms to tackle the simultaneous circulation of respiratory viruses effectively.

From intramuscular to nasal: unleashing the potential of nasal spray vaccines against coronavirus disease 2019

Coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected 700 million people worldwide since its outbreak in 2019. The current pandemic strains, including Omicron and its large subvariant series, exhibit strong transmission and stealth. After entering the human body, the virus first infects nasal epithelial cells and invades host cells through the angiotensin-converting enzyme 2 receptor and transmembrane serine protease 2 on the host cell surface. The nasal cavity is an important body part that protects against the virus. Immunisation of the nasal mucosa produces immunoglobulin A antibodies that effectively neutralise viruses. Saline nasal irrigation, a type of physical therapy, can reduce the viral load in the nasal cavity and prevent viral infections to some extent. As a commonly used means to fight SARS-CoV-2, the intramuscular (IM) vaccine can induce the human body to produce a systemic immune response and immunoglobulin G antibody; however, the antibody is difficult to distribute to the nasal mucosa in time and cannot achieve a good preventive effect. Intranasal (IN) vaccines compensate for the shortcomings of IM vaccines, induce mucosal immune responses, and have a better effect in preventing infection. In this review, we discuss the nasal defence barrier, the harm caused by SARS-CoV-2, the mechanism of its invasion into host cells, nasal cleaning, IM vaccines and IN vaccines, and suggest increasing the development of IN vaccines, and use of IN vaccines as a supplement to IM vaccines.

SARS-CoV-2 and Influenza Co-Infection: Fair Competition or Sinister Combination?

The COVID-19 pandemic remains a serious public health problem globally. During winter influenza seasons, more aggressive SARS-CoV-2 infections and fatalities have been documented, indicating that influenza co-infections may significantly impact the disease outcome of COVID-19. Both influenza and SARS-CoV-2 viruses share many similarities in their transmission and their cellular tropism for replication in the human respiratory tract. However, the complex intricacies and multi-faceted dynamics of how the two pathogens interact to ensure their survival in the same lung microenvironment are still unclear. In addition, clinical studies on influenza co-infections in COVID-19 patients do not provide conclusive evidence of how influenza co-infection mechanistically modifies disease outcomes of COVID-19. This review discusses various viral as well as host factors that potentially influence the survival or synergism of these two respiratory pathogens in the infected lung microenvironment.

COVID-19 Variants and Vaccine Development

Coronavirus disease 2019 (COVID-19), the global pandemic caused by severe acute respiratory syndrome 2 virus (SARS-CoV-2) infection, has caused millions of infections and fatalities worldwide. Extensive SARS-CoV-2 research has been conducted to develop therapeutic drugs and prophylactic vaccines, and even though some drugs have been approved to treat SARS-CoV-2 infection, treatment efficacy remains limited. Therefore, preventive vaccination has been implemented on a global scale and represents the primary approach to combat the COVID-19 pandemic. Approved vaccines vary in composition, although vaccine design has been based on either the key viral structural (spike) protein or viral components carrying this protein. Therefore, mutations of the virus, particularly mutations in the S protein, severely compromise the effectiveness of current vaccines and the ability to control COVID-19 infection. This review begins by describing the SARS-CoV-2 viral composition, the mechanism of infection, the role of angiotensin-converting enzyme 2, the host defence responses against infection and the most common vaccine designs. Next, this review summarizes the common mutations of SARS-CoV-2 and how these mutations change viral properties, confer immune escape and influence vaccine efficacy. Finally, this review discusses global strategies that have been employed to mitigate the decreases in vaccine efficacy encountered against new variants.

A Chymotrypsin-Dependent Live-Attenuated Influenza Vaccine Provides Protective Immunity against Homologous and Heterologous Viruses

Influenza virus is one of the main pathogens causing respiratory diseases in humans. Vaccines are the most effective ways to prevent viral diseases. However, the limited protective efficacy of current influenza vaccines highlights the importance of novel, safe, and effective universal influenza vaccines. With the progress of the COVID-19 pandemic, live-attenuated vaccines delivered through respiratory mucosa have shown robustly protective efficacy. How to obtain a safe and effective live-attenuated vaccine has become a major challenge. Herein, using the influenza virus as a model, we have established a strategy to quickly obtain a live-attenuated vaccine by mutating the cleavage site of the influenza virus. This mutated influenza virus can be specifically cleaved by chymotrypsin. It has similar biological characteristics to the original strain in vitro, but the safety is improved by at least 100 times in mice. It can effectively protect against lethal doses of both homologous H1N1 and heterologous H5N1 viruses post mucosal administration, confirming that the vaccine generated by this strategy has good safety and broad-spectrum protective activities. Therefore, this study can provide valuable insights for the development of attenuated vaccines for respiratory viruses or other viruses with cleavage sites.

Intranasal influenza-vectored COVID-19 vaccines confer broad protection against SARS-CoV-2 XBB variants in hamsters

The XBB.1.5 subvariant has garnered significant attention due to its exceptional immune evasion and transmissibility. Significantly, the evolutionary trajectory of SARS-CoV-2 has shown continual progression, with a recent global shift observed from XBB to BA.2.86, exemplified by the emergence of the predominant JN.1 subvariant. This phenomenon highlights the need for vaccines that can provide broad-spectrum antigenic coverage. In this study, we utilized a NS1-deleted (dNS1) influenza viral vector to engineer an updated live-attenuated vectored vaccine called dNS1-XBB-RBD. This vaccine encodes the receptor-binding domain (RBD) protein of the XBB.1.5 strain. Our findings demonstrate that the dNS1-XBB-RBD vaccine elicits a similar systemic and mucosal immune response compared to its prototypic form, dNS1-RBD. In hamsters, the dNS1-XBB-RBD vaccine provided robust protection against the SARS-CoV-2 immune-evasive strains XBB.1.9.2.1 and Beta. Remarkably, nasal vaccination with dNS1-RBD, which encodes the ancestor RBD gene, also effectively protected hamsters against both the XBB.1.9.2.1 and Beta strains. These results provide valuable insights about nasal influenza-vectored vaccine and present a promising strategy for the development of a broad-spectrum vaccine against COVID-19 in the future.

SARS-CoV-2 infection induces robust mucosal antibody responses in the upper respiratory tract

Despite multiple research efforts to characterize coronavirus disease 2019 (COVID-19) in humans, there is no clear data on the specific role of mucosal immunity on COVID-19 disease. Here, we longitudinally profile the antibody response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and seasonal HCoV-OC43 S proteins in serum and nasopharyngeal swabs from COVID-19 patients. Results showed that specific antibody responses against SARS-CoV-2 and HCoV-OC43 S proteins can be detected in the upper respiratory tract. We found that COVID-19 patients mounted a robust mucosal antibody response against SARS-CoV-2 S with specific secretory immunoglobulin A (sIgA), IgA, IgG, and IgM antibody subtypes detected in the nasal swabs. Additionally, COVID-19 patients showed IgG, IgA, and sIgA responses against HCoV-OC43 S in the local mucosa, whereas no specific IgM was detected. Interestingly, mucosal antibody titers against SARS-CoV-2 peaked at day 7, whereas HCoV-OC43 titers peaked earlier at day 3 post-recruitment, suggesting an immune memory recall to conserved epitopes of beta-HCoVs in the upper respiratory tract.

Inhalable hybrid nanovaccines with virus-biomimetic structure boost protective immune responses against SARS-CoV-2 variants

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with different antigenic variants, has posed a significant threat to public health. It is urgent to develop inhalable vaccines, instead of injectable vaccines, to elicit mucosal immunity against respiratory viral infections.

METHODS

We reported an inhalable hybrid nanovaccine (NVRBD-MLipo) to boost protective immunity against SARS-CoV-2 infection. Nanovesicles derived from genetically engineered 293T cells expressing RBD (NVRBD) were fused with pulmonary surfactant (PS)-biomimetic liposomes containing MPLA (MLipo) to yield NVRBD-MLipo, which possessed virus-biomimetic structure, inherited RBD expression and versatile properties.

RESULTS

In contrast to subcutaneous vaccination, NVRBD-MLipo, via inhalable vaccination, could efficiently enter the alveolar macrophages (AMs) to elicit AMs activation through MPLA-activated TLR4/NF-κB signaling pathway. Moreover, NVRBD-MLipo induced T and B cells activation, and high level of RBD-specific IgG and secretory IgA (sIgA), thus elevating protective mucosal and systemic immune responses, while reducing side effects. NVRBD-MLipo also demonstrated broad-spectrum neutralization activity against SARS-CoV-2 (WT, Delta, Omicron) pseudovirus, and protected immunized mice against WT pseudovirus infection.

CONCLUSIONS

This inhalable NVRBD-MLipo, as an effective and safe nanovaccine, holds huge potential to provoke robust mucosal immunity, and might be a promising vaccine candidate to combat respiratory infectious diseases, including COVID-19 and influenza.

Short-term effectiveness of single-dose intranasal spray COVID-19 vaccine against symptomatic SARS-CoV-2 Omicron infection in healthcare workers: a prospective cohort study

Background

The pivotal phase 3 efficacy clinical trial has demonstrated that a two-dose regimen of dNS1-RBD (Beijing Wantai Biological Pharmacy Enterprise, Beijing, China) is well-tolerated and provides wide protection against SARS-CoV-2 infection. However, the effectiveness of a single-dose regimen is still unknown. We aimed to estimate the effectiveness of one-dose of dNS1-RBD against symptomatic Omicron infections in real-world conditions.

Methods

This prospective cohort study was conducted during an Omicron outbreak among healthcare workers in Xiamen, China, from December 22, 2022 to January 16, 2023. Participants chose to receive single-dose of dNS1-RBD or remain unvaccinated based on personal preference. Healthcare workers daily validated their SARS-CoV-2 infection status, using either RT-PCR or rapid antigen test. A survey questionnaire was conducted to gather information on acute symptoms from individuals infected with SARS-CoV-2. The primary outcome was the symptomatic SARS-CoV-2 infections after enrollment in the dNS1-RBD recipients or the control group among all participants and by prior COVID-19 vaccination status.

Findings

On December 22, 2022, a total of 1391 eligible participants without a history of prior SARS-CoV-2 infection were enrolled. Among them, 550 received single-dose of dNS1-RBD, while 841 remained unvaccinated. In the total cohort, the range of follow-up time was 1∼26 days. During the study period, a total of 880 symptomatic SARS-CoV-2 infections were identified in the total cohort. The adjusted vaccine effectiveness against symptomatic SARS-CoV-2 infections and the infections requiring medical attention were 19.0% (95% CI: 6.7, 29.7, P = 0.004) and 59.4% (95% CI: 25.1, 78.0, P = 0.004) in the total cohort, 11.6% (95% CI: -2.4, 23.7, P = 0.100) and 55.3% (95% CI: 15.3, 76.4, P = 0.014) in the participants with inactivated COVID-19 vaccination history, as well as 87.0% (95% CI: 72.6, 93.9, P < 0.001) and 84.2% (95% CI: -41.8, 98.2, P = 0.099) in the naïve participants, respectively.

Interpretation

When administered as a booster to individuals with a history of inactivated COVID-19 vaccination, a single-dose of dNS1-RBD provides protection against infections requiring medical attention at least in the short-term after vaccination. The data also showed that a single-dose of dNS1-RBD is protective against symptomatic SARS-CoV-2 infections as a primary immunization for individuals without prior exposure, but due to the limited sample size of naïve participants, further research with a larger sample size is needed to make a solid conclusion.

Funding

Xiamen Science and Technology Bureau 2022 General Science and Technology Plan Project and the Bill & Melinda Gates Foundation.

Progress and challenges in the clinical evaluation of immune responses to respiratory mucosal vaccines

INTRODUCTION

Following the coronavirus disease pandemic, respiratory mucosal vaccines that elicit both mucosal and systemic immune responses have garnered increasing attention. However, human physiological characteristics pose significant challenges in the evaluation of mucosal immunity, which directly impedes the development and application of respiratory mucosal vaccines.

AREAS COVERED

This study summarizes the characteristics of immune responses in the respiratory mucosa and reviews the current status and challenges in evaluating immune response to respiratory mucosal vaccines.

EXPERT OPINION

Secretory Immunoglobulin A (S-IgA) is a major effector molecule at mucosal sites and a commonly used indicator for evaluating respiratory mucosal vaccines. However, the unique physiological structure of the respiratory tract pose significant challenges for the clinical collection and detection of S-IgA. Therefore, it is imperative to develop a sampling method with high collection efficiency and acceptance, a sensitive detection method, reference materials for mucosal antibodies, and to establish a threshold for S-IgA that correlates with clinical protection. Sample collection is even more challenging when evaluating mucosal cell immunity. Therefore, a mucosal cell sampling method with high operability and high tolerance should be established. Targets of the circulatory system capable of reflecting mucosal cellular immunity should also be explored.

Role of Immunoglobulin A in COVID-19 and Influenza Infections

Immunoglobulin A (IgA) is critical in the immune response against respiratory infections like COVID-19 and influenza [...].

Intranasal Route: A Nasocerebral Approach against SARS-CoV-2 in NeuroCOVID

The nasal cavity is a prime site for viral load of SARS-CoV-2 in COVID-19, as is evident from the fact that this area has been used for sample collection for the diagnosis of COVID-19. The nasal cavity has a connection with the brain across the cribriform plate which has been reported to be a route of SARS-CoV-2 to the olfactory apparatus and the brain. Targeting the SARS-CoV-2 in the nasal cavity in patients presenting with COVID-19 and long-COVID can result in the prevention and treatment of neurological deficits and therefore needs to be prioritized as a route of potential significance.