Multi-Component Intranasal COVID-19 Vaccine Shows Promise in Preclinical and Early Human Studies
核心洞察
Researchers developed a two-component intranasal COVID-19 (搜索) vaccine combining adenoviral vector (搜索) and protein subunit platforms that demonstrated robust mucosal and systemic immunity in animal models.
The vaccine, comprised of human Ad5 vector expressing spike protein (搜索) and recombinant RBD protein, provided protection against live viral challenge and prevented transmission in preclinical studies.
Early human trials in 70 adults showed the intranasal vaccine was well-tolerated with only mild adverse reactions and induced strong antibody responses in both serum and nasal samples.
Researchers have developed a novel multi-component intranasal COVID-19 (搜索) vaccine that combines adenoviral vector (搜索) and protein subunit platforms, demonstrating promising results in both animal models and early human trials. The approach addresses limitations of current intramuscular vaccines by targeting mucosal immunity at the primary site of SARS-CoV-2 (搜索) infection.
Novel Vaccine Design Overcomes Platform Limitations
The two-component vaccine developed by Weiqi Hong and colleagues consists of a human adenovirus serotype 5 (Ad5) vector expressing the full spike protein (搜索) of the Omicron XBB.1.5 variant (Ad5XBB.1.5 (搜索)) combined with a recombinant spike receptor binding domain (搜索) protein (RBDXBB.1.5-HR (搜索)). This design leverages the strengths of both platforms while mitigating their individual weaknesses.
Viral vector vaccines typically induce strong immune responses through pathogen-recognition receptors like STING (搜索) and toll-like receptor-9 (搜索), acting as natural adjuvants. However, prior exposure to similar viruses can limit their effectiveness. Recombinant protein vaccines offer excellent safety profiles and can target specific pathogen components, but often require additional adjuvants that may increase adverse events.
The researchers demonstrated flexibility in their approach by also developing variants targeting the Omicron BA.5 strain and a three-component vaccine incorporating both XBB.1.5 and BA.5 variants, showing the platform's potential for multivalent protection.
Robust Preclinical Efficacy Data
In murine studies, the Ad5XBB.1.5 (搜索) + RBDXBB.1.5-HR (搜索) vaccine generated comprehensive immune responses both systemically and within respiratory mucosal tissues. Measurements included anti-RBD IgG and IgA antibody levels, pseudovirus and live virus neutralizing antibody responses, spike-specific germinal center B cells, and various T cell populations including CD4+ and CD8+ memory T cells.
Mechanistic studies using genetic knockout mice and single-cell RNA sequencing revealed that the adenoviral vector (搜索) enhanced dendritic cell phagocytosis, antigen processing, and presentation of the protein subunit through a STING (搜索)-dependent pathway. Notably, even an empty adenoviral vector demonstrated adjuvant properties.
Live viral challenge studies in mice and contact exposure experiments in hamsters confirmed the vaccine's protective efficacy. Analysis of genomic and subgenomic RNA in respiratory tissues, along with lung pathology assessments, indicated robust protection against SARS-CoV-2 (搜索) infection.
Promising Human Safety and Immunogenicity
The researchers conducted a human study administering low or high doses of the intranasal vaccine to 70 adults who had not received COVID-19 (搜索) vaccination or experienced infection in the previous 3-6 months. The prime-boost regimen was administered with a 14-day interval.
The vaccine demonstrated excellent tolerability with only self-limiting mild adverse reactions. Importantly, it produced robust mucosal and systemic humoral immune responses, as evidenced by analysis of both serum and nasal swab samples. However, the study was limited by sample collection only extending to 28 days post-vaccination and the absence of cellular immune response assessments.
Advantages of Mucosal Vaccination Approach
The intranasal delivery route offers several theoretical advantages over intramuscular administration. Since SARS-CoV-2 (搜索) primarily infects through respiratory mucosa, vaccines that induce secretory IgA and activate local resident memory cells may provide superior protection at the site of initial exposure compared to systemic immunity alone.
The adenoviral vector (搜索) facilitates effective transport across the mucosal barrier, as adenoviruses naturally infect via this route, while simultaneously acting as an adjuvant to boost uptake and presentation of the recombinant protein component. The researchers showed that heterologous vaccination with three intramuscular mRNA vaccine doses followed by their three-component platform enhanced both systemic and respiratory mucosal immunity beyond intramuscular vaccination alone.
Future Considerations for Variant Protection
While the current vaccine focuses on spike protein (搜索) components, the researchers acknowledge potential limitations for long-term protection against future variants, given the significant mutations in SARS-CoV-2 (搜索) spike protein that have contributed to immune escape. They suggest that incorporating non-spike proteins such as envelope, membrane, and nucleocapsid antigens, which are commonly targeted by T cells following natural infection, could provide broader and more durable immunity.
The work demonstrates that integration of adenoviral vectors as adjuvants within combined platform vaccines may provide novel strategies for inducing robust mucosal immunity, with potential importance for future vaccine development against respiratory pathogens.