An easy pill to swallow: oral recombinant vaccines for the 21st century

Norovirus replication, host interactions and vaccine advances

Human noroviruses (HuNoVs) are the leading cause of acute gastroenteritis worldwide in all age groups and cause significant disease and economic burden globally. To date, no approved vaccines or antiviral therapies are available to treat or prevent HuNoV illness. Several candidate vaccines are in clinical trials, although potential barriers to successful development must be overcome. Recently, significant advances have been made in understanding HuNoV biology owing to breakthroughs in virus cultivation using human intestinal tissue-derived organoid (or enteroid) cultures, advances in structural biology technology combined with epitope mapping and increased metagenomic sequencing. New and unexpected strain-specific differences in pandemic versus non-pandemic virus structures, replication properties and virus-host interactions, including host factors required for susceptibility to infection and pathogenesis, are discussed.

An oral recombinant human type 5 adenovirus vector vaccine encoding the S protein of Type I feline coronavirus effectively protection against FCoV challenge in cats

Feline coronavirus (FCoV) poses a significant threat to the lives of cats, and there is currently no commercial vaccines available. In the present study, a vaccine was developed using a human type 5 adenovirus vector to express the FCoV-I S protein (rAd5-FCoV-S) to induce the immunogenicity of rAd5-FCoV-S through oral and intramuscular immunization in mice and cats. Both vaccination methods stimulated a higher IgG antibody response. However, oral vaccination led to a significantly higher SIgA antibody level, which was 4.8 times and 2.4 times greater than that induced by intramuscular vaccination in mice and cats, respectively, with the highest level reaching 1:128. In addition, oral vaccination increased the count of IFN-γ-producing and IL-4-producing splenocytes in mice, effectively boosting cellular immune responses. Challenge protection experiments in cats showed that oral vaccination with rAd5-FCoV-S provided 100 % protection compared to a survival rate of only 33 % for unvaccinated cats. Compared to the PBS group, oral rAd5-FCoV-S administration substantially decreased the FCoV viral load within the feces, rectal tissues, and colon tissues of cats. Hematoxylin and eosin (HE) staining and immunohistochemical analysis of rectal and colonic tissues revealed that cats in the oral group exhibited minimal intestinal damage, whereas PBS cats presented significant inflammatory cell infiltration and shedding of intestinal epithelial cells. These findings demonstrate that oral administration of rAd5-FCoV-S induces a robust humoral immune response and a strong cell-mediated immune response in cats, thereby conferring immunity against FCoV infection.

Oral Ad5 Vector-Based SARS-CoV-2 Vaccine Effectively Induces Mucosal and Systemic Immune Responses in BALB/c Mice

Mucosal immunity is essential for preventing viral infections through the mucosal route. The emerging SARS-CoV-2 variants have posed additional hurdles to the efficiency of existing vaccines. The rapid development of novel vaccines that generate broad mucosal and systemic immunity could be the most effective strategy to address this issue. In this study, we developed a recombinant and replication-deficient type-5 adenoviral vaccine with a built-in double-strand RNA adjuvant and the vaccine expresses the SARS-CoV-2 Omicron BA.1 spike (S) antigen (hereinafter referred to as "the oral vaccine"). We found that two doses of the oral vaccine in BALB/c mice generated long-lasting S-specific mucosal and systemic immune responses, as well as broad neutralizing antibodies and SIgA antibodies. In addition, we found that compared to an mRNA vaccine booster, using the oral vaccine as a booster could induce both effective mucosal and systemic immunity, addressing the limitation of mRNA vaccines in eliciting mucosal immunity. Prospective oral vaccines require further investigation into development and potential applications, particularly viral challenge experiments, before clinical trials.

Konjac glucomannan exerts regulatory effects on macrophages and its applications in biomedical engineering

Konjac glucomannan (KGM) molecular chains contain a small amount of acetyl groups and a large number of hydroxyl groups, thereby exhibiting exceptional water retention and gel-forming properties. To meet diverse requirements, KGM undergoes modification processes such as oxidation, acetylation, grafting, and cationization, which reduce its viscosity, enhance its mechanical strength, and improve its water solubility. Researchers have found that KGM and its derivatives can regulate the polarization of macrophages, inducing their transformation into classically activated M1-type macrophages or alternatively activated M2-type macrophages, and even facilitating the interconversion between M1 and M2 phenotypes. Concurrently, the modulation of macrophage polarization states holds significant importance for chronic wound healing, inflammatory bowel disease (IBD), antitumor therapy, tissue engineering scaffolds, oral vaccines, pulmonary delivery, and probiotics. Therefore, KGM has the advantages of both immunomodulatory effects (biological activity) and gel-forming properties (physicochemical properties), giving it significant advantages in a variety of biomedical engineering applications.

Cutting-edge research frontiers in oral cavity vaccines for respiratory diseases: a roadmap for scientific advancement

Intramuscular vaccines present limitations in eliciting robust mucosal immunity and preventing respiratory pathogens transmission. Sublingual vaccine administration offers promising advantages, including interconnected mucosal protection. Despite these advantages, only a few clinical trials have explored sublingual vaccines, underscoring the necessity of optimizing next-generation vaccine formulas. Critical research priorities include understanding vector behavior in the oral environment, understanding their interactions with mucosal immunity and developing formulations enabling sustained mucosal contact to facilitate efficient transduction. Consequently, tonsil organoids, as representative human mucosal models, could offer critical insights into sublingual immunization. Thus, a multi-disciplinary approach integrating pharmacological, immunological, and manufacturing considerations is pivotal for sublingual vaccines in targeting pathogen-aggravated prevalent respiratory diseases including asthma, COPD and lung cancer, as well as the antimicrobial resistance crisis.