Preclinical dose-ranging studies of a novel dry powder norovirus vaccine formulation

Advances in intranasal vaccine delivery: A promising non-invasive route of immunization

The importance of vaccination has been proven particularly significant the last three years, as it is revealed to be the most efficient weapon for the prevention of several infections including SARS-COV-2. Parenteral vaccination is the most applicable method of immunization, for the prevention of systematic and respiratory infections, or central nervous system disorders, involving T and B cells to a whole-body immune response. However, the mucosal vaccines, such as nasal vaccines, can additionally activate the immune cells localized on the mucosal tissue of the upper and lower respiratory tract. This dual stimulation of the immune system, along with their needle-free administration favors the development of novel nasal vaccines to produce long-lasting immunity. In recent years, the nanoparticulate systems have been extensively involved in the formulation of nasal vaccines as polymeric, polysaccharide and lipid ones, as well as in the form of proteosomes, lipopeptides and virosomes. Advanced delivery nanosystems have been designed and evaluated as carriers or adjuvants for nasal vaccination. To this end, several nanoparticulate vaccines are undergone clinical trials as promising candidates for nasal immunization, while nasal vaccines against influenza type A and B and hepatitis B have been approved by health authorities. This comprehensive literature review aims to summarize the critical aspects of these formulations and highlight their potential for the future establishment of nasal vaccination. Both preclinical (in vitro and in vivo) and clinical studies are incorporated, summarized, and critically discussed, as well as the limitations of nasal immunization.

Nano-adjuvanted dry powder vaccine for the mucosal immunization against airways pathogens

Nasal vaccination has been shown to provide optimal protection against respiratory pathogens. However, mucosal vaccination requires the implementation of specific immunization strategies to improve its effectiveness. Nanotechnology appears a key approach to improve the effectiveness of mucosal vaccines, since several nanomaterials provide mucoadhesion, enhance mucosal permeability, control antigen release and possess adjuvant properties. Mycoplasma hyopneumoniae is the main causative agent of enzootic pneumonia in pigs, a respiratory disease responsible for considerable economic losses in the pig farming worldwide. The present work developed, characterized, and tested in vivo an innovative dry powder nasal vaccine, obtained from the deposition on a solid carrier of an inactivated antigen and a chitosan-coated nanoemulsion, as an adjuvant. The nanoemulsion was obtained through a low-energy emulsification technique, a method that allowed to achieve nano droplets in the order of 200 nm. The oil phase selected was alpha-tocopherol, sunflower oil, and poly(ethylene glycol) hydroxystearate used as non-ionic tensioactive. The aqueous phase contained chitosan, which provides a positive charge to the emulsion, conferring mucoadhesive properties and favoring interactions with inactivated M. hyopneumoniae. Finally, the nanoemulsion was layered with a mild and scalable process onto a suitable solid carrier (i.e., lactose, mannitol, or calcium carbonate) to be transformed into a solid dosage form for administration as dry powder. In the experimental study, the nasal vaccine formulation with calcium carbonate was administered to piglets and compared to intramuscular administration of a commercial vaccine and of the dry powder without antigen, aimed at evaluating the ability of IN vaccination to elicit an in vivo local immune response and a systemic immune response. Intranasal vaccination was characterized by a significantly higher immune response in the nasal mucosa at 7 days post-vaccination, elicited comparable levels of Mycoplasma-specific IFN-γ secreting cells and comparable, if not higher, responsiveness of B cells expressing IgA and IgG in peripheral blood mononuclear cells, with those detected upon a conventional intramuscular immunization. In conclusion, this study illustrates a simple and effective strategy for the development of a dry powder vaccine formulation for nasal administration which could be used as alternative to current parenteral commercial vaccines.

Spray Drying and Particle Engineering in Dosage Form Design for Global Vaccines

Vaccines are a very important tool in the effort to reduce the global burden of infectious diseases. Modern vaccines can be formulated in several ways to induce specific immunity, including through the use of live bacteria, subunit antigens, and even genetic material. However, vaccines typically need to be transported and stored under controlled refrigerated or frozen conditions to maintain potency. This strict temperature control is incompatible with the available infrastructure in many developing countries. One method of improving the thermostability of a vaccine is through drying of a liquid presentation into a dry dosage form. In addition to enhancing the capability for distribution in resource-poor settings, these dry vaccine forms are more suitable for long-term stockpiling. Spray drying is a drying method that has been successfully used to stabilize many experimental vaccines into a dry form for storage above refrigerated temperatures. Additionally, the use of spray drying allows for the production of engineered particles suitable for respiratory administration. These particles can be further designed for increased out-of-package robustness against high humidity. Furthermore, there are already commercial dry powder delivery devices available that can be used to safely deliver vaccines to the respiratory system. The research in this field demonstrates that the resources to develop highly stable vaccines in flexible dosage forms are available and that these presentations offer many advantages for global vaccination campaigns.

Animal models in vaccinology: state of the art and future perspectives for an animal-free approach

Vaccine discovery and development is mainly driven by studies on immunogenicity and safety based on the appropriate animal models. In this review we will describe the importance of animal models in vaccinology, from research and development to pre-licensure and post-licensure commitments with particular emphasis on the advantages and limitations of each animal species. Finally, we will describe the most modern technologies, the new in vitro and ex vivo models and the new advances in the field which may drive into a new era of 'animal free' vaccinology.

Human Norovirus: Experimental Models of Infection

Human noroviruses (HuNoVs) are a leading cause of acute gastroenteritis worldwide. HuNoV infections lead to substantial societal and economic burdens. There are currently no licensed vaccines or therapeutics for the prevention or treatment of HuNoVs. A lack of well-characterized in vitro and in vivo infection models has limited the development of HuNoV countermeasures. Experimental infection of human volunteers and the use of related viruses such as murine NoV have provided helpful insights into HuNoV biology and vaccine and therapeutic development. There remains a need for robust animal models and reverse genetic systems to further HuNoV research. This review summarizes available HuNoV animal models and reverse genetic systems, while providing insight into their usefulness for vaccine and therapeutic development.

Virus-Like Particles-Based Mucosal Nanovaccines

Virus-like particles (VLPs) are protein complexes that resemble a virus and constitute highly immunogenic entities as they mimic the pathogen at an important degree. Among nanovaccines, those based on VLPs are the most successful thus far with some formulations already commercialized (e.g., those against hepatitis B and E viruses and human papillomavirus). This chapter highlights the advantages of VLPs-based vaccines, describing approaches for their design and transmittance of the state of the art for mucosal VLPs-based vaccines development. Several candidates have been produced in insect cells, plants, and E. coli and mammalian cells; they have been mainly evaluated in i.n. and oral immunization schemes. i.n. vaccines against the influenza virus and the Norwalk virus are the most advanced applications. For the latter, i.n. formulations are under clinical evaluation. Perspectives for the field comprise the expansion of the use of low-cost platforms such as plants and bacteria, the development of multiepitopic/multivalent vaccines, and computationally designed VLPs. Mucosal VLPs-based vaccines stand as a major promising approach in vaccinology and the initiation of more clinical trials is envisaged in a short time.

Intranasal immunization with aluminum salt-adjuvanted dry powder vaccine

Intranasal vaccination using dry powder vaccine formulation represents an attractive, non-invasive vaccination modality with better storage stability and added protection at the mucosal surfaces. Herein we report that it is feasible to induce specific mucosal and systemic antibody responses by intranasal immunization with a dry powder vaccine adjuvanted with an insoluble aluminum salt. The dry powder vaccine was prepared by thin-film freeze-drying of a model antigen, ovalbumin, adsorbed on aluminum (oxy)hydroxide as an adjuvant. Special emphasis was placed on the characterization of the dry powder vaccine formulation that can be realistically used in humans by a nasal dry powder delivery device. The vaccine powder was found to have "passable" to "good" flow properties, and the vaccine was uniformly distributed in the dry powder. An in vitro nasal deposition study using nasal casts of adult humans showed that around 90% of the powder was deposited in the nasal cavity. Intranasal immunization of rats with the dry powder vaccine elicited a specific serum antibody response as well as specific IgA responses in the nose and lung secretions of the rats. This study demonstrates the generation of systemic and mucosal immune responses by intranasal immunization using a dry powder vaccine adjuvanted with an aluminum salt.

More robust gut immune responses induced by combining intranasal and sublingual routes for prime-boost immunization

Norovirus causes acute and debilitating gastroenteritis, characterized by vomiting and diarrhea. We recently reported a recombinant GII. 4 P domain particle (Pd) vaccine adjuvanted with a flagellin, Vibrio vulnificus FlaB, effectively promoting both humoral and cell-mediated immune responses. In the previous study, we found that sublingual (SL) immunization induced higher fecal secretory IgA (SIgA) responses while intranasal (IN) route provided higher amplitude of humoral and cellular immune responses in the systemic compartment. We hypothesized that the combination of IN and SL routes should induce more potent and sustained SIgA responses in the gut. In this study, we have tried combinatorial prime-boost immunization employing both IN and SL routes. The IN priming and SL boosting with the Pd+FlaB vaccine enhanced highest SIgA responses in feces, accompanying increased Pd-specific memory B cells and plasma cells in spleen and bone marrow, respectively. Notably, the strongest long-lasting SIgA response in feces was induced by combined IN prime and SL boost vaccination, which was sustained for more than 3 months. Significantly enhanced gut-homing B cell and follicular helper T cell responses in mesenteric lymph nodes (mLNs) were observed in the IN prime and SL boost combination. IN priming was a requisite for the robust induction of Pd-specific IFNγ, IL-2, IL-4 and IL-5 cytokine responses in the systemic immune compartment. Collectively, the IN prime and SL boost combination was the best option for inducing balanced long-lasting immune responses against the norovirus antigen in both enteric and systemic compartments. These results suggest that immune responses in specific mucosal compartments may be programmed by employing different prime-boost immunization routes.

Development of a synthetic Vi polysaccharide vaccine for typhoid fever

Typhoid fever remains a serious public health problem with a high impact on toddlers and young children. Vaccines against the Vi capsular polysaccharide are efficacious against typhoid fever demonstrating that antibodies against Vi confer protection. The currently licensed Vi typhoid vaccines have however limited efficacy and are manufactured by a complex process from wild-type bacteria. Due to these inherent issues with the current vaccines, an alternative vaccine based on an O-acetylated high molecular weight (HMW) polygalacturonic acid (GelSite-OAc™) was generated. The HMW polygalacturonic acid shares the same backbone as the Vi polysaccharide of Salmonella Typhi. The GelSite-OAc™ has a high molecular weight (>1 × 106 Da) and a high degree of O-acetylation (DOAc) (>5 μmole/mg), both exceeding the potency specifications of the current Vi vaccine. Studies in Balb/c mice demonstrated that GelSite-OAc™ was highly immunogenic, inducing a strong antigen-specific antibody response in a DOAc- and dose-dependent manner which was comparable to or higher than those induced by the licensed Vi vaccine. Importantly, the GelSite-OAc™ was shown to be fully protective in mice against lethal challenge with Salmonella Typhi. Furthermore, the GelSite-OAc™ demonstrated a boosting effect or memory response, exhibiting a >2-fold increase in antibody levels upon the second immunization with either GelSite-OAc™ or the Vi vaccine. This novel boosting effect is unique among polysaccharide antigens and potentially makes GelSite-OAc™ effective in people under 2 years old. Together these results suggest that the GelSite-OAc™ could be a highly effective vaccine against Salmonella Typhi.

Intranasal immunization with dry powder vaccines

Vaccination represents a cost-effective weapon for disease prevention and has proven to dramatically reduce the incidences of several diseases that once were responsible for significant mortality and morbidity worldwide. The nasal cavity constitutes the initial stage of the respiratory system and the first contact with inhaled pathogens. The intranasal (IN) route for vaccine administration is an attractive alternative to injection, due to the ease of administration as well as better patient compliance. Many published studies have demonstrated the safety and effectiveness of IN immunization with liquid vaccines. Currently, two liquid IN vaccines are available and both contain live attenuated influenza viruses. FluMist® was approved in 2003 in the United States, and Nasovac® H1N1 vaccine was approved in India in 2010. Preclinical studies showed that IN immunization with dry powder vaccines (DPVs) is feasible. Although there is not a commercially available DPV yet, DPVs have the inherent advantage of being relatively more stable than liquid vaccines. This review focuses on recent developments of DPVs as next-generation IN vaccines.

Norovirus vaccines under development

Noroviruses (NoVs) are one of the leading causes of acute gastroenteritis, including both outbreaks and endemic infections. The development of preventive strategies, including vaccines, for the most susceptible groups (children <5years of age, the elderly and individuals suffering crowding, such as military personnel and travelers) is desirable. However, NoV vaccine development has faced many difficulties, including genetic/antigenic diversity, limited knowledge on NoV immunology and viral cycle, lack of a permissive cell line for cultivation and lack of a widely available and successful animal model. Vaccine candidates rely on inoculation of virus-like particles (VLPs) formed by the main capsid protein VP1, subviral particles made from the protruding domain of VP1 (P-particles) or viral vectors with a NoV capsid gene insert produced by bioengineering technologies. Polivalent vaccines including multiple NoV genotypes and/or other viruses acquired by the enteric route have been developed. A VLP vaccine candidate has reached phase II clinical trials and several others are in pre-clinical stages of development. In this article we discuss the main challenges facing the development of a NoV vaccine and the current status of prevailing candidates.

Intranasal delivery of a bivalent norovirus vaccine formulated in an in situ gelling dry powder

The global health community is beginning to understand the burden of norovirus-associated disease, which has a significant impact in both developed and developing countries. Norovirus virus like particle (VLP)-based vaccines are currently under development and have been shown to elicit systemic and mucosal immune responses when delivered intranasally. In the present study, we describe the use of a dry powder formulation (GelVac™) with an in situ gelling polysaccharide (GelSite™) extracted from Aloe vera for nasal delivery of a bivalent vaccine formulation containing both GI and GII.4 norovirus VLPs. Dose-ranging studies were performed to identify the optimal antigen dosages based on systemic and mucosal immune responses in guinea pigs and determine any antigenic interference. A dose-dependent increase in systemic and mucosal immunogenicity against each of the VLPs were observed as well as a boosting effect for each VLP after the second dosing. A total antigen dose of ≥50 μg of each GI and GII.4 VLPs was determined to be the maximally immunogenic dose in guinea pigs. The immunogenicity results of this bivalent formulation, taken together with previous work on monovalent GelVac™ norovirus vaccine formulation, provides a basis for future development of this norovirus VLP vaccine.