Intranasal administration of a virus like particles-based vaccine induces neutralizing antibodies against SARS-CoV-2 and variants of concern.

BACKGROUND: The highly contagious SARS-CoV-2 is mainly transmitted by respiratory droplets and aerosols. Consequently, people are required to wear masks and maintain a social distance to avoid spreading of the virus. Despite the success of the commercially available vaccines, the virus is still uncontained globally. Given the tropism of SARS-CoV-2, a mucosal immune reaction would help to reduce viral shedding and transmission locally. Only seven out of hundreds of ongoing clinical trials are testing the intranasal delivery of a vaccine against COVID-19. METHODS: In the current study, we evaluated the immunogenicity of a traditional vaccine platform based on virus-like particles (VLPs) displaying RBD of SARS-CoV-2 for intranasal administration in a murine model. The candidate vaccine platform, CuMVTT -RBD, has been optimized to incorporate a universal T helper cell epitope derived from tetanus-toxin and is self-adjuvanted with TLR7/8 ligands. RESULTS: CuMVTT -RBD vaccine elicited a strong systemic RBD- and spike-IgG and IgA antibodies of high avidity. Local immune response was assessed, and our results demonstrate a strong mucosal antibody and plasma cell production in lung tissue. Furthermore, the induced systemic antibodies could efficiently recognize and neutralize different variants of concern (VOCs). CONCLUSION: Our data demonstrate that intranasal administration of CuMVTT -RBD induces a protective systemic and local specific antibody response against SARS-CoV-2 and its VOCs.

A scalable and highly immunogenic virus-like particle-based vaccine against SARS-CoV-2.

BACKGROUND: SARS-CoV-2 caused one of the most devastating pandemics in the recent history of mankind. Due to various countermeasures, including lock-downs, wearing masks, and increased hygiene, the virus has been controlled in some parts of the world. More recently, the availability of vaccines, based on RNA or adenoviruses, has greatly added to our ability to keep the virus at bay; again, however, in some parts of the world only. While available vaccines are effective, it would be desirable to also have more classical vaccines at hand for the future. Key feature of vaccines for long-term control of SARS-CoV-2 would be inexpensive production at large scale, ability to make multiple booster injections, and long-term stability at 4℃. METHODS: Here, we describe such a vaccine candidate, consisting of the SARS-CoV-2 receptor-binding motif (RBM) grafted genetically onto the surface of the immunologically optimized cucumber mosaic virus, called CuMVTT -RBM. RESULTS: Using bacterial fermentation and continuous flow centrifugation for purification, the yield of the production process is estimated to be >2.5 million doses per 1000-litre fermenter run. We demonstrate that the candidate vaccine is highly immunogenic in mice and rabbits and induces more high avidity antibodies compared to convalescent human sera. The induced antibodies are more cross-reactive to mutant RBDs of variants of concern (VoC). Furthermore, antibody responses are neutralizing and long-lived. In addition, the vaccine candidate was stable for at least 14 months at 4℃. CONCLUSION: Thus, the here presented VLP-based vaccine may be a good candidate for use as conventional vaccine in the long term.

Identifying Key Drivers of Efficient B Cell Responses: On the Role of T Help, Antigen-Organization, and Toll-like Receptor Stimulation for Generating a Neutralizing Anti-Dengue Virus Response.

T help (Th), stimulation of toll-like receptors (pathogen-associated molecular patterns, PAMPs), and antigen organization and repetitiveness (pathogen-associated structural patterns, PASPs) were shown numerous times to be important in driving B-cell and antibody responses. In this study, we dissected the individual contributions of these parameters using newly developed "Immune-tag" technology. As model antigens, we used eGFP and the third domain of the dengue virus 1 envelope protein (DV1 EDIII), the major target of virus-neutralizing antibodies. The respective proteins were expressed alone or genetically fused to the N-terminal fragment of the cucumber mosaic virus (CMV) capsid protein-nCMV, rendering the antigens oligomeric. In a step-by-step manner, RNA was attached as a PAMP, and/or a universal Th-cell epitope was genetically added for additional Th. Finally, a PASP was added to the constructs by displaying the antigens highly organized and repetitively on the surface of CMV-derived virus-like particles (CuMV VLPs). Sera from immunized mice demonstrated that each component contributed stepwise to the immunogenicity of both proteins. All components combined in the CuMV VLP platform induced by far the highest antibody responses. In addition, the DV1 EDIII induced high levels of DENV-1-neutralizing antibodies only if displayed on VLPs. Thus, combining multiple cues typically associated with viruses results in optimal antibody responses.

Preclinical Evaluation of Novel Sterically Optimized VLP-Based Vaccines against All Four DENV Serotypes.

Over the past few decades, dengue fever has emerged as a significant global health threat, affecting tropical and moderate climate regions. Current vaccines have practical limitations, there is a strong need for safer, more effective options. This study introduces novel vaccine candidates covering all four dengue virus (DENV) serotypes using virus-like particles (VLPs), a proven vaccine platform. The dengue virus envelope protein domain III (EDIII), the primary target of DENV-neutralizing antibodies, was either genetically fused or chemically coupled to bacteriophage-derived AP205-VLPs. To facilitate the incorporation of the large EDIII domain, AP205 monomers were dimerized, resulting in sterically optimized VLPs with 90 N- and C-termini. These vaccines induced high-affinity/avidity antibody titers in mice, and confirmed their protective potential by neutralizing different DENV serotypes in vitro. Administration of a tetravalent vaccine induced high neutralizing titers against all four serotypes without producing enhancing antibodies, at least not against DENV2. In conclusion, the vaccine candidates, especially when administered in a combined fashion, exhibit intriguing properties for potential use in the field, and exploring the possibility of conducting a preclinical challenge model to verify protection would be a logical next step.

Preclinical Development of a Novel Zika Virus-like Particle Vaccine in Combination with Tetravalent Dengue Virus-like Particle Vaccines.

Declared as a Public Health Emergency in 2016 by the World Health Organization (WHO), the Zika virus (ZIKV) continues to cause outbreaks that are linked to increased neurological complications. Transmitted mainly by Aedes mosquitoes, the virus is spread mostly amongst several tropical regions with the potential of territorial expansion due to environmental and ecological changes. The ZIKV envelope protein's domain III, crucial for vaccine development due to its role in receptor binding and neutralizing antibody targeting, was integrated into sterically optimized AP205 VLPs to create an EDIII-based VLP vaccine. To increase the potential size of domains that can be accommodated by AP205, two AP205 monomers were fused into a dimer, resulting in 90 rather than 180 N-/C- termini amenable for fusion. EDIII displayed on AP205 VLPs has several immunological advantages, like a repetitive surface, a size of 20-200 nm (another PASP), and packaged bacterial RNA as adjuvants (a natural toll-like receptor 7/8 ligand). In this study, we evaluated a novel vaccine candidate for safety and immunogenicity in mice, demonstrating its ability to induce high-affinity, ZIKV-neutralizing antibodies without significant disease-enhancing properties. Due to the close genetical and structural characteristics, the same mosquito vectors, and the same ecological niche of the dengue virus and Zika virus, a vaccine covering all four Dengue viruses (DENV) serotypes as well as ZIKV would be of significant interest. We co-formulated the ZIKV vaccine with recently developed DENV vaccines based on the same AP205 VLP platform and tested the vaccine mix in a murine model. This combinatory vaccine effectively induced a strong humoral immune response and neutralized all five targeted viruses after two doses, with no significant antibody-dependent enhancement (ADE) observed. Overall, these findings highlight the potential of the AP205 VLP-based combinatory vaccine as a promising approach for providing broad protection against DENV and ZIKV infections. Further investigations and preclinical studies are required to advance this vaccine candidate toward potential use in human populations.