This characterized virion-mimetic structural vaccine not only induces the production of high-efficiency antibodies against both the spike and N proteins but also elicits robust S1-specific and N-specific CTL responses in animal models, creating an optimal microenvironment for eliciting potent and broad-spectrum adaptive immune responses.
Abstract
In the present study, by building on the previous development of a DC-SIGN-targeting virus-like structure (VLS) vaccine platform and a comprehensive characterization of SARS-CoV-2 structural biology, particularly insights into the role of the nucleocapsid (N) protein in eliciting cytotoxic T lymphocyte (CTL) responses during infection, we designed a SARS-CoV-2 virion-mimetic structural vaccine that encapsulates an mRNA encoding the spike S1 antigen complexed with N protein complexes, with S1 proteins loaded on its surface. This characterized virion-mimetic structural vaccine not only induces the production of high-efficiency antibodies against both the spike and N proteins but also elicits robust S1-specific and N-specific CTL responses in animal models. Furthermore, the generated antibodies exhibit cross-reactive neutralizing activity against multiple SARS-CoV-2 variants and provide protective immunity against challenge with mutant viruses in immunized hosts. This SARS-CoV-2 virion-mimetic structure effectively recapitulates natural infection pathways, comprehensively activating the innate immune system and thereby creating an optimal microenvironment for eliciting potent and broad-spectrum adaptive immune responses.
It is shown that a Wuhan-lineage-based multi-antigen VLP vaccine can provide cross-protection against an antigenically divergent SARS-CoV-2 variant that is not fully explained by detectable serum neutralizing activity alone, suggesting the importance of integrated immune responses involving humoral, cellular, and local immune mechanisms.
Seung-Ji Kim, Howon Kim, Seung-Eun Son et al.· Vaccine· 0 citations
The emergence of the SARS-CoV-2 pandemic led to the spread of highly transmissible variants, such as the Delta variant, which originated in India, underscoring the urgent need to develop new antivirals, therapeutics, and vaccines. In our previous study, we showed that Membrane-Envelope Virus-like Particles exhibit antigenicity and neutralization activity. Hence, our present study was conducted to evaluate whether the M protein alone can form VLPs that elicit an immune response. Using computational methods, we identified key interacting residues in M-protein that contribute to VLP formation and interact with other structural proteins, including Spike (S), Nucleocapsid (N), and Envelope (E). The SARS-CoV-2-M protein was expressed in Sf-21 insect cells, and the resulting VLPs were purified, analyzed for shape and size, and characterized using DLS, FESEM, and TEM. The purified VLPs were injected into BALB/c mice to evaluate their immune response compared with uninfected controls. The biophysical analysis confirms that the particles are round and have a size of ~ 180–200 nm. The serum levels of IgG, IgM, and IgA were found to be higher in immunized mice than in uninfected mice. Further qRT-PCR analysis demonstrated the levels of IFN-γ, IL-2, and IL-12, indicating a TH1-biased immune response against the M protein. Our study demonstrates that the highly conserved M protein can self-assemble into VLPs and elicit humoral and cellular immune response. Furthermore, our study indicates that while M-protein VLPs elicit significant antibodies and cytokine responses, they do not induce detectable neutralizing activity when given alone.
Akash Kumar, K. K. Inampudi, Vikas Kumar et al.· Virology Journal· 0 citations
Over the past two decades, three major coronavirus (CoV) outbreaks–SARS, MERS, and COVID-19–have occurred, all caused by Beta-coronaviruses. Future outbreaks of yet-undiscovered CoVs with pandemic potential are anticipated. This underscores the urgent need for a broadly protective CoV vaccine. We hypothesize that targeting conserved regions of the CoV genome, such as the membrane (M) and nucleocapsid (N) proteins shared across Sarbecoviruses, can provide cross-protective immunity.
To induce mucosal immune responses at the site of CoV infection (upper respiratory tract), we used papillomavirus-like particles (VLPs) as a delivery vector. Vaccine constructs were designed using rearranged SARS-CoV-2 Omicron-XEC M and N sequences fused to ubiquitin to enhance antigen processing and T cell activation. These constructs were cloned into a pVax1 vector and expressed in HEK293T cells. Expression was confirmed by RT-PCR and Western blotting. The constructs were then packaged into pseudoviruses using bovine papillomavirus VLPs. Mice were immunized with these pseudoviruses.
Intracellular cytokine staining revealed antigen-specific T cell responses in lymph nodes and spleens of immunized mice following peptide stimulation. These responses were absent in control animals. Furthermore, vaccinated transgenic K18-hACE2 mice showed protection against heterologous challenge with SARS-CoV-2 Omicron-KP.3, indicating cross-variant efficacy.
Our findings demonstrate that mucosal delivery of conserved CoV antigens via papillomavirus VLPs induces strong, antigen-specific T cell responses and protects against heterologous SARS-CoV-2 challenge. This strategy shows promise for developing a pan-coronavirus vaccine.
NIH
Vaccines and Immunotherapy (VAC)
Aidan Dorn, Hansam Cho, Lanying Du et al.· Journal of Immunology· 0 citations
mRNA-encoded virus-like particles (VLPs) are an emerging advancement in vaccine technology, enabling the self-assembly of viral antigens into structures that closely resemble native viruses. This innovative approach to conventional mRNA vaccination may boost vaccine-induced adaptive immune responses and allow for reduced dosing. To evaluate this technology, we developed AZD6563, an mRNA VLP vaccine targeting the COVID-19 XBB1.5 spike variant.
The phase 1 clinical study ARTEMIS-C was conducted to assess cellular immunogenicity in adults aged 18—64 years and ≥65 years following administration of AZD6563 (5 µg or 10 µg) or the licensed BNT162b2 XBB.1.5 mRNA vaccine (30 µg).
AZD6563 drove spike-specific CD4+ and CD8+ T cell responses comparable to those elicited by higher dose of BNT162b2. Functional analysis of these cells revealed similar cytokine production profiles across groups; however, the 10µg dose of AZD6563 led to higher TCR diversity within the ≥65-year cohort. Notably, expansion of spike-specific B cells was most pronounced in the AZD6563 10µg group, with marked increases in cross-reactive XBB.1.5 spike-specific B cells that also recognized Omicron BA.4/5 and ancestral SARS-CoV-2 variants.
Collectively, these results demonstrate that AZD6563, at reduced doses, matches the cellular immunogenicity of BNT162b2 while enhancing B cell cross-reactivity and TCR diversity in older adults, supporting its potential as a next-generation COVID-19 vaccine candidate.
n/a
Vaccines and Immunotherapy (VAC)
Michael Powell, Nicholas G. Battaglia, Lee-Jah Chang et al.· Journal of Immunology· 0 citations
The rapid evolution and immune evasion of the Spike (S) protein in canine coronavirus type II (CCoV-II) necessitate the development of vaccines with enhanced durability and broad-spectrum efficacy. Circular RNA (circRNA) offers a superior platform to linear mRNA due to its covalently closed structure, which resists exonuclease degradation and ensures sustained antigen expression. In this study, we designed a multiepitope circRNA vaccine targeting conserved CTL, HTL, and LBL epitopes of the CCoV-II S protein, encapsulated in lipid nanoparticles (LNPs). The LNP-circRNA formulations exhibited high physicochemical stability and robust S protein expression in vitro. In both murine and canine models, the vaccine elicited potent S-specific IgG and neutralizing antibody titers, significantly enhancing T follicular helper (Tfh) cell and germinal center B (GC) cell responses. Crucially, vaccinated dogs challenged with virulent CCoV-II showed markedly reduced viral shedding, attenuated clinical symptoms, and preserved intestinal integrity without systemic inflammatory adverse effects. These results demonstrate that the multiepitope circRNA vaccine induces robust, long-term immune protection, establishing it as a highly effective next-generation candidate for the prevention of CCoV-II infection.
Xiaoyu Zhang, Lingli Wang, Wenna He et al.· Veterinary Microbiology· 0 citations
It is hypothesized that next-generation CoV vaccines incorporating highly conserved SARS-CoV-2 T cell antigens would confer potent, broad, long-lasting cross-protective immunity against multiple VOCs.
Swayam Prakash, N. Dhanushkodi, Afshana Quadiri et al.· npj Vaccines· 0 citations