Aug 2026· Vaccine· Vol 91, pp.
129059
· 0 citations· 68 references
Medicine
TL;DR
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.
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to evolve through mutations in the spike (S) protein, leading to antigenically divergent variants such as the Omicron sublineage JN.1 that markedly reduce vaccine-induced neutralizing antibody activity. These limitations highlight the need for vaccine strategies that can induce multilayered protective immunity rather than relying solely on S protein-targeted immunity. Here, we developed a Wuhan-lineage-based multi-antigen virus-like particle (VLP) vaccine incorporating S, envelope (E), membrane (M), and nucleocapsid (N) proteins using a baculovirus dual-expression system. Mice were primed intramuscularly and boosted via either the intramuscular or intranasal route, and humoral, mucosal, and cellular immune responses were evaluated. Both vaccination regimens induced robust systemic IgG responses, whereas mucosal IgA responses were selectively enhanced following intranasal boosting. Sera from VLP-immunized mice efficiently neutralized the homologous Wuhan-lineage strain but showed no detectable neutralizing activity against the JN.1 variant. Despite this, VLP immunization elicited antigen-specific CD4+ and CD8+ T cell responses in both pulmonary and systemic compartments. In a highly susceptible K18-hACE2 mouse model, VLP immunization completely prevented mortality following challenge with both the ancestral Wuhan-lineage strain and the JN.1 variant and markedly suppressed viral replication in respiratory tissues. Histopathological analysis further showed minimal interstitial lung lesions with organized perivascular lymphocytic infiltration in vaccinated mice, while pulmonary cytokine analysis revealed qualitatively distinct immune response patterns depending on the challenge strain and vaccination status. Our findings show 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.
Immune imprinting is a phenomenon in which prior antigen exposure limits variant-specific de novo immune responses to subsequent related antigens. The serum response to Omicron boosters in mice and human are strongly imprinted by prior vaccines encoding SARS-CoV-2 Wuhan-1 spike (e.g., mRNA-1273). Strategies including changes of dosage and interval have had limited success in enhancing variant-specific immunity. Intranasal (i.n.) vaccination is a promising approach that elicits mucosal and systemic immunity. Here we analysed the response of variant boosters delivered i.m. or i.n. after mRNA-1273 priming at the serum, cellular, and B cell repertoire levels to understand how boosting routes modulate the imprinting effect.
C57BL/6 mice were primed i.m. with mRNA-1273 and heterologously boosted i.m. or i.n. with a chimpanzee adenoviral-vectored vaccine (ChAd-SARS-CoV-2-S) against XBB.1.5 spike. Serum and bronchoalveolar lavage fluid (BALF) were analysed for cross-reactive and strain-specific spike-binding IgG/IgA. Neutralizing activity was assessed using pseudovirus neutralization assays. Cross-reactive and strain-specific spike-binding memory B cells (MBCs) in draining lymph nodes (dLNs) were quantified. Ongoing studies are using single-cell BCR sequencing to analyse plasmablast clonotypes, with selected ones expressed as mAbs for functional and epitope analyses.
Intranasal boosting with ChAd-SARS-CoV-2-S against XBB.1.5 spike induced higher fractions of XBB.1.5-specific serum IgG and BALF IgA with greater neutralizing activity. Intranasal vaccination increased XBB.1.5-specific MBCs in dLNs, indicating a route-dependent shift in B cell specificity.
Intranasal boosting promotes greater variant-specific response at both the serum and cellular levels than i.m. boosting. Ongoing B cell repertoire and mAb analyses will provide mechanistic insight into how vaccination route reshapes clonal selection and maturation, informing rational vaccination design.
Moderna and NIH R01AI157155
Vaccines and Immunotherapy (VAC)
Xinyi Liu, Chieh-Yu Liang, Michael S. Diamond· Journal of Immunology· 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
Its ability to limit viral shedding from the upper respiratory tract and to mitigate SARS-CoV-2-induced pulmonary pathology, contributing to the preservation of lung vascular integrity, underscores the utility of mucosal immunization with Corfluvec as a valuable intranasal complement to current systemic vaccination strategies.
M. Stukova, A. Shurygina, Arman Muzhikyan et al.· Vaccines· 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
SARS-CoV-2 spike—based vaccines control COVID-19, yet vaccine-associated enhanced respiratory disease (VAERD) after breakthrough infection remains a concern. We previously reported Th2/Th17-skewed VAERD in hACE2 mice, however, the mechanisms, durability, and effects of vaccine types and routes in this process are unclear and will be investigated here.
Wild-type mice received spike protein plus alum/CpG and were challenged with MA10 strain 14 days or 7 months post-boost. Parallel cohorts received intramuscular (IM) mRNA vaccines (Comirnaty or Spikevax) and were challenged at 7 months. Splenocytes were restimulated with spike peptide subpools to map Th2/Th17-associated epitopes. B cell or ITK deficient mice were used to define signaling requirements. We also used model antigen ovalbumin (OVA) as a control to test whether the observed Th2/Th17 phenotype is uniquely associated with intranasal spike following IM subunit vaccination. To further assess booster safety, IM mRNA vaccinated mice were boosted with intramuscular mRNA vaccine or intranasal Ad5-Spike.
Despite protection, adjuvanted protein vaccination caused severe lung pathology with CD4+ T infiltration and elevated Th2/Th17 cytokines, persisting to 7 months. mRNA vaccines did not induce Th2/Th17-associated VAERD at delayed challenge. Th2/Th17-linked epitopes localized to S1, and both B cells and ITK signaling were required for pulmonary inflammation. Compared with OVA, intranasal spike after intramuscular adjuvanted vaccination recruited additional lung Th17 cells. For boosting, intramuscular mRNA was markedly safer than intranasal Ad5-Spike, which triggered robust Th2/Th17 inflammation.
VAERD risk can persist long after vaccination and depends on platform and delivery route. Intramuscular mRNA vaccines show superior safety, while spike contains epitopes capable of driving Th2- and Th17-mediated pathology, highlighting the need to refine spike antigens and booster strategies for durable, safe protection.
n/a
Vaccines and Immunotherapy (VAC)
Tianyi Zhang, Nicholas Magazine, Lamis El-Baz 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