Aug 2026· Vaccine· Vol 91, pp.
129073
· 0 citations· 60 references
Medicine
TL;DR
Combining AddaS03 and Poly I:C adjuvants is a potent strategy to modulate and enhance immune responses elicited by an RBD-based vaccine.
Abstract
Background
The COVID-19 pandemic caused over seven million deaths, and disease control relied largely on mass immunization campaigns. Although diverse vaccine platforms were used, most formulations targeted the Spike protein because of its central role in virus entry. Persistent viral evolution and global vaccine inequity highlight the need for alternative strategies, particularly for low- and middle-income countries. In this scenario, recombinant protein-based vaccines are attractive due to low cost, established manufacturing pipelines and well-characterized safety profiles. The receptor binding domain (RBD) of Spike is an appealing antigen due to its relatively simple structure, proven immunogenicity - especially in multimerized formats - and because it harbors most neutralizing antibody epitopes. Protein-based vaccines, however, rely on the use of adjuvants to optimize antigen-specific immunity.
Methods
We used an RBD dimer derived from the ancestral Wuhan strain as a well-characterized protein to evaluate the humoral and cellular immunogenicity of combined AddaS03 and Poly I:C adjuvants in BALB/c mice.
Results
The adjuvant combination preserved the strong humoral responses typically induced by AddaS03 while conferring the Th1-skewing properties of Poly I:C, producing a synergistic effect that exceed those of each adjuvant alone. Specifically, the combination improved antibody affinity, increased the generation of antibody- secreting cells in spleen and bone marrow, and enhanced the induction of polyfunctional, cytokine-producing CD4+ T cells. Additionally, we mapped and characterized three class II T cell epitopes within RBD: peptide 6 (351-YAWNRKRISNCVADYSV-367), peptide 19 (442-SKVGGNYNYLYRLFRK-458) and peptide 20 (449-YNYLYRLFRKSNLKPFE-465).
Conclusions
Combining AddaS03 and Poly I:C adjuvants is a potent strategy to modulate and enhance immune responses elicited by an RBD-based vaccine.
Safe, effective, durable, and broadly deployable vaccines are needed for sustainable control of hepatitis C virus (HCV) that poses a significant global public health threat. We reported the preclinical development of a novel HCV vaccine candidate engineered by formulating a novel native-like secreted E1E2 immunogen and a well-established combinatorial adjuvant of QS-21 + 3D-(6-acyl) PHAD into our unique microneedle patches (MNPs).
In C57BL/6 mice, we evaluated (1) the local immunomodulation characteristics by RT-qPCR; (2) the local and systemic reactogenicity; (3) humoral responses by ELISA and pseudovirus neutralization; and (4) cellular responses by antigen-specific stimulation of isolated splenocytes, followed by intracellular cytokine staining and flow cytometry. Intramuscular vaccination (IM) was used as a benchmark group. In human skin explants, we studied the effect of MNP-delivered adjuvant on the subsets and phenotypes of skin-migratory dendritic cells by flow cytometry.
Our HCV vaccine efficiently and safely (with no systemic and local reactogenicity) engineered the skin immune system in mice to induce proinflammatory milieu at the vaccine-targeted tissues with increased Nlrp3, Ifng, and Cxcl10 expression. In human skin explants, our HCV vaccine stimulated the migration of highly immunostimulatory antigen-presenting cells, supported by enhanced expression of co-stimulatory molecules, such as CD86 and CD83. Skin immunization of mice with our HCV vaccine elicited improved humoral (higher binding and neutralizing antibodies with enhanced Th1-skewing) and cellular polyfunctional T-cells responses compared to IM immunization. The formulation preserved potency for 3 months at 40 °C, indicating thermostability.
Unique safety, shelf-stability, innate and adaptive immunogenicity advantages of MNP-based skin immunization would enable the development of clinically translatable and globally accessible HCV vaccines with rationally designed antigens and adjuvants.
Department of Dermatology, University of Pittsburgh
Vaccines and Immunotherapy (VAC)
Yinuo Zhang, A. Dhayani, Stephen C. Balmert 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.
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Vaccines and Immunotherapy (VAC)
Michael Powell, Nicholas G. Battaglia, Lee-Jah Chang et al.· Journal of Immunology· 0 citations
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
Porcine epidemic diarrhea virus (PEDV) causes severe enteric disease in piglets, with mortality approaching 100% in naïve herds and extensive global economic losses. Protection relies on maternal vaccination to confer lactogenic immunity; however, current vaccines provide incomplete protection. To improve the immunogenicity of spike-based subunit vaccines, we developed a recombinant S1-nucleocapsid (N) fusion antigen, combining the S1 domain, which contains multiple neutralizing epitopes, with highly conserved N protein within a single immunogen. The antigen formed heterogeneous multimeric assemblies when expressed in mammalian cells and was formulated with Montanide™ Gel 02 PR or ISA 61 VG adjuvants. Immunogenicity was evaluated in BALB/c mice using a prime-boost intramuscular vaccination regimen by assessing antigen-binding and neutralizing antibodies, as well as IFN-γ- and IL-5-secreting cells. Vaccination induced robust IgG, IgG1, IgG2a, and IgA responses against both S1 and N, with higher neutralizing antibody titers in the Gel 02 PR group than the ISA 61 VG group. Adjuvant formulation influenced cytokine response patterns. Both Gel 02 PR and ISA 61 formulations showed higher IFN-γ and IL-5 responses than the control group with Gel 02 inducing highest IFN-γ levels amongst the groups. These pre-clinical findings demonstrate that the S1-N-T4f fusion antigen is a promising vaccine candidate for further evaluation of its protective potential against PEDV infection.
Mario Fragoso-Saavedra, Brittany Thivierge, Qiang Liu· Microbial Pathogenesis· 0 citations
ABSTRACT Pseudomonas aeruginosa (Pa) is a ubiquitous, opportunistic nosocomial pathogen that poses a significant threat due to its innate and acquired multidrug resistance. Novel vaccine strategies are urgently needed for vulnerable populations, many of which harbor pre-existing immunity from prior encounters with Pa. Here, we evaluated a multivalent subunit vaccine combining type III secretion system (T3SS) antigens and exolysin A (ExlA) in a nanoemulsion formulation using a clinically relevant murine pulmonary pre-exposure model. This approach allowed us to determine whether vaccination could overcome the limitations of the host’s initial, ineffective immune response. Vaccination fundamentally transforms suboptimal baseline memory into a potent, multi-faceted Th1/Th17-polarized response. This globally transformed signature was characterized by significantly enhanced antigen-specific IFN-γ and IL-17A production, both locally and systematically in the lung, with exceptionally large biological effect sizes (Cohen’s d values reaching 21.35). By utilizing log10 transformation to accurately reflect pathogen growth kinetics, we demonstrated that this vaccine-augmented immunity conferred statistically significant protection following heterologous challenge. In the twice-exposed cohort, vaccination promoted superior bacterial clearance of the T3SS-positive strain, though clearance of the ExlA-positive strain was not enhanced, potentially due to immunological interference from pre-existing T3SS memory. In the thrice-exposed cohort, a functional protective threshold was observed, where high levels of natural immunity matched the vaccine-induced clearance levels. Our findings established that our vaccine formulation can effectively boost and redirect pre-existing immunity, offering a promising approach to overcome the limitations of natural exposure and protect at-risk individuals from diverse Pa infections.
D. R. Howlader, Sayan Das, Satabdi Biswas et al.· Infection and Immunity· 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.
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Vaccines and Immunotherapy (VAC)
Tianyi Zhang, Nicholas Magazine, Lamis El-Baz et al.· Journal of Immunology· 0 citations