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.
Abstract
The first-generation Spike-based COVID-19 vaccines reduced the risk of hospitalization, serious illness, and death from SARS-CoV-2 infections. However, waning immunity failed to prevent immune escape, resulting in multiple variants of concern (VOCs) and prolonging the pandemic. We hypothesize 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. In this study, we identified 10 non-Spike antigens common and highly conserved across 8.7 million SARS-CoV-2 strains, prior VOCs, SARS-CoV-1, MERS-CoV, seasonal human cold CoVs, and animal CoVs. Seven antigens were preferentially recognized by CD8
+
and CD4
+
T cells from unvaccinated asymptomatic COVID-19 patients, irrespective of VOC. Three conserved antigens (NSP2, NSP14, Nucleoprotein) administered to golden Syrian hamsters: (
i
) induced high frequencies of lung-resident polyfunctional CXCR5
+
CD4
+
T
FH
cells, GzmB
+
CD4
+
/CD8
+
cytotoxic T cells, and CD69
+
IFN-γ
+
TNFα
+
CD4
+
/CD8
+
effector T cells; (
ii
) reduced morbidity, viral load, lung pathology, and COVID-19-like symptoms from various VOCs, including the pathogenic B.1.617.2 Delta and the recent KP.3 Omicron variants; (
iii
) improved protection conferred by spike-alone mRNA; and (
iv
) conferred protection that lasted for more than 1 year. This multi-antigen CoV vaccine could provide potent, broad-spectrum, and durable cross-protective immunity against current and future variants of concern in the clinic.
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)
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M. Stukova, A. Shurygina, Arman Muzhikyan et al.· Vaccines· 0 citations
The COVID-19 pandemic has substantially reshaped population humoral immunity. However, whether individuals in the post-pandemic era have developed broader cross-neutralizing antibody responses against diverse coronaviruses remains unclear. To address this question, we evaluated serum neutralizing activity in 869 individuals from Wuhan, China, including 78 pre-pandemic samples collected in 2017 and 791 post-pandemic samples collected in 2025. Compared with pre-pandemic sera, post-pandemic sera exhibited enhanced neutralizing activity against multiple sarbecoviruses and the merbecovirus MjHKU4r-CoV-1, with mean viral inhibition increasing by 1.7% to 76.5% at a 1:20 serum dilution, most prominently against clade 1b sarbecoviruses. In contrast, no appreciable enhancement was observed against endemic human alphacoronaviruses or MERS-CoV. Neutralizing responses were strongly correlated across sarbecoviruses, particularly within clade 1b. Antigenic mapping showed that genetic relatedness did not reliably predict antigenic relationships, as Pangolin-GD, Pangolin-GX, and Khosta-2 were genetically more divergent yet antigenically closer to ancestral SARS-CoV-2 (D614G) than contemporary SARS-CoV-2 variants. Notably, both cohorts robustly neutralized Khosta-2, primarily through S1-directed antibodies, suggesting pre-existing cross-reactive immunity induced by endemic human coronaviruses that was further boosted by SARS-CoV-2 exposure. Collectively, these findings demonstrate that post-pandemic sera exhibit enhanced cross-neutralizing antibody responses predominantly against sarbecoviruses, potentially strengthening population immunity against related zoonotic sarbecoviruses and increasing the immunological barrier to their emergence in humans.
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