tetano
Editor, Senior Moderator
Front Immunol
. 2025 Nov 11:16:1694699.
doi: 10.3389/fimmu.2025.1694699. eCollection 2025. Multi-antigen MVA-vectored SARS-CoV-2 vaccine, GEO-CM04S1, induces cross-protective immune responses to ancestral and Omicron variants
Amany Elsharkawy[SUP] 1 [/SUP], Shannon Stone[SUP] 1 [/SUP], Anchala Guglani[SUP] 1 [/SUP], Felix Wussow[SUP] 2 [/SUP], J D Burleson[SUP] 2 [/SUP], Mary Hauser[SUP] 2 [/SUP], Arban Domi[SUP] 2 [/SUP], Pratima Kumari[SUP] 2 [/SUP], Todd R Albrecht[SUP] 2 [/SUP], Chinonye Dim[SUP] 1 [/SUP], Mark Newman[SUP] 2 [/SUP], Don J Diamond[SUP] 3 [/SUP], Sreenivasa Rao Oruganti[SUP] 2 [/SUP], Mukesh Kumar[SUP] 1 [/SUP]
Affiliations
The design focus of the first-generation COVID-19 vaccines was on the use of the SARS-CoV-2 spike (S) protein as the primary vaccine immunogen to induce high levels of neutralizing antibodies. Efficacy was repeatedly disrupted due to the diminished neutralizing capacity of vaccine-induced antibodies against emerging variants. Vaccine candidate GEO-CM04S1 is based on the use of a modified vaccinia Ankara vector (MVA) that co-expresses S and nucleocapsid (N) antigens of the Wuhan-Hu-1 reference strain. It is designed to induce both antibody and T-cell responses to both S and N, with the goal of broadening immune response specificity and function. Herein, we characterized GEO-CM04S1 vaccine induced immune responses and efficacy against the ancestral Wuhan strain B.1 and the Omicron subvariant XBB.1.5 in K18-hACE-2 mouse model. We also tested experimental vaccine candidates that encode either S or N proteins alone and determined their relative levels and immunogenicity and contribution to efficacy. We demonstrated that immune responses induced by GEO-CM04S1 protects against weight loss, upper and lower respiratory tract infection, lung injury and excessive inflammation following intranasal challenge with B.1. We showed that only GEO-CM04S1 maintained full protective efficacy against the Omicron subvariant XBB.1.5. GEO-CM04S1 vaccination reduced viral replication without significant lung damage following XBB.1.5 infection. Despite full protection, no neutralizing antibodies were detected against XBB.1.5 in the sera of GEO-CM04S1-immunized animals, suggesting a critical role of T-cell responses. Using antibody-mediated depletion, we showed that depletion of CD20 cells or CD8[SUP]+[/SUP] T cells did not impact the vaccine protective efficacy whereas depletion of CD4[SUP]+[/SUP] T-cells diminished levels of efficacy. Collectively, our data demonstrate the full cross-variant protective immunity induced by GEO-CM04S1 and that CD4[SUP]+[/SUP] T-cell responses are a major effector element of vaccine protection.
Keywords: B.1; COVID-19; K18-hACE-2; SARS-CoV-2; T-cells; XBB.1.5; vaccine.
. 2025 Nov 11:16:1694699.
doi: 10.3389/fimmu.2025.1694699. eCollection 2025. Multi-antigen MVA-vectored SARS-CoV-2 vaccine, GEO-CM04S1, induces cross-protective immune responses to ancestral and Omicron variants
Amany Elsharkawy[SUP] 1 [/SUP], Shannon Stone[SUP] 1 [/SUP], Anchala Guglani[SUP] 1 [/SUP], Felix Wussow[SUP] 2 [/SUP], J D Burleson[SUP] 2 [/SUP], Mary Hauser[SUP] 2 [/SUP], Arban Domi[SUP] 2 [/SUP], Pratima Kumari[SUP] 2 [/SUP], Todd R Albrecht[SUP] 2 [/SUP], Chinonye Dim[SUP] 1 [/SUP], Mark Newman[SUP] 2 [/SUP], Don J Diamond[SUP] 3 [/SUP], Sreenivasa Rao Oruganti[SUP] 2 [/SUP], Mukesh Kumar[SUP] 1 [/SUP]
Affiliations
- PMID: 41306976
- PMCID: PMC12645453
- DOI: 10.3389/fimmu.2025.1694699
The design focus of the first-generation COVID-19 vaccines was on the use of the SARS-CoV-2 spike (S) protein as the primary vaccine immunogen to induce high levels of neutralizing antibodies. Efficacy was repeatedly disrupted due to the diminished neutralizing capacity of vaccine-induced antibodies against emerging variants. Vaccine candidate GEO-CM04S1 is based on the use of a modified vaccinia Ankara vector (MVA) that co-expresses S and nucleocapsid (N) antigens of the Wuhan-Hu-1 reference strain. It is designed to induce both antibody and T-cell responses to both S and N, with the goal of broadening immune response specificity and function. Herein, we characterized GEO-CM04S1 vaccine induced immune responses and efficacy against the ancestral Wuhan strain B.1 and the Omicron subvariant XBB.1.5 in K18-hACE-2 mouse model. We also tested experimental vaccine candidates that encode either S or N proteins alone and determined their relative levels and immunogenicity and contribution to efficacy. We demonstrated that immune responses induced by GEO-CM04S1 protects against weight loss, upper and lower respiratory tract infection, lung injury and excessive inflammation following intranasal challenge with B.1. We showed that only GEO-CM04S1 maintained full protective efficacy against the Omicron subvariant XBB.1.5. GEO-CM04S1 vaccination reduced viral replication without significant lung damage following XBB.1.5 infection. Despite full protection, no neutralizing antibodies were detected against XBB.1.5 in the sera of GEO-CM04S1-immunized animals, suggesting a critical role of T-cell responses. Using antibody-mediated depletion, we showed that depletion of CD20 cells or CD8[SUP]+[/SUP] T cells did not impact the vaccine protective efficacy whereas depletion of CD4[SUP]+[/SUP] T-cells diminished levels of efficacy. Collectively, our data demonstrate the full cross-variant protective immunity induced by GEO-CM04S1 and that CD4[SUP]+[/SUP] T-cell responses are a major effector element of vaccine protection.
Keywords: B.1; COVID-19; K18-hACE-2; SARS-CoV-2; T-cells; XBB.1.5; vaccine.