Journal: Frontiers in Immunology

Article Title: Immunization with MVA-based vaccines protects K18-hACE2 mice from SARS-CoV-2 infection-associated inflammatory lesions in brains

doi: 10.3389/fimmu.2026.1788665

Figure Lengend Snippet: Study design. Male and female K18-hACE2 mice received PBS, Modified Vaccinia Virus Ankara wild type (MVA-WT), recombinant MVA expressing native (S) or stabilized (ST) SARS-CoV-2 spike protein, nucleocapsid protein (N) or both ST and N proteins prior to intranasal SARS-CoV-2 infection (3.6 × 10 4 TCID50, Germany/BavPat1/2020 strain, NR-52370). (a) Booster experiment - mice were vaccinated twice (day 0 and 21) and infected four weeks later. (b) Prime experiment - mice were immunized only once and infected four weeks later. (c) Emergency experiment – animals were vaccinated once and infected two days later. Mice were sacrificed 6-, 7- and 8 days post infection (dpi). The syringe icon indicates vaccination, the virus icon denotes SARS-CoV-2 infection in the animals, and the red cross marks the day of euthanasia.

Article Snippet: As negative controls, primary antibodies were replaced either by normal rabbit serum for Iba-1 and CD3 (1:3000; #R4505, Sigma-Aldrich Chemie GmbH, Tauffkirchen, Germany) or by ascites fluid from non-immunized BALB/c mice in case of SARS-CoV-2-NP staining (1:1000; #BL CL8100, Cedarlane ® , biologo, Kronshagen, Germany).

Techniques: Modification, Virus, Recombinant, Expressing, Infection

Journal: Frontiers in Immunology

Article Title: Immunization with MVA-based vaccines protects K18-hACE2 mice from SARS-CoV-2 infection-associated inflammatory lesions in brains

doi: 10.3389/fimmu.2026.1788665

Figure Lengend Snippet: In contrast to infected animals from both the PBS [ (a) 6 days post infection (dpi)] and MVA-WT [ (b) 6 dpi] groups, which showed lymphohistiocytic meningoencephalitis with microgliosis and neuroinvasion, K18-hACE2 mice, vaccinated twice [Booster experiment, (c) 8 dpi] or once [Prime experiment, (d) 8 dpi] four weeks prior to infection with MVA-based vaccines expressing stabilized spike and nucleocapsid proteins (MVA-SARS-2-ST/N) showed no inflammatory lesions and no viral spread. Animals immunized with MVA-SARS-2-ST/N two days prior to infection [Emergency experiment, (e) 6 dpi (two left pictures) and at 8 dpi (two right pictures)] also developed lesions, but the inflammatory alterations and the immunopositivity for the viral antigen were less pronounced than in the controls. (a, b) Control animals showed lymphohistiocytic meningoencephalitis, numerous SARS-CoV-2-NP-positive neurons, spiky microglia, and predominantly perivascular T cell infiltration. (c, d) Animals vaccinated twice (c) or once (d) four weeks prior to infection with MVA-SARS-2-ST/N presented no inflammatory changes or neuroinvasion. (e) Animals immunized (MVA-SARS-2-ST/N) once two days prior to infection presented less severe inflammatory changes and a less pronounced spread of viral antigen than the control groups. Bars = 50µm.

Article Snippet: As negative controls, primary antibodies were replaced either by normal rabbit serum for Iba-1 and CD3 (1:3000; #R4505, Sigma-Aldrich Chemie GmbH, Tauffkirchen, Germany) or by ascites fluid from non-immunized BALB/c mice in case of SARS-CoV-2-NP staining (1:1000; #BL CL8100, Cedarlane ® , biologo, Kronshagen, Germany).

Techniques: Infection, Vaccines, Expressing, Control

Journal: Frontiers in Immunology

Article Title: Immunization with MVA-based vaccines protects K18-hACE2 mice from SARS-CoV-2 infection-associated inflammatory lesions in brains

doi: 10.3389/fimmu.2026.1788665

Figure Lengend Snippet: K18-hACE2 mice vaccinated once or twice four weeks prior to infection with MVA-based vaccines expressing native (S) or stabilized spike (ST) protein showed minimal or no inflammatory alterations, no presence of viral antigen or change in microglial morphology, and only minimal T cell infiltration in contrast to non-vaccinated animals from the PBS and MVA-WT groups and animals immunized with a MVA vaccine expressing the viral nucleocapsid (N) protein. Animals immunized with MVA-SARS-2-ST/N two days prior to infection also developed lesions, but the inflammatory changes and immunopositivity for viral antigen were less pronounced than in the control animals. (a-c) Semi-quantitative analysis of hematoxylin and eosin-stained and SARS-CoV-2-NP-immunostained slides as well as quantitative analysis of Iba-1-positive area and CD3-positive T cells in the cerebrum and brain stem of animals immunized with the Booster (a) , Prime (b) and Emergency (c) protocols. Data were tested using the Kruskal–Wallis test followed by Dunn–Bonferroni post hoc testing. Statistical significance was accepted at a p-value of ≤0.05 (*). The graphs show mean (solid line), individual values (dots), and standard deviation (vertical bars).

Article Snippet: As negative controls, primary antibodies were replaced either by normal rabbit serum for Iba-1 and CD3 (1:3000; #R4505, Sigma-Aldrich Chemie GmbH, Tauffkirchen, Germany) or by ascites fluid from non-immunized BALB/c mice in case of SARS-CoV-2-NP staining (1:1000; #BL CL8100, Cedarlane ® , biologo, Kronshagen, Germany).

Techniques: Infection, Vaccines, Expressing, Control, Staining, Standard Deviation

Journal: Frontiers in Immunology

Article Title: Immunization with MVA-based vaccines protects K18-hACE2 mice from SARS-CoV-2 infection-associated inflammatory lesions in brains

doi: 10.3389/fimmu.2026.1788665

Figure Lengend Snippet: In contrast to the animals from control groups (PBS, 6 dpi), which showed multiple neurons (predominantly in the ganglion cell layer) positive for SARS-CoV-2 nucleocapsid protein (NP) in the retina, mice vaccinated four weeks prior to the infection with MVA-SARS-2-ST/N (Booster experiment and Prime experiment, 8 dpi) did not show any viral antigen immunopositivity. Only one animal immunized with MVA-SARS-2-ST/N two days prior to the infection displayed SARS-CoV-2-NP positive neurons in the retina (Emergency experiment, 7 dpi). Abbreviations indicate the retinal layers: NFL, nerve fiber layer; GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; PL, photoreceptor layer; Bars = 50µm.

Article Snippet: As negative controls, primary antibodies were replaced either by normal rabbit serum for Iba-1 and CD3 (1:3000; #R4505, Sigma-Aldrich Chemie GmbH, Tauffkirchen, Germany) or by ascites fluid from non-immunized BALB/c mice in case of SARS-CoV-2-NP staining (1:1000; #BL CL8100, Cedarlane ® , biologo, Kronshagen, Germany).

Techniques: Control, Infection