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. 2021 Jun 18;22(8):e52447. doi: 10.15252/embr.202152447

Figure 7. cGAMP‐VLPs containing the SARS‐CoV‐2 S protein induce an enhanced antibody response.

Figure 7

  • A
    cGAMP‐S‐VLPs and Empty‐S‐VLPs incorporate SARS‐CoV‐2 S. Lysates from VLP producer cells and VLP preparations were analysed by Western blot for the presence of the S2 subunit of SARS‐CoV‐2 S, Gag‐GFP and actin using the indicated antibodies.
  • B, C
    Immunisation with cGAMP‐S‐VLPs augments anti‐Spike and anti‐RBD antibody titres. Mice were immunised via the intra‐muscular route with 5 × 105 IU of cGAMP‐S‐VLPs, Empty‐S‐VLPs or PBS as a control. Three weeks after immunisation, sera were collected, heat‐inactivated, and titres of antibodies capable of binding to SARS‐CoV‐2 S (B) or its RBD (C) were determined by ELISA. The antibody response was expressed as end‐point titre defined as the reciprocal of the highest serum dilution that gives a positive signal (blank+10SD). The dotted line shows the limit of detection (LOD).
  • D
    Immunisation with cGAMP‐S‐VLPs induces neutralising antibodies. Using serum samples from (B), antibody titres capable of neutralising SARS‐CoV‐2 were determined by microneutralisation (MN) assay. Calculated IC50 doses from multiple serum dilutions are shown. The dotted line shows the LOD.

Data information: Panel (A) is representative of two independent experiments. In (B‐D), data were pooled from two independent experiments including a total of 12 mice per condition; symbols show data from individual animals. Horizontal lines indicate the mean. Statistical analyses were done using a Kruskal–Wallis test followed by Dunn’s multiple comparisons test (B, C, D). *P < 0.05; ****P < 0.0001. See also Fig EV5.