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. 2021 Nov 20;224(11):1861–1872. doi: 10.1093/infdis/jiab535

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© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (https://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

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Figure 6. — Germinal center-induced cross-protective immunity. A, Experimental design. Three macaques were challenged with 12.5mL of SARS-CoV-2 virus (2.1×10⁶ TCID₅₀/mL, S clade). After the ASCs from the primary infection had disappeared from all infected macaques, 3 infected macaques were rechallenged at 124 dpi with the SARS-CoV-2 GH clade. Additionally, 3 uninfected monkeys (controls) were challenged at 0 dpi with the same SARS-CoV-2 (GH clade) as that used to reinfect animals. B, IgM and IgG antibody responses specific for SARS-CoV-2 spike (S1+S2) proteins were analyzed using plasma collected at 0, 1, 7, 14, 21, 28, 56, 112, and 124 dpi following the initial infection, using the ELISA (1-way ANOVA with Dunnett test for multiple comparisons vs 0 dpi; ∗P<.05, ∗∗P<.01, ∗∗∗P<.001). C, Representative ELISPOT data of SARS-CoV-2 spike protein (S1+S2)-specific IgM (blue) and IgG (red) ASCs in peripheral blood mononuclear cells of primary-challenged primates. Circles represent individual data (1-way ANOVA with Dunnett test for multiple comparisons vs 0 dpi; ∗∗P<.01, ∗∗∗P<.001). D, Representative ELISPOT data of SARS-CoV-2 spike protein (S1+S2)-specific IgM (blue) and IgG (red)-secreting cells differentiated from MBCs over 4 days using anti-CD3 and anti-CD28 monoclonal antibodies (1 μg/mL). Circles represent individual data (1-way ANOVA with Dunnett test for multiple comparisons vs 0 dpi; ∗P<.05). E, After infection with the S and GH clade, neutralization indicated according to plasma dilution at 124 dpi. F, Virus titers of swab samples in which viral RNA (copies/mL) was quantified using qRT-PCR and TCID₅₀/mL was determined. Circles represent individual data and bar values represent mean±SEM. Abbreviations: ANOVA, analysis of variance; ASC, antibody-secreting cell; CM, cynomolgus macaque; dpi, days postinfection; ELISA, enzyme-linked immunosorbent assay; ELISPOT, enzyme-linked immunospot; Ig, immunoglobulin; MBC, memory B cell; OD, optical density; qRT-PCR, quantitative reverse transcription polymerase chain reaction; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; TCID₅₀, 50% tissue culture infectious dose.