Mpox vaccine and infection-driven human immune signatures: an immunological analysis of an observational study

Abstract

Background: Monkeypox virus has recently infected more than 88 000 people, raising concerns about our preparedness against this emerging viral pathogen. Licensed and approved for mpox, the JYNNEOS vaccine has fewer side-effects than previous smallpox vaccines and has shown immunogenicity against monkeypox in animal models. This study aims to elucidate human immune responses to JYNNEOS vaccination compared with mpox-induced immunity.

Methods: Peripheral blood mononuclear cells and sera were obtained from ten individuals vaccinated with one or two doses of JYNNEOS and six individuals diagnosed with monkeypox virus infection. Samples were obtained from seven individuals before vaccination to serve as a baseline. We examined the polyclonal serum (ELISA) and single B-cell (heavy chain gene and transcriptome data) antibody repertoires and T-cell responses (activation-induced marker and intracellular cytokine staining assays) induced by the JYNNEOS vaccine versus monkeypox virus infection.

Findings: All participants were men between the ages of 21 and 60 years, except for one woman in the group of mpox-convalescent individuals, and none had previous orthopoxvirus exposure. All mpox cases were mild. Vaccinee samples were collected 6-33 days after the first dose and 5-40 days after the second dose. Mpox-convalescent samples were collected 20-102 days after infection. In vaccine recipients, gene-level plasmablast and antibody responses were negligible and sera displayed moderate binding to recombinant orthopoxviral proteins (A29L, A35R, E8L, A30L, A27L, A33R, B18R, and L1R) and native proteins from the 2022 monkeypox outbreak strain. By contrast, recent monkeypox virus infection (within 20-102 days) induced robust serum antibody responses to monkeypox virus proteins and to native monkeypox virus proteins from a viral isolate obtained during the 2022 outbreak. JYNNEOS vaccine recipients presented robust orthopoxviral CD4⁺ and CD8⁺ T-cell responses.

Interpretation: Infection with monkeypox virus resulted in robust B-cell and T-cell responses, whereas immunisation with JYNNEOS elicited more robust T-cell responses. These data can help to inform vaccine design and policies for preventing mpox in humans.

Funding: National Cancer Institute (National Institutes of Health), National Institute of Allergy and Infectious Diseases (National Institutes of Health), and Icahn School of Medicine.

Figure 1.. Antibody repertoires of single B cells after one and two doses of JYNNEOS

(A) Heavy chain variable (VH) sequence diversity was measured using three different parameters. Plasmablasts were collected 6–9 days after one or two doses of JYNNEOS. Total B cells (CD19+) from the same participants were collected before immunization and sorted for single-cell sequencing. (B) Frequency of VH mutations. (C) CDR3 amino acid (AA) lengths. (D) Frequencies of heavy chain gene mutations according to immunoglobulin isotype. Participants are shown by unique symbols.

Figure 2.. Serum antibody responses to recombinant monkeypox and vaccinia proteins, and lysates from mpox-infected cells

(A–D) Serum IgG responses to recombinant monkeypox proteins A29L (A), A35R (B), E8L (C), and A30L (D) at pre-vaccination and 18–60 days post-immunizations or 45–102 days post-infection. AUC, area under the curve. (E–H) Serum IgG responses to recombinant vaccinia proteins A27L (E), A33R (F), B18R (G), and L1R (H) at pre- and post-vaccination or post-mpox infection. (I) Serum IgG responses of pre- and post-vaccination or post-mpox infection to a lysate from mpox-infected cells. Mean with 95% CI are depicted. Dashed lines represent the LOD. Positivity was defined as the mean +3 standard deviations from pre-vaccination participants. p values are listed above the data points. The percentages below the donut graphs describe the percentage of positivity. Comparisons were performed using the Kruskal-Wallis test followed by Dunn’s multiple comparisons test. Appendix p 14 depicts the same data presented as error plots. Appendix p 15 shows additional IgG data from an earlier time points post-immunization.

Figure 3.. Human CD4+ and CD8+ T cell responses to JYNNEOS immunization or mpox infection

(A–B) CD4 T cell responses to the OPXV peptide pool 9–114 days after vaccination and the magnitudes of their AIM (A) or ICS (B) responses pre- and post-vaccination or 20–130 days post-mpox infection. FC, fold change. (C-D) CD8 T cell responses to the OPXV peptide pool after vaccination and the magnitudes of their AIM (C) or ICS (D) responses pre- and post-vaccination or post-mpox infection. (E) OPXV-specific CD4 cTFH cell responses to the OPXV peptide pool after vaccination and AIM magnitudes pre- and post-vaccination or post-mpox infection. (F) Functionality of OPXV-specific CD40L+ CD4 and CD69+ CD8 cytokine responses pre- and post-vaccination or post-mpox infection. (A-D) Geometric mean is depicted and error bars represent 95% CI. (E) Mean is depicted and error bars represent 95% CI. Dashed lines represent the LOS. Positivity was defined as twice the standard deviation from the median. All fold change (FC) graphs depict the geometric mean. The significance of the FC was assessed by Wilcoxon signed-rank test. Pre-vaccination and post-dose two values were compared by Wilcoxon matched pairs signed-rank test. Pre-vaccination and convalescent samples were compared by one-tailed Mann-Whitney test. Dose two and convalescent were compared by two-tailed Mann-Whitney test. p values are listed above the data points. The donut graphs represent the the percentage of positivity. The percentages below the donut graphs describe the positive participants. Appendix p 16 shows the same data presented as error plots. Appendix p 17 shows the gating strategy for the T cell assay and the individual cytokine responses.