Pre-existing yellow fever immunity impairs and modulates the antibody response to tick-borne encephalitis vaccination

Abstract

Flaviviruses have an increasing global impact as arthropod-transmitted human pathogens, exemplified by Zika, dengue, yellow fever (YF), West Nile, Japanese encephalitis, and tick-borne encephalitis (TBE) viruses. Since all flaviviruses are antigenically related, they are prone to phenomena of immunological memory ('original antigenic sin'), which can modulate immune responses in the course of sequential infections and/or vaccinations. In our study, we analyzed the influence of pre-existing YF vaccine-derived immunity on the antibody response to TBE vaccination. By comparing samples from YF pre-vaccinated and flavivirus-naive individuals, we show that YF immunity not only caused a significant impairment of the neutralizing antibody response to TBE vaccination but also a reduction of the specific TBE virus neutralizing activities (NT/ELISA-titer ratios). Our results point to a possible negative effect of pre-existing cross-reactive immunity on the outcome of flavivirus vaccination that may also pertain to other combinations of sequential flavivirus infections and/or vaccinations.

Keywords: Viral infection; Virology.

Fig. 1

Structure of TBE virus E protein and TBE vaccination schedule. a Ribbon diagram of the TBE virus E dimer (PDB: 5O6A;) in side view and b surface representation of TBE virus E dimer (PDB: 1SVB;) in top view (lacking the stem and transmembrane domains (TMD)). Color code: DI, red; DII, yellow; DIII, blue; stem, green; TMD, gray; the fusion loop (FL) is highlighted in orange. c Time schedule of TBE vaccination (top – blue arrows) and blood withdrawals (bottom – red arrows). The structures were generated with PyMol (Schrödinger, LLC; www.pymol.org) using published PDB files (https://www.rcsb.org)

Fig. 2

ELISA and neutralization tests of TBE post-vaccination plasma pools. Blue lines and filled symbols (mean values): Plasma pools of flavivirus-naive group. Red lines and filled symbols (mean values): Plasma pools of YF pre-vaccinated group. Open circles show results of independent experiments. Testing was performed in TBE and YF ELISA (a, c), as well as TBE and YF NT (b, d) at five different time points in the course of TBE vaccination (Fig. 1c). Arrows indicate time points of vaccination. Error bars represent the standard errors of the means (SEM) calculated from at least three independent experiments. Asterisks indicate significant differences between the two groups at the different time points (measured by t-test): **P < 0.01; ***P < 0.001; ****P < 0.0001

Fig. 3

Den and RB ELISA of TBE post-vaccination plasma pools. Blue lines and filled symbols (mean values): Plasma pools of flavivirus-naive group. Red lines and filled symbols (mean values): Plasma pools of YF pre-vaccinated group. Open circles show results of independent experiments. Testing was performed in a Den and b RB ELISA at five different time points in the course of TBE vaccination (Fig. 1c). Arrows indicate time points of vaccination. Error bars represent the SEM calculated from at least three independent experiments. Asterisks indicate significant differences between the two groups at the different time points (measured by t-test): **P < 0.01; ***P < 0.001

Fig. 4

ELISA of TBE post-vaccination plasma pools at time point 28 weeks before (control) and after depletion of cross-reactive antibodies with RB sE. Blue columns (mean values): Plasma pool of flavivirus-naive group. Red columns (mean values): Plasma pool of YF pre-vaccinated group. Open circles show results of independent experiments. a RB ELISA. b Den ELISA. c TBE ELISA. d YF ELISA. Error bars represent the SEM calculated from three independent experiments

Fig. 5

NTs of TBE post-vaccination plasma pools at time point 28 weeks before (control) and after depletion of cross-reactive antibodies with RB sE. Blue columns (mean values): Plasma pool of flavivirus-naive group. Red columns (mean values): Plasma pool of YF pre-vaccinated group. Open circles show results of independent experiments. a TBE NT. b YF NT. Error bars represent the SEM calculated from at least three independent experiments. No statistically significant difference was observed before and after depletion (measured by t-test)

Fig. 6

TBE ELISA and NT of individual TBE post-vaccination plasma samples at time point 28 weeks. Blue circles: Plasma samples from flavivirus-naive individuals. Red squares: Plasma samples form YF pre-vaccinated individuals. The values of the symbols represent the means of three to four independent experiments. Solid lines: Means of individual values. Dotted lines: Results of plasma pools. a TBE ELISA. b Fold differences of individual ELISA values to the means of all ELISA titers. c TBE NT. d Fold differences of individual NT titers to the means of all NT titers. Asterisks in a and c indicate significant differences between the two groups (measured by t-test): *P < 0.05; ****P < 0.0001

Fig. 7

Fold differences of TBE ELISA a and TBE NT b to RB ELISA titers of individual TBE post-vaccination sera at time point 28 weeks. Blue circles: Plasma samples from flavivirus-naive individuals. Red squares: Plasma samples form YF pre-vaccinated individuals. The values of the symbols represent the means of three independent experiments. Ratios of TBE ELISA and NT titers to RB titers were calculated and expressed as the fold difference to the respective mean of the two groups

Fig. 8

Correlation of ELISA and NT of TBE post-vaccination plasma samples at time point 28 weeks. Blue lines and circles: Plasma samples from flavivirus-naive individuals. Red lines and squares: Plasma samples from YF pre-vaccinated individuals. The values of the symbols represent the means of three to four independent experiments. a Linear regression of TBE ELISA and TBE NT₅₀ titers. Spearman correlation coefficients (r) are indicated for both groups. b Ratios of TBE NT₅₀ titers and TBE ELISA titers of individual plasma samples of both groups. Solid line: means of all single sera. Asterisks in b indicate significant differences between the two groups (measured by t-test): ***P < 0.001