Characterization of neutralizing versus binding antibody and T cell responses to varicella-zoster virus in the elderly

Abstract

Age-related immune changes increase the risk of herpes zoster (HZ) caused by varicella-zoster virus (VZV) reactivation. Understanding immune responses to VZV is crucial for reducing the burden of HZ in aging populations. Due to the limited availability of data regarding the VZV immune profiles of elderly individuals, particularly in developing countries, more comprehensive immunological investigations are warranted. A total of 213 participants aged ≥ 60 years were included in this study. VZV-neutralizing antibodies (NAb) and glycoprotein-binding antibodies (BAb) were quantified. Furthermore, VZV-specific T cell subsets and their functionality were evaluated using flow cytometry. Elderly individuals demonstrated a high VZV seropositivity rate of 98.6%, exceeding that of the younger adults. Interestingly, VZV-BAb increased, whereas the proportion of NAb decreased with age, with a significantly lower proportion in the elderly aged ≥ 70 years. The elderly showed decreased naïve T cells and accumulated VZV-specific aged T cells; central memory and effector memory CD4⁺ and CD8⁺ T cells, and terminal effector memory CD8⁺ T cells; with elevated expression of senescence and exhaustion markers, indicating functional impairment. Nonetheless, VZV-specific functional T cells; percentages of VZV-specific interferon-γ-secreting CD4⁺ and CD8⁺ T cells; were not diminished. These findings provide insights into aging VZV immune profiles, which will facilitate the development of age-specific HZ vaccination policies.

Keywords: Aging; Immunosenescence; Shingles; Varicella-zoster virus.

Fig. 1

Age-dependency of VZV-specific BAb and NAb titers in the elderly. Correlation plots between age, gender, and gp IgG ELISA (A), gH/gL IgG ELISA (B), live virus MNT (C), ratio of gp IgG ELISA to live virus MNT (D), and ratio of gH/gL IgG ELISA to live virus MNT (E). Each open circle and solid triangle represent the serological results of individual elderly male and female participants, respectively. Solid and dashed lines with gray areas indicate linear regression lines with 95% confidence intervals for male and female data. Pearson’s correlation coefficient (r) was used to test for correlations. Bold r and p-values indicate a significant correlation (p < 0.05). Ratio of gH/gL IgG ELISA to live virus MNT in the different age groups (F). Each dot represents an individual subject and the horizontal lines indicate the medians. P-values were determined using the Kruskal-Wallis test with Dunn’s multiple comparisons. *p < 0.05 and **p < 0.01. gp glycoproteins, gH/gL, glycoprotein H/glycoprotein L complex, ID₅₀ 50% inhibitory dilution, mIU milli-international unit.

Fig. 2

Percentage of T cell population after stimulation with VZV gE and CMV pp65 peptides. Gating strategy with representative flow cytometry plots identifying subpopulations of CD4⁺ and CD8⁺ T cells (A). VZV-specific CD4⁺ (B) and CD8⁺ (C) T cell subpopulations. CMV-specific CD4⁺ (D) and CD8⁺ (E) T cell subpopulations. The fractions of the total CD4⁺ and CD8⁺ T cell differentiation subpopulations are depicted in the graphs. The different percentages of specific subsets across all elderly groups (≥ 60 years, N = 121) compared to the adult group (< 60 years, N = 31) under each condition are shown in Supplementary Fig. S2 and S3. P-values were determined using the Kruskal–Wallis test with Dunn’s multiple comparisons. Abbreviations: T_CM, central memory; T_EM, effector memory; T_EMRA, terminal effector memory T cells.

Fig. 3

VZV- and CMV-specific responses in participants with simulated IFN-γ-secreting T cells. Gating strategy with representative flow cytometry plots identifying CD4⁺ and CD8⁺ T cells secreting IFN-γ (A). Percentages of CD4⁺ (left) and CD8⁺ (right) T cells secreting IFN-γ in VZV-stimulated individuals (B) and CMV-stimulated individuals (C). Each dot represents a single donor subtracted from the negative control (< 60 years, N = 31; 60–69 years, N = 65; 70–79 years, N = 40; ≥ 80 years, N = 16), and the horizontal lines indicate the medians. P-values were determined using the Kruskal-Wallis test with Dunn’s multiple comparisons. **p < 0.01, ***p < 0.001, and ****p < 0.0001.

Fig. 4

Correlation between VZV-specific HIR and CMIR in the elderly and adults. Correlation plots between gp IgG ELISA and gH/gL IgG ELISA (A), gp IgG ELISA and live virus MNT (B), gH/gL IgG ELISA and live virus MNT (C), percentage of IFN-γ-secreting cells and gp IgG ELISA (D), percentage of IFN-γ-secreting cells and gH/gL IgG ELISA (E), percentage of IFN-γ-secreting cells and live virus MNT (F), percentage of IFN-γ-secreting cells and ratio of gp IgG ELISA to live virus MNT (G), and percentage of IFN-γ-secreting cells and ratio of gH/gL IgG ELISA to live virus MNT (H). Each dot represents the immunological results of the individual elderly and adult participants. Straight lines with gray areas indicate linear regression lines with 95% confidence intervals. Pearson’s correlation coefficient (r) was used to test for correlations. Bold r and p-values indicate a significant correlation (p < 0.05). gp glycoproteins, gH/gL glycoprotein H/glycoprotein L complex, ID₅₀ 50% inhibitory dilution, mIU milli-international unit.

Fig. 5

Correlation between VZV- and CMV-specific antibodies in the elderly and adults. Correlation plots of CMV IgG ELISA and VZV gp IgG ELISA (A), VZV gH/gL IgG ELISA (B), and VZV live virus MNT (C). Each dot represents the immunological results of the individual elderly and adult participants. Straight lines with gray areas indicate linear regression lines with 95% data confidence intervals. Pearson’s correlation coefficient (r) was used to test for correlations. Bold r and p-values indicate a significant correlation (p < 0.05). gp glycoproteins, gH/gL glycoprotein H/glycoprotein L complex, ID₅₀ 50% inhibitory dilution, mIU milli-international unit, PEI-U Paul Ehrlich Institute unit.