Vitamin D3 replacement enhances antigen-specific immunity in older adults

Abstract

Introduction: Ageing is associated with increased number of infections, decreased vaccine efficacy and increased systemic inflammation termed inflammageing. These changes are reflected by reduced recall responses to varicella zoster virus (VZV) challenge in the skin of older adults. Vitamin D deficiency is more common in the old and has been associated with frailty and increased inflammation. In addition, vitamin D increases immunoregulatory mechanisms and therefore has the potential to inhibit inflammageing.

Objectives: We investigated the use of vitamin D₃ replacement to enhance cutaneous antigen-specific immunity in older adults (≥65 years).

Methods: Vitamin D insufficient older adults (n = 18) were administered 6400IU of vitamin D₃/day orally for 14 weeks. Antigen-specific immunity to VZV was assessed by clinical score assessment of the injection site and transcriptional analysis of skin biopsies collected from challenged injection sites pre- and post-vitamin D₃ replacement.

Results: We showed that older adults had reduced VZV-specific cutaneous immune response and increased non-specific inflammation as compared to young. Increased non-specific inflammation observed in the skin of older adults negatively correlated with vitamin D sufficiency. We showed that vitamin D₃ supplementation significantly increased the response to cutaneous VZV antigen challenge in older adults. This enhancement was associated with a reduction in inflammatory monocyte infiltration with a concomitant enhancement of T cell recruitment to the site of antigen challenge in the skin.

Conclusion: Vitamin D₃ replacement can boost antigen-specific immunity in older adults with sub-optimal vitamin D status.

Keywords: ageing; skin; varicella zoster virus; vitamin D.

Graphical Abstract

Figure 1.

Decreased cutaneous immunity with age correlates with vitamin D insufficiency. (A) study schematic, young (white) and old (grey) individuals were injected with either antigen or saline and biopsies were collected at specified time points and RNAseq or microarray analysis was performed. Samples were compared to normal [unmanipulated; - (young n = 5 and old n = 32)] skin. (B) Antigen-specific gene module was generated and (C) T cell-specific gene module in VZV-injected skin (72 hours post-injection; young n = 6 and young n = 9). (D) saline-specific gene module and (E) monocyte-specific gene module in saline injected skin (6 hours post-injection; young n = 9 and old n = 37). (F) Monocyte-specific gene module in VZV injected skin (6 hours post-injection; young n = 6 and young n = 9). (G) Saline-specific module and (H) monocyte-specific module in saline-injected skin from old donors was correlated with serum 25(OH)D concentrations (nmol/l). B–F were analysed with an unpaired t test and G and H were analysed by a Pearson correlation test. **P < 0.01; ***P < 0.001; ****P < 0.0001.

Figure 2.

Vitamin D₃ supplementation significantly improves VZV-specific cutaneous immunity. (A) Clinical study schematic. (B) Serum 25(OH)D concentrations and C and D, VZV clinical scores in older adults pre- and post-supplementation (n = 18). B and C were analysed with a paired t test. ***P < 0.001; ****P < 0.0001.

Figure 3.

Vitamin D₃ supplementation is associated with reduced inflammatory monocyte recruitment in response to saline. (A) RNAseq analysis of 3 mm biopsies collected from normal and saline-injected skin (6 hours post-injection) pre- and post-vitamin D₃ supplementation. The top 30 genes upregulated in saline-injected skin as compared to normal skin before pre-Vitamin D₃ and (B) dot plots of top eight upregulated saline-associated genes pre-vitamin D₃. (C) Saline-specific module and (D) monocyte-specific module in saline-injected skin pre- and post-vitamin D₃ supplementation (n = 17). B, analysed by C and D, analysed with a Wilcoxon-matched paired test. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.

Figure 4.

Vitamin D₃ supplementation increases the accumulation of T cells at the site of VZV challenge. (A) RNAseq analysis of 3 mm biopsies collected from normal and VZV-injected skin (48 hours post-injection) pre- and post-vitamin D. The top 30 genes upregulated in VZV injected skin as compared to normal skin before post-Vitamin D₃ (n = 16). (B) VZV-specific module and (C) T cell specific module in VZV-injected skin pre- and post-vitamin D₃ supplementation separated based upon improvement in VZV score change of <2 (white; n = 9) and change ≥2 (red; n = 7). Paired data were analysed using a Wilcoxon-matched paired test and unpaired data with Mann–Whitney test. *P < 0.05; **P < 0.01.