Evaluation of VZV-specific Cell-mediated Immunity by Interferon-gamma ELISA in Adults ≥50 Years of Age Administered a Herpes Zoster Vaccine.

Varicella-zoster virus (VZV)-specific cell-mediated immunity (CMI) is critical for preventing and controlling the onset of herpes zoster (HZ). To assess VZV CMI, an interferon-gamma (IFN-γ) enzyme-linked immunosorbent assay (ELISA) was validated by examining the influence of VZV-specific antigen content, incubation time, and interval from whole blood collection on the assay. In the phase II clinical trial, VZV-specific CMI in adults ≥50 years of age administered an HZ vaccine were evaluated by IFN-γ ELISA, as determined by measuring IFN-γ production in the whole blood in response to stimulation with ultraviolet light-inactivated VZV. The VZV-specific IFN-γ levels varied among individuals from pre-vaccination (baseline) to 6 weeks post-vaccination. In most subjects, VZV-specific CMI was increased at 6 weeks post-vaccination. The HZ vaccine elicited a significant increase in the VZV-specific CMI response as measured by ELISA; the geometric mean fold-rises (GMFRs) from baseline to 6 weeks post-vaccination were 3.50, 4.22, and 5.24 in the 4.3, 4.7, and 4.9 log PFU vaccine groups, respectively, which was significantly higher than in the placebo group (P<0.05). These results indicate that vaccination enhances the VZV-specific CMI responses in subjects; IFN-γ ELISA is an effective method for evaluating the CMI response and may be useful for identifying individuals at a high risk of HZ infection. This article is protected by copyright. All rights reserved.