Frequencies of Memory T Cells Specific for Varicella?Zoster Virus, Herpes Simplex Virus, and Cytomegalovirus by Intracellular Detection of Cytokine Expression

Abstract

Memory T cells specific for varicella-zoster virus (VZV), herpes simplex virus (HSV), and human cytomegalovirus (HCMV) were compared in immune adults by intracellular cytokine (ICC) detection. The mean percentages of CD4⁺ T cells were 0.11% for VZV and 0.22% for HSV by interferon (IFN)-γ production; the frequency for HCMV was significantly higher at 1.21%. Percentages of VZV-, HSV-, and HCMV-specific CD4⁺ T cells were similar by use of tumor necrosis factor (TNF)-α. HCMV-stimulated CD8⁺ T cells produced IFN-γ (1.11%) and TNF-α (1.71%); VZV- and HSV-specific CD8⁺ T cells were not detectable. VZV CD4⁺ T cell numbers were similar in young adults with natural or vaccine-induced immunity. VZV CD4⁺ T cells were significantly less frequent in older adults. Secondary varicella immunization did not increase VZV-specific CD4⁺ T cell frequencies by ICC assay. Numbers of memory T cells specific for herpesviruses may vary with sites of viral latency and with host age.