Persistent High Frequencies of Varicella-Zoster Virus ORF4 Protein-Specific CD4⁺T Cells after Primary Infection

Abstract

Open reading frame 4 (ORF4) of varicella-zoster virus (VZV) encodes an immediate-early protein that is believed to be important for viral infectivity and establishing latency. Evidence suggests that VZV-specific T cells are crucial in the control of viral replication, but there are no data addressing the existence of potential ORF4 protein-specific CD4؉ T cells. We tested the hypothesis that VZV ORF4 protein-specific CD4 ؉ T cells could be identified and characterized within the peripheral blood of healthy immune donors following primary infection. Gamma interferon (IFN-␥) immunosorbent assays were used to screen peripheral blood mononuclear cells obtained from healthy seropositive donors for responses to overlapping ORF4 peptides, viral lysate, and live vaccine. High frequencies of ORF4 protein-specific T cells were detected ex vivo in individuals up to 52 years after primary infection. Several immunogenic regions of the ORF4 protein were identified, including a commonly recognized epitope which was restricted through HLA-DRB1*07. Total ORF4 protein-specific responses comprised 19.7% and 20.7% of the total lysate and vaccine responses, respectively, and were dominated by CD4 ؉ T cells. Indeed, CD4 ؉ T cells were found to dominate the overall virus-specific IFN-␥ cellular immune response both ex vivo and after expansion in vitro. In summary, we have identified an ORF4 protein as a novel target antigen for persistent VZV-specific CD4 ؉ T cells, with implications for disease pathogenesis and future vaccine development.

Genome-Wide Analysis of T Cell Responses during Acute and Latent Simian Varicella Virus Infections in Rhesus Macaques

“…Consequently, our understanding of the global anti-VZV T cell response remains incomplete. This is illustrated by the fact that one study concluded that the CD4 T cell response to VZV is directed primarily against ORF4 (19), while a follow-up study suggested that the anti-VZV response is primarily mediated by CD4 T cells directed against ORF67 (20). We have recently shown that intrabronchial infection of young rhesus macaques (RM) with simian varicella virus (SVV) results in disease characteristic of VZV infection in humans, with the appearance of a generalized varicella rash at 7 days postinfection (dpi), generation of T and B cell responses that peak at 7 to 14 days postinfection, resolution of viremia coincident with abatement of varicella at 21 to 35 days postinfection, and establishment of latency with limited transcriptional activity in the sensory ganglia (22,23).…”

“…More recent studies also using T cell lines suggest that the anti-ORF4, -63, -67, and -68 responses are predominated by CD4 T cells (1,(19)(20)(21). However, to date, a comprehensive ex vivo analysis of the T cell response to the entire VZV genome has not been conducted.…”

IE63-specific T-cell responses associate with control of subclinical varicella zoster virus reactivation in individuals with malignancies

“…VZV glycoproteins I and E, immediate-early protein 63 (IE63) and four specific CD4 þ T cells have been shown to circulate at persistently high frequencies in the peripheral blood of healthy seropositive donors without a history of reactivation (Jones et al, 2006Malavige et al, 2007Malavige et al, , 2008a. However, VZV-specific T-cell responses have been shown to be lower in elderly individuals and in patients with disease such as systemic lupus erythematosus (Miller, 1980;Levin et al, 2003;Park et al, 2004).…”

“…However, apart from clinically apparent VZV reactivation, subclinical reactivation has also been reported in both immunocompetent and immunosuppressed individuals (Schunemann et al, 1998;Quinlivan et al, 2007). Although the mechanisms underlying such reactivation are unclear, it is thought that cell-mediated immune responses are vital in controlling VZV replication (Malavige et al, , 2008b.VZV glycoproteins I and E, immediate-early protein 63 (IE63) and four specific CD4 þ T cells have been shown to circulate at persistently high frequencies in the peripheral blood of healthy seropositive donors without a history of reactivation (Jones et al, 2006Malavige et al, 2007Malavige et al, , 2008a. However, VZV-specific T-cell responses have been shown to be lower in elderly individuals and in patients with disease such as systemic lupus erythematosus (Miller, 1980;Levin et al, 2003;Park et al, 2004).…”

Identification of Varicella-Zoster Virus-Specific CD8 T Cells in Patients after T-Cell-Depleted Allogeneic Stem Cell Transplantation

“…Previous research has demonstrated that IE62-specific T cells were detected after primary VZV infection and in immune subjects (2,4). In addition, T cells recognizing various other IE proteins and glycoproteins of VZV, as demonstrated by gamma interferon (IFN-␥) production upon stimulation with peptides or lysate derived from these proteins, have been described (1,6,13). The VZVspecific memory T cells found in these studies were predominantly CD4 T cells, while no VZV-specific CD8 T cells were demonstrated without prior in vitro expansion, possibly due to the low frequency of VZV-specific CD8 T cells or to the low sensitivity of the screening methods used to detect CD8 T cells by IFN-␥ production upon stimulation.…”