Human Cytomegalovirus (HCMV)-Specific CD4 ⁺ T Cells Are Polyfunctional and Can Respond to HCMV-Infected Dendritic Cells In Vitro

Abstract

Human cytomegalovirus (HCMV) infection and periodic reactivation are generally well controlled by the HCMV-specific T cell response in healthy people. While the CD8 ϩ T cell response to HCMV has been extensively studied, the HCMVspecific CD4 ϩ T cell effector response is not as well understood, especially in the context of direct interactions with HCMV-infected cells. We screened the gamma interferon (IFN-␥) and interleukin-10 (IL-10) responses to 6 HCMV peptide pools (pp65, pp71, IE1, IE2, gB, and US3, selected because they were the peptides most frequently responded to in our previous studies) in 84 donors aged 23 to 74 years. The HCMV-specific CD4 ϩ T cell response to pp65, IE1, IE2, and gB was predominantly Th1 biased, with neither the loss nor the accumulation of these responses occurring with increasing age. A larger proportion of donors produced an IL-10 response to pp71 and US3, but the IFN-␥ response was still dominant. CD4 ϩ T cells specific to the HCMV proteins studied were predominantly effector memory cells and produced both cytotoxic (CD107a expression) and cytokine (macrophage inflammatory protein 1␤ secretion) effector responses. Importantly, when we measured the CD4 ϩ T cell response to cytomegalovirus (CMV)-infected dendritic cells in vitro, we observed that the CD4 ϩ T cells produced a range of cytotoxic and secretory effector functions, despite the presence of CMV-encoded immune evasion molecules. CD4 ϩ T cell responses to HCMV-infected dendritic cells were sufficient to control the dissemination of virus in an in vitro assay. Together, the results show that HCMV-specific CD4 ϩ T cell responses, even those from elderly individuals, are highly functional and are directly antiviral.IMPORTANCE Human cytomegalovirus (HCMV) infection is carried for a lifetime and in healthy people is kept under control by the immune system. HCMV has evolved many mechanisms to evade the immune response, possibly explaining why the virus is never eliminated during the host's lifetime. The dysfunction of immune cells associated with the long-term carriage of HCMV has been linked with poor responses to new pathogens and vaccines when people are older. In this study, we investigated the response of a subset of immune cells (CD4 ϩ T cells) to HCMV proteins in healthy donors of all ages, and we demonstrate that the functionality of CD4 ϩ T cells is maintained. We also show that CD4 ϩ T cells produce effector functions in response to HCMV-infected cells and can prevent virus spread. Our work demonstrates that these HCMV-specific immune cells retain many important functions and help to prevent deleterious HCMV disease in healthy older people.

Latent Cytomegalovirus (CMV) Infection Does Not Detrimentally Alter T Cell Responses in the Healthy Old, But Increased Latent CMV Carriage Is Related to Expanded CMV-Specific T Cells

“…We also wanted to measure the range of T cell responses in a large donor cohort to a number of viral proteins expressed during lytic infection; we have previously identified both CD4 + and CD8 + T cells producing IFNγ from many donors to six HCMV lytic proteins pp65, IE1, IE2, gB, pp71, and US3 (57, 63). Using FluoroSpot methodology, we were able to measure CD8 + T cell IFNγ responses and both IFNγ and IL-10 CD4 + T cell responses to overlapping peptide pools of these 11 HCMV proteins.…”

The self‐curing phenomenon of schistosome infection in rhesus macaques: insight from in vitro studies

“…These findings suggest that multifunctional cellular immune responses might be involved in the self‐cure process. Several studies have demonstrated the protective roles of host polyfunctional cells against numerous infectious organisms . For example, the frequency of Plasmodium falciparium ‐specific polyfunctional T cells has been associated with protection in humans .…”

CMV immune evasion and manipulation of the immune system with aging

“…The production of cellular IL-10 in response to HCMV antigenic stimulation by CD4+ T cells has been observed in multiple studies (Clement et al 2016; Jackson et al 2017a; Mason et al 2013; Schwele et al 2012). Production of IL-10 is a characteristic feature of regulatory T cells (Tregs) (Zhu et al 2010).…”

“…In order to address this problem, we have developed a viral dissemination assay which we have used to interrogate the capacity of HCMV-specific CD8+ (Jackson et al 2014) and CD4+ T cells (Jackson et al 2017a) to control the spread of HCMV in vitro. We have demonstrated that purified CD8+ and CD4+ T cell populations when isolated directly ex vivo are able to prevent the spread of the a GFP-tagged clinical CMV isolate.…”