Association of Premature Immune Aging and Cytomegalovirus After Solid Organ Transplant

Abstract

Immune function is altered with increasing age. Infection with cytomegalovirus (CMV) accelerates age-related immunological changes resulting in expanded oligoclonal memory CD8 T cell populations with impaired proliferation, signaling, and cytokine production. As a consequence, elderly CMV seropositive (CMV+) individuals have increased mortality and impaired responses to other infections in comparison to seronegative (CMV–) individuals of the same age. CMV is also a significant complication after organ transplantation, and recent studies have shown that CMV-associated expansion of memory T cells is accelerated after transplantation. Thus, we investigated whether immune aging is accelerated post-transplant, using a combination of telomere length, flow cytometry phenotyping, and single cell RNA sequencing. Telomere length decreased slightly in the first year after transplantation in a subset of both CMV+ and CMV– recipients with a strong concordance between CD57+ cells and short telomeres. Phenotypically aged cells increased post-transplant specifically in CMV+ recipients, and clonally expanded T cells were enriched for terminally differentiated cells post-transplant. Overall, these findings demonstrate a pattern of accelerated aging of the CD8 T cell compartment in CMV+ transplant recipients.

Functional Changes of T-Cell Subsets with Age and CMV Infection

“…Our results regarding CD57+ T-cells expansion in CMV-seropositive older donors are also of interest in the study of CMV infection in transplant recipients where CMV infection represents a significant complication. CD8+CD57+ TEMRA cells increased over time after transplant specifically in CMV-seropositive but not CMV-seronegative recipients, and changes in CD8+ T-cells compatible with accelerated immune aging have been observed in CMV-seropositive transplant recipients [ 62 ]. Our results showing that CD57+ T-cells are mainly expanded in CMV-seropositive individuals, and maintain cytokine production and polyfunctionality independently of age, suggest that CD57+ T-cells may contribute to the promotion of adverse inflammatory outcomes, such as late graft dysfunction, chronic kidney rejection, cancer, and atherosclerosis observed after kidney transplant associated with CMV infection.…”

CMV-Responsive CD4 T Cells Have a Stable Cytotoxic Phenotype Over the First Year Post-Transplant in Patients Without Evidence of CMV Viremia

“…Recipients of heart or kidney transplant were enrolled pre-transplant or within the first year after transplant at the University of Pennsylvania, Stanford University or the Veterans Administration Palo Alto Health Care System as described ( 25 ). Analysis of CD8 T cells in these cohorts by flow cytometry ( 25 ) and targeted single cell sequencing were previously described in detail ( 26 , 27 ). Induction therapy varied based on transplanted organ and center ( Supplementary Tables 1, 2 ).…”

“…Induction therapy varied based on transplanted organ and center ( Supplementary Tables 1, 2 ). Blood samples were collected as described ( 25 ). Both recipients and organ donors were tested for CMV serostatus pre-transplant.…”

“…Cells were stained as described ( 25 ) using antibodies conjugated to fluorescein, phycoerythrin (PE) or PE conjugates, allophycocyanin (APC) or APC conjugates, Alexa Fluor 700, Brilliant Violet dyes 421, 570, 605, 650, 711, or 785, and Brilliant Ultraviolet dyes 395, 496, and 737. The antibodies were specific for anti-human CD3 (HIT3a), CD4 (S3.5), CD8 (RPA-T8), CD14 (61D3), CD16 (3G8), CD19 (HIB19), CCR7 (G043H7), CD107a (H4A3), CD45RO (UCHL1), CD45RA (HI100), CD57(HNK1), PD-1 (EH12.2H7), T-bet (4B10), interferon (IFN)γ (B27), and tumor necrosis factor (TNF)α (mAb11) and were purchased from BioLegend, eBioscience, BD, Life Technologies, Abcam (Cambridge, UK), or Beckman-Coulter (Pasadena, CA).…”

“…The patients in the study did not have CMV viremia detected during the study course, and therefore represent a population with clinically-controlled CMV. We had previously analyzed CMV-responsive T cells by flow cytometry and by targeted single cell T cell receptor (TCR) and RNA sequencing, and focused on CD8 T cells because we observed greater phenotypic variation in CD8 T cells than CD4 T cells ( 25 , 26 ). However, we did observe variation within the CD4 population as well, and therefore reanalyze the data here to address similar questions for CD4 T cells.…”