Reduced expression of the lncRNA NRON is a potential hallmark of the CMV-amplified CD8+ T cell accumulations commonly seen in older humans

Abstract

The characteristic accumulation of late-stage differentiated CD8+ T cells is enhanced by lifelong latent cytomegalovirus (CMV) persistence, which makes it challenging to screen for subclinical biomarkers of immune aging in the elderly. We systematically identified predominantly preformed, long, noncoding RNAs (lncRNAs) as integrative biomarkers of CD8⁺ T cell aging in 14 elderly CMV carriers over 80 years of age. After sorting the CD28^nullCD8⁺ T cell subset and its CD28^bearingCD8⁺ counterpart in five nonagenarians, we profiled the differential expression of lncRNAs and genes in CD28^nullCD8⁺ T cells via array detection. We focused on 11 differentially expressed antisense lncRNAs and cross-referenced them with previously identified age-accumulated lncRNAs to create a set of candidates in CD28^nullCD8⁺T cells. We performed intracellular validation on the age-accumulated candidate lncRNAs paired with their antisense target genes using quantitative polymerase chain reaction (qPCR). Simultaneously, we sorted the CMV_pp65-specific CD8⁺ T cell subset and its counterpart from participant cells with the HLA-A-*0201 genotype. The validated age-accumulated lncRNAs in CD28^nullCD8⁺ T cells were intracellularly cross-validated in CMV_pp65CD8⁺ T cells. Finally, we identified the immunity-related gene(s) that acted as potential target(s) to the cross-validated age-accumulated lncRNA(s), using bioinformatics techniques. The potential regulation of the final identified lncRNA-gene pair(s) was simultaneously predicted in two pathway-integrated networks. We concluded that expression of an age-accumulated lncRNA (NRON) was decreased, whereas that of its immunity-related target gene (NFAT) was increased, in both CD28^nullCD8⁺ T cells and CMV_pp65CD8⁺ T cells of elderly individuals with persistent CMV infection. The identification of NRON as a potential biomarker suggests that NRON contributes to CMV-enhanced CD28^nullCD8⁺ T cell aging by modulating phosphorylation and/or IL-4-dependent NFAT signaling.

Keywords: Bioinformatics; Biomarkers; CMV persistence; Immune aging; T cell.