Identification of a core miRNA signature unique to exhausted cytotoxic CD8+ T cells

Abstract

Abstract Cytotoxic CD8+ T lymphocytes (CTLs) play a major role in protection against chronic viral infections and tumors. Chronic antigen stimulation in both conditions leads to CTL exhaustion and failure of CTLs to efficiently eradicate tumors and virally infected cells. miRNAs are small, non-coding RNA molecules that participate in post-transcriptional gene regulation. This study aimed to determine the core miRNA signature of CTL exhaustion in mouse models of both tumors and chronic infection. Exhausted anti-tumor CTLs were isolated from tumors of mice that received 10^6 mouse mesothelioma cells (AE17sOVA) followed by an adoptive transfer of 10^4 CD45.1+ OT-I cells. Effector anti-viral CTLs were isolated from mice adoptively transferred with 10^4 CD45.1+ OT-I cells or P14 cells and infected with WSN-OVA or LCMV Armstrong respectively. For exhausted anti-viral CTLs, mice were adoptively transferred with 10^4 CD45.1+ P14 cells and infected with LCMV-Cl13. Single cell suspensions were prepared from the different tissues, live CTLs were FACS sorted, RNA isolated and small RNA-seq was performed. Principle component analysis (PCA) of miRNA expression revealed that exhausted anti-tumor CTLs and anti-LCMV Cl13 CTLs cluster apart from effector anti-viral CTLs (WSN-OVA and LCMV Armstrong). Differential expression analysis identified 73 miRNAs commonly shared between the exhausted day anti-tumor CTL and anti-viral CTL. Using RNA sequencing of two different models of exhaustion, distinct RNA profiles common in exhausted CTLs were found. This core miRNA signature can now be used to manipulate the expression of specific miRNA to potentially prevent or revert CTL exhaustion and improve the CTL response against tumors and/or chronic infections.