Introduction Post-transplant lymphoproliferative disorder (PTLD) is a potentially fatal complication of organ transplantation commonly associated with Epstein Barr virus (EBV) infection. EBV viral loads are typically monitored by qPCR but EBV viremia does not always portend PTLD, and EBV⁺ PTLD can occur in the absence of increased viral levels. Thus, new biomarkers are critical to improving patient outcomes.

Methods: miRNA-microarray profiling (Taqman-TLDA cards) was used to quantitate expression levels of 639 miRNA in RNA isolated from spontaneously arising EBV⁺ B lymphoma cell lines from patients with PTLD (SLCL) (n=6), B lymphoblastoid cell lines (LCL) generated in vitro with the B95.8 strain of EBV (n=4), and normal human B cells (n=4). One-way ANOVA analysis was used to identify the miRNAs differentially modulated within the groups. Further, real-time qPCR analysis was used to validate the specific differentially expressed miRNAs identified from microarray profiling. Exosomes are nanometric (30-150nm) membrane vesicles that are released by most cell types. Studies have shown that exosomes contain and transfer miRNAs between cells thus allowing for local and distant intercellular communication. Exosomes were isolated from the culture supernatant of SLCL using ExoQuick-TC and centrifugation. RNA was isolated from exosomes and miRNAs quantitated

Results: One hundred and thirty-three (133) miRNAs were significantly modulated by EBV infection in both LCL and SLCL Sixteen miRNAs were uniquely modulated in SLCLs (13 up, 3 down). Real-time qPCR validated a panel of 5 miRNAs (miR-19a, miR-100, miR-106a, miR-422a miR-449b) that were significantly increased in SLCLs as compared to normal EBV⁺ B cells. Exosomes, which were confirmed by transmission electron microscopy, were present in very high levels in SLCL supernatants. Further, SLCL exosomes expressed miRNAs including miR-19a and miR-106a. Interestingly, miR-30c, which was downregulated in SLCLs, was increased in SLCL exosomes.

Conclusion: EBV+ B lymphoma cell lines from PTLD patients produce miRNA-containing exosomes and this may constitute a mechanism of intercellular communication by miRNA transfer to other cells. Importantly, cellular and circulating, cell-free miRNAs have great potential as non-invasive biomarkers of PTLD.

CITATION INFORMATION: Kaul V, Harris-Arnold A, Esquivel C, Martinez O, Krams S. Identification of MicroRNAs in EBV⁺ B Cell Lymphomas and Secreted Exosomes. Am J Transplant. 2016;16 (suppl 3).

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