High Throughput T Cell Receptor Sequencing Augments Diagnosis and Response Assessment in Patients with Angioimmunoblastic T Cell Lymphoma

Diagnosis and response assessment to therapy has been shown to be challenging in patients with angioimmunoblastic T cell lymphoma (AITL). While at disease onset histology of neoplastic T cell infiltrates in affected lymph nodes and/or bone marrow might be hard to distinguish from reactive lymphproliferation, clonality analyses using T cell receptor (TCR) spectratyping has been helpful in the diagnosis of malignant lymphoma. Nevertheless, resolution of this method is confined to a particular base pair fragment length, which could include several different T cell clones, making detection of minimal residual disease (MRD) almost impossible. From a clinical point of view, rapid responses of AITL to chemotherapy is not uncommon. But as a matter of fact, clinical symptoms of the lymphoma might persist, while neither imaging nor histology is able to detect residual disease.

In an attempt to augment diagnosis of malignancy and improve MRD detection in AILT we established a high throughput TCR profiling approach using next generation sequencing (NGS). In order to determine lymphomaspecific TCR gamma V-J rearrangements, we analysed the entire expressed human TCR gamma repertoire in several different tissues using LymphoTrack TRG assays (Invivoscribe) together with the MiSeq Illumina platform.

In all analysed cases of histologically proven AITL (n=6), TCR profiling resulted in detection of at least one lymphomaspecific clonal V-Jgamma rearranged TCR sequence in all examined relevant tissue probes (lymph nodes, bone marrow, blood) with observed frequencies up to 16% of all reads in lymph nodes and 7% in blood/bone marrow at the time of diagnosis. Lymphomaspecific TCR sequences as revealed by NGS correlated with clonality results as determined from Vgamma fragments analyses by spectratyping. In addition to confirmation of diagnosis, in some cases lymphomaspecific TCR sequences could be detected in lymph node and bone marrow biopsies up to one year before establishment of AITL diagnosis, in which routine pathology examination could only describe an unspecific lymphadenitis. Treatment responses resulted in diminished frequencies of the lymphomaspecific TCR sequences in blood and bone marrow samples with complete disappearance after allogeneic stem cell transplantation. Of particular importance was the observed sustained detection of lymphomaspecific TCR sequences in bone marrow samples in apparently successful treated patients with refractory clinical symptoms, in which lymphoma activity could not firmly be proven by other imaging or pathology methods.

In conclusion, NGS based TCR profiling using V-J gamma rearrangments is very helpful for further analyses of AITL biology and might serve as MRD marker for therapy guidance.