Immunoglobulin Somatic Hypermutation by Next Generation Sequencing (Blood)

CLL is one of the most commonly diagnosed hematologic malignancies in the U.S. It primarily affects elderly individuals, although ~30% of patients are under age 60. The clinical course of CLL is variable, with a very indolent course in many patients to more progressive forms that may eventually transform into high grade lymphomas. The ability to identify high-risk patients is an important goal in care of CLL patients as these patients are eligible for more intensive therapy protocols aimed at prolonging survival. IGH Vh mutation status has been shown to be an important prognostic factor for CLL patients. Lack of somatic mutation (>98% homology to germ line) in the Vh gene is associated with a comparatively poor prognosis, whereas >2% mutation rate is associated with a better prognosis. Clinical correlation of IGH Vh mutation status with other prognostic factors such as clinical staging (i.e. Rai and Binet staging), cytogenetic changes (e.g. 11q-, 17p- and trisomy 12), immunohistochemistry (e.g. ZAP-70, CD49d, or CD38 expression), laboratory findings (e.g. beta-2-microglobulin), and other gene mutations (e.g. TP53) is important for predicting disease risk and response to treatment.

The LymphoTrack® (InVivoScribe Technologies) IGHV Leader Somatic Hypermutation Assay for Illumina® MiSeq® is a next generation sequencing (NGS)-based assay targeting the Leader (VHL) -J (JH1, JH2, JH3, JH4, JH5, and JH6) regions of the immunoglobulin heavy chain (IGH) gene locus using both genomic DNA and RNA (reverse transcribed into cDNA) as starting genetic material. The somatic hypermutation status of clonal populations is determined by the number of mismatches identified in the encompassed VH region when compared to the germline reference sequence.