Preferential Usage of Specific Immunoglobulin Heavy Chain Variable Region Genes with Unmutated Profile and Advanced Stage at Presentation Are Common Features in Patients with Chronic Lymphocytic Leukemia from Senegal

Introduction : Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in Western populations, being rarer in Asian and African people. It has been suggested that patients with CLL from Africa might have a more aggressive disease compared with Causasien patients. In this study, we aimed to identify genetic factors that may account for this difference Methods: We collected peripheral blood mononuclear cells (PBMCs) from a total of 75 patients with CLL, 25 from Senegal (Africa), and 50 from Siena. Since it is well known that there are differences in germline IGH repertoires between different populations, we also collected PBMCs from five healthy Senegalese individuals as control. We analyzed immunoglobulin heavy chain (IGH) genes mutational status by performing next-generation sequencing in these 2 groups of patients. Results: We found that Senegalese patients more frequently had adverse prognostic factors and an unmutated profile. Furthermore, we documented that IGHV1 (IGHV1-69), IGHD3, and IGHJ6 were significantly more frequent in Senegalese patients, whereas IGHV3-30 was common and limited to the Italian cohort. Stereotyped receptors commonly detected in the white population were not recorded in our Senegalese series. Conclusion: The different IGH repertoire we observed in the Senegalese cohort may reflect the diverse genetic and microenvironmental (ie, polymicrobial stimulation) background. Disclosures Gozzetti: Takeda: Honoraria; Amgen: Honoraria; Janssen: Honoraria, Research Funding.

Characterization of Variable Region Genes and Discovery of Key Recognition Sites in the Complementarity Determining Regions of the Anti-Thiacloprid Monoclonal Antibody

Sequence-defined recombinant antibodies (rAbs) have emerged as alternatives to hybridoma-secreted monoclonal antibodies (mAbs) for performing immunoassays. However, the polyploidy nature of hybridomas often leads to the coexistence of aberrant or non-specific functional variable region (VR) gene transcripts, which complicates the identification of correct VR sequences. Herein, we introduced the use of LC-MS/MS combined with next-generation sequencing to characterize VR sequences in an anti-thiacloprid mAb, which was produced by a hybridoma with genetic antibody diversity. The certainty of VR sequences was verified by the functional analysis based on the recombinant antibody (rAb) expressed by HEK293 mammalian cells. The performance of the rAb was similar to that of the parental mAb, with IC50 values of 0.73 and 0.46 μg/L as measured by ELISAs. Moreover, molecular docking analysis revealed that Ser52 (H-CDR2), Trp98, and Trp93 (L-CDR3) residues in the complementarity determining regions (CDRs) of the identified VR sequences predominantly contributed to thiacloprid-specific recognition through hydrogen bonds and the CH–π interaction. Through single-site-directed alanine mutagenesis, we found that Trp98 and Trp93 (L-CDR3) showed high affinity to thiacloprid, while Ser52 (H-CDR2) had an auxiliary effect on the specific binding. This study presents an efficient and reliable way to determine the key recognition sites of hapten-specific mAbs, facilitating the improvement of antibody properties.

David James Kemp 1945–2013

David Kemp's seminal contributions to molecular parasitology of malaria and scabies have placed Australian science at the forefront of research on these important human pathogens. Immunoscreening of expression clones led to the identification of several vaccine candidates against malaria. His contributions to scabies research are pivotal to our understanding of bacteria–parasite–human interactions. Other notable achievements are: the discovery of one of the earliest known multi-gene families; the first cloning of linked variable-region genes in the immunoglobulin heavy-chain locus; the invention of highly cited molecular biology methods, namely Northern blotting and inverted-PCR; and contributions to ‘molecular public health' by his work on various bacterial infections relevant to the health of Indigenous Australians. Kemp's manifest enthusiasm for science was highly infectious. He mentored many high-achieving scientists. In addition to his exemplary career as a scientist, he was a musician at heart and a passionate rock fossicker.