ABSTRACT
Leukopenia is a common manifestation of many diseases, including global outbreak SAS-CoV-2 infection. Granulocyte-macrophage colony-stimulating factor (GM -CSF) has been proved to be effective in promoting lymphocyte regeneration, but adverse immunological effects have also emerged. This study aim to investigate the effect of GM -CSF on BCR heavy chain CDR3 repertoire while promoting lymphocyte regeneration. Cyclophosphamide (CTX) and GM -CSF were used to inhibit and stimulate bone marrow hematopoiesis, respectively. High throughput sequencing was applied to detect the characteristics of BCR CDR3 repertoire in controls, CTX group and GM -CSF group. The white blood cells (WBCs) were quickly reduced (P < 0.05) with lymphocytes decreasing causing by CTX, and the WBCs and lymphocytes returned to the level of controls after GM -CSF treatment. The diversity of BCR heavy chain CDR3 repertoire was also significantly decreased in CTX group. Although there is still a big gap from the controls, the diversity was picked up after GM -CSF treatment. The expression of IGHD01-01, IGHD02-14 and IGHJ04-01 with high-frequency usage regularly and significantly changed in three groups, and many genes with low-frequency usage lost in CTX group and did not reappear in GM -CSF group. Moreover, two shared sequences and accounted for the highest proportion in GM -CSF group have been detected in animal model of chronic lymphocytic leukemia. These results revealed that GM -CSF can partially restore changes in the BCR heavy chain CDR3 repertoire while promoting lymphocyte regeneration, but it may also lead to rearrangement, proliferation and activation of abnormal B cells, which can provide a basis for further study on the adverse immunological effects and mechanism of GM -CSF treatment.
Subject(s)
Cyclophosphamide/adverse effects , Granulocyte-Macrophage Colony-Stimulating Factor/immunology , Leukopenia/immunology , Lymphocytes/drug effects , Lymphocytes/immunology , Receptors, Antigen, B-Cell/drug effects , Receptors, Antigen, B-Cell/metabolism , Animals , Complementarity Determining Regions/drug effects , Complementarity Determining Regions/genetics , Complementarity Determining Regions/metabolism , Cyclophosphamide/therapeutic use , Female , Granulocyte-Macrophage Colony-Stimulating Factor/therapeutic use , Immunoglobulin Heavy Chains/drug effects , Immunoglobulin Heavy Chains/genetics , Immunoglobulin Heavy Chains/metabolism , Immunoglobulin Joining Region/drug effects , Immunoglobulin Joining Region/metabolism , Immunoglobulin Variable Region/drug effects , Immunoglobulin Variable Region/metabolism , Leukocytes/drug effects , Leukopenia/chemically induced , Leukopenia/drug therapy , Lymphocytes/metabolism , Mice, Inbred BALB C , Receptors, Antigen, B-Cell/immunologyABSTRACT
Since the COVID-19 pandemic onset, the antibody response to SARS-CoV-2 has been extensively characterized. Antibodies to the receptor binding domain (RBD) on the spike protein are frequently encoded by IGHV3-53/3-66 with a short complementarity-determining region (CDR) H3. Germline-encoded sequence motifs in heavy chain CDRs H1 and H2 have a major function, but whether any common motifs are present in CDR H3, which is often critical for binding specificity, is not clear. Here, we identify two public clonotypes of IGHV3-53/3-66 RBD antibodies with a 9-residue CDR H3 that pair with different light chains. Distinct sequence motifs on CDR H3 are present in the two public clonotypes that seem to be related to differential light chain pairing. Additionally, we show that Y58F is a common somatic hypermutation that results in increased binding affinity of IGHV3-53/3-66 RBD antibodies with a short CDR H3. These results advance understanding of the antibody response to SARS-CoV-2.