Sequencing the B Cell Receptor Repertoires of Antibody-Deficient Individuals With and Without Infection Susceptibility

PURPOSE

Most individuals with antibody deficiency (hypogammaglobulinemia) need immunoglobulin replacement therapy (IgG-RT) from healthy plasma donors to stay clear of infections. However, a small subset of hypogammaglobulinemic patients do not require this substitution therapy. We set out to investigate this clinical conundrum by asking whether the peripheral B cell receptor repertoires differ between antibody-deficient patients who do and do not need IgG-RT.

METHODS

We sequenced and analyzed IgG and IgM heavy chain B cell receptor repertoires from peripheral blood mononuclear cells (PBMCs) isolated from patients with low serum IgG concentrations who did or did not require IgG-RT.

RESULTS

Compared to the patients who did not need IgG-RT, those who needed IgG-RT had higher numbers of IgG antibody clones, higher IgM diversity, and less oligoclonal IgG and IgM repertoires. The patient cohorts had different heavy chain variable gene usage, and the patients who needed IgG-RT had elevated frequencies of IgG clones with higher germline identity (i.e., fewer somatic hypermutations).

CONCLUSION

Antibody-deficient patients with infection susceptibility who needed IgG-RT had more diverse peripheral antibody repertoires that were less diverged from germline and thus may not be as optimal for targeting pathogens, possibly contributing to infection susceptibility.

Class II human leucocyte antigen DRB1*11 in hairy cell leukaemia patients with and without haemolytic uraemic syndrome

Frequencies of human leucocyte antigens (HLA) were determined in 287 classic hairy cell leukaemia (HCL) patients. With respect to both population (n = 287) and allele (2n = 574) frequency respectively, the most common HLA class I and II antigens expressed were HLA-A*02 (49·1% and 28·6%), HLA-B*07 (21·3% and 11·1%), HLA-C*07 (46·7 and 28·2%), HLA-DQB1*03 (62·7% and 37·3%), HLA-DRB1*11 (30·0% and 16·0%) and HLA-DRB4*01 (45·3% and 29·6%). In comparing 6-14 databases of control Caucasians to 267 Caucasian HCL patients, only HLA-DRB1*11 was consistently over-represented in HCL, 31·1% of patients vs. 17-19·9% of controls (P = 0·0055 to <0·0001) and 16·5% of alleles vs. 6·5-12·3% of control alleles (P = 0·022 to <0·0001). HLA-DRB1*11 is a known risk factor for acquired thrombotic microangiopathy. Anti-CD22 recombinant immunotoxin BL22 in HCL was associated with a 12% incidence of completely reversible grade 3-4 haemolytic uraemic syndrome (HUS), mainly during the second or third retreatment cycle. Of 49 HCL patients receiving ≥2 cycles of BL22, 7 (14%) had HUS and HLA-DRB1*11 was expressed in 71% of 7 with HUS compared with only 21% of 42 without (P = 0·015). These data suggest that DBR1*11 may be a marker for increased susceptibility to HCL and, among HCL patients, could be a risk factor for BL22-induced HUS.

Molecular characterization of immunoglobulin gene rearrangements in diffuse large B-cell lymphoma: antigen-driven origin and IGHV4-34 as a particular subgroup of the non-GCB subtype

The pathogenesis of diffuse large B-cell lymphoma (DLBCL) remains partially unknown. The analysis of the B-cell receptor of the malignant cells could contribute to a better understanding of the DLBCL biology. We studied the molecular features of the immunoglobulin heavy chain (IGH) rearrangements in 165 patients diagnosed with DLBCL not otherwise specified. Clonal IGH rearrangements were amplified according to the BIOMED-2 protocol and PCR products were sequenced directly. We also analyzed the criteria for stereotyped patterns in all complete IGHV-IGHD-IGHJ (V-D-J) sequences. Complete V-D-J rearrangements were identified in 130 of 165 patients. Most cases (89%) were highly mutated, but 12 sequences were truly unmutated or minimally mutated. Three genes, IGHV4-34, IGHV3-23, and IGHV4-39, accounted for one third of the whole cohort, including an overrepresentation of IGHV4-34 (15.5% overall). Interestingly, all IGHV4-34 rearrangements and all unmutated sequences belonged to the nongerminal center B-cell-like (non-GCB) subtype. Overall, we found three cases following the current criteria for stereotyped heavy chain VH CDR3 sequences, two of them belonging to subsets previously described in CLL. IGHV gene repertoire is remarkably biased, implying an antigen-driven origin in DLBCL. The particular features in the sequence of the immunoglobulins suggest the existence of particular subgroups within the non-GCB subtype.

Partial versus productive immunoglobulin heavy locus rearrangements in chronic lymphocytic leukemia: implications for B-cell receptor stereotypy

The frequent occurrence of stereotyped heavy complementarity-determining region 3 (VH CDR3) sequences among unrelated cases with chronic lymphocytic leukemia (CLL) is widely taken as evidence for antigen selection. Stereotyped VH CDR3 sequences are often defined by the selective association of certain immunoglobulin heavy diversity (IGHD) genes in specific reading frames with certain immunoglobulin heavy joining (IGHJ ) genes. To gain insight into the mechanisms underlying VH CDR3 restrictions and also determine the developmental stage when restrictions in VH CDR3 are imposed, we analyzed partial IGHD-IGHJ rearrangements (D-J) in 829 CLL cases and compared the productively rearranged D-J joints (that is, in-frame junctions without junctional stop codons) to (a) the productive immunoglobulin heavy variable (IGHV )-IGHD-IGHJ rearrangements (V-D-J) from the same cases and (b) 174 D-J rearrangements from 160 precursor B-cell acute lymphoblastic leukemia cases (pre-B acute lymphoblastic leukemia [ALL]). Partial D-J rearrangements were detected in 272/829 CLL cases (32.8%). Sequence analysis was feasible in 238 of 272 D-J rearrangements; 198 of 238 (83.2%) were productively rearranged. The D-J joints in CLL did not differ significantly from those in pre-B ALL, except for higher frequency of the IGHD7-27 and IGHJ6 genes in the latter. Among CLL carrying productively rearranged D-J, comparison of the IGHD gene repertoire in productive V-D-J versus D-J revealed the following: (a) overuse of IGHD reading frames encoding hydrophilic peptides among V-D-J and (b) selection of the IGHD3-3 and IGHD6-19 genes in V-D-J junctions. These results document that the IGHD and IGHJ gene biases in the CLL expressed VH CDR3 repertoire are not stochastic but are directed by selection operating at the immunoglobulin protein level.

Molecular variant of hairy cell leukemia with poor prognosis

Hairy cell leukemia variant (HCLv), described 30 years ago, was reported to present with high disease burden and less often leukopenia, and later was reported to be resistant to purine analogs. Patients with HCLv were overrepresented among patients with HCL seeking relapsed/refractory trials. To compare clinical and molecular features of classic HCL (HCLc) and HCLv, 85 rearrangements expressing immunoglobulin variable heavy chain were sequenced, taken from 20 patients with HCLv and 62 with HCLc. The gene VH4-34, commonly used in autoimmune disorders, was found in eight patients (40%) with HCLv versus six (10%) with HCLc (p = 0.004). Ninety-three percent of the VH4-34 rearrangements were unmutated, defined as >98% homologous to the germline sequence. Clinical features of VH4-34+ patients that were similar to those with HCLv included higher white blood cell counts at diagnosis (p = 0.002) and lower response (p = 0.00001) and progression-free survival (p = 0.007) after first-line cladribine, and shorter overall survival from diagnosis (p < 0.0001). It was found that VH4-34 was independent from HCLv and a stronger predictor than HCLv in associating with poor prognosis. We conclude that VH4-34+ hairy cell leukemia, which only partly overlaps with HCLv, is associated with poor prognosis after single-agent cladribine. However, cases are observed which respond well to antibody therapy either alone or in combination with purine analog.

Evidence of canonical somatic hypermutation in hairy cell leukemia

To compare hairy cell leukemia (HCL) with chronic lymphocytic leukemia (CLL) and normal B cells with respect to their B-cell receptors, somatic hypermutation (SHM) features in HCL were examined in a series of 130 immunoglobulin gene heavy chain rearrangements, including 102 from 100 classic (HCLc) and 28 from 26 variant (HCLv) patients. The frequency of unmutated rearrangements in HCLc was much lower than that in HCLv (17% vs 54%, P < .001) or historically in CLL (17% vs 46%, P < .001), but HCLv and CLL were similar (P = .45). As previously reported for CLL, evidence of canonical SHM was observed in HCLc rearrangements, including: (1) a higher ratio of replacement to silent mutations in the complementarity determining regions than in the framework regions (2.83 vs 1.41, P < .001), (2) higher transition to transversion ratio than would be expected if mutations were random (1.49 vs 0.5, P < .001), and (3) higher than expected concentration of mutations within RGYW hot spots (13.92% vs 3.33%, P < .001). HCLv met these 3 criteria of canonical SHM to a lesser extent. These data suggest that, whereas HCLc cells may recognize antigen-like CLL and normal B cells before malignant transformation, HCLv cells from some patients may originate differently, possibly without undergoing antigen recognition.

Hairy-cell leukemia variant: recent view on diagnosis, biology and treatment

Hairy-cell leukemia variant (HCl-V) is a district clinico-pathological entity with intermediate features between classical HCl (HCl-C) and B-cell prolymphocytic leukemia. HCl-V is now included in the World Health Organization (WHO) classification as a provisional entity. It is an uncommon disorder accounting for approximately 0.4% of chronic lymphoid malignancies and 10% of all HCl cases. In contrast to HCl-C, HCl-V is a more aggressive disease and according to the new WHO classification it is no longer considered to be biologically related to HCl-C. Patients with HCl-V have an elevated white blood count, easy-to-aspirate bone marrow and weak reactivity to tartrate - resistant acid phosphatase (TRAP). Immunophenotypically, HCl-V cells are positive for CD103 and CD11c and negative for CD25. The HCl-V cells express also the B-cell antigens, CD19, CD20 and CD22. The HCl-V patients have frequently an unmutated Ig gene configuration. Currently, the principles of therapy for this rare disease derive from uncontrolled single institutional studies, or even single case reports. In contrast to HCl-C, the HCl-V response to purine nucleoside analogs (PNA) is limited to partial responses in approximately 50% of patients. However, complete responses were observed in patients treated with rituximab and anti-CD22 immunotoxins. In Japan, a distinct subtype of HCl known as HCl-Japanese variant (HCl-JV) has been identified. As with HCl-V, patients with HCl-JV have leukocytosis, weak TRAP activity in leukemic cells, and lack of CD25 antigen. In this review, the biology, diagnostic criteria, and current therapeutic options in HCl-V and HCl-JV are presented.

VH4-34+ hairy cell leukemia, a new variant with poor prognosis despite standard therapy

Hairy cell leukemia variant (HCLv) presents with high disease burden, lack of typical antigens like CD25, and poor response to standard treatments like cladribine. Occasionally, patients with classic HCL respond poorly. Clinical and molecular features of HCL and HCLv has not been compared. Rearrangements expressing immunoglobulin VH chain were sequenced, including 22 from 20 patients with HCLv and 63 from 62 patients with classic HCL. Most patients were seeking relapsed/refractory trials, representing a poor-prognosis population. VH4-34, a gene commonly used in autoimmune disorders, was observed in 8 (40%) HCLv and 6 (10%) classic (P = .004) HCL patients. Compared with 71 VH4-34(-) rearrangements, 14 VH4-34(+) rearrangements were more frequently (P < .001) unmutated, defined as greater than 98% homologous to germline sequence. VH4-34(+) patients had greater white blood cell counts at diagnosis (P = .002), lower response rate (P < .001) and progression-free survival (P = .007) after initial cladribine, and shorter overall survival from diagnosis (P < .001). Response and survival were more closely related to VH4-34 status than to whether or not patients had HCLv. VH4-34(+) HCL is an important disorder that only partly overlaps with the previously described HCLv. Response to initial single-agent cladribine therapy is suboptimal; these patients should be considered for alternative approaches, including antibody-related therapy.