Comparison of Two Strategies to Generate Antigen-Specific Human Monoclonal Antibodies: Which Method to Choose for Which Purpose?

Human monoclonal antibodies (mAbs) are valuable tools to link genetic information with functional features and to provide a platform for conformational epitope mapping. Additionally, combined data on genetic and functional features provide a valuable mosaic for systems immunology approaches. Strategies to generate human mAbs from peripheral blood have been described and used in several studies including single cell sequencing of antigen-binding B cells and the establishment of antigen-specific monoclonal Epstein-Barr Virus (EBV) immortalized lymphoblastoid cell lines (LCLs). However, direct comparisons of these two strategies are scarce. Hence, we sought to set up these two strategies in our laboratory using peanut 2S albumins (allergens) and the autoantigen anti-Rho guanosine diphosphate dissociation inhibitor 2 (RhoGDI2, alternatively 'ARHGDIB') as antigen targets to directly compare these strategies regarding costs, time expenditure, recovery, throughput and complexity. Regarding single cell sequencing, up to 50% of corresponding V(D)J gene transcripts were successfully amplified of which 54% were successfully cloned into expression vectors used for heterologous expression. Seventy-five percent of heterologously expressed mAbs showed specific binding to peanut 2S albumins resulting in an overall recovery of 20.3%, which may be increased to around 29% by ordering gene sequences commercially for antibody cloning. In comparison, the establishment of monoclonal EBV-LCLs showed a lower overall recovery of around 17.6%. Heterologous expression of a mAb carrying the same variable region as its native counterpart showed comparable concentration-dependent binding abilities. By directly comparing those two strategies, single cell sequencing allows a broad examination of antigen-binding mAbs in a moderate-throughput manner, while the establishment of monoclonal EBV-LCLs is a powerful tool to select a small number of highly reactive mAbs restricted to certain B cell subpopulations. Overall, both strategies, initially set-up for peanut 2S albumins, are suitable to obtain human mAbs and they are easily transferrable to other target antigens as shown for ARHGDIB.

ARHGDIB and AT1R autoantibodies are differentially related to the development and presence of chronic antibody-mediated rejection and fibrosis in kidney allografts.

The role of non-HLA autoantibodies in chronic-active antibody-mediated rejection (c-aABMR) of kidney transplants is largely unknown. In this study, the presence and clinical relevance of non-HLA autoantibodies using a recently developed multiplex Luminex-based assay were investigated. Patients with a kidney allograft biopsy at least 6 months after transplantation with a diagnosis of c-aABMR (n = 36) or no rejection (n = 21) were included. Pre-transplantation sera and sera at time of biopsy were tested for the presence of 14 relevant autoantibodies. A significantly higher signal for autoantibodies against Rho GDP-dissociation inhibitor 2 (ARHGDIB) was detected in recipients with c-aABMR as compared to recipients with no rejection. However, ARHGDIB autoantibodies did not associate with graft survival. Levels of autoantibodies against angiotensin II type 1-receptor (AT1R) and peroxisomal trans-2-enoyl-CoA reductase (PECR) were increased in recipients with interstitial fibrosis in their kidney biopsy. Only the signal for AT1R autoantibody showed a linear relationship with the degree of interstitial fibrosis and was associated with graft survival. In conclusion, anti-ARHGDIB autoantibodies are increased when c-aABMR is diagnosed but are not associated with graft survival, while higher levels of AT1R autoantibody are specifically associated with the presence of interstitial fibrosis and graft survival.

Antibodies Against ARHGDIB and ARHGDIB Gene Expression Associate With Kidney Allograft Outcome.

BACKGROUND: The impact of donor-specific anti-HLA antibodies (DSA) on antibody-mediated rejection (AMR) and kidney allograft failure is well established. However, the relevance of non-HLA antibodies remains unclear. METHODS: We investigated 13 pretransplant non-HLA antibodies and their association with histology of AMR (AMRh) and kidney allograft failure. We included single kidney recipients (n = 203) with AMRh, according to the Banff 2017 classification and matched AMRh-free controls (n = 219). Non-HLA antibodies were assessed using multiplex Luminex assay. RESULTS: Of the selected non-HLA antibodies (against agrin, adipocyte plasma membrane-associated protein, Rho GDP-dissociation inhibitor 2 [ARHGDIB], Rho guanine nucleotide exchange factor 6, angiotensin-II type 1 receptor, endothelin type A receptor, lamin B1, BPI fold-containing family B member 1, peroxisomal trans-2-enoyl-coenzyme A reductase, phospholipase A2 receptor, protein kinase C zeta type, tubulin beta-4B class IVb, vimentin), only antibodies against ARHGDIB (adjusted median fluorescence intensity [aMFI] ≥ 1000), a minor histocompatibility antigen, associated with graft failure, in univariate and multivariate models (hazard ratio = 2.7; 95% confidence interval [CI],1.3-5.4; P = 0.007). There was a 19.5-fold (95% CI, 6.0-63.9; P < 0.0001) increased risk of graft failure in patients positive for both DSA and anti-ARHGDIB antibodies (aMFI ≥ 1000) versus patients negative for both DSA and anti-ARHGDIB antibodies, compared with a 4.4-fold (95% CI, 2.4-8.2; P < 0.0001) increased risk in patients with only DSA, and a 4.1-fold (95% CI, 1.4-11.7; P = 0.009) increased risk in patients with only anti-ARHGDIB antibodies above 2000 aMFI. AMRh associated with increased intrarenal expression of the ARHGDIB gene. In the absence of AMRh and DSA, anti-ARHGDIB antibodies were not clearly associated with graft failure. CONCLUSIONS: The presence of pretransplant anti-ARHGDIB antibodies has an additive effect in patients with DSA on the risk of graft failure via AMRh. Other investigated non-HLA antibodies, including antibodies against angiotensin-II type 1 receptor, did not contribute to risk stratification and could not explain the histology of AMR in the absence of DSA.

Antibodies against ARHGDIB are associated with long-term kidney graft loss.

The clinical significance of non-HLA antibodies on renal allograft survival is a matter of debate, due to differences in reported results and lack of large-scale studies incorporating analysis of multiple non-HLA antibodies simultaneously. We developed a multiplex non-HLA antibody assay against 14 proteins highly expressed in the kidney. In this study, the presence of pretransplant non-HLA antibodies was correlated to renal allograft survival in a nationwide cohort of 4770 recipients transplanted between 1995 and 2006. Autoantibodies against Rho GDP-dissociation inhibitor 2 (ARHGDIB) were significantly associated with graft loss in recipients transplanted with a deceased-donor kidney (N = 3276) but not in recipients of a living-donor kidney (N = 1496). At 10 years after deceased-donor transplantation, recipients with anti-ARHGDIB antibodies (94/3276 = 2.9%) had a 13% lower death-censored covariate-adjusted graft survival compared to the anti-ARHGDIB-negative (3182/3276 = 97.1%) population (hazard ratio 1.82; 95% confidence interval, 1.32-2.53; P = .0003). These antibodies occur independently from donor-specific anti-HLA antibodies (DSA) or other non-HLA antibodies investigated. No significant relations with graft loss were found for the other 13 non-HLA antibodies. We suggest that pretransplant risk assessment can be improved by measuring anti-ARHGDIB antibodies in all patients awaiting deceased-donor transplantation.

Autoantibodies specific to D4GDI modulate Rho GTPase mediated cytoskeleton remodeling and induce autophagy in T lymphocytes.

T lymphocytes from patients with Systemic Lupus Erythematosus (SLE) display multiple abnormalities, including increased cell activation, abnormal cell death by apoptosis and impairment of autophagy pathway. In the present study we report the presence of specific antibodies to D4GDI, a small GTPase family inhibitor, in a significant percentage (46%) of SLE patient sera. We also found a significant association between the presence of these autoantibodies and hematologic manifestations occurring in these patients. Investigating the possible implication of anti-D4GDI autoantibodies in SLE pathogenesis or progression, we found that these antibodies were capable of binding D4GDI expressed at the lymphocyte surface and triggering a series of subcellular events, including Rho GTPase activation. These antibodies were also able to induce autophagy in T cells from both healthy donors and SLE patients, but only those negative to these antibodies. We can conclude that anti-D4GDI autoantibodies could be capable of triggering important responses in T cells such as cytoskeleton remodeling and autophagy pathway and that, in SLE patients, the chronic exposure to these specific autoantibodies could lead to the selection of autophagy-resistant T cell clones contributing to the pathogenesis of the disease.