The effects of CAMPATH-1H on cell viability do not correlate to the CD52 density on the cell surface

Targeting T Follicular Helper Cells to Control Humoral Allogeneic Immunity

Humoral allogeneic immunity driven by anti-HLA donor-specific antibodies and antibody-mediated rejection (AMR) significantly impede prolonged survival of organ allografts after transplantation. Although the importance of T follicular helper (TFH) cells in controlling antibody responses has been long established, their role in directing donor-specific antibody generation leading to AMR was only recently appreciated in the clinical setting of organ transplantation. In this review, we provide a comprehensive summary of the current knowledge on the biology of human TFH cells as well as their circulating counterparts and describe their pivotal role in driving humoral alloimmunity. In addition, we discuss the intrinsic effects of current induction therapies and maintenance immunosuppressive drugs as well as of biotherapies on TFH cells and provide future directions and novel opportunities of biotherapeutic targeting of TFH cells that have the potential of bringing the prophylactic and curative treatments of AMR toward personalized and precision medicine.

Event-Driven Immunoprofiling Predicts Return of Disease Activity in Alemtuzumab-Treated Multiple Sclerosis

Background: Alemtuzumab is a highly effective drug for the treatment of multiple sclerosis (MS), characterized by specific patterns of depletion and repopulation. As an induction-like treatment concept, two mandatory infusion courses can inhibit long-term disease activity in the majority of patients, and additional courses can successfully manage subsequent re-emergence of disease activity. Currently, there are no biomarkers to identify patients with re-emergent disease activity requiring retreatment.

Methods: In this study, we systematically characterized 16 MS patients commencing alemtuzumab. Clinical parameters, MRI and detailed immunoprofiling were conducted every 3 months for up to 84 months.

Results: Alemtuzumab led to significant decrease in clinical disease activity in all evaluated patients. Nine out of 16 patients presented with no evidence of disease activity (NEDA)-3 up to 84 months (“complete-responder”), while 7 patients demonstrated clinical or/and subclinical MRI disease activity and received alemutzumab retreatment (“partial-responder”). In both response categories, all T- and B-cell subsets were markedly depleted after alemtuzumab therapy. In particular, absolute numbers of Th1 and Th17 cells were markedly decreased and remained stable below baseline levels—this effect was particularly pronounced in complete-responders. While mean cell numbers did not differ significantly between groups, analysis of event-driven immunoprofiling demonstrated that absolute numbers of Th1 and Th17 cells showed a reproducible increase starting 6 months before relapse activity. This change appears to predict emergent disease activity when compared with stable disease.

Conclusion: Studies with larger patient populations are needed to confirm that frequent immunoprofiling may assist in evaluating clinical decision-making of alemtuzumab retreatment.

Brief Report: CD52 Expression on CD4+ T Cells in HIV-Positive Individuals on cART

BACKGROUND

HIV persists in a latent state in quiescent CD4 T cells preventing eradication of HIV. CD52 is a surface molecule modulated by HIV. We aimed at examining factors related to CD52 expression on CD4 T cells in HIV-positive individuals and the impact of initiation of combination antiretroviral therapy (cART).

METHODS

Peripheral blood mononuclear cells from 18 HIV-positive individuals and 10 uninfected age- and sex-matched controls were examined by flow cytometry for CD38 and CD52 expression on CD4 T cells. Stimulation assays were performed on 8 healthy blood donors to determine a cutoff for CD52 expression.

RESULTS

All examined CD4 T cells expressed CD52. However, both CD4 T cells with higher (CD52) and with lower CD52 expression (CD52dim) were found in HIV-positive individuals compared to uninfected controls. Two % CD52dim cells defined groups of high and low CD52: the group of individuals with high CD52 had higher CD4 counts at baseline (447 vs. 54 cells/µL, P = 0.02) and higher increase in CD4 counts during follow-up compared with low CD52 (P = 0.02). After 12 months of cART, CD52 increased (median fluorescence intensity 4846 vs. 5621, P < 0.05), whereas CD38 decreased (median fluorescence intensity 1519 vs. 730, P < 0.0001).

CONCLUSIONS

All HIV-positive individuals in this cohort had CD4 T cells that expressed CD52. Higher CD4 counts were found in those with high CD52. Furthermore, an increase in CD52 was found after 12 months of cART, indicating that anti-CD52 antibodies may be more efficient for depletion of CD4 T cells in HIV-positive individuals on cART.

Principles of alemtuzumab immunoablation in hematopoietic cell transplantation for non-malignant diseases in children: A review

Alemtuzumab is a humanized mAb targeted to CD52. Alemtuzumab is highly immunosuppressive with the ability to deplete T and B cells (in addition to other immune cell lines). A growing understanding of the PKs, dosing, and timing of administration of alemtuzumab has allowed for the study of its use as a conditioning agent for allogeneic HCT. The highly immunosuppressive properties of the drug are particularly appealing in the setting of non-malignant HCT, where GVHD provides no clinical benefit and relapse of malignancy is not applicable. In addition, the degree of immune suppression achieved with alemtuzumab has allowed for a reduction in the intensity of myeloablative cytotoxic agents included in some HCT conditioning regimens, allowing for fewer acute and late toxicities. This review paper will provide a comprehensive summary of the mechanism of action, PKs, dosing, and timing of alemtuzumab, a brief description of its use in various allogeneic HCT protocols for non-malignant conditions and a summary of the data regarding its use for GVHD therapy. The goal of this review was to provide an understanding as to how alemtuzumab might be safely incorporated into HCT conditioning regimens for children with non-malignant disease, allowing for expanded access to curative HCT therapy.

The immunological function of CD52 and its targeting in organ transplantation

INTRODUCTION

CD52 (Campath-1 antigen), a glycoprotein of 12 amino acids anchored to glycosylphosphatidylinositol, is widely expressed on the cell surface of immune cells, such as mature lymphocytes, natural killer cells (NK), eosinophils, neutrophils, monocytes/macrophages, and dendritic cells (DCs). The anti-CD52 mAb, alemtuzumab, was used widely in clinics for the treatment of patients such as organ transplantation. In the present manuscript, we will briefly summarize the immunological function of CD52 and discuss the application of anti-CD52 mAb in transplantation settings.

FINDINGS

We reviewed studies published until July 2016 to explore the role of CD52 in immune cell function and its implication in organ transplantation. We showed that ligation of cell surface CD52 molecules may offer costimulatory signals for T-cell activation and proliferation. However, soluble CD52 molecules will interact with the inhibitory sialic acid-binding immunoglobulin-like lectin 10 (Siglec10) to significantly inhibit T cell proliferation and activation. Although the physiological and pathological significances of CD52 molecules are still poorly understood, the anti-CD52 mAb, alemtuzumab, was used widely for the treatment of patients with chronic lymphocytic leukemia, autoimmune diseases as well as cell and organ transplantation in clinics.

CONCLUSION

Studies clearly showed that CD52 can modulate T-cell activation either by its intracellular signal pathways or by the interaction of soluble CD52 and Siglec-10 expressing on T cells. However, the regulatory functions of CD52 on other immune cell subpopulations in organ transplantation require to be studied in the near future.

The HOVON68 CLL trial revisited: performance status and comorbidity affect survival in elderly patients with chronic lymphocytic leukemia

In the HOVON68 CLL trial, patients 65 to 75 years of age had no survival benefit from the addition of low-dose alemtuzumab to fludarabine and cyclophosphamide (FC) in contrast to younger patients. The reasons are explored in this 5-year trial update using both survival analysis and competing risk analysis on non-CLL-related mortality. Elderly FCA patients died more frequently from causes not related to CLL, and more often related to comorbidity (mostly cardiovascular) than to infection. In a Cox multivariate analysis, del(17p), performance status >0, and comorbidity were associated with a higher non-CLL-related mortality in the elderly independent of the treatment modality. Thus, while the 'fit' elderly with no comorbidity or performance status of 0 might potentially benefit from chemo-immunotherapy with FC, caution is warranted, when considering alemtuzumab treatment in elderly patients with cardiovascular comorbidity.

Effect of Immunosuppressive Drugs on Humoral Allosensitization after Kidney Transplant

The negative effect of donor-specific antibodies on the success of solid transplant is now clearly established. However, the lack of effective treatment to prevent the development of antibody-mediated lesions deepens the need for clinicians to focus on primary prevention of de novo humoral allosensitization. Among the factors associated with the risk of developing de novo donor-specific antibodies, therapeutic immunosuppression is the most obvious parameter in which improvement is possible. Beyond compliance and the overall depth of immunosuppression, it is likely that the nature of the drugs is also crucial. Here, we provide an overview of the molecular effect of the various immunosuppressive drugs on B cell biology. Clinical data related to the effect of these drugs on de novo humoral allosensitization are also examined, providing a platform from which clinicians can optimize immunosuppression for prevention of de novo donor-specific antibody generation at the individual level.