Persistent panhypogammaglobulinemia with selected loss of memory B cells and impaired isotype expression after rituximab therapy for post-transplant EBV-associated autoimmune hemolytic anemia

B cell subsets reconstitution and immunoglobulin levels in children and adolescents with B non-Hodgkin lymphoma after treatment with single anti CD20 agent dose included in chemotherapeutic protocols: single center experience and review of the literature

BACKGROUND

RTX, an anti-CD20 monoclonal antibody, added to chemotherapy has proven to be effective in children and adolescents with high-grade, high-risk and matured non-Hodgkin lymphoma. RTX leads to prompt CD19+ B lymphocyte depletion. However, despite preserved immunoglobulin production by long-lived plasmablasts after treatment, patients remain at risk of prolonged hypogammaglobulinemia. Further, there are few general guidelines for immunology laboratories and clinical feature monitoring after B cell-targeted therapies. The aim of this paper is to describe B cell reconstitution and immunoglobulin levels after pediatric B-NHL protocols, that included a single RTX dose and to review the literature.

METHODS

A retrospective single-center study on the impact of a single RTX dose included in a chemotherapeutic pediatric B Non-Hodgkin Lymphoma (B-NHL) treatment protocols. Immunology laboratory and clinical features were evaluated over an eight hundred days follow-up (FU) period, after completing B-NHL treatment.

RESULTS

Nineteen patients (fifteen Burkitt lymphoma, three Diffuse large B cell lymphoma, and one Marginal zone B cell lymphoma) fulfilled the inclusion criteria. Initiation of B cell subset reconstitution occurred a median of three months after B-NHL treatment. Naïve and transitional B cells declined over the FU in contrast to the marginal zone and the switched memory B cell increase. The percentage of patients with IgG, IgA, and IgM hypogammaglobulinemia declined consistently over the FU. Prolonged IgG hypogammaglobulinemia was detectable in 9%, IgM in 13%, and IgA in 25%. All revaccinated patients responded to protein-based vaccines by specific IgG antibody production increase. Following antibiotic prophylaxes, none of the patients with hypogammaglobulinemia manifested with either a severe or opportunistic infection course.

CONCLUSION

The addition of a single RTX dose to the chemotherapeutic treatment protocols was not shown to increase the risk of developing secondary antibody deficiency in B-NHL pediatric patients. Observed prolonged hypogammaglobulinemia remained clinically silent. However interdisciplinary agreement on regular long-term immunology FU after anti-CD20 agent treatment is required.

Secondary rituximab-associated versus primary immunodeficiencies: The enigmatic border

Rituximab (RTX), a chimeric monoclonal antibody targeting CD20-positive cells, is a valuable treatment option for malignant and benign immune-related disorders. The rationale of targeting the CD20 antigen relies on depletion of both healthy and autoreactive/malignant CD20-espressing cells, but normal B-cell reconstitution is expected within months after treatment. Nevertheless, a number of recent studies have documented prolonged B-cell deficiency associated with new-onset hypogammaglobulinemia in patients receiving RTX. Awareness of post-RTX hypogammaglobulinemia has become wider among clinicians, with a growing number of reports about the increased incidence, especially in children. Although these patients were previously regarded as affected by secondary/iatrogenic immunodeficiency, atypical clinical and immunological manifestations (e.g., severe or opportunistic infections; prolonged B-cell aplasia) raise concerns of delayed manifestations of genetic immunological disorders that have been unveiled by B-cell perturbation. As more patients with undiagnosed primary immune deficiency receiving RTX have been identified, it remains the challenge in discerning those that might display a higher risk of persistent RTX-associated hypogammaglobulinemia and need a tailored immunology follow-up. In this review, we summarize the principal evidence regarding post-RTX hypogammaglobulinemia and provide a guideline for identifying patients at higher risk of RTX-associated hypogammaglobulinemia that could harbor an inborn error of immunity.

Persistence of Virus-Specific Antibody after Depletion of Memory B Cells

Following vaccination or primary virus infection, virus-specific antibodies provide the first line of defense against reinfection. Plasma cells residing in the bone marrow constitutively secrete antibodies, are long-lived, and can thus maintain serum antibody levels over extended periods of time in the absence of antigen.

Persistent hypogammaglobulinemia due to immunoglobulin class switch impairment by peri-transplant rituximab therapy

Post-transplant lymphoproliferative disorder (PTLD) is one of the most serious complications of allogeneic hematopoietic stem cell transplantation (HSCT). Rituximab is effective for PTLD; however, rituximab can produce adverse effects, including hypogammaglobulinemia. Here, we present the case of an 18-year-old female with refractory cytopenia of childhood who developed persistent selective hypogammaglobulinemia with low immunoglobulin G (IgG) 2 and IgG4 levels and monoclonal protein after rituximab therapy against probable PTLD. Despite B-cell recovery, the serum IgG levels gradually declined, reaching < 300 mg/dL at 33 months after rituximab treatment. In addition, class-switched memory (CD27⁺IgD^-) B cells were limited in phenotypic analysis. These findings suggest that peri-HSCT rituximab may contribute to an abnormal B-cell repertoire induced by impaired immunoglobulin class switch.

Low dose Rituximab for pre-emptive treatment of Epstein Barr virus reactivation after allogenic hematopoietic stem cell transplantation

INTRODUCTION

The most used preemptive therapy for Epstein Barr virus reactivation post allogeneic hematopoietic stem cell (HSCT) transplant is Rituximab, 375 mg/m2, once weekly until EBV viremia negativity. There is no data suggesting such a high dose.

OBJECTIVE

We hypothesized that a lower dose of Rituximab would be as efficient with less toxicity.

PATIENTS

In a retrospective, monocentric study, we analyzed 16 consecutive patients treated preemptively with low dose Rituximab for EBV reactivation post HSCT. Patients were treated with low Rituximab dose of 100 mg/m² weekly. Success was defined by a decrease of EBV viremia of 1 log¹⁰ and below 1000 UI/ml, and the absence of post-transplant lymphoproliferative disorder (PTLD).

RESULTS

Success rate was 93.4% (15/16). One (1/16, 6%) PTLD was diagnosed after preemptive therapy, despite a negative viremia.

CONCLUSION

A low dose of Rituximab of 100 mg/m² per injection for pre-emptive therapy of EBV reactivation post HSCT is safe and effective for preventing PTLD. Prospective, randomized, multicentric trials with larger number of patient are needed to determine the best rituximab dose.

Risk factors predisposing to the development of hypogammaglobulinemia and infections post-Rituximab

Rituximab (RTX) is a monoclonal antibody against CD20, commonly used in the treatment of hematological malignancies and autoimmune diseases. The use of RTX is related to the development of hypogammaglobulinemia and infections. Aim of this review is to summarize the evidence supporting the association of specific risk factors with the development of hypogammaglobulinemia and infections post-RTX. Immunological complications are more common in patients with malignant diseases as compared to non-malignant diseases. Moreover, the use of more than one dose of RTX, maintenance regimens, low pre-treatment basal immunoglobulin levels and the association with Mycophenolate and purine analogues represent risk factors for the development of hypogammaglobulinemia. The number of RTX courses, the evidence of low IgG levels for more than 6 months, the use of G-CSF, the occurrence of chronic lung disease, cardiac insufficiency, extra-articular involvement in patients with rheumatoid arthritis, low levels of IgG and older age have been correlated with a higher risk of infections. Even though the heterogeneity of the studies in terms of study population age and underlying disease, RTX schedules as well as differences in pre-treatment or concomitant therapy doesn't allow drawing definitive conclusions, the study of the literature highlight the association of specific risk factors with the occurrence of hypogammaglobulinemia and/or infections. A long term randomized controlled clinical trial could be useful to define a personalized evidence-based risk management plan for patients treated with RTX.

Severe and fatal adverse events risk associated with rituximab addition to B-cell non-Hodgkin's lymphoma (B-NHL) chemotherapy: a meta-analysis

PURPOSE

Rituximab is a monoclonal antibody targetting the CD20 antigen with the ability to increase overall remission (OR) in B-cell non-Hodgkin's lymphoma (B-NHL). A systematic review and meta-analysis were conducted to determine the risk of the most clinically relevant severe and fatal adverse events (AEs) associated with the use of rituximab in the treatment of B-NHL.

PATIENTS AND METHODS

We included phase III clinical trials that used chemotherapy in combination with rituximab or chemotherapy alone as for B-NHL. Statistical analyses were conducted to calculate summary risk ratio (RR) of the relevant severe and fatal AEs related with rituximab.

RESULTS

Eight randomised controlled clinical trials were included in this meta-analysis. Summary RR obtained showed no statistically significant rituximab-associated increased risk in 13 severe adverse events (SAEs) (infection, fever, anaemia, thrombocytopaenia, granulocytopenia, liver toxicity, cardiac toxicity, neurologic toxicity, lung toxicity, mucositis, nausea/vomiting, diarrhoea, alopecia) except leukocytopenia (36.4% versus 31%; RR = 1.13; 95%CI, 1.01-1.27; P = 0.03). The incidences of fatal AEs showed noteworthy difference between rituximab group and control group (RR = 1.45; 95% CI, 1.04-2.02; P = 0.03).

CONCLUSION

This meta-analysis indicates that there was no proof of statistically higher incidence of most SAEs in rituximab containing group compared with chemotherapy alone. However, fatal infections were more frequently observed in patients who received rituximab. Considering the low-incidence infection-induced death during the treatment period, the effects of rituximab on infections need further investigation.

Immunoglobulin replacement therapy in secondary hypogammaglobulinemia

Immunoglobulin (Ig) replacement therapy dramatically changed the clinical course of primary hypogammaglobulinemias, significantly reducing the incidence of infectious events. Over the last two decades its use has been extended to secondary antibody deficiencies, particularly those related to hematological disorders as lymphoproliferative diseases (LPDs) and multiple myeloma. In these malignancies, hypogammaglobulinemia can be an intrinsic aspect of the disease or follow chemo-immunotherapy regimens, including anti-CD20 treatment. Other than in LPDs the broadening use of immunotherapy (e.g., rituximab) and immune-suppressive therapy (steroids, sulfasalazine, and mycophenolate mofetil) has extended the occurrence of iatrogenic hypogammaglobulinemia. In particular, in both autoimmune diseases and solid organ transplantation Ig replacement therapy has been shown to reduce the rate of infectious events. Here, we review the existing literature about Ig replacement therapy in secondary hypogammaglobulinemia, with special regard for subcutaneous administration route, a safe, effective, and well-tolerated treatment approach, currently well established in primary immunodeficiencies and secondary hypogammaglobulinemias.

Subcutaneous immunoglobulin in lymphoproliferative disorders and rituximab-related secondary hypogammaglobulinemia: a single-center experience in 61 patients

Intravenous immunoglobulin replacement therapy represents the standard treatment for hypogammaglobulinemia secondary to B-cell lymphoproliferative disorders. Subcutaneous immunoglobulin infusion is an effective, safe and well-tolerated treatment approach in primary immunodeficiencies but no extensive data are available on their use in secondary hypogammaglobulinemia, a frequent phenomenon occurring after treatment with anti-CD20 monoclonal antibodies in lymphoproliferative disorders. In this retrospective study we evaluated efficacy (serum IgG trough levels, incidence of infections per year, need for antibiotics) and safety (number of adverse events) of intravenous (300 mg/kg/4 weeks) versus subcutaneous (75 mg/kg/week) immunoglobulin replacement therapy in 61 patients. In addition, the impact of the infusion methods on quality of life was compared. All patients were treated with subcutaneous immunoglobulin, and 33 out of them had been previously treated with intravenous immunoglobulin. Both treatments appeared to be effective in replacing Ig production deficiency and in reducing the incidence of infectious events and the need for antibiotics. Subcutaneous immunoglobulin obtained a superior benefit when compared to intravenous immunoglobulin achieving higher IgG trough levels, lower incidence of overall infection and need for antibiotics. The incidence of serious bacterial infections was similar with both infusion ways. As expected, a lower number of adverse events was registered with subcutaneous immunoglobulin, compared to intravenous immunoglobulin, with no serious adverse events. Finally, we observed an improvement in health-related quality of life parameters after the switch to subcutaneous immunoglobulin. Our results suggest that subcutaneous immunoglobulin is safe and effective in patients with hypogammaglobulinemia associated to lymphoproliferative disorders.

Fulminant viral myocarditis after rituximab therapy in pediatric nephrotic syndrome

BACKGROUND

We report a 7-year-old boy with high-degree steroid-dependent idiopathic nephrotic syndrome (SDNS) who went into remission with rituximab (RTX) maintenance therapy.

CASE-DIAGNOSIS/TREATMENT

Four months after this patient received his first RTX infusion, there was a progressive and sustained decrease of immunoglobulin (Ig)G and IgM levels. Thirteen months after the initiation of RTX therapy he was in sustained remission without any steroid or oral immunosuppressive therapy; however, B cell depletion was still present. At this time he developed a fulminant myocarditis due to enterovirus. Despite aggressive treatment and the administration of intravenous polyvalent immunoglobulins there was no clinical improvement. He successfully underwent heart transplant surgery.

CONCLUSIONS

We conclude that B cell depletion with RTX is efficacious in the treatment of paediatric SDNS but that it may be associated with severe infectious complications. Therefore, we recommend a close monitoring of Ig levels in children who have received RTX therapy and a supplementation with intravenous Ig as soon as the Ig levels fall below the lower limit of the normal range.

Common variable immunodeficiency unmasked by treatment of immune thrombocytopenic purpura with Rituximab

Background

Hypogammaglobulinemia may be part of several different immunological or malignant conditions, and its origin is not always obvious. Furthermore, although autoimmune cytopenias are known to be associated with common variable immunodeficiency (CVID) and even may precede signs of immunodeficiency, this is not always recognized. Despite novel insight into the molecular immunology of common variable immunodeficiency, several areas of uncertainty remain. In addition, the full spectrum of immunological effects of the B cell depleting anti-CD20 antibody Rituximab has not been fully explored. To our knowledge this is the first report of development of CVID in a patient with normal immunoglobulin prior to Rituximab treatment.

Case presentation

Here we describe the highly unusual clinical presentation of a 34-year old Caucasian male with treatment refractory immune thrombocytopenic purpura and persistent lymphadenopathy, who was splenectomized and received multiple courses of high-dose corticosteroid before treatment with Rituximab resulted in a sustained response. However, in the setting of severe pneumococcal meningitis, hypogammaglobulinemia was diagnosed. An extensive immunological investigation was performed in order to characterize his immune status, and to distinguish between a primary immunodeficiency and a side effect of Rituximab treatment. We provide an extensive presentation and discussion of the literature on the basic immunology of CVID, the mechanism of action of Rituximab, and the immunopathogenesis of hypogammaglobulinemia observed in this patient.

Conclusions

We suggest that CVID should be ruled out in any patient with immune cytopenias in order to avoid diagnostic delay. Likewise, we stress the importance of monitoring immunoglobulin levels before, during, and after Rituximab therapy to identify patients with hypogammaglobulinemia to ensure initiation of immunoglobulin replacement therapy in order to avoid life-threatening invasive bacterial infections. Recent reports indicate that Rituximab is not contra-indicated for the treatment of CVID-associated thrombocytopenia, however concomitant immunoglobulin substitution therapy is of fundamental importance to minimize the risk of infections. Therefore, lessons can be learned from this case report by clinicians caring for patients with immunodeficiencies, haematological diseases or other autoimmune disorders, particularly, when Rituximab treatment may be considered.

CD20-targeted T cells after stem cell transplantation for high risk and refractory non-Hodgkin's lymphoma

A phase I trial of infusing anti-CD3 × anti-CD20 bispecific antibody (CD20Bi) armed activated T cells (aATC) was conducted in high-risk/refractory non-Hodgkin's lymphoma patients to determine whether aATC infusions are safe, affect immune recovery, and induce an antilymphoma effect. Ex vivo expanded ATC from 12 patients were armed with anti-CD20 bispecific antibody, cryopreserved, and infused after autologous stem cell transplantation (SCT). Patients underwent SCT after high-dose chemotherapy, and aATC infusions were started on day +4. The patients received 1 infusion of aATC per week for 4 weeks after SCT with doses of 5, 10, 15, and 20 × 10(9). aATC infusions were safe and did not impair engraftment. The major side effects were chills, fever, hypotension, and fatigue. The mean number of IFN-γ Enzyme-linked Immunosorbent Spots (ElSpots) directed at CD20 positive lymphoma cells (DAUDI, P = .0098) and natural killer cell targets (K562, P < .0051) and the mean specific cytotoxicity directed at DAUDI (P = .037) and K562 (P = .002) from pre-SCT to post-SCT were significantly higher. The increase in IFN-γ EliSpots from pre-SCT to post-SCT in patients who received armed ATC after SCT were significantly higher than those in patients who received SCT alone (P = .02). Serum IL-7, IL-15, Macrophage inflammatory protein (MIP)-1 beta, IP-10, MIP-1α, and Monokine induced by gamma interferone increased within hours after infusion. Polyclonal and specific antibodies were near normal 3 months after SCT. aATC infusions were safe and increased innate and specific antilymphoma cell immunity without impairing antibody recovery after SCT.

Sustained hypogammaglobulinemia under rituximab maintenance therapy could increase the risk for serious infections: a report of two cases

We report two patients with granulomatosis with polyangiitis in remission with rituximab maintenance therapy with sustained hypogammaglobulinemia. Both patients had serious infections and were admitted to the intensive therapy unit. The patients had at least low IgM levels prior to the initiation of rituximab. They received cyclophosphamide and prednisolone at induction and at maintenance. They had lung affection, low level of both IgM and IgG and a cumulative dose of rituximab over 7 g at the time of the severe infection. Our patients have features similar to common variable immunodeficiency patients, and therefore prolonged very low levels of immunoglobulins could heighten the risk for severe infections.

Diagnostic strategy for patients with hypogammaglobulinemia in rheumatology

The discovery of hypogammaglobulinemia, which is defined as a plasmatic level of immunoglobulin (Ig) under 5 g/L is rare in clinical practice. However, the management of immunodepressed patients in rheumatology, sometimes due to the use of immunosuppressive treatments such as anti-CD20 in chronic inflammatory rheumatisms, increases the risk of being confronted to this situation. The discovery of hypogammaglobulinemia in clinical practice, sometimes by chance, must never be neglected and requires a rigorous diagnosis approach. First of all, in adults, secondary causes, in particular lymphoid hemopathies or drug-related causes (immunosuppressors, antiepileptics) must be eliminated. A renal (nephrotic syndrome) or digestive (protein-losing enteropathy) leakage of Ig is also possible. More rarely, it is due to an authentic primary immunodeficiency (PID) discovered in adulthood: common variable immunodeficiency (CVID) which is the most frequent form of PID, affects young adults between 20 and 30 years and can sometimes trigger joint symptoms similar to those in rheumatoid arthritis; or Good syndrome, which associates hypogammaglobulinemia, thymoma and recurrent infections around the age of 40 years. In most cases, after confirming hypogammaglobulinemia on a second test, biological examinations and thoracic-abdominal-pelvic CT scan will guide the diagnosis, after which the opinion of a specialist can be sought depending on the findings of the above examinations. At the end of this review, we provide a decision tree to guide the clinician confronted to an adult-onset hypogammaglobulinemia.

Successful treatment of mixed-type autoimmune hemolytic anemia with rituximab in a child following liver transplantation

Development of a severe form of mixed-type AIHA after orthotopic liver transplantation is a rare, but a life-threatening event. We report a case of mixed-type AIHA that developed in a child after hepatocyte and living-related orthotopic liver transplantation for factor VII deficiency.

The effect of rituximab on humoral and cell mediated immunity and infection in the treatment of autoimmune diseases

Depletion of B lymphocytes using the anti-CD20 monoclonal antibody rituximab has wide-spread use in the treatment of patients with autoimmune disorders. As haematopoietic progenitor cells and only a fraction of differentiated plasma express CD20, the effect of rituximab on immune function appears to be minimal. However, hypogammagobulinaemia can occur with repeated doses and emerging data from large studies suggest a subtle increase in the risk of infection. Reactivation of latent JC virus, resulting in progressive multifocal leucoencephalopathy, and hepatitis B virus, resulting in hepatoxicity, have been documented in patients receiving rituximab; although confounding effects of concomitant immunosuppressive therapies and immune dysregulation due to the underlying disease make causal associations of infections problematic. This review discusses the efficacy of B cell depletion therapy in the treatment of autoimmune diseases, the effect of B cell depletion on infection and immunity including the role of the B cell in autoimmunity, and identifies areas of controversy.

Cytomegalovirus infection following renal transplantation in patients administered low-dose rituximab induction therapy

Anti-CD20 antibody (rituximab) is recently being used as a B cell-depleting agent in renal transplantation (RTx). However, the incidence of infectious complications associated with rituximab therapy remains uncertain. We evaluated the incidence of cytomegalovirus (CMV) infection associated with rituximab therapy in RTx. A total of 83 patients were enrolled. The immunosuppressive regimen consisted of tacrolimus or cyclosporin, mycophenolate mofetil, methylprednisolone and basiliximab. In 54 patients, only one dose of rituximab (200 or 500 mg/kg body weight) was given before RTx. A total of 25 of 43 (58.1%) recipients who were CMV seropositive prior to RTx and who received rituximab induction therapy developed CMV infection, compared to 18 of 24 (75%) CMV seropositive recipients who did not receive rituximab therapy (P = 0.1676). A total of 8 of 11 patients who were CMV seronegative prior to RTx and who received rituximab developed CMV infection. However, CMV seroconversion was seen in all 8 of these infected patients. Low-dose rituximab induction therapy in renal transplant recipients appears to have no influence on the incidence of CMV infection and CMV seroconversion. However, we have to consider anti-CMV prophylaxis therapy, because of high incidents of CMV infection, especially for CMV seronegative recipients who received rituximab.

Targeting CD70 for human therapeutic use

Expression of CD70, a member of the tumor necrosis factor superfamily, is restricted to activated T-and B-lymphocytes and mature dendritic cells. Binding of CD70 to its receptor, CD27, is important in priming, effector functions, differentiation and memory formation of T-cells as well as plasma and memory B-cell generation. Antibody blockade of CD70-CD27 interaction inhibits the onset of experimental autoimmune encephalomyelits and cardiac allograft rejection in mice. CD70 has been also detected on hematological tumors and on carcinomas. The highly restricted expression pattern of CD70 in normal tissues and its widespread expression in various malignancies as well as its potential role in autoimmune and inflammatory conditions makes it an attractive target for antibody-based therapeutics. This chapter provides an overview of the physiological role of CD70-CD27 interactions and discusses various approaches to target this pathway for therapeutic use in cancers and autoimmunity.

Late onset neutropenia and immunoglobulin suppression of the patients with malignant lymphoma following autologous stem cell transplantation with rituximab

BACKGROUND

Recently, decrease of immunoglobulin concentrations or neutrophil counts were reported in some cases several months after administration of rituximab. We examined a number of episodes of late onset neutropenia or immunoglobulin decrease in patients with malignant lymphoma who were in complete remission following autologous transplantation with or without rituximab.

METHOD

Patients with follicular lymphoma and diffuse large B cell lymphoma transplanted with or without rituximab in our institutes were analyzed. Immunoglobulin concentrations and neutrophil counts after transplantation, both with and without rituximab were measured serially.

RESULTS

Four weeks after transplantation, blood samples revealed lower concentrations of IgG and IgA in the rituximab group than in the non-rituximab group. Neutrophil numbers did not fall below 0.5x10(9) /L four weeks or more after transplantation in the non-rituximab group. Neutrophil numbers dropped below 0.5x10(9) /L in 6 of 14 cases in the rituximab group.

CONCLUSION

Although the present study was retrospective and disease composition and pre-transplantation regimens differed between the two groups, the addition of rituximab to autologous transplantation might bring about a decrease of immunoglobulin levels and transient LON.

CD70 as a therapeutic target in human malignancies

BACKGROUND

Expression of CD70, a member of the tumor necrosis factor superfamily, is restricted to activated T and B lymphocytes and mature dendritic cells. CD70 has also been detected on hematological tumors and on carcinomas. The restricted expression pattern of CD70 in normal tissues and its widespread expression in various malignancies makes it an attractive target for antibody-based therapeutics. Investigations to exploit CD70 as a cancer target have lead to the identification of potential antibody-based clinical candidates. Anti-CD70 antibodies for therapeutic use have been developed and used to validate CD70 as a target for cancers. Antibodies are also used as a vehicle to deliver potent cytotoxic drugs to target CD70+ malignant cells. Both unconjugated antibodies and antibody-drug conjugates targeting CD70 have been tested in animal models of human cancers.

OBJECTIVE

To describe the expression of CD70 in cancer cells and the development of antibody-based therapies against CD70.

METHODS

A review of the available literature.

RESULTS/CONCLUSIONS

Humanized anti-CD70 antibodies have shown significant antitumor activity in preclinical xenograft models of cancer. Additionally, anti-CD70 antibody-drug conjugates exhibit potent antitumor activity in solid tumor xenograft models, confirming increased therapeutic efficacy through cytotoxic drug delivery. Thus, preclinical animal models have provided strong evidence that targeting CD70 either with unconjugated antibodies or with antibody-drug conjugates represents a promising approach to treat human malignancies.

Delayed redistribution of CD27, CD40 and CD80 positive B cells and the impaired in vitro immunoglobulin production in patients with non-Hodgkin lymphoma after rituximab treatment as an adjuvant to autologous stem cell transplantation

Recent studies have indicated that patients who received rituximab as an adjuvant to stem cell transplantation (SCT) demonstrated an increased risk of developing severe hypogammaglobulinaemia, which was found to be a result of delayed recovery of CD27 positive memory B cells and impaired isotype expression. It appears that rituximab influences both the quantity and quality of B-cell redistribution. Precisely how the B-cell repertoire regenerates after anti-CD20-mediated transient B-cell depletion in patients with non-Hodgkin lymphoma (NHL) remains to be elucidated. This study performed a phenotypical analysis of B cells in 17 NHL patients who received rituximab as an adjuvant to autologous SCT. The median period after final administration of rituximab was 36 months (range, 12-43 months). Surface antigen expression of CD27, CD40 and CD80 in NHL patients was statistically significantly different from healthy controls (n = 14). Moreover, B cells from NHL patients showed significantly impaired IgG and IgA production upon engagement of surface immunoglobulin receptors in the presence of interleukin (IL)-2, IL-10 and CD40 ligand in comparison with samples from healthy controls. The delayed recovery of memory B cells with an abnormal cell marker expression and function demonstrates that naive B cells may fail to differentiate into plasma cells, resulting in hypogammaglobulinaemia after autologous SCT and rituximab therapy.

Engineered anti-CD70 antibody with multiple effector functions exhibits in vitro and in vivo antitumor activities

Antigens expressed on malignant cells in the absence of significant expression on normal tissues are highly desirable targets for therapeutic antibodies. CD70 is a TNF superfamily member whose normal expression is highly restricted but is aberrantly expressed in hematologic malignancies including non-Hodgkin lymphoma (NHL), Hodgkin disease, and multiple myeloma. In addition, solid tumors such as renal cell carcinoma, nasopharyngeal carcinoma, thymic carcinoma, meduloblastoma, and glioblastoma express high levels of this antigen. To functionally target CD70-expressing cancers, a murine anti-CD70 monoclonal antibody was engineered to contain human IgG1 constant domains. The engineered antibody retained the binding specificity of the murine parent monoclonal antibody and was shown to induce Fc-mediated effector functions including antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and antibody-dependent cellular phagocytosis in vitro. Further, administration of this antibody significantly prolonged survival of severe combined immunodeficient (SCID) mice bearing CD70+ disseminated human NHL xenografts. Survival of these mice was dependent upon the activity of resident effector cells including neutrophils, macrophages, and natural killer (NK) cells. These data suggest that an anti-CD70 antibody, when engineered to contain human IgG1 constant domains, possesses effector cell–mediated antitumor activity and has potential utility for anticancer therapy.

The emerging role of rituximab in organ transplantation

Long-term acceptance of solid organ allografts remains a challenge. While many acute rejection episodes can be treated, new mechanisms of allograft damage are now being defined especially in kidney transplantation. Unexpected clusters of CD20(+) cells have been discovered in renal biopsies performed for clinical rejection. C4d deposition is now routinely seen in refractory rejection. Despite the rapid introduction of new immunosuppressive agents in transplantation, the search for an efficacious anti-B-cell agent remains. With novel mechanisms of allograft damage now being defined, it is important to consider how an anti-B-cell agent might fit into an immunosuppressive regimen. Rituximab is a high-affinity CD20 specific antibody that depletes the B-cell compartment by inducing cellular apoptosis. Thus, it is a rational choice for therapy in transplantation to abrogate B-cell mediated events. In this review, we will discuss the mechanisms of action of rituximab, and its use in for a variety of indications in solid organ transplantation. There are emerging case reports that show that rituximab may be an effective agent to treat antibody-mediated rejection, and post-transplant lymphoproliferative disorder. Rituximab has been frequently cited as an important adjunct therapy in desensitization protocols for highly sensitized transplant recipients as well as recipients of ABO incompatible transplants. Rituximab demonstrates promise in this regard and warrants additional consideration in prospective clinical trials.

Hypogammaglobulinemia with a selective delayed recovery in memory B cells and an impaired isotype expression after rituximab administration as an adjuvant to autologous stem cell transplantation for non-Hodgkin lymphoma

OBJECTIVES

Some studies have indicated patients who received rituximab as adjuvant to stem cell transplantation had an increased risk of developing severe hypogammaglobulinemia. The mechanism of this hypogammaglobulinemia is unknown, although investigators have hypothesized a further delay in the B-cell recovery as one potential etiology. The aim of this study is to clarify the mechanism(s) of this hypogammaglobulinemia.

METHODS

A total of 14 patients with high-risk CD20+ lymphoma underwent an autologous peripheral blood stem cell transplantation (APBSCT). After a hematological recovery, rituximab was given weekly for up to four doses as an adjuvant therapy.

RESULTS

After a median follow up of 33.5 months, we found six patients (group A) who had hypogammaglobulinemia, while the eight other patients (group B) had normal serum immunoglobulin levels. A phenotypical analysis revealed that group A patients had already achieved B-cell recovery. However, we found a severe delay in the recovery of CD27+ memory B cells, especially in the IgD-/CD27+ switched populations in group A, but CD27 negative naive B-cells reverted to a normal range in both groups. Consistent with this, reverse transcriptase-polymerase chain reaction studies with peripheral blood mononuclear cells revealed that most patients in group A lacked more than two classes of isotype transcripts.

CONCLUSIONS

Abnormal repertoires and impaired isotype expression are seen in patients with common variable immunodeficiency, these data suggested that rituximab after APBSCT can affect not only the B-cell quantities, but also the recovery of the B-cell repertoires.