CD40 stimulation promotes human secondary immunoglobulin responses in HuPBL-SCID chimeras

Characteristics and clinical trial results of agonistic anti-CD40 antibodies in the treatment of malignancies

Cluster of differentiation 40 (CD40) mediates many immune activities. Preclinical studies have shown that activation of CD40 can evoke massive antineoplastic effects in several tumour models in vivo, providing a rationale for using CD40 agonists in cancer immunotherapy. To date, several potential agonistic antibodies that target CD40 have been investigated in clinical trials. Early clinical trials have shown that the adverse events associated with agonists of CD40 thus far have been largely transient and clinically controllable, including storms of cytokine release, hepatotoxicity and thromboembolic events. An antitumour effect of targeting CD40 for monotherapy or combination therapy has been observed in some tumours. However, these antitumour effects have been moderate. The present review aimed to provide updated details of the clinical results of these agonists, and offer information to further investigate the strategies of combining CD40 activation with chemotherapy, radiotherapy, targeted therapy and immunomodulators. Furthermore, biomarkers should be identified for monitoring and predicting responses and informing resistance mechanisms.

The Use of Anti-CD40 mAb in Cancer

Immunomodulatory monoclonal antibody (mAb) therapy is at the forefront of developing cancer therapeutics with numerous targeted agents proving highly effective in selective patients at stimulating protective host immunity, capable of eradicating established tumours and leading to long-term disease-free states. The cell surface marker CD40 is expressed on a range of immune cells and transformed cells in malignant states whose signalling plays a critical role in modulating adaptive immune responses. Anti-CD40 mAb therapy acts via multiple mechanisms to stimulate anti-tumour immunity across a broad range of lymphoid and solid malignancies. A wealth of preclinical research in this field has led to the successful development of multiple anti-CD40 mAb agents that have shown promise in early-phase clinical trials. Significant progress has been made to enhance the engagement of antibodies with immune effectors through their interactions with Fcγ receptors (FcγRs) by the process of Fc engineering. As more is understood about how to best optimise these agents, principally through the fine-tuning of mAb structure and choice of synergistic partnerships, our ability to generate robust, clinically beneficial anti-tumour activity will form the foundation for the next generation of cancer therapeutics.

Humanized SCID mouse models for biomedical research

There is a growing need for effective animal models to carry out experimental studies on human hematopoietic and immune systems without putting individuals at risk. Progress in development of small animal models for the in vivo investigation of human hematopoiesis and immunity has seen three major breakthroughs over the last three decades. First, CB 17-Prkdc(scid) (abbreviated CB 17-scid) mice were discovered in 1983, and engraftment of these mice with human fetal tissues (SCID-Hu model) and peripheral blood mononuclear cells (Hu-PBL-SCID model) was reported in 1988. Second, NOD-scid mice were developed and their enhanced ability to engraft with human hematolymphoid tissues as compared with CB17-scid mice was reported in 1995. NOD-scid mice have been the "gold standard" for studies of human hematolymphoid engraftment in small animal models over the last 10 years. Third, immunodeficient mice bearing a targeted mutation in the IL-2 receptor common gamma chain (IL2rgamma(null)) were developed independently by four groups between 2002 and 2005, and a major increase in the engraftment and function of human hematolymphoid cells as compared with NOD-scid mice has been reported. These new strains of immunodeficient IL2rgamma(null) mice are now being used for studies in human hematopoiesis, innate and adaptive immunity, autoimmunity, infectious diseases, cancer biology, and regenerative medicine. In this chapter, we discuss the current state of development of these strains of mice, the remaining deficiencies, and how approaches used to increase the engraftment and function of human hematolymphoid cells in CB 17-scid mice and in previous models based on NOD-scid mice may enhance human hematolymphoid engraftment and function in NOD-scid IL2rgamma(null) mice.

Human interleukin-15 improves engraftment of human T cells in NOD-SCID mice

Human nonobese diabetic-severe combined immune deficiency (NOD-SCID) mouse chimeras have been widely used as an in vivo model to assess human immune function. However, only a small fraction of transferred human T lymphocytes can be detected in human peripheral blood lymphocyte (huPBL)-NOD-SCID chimeras. To improve the reconstitution of human T lymphocytes in NOD-SCID mice, the use of recombinant human interleukin-15 (rhIL-15) as a stimulator of human lymphocytes was explored. Administration of rhIL-15 after transplantation of huPBLs into NOD-SCID mice increased reconstitution of human T lymphocytes in a dose-dependent manner, with an optimal dosage of 1 microg/mouse. The number of human T lymphocytes (HLA-ABC+ CD3+) in the lymphoid organs or tissue of rhIL-15-treated huPBL-NOD-SCID mice increased 11- to 80-fold, and phytohemagglutinin-induced T-lymphocyte proliferation and cytokine production were significantly enhanced. Additionally, although mature human cells have not been thought to enter the murine thymus, human T lymphocytes were detected in the huPBL-NOD-SCID thymus after rhIL-15 treatment. Thus, rhIL-15 can be used to optimize long-term peripheral T-cell engraftment in these human-mouse chimeras and may also be useful in clinical treatment of T-cell deficiencies.

Alloimmune injury and rejection of human skin grafts on human peripheral blood lymphocyte-reconstituted non-obese diabetic severe combined immunodeficient beta2-microglobulin-null mice

Small animal models with the capacity to support engraftment of a functional human immune system are needed to facilitate studies of human alloimmunity. In the present investigation, non-obese diabetic (NOD) severe combined immunodeficient (scid) beta2-microglobulin-null (B2mnull) mice engrafted with human peripheral blood lymphocytes (hu-PBL-NOD-scid B2mnull mice) were used as in vivo models for studying human skin allograft rejection. Hu-PBL-NOD-scid B2mnull mice were established by injection of human spleen cells or PBLs and transplanted with full-thickness allogeneic human skin. Human cell engraftment was enhanced by injection of anti-mouse CD122 antibody. The respective contributions of human CD4+ and CD8+ cells in allograft rejection were determined using depleting antibodies. Human skin grafts on unmanipulated NOD-scid B2mnull mice uniformly survived but on chimeric hu-PBL-NOD-scid B2mnull mice exhibited severe immune-mediated injury that often progressed to complete rejection. The alloaggressive hu-PBLs did not require prior in vitro sensitization to elicit targeted effector cell activity. Extensive mononuclear cell infiltration directed towards human-origin endothelium was associated with thrombosis and fibrin necrosis. No evidence of graft-versus-host disease was detected. Either CD4+ or CD8+ T cells may mediate injury and alloimmune rejection of human skin grafts on hu-PBL-NOD-scid B2mnull mice. It is proposed that Hu-PBL-NOD-scid B2mnull mice engrafted with human skin will provide a useful model for analysis of interventions designed to modulate human allograft rejection.