Pathobiology of ischaemic stroke: an integrated view

This review is directed at understanding how neuronal death occurs in two distinct insults, global ischemia and focal ischemia. These are the two principal rodent models for human disease. Cell dea...

Ischemic Cell Death in Brain Neurons

The neonatal Fc receptor for IgG (FcRn) has been well characterized in the transfer of passive humoral immunity from a mother to her fetus. In addition, throughout life, FcRn protects IgG from degradation, thereby explaining the long half-life of this class of antibody in the serum. In recent years, it has become clear that FcRn is expressed in various sites in adults, where its potential function is now beginning to emerge. In addition, recent studies have examined the interaction between FcRn and the Fc portion of IgG with the aim of either improving the serum half-life of therapeutic monoclonal antibodies or reducing the half-life of pathogenic antibodies. This Review summarizes these two areas of FcRn biology.

FcRn: the neonatal Fc receptor comes of age

Immunoglobulins are heterodimeric proteins composed of 2 heavy and 2 light chains. They can be separated functionally into variable domains that bind antigens and constant domains that specify effector functions, such as activation of complement or binding to Fc receptors. The variable domains are created by means of a complex series of gene rearrangement events and can then be subjected to somatic hypermutation after exposure to antigen to allow affinity maturation. Each variable domain can be split into 3 regions of sequence variability termed the complementarity-determining regions (CDRs) and 4 regions of relatively constant sequence termed the framework regions. The 3 CDRs of the heavy chain are paired with the 3 CDRs of the light chain to form the antigen-binding site, as classically defined. The constant domains of the heavy chain can be switched to allow altered effector function while maintaining antigen specificity. There are 5 main classes of heavy chain constant domains. Each class defines the IgM, IgG, IgA, IgD, and IgE isotypes. IgG can be split into 4 subclasses, IgG1, IgG2, IgG3, and IgG4, each with its own biologic properties, and IgA can similarly be split into IgA1 and IgA2.

Structure and function of immunoglobulins.

Antibodies constitute the most rapidly growing class of human therapeutics and the second largest class of drugs after vaccines. The generation of potent antibody therapeutics, which I review here, is an iterative design process that involves the generation and optimization of antibodies to improve their clinical potential.

Potent antibody therapeutics by design

Purpose: We generated a humanized antibody, HuLuc63, which specifically targets CS1 (CCND3 subset 1, CRACC, and SLAMF7), a cell surface glycoprotein not previously associated with multiple myeloma. To explore the therapeutic potential of HuLuc63 in multiple myeloma, we examined in detail the expression profile of CS1, the binding properties of HuLuc63 to normal and malignant cells, and the antimyeloma activity of HuLuc63 in preclinical models.

Experimental Design: CS1 was analyzed by gene expression profiling and immunohistochemistry of multiple myeloma samples and numerous normal tissues. HuLuc63-mediated antimyeloma activity was tested in vitro in antibody-dependent cellular cytotoxicity (ADCC) assays and in vivo using the human OPM2 xenograft model in mice.

Results: CS1 mRNA was expressed in >90% of 532 multiple myeloma cases, regardless of cytogenetic abnormalities. Anti-CS1 antibody staining of tissues showed strong staining of myeloma cells in all plasmacytomas and bone marrow biopsies. Flow cytometric analysis of patient samples using HuLuc63 showed specific staining of CD138+ myeloma cells, natural killer (NK), NK-like T cells, and CD8+ T cells, with no binding detected on hematopoietic CD34+ stem cells. HuLuc63 exhibited significant in vitro ADCC using primary myeloma cells as targets and both allogeneic and autologous NK cells as effectors. HuLuc63 exerted significant in vivo antitumor activity, which depended on efficient Fc-CD16 interaction as well as the presence of NK cells in the mice.

Conclusions: These results suggest that HuLuc63 eliminates myeloma cells, at least in part, via NK-mediated ADCC and shows the therapeutic potential of targeting CS1 with HuLuc63 for the treatment of multiple myeloma.

https://clincancerres.aacrjournals.org/content/clincanres/14/9/2775.full.pdf

CS1, a Potential New Therapeutic Antibody Target for the Treatment of Multiple Myeloma

Engineered human IgG antibodies with longer serum half-lives in primates

The serum half-life of IgG Abs is regulated by the neonatal Fc receptor (FcRn). By binding to FcRn in endosomes, IgG Abs are salvaged from lysosomal degradation and recycled to the circulation. Several studies have demonstrated a correlation between the binding affinity of IgG Abs to FcRn and their serum half-lives in mice, including engineered Ab fragments with longer serum half-lives. Our recent study extended this correlation to human IgG2 Ab variants in primates. In the current study, several human IgG1 mutants with increased binding affinity to human FcRn at pH 6.0 were generated that retained pH-dependent release. A pharmacokinetics study in rhesus monkeys of one of the IgG1 variants indicated that its serum half-life was ∼2.5-fold longer than the wild-type Ab. Ag binding was unaffected by the Fc mutations, while several effector functions appeared to be minimally altered. These properties suggest that engineered Abs with longer serum half-lives may prove to be effective therapeutics in humans.

An engineered human IgG1 antibody with longer serum half-life.

The invention provides humanized immunoglobulins that bind to and neutralize γ-interferon. The antibodies are useful for treatment of diseases of the immune system, particularly autoimmune diseases.

Humanized antibodies to gamma-interferon

Background and Purpose E-selectin participates in leukocyte-endothelial adhesion and the inflammatory processes that follow focal cerebral ischemia and reperfusion. The temporal and topographical patterns of microvascular E-selectin presentation after experimental focal cerebral ischemia are relevant to microvascular reactivity to ischemia. Methods The upregulation and fate of E-selectin antigen during 2 hours of middle cerebral artery occlusion (n=4) and 3 hours of occlusion with reperfusion (1 hour, n=4; 4 hours, n=6; 24 hours, n=6) were evaluated in the nonhuman primate. E-selectin and E:P-selectin immunoreactivities were semiquantitated with the use of computerized light microscopy video imaging and laser confocal microscopy. Results Three patterns of microvascular E-selectin expression, defined by the antibody E-1E4, were confirmed by complete elimination of E-1E4 binding after incubation with soluble recombinant human E-selectin: (1) Low immunoperoxidase intensity was observed in ischemic microvesse...

Naoya Tsurushita

Papers

CS1, a Potential New Therapeutic Antibody Target for the Treatment of Multiple Myeloma

Engineered human IgG antibodies with longer serum half-lives in primates

An engineered human IgG1 antibody with longer serum half-life.

Humanized antibodies to gamma-interferon

E-Selectin Appears in Nonischemic Tissue During Experimental Focal Cerebral Ischemia