Expression, purification and characterization of recombinant interleukin-21

Cytokines and their role as immunotherapeutics and vaccine Adjuvants: The emerging concepts

Cytokines are a protein family comprising interleukins, lymphokines, chemokines, monokines and interferons. They are significant constituents of the immune system, and they act in accordance with specific cytokine inhibiting compounds and receptors for the regulation of immune responses. Cytokine studies have resulted in the establishment of newer therapies which are being utilized for the treatment of several malignant diseases. The advancement of these therapies has occurred from two distinct strategies. The first strategy involves administrating the recombinant and purified cytokines, and the second strategy involves administrating the therapeutics which inhibits harmful effects of endogenous and overexpressed cytokines. Colony stimulating factors and interferons are two exemplary therapeutics of cytokines. An important effect of cytokine receptor antagonist is that they can serve as anti-inflammatory agents by altering the treatments of inflammation disorder, therefore inhibiting the effects of tumour necrosis factor. In this article, we have highlighted the research behind the establishment of cytokines as therapeutics and vaccine adjuvants, their role of immunotolerance, and their limitations.

Targeting IL-21 to tumor-reactive T cells enhances memory T cell responses and anti-PD-1 antibody therapy

T cell rejuvenation by PD-1/PD-L1 blockade, despite emerging as a highly promising therapy for advanced cancers, is only beneficial for a minority of treated patients. There is evidence that a lack of efficient T cell activation may be responsible for the failure. Here, we demonstrate that IL-21 can be targeted to tumor-reactive T cells by fusion of IL-21 to anti-PD-1 antibody. To our surprise, the fusion protein PD-1Ab21 promotes the generation of memory stem T cells (T_SCM) with enhanced cell proliferation. PD-1Ab21 treatment show potent antitumor effects in established tumor-bearing mice accompanied with an increased frequency of T_SCM and robust expansion of tumor-specific CD8⁺ T cells with a memory phenotype, and is superior to a combination of PD-1 blockade and IL-21 infusion. Therefore, we have developed a potential strategy to improve the therapeutic effects of immune checkpoint blockade by simultaneously targeting cytokines to tumor-reactive T cells.

IL-21 restricts T follicular regulatory T cell proliferation through Bcl-6 mediated inhibition of responsiveness to IL-2

T follicular regulatory (Tfr) cells control the magnitude and specificity of the germinal centre reaction, but how regulation is contained to ensure generation of high-affinity antibody is unknown. Here we show that this balance is maintained by the reciprocal influence of interleukin (IL)-2 and IL-21. The number of IL-2-dependent FoxP3+ regulatory T cells is increased in the peripheral blood of human patients with loss-of-function mutations in the IL-21 receptor (IL-21R). In mice, IL-21:IL-21R interactions influence the phenotype of T follicular cells, reducing the expression of CXCR4 and inhibiting the expansion of Tfr cells after T-cell-dependent immunization. The negative effect of IL-21 on Tfr cells in mice is cell intrinsic and associated with decreased expression of the high affinity IL-2 receptor (CD25). Bcl-6, expressed in abundance in Tfr cells, inhibits CD25 expression and IL-21-mediated inhibition of CD25 is Bcl-6 dependent. These findings identify a mechanism by which IL-21 reinforces humoral immunity by restricting Tfr cell proliferation.

Stability engineering of the human antibody repertoire

Human monoclonal antibodies often display limited thermodynamic and colloidal stabilities. This behavior hinders their production, and places limitations on the development of novel formulation conditions and therapeutic applications. Antibodies are highly diverse molecules, with much of the sequence variation observed within variable domain families and, in particular, their complementarity determining regions. This has complicated the development of comprehensive strategies for the stability engineering of the human antibody repertoire. Here we provide an overview of the field, and discuss recent advances in the development of robust and aggregation resistant antibody therapeutics.

Efficient production of recombinant IL-21 proteins for pre-clinical studies by a two-step dilution refolding method

Produced by CD4(+) helper T cells and natural killer T (NKT) cells, interleukin-21 (IL-21) performs broad regulatory functions on B cells, CD4(+) T cells, CD8(+) T cells, NK cells and NKT cells. Targeting IL-21 to enhance the immune system has attracted great interests in the development of vaccination, anti-infection and anti-tumor therapies. Administration of IL-21 in pre-clinical models is however limited by relatively high expense of the recombinant IL-21 protein. Here, we report a rapid and cost-effective method to produce IL-21 using Escherichia coli (E. coli) by introducing a novel two-step dilution strategy for refolding. The method has been validated to produce milligrams of human IL-21, human IL-21/IL-4 chimera and mouse IL-21 with high bioactivities and low endotoxin, mostly suitable for in vitro and in vivo pre-clinical studies.