Functional comparison of recombinant interleukin 2 (IL-2) with IL-2-containing preparations derived from cultured cells

Advancing Biologic Therapy for Refractory Autoimmune Hepatitis

Biologic agents may satisfy an unmet clinical need for treatment of refractory autoimmune hepatitis. The goals of this review are to present the types and results of biologic therapy for refractory autoimmune hepatitis, indicate opportunities to improve and expand biologic treatment, and encourage comparative clinical trials. English abstracts were identified in PubMed by multiple search terms. Full-length articles were selected for review, and secondary and tertiary bibliographies were developed. Rituximab (monoclonal antibodies against CD20 on B cells), infliximab (monoclonal antibodies against tumor necrosis factor-alpha), low-dose recombinant interleukin 2 (regulatory T cell promoter), and belimumab (monoclonal antibodies against B cell activating factor) have induced laboratory improvement in small cohorts with refractory autoimmune hepatitis. Ianalumab (monoclonal antibodies against the receptor for B cell activating factor) is in clinical trial. These agents target critical pathogenic pathways, but they may also have serious side effects. Blockade of the B cell activating factor or its receptors may disrupt pivotal B and T cell responses, and recombinant interleukin 2 complexed with certain interleukin 2 antibodies may selectively expand the regulatory T cell population. A proliferation-inducing ligand that enhances T cell proliferation and survival is an unevaluated, potentially pivotal, therapeutic target. Fully human antibodies, expanded target options, improved targeting precision, more effective delivery systems, and biosimilar agents promise to improve efficacy, safety, and accessibility. In conclusion, biologic agents target key pathogenic pathways in autoimmune hepatitis, and early experiences in refractory disease encourage clarification of the preferred target, rigorous clinical trial, and comparative evaluations.

A convenient method for hTfR1 inclusion body purification

Human transferrin receptor, referred as hTfR1, is ubiquitously expressed at low levels in most normal human tissues; however, the expression level of hTfR1 at the blood-brain barrier (BBB) and in tumor tissues is relatively higher. hTfR1 is a type II homodimeric transmembrane protein. The extracellular domain of hTfR1 consists of three domains: helical domain, apical, and protease-like domain. In order to prepare hTfR1 antibody, which can be utilized to deliver drugs across BBB through receptor-mediated endocytosis, we began to express the nonligand binding domain of hTfR1 in Escherichia coli BL21 Transetta (DE3). The TfR1 gene was first obtained from HepG2 cells by reverse-transcription polymerase chain reaction (RT-PCR) and then inserted into pET 32a(c+) vector. The protein was expressed in the form of inclusion body with extremely high purity by the E. coli BL21 Transetta (DE3), and the purity was further improved by size-exclusion chromatography. The Western blot test indicated that the recombinant protein was TfR1 as expected. Above all, this report provided a convenient protocol that could be fulfilled in order to prepare hTfR1 inclusion body, which failed to be purified by an Ni(2+) affinity column.

Biotechnological applications of bacterial protein secretion: from therapeutics to biofuel production

Recent years have witnessed significant progresses in engineering of recombinant protein secretion. The relatively simple secretion mechanisms, Type I and Type V (autotransporters), are increasingly used for secretion of recombinant proteins. The secretion level of target proteins varied from milligrams to grams per liter. The range of proteins was significantly expanded beyond medical application. Notable additions include biofuel productions from renewable feedstock. Despite the progress, almost all successes in the engineering efforts come with significant trials and errors, highlighting the need for a better understanding of secretion systems and rational based methods.

Engineering of therapeutic proteins production in Escherichia coli

Low cost and simplicity of cultivating bacteria make the E. coli expression system a preferable choice for production of therapeutic proteins both on a lab scale and in industry. In addition straightforward recombinant DNA technology offers engineering tools to produce protein molecules with modified features. The lack of posttranslational modification mechanisms in bacterial cells such as glycosylation, proteolytic protein maturation or limited capacity for formation of disulfide bridges may, to a certain extent, be overcome with protein engineering. Protein engineering is also often employed to improve protein stability or to modulate its biological action. More sophisticated modifications may be achieved by genetic fusions of two proteins. This article presents a variety of examples of genetic engineering of therapeutic proteins. It emphasizes the importance of designing a construct without any unnecessary amino acid residues.

A novel, cheap and effective fusion expression system for the production of recombinant proteins

To develop faster, less expensive methods for expression and purification of proteins, the annexin B1-intein fusion expression system was constructed. The interest proteins fused to the annexin B1-intein tag were purified in a single-step method based on the Ca(2+)-binding activity of annexin B1, and the annexin B1-intein fusion tag was removed based on the self-cleaving activity of the intein. Moreover, we found that in some cases, fusion to annexin B1 can promote the solubility of heterologous proteins. The production of soluble and highly active of interleukin-2 and low-molecular single-chain urokinase in our results proved that the system was a novel, cheap and effective fusion expression system for the production of valuable soluble recombinant proteins in Escherichia coli.

Immunochemical characterization of antigenic domains on human IL-2: Spatially distinct epitopes are associated with binding to the p55 and p70 subunits of IL-2 receptor

We have isolated and characterized 8 mAb against human rIL-2. All recognize nonglycosylated rIL-2 in liquid phase with similar affinities (Kd approximately 1 nM). Based on the epitopes of the IL-2 molecule that they recognize and their pattern of reactivity against glycosylated and non-glycosylated IL-2, they have been classified into four groups. The first group of anti-IL-2 mAb (2C4, 19B11 and 12C2) inhibits IL-2 binding to p70 IL-2R, while the second one (16F11, 18E1 and 2A4) prevents its binding to p55 IL-2R. These two groups neutralize IL-2 activity in a T cell proliferation assay equally well, due to their similar inhibition of IL-2 binding to high affinity IL-2R. Two mAb, 3H9 and 17F4, recognize separate epitopes on IL-2 molecule, are poor inhibitors of IL-2 binding, and they are inefficient in the neutralization of its biological activity; they have been assigned to the third and fourth groups, respectively. These results show that mAb from the first and second group recognize two epitopes of the human IL-2 molecule which probably overlap the p70 IL-2R and p55 IL-2R binding sites, respectively. In addition, these areas together form the high affinity IL-2R binding site. The two mAb from the third and fourth group recognized epitopes of IL-2 not directly involved in IL-2 binding to its receptor. All eight mAb anti-human IL-2 recognize murine IL-2 and with the exception of one, 17F4 mAb are also able to neutralize it in a T cell proliferation assay. The relationship between the structure and the function of the IL-2 molecule is discussed.

Comparison between crude interleukin-2 and recombinant interleukin-2 in maintaining killing activity of cultured lymphocytes

Peripheral blood lymphocytes, regional lymph node lymphocytes or malignant effusion lymphocytes from cancer patients were incubated with crude IL-2 (cIL-2) for 13 days. These effectors, which frequently expressed IL-2 receptor (IL-2R), proliferated well and possessed augmented killing activity against fresh autologous tumor cells and K562. However, when recombinant IL-2 (rIL-2) was added for the last 4 days of culture instead of cIL-2, IL-2R expression and killing activity against fresh autologous tumor cells decreased significantly (P less than 0.05). Phenotypic analysis indicated that cIL-2 significantly promoted the expansion of the cytotoxic population (CD8+.11b-)(P less than 0.05). The decreases in killing activity and IL-2R expression were restored by 0.004% PHA plus rIL-2, but not in the presence of rIFN-gamma, rIL-1 alpha, rIL-1 beta, rIL-4 or rIL-6. PHA-free cIL-2 maintained killing activity, but not IL-2R expression. We conclude that some factors in cIL-2 and a low dose of PHA-P are necessary for the maintenance of killing activity and IL-2R expression of cultured lymphocytes in the late phase of culture.

Inhibition of pokeweed mitogen-induced Ig secretion by IgG monoclonal antibodies to MHC class I and class II molecules requires binding of the intact antibody

Seven purified IgG monoclonal antibodies reactive with different epitopes on DQw1, DR, HLA-A3 or p85 glycoprotein of human lymphocytes have each been shown to inhibit pokeweed mitogen (PWM)-induced IgG and IgM secretion in a dose-dependent manner. Binding of these antibodies to their target antigens was required for the suppression. Antibodies of IgG1, IgG2 alpha, and IgG2b subclasses were able to inhibit both IgG and IgM secretion in the PWM system. The mechanisms by which two of the monoclonal antibodies (MoAbs)-77.34, specific for the class II antigen DQw1, and GAP A3, specific for the class I antigen HLA-A3-caused inhibition--were analyzed. The suppressive effects of 77.34 and GAP A3 were maximal when added at the initiation of the culture period. No inhibition of IL-2 production or cellular proliferation was detected. Supernatants obtained from inhibited cultures were not themselves suppressive. The F(ab')2 fragments of either 77.34 or GAP A3 failed to influence PWM-Ig secretion, indicating that intact IgG molecules were required. This suggests that the observed inhibition might be mediated via Fc receptors. Together F(ab')2 fragments of either 77.34 or GAP A3 and a control IgG2a protein did not reconstitute the inhibitory effects of intact 77.34 or GAP A3. Suppression, therefore, required intact Fc portions on the same IgG molecules as those that bound to DQw1 or HLA-A3. These studies suggest that populations of IgG molecules that crosslink sufficient numbers of Fc receptors with other cell surface antigens on peripheral blood mononuclear cells (PBMs) during the early stages of B-cell activation can inhibit Ig secretion. Crosslinking of B-cell Fc receptors with SIg has been proposed by others to act as a negative signal for Ig production; our data raise the possibility that crosslinking of FcR with B-cell plasma membrane components other than SIg can also suppress Ig secretion.

Interleukin 2 stimulates heart contractility in the presence of exogenous arachidonate or the calcium ionophore A 23187

An increase in the isometric developed tension (IDT) of isolated rat atria was observed shortly after the addition of human interleukin 2 (IL-2) to the organ preparation with subthreshold concentrations of either arachidonate (AA, 1.98 X 10(-6)M) or the calcium ionophore A 23187 (1.9 X 10(-6)M). Both natural purified IL-2 (nIL-2) and yeast recombinant IL-2 (rIL-2) were active in this experimental system. It was determined that this lymphokine was active at 2 X 10(-11)M, considering as a reference the specific activity of rIL-2. Anti-IL-2 monoclonal antibody (anti-IL-2 MAb) abolished this reaction. Inhibition of atrial phospholipase C activity by nitrocarboxyphenyl N,N-diphenylcarbamate (NCDC, 5 X 10(-6)M) prevented the development of the inotropic positive effect of IL-2 in the presence of either AA or A 23187. The synthetic diacylglyceride 1-oleoyl, 2-acetyl-glycerol (OAG) replaced the IL-2 as stimulatory signal but NCDC had no effect on the reaction. The results suggest that IL-2 can alter the physiologic behaviour of the heart and that its mechanism of action is probably similar to the one proposed for other IL-2 targets (IL-2 receptor-positive T lymphocytes, T cell lines).

The requirements for successful immunotherapy of intraperitoneal cancer using interleukin-2 and lymphokine-activated killer cells

In a significant proportion of patients with gastrointestinal and ovarian malignancy the peritoneal cavity is a prominent site at which surgical treatment fails. Adjuvant treatments directed at this site should be investigated in an attempt to improve survival in patients with these cancers. In the study reported here, a model of intraperitoneal tumor in the mouse was established and shows the effectiveness of lymphokine activated killer (LAK) cells and exogenous interleukin-2 (IL-2) in the control of intraperitoneal tumor. A standard regimen was used to treat seven different tumors in three different mouse strains. In all seven cases a significant reduction in the intraperitoneal tumor mass was observed when LAK cells plus IL-2 were used as immunotherapy. A prolonged survival was also demonstrated in mice with intraperitoneal tumor. The relevance of these observations to patients with cancer was demonstrated in that allogeneic and syngeneic LAK cells were equally effective, LAK cells generated from normal and from tumor-bearing donors showed equal reactivity, and this treatment was successful in the immuno-compromised host. Both IL-2 derived from an IL-2-producing subline of the EL-4 thymoma and recombinant IL-2 were equally effective in the control of intraperitoneal tumor. The local-regional effects of the intraperitoneal administration of IL-2 were demonstrated by high levels of LAK cell cytotoxicity in peritoneal exudate cells. Intraperitoneal IL-2 or IL-2 plus LAK cell regimens should be investigated in the treatment of malignancy that spreads by implantation onto peritoneal surfaces.

Production of and responsiveness to interleukin 2 in autoimmune BXSB mice

BXSB male mice serve as one of several murine models of human systemic lupus erythematosus. T-cell abnormalities in these mice involve decreased production of and responsiveness interleukin 2 (IL-2) and are age-related. The studies presented here investigated the mechanism of these T-cell defects. The results suggest that excessive suppressor-T-cell activity as well as soluble inhibitors of IL-2 production and activity, including PGE, are not responsible for the low levels of IL-2 observed in culture supernatants of Con A-stimulated lymphocytes from "old" (3-6 months) BXSB male mice. Supplementation of Con A-stimulated lymphocyte cultures from BXSB male mice with human IL-1 or normal murine accessory cells did not augment IL-2 production. Reduced proliferative responses were observed in bulk cultures of Con A- or alloantigen-stimulated "old" BXSB male lymphocytes, which were not enhanced by exogenous IL-2. Limiting dilution analysis revealed reduced frequencies of Con A- and alloantigen-inducible IL-2-reactive T cells in these mice. These results suggest intrinsic defects in the ability of T cells from "old" BXSB male mice to be activated to produce and respond to IL-2.