Purification and protective efficacy of monomeric and modified Yersinia pestis capsular F1-V antigen fusion proteins for vaccination against plague

The F1-V vaccine antigen, protective against Yersinia pestis, exhibits a strong tendency to multimerize that affects larger-scale manufacture and characterization. In this work, the sole F1-V cysteine was replaced with serine by site-directed mutagenesis for characterization of F1-V non-covalent multimer interactions and protective potency without participation by disulfide-linkages. F1-V and F1-V(C424S) proteins were overexpressed in Escherichia coli, recovered using mechanical lysis/pH-modulation and purified from urea-solubilized soft inclusion bodies, using successive ion-exchange, ceramic hydroxyapatite, and size-exclusion chromatography. This purification method resulted in up to 2mg/g of cell paste of 95% pure, mono-disperse protein having < or =0.5 endotoxin units per mg by a kinetic chromogenic limulus amoebocyte lysate reactivity assay. Both F1-V and F1-V(C424S) were monomeric at pH 10.0 and progressively self-associated as pH conditions decreased to pH 6.0. Solution additives were screened for their ability to inhibit F1-V self-association at pH 6.5. An L-arginine buffer provided the greatest stabilizing effect. Conversion to >500-kDa multimers occurred between pH 6.0 and 5.0. Conditions for efficient F1-V adsorption to the cGMP-compatible alhydrogel adjuvant were optimized. Side-by-side evaluation for protective potency against subcutaneous plague infection in mice was conducted for F1-V(C424S) monomer; cysteine-capped F1-V monomer; cysteine-capped F1-V multimer; and a F1-V standard reported previously. After a two-dose vaccination with 2 x 20 microg of F1-V, respectively, 100%, 80%, 80%, and 70% of injected mice survived a subcutaneous lethal plague challenge with 10(8) LD(50)Y. pestis CO92. Thus, vaccination with F1-V monomer and multimeric forms resulted in significant, and essentially equivalent, protection.

A phase I study of combination therapy with immunotoxins IgG-HD37-deglycosylated ricin A chain (dgA) and IgG-RFB4-dgA (Combotox) in patients with refractory CD19(+), CD22(+) B cell lymphoma

This study used an 8-day continuous infusion regimen of a 1:1 mixture of two immunotoxins (ITs) prepared from deglycosylated ricin A chain (dgA) conjugated to monoclonal antibodies directed against CD22 (RFB4-dgA) and CD19 (HD37-dgA; Combotox) in a Phase I trial involving 22 patients with refractory B cell lymphoma to determine the maximum tolerated dose, clinical pharmacology, and toxicity profile and to characterize any clinical responses. Adult patients received a continuous infusion of Combotox at 10, 20, or 30 mg/m2/192 h. No intrapatient dose escalation was permitted. Patients with > or =50 circulating tumor cells (CTCs)/mm3 in peripheral blood tolerated all doses without major toxicity. The maximum level of serum IT (Cmax) achieved in this group was 345 ng/ml of RFB4-dgA and 660 ng/ml of HD37-dgA (1005 ng/ml of Combotox). In contrast, patients without CTCs (<50/mm3) had unpredictable clinical courses that included two deaths probably related to the IT. Additionally, patients exhibited a significant potential for association between mortality and a history of either autologous bone marrow or peripheral blood stem cell transplants (P2 = 0.003) and between mortality and a history of radiation therapy (P2 = 0.036). In patients with CTCs, prior therapies appeared to have little impact on toxicity. Subsequent evaluation of the ITs revealed biochemical heterogeneity between two lots of HD37-dgA. In addition, HD37-dgA thawed at the study site tended to contain significant particulates, which were not apparent in matched controls stored at the originating site. This suggests that a tendency to aggregate may have resulted from shipping, storage, and handling of the IT that occurred prior to preparation for administration. It is not clear to what extent, if any, the aggregation of HD37-dgA IT was related to the encountered clinical toxicities; however, the potential to aggregate does suggest one possible basis for problems in our clinical experience with HD37-dgA and leads us to the conclusion that non-aggregate-forming formulations for these ITs should be pursued prior to future clinical trials.

Identification of defensin-1, defensin-2, and CAP37/azurocidin as T-cell chemoattractant proteins released from interleukin-8-stimulated neutrophils

Reports that interleukin-8 (IL-8) induces the infiltration of neutrophils followed by T-cells into injection sites led us to postulate that by stimulation of neutrophil degranulation IL-8 may cause the release of factors with chemoattractant activity for T-lymphocytes. Extracts of human neutrophil granules were chromatographed to isolate and purify T-lymphocyte chemoattractant factors. Two major peaks of T-cell chemotactic activity were purified by C18 reversed phase high pressure liquid chromatography (HPLC). The first peak was resolved further by C4 reversed phase HPLC and yielded an active fraction shown by NH2-terminal amino acid sequence analysis to contain defensins HNP-1, HNP-2, and HNP-3. Purified defensins HNP-1 and HNP-2 (kindly provided by Dr. R. I. Lehrer, UCLA) were also potent chemoattractants for human T-cells, while HNP-3 was inactive. The second peak of T-cell chemoattractant activity was also further purified to homogeneity by C4 reversed phase HPLC and identified by NH2-terminal sequence analysis as CAP37/azurocidin, a protein with sequence homology to serine proteases. 0.1 100 ng of defensins and 1.0 100 ng/ml CAP37 were able to stimulate in vitro T-cell chemotaxis. Neutrophil activating factors, i.e. IL-8, phorbol 12-myristate 13-acetate/ionomycin, and formylmethionylleucylphenylalanine each induced the release of CAP37 and defensins from neutrophil granules. Subcutaneous administration of defensins or CAP37/azurocidin into BALB/c mice resulted in a moderate neutrophil and mononuclear cell infiltrate by 4 h, which was greater by 24 h at the site of injection. Additionally, subcutaneous injection of defensins into chimeric huPBL-SCID mice resulted in significant infiltration by human CD3+ cells within 4 h. These results identify the antimicrobial proteins, CAP37/azurocidin and defensins HNP-1 and HNP-2, as potent neutrophil-derived chemoattractants for T-cells. These proteins represent primordial antimicrobial peptides which may have evolved into acute inflammatory cell-derived signals that mobilize immunocompetent T-cells and other inflammatory cells.

Interleukin-8 receptor beta. The role of the carboxyl terminus in signal transduction

Two interleukin-8 (IL-8) receptors, alpha and beta, have been identified and cloned. Both receptors are thought to transduce signals by coupling to GTP-binding proteins. The aim of this study is to determine whether the carboxyl terminus (C') of IL-8 receptor beta (IL-8R beta) is involved in signaling in response to IL-8. We have constructed a number of IL-8R beta genes that encode truncated forms of the IL-8R beta. The deletions consisted of amino acids 349-355, 336-355, 325-355, and 317-355 (termed beta 2, beta 3, beta 4, and beta 5, respectively). 293 human embryonic kidney cells were transfected with the wild type IL-8R beta (beta 1) and with these mutants. Cells transfected with the mutated receptors expressed the receptors and bound IL-8 with the same high affinity as cells transfected with the wild type receptor. The capacity of the mutated receptors to convey functional signals was evaluated by comparing the chemotaxis index of cells expressing the C'-truncated receptors to the index of cells expressing the wild type receptor. The results indicate that while cells expressing beta 1, beta 2, beta 3, and beta 4 were chemoattracted in response to IL-8, cells expressing beta 5 did not migrate in response to IL-8 stimulation. Therefore, the data suggest that amino acids 317-324 are involved in signaling by IL-8R beta.

Serum amyloid A is a chemoattractant: induction of migration, adhesion, and tissue infiltration of monocytes and polymorphonuclear leukocytes

Serum amyloid A (SAA) is an acute phase protein that in the blood is bound to high density lipoproteins; SAA is secreted mainly by hepatocytes, and its concentration increases in the blood up to 1000 times during an inflammatory response. At present, its biological function is unclear. Since some forms of secondary amyloidosis are caused by deposition in tissues of peptides derived from the SAA and leukocytes seem to be involved in this process, we investigated the effect of human SAA on human monocytes and polymorphonuclear cells (PMN). When recombinant human SAA (rSAA) was used at concentrations corresponding to those found during the acute phase (> 0.8 microM), it induced directional migration of monocytes and polymorphonuclear leukocytes. Preincubation of rSAA with high density lipoproteins blocked this chemoattractant activity for both monocytes and PMN. rSAA also regulated the expression of the adhesion proteins CD11b and leukocyte cell adhesion molecule 1 and induced the adhesion of PMN and monocytes to umbilical cord vein endothelial cell monolayers. When subcutaneously injected into mice, rSAA recruited PMN and monocytes at the injection site. On the basis of these data, we suggest that SAA may participate in enhancing the migration of monocytes and PMN to inflamed tissues during an acute phase response.

Chemokines and serpentines: the molecular biology of chemokine receptors

Chemokines are pro-inflammatory molecules with a diverse array of biological and biochemical functions. These molecules induce the migration of a number of leukocyte subsets including monocytes, neutrophils, and T-cells. The recent cloning of the IL-8, GRO, and MIP-1 alpha chemokine receptors revealed that these glycoproteins belong to the serpentine family of seven transmembrane G-protein-coupled receptors. Other members of this family include the chemotactic receptors for fMLP and C5a, indicating that a common pathway for eliciting the directional migration of leukocytes is probably transduced via G proteins. Ligand binding to chemokine receptors is complex, featured by multiple chemokines binding to a single receptor and multiple receptors binding a specific ligand. Future directions in this field appear to be focused on the cloning of novel receptors and the identification of ligands for orphaned receptors.

Characterization of a tyrosine kinase activity associated with the high-affinity interleukin 2 receptor complex

The IL-2 receptor complex is minimally composed of two genetically unrelated subunits of relative molecular masses 55 and 75 kDa respectively. Structural information deduced from the cDNA sequences of either subunit have not revealed significant information as to the basis of the mechanisms of IL-2 receptor signal transduction. Nevertheless, IL-2 stimulates the activation of one or more tyrosine kinases requiring the functional participation of the p75 member of the receptor complex. Here we have developed the methods to isolate the receptor complex with an associated tyrosine protein kinase. Extracts of membrane glycoproteins from activated normal human T lymphocytes and cell lines demonstrated catalytic activation of tyrosine kinase activity when stimulated with IL-2. Purification of the receptor complex with biotinylated IL-2 revealed the presence of two dominant phosphotyrosyl-proteins of approximate molecular masses 58 and 97 kDa. Denaturation gel electrophoresis followed by renaturation of proteins associated with the IL-2 receptor complex demonstrated that the 97 kDa protein had catalytic autophosphorylation activity. The results indicate that the 58 and 97 kDa phosphotyrosyl-proteins can be found to co-precipitate with the IL-2 receptor complex and that the 97 kDa protein was demonstrated to have protein kinase activity. The association of such kinases with receptors devoid of catalytic structure may represent a unique paradigm of growth-factor receptor mechanisms.

Characterization of a class 3 tyrosine kinase

In an effort to identify unique tyrosine kinases found in human leukemia cell lines, we utilized polymerase chain reaction (PCR) technology and degenerate oligonucleotide primers to produce a cDNA library of kinase catalytic domains found in the human monocytic cell line AML-193. This search yielded a member of the class 3 tyrosine kinases closely related to the murine kinase FD-22. Previous work has identified this kinase as JAK1. This class of tyrosine kinases is characterized by being ubiquitously expressed, lacking both a ligand-binding domain and a SH2 domain, while containing a second domain similar to a degenerate kinase domain. Our studies focused on the further characterization of this class 3 tyrosine kinase using Northern blot analysis to demonstrate an increase in steady-state mRNA by interferon-gamma in human monocytes. A human-hamster somatic cell hybrid panel and linkage mapping was used to assign JAK1 (aml-116) to human chromosome 1.

Cytokines as positive and negative regulators of tumor promotion and progression

Cytokines can have both negative and positive effects on cells undergoing carcinogenesis. The promotion and progression phases of carcinogenesis may be affected by autocrine loops involving cytokines with growth factor activities such as IL-1, IL-2, low molecular weight B cell growth factor, TNF, IL-3, GM-CSF, M-CSF and IL-9. Aberrations in cytokine receptors such as the truncated EGF receptor present in v-erB promotes the growth of neoplastic cells. Aberrant signaling mechanisms, as found with spleen focus-forming virus, which mimics the ligand that activates the erythropoietin receptor, can also contribute to proliferation of preneoplastic and neoplastic cells. In contrast, cytokines such as interferons, LIF, TGF-beta, TNF and leukoregulin, with antiproliferative or differentiating activities, are sometimes capable of inhibiting carcinogenesis. Transfection of tumor cells with cytokine genes, such as IL-2, IL-4 and TNF, can cause suppression of in vivo tumor cell growth by mobilizing host immune and inflammatory cell responses. Thus cytokines and their receptors may play a direct role in early stages of tumor cell development and growth.

Regulation of the interleukin 2 receptor complex tyrosine kinase activity in vitro

Interleukin 2 (IL-2) has been shown to stimulate tyrosine phosphorylation of a number of proteins requiring only the p75 beta chain of the IL-2 receptor. Unlike the receptors for epidermal growth factor, insulin, and other growth factors, the p55-alpha and p75-beta chains of the IL-2 receptor have no tyrosine protein kinase domain suggesting that the IL-2 receptor complex activates protein kinases by a unique mechanism. The activation of tyrosine kinases by IL-2 in situ was studied and using a novel methodology has shown tyrosine kinase activity associated with the purified IL-2R complex in vitro. IL-2 stimulated the in situ tyrosine phosphorylation of 97 kDa and 58 kDa proteins which bound to poly(Glu,Tyr)4:1, a substrate for tyrosine protein kinases, suggesting these proteins had characteristics found in almost all tyrosine kinases. IL-2 was found to stimulate tyrosine protein kinase activity in receptor extracts partially purified from human T lymphocytes and the YT cell line. Biotinylated IL-2 was used to precipitate the high-affinity-receptor complex and phosphoproteins associated with it. The data indicated that the 97-kDa and 58-kDa phosphotyrosyl proteins were tightly associated with the IL-2 receptor complex. These proteins were phosphorylated on tyrosine residues by IL-2 stimulation of intact cells and ligand treatment of in vitro receptor extracts. Furthermore, the 97-kDa and 58-kDa proteins were found in streptavidin-agarose/biotinylated IL-2 purified receptor preparations and showed high affinity for tyrosine kinase substrate support matrixes. The experiments suggest that these two proteins are potential candidates for tyrosine kinases involved in the IL-2R complex signal transduction process.

Clathrin light chains are calcium-binding proteins

Clathrin light chains have been purified to near homogeneity. When analyzed by sodium dodecyl sulfate gel electrophoresis followed by silver stain for proteins, no bands corresponding to light chains were detected. As calmodulin and troponin C are known to behave in the same manner on silver staining, the possibility that clathrin light chains were Ca2+-binding proteins was investigated. Light chains fixed to nitrocellulose filters were found to bind 45Ca2+ in the presence of 5 mM Mg2+. The Ca2+-binding capacity of the light chains was further investigated, using gel filtration and equilibrium dialysis. The light chains were shown to bind, in the presence of 3 mM Mg2+, 1 mol of Ca2+ per mol of light chain with a Kd of 25-55 microM. Nitrocellulose binding and gel filtration studies showed that light chains present in triskelions are still capable of binding Ca2+, in this case with a calculated Kd of 45 microM.

Stimulation of tyrosine phosphorylation of rat brain membrane proteins by calmodulin

Calmodulin stimulates the alkali-resistant phosphorylation of peptides of 50 and 58-60 kDa in rat brain membrane. Phosphoamino acid analysis indicated a calmodulin stimulated increase of phosphotyrosine in these peptides. Calmodulin also stimulated the phosphorylation of these peptides at serine and threonine residues. This suggests the involvement of the calmodulin regulatory system in the effects of tyrosine protein kinases.

Association of adenylate cyclase inhibition by NaF with loss of a factor in rat heart sarcolemma

Heart sarcolemma from different animals was isolated for studying the effect of NaF on membrane-bound adenylate cyclase activity. Unlike dog and rabbit heart, a depression of adenylate cyclase by NaF was observed in sarcolemma from rat heart. There was a progressive attenuation of the NaF ability to stimulate the enzyme at different steps of the sarcolemmal isolation procedure. The activation by epinephrine in the presence of Gpp(NH)p also decreased progressively but unlike NaF, this agent did not show an inhibition of the enzyme. The inhibitory action of NaF was not reversed upon the treatment of heart membranes with deoxycholate or by Ca2+. Lubrol extract (supernatant) of a particulate fraction from rat heart, which showed NaF activation, returned the stimulatory response of the sarcolemmal adenylate cyclase to NaF. These results suggest that some regulatory factor is required for the stimulation of adenylate cyclase by NaF in myocardium and rat heart is susceptible for the loss of such a factor during the sarcolemmal isolation by the hypotonic shock-LiBr treatment method.

Role of phosphatidylinositol in basal adenylate cyclase activity of rat heart sarcolemma

The adenylate cyclase activity and phospholipid composition were determined in rat heart sarcolemma after treating the membranes with a phosphatidylinositol-specific phospholipase C. Complete hydrolysis of phosphatidylinositol in sarcolemma was associated with a marked loss of the basal adenylate cyclase activity. The recombination of the supernatant with the phosphatidylinositol-depleted membranes was found to reactivate the adenylate cyclase activity. The soluble component(s) in the supernatant, which restored the adenylate cyclase activity, was thermolabile and precipitated by ammonium sulfate. Extensive hydrolysis of phosphatidylcholine, phosphatidylethanolamine and sphingomyelin in sarcolemma with a Clostridium welchii phospholipase C treatment did not affect the basal adenylate cyclase activity. These results suggest that phosphatidylinositol anchors component(s) essential for the expression of basal adenylate cyclase activity to the myocardial cell membrane.

Metabolism of 17beta-hydroxy-2-hydroxymethylene-5alpha-androstan-3-one in the rabbit

An acidic metabolite, 2alpha-carboxy-5alpha-androstane-3alpha,16alpha,17alpha-triol and two neutral metabolites, 2alpha-hydroxymethyl-5alpha-androstane-3alpha,17alpha-diol, and 2alpha-hydroxymethyl-5alpha-androstane-3alpha,16alpha,17alpha-triol have been identified in the urine of rabbits orally dosed with 17beta-hydroxy-2-hydroxymethylene-5alpha-androstan-3-one. 2alpha-Hydroxymethyl-5alpha-androstane-3alpha,16alpha,17alpha-triol was previously obtained from the urine of rabbits dosed with 17beta-hydroxy-2alpha-methyl-5alpha-androstan-3-one. The acidic metabolite was the major urinary excretion product.