Removal of endotoxin from recombinant protein preparations

Human oxidation-specific antibodies reduce foam cell formation and atherosclerosis progression

OBJECTIVES

We sought to assess the in vivo importance of scavenger receptor (SR)-mediated uptake of oxidized low-density lipoprotein (OxLDL) in atherogenesis and to test the efficacy of human antibody IK17-Fab or IK17 single-chain Fv fragment (IK17-scFv), which lacks immunologic properties of intact antibodies other than the ability to inhibit uptake of OxLDL by macrophages, to inhibit atherosclerosis.

BACKGROUND

The unregulated uptake of OxLDL by macrophage SR contributes to foam cell formation, but the importance of this pathway in vivo is uncertain.

METHODS

Cholesterol-fed low-density lipoprotein receptor knockout (LDLR(-/-)) mice were treated with intraperitoneal infusion of human IK17-Fab (2.5 mg/kg) 3 times per week for 14 weeks. Because anti-human antibodies developed in these mice, LDLR(-/-)/low-density lipoprotein receptor Rag 1 double-knockout mice (lacking the ability to make immunoglobulins due to loss of T- and B-cell function) were treated with an adenoviral vector encoding adenovirus expressed (Adv)-IK17-scFv or control adenovirus-enhanced green fluorescent protein vector intravenously every 2 weeks for 16 weeks.

RESULTS

In LDLR(-/-) mice, infusion of IK17-Fab was able to sustain IK17 plasma levels for the first 8 weeks, but these diminished afterward due to increasing murine anti-IK17 antibody titers. Despite this, after 14 weeks, a 29% decrease in en face atherosclerosis was noted compared with phosphate-buffered saline-treated mice. In LDLR(-/-)/low-density lipoprotein receptor Rag 1 double-knockout mice, sustained levels of plasma IK17-scFv was achieved by Adv-IK17-scFv-mediated hepatic expression, which led to a 46% reduction (p < 0.001) in en face atherosclerosis compared with adenovirus-enhanced green fluorescent protein vector. Importantly, peritoneal macrophages isolated from Adv-IK17-scFv treated mice had decreased lipid accumulation compared with adenovirus-enhanced green fluorescent protein-treated mice.

CONCLUSIONS

These data support an important role for SR-mediated uptake of OxLDL in the pathogenesis of atherosclerosis and demonstrate that oxidation-specific antibodies reduce the progression of atherosclerosis, suggesting their potential in treating cardiovascular disease in humans.

Analysis of a novel cathepsin B circulating antigen and its response to drug treatment in Trichinella-infected mice

In this paper, we cloned a novel full-length cDNA that encodes a Trichinella spiralis cathepsin B-like protease gene (TsCPB) using 3'-RACE PCR. The recombinant mature TsCPB protein (rTsCPB) was then expressed in an Escherichia coli expression system and purified with Ni-affinity chromatography. Real-time quantitative PCR revealed that TsCPB was expressed across all development stages of the parasite but had the highest expression level during the adult stage. Furthermore, rTsCPB was detected in Trichinella excretory-secretory products with anti-rTsCPB rabbit polyclonal antibodies. Interestingly, rTsCPB was strongly recognized by the T. spiralis-infected sera in Western blotting, implying that TsCPB protein appeared in the peripheral blood of Trichinella-infected mice as circulating antigens (CAg). We then analyzed the dynamic levels of TsCPB CAg and its antibodies in T. spiralis-infected sera by using an improved double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) and indirect ELISA, respectively. The results showed that TsCPB CAg can be detected much earlier compared to antibody detection in Trichinella-infected mice. In addition, we monitored the effects of albendazole drug therapy (a dosage of 370 mg/kg body weight, twice a day) on T. spiralis-infected mice by detecting the levels of TsCPB CAg and its antibody in the sera of drug-treated mice. The results showed that the levels of CAg dramatically decreased after successful drug treatment, while the antibody level remained unchanged. Overall, the novel Trichinella antigen TsCPB could be a promising novel circulating antigen molecule for the detection of Trichinella infection and for monitoring the efficacy of drug treatment of trichinellosis.

An antigenic recombinant serine protease from Trichinella spiralis induces protective immunity in BALB/c mice

In this study, we report the cloning and characterization of a cDNA encoding a Trichinella serine protease gene (TspSP-1.3) from GenBank. The recombinant TspSP-1.3 protein (rTspSP-1.3) was expressed in an Escherichia coli expression system and purified with Ni-affinity chromatography. Real-time quantitative PCR analysis revealed that TspSP-1.3 was expressed at significantly higher levels in muscle larvae and adult worms than in newborn larvae. TspSP-1.3 was detected in excretory-secretory proteins of Trichinella spiralis with western blotting. Immunization with the rTspSP-1.3 antigen induced humoral immune responses, which manifested as elevated specific anti-rTspSP-1.3 IgG and IgE antibodies and a mixed Th1/Th2 response. To determine whether purified rTspSP-1.3 had good antigenicity and could be a vaccine candidate for the control of T. spiralis infection, we immunized BALB/c mice with rTspSP-1.3 and subsequently challenged the mice with T. spiralis larvae. The results showed that mice vaccinated with rTspSP-1.3 exhibited an average reduction in the muscle larvae burden of 39 % relative to the control group. These results suggest that TspSP-1.3 could be a novel vaccine candidate for controlling Trichinella infection.

SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts

Background

Toxoplasma gondii is an intracellular parasite that causes relevant clinical disease in humans and animals. Several studies have been performed in order to understand the interactions between proteins of the parasite and host cells. SAG2A is a 22 kDa protein that is mainly found in the surface of tachyzoites. In the present work, our aim was to correlate the predicted three-dimensional structure of this protein with the immune system of infected hosts.

Methods

To accomplish our goals, we performed in silico analysis of the amino acid sequence of SAG2A, correlating the predictions with in vitro stimulation of antigen presenting cells and serological assays.

Results

Structure modeling predicts that SAG2A protein possesses an unfolded C-terminal end, which varies its conformation within distinct strain types of T. gondii. This structure within the protein shelters a known B-cell immunodominant epitope, which presents low identity with its closest phyllogenetically related protein, an orthologue predicted in Neospora caninum. In agreement with the in silico observations, sera of known T. gondii infected mice and goats recognized recombinant SAG2A, whereas no serological cross-reactivity was observed with samples from N. caninum animals. Additionally, the C-terminal end of the protein was able to down-modulate pro-inflammatory responses of activated macrophages and dendritic cells.

Conclusions

Altogether, we demonstrate herein that recombinant SAG2A protein from T. gondii is immunologically relevant in the host-parasite interface and may be targeted in therapeutic and diagnostic procedures designed against the infection.

One single method to produce native and Tat-fused recombinant human α-synuclein in Escherichia coli

BACKGROUND

Human α-synuclein is a small-sized, natively unfolded protein that in fibrillar form is the primary component of Lewy bodies, the pathological hallmark of Parkinson's disease. Experimental evidence suggests that α-synuclein aggregation is the key event that triggers neurotoxicity although additional findings have proposed a protective role of α-synuclein against oxidative stress. One way to address the mechanism of this protective action is to evaluate α-synuclein-mediated protection by delivering this protein inside cells using a chimeric protein fused with the Tat-transduction domain of HIV Tat, named TAT-α-synuclein.

RESULTS

A reliable protocol was designed to efficiently express and purify two different forms of human α-synuclein. The synthetic cDNAs encoding for the native α-synuclein and the fusion protein with the transduction domain of Tat protein from HIV were overexpressed in a BL21(DE3) E. coli strain as His-tagged proteins. The recombinant proteins largely localized (≥ 85%) to the periplasmic space. By using a quick purification protocol, based on recovery of periplasmic space content and metal-chelating chromatography, the recombinant α-synuclein protein forms could be purified in a single step to ≥ 95% purity. Both α-synuclein recombinant proteins form fibrils and the TAT-α-synuclein is also cytotoxic in the micromolar concentration range.

CONCLUSIONS

To further characterize the molecular mechanisms of α-synuclein neurotoxicity both in vitro and in vivo and to evaluate the relevance of extracellular α-synuclein for the pathogenesis and progression of Parkinson's disease, a suitable method to produce different high-quality forms of this pathological protein is required. Our optimized expression and purification procedure offers an easier and faster means of producing different forms (i.e., both the native and the TAT-fusion form) of soluble recombinant α-synuclein than previously described procedures.

Functional characterization of fish neuroglobin: zebrafish neuroglobin is highly expressed in amacrine cells after optic nerve injury and can translocate into ZF4 cells

Neuroglobin (Ngb) is a recently discovered vertebrate heme protein that is expressed in the brain and can reversibly bind oxygen. Mammalian Ngb is involved in neuroprotection under conditions of oxidative stress, such as ischemia and reperfusion. We previously found that zebrafish Ngb can penetrate the mammalian cell membrane. In the present study, we investigated the functional characteristics of fish Ngb by using the zebrafish cell line ZF4 and zebrafish retina. We found that zebrafish Ngb translocates into ZF4 cells, but cannot protect ZF4 cells against cell death induced by hydrogen peroxide. Furthermore, we demonstrated that a chimeric ZHHH Ngb protein, in which module M1 of human Ngb is replaced by that of zebrafish, is a cell-membrane-penetrating protein that can protect ZF4 cells against hydrogen peroxide exposure. Moreover, we investigated the localization of Ngb mRNA and protein in zebrafish retina and found that Ngb mRNA is expressed in amacrine cells in the inner nuclear layer and is significantly increased in amacrine cells 3days after optic nerve injury. Immunohistochemical studies clarified that Ngb protein levels were increased in both amacrine cells and presynaptic regions in the inner plexiform layer after nerve injury. Taken together, we hypothesize that fish Ngb, whose expression is upregulated in amacrine cells after optic nerve injury, might be released from amacrine cells, translocate into neighboring ganglion cells, and function in the early stage of optic nerve regeneration. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins.

Macrophage migration inhibitory factor (MIF) of the protozoan parasite Eimeria influences the components of the immune system of its host, the chicken

Macrophage migration inhibitory factor (MIF) is a soluble factor produced by sensitized T lymphocytes that inhibits the random migration of macrophages. Homologues of MIF from invertebrates have been identified, making it an interesting molecule from a functional perspective. In the present study, the localization of a parasite MIF protein as well as its effect on the host was characterized. Western blot analysis shows that Eimeria MIF (EMIF) is found during all parasite developmental stages tested. Transmission electron microscopy shows that MIF is distributed throughout cytosol and nucleus of Eimeria acervulina merozoites. Immunohistochemical analysis suggests that EMIF may be released into the surrounding tissues as early as 24 h after infection, while later during oocyst formation, MIF expression is localized to areas immediately surrounding the oocysts, as well as in wall-forming bodies. The chemotaxis assay revealed an inhibitory function of EMIF on chicken monocyte migration. Quantitative real-time PCR was performed to examine the effect of EMIF on host immune system by measuring the transcripts of inflammatory mediators. An ex vivo stimulation study showed that E. acervulina MIF (EaMIF) enhanced expression of pro-inflammatory cytokines and chemokines in the presence of lipopolysaccharide (LPS). Furthermore, sequential treatment of adherent peripheral blood mononuclear cells with EaMIF, chicken MIF, and LPS in 2-h intervals led to the highest levels of interleukin (IL)-1B, chemokine CCLi3, IL-18, and interferon-gamma mRNA expression. This study shows that parasite MIF is widely expressed and may have potential effects on the immune system of the host.

Antigen replacement of domains D2 and D3 in flagellin promotes mucosal IgA production and attenuates flagellin-induced inflammatory response after intranasal immunization

Targeting early infection in mucosal sites is one of the primary goals for mucosal vaccines so as to prevent pathogen mucosal transmission and infection. The TLR5 agonist flagellin was deemed to be a mucosal adjuvant candidate for clinical usage. However, the high antigenicity of flagellin and the possible inflammatory injury induced by flagellin might restrict its clinical usage. Here HIV-1 p24 protein was selected as an antigen model and we replaced the main antigenicity region domains D2 and D3 of non-pathogenic E.coli-derived flagellin (KF). The derived soluble protein KFD-p24 3D was then compared with KF-p24, which fused p24 directly to the C-terminal of KF. In vitro and ex vivo experiments showed that KFD-p24 3D has lower TLR5 agonist efficacy and less immunocyte-activating efficacy. Interestingly, the production of KF- specific antibody was highly reduced, and KFD-p24 3D induced IgA-biased antibody responses in mucosal sites. Moreover, KFD-p24 3D induced far fewer systemic inflammatory responses and abrogated detectable inflammatory side effects on mice, even at the high dose. The properties of enhanced IgA generation and attenuated inflammatory responses broaden the safe-dose range of KFD-p24 3D flagellin, creating a potentially promising mucosal adjuvant.

Assessment of a protein cocktail-based skin test for bovine tuberculosis in a double-blind field test in cattle

Bovine tuberculosis (bTB) is a worldwide zoonosis caused mainly by Mycobacterium bovis. The traditional diagnostic method used often is the tuberculin skin test, which uses bovine purified protein derivatives (PPD-B). However, it is difficult to maintain uniformity of PPD-B from batch to batch, and it shares common antigens with nonpathogenic environmental mycobacteria. To overcome these problems, M. bovis-specific antigens that showed good T cell stimulation, such as CFP-10, ESAT-6, Rv3615c, etc., have been used in the skin test, but there have been no large-scale clinical studies on these antigens. In this study, two combinations (CFP-10/ESAT-6/TB10.4 protein cocktail and CFP-10/ESAT-6/Rv3872/MPT63 protein cocktail) were developed and used as stimuli in the skin test. Cattle were double-blind tested to assess the efficiency of the protein cocktail-based skin tests. The results showed that the CFP-10/ESAT-6/TB10.4 protein cocktail-based skin test can differentiate TB-infected cattle from Mycobacterium avium-infected ones and that it shows a high degree of agreement with the traditional tuberculin skin test (κ = 0.8536) and gamma interferon (IFN-γ) release assay (κ = 0.8154). Compared to the tuberculin skin test, the relative sensitivity and relative specificity of the CFP-10/ESAT-6/TB10.4-based skin test were 87% and 97%, respectively., The relative sensitivity and relative specificity of the CFP-10/ESAT-6/TB10.4-based skin test were 93% and 92%, respectively, on comparison with the IFN-γ release assay. The correlation between the increases in skin thickness observed after the inoculation of stimuli was high (PPD-B versus CFP-10/ESAT-6/TB10.4, Spearman r of 0.8435). The correlation between the optical density at 450 nm (OD450) obtained after blood stimulation with PPD-B and the increase in skin thickness observed after inoculation of the CFP-10/ESAT-6/TB10.4 protein cocktail was high (Spearman r = 0.7335). Therefore, the CFP-10/ESAT-6/TB10.4-based skin test responses correlate to traditional measures of bovine TB evaluation, including skin test and gamma interferon release assay.

Helicobacter pylori thiolperoxidase as a protective antigen in single- and multi-component vaccines

Helicobacter pylori is an important pathogen of the human stomach, and the development of a protective vaccine has been an enticing goal for many years. The H. pylori antioxidant enzymes superoxide dismutase (SOD) and catalase (KatA) have been shown to be protective as vaccine antigens in mice, demonstrating that the organism's antioxidant enzyme system is a fruitful target for vaccine development. The research described here demonstrates that an additional antioxidant enzyme, thiolperoxidase (Tpx), is effective as a prophylactic vaccine antigen via both systemic and mucosal routes. The functional relationship between SOD, KatA and Tpx also provided an opportunity to investigate synergistic or additive effects when the three antigens were used in combination. Although the antigens still provided equivalent protection when administered in combination, no additional protection was observed. Moreover a decrease in antibody titres to the individual antigens was observed when delivered in combination via the nasal route, though not when injected subcutaneously. The findings of this paper demonstrate that the antioxidant system of H. pylori presents a particularly rich resource for vaccine development.

Protein polymer hydrogels: effects of endotoxin on biocompatibility

Protein polymer-based hydrogels have shown potential for tissue engineering applications, but require biocompatibility testing for in vivo use. Enzymatically crosslinked protein polymer-based hydrogels were tested in vitro and in vivo to evaluate their biocompatibility. Endotoxins present in the hydrogel were removed by Trition X-114 phase separation. The reduction of endotoxins decreased TNF-α production by a macrophage cell line in vitro; however, significant inflammatory response was still present compared to collagen control gels. A branched PEG molecule and dexamethasone were added to the hydrogel to reduce the response. In vitro testing showed a decrease in the TNF-α levels with the addition of dexamethasone. In vivo implantations into the epididymal fat pad of C57/BL6 mice, however, indicated a decreased inflammatory mediated immune response with a hydrogel treated with both PEGylation and endotoxin reduction. This study demonstrates the importance of endotoxin testing and removal in determining the biocompatibility of biomaterials.

Discordant antibody and cellular responses to Pneumocystis major surface glycoprotein variants in mice

Background

The major surface glycoprotein (Msg) of Pneumocystis is encoded by approximately 50 to 80 unique but related genes. Msg diversity may represent a mechanism for immune escape from host T cell responses. We examined splenic T cell proliferative and cytokine as well as serum antibody responses to recombinant and native Pneumocystis antigens in immunized or Pneumocystis-infected mice. In addition, immune responses were examined in 5 healthy humans.

Results

Proliferative responses to each of two recombinant Msg variant proteins were seen in mice immunized with either recombinant protein, but no proliferation to these antigens was seen in mice immunized with crude Pneumocystis antigens or in mice that had cleared infection, although the latter animals demonstrated proliferative responses to crude Pneumocystis antigens and native Msg. IL-17 and MCP-3 were produced in previously infected animals in response to the same antigens, but not to recombinant antigens. Antibody responses to the recombinant P. murina Msg variant proteins were seen in all groups of animals, demonstrating that all groups were exposed to and mounted immune responses to Msg. No human PBMC samples proliferated following stimulation with P. jirovecii Msg, while antibody responses were detected in sera from 4 of 5 samples.

Conclusions

Cross-reactive antibody responses to Msg variants are common, while cross-reactive T cell responses are uncommon; these results support the hypothesis that Pneumocystis utilizes switching of Msg variant expression to avoid host T cell responses.

Human neuroglobin functions as an oxidative stress-responsive sensor for neuroprotection

Mammalian neuroglobin (Ngb) protects neuronal cells under conditions of oxidative stress. The mechanism underlying this function is only partly understood. Here, we report that human Ngb exists in lipid rafts only during oxidative stress and that lipid rafts are crucial for neuroprotection by Ngb. The ferrous oxygen-bound form of Ngb, which exists under normoxia, is converted to the ferric bis-His conformation during oxidative stress, inducing large tertiary structural changes. We clarified that ferric bis-His Ngb, but not ferrous ligand-bound Ngb, specifically binds to flotillin-1, a lipid raft microdomain-associated protein, as well as to α-subunits of heterotrimeric G proteins (Gα(i/o)). Moreover, we found that human ferric bis-His Ngb acts as a guanine nucleotide dissociation inhibitor for Gα(i/o) that has been modified by oxidative stress. In addition, our data shows that Ngb inhibits the decrease in cAMP concentration that occurs under oxidative stress, leading to protection against cell death. Furthermore, by using a mutated Ngb protein that cannot form the bis-His conformation, we demonstrate that the oxidative stress-induced structural changes of human Ngb are essential for its neuroprotective activity.

Formin mDia1 mediates vascular remodeling via integration of oxidative and signal transduction pathways

RATIONALE

The mammalian diaphanous-related formin (mDia1), governs microtubule and microfilament dynamics while functioning as an effector for Rho small GTP-binding proteins during key cellular processes such as adhesion, cytokinesis, cell polarity, and morphogenesis. The cytoplasmic domain of the receptor for advanced glycation endproducts binds to the formin homology 1 domain of mDia1; mDia1 is required for receptor for advanced glycation endproducts ligand-induced cellular migration in transformed cells.

OBJECTIVE

Because a key mechanism in vascular remodeling is the induction of smooth muscle cell migration, we tested the role of mDia1 in this process.

METHODS AND RESULTS

We report that endothelial denudation injury to the murine femoral artery significantly upregulates mDia1 mRNA transcripts and protein in the injured vessel, particularly in vascular smooth muscle cells within the expanding neointima. Loss of mDia1 expression significantly reduces pathological neointimal expansion consequent to injury. In primary murine aortic smooth muscle cells, mDia1 is required for receptor for advanced glycation endproducts ligand-induced membrane translocation of c-Src, which leads to Rac1 activation, redox phosphorylation of AKT/glycogen synthase kinase 3β, and consequent smooth muscle cell migration.

CONCLUSIONS

We conclude that mDia1 integrates oxidative and signal transduction pathways triggered, at least in part, by receptor for advanced glycation endproducts ligands, thereby regulating pathological neointimal expansion.

A combined strategy improves the solubility of aggregation-prone single-chain variable fragment antibodies

Recombinant single-chain variable fragment (scFv) antibodies have wide applications in the areas of biotechnology and medicine. However, there is currently no universal expression-purification system for generating different soluble scFvs. In this study, A15 and E34, two genes coding scFvs against human IL-17A, were fused with N-terminal signal peptide sequences pelB or STII, or with highly hydrophilic tags Trx, NusA, or MBP, respectively. These constructs were expressed in Escherichia coli. We found that the scFvs fused with either NusA or MBP showed a higher solubility than fused with signal peptides or Trx. The scFvs were aggregated when the NusA or MBP was removed by thrombin. Interestingly, we observed a reduction of precipitation when the fusion proteins were expressed in Origami B(DE3)pLysS cells but not in BL21(DE3)pLysS. Because cleaving the tags resulted in the aggregation of scFvs, several solubility-enhancing additives were added in the digestion buffer and only L-arginine (Arg) or Tween20 promoted the solubility. After an affinity chromatography, the scFvs were separated from the tags with the purity up to 90%. The final yield of scFvs from the scFv-MBP system was approximately 8.9 mg/L of culture medium and 1.5 mg/g of wet weight cells, which was 1.6-fold higher than the yield from the scFv-NusA system. The obtained scFvs exhibited normal binding affinities and activities after endotoxin removal. In conclusion, we describe a strategy combining the fusion tags, the Escherichia coli with oxidizing bacterial cytoplasm, and the solubility-enhancing additives for expressing and purifying the soluble and functional scFvs.

Enhancement of immune response towards non-lipidized Borrelia burgdorferi recombinant OspC antigen by binding onto the surface of metallochelating nanoliposomes with entrapped lipophilic derivatives of norAbuMDP

Lyme disease caused by spirochete Borrelia burgdorferi sensu lato, is a tick-born illness. If the infection is not eliminated by the host immune system and/or antibiotics, it may further disseminate and cause severe chronic complications. The immune response to Borrelia is mediated by phagocytic cells and by Borrelia-specific complement-activating antibodies associated with Th1 cell activation. A new experimental vaccine was constructed using non-lipidized form of recombinant B. burgdorferi s.s. OspC protein was anchored by metallochelating bond onto the surface of nanoliposomes containing novel nonpyrogenic lipophilized norAbuMDP analogues denoted MT05 and MT06. After i.d. immunization, the experimental vaccines surpassed Alum with respect to OspC-specific titers of IgG2a, IgG2b isotypes when MT06 was used and IgG3, IgM isotypes when MT05 was used. Both adjuvants exerted a high adjuvant effect comparable or better than MDP and proved themselves as nonpyrogenic.

Antigen targeting to major histocompatibility complex class II with streptococcal mitogenic exotoxin Z-2 M1, a superantigen-based vaccine carrier

Streptococcal mitogenic exotoxin Z-2 (SMEZ-2) is a streptococcal superantigen that primarily stimulates human T cells bearing Vβ8 and mouse T cells bearing Vβ11. Mutagenesis of T cell receptor (TCR)-binding residues (W75L, K182Q, D42C) produced a mutant called M1 that was >10(5)-fold less active toward human peripheral blood lymphocytes and splenocytes from transgenic mice that express human CD4 and either human HLA-DR3-DQ2 or HLA-DR4-DQ8. Similarly, cytokine production in response to M1 in lymphocyte culture was rendered undetectable, and no change in the frequency of Vβ11-bearing T cells in mice receiving M1 was observed. M1 toxoid was tested as a potential vaccine conjugate. Vaccination with 1 to 10 μg M1 conjugated to ovalbumin (M1-ovalbumin) resulted in more rapid and quantitatively higher levels of anti-ovalbumin IgG, with endpoint titers being 1,000- to 10,000-fold greater than those in animals immunized with unconjugated ovalbumin. Substantially higher levels of anti-ovalbumin IgG were observed in mice transgenic for human major histocompatibility complex (MHC) class II. Substitution of M1 with an MHC class II binding mutant (DM) eliminated enhanced immunity, suggesting that M1 enhanced the delivery of antigen via MHC class II-positive antigen-presenting cells that predominate within lymphoid tissue. Immunization of animals with a conjugate consisting of M1 and ovalbumin peptide from positions 323 to 339 generated levels of anti-peptide IgG 100-fold higher than those in animals immunized with peptide alone. Coupling of a TCR-defective superantigen toxoid presents a new strategy for conjugate vaccines with the additional benefit of targeted delivery to MHC class II-bearing cells.

Treatment with recombinant Hsp72 suppresses collagen-induced arthritis in mice

Although the level of heat shock protein (Hsp72) has been shown to be enhanced in rheumatoid arthritis (RA) synovial tissues and RA synovial fluid, it remains unclear what role extracellular Hsp72 plays in the pathogenesis of RA. This study was conducted to investigate the effects of recombinant human Hsp72 on collagen-induced arthritis (CIA) when administered therapeutically and elucidate its underlying mechanism. We demonstrated that recombinant Hsp72 significantly reduced disease severity. Hsp72-treated animals displayed significantly less cartilage and bone destruction than that in the controls. Hsp72 treatment also reduced the expression of tumor necrosis factor alpha and interleukin 6 in the sera. Furthermore, Hsp72 treatment significantly inhibited activation of nuclear factor kappa B (NF-κB) in synovial tissues of CIA mice. These findings suggest that recombinant Hsp72 effectively suppressed synovial inflammation and the development and progress of CIA, which is mediated through the reduction of production of proinflammatory cytokines and the suppression of activation of NF-κB pathway.

Optimization of purification protocols based on the step-by-step monitoring of the protein aggregates in soluble fractions

Soluble protein fractions are often considered containing exclusively monodispersed and correctly folded molecules. This is not the case, being soluble aggregates of different complexity widely represented in such fractions. The use of fusing target protein domains to highly soluble carriers may strongly contribute to soluble aggregate accumulation. Therefore, reliable analytical methods must be used to evaluate the biophysical characteristics of soluble proteins. On the other hand, conventional methodologies are often technically demanding and time consuming. In this method paper, a protocol is presented that enables the rapid evaluation of the protein monodispersity from the initial step aimed at screening several conditions in parallel to the setup of the complete protocol for large-scale purification. The analysis is performed by means of simple lab equipment and starting from small sample volumes.

Rv2468c, a novel Mycobacterium tuberculosis protein that costimulates human CD4+ T cells through VLA-5

Mtb regulates many aspects of the host immune response, including CD4+ T lymphocyte responses that are essential for protective immunity to Mtb, and Mtb effects on the immune system are paradoxical, having the capacity to inhibit (immune evasion) and to activate (adjuvant effect) immune cells. Mtb regulates CD4+ T cells indirectly (e.g., by manipulation of APC function) and directly, via integrins and TLRs expressed on T cells. We now report that previously uncharacterized Mtb protein Rv2468c/MT2543 can directly regulate human CD4+ T cell activation by delivering costimulatory signals. When combined with TCR stimulation (e.g., anti-CD3), Rv2468c functioned as a direct costimulator for CD4+ T cells, inducing IFN-γ secretion and T cell proliferation. Studies with blocking antibodies and soluble RGD motifs demonstrated that Rv2468c engaged integrin VLA-5 (α5β1) on CD4+ T cells through its FN-like RGD motif. Costimulation by Rv2468c induced phosphorylation of FAKs and Pyk2. These results reveal that by expressing molecules that mimic host protein motifs, Mtb can directly engage receptors on CD4+ T cells and regulate their function. Rv2468c-induced costimulation of CD4+ T cells could have implications for TB immune pathogenesis and Mtb adjuvant effect.

In vivo visualization and attenuation of oxidized lipid accumulation in hypercholesterolemic zebrafish

Oxidative modification of LDL is an early pathological event in the development of atherosclerosis. Oxidation events such as malondialdehyde (MDA) formation may produce specific, immunogenic epitopes. Indeed, antibodies to MDA-derived epitopes are widely used in atherosclerosis research and have been demonstrated to enable cardiovascular imaging. In this study, we engineered a transgenic zebrafish with temperature-inducible expression of an EGFP-labeled single-chain human monoclonal antibody, IK17, which binds to MDA-LDL, and used optically transparent zebrafish larvae for imaging studies. Feeding a high-cholesterol diet (HCD) supplemented with a red fluorescent lipid marker to the transgenic zebrafish resulted in vascular lipid accumulation, quantified in live animals using confocal microscopy. After heat shock-induced expression of IK17-EGFP, we measured the time course of vascular accumulation of IK17-specific MDA epitopes. Treatment with either an antioxidant or a regression diet resulted in reduced IK17 binding to vascular lesions. Interestingly, homogenates of IK17-EGFP-expressing larvae bound to MDA-LDL and inhibited MDA-LDL binding to macrophages. Moreover, sustained expression of IK17-EGFP effectively prevented HCD-induced lipid accumulation in the vascular wall, suggesting that the antibody itself may have therapeutic effects. Thus, we conclude that HCD-fed zebrafish larvae with conditional expression of EGFP-labeled oxidation-specific antibodies afford an efficient method of testing dietary and/or other therapeutic antioxidant strategies that may ultimately be applied to humans.

Entamoeba lysyl-tRNA synthetase contains a cytokine-like domain with chemokine activity towards human endothelial cells

Immunological pressure encountered by protozoan parasites drives the selection of strategies to modulate or avoid the immune responses of their hosts. Here we show that the parasite Entamoeba histolytica has evolved a chemokine that mimics the sequence, structure, and function of the human cytokine HsEMAPII (Homo sapiens endothelial monocyte activating polypeptide II). This Entamoeba EMAPII-like polypeptide (EELP) is translated as a domain attached to two different aminoacyl-tRNA synthetases (aaRS) that are overexpressed when parasites are exposed to inflammatory signals. EELP is dispensable for the tRNA aminoacylation activity of the enzymes that harbor it, and it is cleaved from them by Entamoeba proteases to generate a standalone cytokine. Isolated EELP acts as a chemoattractant for human cells, but its cell specificity is different from that of HsEMAPII. We show that cell specificity differences between HsEMAPII and EELP can be swapped by site directed mutagenesis of only two residues in the cytokines' signal sequence. Thus, Entamoeba has evolved a functional mimic of an aaRS-associated human cytokine with modified cell specificity.

Endotoxin-free purification for the isolation of bovine viral diarrhoea virus E2 protein from insoluble inclusion body aggregates

Background

Protein expression in Escherichia coli may result in the recombinant protein being expressed as insoluble inclusion bodies. In addition, proteins purified from E. coli contain endotoxins which need to be removed for in vivo applications. The structural protein, E2, from Bovine Viral Diarrhoea Virus (BVDV) is a major immunogenic determinant, and is an ideal candidate as a subunit vaccine. The E2 protein contains 17 cysteine residues creating difficulties in E. coli expression. In this report we outline a procedure for successfully producing soluble and endotoxin-free BVDV E2 protein from inclusion bodies (IB).

Results

The expression of a truncated form of BVDV-E2 protein (E2-T1) in E. coli resulted in predominantly aggregated insoluble IB. Solubilisation of E2-T1 with high purity and stability from IB aggregates was achieved using a strong reducing buffer containing 100 mM Dithiothreitol. Refolding by dialysis into 50 mM Tris (pH 7.0) containing 0.2% Igepal CA630 resulted in a soluble but aggregated protein solution. The novel application of a two-phase extraction of inclusion body preparations with Triton X-114 reduced endotoxin in solubilised E2-T1 to levels suitable for in vivo use without affecting protein yields. Dynamic light scattering analyses showed 37.5% of the protein was monomeric, the remaining comprised of soluble aggregates. Mice immunised with E2-T1 developed a high titre antibody response by ELISA. Western hybridisation analysis showed E2-T1 was recognised by sera from immunised mice and also by several BVDV-E2 polyclonal and monoclonal antibodies.

Conclusion

We have developed a procedure using E. coli to produce soluble E2-T1 protein from IB, and due to their insoluble nature we utilised a novel approach using Triton X-114 to efficiently remove endotoxin. The resultant protein is immunogenic and detectable by BVDV-E2 specific antibodies indicating its usefulness for diagnostic applications and as a subunit vaccine. The optimised E. coli expression system for E2-T1 combined with methodologies for solubilisation, refolding and integrated endotoxin removal presented in this study should prove useful for other vaccine applications.

Designing the next generation of vaccines for global public health

Vaccine research and development are experiencing a renaissance of interest from the global scientific community. There are four major reasons for this: (1) the lack of efficacious treatment for many devastating infections; (2) the emergence of multidrug resistant bacteria; (3) the need for improving the safety of the more traditional licensed vaccines; and finally, (4) the great promise for innovative vaccine design and research with convergence of omics sciences, such as genomics, proteomics, immunomics, and vaccinology. Our first project based on omics was initiated in 2000 and was termed reverse vaccinology. At that time, antigen identification was mainly based on bioinformatic analysis of a singular genome. Since then, omics-guided approaches have been applied to its full potential in several proof-of-concept studies in the industry, with the first reverse vaccinology-derived vaccine now in late stage clinical trials and several vaccines developed by omics in preclinical studies. In the meantime, vaccine discovery and development has been further improved with the support of proteomics, functional genomics, comparative genomics, structural biology, and most recently vaccinomics. We illustrate in this review how omics biotechnologies and integrative biology are expected to accelerate the identification of vaccine candidates against difficult pathogens for which traditional vaccine development has thus far been failing, and how research will provide safer vaccines and improved formulations for immunocompromised patients in the near future. Finally, we present a discussion to situate omics-guided rational vaccine design in the broader context of global public health and how it can benefit citizens in both developed and developing countries.

Myeloid related proteins activate Toll-like receptor 4 in human acute coronary syndromes

INTRODUCTION

We previously reported increased expression of TLR4 on monocytes in thrombi from patients with acute coronary syndromes (ACS). In mice, myeloid related protein (MRP) 8 and MRP14, cytoplasmic proteins of neutrophils and monocytes, activate Toll-like receptor (TLR) 4 during sepsis. In human ACS, we investigated now whether the pro-inflammatory action of MRPs occurs through TLR4 in monocytes derived from thrombi.

METHODS

Coronary thrombi and peripheral blood of 27 ACS patients were analyzed. CD14(+) monocytes were isolated and incubated with TLR2 ligand PM3SKA, TLR4 ligand lipopolysaccharide (LPS), MRP8, MRP14, or MRP8/14 heterocomplex. Anti-TLR4 antibodies (HTA125) were used to block TLR4 and polymyxin B (PMB) was employed to inhibit endotoxins. Before and after stimulation, the release of TNFα was measured by ELISA and the expression of TLR4 on CD14(+) monocytes was determined by flow cytometry. Further, selected pathways of downstream signaling were analyzed.

RESULTS

MRP8 and MRP8/14 increased release of TNFα in cultures of CD14(+) monocytes, more in cells derived from thrombi compared with matched peripheral blood cells (p<0.001). LPS, MRP8, and MRP8/14, but much less PM3SKA and MRP14 alone, stimulated TNFα release, which can be inhibited by HTA125. MRP8/14 enhanced TLR4 expression on monocytes from thrombi (p<0.001), but not on monocytes from peripheral blood of the same patients.

CONCLUSION

In ACS, MRP8 and MRP8/14 complex are specific ligands of TLR4, which induce the release of TNFα and probably other pro-inflammatory agents from monocytes. This specific MRP8/14-dependent pathway with striking similarities to sepsis increasing expression of TLR4 in thrombi appears to be involved in the pathogenesis of coronary occlusion and may represent a novel therapeutic target in ACS.

SplitCore: an exceptionally versatile viral nanoparticle for native whole protein display regardless of 3D structure

Nanoparticles displaying native proteins are attractive for many applications, including vaccinology. Virus-based nanoparticles are easily tailored by genetic means, commonly by inserting heterologous sequences into surface-exposed loops. The strategy works well with short peptides but is incompatible with the structures of most native proteins, except those with closely juxtaposed termini. Here we overcome this constraint by splitting the capsid protein of hepatitis B virus, one of the most advanced and most immunogenic display platforms, inside the insertion loop (SplitCore). The split parts, coreN and coreC, efficiently form capsid-like particles (CLPs) in E. coli and so do numerous fusions to coreN and/or coreC of differently structured proteins, including human disease related antigens of >300 amino acids in length. These CLPs induced high-titer antibodies, including neutralizing ones, in mice. The concept was easily expanded to triple-layer CLPs carrying reporter plus targeting domains, and should be applicable to protein-based nanoparticle design in general.

TLR1/2 activation during heterologous prime-boost vaccination (DNA-MVA) enhances CD8+ T Cell responses providing protection against Leishmania (Viannia)

BACKGROUND

Leishmania (Viannia) parasites present particular challenges, as human and murine immune responses to infection are distinct from other Leishmania species, indicating a unique interaction with the host. Further, vaccination studies utilizing small animal models indicate that modalities and antigens that prevent infection by other Leishmania species are generally not protective.

METHODOLOGY

Using a newly developed mouse model of chronic L. (Viannia) panamensis infection and the heterologous DNA prime - modified vaccinia virus Ankara (MVA) boost vaccination modality, we examined whether the conserved vaccine candidate antigen tryparedoxin peroxidase (TRYP) could provide protection against infection/disease.

RESULTS

Heterologous prime - boost (DNA/MVA) vaccination utilizing TRYP antigen can provide protection against disease caused by L. (V.) panamensis. However, protection is dependent on modulating the innate immune response using the TLR1/2 agonist Pam3CSK4 during DNA priming. Prime-boost vaccination using DNA alone fails to protect. Prior to infection protectively vaccinated mice exhibit augmented CD4 and CD8 IFNγ and memory responses as well as decreased IL-10 and IL-13 responses. IL-13 and IL-10 have been shown to be independently critical for disease in this model. CD8 T cells have an essential role in mediating host defense, as CD8 depletion reversed protection in the vaccinated mice; vaccinated mice depleted of CD4 T cells remained protected. Hence, vaccine-induced protection is dependent upon TLR1/2 activation instructing the generation of antigen specific CD8 cells and restricting IL-13 and IL-10 responses.

CONCLUSIONS

Given the general effectiveness of prime-boost vaccination, the recalcitrance of Leishmania (Viannia) to vaccine approaches effective against other species of Leishmania is again evident. However, prime-boost vaccination modality can with modulation induce protective responses, indicating that the delivery system is critical. Moreover, these results suggest that CD8 T cells should be targeted for the development of a vaccine against infection caused by Leishmania (Viannia) parasites. Further, TLR1/2 modulation may be useful in vaccines where CD8 T cell responses are critical.

Recombinant Porphyromonas gingivalis FimA preproprotein expressed in Escherichia coli is lipidated and the mature or processed recombinant FimA protein forms a short filament in vitro

The gram-negative anaerobic bacterium Porphyromonas gingivalis is an etiologically important pathogen for chronic periodontal diseases in adults. Our previous study suggested that the major structural components of both Fim and Mfa fimbriae in this organism are secreted through their lipidated precursors. In this study, we constructed Escherichia coli strains expressing various fimA genes with or without the 5'-terminal DNA region encoding the signal peptide, and we determined whether lipidation of recombinant FimA proteins occurred in E. coli. Lipidation occurred for a recombinant protein from the fimA gene with the 5'-terminal DNA region encoding the signal peptide but not for a recombinant protein from the fimA gene without the signal-peptide-encoding region, as revealed by [3H]palmitic acid labeling experiments. A TLR2-dependent signaling response was induced by the recombinant protein from the fimA gene with the signal-peptide-encoding region but not by a recombinant protein from the fimA gene with the signal-peptide-encoding region that had a base substitution causing an amino acid substitution (C19A). Electron microscopic analysis revealed that recombinant FimA (A-47 - W-383) protein was autopolymerized to form filamentous structures of about 80 nm in length in vitro. The results suggest that FimA protein, a major subunit of Fim fimbriae, is transported to the outer membrane by the lipoprotein sorting system, and a mature or processed FimA protein on the outer membrane is autopolymerized to form Fim fimbriae.

E. coli Lipopolysaccharide: acute oral toxicity study in mice

A single dose of endotoxin (lipopolysaccharide) from a common laboratory cloning and expression strain (Escherichia coli BL21[DE3]) was administered to groups of male and female CD-1 mice (n=5/group) at doses up to 1,000,000 endotoxin units (EU) per mouse by oral gavage. The mice were observed for mortality, body weight effects, and clinical signs for 14 days after which they were sacrificed for gross organ necropsy. All mice survived until the scheduled sacrifice, no clinical signs of toxicity were observed, no test substance-related body weight losses occurred and no gross lesions were present at necropsy. Under the conditions of this study, oral administration of E. coli BL21(DE3) endotoxin to mice at a dose of up to 1,000,000 EU/mouse produced no evidence of toxicity.

Protein polymer MRI contrast agents: Longitudinal analysis of biomaterials in vivo

Despite recent advances in tissue engineering to regenerate biological function by combining cells with material supports, development is hindered by inadequate techniques for characterizing biomaterials in vivo. Magnetic resonance imaging is a tomographic technique with high temporal and spatial resolution and represents an excellent imaging modality for longitudinal noninvasive assessment of biomaterials in vivo. To distinguish biomaterials from surrounding tissues for magnetic resonance imaging, protein polymer contrast agents were developed and incorporated into hydrogels. In vitro and in vivo images of protein polymer hydrogels, with and without covalently incorporated protein polymer contrast agents, were acquired by magnetic resonance imaging. T(1) values of the labeled gels were consistently lower when protein polymer contrast agents were included. As a result, the protein polymer contrast agent hydrogels facilitated fate tracking, quantification of degradation, and detection of immune response in vivo. For the duration of the in vivo study, the protein polymer contrast agent-containing hydrogels could be distinguished from adjacent tissues and from the foreign body response surrounding the gels. The hydrogels containing protein polymer contrast agent have a contrast-to-noise ratio 2-fold greater than hydrogels without protein polymer contrast agent. In the absence of the protein polymer contrast agent, hydrogels cannot be distinguished by the end of the gel lifetime.

Module M1 of zebrafish neuroglobin acts as a structural and functional protein building block for a cell-membrane-penetrating activity

Neuroglobin (Ngb) is a recently discovered vertebrate globin that is expressed in the brain and can reversibly bind oxygen. Mammalian Ngb is involved in neuroprotection during oxidative stress that occurs, for example, during ischemia and reperfusion. Recently, we found that zebrafish, but not human, Ngb can translocate into cells. Moreover, we demonstrated that a chimeric ZHHH Ngb protein, in which the module M1 of human Ngb is replaced by the corresponding region of zebrafish Ngb, can penetrate cell membranes and protect cells against oxidative stress-induced cell death, suggesting that module M1 of zebrafish Ngb is important for protein transduction. Furthermore, we recently showed that Lys7, Lys9, Lys21, and Lys23 in module M1 of zebrafish Ngb are crucial for protein transduction activity. In the present study, we have investigated whether module M1 of zebrafish Ngb can be used as a building block to create novel cell-membrane-penetrating folded proteins. First, we engineered a chimeric myoglobin (Mb), in which module M1 of zebrafish Ngb was fused to the N-terminus of full-length human Mb, and investigated its functional and structural properties. Our results showed that this chimeric Mb protein is stable and forms almost the same heme environment and α-helical structure as human wild-type Mb. In addition, we demonstrated that chimeric Mb has a cell-membrane-penetrating activity similar to zebrafish Ngb. Moreover, we found that glycosaminoglycan is crucial for the cell-membrane-penetrating activity of chimeric Mb as well as that of zebrafish Ngb. These results enable us to conclude that such module substitutions will facilitate the design and production of novel functional proteins.

Endotoxin removing method based on lipopolysaccharide binding protein and polyhydroxyalkanoate binding protein PhaP

Polyhydroxyalkanoates (PHAs) granule associated protein PhaP has a strong affinity to PHA and other hydrophobic polymers. Human lipopolysaccharide binding protein (hLBP) is a natural endotoxin receptor in plasma. In this study, genes encoding hLBP fused with PhaP were expressed in Pichia pastoris GS115 for production of the fusion protein. The purified rhLBP-PhaP fusion protein was immobilized on particles of polyhydroxybutyrate (PHB), which is a member of microbial polyhydroxyalkanoates (PHA). The rhLBP-PhaP-coated PHB particles were added to endotoxin containing water and protein solutions to study their endotoxin removal and protein recovery efficiencies. The influences of ionic strengths and pH on endotoxin removal and protein recovery in different protein solutions were also studied using acidic proteins including bovine serum albumin (BSA), ovalbumin, and basic protein α-chymotrypsinogen as model proteins. The results showed that rhLBP-PhaP particles could remove endotoxin with an efficiency of over 90%. All endotoxin removal and protein recovery efficiencies were only slightly affected by ionic strengths but were drastically affected by pH changes. Our results demonstrated that rhLBP-PhaP particles with their high efficiency, ease of preparation, and nontoxicity will be a suitable system for endotoxin removal in the protein purification industry.