Tail-vein injection of mannan-binding lectin DNA leads to high expression levels of multimeric protein in liver

Evolution of the Experimental Models of Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a rare, aggressive disease with poor overall survival. In advanced cases, surgery is often not possible or fails; in addition, there is a lack of effective and specific therapies. Multidisciplinary approaches and advanced technologies have improved the knowledge of CCA molecular pathogenesis, highlighting its extreme heterogeneity and high frequency of genetic and molecular aberrations. Effective preclinical models, therefore, should be based on a comparable level of complexity. In the past years, there has been a consistent increase in the number of available CCA models. The exploitation of even more complex CCA models is rising. Examples are the use of CRISPR/Cas9 or stabilized organoids for in vitro studies, as well as patient-derived xenografts or transgenic mouse models for in vivo applications. Here, we examine the available preclinical CCA models exploited to investigate: (i) carcinogenesis processes from initiation to progression; and (ii) tools for personalized therapy and innovative therapeutic approaches, including chemotherapy and immune/targeted therapies. For each model, we describe the potential applications, highlighting both its advantages and limits.

Hepatic Overexpression of Soluble Urokinase Receptor (uPAR) Suppresses Diet-Induced Atherosclerosis in Low-Density Lipoprotein Receptor-Deficient (LDLR-/-) Mice

Objective

Atherosclerosis, a chronic inflammatory disease, arises from metabolic disorders and is driven by inappropriate recruitment and proliferation of monocytes / macrophages and vascular smooth-muscle-cells. The receptor for the urokinase-type plasminogen activator (uPAR, Plaur) regulates the proteolytic activation of plasminogen. It is also a coactivator of integrins and facilitates leukocyte-endothelial interactions and vascular smooth-muscle-cell migration. The role of uPAR in atherogenesis remains elusive.

Methods and Results

We generated C57Bl6/J low-density lipoprotein receptor (LDL) and uPAR double knockout (uPAR^-/-/LDLR^-/-) mice to test the role of uPAR in two distinct atherosclerosis models. In LDLR^-/- mice, hepatic overexpression following hydrodynamic transfection of soluble uPAR that competes with endogenous membrane-bound uPAR was performed as an interventional strategy. Aortic root atherosclerotic lesions induced by feeding a high-fat diet were smaller and comprised less macrophages and vascular smooth-muscle-cells in double knockout mice and animals overexpressing soluble uPAR when compared to controls. In contrast, lesion size, lipid-, macrophage-, and vascular smooth muscle cell content of guide-wire-induced intima lesions in the carotid artery were not affected by uPAR deficiency. Adhesion of uPAR^-/--macrophages to TNFα-stimulated endothelial cells was decreased in vitro accompanied by reduced VCAM-1 expression on primary endothelial cells. Hepatic overexpression of soluble full-length murine uPAR in LDLR^-/- mice led to a reduction of diet-induced atherosclerotic lesion formation and monocyte recruitment into plaques. Ex vivo incubation with soluble uPAR protein also inhibited adhesion of macrophages to TNFα-stimulated endothelial cells in vitro.

Conclusion

uPAR-deficiency as well as competitive soluble uPAR reduced diet-promoted but not guide-wire induced atherosclerotic lesions in mice by preventing monocyte recruitment and vascular smooth-muscle-cell infiltration. Soluble uPAR may represent a therapeutic tool for the modulation of hyperlipidemia-associated atherosclerotic lesion formation.

Current progress in the development of a prophylactic vaccine for HIV-1

Since its discovery and characterization in the early 1980s as a virus that attacks the immune system, there has been some success for the treatment of human immunodeficiency virus-1 (HIV-1) infection. However, due to the overwhelming public health impact of this virus, a vaccine is needed urgently. Despite the tireless efforts of scientist and clinicians, there is still no safe and effective vaccine that provides sterilizing immunity. A vaccine that provides sterilizing immunity against HIV infection remains elusive in part due to the following reasons: 1) degree of diversity of the virus, 2) ability of the virus to evade the hosts' immunity, and 3) lack of appropriate animal models in which to test vaccine candidates. There have been several attempts to stimulate the immune system to provide protection against HIV-infection. Here, we will discuss attempts that have been made to induce sterilizing immunity, including traditional vaccination attempts, induction of broadly neutralizing antibody production, DNA vaccines, and use of viral vectors. Some of these attempts show promise pending continued research efforts.

Systemic and mucosal immunization with Candida albicans hsp90 elicits hsp90-specific humoral response in vaginal mucosa which is further enhanced during experimental vaginal candidiasis

The Candida albicans heat shock protein 90 kDa (hsp90-CA) is an important target for protective antibodies in disseminated candidiasis of experimental mice and humans. Hsp90-CA is present in the cell wall of Candida pseudohyphae or hyphae--typical pathogenic morphotypes in both mucosal and systemic Candida infections. However, the potential protective effects of hsp90-CA-specific antibodies in vaginal candidiasis has not yet been reported. In the present study we used various vaccine formulations (recombinant hsp90-CA protein and hsp90-CA-encoding DNA vaccine) and routes of administration (intradermal, intranasal, and intravenous) to induce both hsp90-CA-specific systemic and vaginal mucosa immune responses in experimental BALB/c mice. The results showed that intradermal recombinant hsp90-CA protein priming, followed by intranasal or intradermal recombinant hsp90-CA protein boosting induced significant increases in both serum and vaginal hsp90-CA-specific IgG and IgA antibodies compared to the control group, as well as enhanced hsp90-CA-specific splenocyte responses in vitro. In the intradermally boosted group, subsequent experimental vaginal Candida infection induced additional increases in the hsp90-CA specific IgG isotype, suggesting that Candida has the ability to induce a local hsp90-specific antibody (IgG) response during vulvovaginal candidiasis. Further work is required to elucidate the importance of immunity to highly conserved antigens during infection of the human female reproductive tract where a balance between immunity to and tolerance for commonly antigens such as hsp90 is necessary for the maintenance of fertility.

Delivery of DNA HIV-1 vaccine to the liver induces high and long-lasting humoral immune responses

The quality of immune responses induced by DNA vaccination depends on the site of DNA administration, the expression, and the properties of the encoded antigen. In the present study, we demonstrate that intravenous hydrodynamic HIV-1 envelope DNA injection resulted in high levels of expression of HIV-1 envelope antigen in the liver. When compared to the administration of DNA by i.n., i.d., i.m., and i.splenic routes, hydrodynamic vaccination induced, upon DNA boosting, levels of HIV-1 envelope-specific antibodies 40-fold higher than those elicited by the other routes tested. Hydrodynamic vaccination with 1 microg DNA induced higher humoral responses than 100 microg DNA given intramuscularly in the prime-boost regimen. High levels of envelope-specific IgG and IgA antibodies were induced in genital tract secretions after two doses of DNA followed by intranasal boosting with recombinant HIV-1 gp120 protein. Furthermore, two doses of 100 microg DNA generated interferon-gamma production in approximately 4.3+/-1.7% of CD8(+) splenocytes after in vitro stimulation with HIV-1 envelope peptides. These results demonstrate that DNA vaccines targeted to tissues with high proteosynthetic activity, such as the liver, results in enhanced immune responses.

Differential effects on kidney and liver growth of a non-viral hGH-expression vector in hypophysectomized mice

Non-viral gene transfer was investigated as a potential modality for the treatment of growth hormone deficiency (GHD) using hypophysectomized (Hx) mice as a model. Hx mice were injected with a control plasmid or a plasmid containing the human (h) GH gene driven by a ubiquitin promoter, or left untreated. Treatment with the hGH gene has previously been shown to normalize longitudinal growth and serum insulin-like growth factor I (IGF-I). The present study was conducted to examine the renal/hepatic changes and gene/peptide expression of the GH/IGF-I axis in animals chronically expressing hGH. Following a single hydrodynamic administration of a plasmid DNA containing the hGH gene, a sustained elevation of the circulating hGH level was observed throughout the entire observation period, with a concomitant normalization of circulating IGF-I and IGF-binding protein 3 (IGFBP-3). In addition, longitudinal growth was corrected by normalizing tibia length, tail length, and body weight gain. Interestingly, kidney weights were only partly normalized, whereas kidney glomerular volume and liver weights were fully normalized. Kidney and liver IGF-I protein content was reduced in the Hx mice, but was normalized by hGH treatment. Kidney and liver GH receptor (GHR) mRNA levels were unchanged in the Hx mice, whereas the liver IGF-I mRNA level was reduced in the Hx mice, but was normalized by hGH treatment. We conclude that non-viral hGH gene transfer in Hx mice, which normalizes longitudinal growth and serum IGF-I levels, has differential effects on renal growth and glomerular volume. The potential effects of such excess glomerular growth induced by this intervention require further investigation.

Dlk1/FA1 is a novel endocrine regulator of bone and fat mass and its serum level is modulated by growth hormone

Fat and bone metabolism are two linked processes regulated by several hormonal factors. Fetal antigen 1 (FA1) is the soluble form of dlk1 (delta-like 1), which is a member of the Notch-Delta family. We previously identified FA1 as a negative regulator of bone marrow mesenchymal stem cell differentiation. Here, we studied the effects of circulating FA1 on fat and bone mass in vivo by generating mice expressing high serum levels of FA1 (FA1 mice) using the hydrodynamic-based gene transfer procedure. We found that increased serum FA1 levels led to a significant reduction in total body weight, fat mass, and bone mass in a dose-dependent manner. Reduced bone mass in FA1 mice was associated with the inhibition of mineral apposition rate and bone formation rates by 58 and 72%, respectively. Because FA1 is colocalized with GH in the pituitary gland, we explored the possible modulation of serum FA1 by GH. Serum levels of IGF-I and IGF binding proteins did not change in FA1 mice, whereas increasing serum GH in normal mice using hydrodynamic-based gene transfer procedure dramatically reduced serum FA1 levels by 60%. Conversely, serum FA1 was increased 450% in hypophysectomized mice, and this high level was reduced by 40% during GH treatment. In conclusion, our data identify the FA1 as a novel endocrine factor regulating bone mass and fat mass in vivo, and its serum levels are regulated by GH. FA1 thus provides a novel class of developmental molecules that regulate physiological functions of the postnatal organisms.

Burn injury reveals altered phenotype in mannan-binding lectin-deficient mice

Burn injury destroys skin, the second largest innate immune organ in the body, and triggers chaotic immune and inflammatory responses. The pattern recognition molecule, mannan-binding lectin (MBL), plays an important role in the first-line host defense against infectious agents. MBL initiates the lectin complement pathway and acts as an opsonin. Recent studies suggest that MBL also modulates inflammatory responses. We report that local responses after burn in MBL null mice differ from those found in wild-type (WT) mice in the following important biological markers: spontaneous eschar separation, thinned epidermis and dermis, upregulation of soluble factors including cytokines, chemokines, cell adhesion molecules, a growth factor-binding protein, and matrix metalloproteinases. Mice lacking C1q, C4, or C3 did not show the lack of eschar separation seen in MBL null-burn phenotype. These findings implicate MBL as an important molecule in the maintenance of the homeostatic balance.

Expression of recombination human anti-HBsAg Fab in murine liver

AIM: To evaluate the expression of recombinant and soluble human anti-HBsAg Fab in murine liver.

METHODS: The 5-40 μg recombinant plasmid pXXUF1-HBs-Fab was transfected by hydrodynamics-based administration via tail vein into C57BL/6 mice within 5 s. Meanwhile the empty plasmid transfection group and non-transfection group were established. The serum and tissue samples from liver, kidney and spleen of these mice were collected 3 d after transfection. The expression of genetically engineered Fab antibody in vivo was identified by reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry both at mRNA and protein level.

RESULTS: After transfection with different doses (5, 10, 20 and 40 μg) of pXXUF1-HBs-Fab, the plasma expression of anti-HBsAg Fab was 201.3 ± 13.7, 213.1 ± 13.5, 513.6 ± 12.8 and 954.1 ± 12.7 μg/L, respectively, with specific binding activities to HBsAg protein. There was a postive correlation between the expression of the protein and plasmid dose(r = 0.912, P < 0.01). Meanwhile, the mRNA of Fd and κ chain were detected in liver tissues by RT-PCR. Immunohistochemistry showed brown positive granules in the cytoplasm of liver cells and Fab protein cohered on the inner walls of glomerular capillary lumen and collectors, but the parenchyma cells of the kidney and spleen had no expression of Fd, κ chain and the target protein. The expression of target protein was not observed in both empty plasmid transfection and non-transfection group.

CONCLUSION: The recombinant and soluble human anti-HBsAg Fab can be successfully expressed in mice, and the expression level is increased with the increase of plasmid dose. The above study also shows the Fab protein can be filtrated through glomerular.

Deficiency of mannose-binding lectin greatly increases susceptibility to postburn infection with Pseudomonas aeruginosa

Burn injury disrupts the mechanical and biological barrier that the skin presents against infection by symbionts like the Pseudomonas aeruginosa, a Gram-negative bacteria. A combination of local factors, antimicrobial peptides, and resident effector cells form the initial response to mechanical injury of the skin. This activity is followed by an inflammatory response that includes influx of phagocytes and serum factors, such as complement and mannose-binding lectin (MBL), which is a broad-spectrum pattern recognition molecule that plays a key role in innate immunity. A growing consensus from studies in humans and mice suggests that lack of MBL together with other comorbid factors predisposes the host to infection. In this study we examined whether MBL deficiency increases the risk of P. aeruginosa infection in a burned host. We found that both wild-type and MBL null mice were resistant to a 5% total body surface area burn alone or s.c. infection with P. aeruginosa alone. However, when mice were burned then inoculated s.c. with P. aeruginosa at the burn site, all MBL null mice died by 42 h from septicemia, whereas only one-third of wild-type mice succumbed (p = 0.0005). This result indicates that MBL plays a key role in containing and preventing a systemic spread of P. aeruginosa infection following burn injury and suggests that MBL deficiency in humans maybe a premorbid variable in the predisposition to infection in burn victims.

The hydrodynamics-based procedure for controlling the pharmacokinetics of gene medicines at whole body, organ and cellular levels

Hydrodynamics-based gene delivery, involving a large-volume and high-speed intravenous injection of naked plasmid DNA (pDNA), gives a significantly high level of transgene expression in vivo. This has attracted a lot of attention and has been used very frequently as an efficient, simple and convenient transfection method for laboratory animals. Until recently, however, little information has been published on the pharmacokinetics of the injected DNA molecules and of the detailed mechanisms underlying the efficient gene transfer. We and other groups have very recently demonstrated that the mechanism for the hydrodynamics-based gene transfer would involve, in part, the direct cytosolic delivery of pDNA through the cell membrane due to transiently enhanced permeability. Along with the findings in our series of studies, this article reviews the cumulative reports and other intriguing information on the controlled pharmacokinetics of naked pDNA in the hydrodynamics-based gene delivery. In addition, we describe various applications reported so far, as well as the current attempts and proposals to develop novel gene medicines for future gene therapy using the concept of the hydrodynamics-based procedure. Furthermore, the issues associated with the clinical feasibility of its seemingly invasive nature, which is probably the most common concern about this hydrodynamics-based procedure, are discussed along with its future prospects and challenges.

Hydrodynamic Delivery

Hydrodynamic delivery has emerged as a near-perfect method for intracellular DNA delivery in vivo. For gene delivery to parenchymal cells, only essential DNA sequences need to be injected via a selected blood vessel, eliminating safety concerns associated with current viral and synthetic vectors. When injected into the bloodstream, DNA is capable of reaching cells in the different tissues accessible to the blood. Hydrodynamic delivery employs the force generated by the rapid injection of a large volume of solution into the incompressible blood in the circulation to overcome the physical barriers of endothelium and cell membranes that prevent large and membrane-impermeable compounds from entering parenchymal cells. In addition to the delivery of DNA, this method is useful for the efficient intracellular delivery of RNA, proteins, and other small compounds in vivo. This review discusses the development, current application, and clinical potential of hydrodynamic delivery.

Mannose-binding lectin: laying the stepping stones from clinical research to personalized medicine

As a key component of the complement system, mannose-binding lectin (MBL) is one of the linchpins of innate immunity. It is, therefore, not surprising that MBL2 genetic variants affecting the quantity and activity of the MBL protein in serum have been associated with increased susceptibility to infection and autoimmune diseases, and with poorer prognostic outcomes. This enhanced risk is particularly the case for children and immunosuppressed patients, especially when immunity is further compromised by coexistent primary or secondary immune deficiencies. In several disease areas, such as sepsis, cystic fibrosis, and recurrent childhood infections, the association between low MBL-producing allelic variants and disease risk and/or severity is particularly strong. It is here that the use of MBL testing and replacement therapy has reached the threshold of personalized medicine. The role of MBL in health and disease, advances in MBL testing methodologies and key areas for possible applications of MBL replacement therapy are reviewed.

Disease-associated mutations in human mannose-binding lectin compromise oligomerization and activity of the final protein

Deficiency of human mannose-binding lectin (MBL) caused by mutations in the coding part of the MBL2 gene is associated with increased risk and severity of infections and autoimmunity. To study the biological consequences of MBL mutations, we expressed wild type MBL and mutated MBL in Chinese hamster ovary cells. The normal MBL cDNA (WT MBL-A) was cloned, and the three known natural and two artificial variants were expressed in Chinese hamster ovary cells. When analyzed, WT MBL-A formed covalently linked higher oligomers with a molecular mass of about 300-450 kDa, corresponding to 12-18 single chains or 4-6 structural units. By contrast, all MBL variants formed a dominant band of about 50 kDa, with increasingly weaker bands at 75, 100, and 125 kDa corresponding to two, three, four, and five chains, respectively. In contrast to WT MBL-A, variant MBL formed noncovalent oligomers containing up to six chains (two structural units). MBL variants bound ligands with a markedly reduced capacity compared with WT MBL-A. Mutations in the collagenous region of human MBL compromise assembly of higher order oligomers, resulting in reduced ligand binding capacity and thus reduced capability to activate complement.

Expression of short-chain acyl-CoA dehydrogenase (SCAD) proteins in the liver of SCAD deficient mice after hydrodynamic gene transfer

Hydrodynamic administration of naked DNA was investigated as a method for in vivo expression of variant proteins involved in metabolic diseases, using short-chain acyl-CoA dehydrogenase (SCAD) deficient mice (BALB/cByJ) as a model. Human SCAD wild-type (WT) and two disease-associated SCAD variant proteins (R147W and G185S) were expressed in mouse liver by means of single injections of SCAD cDNA under the control of a ubiquitin promoter. SCAD expression was detected two days after injection. The activity decreased after the first week but continued to be detectable for at least 31 days after injection. Analysis of SCAD WT, R147W, and G185S proteins in liver cells showed that all three SCAD proteins were processed to the mature protein in mitochondria. Concomitantly, the SCAD activity in BALB/cByJ mice injected with SCAD WT, G185S, and R147W cDNA was 30, 39, and 13%, respectively, of the level in normal mice. A tendency to a reduction in the level of butyrylcarnitine in blood was observed although only approximately 5% of the liver cells expressed the SCAD protein. Thus, hydrodynamic gene transfer allows for functional testing of SCAD variant proteins in vivo.

Mannan-binding lectin and its role in innate immunity

Mannan-binding lectin (MBL) is a plasma collectin (C-type lectin with a collagen-like domain) and is considered an important component of innate immunity. Circulating MBL is genetically determined for the major part, but plasma concentration is also markedly influenced by nongenetic factors. The carbohydrate-binding ability of MBL can be inhibited by simple sugars like mannose, fucose and N-acetylglucosamine, but its greatest avidity appears to be for repeating mannose-based structural patterns typical of microbial surfaces. By this means, MBL can bind to a wide variety of bacteria and other microbes, neutralizing them and/or opsonizing them by activating complement using the recently discovered lectin pathway of complement activation. Individual humans differ 1000-fold in MBL concentration, and individuals with low circulating MBL appear to be more vulnerable to infections in a number of clinical settings, especially when combined with secondary immune deficiency. The best evidence that MBL deficiency or insufficiency is physiologically relevant comes from a rapidly expanding literature of clinical studies. MBL insufficiency appears to be a significant risk factor for infections in infants, and for individuals of any age undergoing chemotherapy or post-transplant immunosuppression. Moreover, MBL appears to have a significant influence on the course of certain chronic diseases like rheumatoid arthritis and cystic fibrosis. Replacement therapy with a plasma-derived product is safe and seems promising, while recombinant MBL provides hope for large-scale therapeutic applications. Randomized clinical trials of MBL therapy, which are now on the horizon, should provide unambiguous evidence for the physiological significance of MBL in innate immunity.

Noninvasive gene delivery to the liver by mechanical massage

With the recent completion of the human genome project and the tremendous growth of biotechnology, the desire to extract information concerning gene expression, protein level, subcellular localization, and functionality in the liver will demand the development of efficient gene transfer to this organ with minimal toxicity. In this report, we show that significant gene expression in the liver could be achieved by simple mechanical massage after intravenous injection of naked plasmid DNA into mice. This method is simple, highly reproducible, repeatable, and, more importantly, free of toxicity. Hepatic gene transfer with hepatocyte growth factor (HGF) plasmid DNA prevented endotoxin-induced lethal fulminant hepatic failure, leading to dramatically enhanced survival in mice.

LDL receptor-GFP fusion proteins: new tools for the characterisation of disease-causing mutations in the LDL receptor gene

The function of a series of LDL receptor GFP fusion proteins with different, flexible, unstructured spacer regions was analysed. An optimised version of the fusion protein was used to analyse the effect of an LDL receptor mutation (W556S) found in FH patients and characterised as transport defective. In cultured liver cells this mutation was found to inhibit the transport of LDL receptor GFP fusion protein to the cell surface, thus leading to impaired internalisation of fluorescent labelled LDL. Co-localisation studies confirmed the retention of the mutant protein in the endoplasmic reticulum. Wild type (WT) and W556S LDL receptor GFP fusion proteins were expressed in mouse liver by means of hydrodynamic delivery of naked DNA. Two days after injection liver samples were analysed for GFP fluorescence. The WT LDL receptor GFP protein was located on the cell surface whereas the W556S LDL receptor GFP protein was retained in intracellular compartments. Thus, the GFP-tagged LDL receptor protein allows both detailed time lapse analysis and evaluations in animals for the physiological modelling of mutations. This method should be generally applicable in functional testing of gene products for aberrant processing.