DNA-designed avian IgY antibodies: novel tools for research, diagnostics and therapy

We have recently demonstrated, using the duck Hepatitis B virus (DHBV) model, closely related to human HBV, that following DNA immunization of breeding ducks with a plasmid encoding the targeted protein, specific and biologically active IgY (egg yolk immunoglobulines) are vertically transmitted from their serum into the egg yolk from which they can be extracted and purified. Thus an egg can be considered as a small "factory" for antibody production, since about 60-100 mg of purified IgY can be obtained from each egg yolk of a DNA-immunized duck. One of the major advantages of this new method of "DNA-designed" IgY antibodies is their production via immunization with a gene vector that expresses a corresponding antibody in situ in the cells of an avian host. Therefore this approach allows direct generation of antibodies from plasmid DNA and avoids the costly and tedious preparation of purified antigens required for conventional antibody production. In addition, duck IgY are of remarkable high affinity, avidity and are highly neutralizing. Moreover, the epitope pattern of IgY generated by DNA immunization of ducks is closely related to that observed in viral infection. Such duck IgY are also of particular value as immunodiagnostic tools, since they do not cross-react serologically with mammalian immunoglobulins and complement. Because IgY are resistant to the gastric barrier, the recently described DNA-designed IgY specific to H. pylori Urease B can be of particular interest for passive immunotherapy of gastrointestinal tract infections. Another interesting application is the recent generation in our laboratory of DNA-designed IgY antibodies specific to HBsAg mutants. These antibodies are currently being used to design new diagnostic assay for detection of HBV mutants that are undetectable by actual tests. Moreover, this approach allowing a quick and inexpensive production of a new generation of antibodies will provide pertinent tools to link the fields of genomics and protcomics.

Genetic vaccination for production of DNA-designed antibodies specific to Hepadnavirus envelope proteins

We propose a method of avian antibodies production based on DNA immunization of laying ducks with a plasmid encoding specified antigen, followed by egg collection and purification of egg yolk immunoglobulins (IgY). We have validated this approach in the Duck hepatitis B virus (DHBV) model. We report here that following immunization of female ducks with plasmids encoding DHBV envelope proteins, large amounts (at least 50 mg/egg) of specific antibodies can be obtained from eggs of these ducks. Interestingly, the comparison of different plasmid constructs showed the important differences in their efficacy of specific IgY antibodies induction in the sera and eggs of immunized ducks.

Neuro-glial differentiation of human bone marrow stem cells in vitro

Bone marrow (BM) is a rich source of stem cells and may represent a valid alternative to neural or embryonic cells in replacing autologous damaged tissues for neurodegenerative diseases. The purpose of the present study is to identify human adult BM progenitor cells capable of neuro-glial differentiation and to develop effective protocols of trans-differentiation to surmount the hematopoietic commitment in vitro. Heterogeneous cell populations such as whole BM, low-density mononuclear and mesenchymal stem (MSCs), and several immunomagnetically separated cell populations were investigated. Among them, MSCs and CD90+ cells were demonstrated to express neuro-glial transcripts before any treatment. Several culture conditions with the addition of stem cell or astroblast conditioned media, different concentrations of serum, growth factors, and supplements, used alone or in combinations, were demonstrated to alter the cellular morphology in some cell subpopulations. In particular, MSCs and CD90+ cells acquired astrocytic and neuron-like morphologies in specific culture conditions. They expressed several neuro-glial specific markers by RT-PCR and glial fibrillary acid protein by immunocytochemistry after co-culture with astroblasts, both in the absence or presence of cell contact. In addition, floating neurosphere-like clones have been observed when CD90+ cells were grown in neural specific media. In conclusion, among the large variety of human adult BM cell populations analyzed, we demonstrated the in vitro neuro-glial potential of both the MSC and CD90+ subset of cells. Moreover, unidentified soluble factors provided by the conditioned media and cellular contacts in co-culture systems were effective in inducing the neuro-glial phenotype, further supporting the adult BM neural differentiative capability.

Genetic immunization of ducks for production of antibodies specific to Helicobacter pylori UreB in egg yolks

Following genetic immunization of laying ducks with a plasmid expressing Helicobacter pylori UreB (large subunit of urease), IgY against UreB were obtained from egg yolks. These polyclonal and monospecific IgY antibodies are of higher-titer and specifically recognize recombinant H. pylori urease purified from Escherichia coli. To our knowledge this is the first report describing generation of IgY antibodies directed against antigens of H. pylori by DNA-based immunization.

Sequence-specific inhibition of duck hepatitis B virus reverse transcription by peptide nucleic acids (PNA)

BACKGROUND/AIMS

Peptide nucleic acids (PNAs) appear as promising new antisense agents, that have not yet been examined as hepatitis B virus (HBV) inhibitors. Our aim was to study the ability of PNAs targeting the duck HBV (DHBV) encapsidation signal epsilon to inhibit reverse transcription (RT) and to compare their efficacy with phosphorothioate oligodeoxynucleotides (S-ODNs).

METHODS

The effect of two partly overlapping PNAs targeting epsilon and of analogous S-ODNs was tested in cell-free transcription and translation system for DHBV RT expression. In addition their antiviral effect was investigated in primary duck hepatocytes (PDH).

RESULTS

Both PNAs reproducibly inhibited DHBV RT in a dose-dependent manner with IC(50) of 10nM, whereas up to 600-fold higher concentration of S-ODNs was required for similar inhibition. The PNA targeting the bulge and upper stem of epsilon appeared as more efficient RT inhibitor than the PNA targeting only the bulge. Importantly, the inhibition was highly sequence-specific since double-mismatched PNA had no effect on the RT reaction. Moreover, in PDH the PNA coupled to Arg(7) cationic delivery peptide decreased DHBV replication.

CONCLUSIONS

We provide the first evidence that PNAs targeting the bulge and upper stem of epsilon can efficiently and in a sequence-specific manner inhibit DHBV RT.

Genetic immunization of ducks for production of antibodies specific to Helicobacter pylori UreB in egg yolks

Following genetic immunization of laying ducks with a plasmid expressing Helicobacter pylori UreB (large subunit of urease), IgY against UreB were obtained from egg yolks. These polyclonal and monospecific IgY antibodies are of higher-titer and specifically recognize recombinant H. pylori urease purified from Escherichia coli. To our knowledge this is the first report describing generation of IgY antibodies directed against antigens of H. pylori by DNA-based immunization.

Identification of antigenic regions of duck hepatitis B virus core protein with antibodies elicited by DNA immunization and chronic infection

The induction of humoral response in ducks by DNA-based immunization against duck hepatitis B virus (DHBV) core protein (DHBc) was investigated. In addition, the amino acid specificity of the induced response was compared by using peptide scanning to that elicited either by protein immunization or during chronic DHBV infection. Immunization of ducks with a plasmid expressing DHBc protein led to the induction of a long-lasting antibody response able to specifically recognize viral protein in chronically infected duck livers. Peptide scanning analysis of anti-DHBc response induced during chronic DHBV infection allowed us to identify six major antigenic regions (AR1 to AR6). The reactivity spectrum of duck sera elicited by protein immunization appeared narrower and was restricted to only four of these antigenic regions in spite of higher anti-DHBc antibody titers. Interestingly, anti-DHBc antibodies induced by DNA-based immunization recognized five of six antigenic regions, and the epitope pattern was broader and more closely related to that observed in chronic viral infections. To gain more insight into the location of antigenic regions, we built a three-dimensional (3-D) model of DHBc protein based on human and duck core sequence alignment data and the HBc 3-D crystal structure. The results suggest that two identified antigenic regions (AR2, amino acids [aa] (64)T-P(84), and AR5, aa (183)A-R(210)) are located at positions on the protein surface equivalent to those of the two HBc major epitopes. Moreover, we identified another antigenic region (AR3, aa (99)I-I(112)) that was recognized by all sera from chronically infected, DNA- or protein-immunized ducks within the large 45-aa insertion in DHBc protein, suggesting that this region, which lacks HBc, is externally exposed.

Antiviral effect of adefovir in combination with a DNA vaccine in the duck hepatitis B virus infection model

BACKGROUND/AIMS

Combination of antiviral drugs with immunotherapeutic approaches may be a promising approach for the treatment of chronic hepatitis B. We used the duck HBV (DHBV) infection model to evaluate the efficacy of the combination of adefovir with DNA-immunization by comparison with the respective monotherapies.

METHODS

Pekin ducks chronically infected with DHBV received adefovir treatment alone or in association with intramuscular immunization with a plasmid (pCI-preS/S) expressing the DHBV large envelope protein. Ducks immunized with pCI-preS/S plasmid alone and two control groups receiving empty plasmid injections or no treatment were followed in parallel.

RESULTS

All animals treated with adefovir showed a marked drop in viremia titers during drug administration, followed by a rebound of viral replication after drug withdrawal. Eight weeks after the third DNA boost, the median of viremia within the duck group receiving the combination therapy tended to be lower compared to that of the other groups. In addition, our results suggest a trend to an additive effect of adefovir and DNA vaccine since a 51% decrease in DHBV DNA was observed in autopsy liver samples from combination therapy group, whereas pCI-preS/S or adefovir monotherapies decreased intrahepatic viral DNA by 38 and 14%, respectively. This effect was sustained since it was observed 12 weeks after the end of therapy.

CONCLUSIONS

Our results suggest that combination of adefovir with DNA-vaccine may be able to induce a sustained antiviral effect in vivo.

New hepatitis B virus of cranes that has an unexpected broad host range

All hepadnaviruses known so far have a very limited host range, restricted to their natural hosts and a few closely related species. This is thought to be due mainly to sequence divergence in the large envelope protein and species-specific differences in host components essential for virus propagation. Here we report an infection of cranes with a novel hepadnavirus, designated CHBV, that has an unexpectedly broad host range and is only distantly evolutionarily related to avihepadnaviruses of related hosts. Direct DNA sequencing of amplified CHBV DNA as well a sequencing of cloned viral genomes revealed that CHBV is most closely related to, although distinct from, Ross' goose hepatitis B virus (RGHBV) and slightly less closely related to duck hepatitis B virus (DHBV). Phylogenetically, cranes are very distant from geese and ducks and are most closely related to herons and storks. Naturally occurring hepadnaviruses in the last two species are highly divergent in sequence from RGHBV and DHBV and do not infect ducks or do so only marginally. In contrast, CHBV from crane sera and recombinant CHBV produced from LMH cells infected primary duck hepatocytes almost as efficiently as DHBV did. This is the first report of a rather broad host range of an avihepadnavirus. Our data imply either usage of similar or identical entry pathways and receptors by DHBV and CHBV, unusual host and virus adaptation mechanisms, or divergent evolution of the host genomes and cellular components required for virus propagation.

Progress in DNA vaccine for prophylaxis and therapy of hepatitis B

Increasing lines of evidence suggest that DNA vaccine is of interest to fight chronic hepatitis B virus (HBV) infection. We used the Pekin duck infected by duck HBV (DHBV), closely related to the human virus, which is an attractive model allowing study of protective and therapeutic effectiveness of DNA vaccines against hepatitis B. Immunisation with a plasmid encoding the DHBV large (L) envelope protein induced a strong, specific, highly neutralising and long-lasting anti-preS humoral response in uninfected ducks. Importantly, maternal antibodies elicited by such DNA immunisation were vertically transmitted and protected progeny against viral challenge. Therapeutic immunisation of chronic DHBV-carrier ducks with this plasmid DNA led to the dramatic and sustained decrease in viral replication and even to clearance of intrahepatic viral covalently close circular DNA (cccDNA) pool in some animals. Our recent combination therapy data showed even a more pronounced antiviral effect of DNA vaccine to DHBV envelope protein when associated with antiviral drug (lamivudine) treatment. Therefore, DNA-based vaccine appears as a promising new approach for prophylaxis and therapy of hepatitis B.

Experimental transfection of Macaca sylvanus with cloned human hepatitis B virus

Due to the absence of easily accessible animal models for the study of hepatitis B virus (HBV), the possibility of using Macaca sylvanus, a monkey originating from Morocco, North Africa, was investigated. Three monkeys were intrahepatically inoculated with a replication-competent head-to-tail HBV DNA plasmid dimer construct. The HBV surface antigen and HBV DNA were detected prior to alanine aminotransferase elevation in the serum of two of three HBV-inoculated monkeys at day 2 post-transfection and persisted for several weeks. This indicates that transfected animals developed markers of HBV infection. In addition, electron microscopy of the serum 3 weeks post-transfection showed the presence of virus particles whose shape and size were similar to complete 42 nm HBV Dane particles. Histological examination of liver tissues also revealed pathological changes not observed in uninfected controls, which strongly suggested acute hepatitis. HBV DNA was also detected by PCR in these monkey livers. Taken together, these results indicate that HBV can successfully replicate in this model and that M. sylvanus could be a potentially useful new primate model for the study of HBV replication.

Ultrasound of thyroid, parathyroid glands and neck lymph nodes

In the past 15 years high-frequency B-mode sonography and colour-power Doppler have become the most important and most widely employed imaging modalities for the study of the neck, in particular for thyroid gland, parathyroids and lymph nodes. Sonography allows not only the detection but often also the characterization of the diseases of these organs, distinguishing benign from malignant lesions with high sensitivity and specificity, which could be further improved by the employ of ultrasound contrast agents and harmonic imaging. Although no single sonographic criterion is specific for benign or malignant nature of the lesions, the combination of different signs can be markedly helpful to speed up the diagnostic process. Fine-needle aspiration biopsy (FNAB) remains the most accurate modality for the definitive assessment of thyroid gland nodules and of any doubtful case of nodal disease. In association with clinical findings and serum levels of parathormone, FNAB has specificity close to 100% for the characterization of parathyroid adenomas. A combined approach with sonography and FNAB is generally highly effective.

Percutaneous radio-frequency ablation of hepatic metastases from colorectal cancer: long-term results in 117 patients

PURPOSE

To describe the results of an ongoing radio-frequency (RF) ablation study in patients with hepatic metastases from colorectal carcinoma.

MATERIALS AND METHODS

In 117 patients, 179 metachronous colorectal carcinoma hepatic metastases (0.9-9.6 cm in diameter) were treated with RF ablation by using 17-gauge internally cooled electrodes. Computed tomographic follow-up was performed every 4-6 months. Recurrent tumors were retreated when feasible. Time to new metastases and death for each patient and time to local recurrence for individual lesions were modeled with Kaplan-Meier analysis. Modeling determined the effect of number of metastases on the time to new metastases and death and effect of tumor size on local recurrence.

RESULTS

Estimated median survival was 36 months (95% CI; 28, 52 months). Estimated 1, 2, and 3-year survival rates were 93%, 69%, and 46%, respectively. Survival was not significantly related to number of metastases treated. In 77 (66%) of 117 patients, new metastases were observed at follow-up. Estimated median time until new metastases was 12 months (95% CI; 10, 18 months). Percentages of patients with no new metastases after initial treatment at 1 and 2 years were 49% and 35%, respectively. Time to new metastases was not significantly related to number of metastases. Seventy (39%) of 179 lesions developed local recurrence after treatment. Of these, 54 were observed by 6 months and 67 by 1 year. No local recurrence was observed after 18 months. Frequency and time to local recurrence were related to lesion size (P < or =.001).

CONCLUSION

RF ablation is an effective method to treat hepatic metastases from colorectal carcinoma.

The role of duck hepatitis B virus and aflatoxin B1 in the induction of oxidative stress in the liver

The aim of our study was to use the Pekin duck model to investigate the interactions between hepadnaviral infection and aflatoxin B1 (AFB1) exposure including the role of both factors in the induction of oxidative stress in the liver. AFB1 exposure of duck hepatitis B virus (DHBV) infected Pekin ducks induced a significant increase in viral replication associated with an intense biliary ductular cells proliferation. Interestingly, extremely high levels of AFB1-DNA adducts (40-120 pmol AFB1-Fapy/mg DNA) and AFB1-albumin adducts (1,500-3,000 pg AFB1-lys Eq/mg albumin) were detected in duck liver and serum respectively, as compared to other animal species exposed to a similar AFB1 dose. DHBV infection was found to induce a non-significant increase in AFB1-albumin adduct levels in duck serum. During the treatment duration there was no effect on formation of oxidative base damage within DNA and no effect on oxidative lipid peroxidation following either viral infection or AFB1 exposure. In terms of hepatic antioxidant enzymes (catalase, superoxide dismutase (SOD), glutathione peroxidase) a significant increase in SOD activity occurred following AFB1 exposure, but not DHBV infection, but this was observed only after the cessation of treatment, when biliary ductular cells proliferation was reduced.

Radiofrequency thermal ablation of hepatic metastases

Percutaneous radiofrequency (RF) ablation is a promising therapeutic option for liver metastases, which may result in prolonged survival and chance for cure. Recent technological advancements provide larger coagulation volumes, allowing treatment of medium- and large-size metastases. Candidates are patients with metachronous liver metastases from colorectal or other primary cancers, in whom surgery is contraindicated and with one to four nodules each smaller than approx. 4 cm. We treated 109 patients with 172 colorectal metastases in the liver. Local control was obtained in 70.4% of lesions. Recurrence was significantly more frequent in lesions >3 cm. One major complication occurred (0.6% of sessions), a large bowel perforation requiring surgery. Seven minor complications did not require therapy. New metastases developed at follow-up in 50.4% of patients. Survival rates are 67% and 33% after 2 and 3 years, respectively; estimated median survival being 30 months. RF ablation advantages include minimal-invasiveness (no mortality, significantly lower complications), reduced costs and hospital stays compared to surgery, feasibility in non-surgical candidates, and the potential of repeated treatment if local recurrence occurs or new metastases develop.

Inhibition of hepadnaviral replication by polyethylenimine-based intravenous delivery of antisense phosphodiester oligodeoxynucleotides to the liver

Antisense oligodeoxynucleotides (ODNs) appear as attractive anti-hepatitis B virus (HBV) agents. We investigated in vivo, in the duck HBV (DHBV) infection model, whether linear polyethylenimine (lPEI)-based intravenous delivery of the natural antisense phosphodiester ODNs (O-ODNs) can prevent their degradation and allow viral replication inhibition in the liver. DHBV-infected Pekin ducklings were injected with antisense O-ODNs covering the initiation codon of the DHBV large envelope protein, either in free form (O-ODN-AS2) or coupled to lPEI (lPEI/O-ODN-AS2). Following optimization of lPEI/O-ODN complex formulation, complete O-ODN condensation into a homogenous population of small (20-60 nm) spherical particles was achieved. Flow cytometry analysis showed that lPEI-mediated transfer allowed the intrahepatic delivery of lPEI/O-ODN-AS2 to increase three-fold as compared with the O-ODN-AS2. Following 9-day therapy the intrahepatic levels of both DHBV DNA and RNA were significantly decreased in the lPEI/O-ODN-AS2-treated group as compared with the O-ODN-AS2-treated, control lPEI/O-ODN-treated, and untreated controls. In addition, inhibition of intrahepatic viral replication by lPEI/O-ODN-AS2 was not associated with toxicity and was comparable with that induced by the phosphorothioate S-ODN-AS2 at a five-fold higher dose. Taken together, our results demonstrate that phosphodiester antisense lPEI/O-ODN complexes specifically inhibit hepadnaviral replication. Therefore we provide here the first in vivo evidence that intravenous treatment with antisense phosphodiester ODNs coupled to lPEI can selectively block a viral disease-causing gene in the liver.

Human vasculogenesis ex vivo: embryonal aorta as a tool for isolation of endothelial cell progenitors

SUMMARY

Vasculogenesis, the de novo formation of new blood vessels from undifferentiated precursor cells or angioblasts, has been studied with experimental in vivo and ex vivo animal models, but its mechanism is poorly understood, particularly in humans. We used the aortic ring assay to investigate the angioforming capacity of aortic explants from 11- to 12-week-old human embryos. After being embedded in collagen gels, the aorta rings produced branching capillary-like structures formed by mesenchymal spindle cells that lined a capillary-like lumen and expressed markers of endothelial differentiation (CD31, CD34, von Willebrand factor [vWF], and fms-like tyrosine kinase-1 [Flk-1]/vascular endothelial growth factor receptor 2 [VEGFR2]). The cell linings of these structures showed ultrastructural evidence of endothelial differentiation. The neovascular proliferation occurred primarily in the outer aspects of aortic rings, thus suggesting that the new vessels mainly arose from immature endothelial precursor cells localized in the outer layer of the aortic stroma, ie, a process of vasculogenesis rather than angiogenesis. The undifferentiated mesenchymal cells (CD34+/CD31-), isolated and cultured on collagen-fibronectin, differentiated into endothelial cells expressing CD31 and vWF. Furthermore, the CD34+/CD31+ cells were capable of forming a network of capillary-like structures when cultured on Matrigel. This is the first reported study showing the ex vivo formation of human microvessels by vasculogenesis. Our findings indicate that the human embryonic aorta is a rich source of CD34+/CD31- endothelial progenitor cells (angioblasts), and this information may prove valuable in studies of vascular regeneration and tissue bioengineering.

High incidence of hepatitis B infections among chronic hepatitis cases of unknown aetiology

BACKGROUND/AIMS

In approximately 5% of chronic liver disease cases, no aetiology can be identified. We selected sera from 50 patients with chronic hepatitis of unknown aetiology who were enrolled in this follow-up study whose aim is to gain insight into the possible role of viruses and to define potential clinical outcomes.

METHODS

Patients' sera were screened with highly sensitive polymerase chain reaction assays for hepatitis B (HBV), C, D, and G viruses and TT virus. Sera were also retested for antibodies against the core antigen of HBV.

RESULTS

Surprisingly, HBV DNA was detected in both serum and liver in 15/50 (30%) patients. Immunostaining for HBV antigens on biopsies from patients positive for HBV DNA showed HBcAg and/or HBsAg expression at low levels in 9/15 samples. Eleven of the fifteen patients were anti-HBc positive. With one exception, all patients carried HBV genomes at low levels (10(4) copies/ml or less). Histological signs of chronic liver disease were observed in all patients.

CONCLUSION

Unrecognised HBV infections may account for a high proportion of chronic hepatitis cases of unknown aetiology. Improved HBV detection tests, which appear mandatory for the diagnosis and management of non-A non-E hepatitis as well as for improved safety of transfusions and transplantations are needed.

Isolation and characterization of neural stem cells from the adult human olfactory bulb

We have recently isolated stem cells deriving from the olfactory bulbs of adult patients undergoing particularly invasive neurosurgery. After improving our experimental conditions, we have now obtained neural stem cells according to clonal analysis. The cells can be expanded, established in continuous cell lines and differentiated into the three classical neuronal phenotypes (neurons, astrocytes, and oligodendrocytes). Also, after exposition to leukemia inhibitory factor, we are able to improve the number of neurons, an ideal biological source for transplantation in various neurodegenerative disorders.

Early life humoral response of ducks to DNA immunization against hepadnavirus large envelope protein

DNA vaccination may represent an interesting strategy for early life immunization. However, in some cases, this approach has been shown to induce a tolerance rather than immunity. We have compared the efficiency of neonatal DNA or protein immunization against hepadnavirus envelope protein using the duck hepatitis B virus (DHBV) model. Three-day-old ducklings were immunized with either a plasmid encoding the DHBV pre-S/S large envelope protein (L), or a recombinant preS protein, followed by sequential DNA or protein boosts at weeks 4 and 15. Our results showed that genetic immunization of duck neonates induced specific humoral response to DHBV L protein. Interestingly, an enhanced antibody response was elicited when animals received DNA priming-DNA boosting as compared to DNA priming-protein boosting.