Rise in gamma interferon expression during resolution of duck hepatitis B virus infection

Protection of Ducklings from Duck Hepatitis A Virus Infection with ELPylated Duck Interferon-α

Duck viral hepatitis type I (DVH I) is a lethal disease in ducklings caused by duck hepatitis A virus (DHAV). Although the commercial vaccine is available for vaccination of one-day-old ducklings or breeder ducks, the disease is still prevalent due to the delayed immune response in ducklings and variable maternal antibody levels in breeder duck flocks. To explore the feasibility of duck interferon-α (DuIFN-α) for control of DVH I, DuIFN-α was expressed as an elastin-like polypeptide (ELP) fusion protein (ELP-DuIFN-α) in E. coli and purified by inverse phase transition cycling (ITC). After detection of its cytotoxicity, bioactivity, plasma stability and serum half-life, the protective efficacy of ELP-DuIFN-α against DHAV-1 infection of embryos or ducklings was evaluated using different treatment routes at different infection times. The results show that ELP-DuIFN-α was correctly expressed and purified to more than 90% purity after two cycles of ITC. The purified fusion protein had a specific anti-DHAV-1 activity of 6.0 × 104 IU/mg protein, significantly extended plasma stability and serum half-life without overt cytotoxicity. After allantoic injection with ELP-DuIFN-α pre-infection, co-infection or post-infection with DHAV-1, 5/5, 5/5 or 4/5 embryos survived from the virus challenge. After intramuscular injection or oral administration with ELP-DuIFN-α, 3/5 or 4/5 ducklings survived from co-infection with DHAV-1. After oral administration with ELP-DuIFN-α pre-infection, co-infection or post-infection with DHAV-1, 3/5, 4/5 or 4/5 ducklings survived from the virus challenge, and the relative transcription levels of interferon-stimulated genes were significantly higher than the normal control group and virus challenge control group (p < 0.01). These experimental data suggest that ELP-DuIFN-α can be used as a long-lasting anti-DHAV-1 reagent.

Mechanism of immunosuppression in zebrafish (Danio rerio) spleen induced by environmentally relevant concentrations of perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) has been identified as a new persistent organic pollutant. This pollutant is ubiquitous in water and environments. Although PFOA is toxic to fishes, the precise immunotoxicological mechanism remains unclear. In this study, HPLC-MS analysis proved that PFOA can accumulate in the spleen of zebrafish. As comparison of 7-day and 14-day data, the cumulative content in the spleen significantly increased by 26% even in the 0.1 mg/L PFOA-treated group. Morphological observations revealed that PFOA can damage immune cells in zebrafish spleen by inducing vacuolization, lipofuscin granule production, and mitochondrial swelling. The Toll-like receptor 2 (TLR2)/myeloid differentiation factor 88 (myd88)/NF-κB (P65) pathway can mediate the mRNA expression levels of interferon (IFN) and B cell-activating factor (BAFF); immunoglobulin (Ig) secretion is further regulated. RT-PCR results indicated that the expression levels of P65 and IFN in the 1 mg/L group after PFOA exposure for 7 d increased by 4.03- and 3.28-fold, respectively, in a dose-dependent manner compared with those of the control group. The linear correlation coefficient (r²) was analyzed, and the results indicated that the Ig-mediated pathway can be affected by PFOA. For example, the r² between IgD and P65 decreased from 0.641 (7 d) to 0.295 (14 d) after the cells were exposed to PFOA for a prolonged time; the r² between IgD and IFN increased from 0.562 (7 d) to 0.808 (14 d). The triangle plot method strongly demonstrated that increased PFOA concentration and prolonged exposure to PFOA can inhibit Ig secretion. Therefore, immune organs, particularly the spleen, of zebrafish are vulnerable to PFOA. These results can help to improve the understanding of the possible noncarcinogenic risk mechanisms induced by PFOA.

Simple and visible detection of duck hepatitis B virus in ducks and geese using loop-mediated isothermal amplification

In this study, loop-mediated isothermal amplification (LAMP) was used to establish a rapid, specific, and visual detection method for duck hepatitis B virus (DHBV). The design and synthesis of 4 specific LAMP primers were based on the conserved gene region of the DHBV genome, and the optimum temperature and time of the LAMP reaction were 63°C and 50 min, respectively. The LAMP assay was confirmed to be specific for DHBV detection and had the same sensitivity as the quantitative PCR assay. A visual detection method for rapid determination of results was developed using a color indicator containing phenol red and cresol red. A color change was produced based on a pH change in the reaction system, indicating a positive reaction. For the detection of samples from ducks and geese, the LAMP method has the advantages of simplicity, high sensitivity and specificity, good visibility, and low cost. Moreover, it is more practical and convenient than PCR-related assays for the clinical detection of DHBV.

FTH1 expression is affected by promoter polymorphism and not DNA methylation in response to DHV-1 challenge in duck

Ferritin heavy polypeptide 1 (FTH1) plays a pivotal role in response to viral infections. FTH1 expression is modulated by various pathogens, but the regulatory mechanisms are unknown. We firstly construct duck hepatitis virus 1 (DHV-1) infection model, including morbid ducklings, non-morbid ducklings and control ducklings. Then the mRNA expression of duck FTH1 (duFTH1) was measured mRNA expression of duck FTH1 (duFTH1) in the liver and spleen after duck hepatitis virus 1 (DHV-1) infection using quantitative polymerase chain reaction (qPCR) and found that duFTH1 mRNA was down-regulated significantly in morbid ducklings (liver, P < 0.01; spleen, P < 0.05) compared with the control ducklings. We also found that duFTH1 expression was significantly higher in the spleen (P < 0.01) and liver (P < 0.05) of non-morbid ducklings than in morbid ducklings. Moreover, DNA methylation of the duFTH1 promoter was examined by bisulfite sequencing (BSP) and we found that the duFTH1 promoter was hypomethylated, the relative methylation was only 5.9% and 2.0% in the morbid ducklings and non-morbid ducklings, respectively. The promoter contained a -55 C/T mutation in 75% of non-morbid ducklings, and this polymorphism affected promoter activity. Further analysis suggested that this mutation altered the binding site of the transcription factor NRF1. Binding of NRF1 to the FTH1 promoter was confirmed by electrophoretic mobility shift assay (EMSA) analysis. Thus, our findings revealed the NRF1 was a negative regulator, and lossed of binding of NRF1 to duFTH1 promoter due to -55C/T mutation enhances duFTH1 expression in non-morbid ducks, which provided molecular insights into the effect of duFTH1 expression via promoter polymorphisms, but not DNA methylation, in response to DHV-1 challenge.

Therapeutic Potential of Cell Penetrating Peptides (CPPs) and Cationic Polymers for Chronic Hepatitis B

Chronic hepatitis B virus (HBV) infection remains a major health problem worldwide. Because current anti-HBV treatments are only virostatic, there is an urgent need for development of alternative antiviral approaches. In this context, cell-penetrating peptides (CPPs) and cationic polymers, such as chitosan (CS), appear of particular interest as nonviral vectors due to their capacity to facilitate cellular delivery of bioactive cargoes including peptide nucleic acids (PNAs) or DNA vaccines. We have investigated the ability of a PNA conjugated to different CPPs to inhibit the replication of duck hepatitis B virus (DHBV), a reference model for human HBV infection. The in vivo administration of PNA-CPP conjugates to neonatal ducklings showed that they reached the liver and inhibited DHBV replication. Interestingly, our results indicated also that a modified CPP (CatLip) alone, in the absence of its PNA cargo, was able to drastically inhibit late stages of DHBV replication. In the mouse model, conjugation of HBV DNA vaccine to modified CS (Man-CS-Phe) improved cellular and humoral responses to plasmid-encoded antigen. Moreover, other systems for gene delivery were investigated including CPP-modified CS and cationic nanoparticles. The results showed that these nonviral vectors considerably increased plasmid DNA uptake and expression. Collectively promising results obtained in preclinical studies suggest the usefulness of these safe delivery systems for the development of novel therapeutics against chronic hepatitis B.

Differential innate responses of chickens and ducks to low-pathogenic avian influenza

Ducks and chickens are hosts of avian influenza virus, each with distinctive responses to infection. To understand these differences, we characterized the innate immune response to low-pathogenicity avian influenza virus H7N1 infection in chickens and ducks. Viral RNA was detected in the lungs of chickens from day 0.8 to 7, in ducks mainly at day 4. In both species, viral RNA was detected in the bursa and gut. Infection in chickens resulted in up-regulation of interferon (IFN)-α and IFN-β mRNA, while in the ducks IFN-γ mRNA was strongly up-regulated in the lung and bursa. In chickens and ducks, all investigated pathogen recognition receptor (PRR) mRNAs were up-regulated; however, in the chicken lung Toll-like receptor (TLR)7 and melanoma differentiation-associated protein (MDA)-5 mRNA were strongly induced. TLR3, TLR7 and MDA-5 responses correlated with IFN-α and IFN-β responses in chickens, but in ducks a correlation between IFN-α and TLR7, retinoic acid-inducible gene-I and MDA-5 was absent. We studied the responses of duck and chicken splenocytes to poly(I:C) and R848 analogues to analyse the regulation of PRRs without the interfering mechanisms of the influenza virus. This revealed IFN-α and IFN-γ responses in both species. MDA-5 was only strongly up-regulated in chicken splenocytes, in which time-related PRR responses correlated with the IFN-α and IFN-β response. This correlation was absent in duck splenocytes. In conclusion, chickens and ducks differ in induction of MDA-5, TLR7 and IFN-α mRNA after an influenza virus infection in vivo and after in vitro stimulation with TLR antagonists.

Differences in highly pathogenic avian influenza viral pathogenesis and associated early inflammatory response in chickens and ducks

We studied the immunological responses in the lung, brain and spleen of ducks and chickens within the first 7 days after infection with H7N1 highly pathogenic avian influenza (HPAI). Infection with HPAI caused significant morbidity and mortality in chickens, while in ducks the infection was asymptomatic. The HPAI viral mRNA load was higher in all investigated tissues of chickens compared with duck tissues. In the lung, brain and spleen of HPAI-infected chickens, a high, but delayed, pro-inflammatory response of IL-6 and IL-1β mRNA was induced, including up-regulation of IFN-β, IFN-γ, TLR3 and MDA-5 mRNA from 1 day post infection (p.i.). Whereas in ducks already at 8 h p.i., a quicker but lower response was found for IL-6, IL-1β and iNOS mRNA followed by a delayed activation of TLR7, RIG-I, MDA5 and IFN-γ mRNA response. Virus-infected areas in the lung of chickens co-localized with KUL-01⁺ (macrophages, dendritic cells), CD4⁺, and CD8α⁺ cells, during the first day after infection. However, only KUL-01⁺ cells co-localized with the virus after 1 day p.i. In ducks, CVI-ChNL-68.1⁺ (macrophage-like cells), CD4⁺ and CD8α⁺ cells and apoptosis co-localized with the virus within 8 h p.i. Apoptosis was detected in the brain and lung of HPAI-infected chickens after 2 days p.i. and apoptotic cells co-localized with virus-infected areas. In conclusion, excessive delayed cytokine inflammatory responses but inadequate cellular immune responses may contribute to pathogenesis in chickens, while ducks initiate a fast lower cytokine response followed by the activation of major pattern recognition receptors (TLR7, RIG-I, MDA5) and a persistent cellular response.

In vivo infectivity of liver extracts after resolution of hepadnaviral infection following therapy associating DNA vaccine and cytokine genes

DNA-based vaccination appears of promise for chronic hepatitis B immunotherapy, although there is an urgent need to increase its efficacy. In this preclinical study, we evaluated the therapeutic benefit of cytokine (IL-2, IFN-γ) genes co-delivery with DNA vaccine targeting hepadnaviral proteins in the chronic duck hepatitis B virus (DHBV) infection model. Then, we investigated the persistence of replication-competent virus in the livers of apparently resolved animals. DHBV carriers received four injections of plasmids encoding DHBV envelope and core alone or co-delivered with duck IL-2 (DuIL-2) or duck IFN-γ (DuIFN-γ) plasmids. After long-term (8 months) follow-up, viral covalently closed circular (ccc) DNA was analysed in duck necropsy liver samples. Liver homogenates were also tested for in vivo infectivity in neonatal ducklings. Co-delivery of DuIFN-γ resulted in significantly lower mean viremia starting from week 21. Viral cccDNA was undetectable by conventional methods in the livers of 25% and 57% of animals co-immunized with DuIL-2 and DuIFN-γ, respectively. Interestingly, inoculation of liver homogenates from 7 such apparently resolved animals, exhibiting cccDNA undetectable in Southern blotting and DHBV expression undetectable or restricted to few hepatocytes, revealed that three liver homogenates transmitted high-titre viremia (3-5×10(10) vge/mL) to naïve animals. In conclusion, our results indicate that IFN-γ gene co-delivery considerably enhances immunotherapeutic efficacy of DNA vaccine targeting hepadnaviral proteins. Importantly, we also showed that livers exhibiting only minute amounts of hepadnaviral cccDNA could induce extremely high-titre infection, highlighting the caution that should be taken in occult hepatitis B patients to prevent HBV transmission in liver transplantation context.

Potent inhibition of late stages of hepadnavirus replication by a modified cell penetrating peptide

Cationic cell-penetrating peptides (CPPs) and their lipid domain-conjugates (CatLip) are agents for the delivery of (uncharged) biologically active molecules into the cell. Using infection and transfection assays we surprisingly discovered that CatLip peptides were able to inhibit replication of Duck Hepatitis B Virus (DHBV), a reference model for human HBV. Amongst twelve CatLip peptides we identified Deca-(Arg)₈ having a particularly potent antiviral activity, leading to a drastic inhibition of viral particle secretion without detectable toxicity. Inhibition of virion secretion was correlated with a dose-dependent increase in intracellular viral DNA. Deca-(Arg)₈ peptide did neither interfere with DHBV entry, nor with formation of mature nucleocapsids nor with their travelling to the nucleus. Instead, Deca-(Arg)₈ caused envelope protein accumulation in large clusters as revealed by confocal laser scanning microscopy indicating severe structural changes of preS/S. Sucrose gradient analysis of supernatants from Deca-(Arg)₈-treated cells showed unaffected naked viral nucleocapsids release, which was concomitant with a complete arrest of virion and surface protein-containing subviral particle secretion. This is the first report showing that a CPP is able to drastically block hepadnaviral release from infected cells by altering late stages of viral morphogenesis via interference with enveloped particle formation, without affecting naked nucleocapsid egress, thus giving a view inside the mode of inhibition. Deca-(Arg)₈ may be a useful tool for elucidating the hepadnaviral secretory pathway, which is not yet fully understood. Moreover we provide the first evidence that a modified CPP displays a novel antiviral mechanism targeting another step of viral life cycle compared to what has been so far described for other enveloped viruses.

In vivo electroporation improves therapeutic potency of a DNA vaccine targeting hepadnaviral proteins

This preclinical study investigated the therapeutic efficacy of electroporation (EP)-based delivery of plasmid DNA (pDNA) encoding viral proteins (envelope, core) and IFN-γ in the duck model of chronic hepatitis B virus (DHBV) infection. Importantly, only DNA EP-therapy resulted in a significant decrease in mean viremia titers and in intrahepatic covalently closed circular DNA (cccDNA) levels in chronic DHBV-carrier animals, compared with standard needle pDNA injection (SI). In addition, DNA EP-therapy stimulated in all virus-carriers a humoral response to DHBV preS protein, recognizing a broader range of major antigenic regions, including neutralizing epitopes, compared with SI. DNA EP-therapy led also to significant higher intrahepatic IFN-γ RNA levels in DHBV-carriers compared to other groups, in the absence of adverse effects. We provide the first evidence on DNA EP-therapy benefit in terms of hepadnaviral infection clearance and break of immune tolerance in virus-carriers, supporting its clinical application for chronic hepatitis B.

CpG oligodeoxynucleotides containing GACGTT motifs enhance the immune responses elicited by a goose parvovirus vaccine in ducks

Recombinant parvovirus VP2 (rVP2) was formulated with different types of adjuvant, including aluminum adjuvant and CpG oligodeoxynucleotides (ODNs), and the immunological responses after vaccination in ducks were examined. In comparison with the control group, production of rVP2-specific antibodies, expression of cytokines in peripheral blood mononuclear cells (PBMC) stimulated by rVP2, and percentage of CD4(+)/CD8(+) cells in PBMC were significantly increased in ducks immunized with rVP2 formulated with CpG ODNs containing 3 copies of GACGTT motif. CpG ODNs with GACGTT motifs might be used to improve the efficacy of vaccines for ducks.

The persistence in the liver of residual duck hepatitis B virus covalently closed circular DNA is not dependent upon new viral DNA synthesis

Residual hepatitis B virus (HBV) DNA can be detected following the resolution of acute HBV infection. Our previous work using duck hepatitis B virus (DHBV) infected ducks, indicated that ~80% of residual DHBV DNA in the liver is in the covalently closed circular DNA (cccDNA) form, suggesting that viral DNA synthesis is suppressed. The current study asked more directly if maintenance of residual DHBV cccDNA is dependent upon ongoing viral DNA synthesis. Ducks that recovered from acute DHBV infection were divided into 2 groups and treated with the antiviral drug, Entecavir (ETV), or placebo. No major differences in the stability of cccDNA or levels of residual cccDNA were observed in liver biopsy tissues taken 95 days apart from ETV treated and placebo control ducks. The data suggest that residual DHBV cccDNA is highly stable and present in a cell population with a rate of turnover similar to normal, uninfected hepatocytes.

The early host innate immune response to duck hepatitis B virus infection

The early phase after hepatitis B virus infection could play a crucial role in clearance and/or persistence of the virus, particularly in neonates. This work compared the early phase of duck hepatitis B virus infection in 1-day-old (D1) and 28-day-old (D28) ducks to determine whether differences in viral or host innate immune response can be related to the difference in outcome. In the first phase, almost immediately after inoculation, virus was taken up by components of the reticulo-endothelial systems, particularly liver-specific macrophages, Kupffer cells. Very early after infection, the induction of alpha interferon by infected hepatocytes occurred and was rapidly reinforced by recruitment of effector lymphocytes, which directly or indirectly caused apoptosis, eliminating infected hepatocytes, as was seen in mature birds. In addition, a lack of lymphocytic infiltration of the liver was found in D1 ducks, which supports the suggestion that the innate immune network is less effective in D1 ducks. Taken together, these results suggest that failure of the co-ordinated innate immune response rather than a defect in induced antiviral cell-mediated immunity may be the key factor which makes baby ducks vulnerable to persistence of hepadnavirus infection.

DNA vaccination in combination or not with lamivudine treatment breaks humoral immune tolerance and enhances cccDNA clearance in the duck model of chronic hepatitis B virus infection

This study used a duck hepatitis B virus (DHBV) model to evaluate whether a novel DNA vaccination protocol alone or associated with antiviral (lamivudine) treatment was able to clear the intrahepatic covalently closed, circular viral DNA (cccDNA) pool responsible for persistence of infection. DHBV carriers received DNA vaccine (on weeks 6, 10, 13, 14, 28 and 35) targeting the large envelope and/or core proteins alone or combined with lamivudine treatment (on weeks 1-8) or lamivudine monotherapy. After 10 months of follow-up, a dramatic decrease in viraemia and liver DHBV cccDNA (below 0.08 cccDNA copies per cell) was observed in 9/30 ducks (30 %) receiving DNA mono- or combination therapy, compared with 0/12 (0 %) from lamivudine monotherapy or the control groups, suggesting a significant antiviral effect of DNA immunization. However, association with the drug did not significantly improve DHBV DNA vaccine efficacy (33 % cccDNA clearance for the combination vs 27 % for DNA monotherapy), probably due to the low antiviral potency of lamivudine in the duck model. Seroconversion to anti-preS was observed in 6/9 (67 %) ducks showing cccDNA clearance, compared with 1/28 (3.6 %) without clearance, suggesting a significant correlation (P<0.001) between humoral response restoration and cccDNA elimination. Importantly, an early (weeks 10-12) drop in viraemia was observed in seroconverted animals, and virus replication did not rebound following the cessation of immunotherapy, indicating a sustained effect. This study provides the first evidence that therapeutic DNA vaccination is able to enhance hepadnaviral cccDNA clearance, which is tightly associated with a break in humoral immune tolerance. These results also highlight the importance of antiviral drug potency and an effective DNA immunization protocol for the design of therapeutic vaccines against chronic hepatitis B.