DNA immunization with fusion of CTLA-4 to hepatitis B virus (HBV) core protein enhanced Th2 type responses and cleared HBV with an accelerated kinetic

Contriving a novel of CHB therapeutic vaccine based on IgV_CTLA-4 and L protein via immunoinformatics approach

Chronic infection induced by immune tolerance to hepatitis B virus (HBV) is one of the most common causes of hepatic cirrhosis and hepatoma. Fortunately, the application of therapeutic vaccine can not only reverse HBV-tolerance, but also serve a potentially effective therapeutic strategy for treating chronic hepatitis B (CHB). However, the clinical effect of the currently developed CHB therapeutic vaccine is not optimistic due to the weak immunogenicity. Given that the human leukocyte antigen CTLA-4 owns strong binding ability to the surface B7 molecules (CD80 and CD86) of antigen presenting cell (APCs), the immunoglobulin variable region of CTLA-4 (IgV_CTLA-4) was fused with the L protein of HBV to contrive a novel therapeutic vaccine (V_C4HBL) for CHB in this study. We found that the addition of IgV_CTLA-4 did not interfere with the formation of L protein T cell and B cell epitopes after analysis by means of immunoinformatics approaches. Meanwhile, we also found that the IgV_CTLA-4 had strong binding force to B7 molecules through molecular docking and molecular dynamics (MD) simulation. Notably, our vaccine V_C4HBL showed good immunogenicity and antigenicity by in vitro and in vivo experiments. Therefore, the V_C4HBL is promising to again effectively activate the cellular and humoral immunity of CHB patients, and provides a potentially effective therapeutic strategy for the treatment of CHB in the future.Communicated by Ramaswamy H. Sarma.

Bioinformatics-based design of a fusion vaccine with CTLA-4 variable region to combat Brucella

Brucellosis has become a global zoonotic disease, seriously endangering the health of people all over the world. Vaccination is an effective strategy for protection against Brucella infection in livestock in developed countries. However, current vaccines are pathogenic to humans and pregnant animals, which limits their use. Therefore, it is very important to improve the safety and immune protection of Brucella vaccine. In this study, different bioinformatics approaches were carried out to predict the physicochemical properties, T/B epitope, and tertiary structure of Omp2b and Omp31. Then, these two proteins were sequentially linked, and the Cytotoxic T lymphocyte associated antigen-4 (CTLA-4) variable region was fused to the N-terminal of the epitope sequence. In addition, molecular docking was performed to show that the structure of the fusion protein vaccine had strong affinity with B7 (B7-1, B7-2). This study showed that the designed vaccine containing CTLA-4 had high potency against Brucella, which could provide a reference for the future development of efficient brucellosis vaccines.

Nucleotides Entrapped in Liposome Nanovesicles as Tools for Therapeutic and Diagnostic Use in Biomedical Applications

The use of nucleotides for biomedical applications is an old desire in the scientific community. As we will present here, there are references published over the past 40 years with this intended use. The main problem is that, as unstable molecules, nucleotides require some additional protection to extend their shelf life in the biological environment. Among the different nucleotide carriers, the nano-sized liposomes proved to be an effective strategic tool to overcome all these drawbacks related to the nucleotide high instability. Moreover, due to their low immunogenicity and easy preparation, the liposomes were selected as the main strategy for delivery of the mRNA developed for COVID-19 immunization. For sure this is the most important and relevant example of nucleotide application for human biomedical conditions. In addition, the use of mRNA vaccines for COVID-19 has increased interest in the application of this type of technology to other health conditions. For this review article, we will present some of these examples, especially focused on the use of liposomes to protect and deliver nucleotides for cancer therapy, immunostimulatory activities, enzymatic diagnostic applications, some examples for veterinarian use, and the treatment of neglected tropical disease.

Genetic immunization against hepatitis B virus with calcium phosphate nanoparticles in vitro and in vivo

Calcium phosphate nanoparticles were loaded with plasmid DNA and toll-like receptor ligands (TLR), i.e. CpG or flagellin, to activate antigen-presenting cells (APCs) like dendritic cells (DCs). The functionalized nanoparticles were studied in vitro on HeLa, C2C12 and BHK-21 cell lines, focusing on the expression of two specific proteins. EGFP-DNA, encoding for enhanced green fluorescent protein (EGFP), was used as a model plasmid to optimize the transfection efficiency in vitro by fluorescence microscopy and flow cytometry. Calcium phosphate nanoparticles loaded with TLR ligands and plasmid DNA encoding for the hepatitis B virus surface antigen (pHBsAg) were evaluated by in vitro and in vivo immunization experiments to identify a possible candidate for a prophylactic hepatitis B virus (HBV) vaccine. The nanoparticles induced a strong expression of HBsAg in the three cell lines. In splenocytes, the expression of the co-stimulatory molecules CD80 and CD86 was enhanced. After intramuscular injection in mice, the nanoparticles induced the expression of HBsAg, the antigen-specific T cell response, and the antigen-specific antibody response (IgG1). STATEMENT OF SIGNIFICANCE: Hepatitis B is one of the most frequent viral infections worldwide. For preventive immunization, nanoparticles can be used which carry both an adjuvant (a stimulatory molecule) and DNA encoding for a viral antigen. After administration of such nanoparticles to cells, they are taken up by cells where the DNA is transcribed into the viral antigen (a protein). This viral antigen is inducing a virus-specific immune response. This was shown both by in vitro cell culture as well as by an extensive in vivo study in mice.

Identification of key genes and pathways associated with different immune statuses of hepatitis B virus infection

We aimed to identify key genes and pathways associated with different immune statuses of hepatitis B virus (HBV) infection. The gene expression and DNA methylation profiles were analysed in different immune statuses of HBV infection. Differentially expressed genes (DEGs) and differentially methylated genes (DMGs) were identified, followed by their functional and integrative analyses. The differential expression of IgG Fc receptors (FcγRs) in chronic HBV-infected patients and immune cells during different stages of HBV infection was investigated. Toll-like receptor (TLR) signalling pathway (including TLR6) and leucocyte transendothelial migration pathway (including integrin subunit beta 1) were enriched during acute infection. Key DEGs, such as FcγR Ib and FcγR Ia, and interferon-alpha inducible protein 27 showed correlation with alanine aminotransferase levels, and they were differentially expressed between acute and immune-tolerant phases and between immune-tolerant and immune-clearance phases. The integrative analysis of DNA methylation profile showed that lowly methylated and highly expressed genes, including cytotoxic T lymphocyte-associated protein 4 and mitogen-activated protein kinase 3 were enriched in T cell receptor signalling pathway during acute infection. Highly methylated and lowly expressed genes, such as Ras association domain family member 1 and cyclin-dependent kinase inhibitor 2A were identified in chronic infection. Furthermore, differentially expressed FcγR Ia, FcγR IIa and FcγR IIb, CD3- CD56+ CD16+ natural killer cells and CD14high CD16+ monocytes were identified between immune-tolerant and immune-clearance phases by experimental validation. The above genes and pathways may be used to distinguish different immune statuses of HBV infection.

HBV antigen and DNA loss from mouse serum is associated with novel vaccine-induced HBV surface antigen-specific cell-mediated immunity and cytokine production

Therapeutic vaccination is a promising strategy for controlling chronic hepatitis B virus (HBV). Here, we tested whether several novel vaccination strategies could be used to induce HBV-specific adaptive immune responses and control/eradicate HBV in a mouse model. Robust HBV antigen-specific antibody responses were elicited by several vaccination strategies using a novel particle vaccine (HBSS1), which expresses a fusion of the S (amino acids [aa] 1-223) and preS1 (aa 21-47) antigens, and/or a recombinant adenovirus rAdSS1 vaccine. However, antigen-specific cell-mediated immunity and high levels of production of multiple cytokines were elicited only by heterologous prime-boost immunization; i.e., priming with the HBSS1 vaccine followed by a rAdSS1 boost. Furthermore, the most rapid loss of serum HBsAg, HBeAg and DNA was achieved by the novel vaccination regimen (priming with HBSS1 formulated with adjuvants [alum plus PolyI:C]), which was strongly associated with more potent and functional HBsAg-specific CD4⁺ and CD8⁺ T-cell responses and increased production of interleukin (IL)-2, interferon (IFN)-γ, tumor necrosis factor-α, IL-12, and IFN-γ-induced protein (IP)-10. Thus, our novel heterogeneous prime-boost vaccine regimen shows promise as a therapeutic strategy against HBV.

CTLA‑4 interferes with the HBV‑specific T cell immune response (Review)

Hepatitis B virus (HBV) infection is a major cause of hepatic inflammation. Successful HBV clearance in patients is associated with sustained viral control by effector T cells. Compared with acute hepatitis B, chronic HBV infection is associated with the depletion of T cells, resulting in weak or absent virus-specific T cells reactivity, which is described as 'exhaustion'. This exhaustion is characterized by impaired cytokine production and sustained expression of multiple coinhibitory molecules. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is one of many coinhibitory molecules that can attenuate T cell activation by inhibiting costimulation and transmitting inhibitory signals to T cells. Persistent HBV infection results in the upregulation of CTLA-4 on hepatic CD8⁺ T cells. This prompts CD8⁺ T cell apoptosis, and the activation of cytotoxic T lymphocytes is blocked. Similar to CD8⁺ T cells, CD4⁺ T helper (Th) cell proliferation is hindered following CTLA-4 upregulation. In addition, the differentiation of CD4⁺ Th is polarized toward the Th2/peripherally-inducible T regulatory cell types, increasing the levels of anti-inflammatory cytokines. Conversely, the activation of proinflammatory cells (Th1 and follicular helper T) is blocked, and the levels of proinflammatory cytokines decline. This review summarizes the current literature relevant to T cell exhaustion in patients with HBV-related chronic hepatitis, and discusses the roles of CTLA-4 in T cell exhaustion.

Therapeutic DNA Vaccines for Human Papillomavirus and Associated Diseases

Human papillomavirus (HPV) has long been recognized as the causative agent of cervical cancer. High-risk HPV types 16 and 18 alone are responsible for over 70% of all cases of cervical cancers. More recently, HPV has been identified as an etiological factor for several other forms of cancers, including oropharyngeal, anogenital, and skin. Thus, the association of HPV with these malignancies creates an opportunity to control these HPV lesions and HPV-associated malignancies through immunization. Strategies to prevent or to therapeutically treat HPV infections have been developed and are still pushing innovative boundaries. Currently, commercial prophylactic HPV vaccines are widely available, but they are not able to control established infections or lesions. As a result, there is an urgent need for the development of therapeutic HPV vaccines, to treat existing infections, and to prevent the development of HPV-associated cancers. In particular, DNA vaccination has emerged as a promising form of therapeutic HPV vaccine. DNA vaccines have great potential for the treatment of HPV infections and HPV-associated cancers due to their safety, stability, simplicity of manufacturability, and ability to induce antigen-specific immunity. This review focuses on the current state of therapeutic HPV DNA vaccines, including results from recent and ongoing clinical trials, and outlines different strategies that have been employed to improve their potencies. The continued progress and improvements made in therapeutic HPV DNA vaccine development holds great potential for innovative ways to effectively treat HPV infections and HPV-associated diseases.

Hepatitis B virus core protein promotes hepatocarcinogenesis by enhancing Src expression and activating the Src/PI3K/Akt pathway

Hepatitis B virus core protein (HBc) is expressed preferentially in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC). HBc can function as an oncogene arising from its gene regulatory properties, but how it contributes functionally to hepatocarcinogenesis remains unclear. In this study, we determined the molecular and functional roles of HBc during HBV-associated hepatocellular tumorigenesis. HBc increased tumor formation of hepatoma cells. Moreover, expression of HBc specifically promoted proliferation of hepatoma cells in vitro. Mechanistic investigations revealed that these effects were caused by activation of the Src/PI3K/Akt pathway through proximal switch from inactive Src to the active form of the kinase by HBc. HBc-mediated sarcoma (Src) kinase activation was associated with down-regulation of C-terminal Src kinase (Csk). In addition, HBc enhances Src expression by activation of alternative Src 1A promoter in an Sp1 transcription factor-dependent manner. Proliferation induced by stable HBc expression was associated with increased G₁-S cell cycle progression mediated by Src kinase activation. HBc-induced cellular proliferation and tumor formation were reversed by administration of the Src inhibitor saracatinib. Together, our findings suggest that HBc promotes tumorigenesis of hepatoma cells by enhancing the expression of total Src and the active form of the kinase and subsequently activates Src/PI3K/Akt signaling pathway, revealing novel insights into the underlying mechanisms of HBV-associated hepatocarcinogenesis.-Liu, W., Guo, T.-F., Jing, Z.-T., Yang, Z., Liu, L., Yang, Y.-P., Lin, X., Tong, Q.-Y. Hepatitis B virus core protein promotes hepatocarcinogenesis by enhancing Src expression and activating the Src/PI3K/Akt pathway.

Antitumor immunity of DNA vaccine based on CTLA-4 fused with HER2 against colon carcinoma

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) negatively regulates the T cell activation and competes with CD28 in binding with B7.1/B7.2 molecules. Fusion of the extracellular region of CTLA-4 and a specific antigen is an effective method for improving the immune efficacy of DNA vaccines. This study aimed to investigate the effects of DNA vaccine of human epidermal growth factor receptor-2 (HER2) fused with CTLA-4 on the development of colon carcinoma in mice and to identify the potential immune mechanisms underlying its effects. We constructed recombinant plasmids corresponding to the control group, individual antigen group, and fusion antigen group. Then, mice were intramuscularly injected with the corresponding plasmids and exposed to electrical pulses. Immunogenicity was evaluated at 2 weeks after the last immunization. Furthermore, to investigate the antitumor immune effects of the recombinant plasmid, we established a mouse model of HER2 expression in transplanted tumors. Experimental results showed that the recombinant plasmids expressing fusion antigen induced a stronger cellular immune response. Inoculation of the HER2-CTLA-4 plasmid exerted the strongest inhibitory effect on HER2 expression-mediated tumor growth in mice. These results highlight the potential of the CTLA-4 fusion DNA vaccine as a therapeutic vaccine against colon cancer based on HER2 and CTLA-4.

Single dose HBsAg CS-γ-PGA nanogels induce potent protective immune responses against HBV infection

Hepatitis B virus (HBV) infection is a severe threat to public health, which can be prevented by prophylactic vaccination. Here, we tested nanogels carriers in the prophylactic effect of hepatitis B surface antigen (HBsAg) vaccine. HBsAg nanogels (Ng) were prepared using chitosan (CS) and poly-γ-glutamic acid (γ-PGA). Positively charged Ng (+) and negatively charged Ng (-) were prepared by adjusting the CS and γ-PGA proportion. Dendritic cells (DCs) maturation in mice immunized with HBsAg Ng (+) and HBsAg Ng (-) could be augmented in response to pAAV/HBV1.2 plasmid challenge. Single-dose immunization with HBsAg Ng (+) induced HBsAg specific-antibodies. HBsAg Ng (+) immunized mice cleared HBsAg and restored anti-HBs production after pAAV/HBV1.2 plasmid challenge. Single-dose HBsAg Ng (+) induced humoral and cellular immunity, and could induce effector memory T cells. Single-dose HBsAg Ng (-) favored the induction of cellular immunity, and induced central memory T cells and effector memory T cells. However, HBsAg elimination was similar between HBsAg Ng (+)- and HBsAg Ng (+) plus HBsAg Ng (-)-immunized mice. Zeta potential measurements showed that HBsAg Ng (+) were more stable than HBsAg Ng (-). Therefore, Ng (+) are desirable HBsAg prophylactic vaccine carriers, providing long-term protection against HBV, and are a good choice to study and apply weakly immunostimulatory antigens.

The dose of HBV genome contained plasmid has a great impact on HBV persistence in hydrodynamic injection mouse model

Background

Hydrodynamic injection (HI) of hepatitis B virus (HBV) mouse model is an useful tool for HBV related research in vivo. However, only 40% of C57/BL6 mice injected with 10 μg HBV genome contained plasmid (pAAV-HBV1.2), serum HBsAg more than 6 months and none of the BALB/c mice injected with 10 μg pAAV-HBV1.2 plasmid DNA, serum HBsAg positive more than 4 weeks in the previous study.

Methods

In this study, C57/BL6 and BALB/c mice were hydrodynamic injected with different doses of pAAV-HBV1.2 plasmid DNA. HBV related serum markers were detected by ELISA. ALT levels in the serum were measured using full automated biochemistry analyzer. HBcAg positive cells in the liver were detected by immunohistochemical staining. The mRNA levels of IRF3, ISGs including ISG15, OAS, PKR and immune factors including IFNγ, TNFα, TGFβ, IL-6, IL-10, PDL1 in liver of the mice were quantified by qRT-PCR.

Results

The results showed that the mice injected with 100 μg high-concentration or 1 μg low-concentration of pAAV-HBV1.2 plasmid DNA did not excert dominant influence on HBV persistence. In contrast, injection of 5 μg intermediate-dose of pAAV-HBV1.2 plasmid DNA led to significant prolonged HBsAg expression and HBV persistence in both C57/BL6 (80% of the mice with HBsAg positive more than 6 months) and BALB/c (60% of the mice with HBsAg positive more than 3 months) mice. IFNγ was significant up-regulated in liver of the mice injected with 1 μg or 100 μg pAAV-HBV1.2 plasmid DNA. TNFα was up-regulated significantly in liver of the mice injected with 100 μg pAAV-HBV1.2 plasmid DNA. Moreover, PDL1 was significant up-regulated in liver of the mice injected with 5 μg pAAV-HBV1.2 plasmid DNA.

Conclusion

In this paper we demonstrated that, in the HBV HI mouse model, the concentration of injected pAAV-HBV1.2 plasmid DNA contributes to the diverse kinetics of HBsAg and HBeAg in the serum as well as HBcAg expression level in the liver, which then determined the HBV persisternce, while the antiviral factors IFNγ, TNFα as well as immune negative regulatory factor PDL1 play important roles on HBV persistence.

The IL-1R/TLR signaling pathway is essential for efficient CD8+ T-cell responses against hepatitis B virus in the hydrodynamic injection mouse model

The outcome of hepatitis B viral (HBV) infection is determined by the complex interactions between replicating HBV and the immune system. While the role of the adaptive immune system in the resolution of HBV infection has been studied extensively, the contribution of innate immune mechanisms remains to be defined. Here we examined the role of the interleukin-1 receptor/Toll-like receptor (IL-1R/TLR) signaling pathway in adaptive immune responses and viral clearance by exploring the HBV mouse model. Hydrodynamic injection with a replication-competent HBV genome was performed in wild-type mice (WT) and a panel of mouse strains lacking specific innate immunity component expression. We found higher levels of HBV protein production and replication in Tlr2^−/−, Tlr23479^−/−, 3d/Tlr24^−/−, Myd88/Trif^−/− and Irak4^−/− mice, which was associated with reduced HBV-specific CD8⁺ T-cell responses in these mice. Importantly, HBV clearance was delayed for more than 2 weeks in 3d/Tlr24^−/−, Myd88/Trif^−/− and Irak4^−/− mice compared to WT mice. HBV-specific CD8⁺ T-cell responses were functionally impaired for producing the cytokines IFN-γ, TNF-α and IL-2 in TLR signaling-deficient mice compared to WT mice. In conclusion, the IL-1R/TLR signaling pathway might contribute to controlling HBV infection by augmenting HBV-specific CD8⁺ T-cell responses.

Ceruloplasmin inhibits the production of extracellular hepatitis B virions by targeting its middle surface protein

Ceruloplasmin (CP) is mainly synthesized by hepatocytes and plays an essential role in iron metabolism. Previous reports have shown that CP levels correlate negatively with disease progression in patients with chronic hepatitis B. However, the function of CP in the hepatitis B virus (HBV) life cycle and the mechanism underlying the above correlation remain unclear. Here, we report that CP can selectively inhibit the production of extracellular HBV virions without altering intracellular viral replication. HBV expression can also downregulate the expression of CP. Knockdown of CP using small interfering RNA significantly increased the level of extracellular HBV virions in both Huh7 and HepG2.2.15 cells, while overexpression of CP decreased this level. Mechanistically, CP could specifically interact with the HBV middle surface protein (MHB). Using an HBV replication-competent clone unable to express MHBs, we demonstrated that the overexpression of CP did not affect the production of extracellular HBV virions in the absence of MHBs. Furthermore, introduction of an MHB expression construct could rescue the impairment in virion production caused by CP. Taken together, our results suggest that CP may be an important host factor that targets MHBs during the envelopment and/or release of virions.

PreC and C Regions of Woodchuck Hepatitis Virus Facilitate Persistent Expression of Surface Antigen of Chimeric WHV-HBV Virus in the Hydrodynamic Injection BALB/c Mouse Model

In the hydrodynamic injection (HI) BALB/c mouse model with the overlength viral genome, we have found that woodchuck hepatitis virus (WHV) could persist for a prolonged period of time (up to 45 weeks), while hepatitis B virus (HBV) was mostly cleared at week four. In this study, we constructed a series of chimeric genomes based on HBV and WHV, in which the individual sequences of a 1.3-fold overlength HBV genome in pBS-HBV1.3 were replaced by their counterparts from WHV. After HI with the WHV-HBV chimeric constructs in BALB/c mice, serum viral antigen, viral DNA (vDNA), and intrahepatic viral antigen expression were analyzed to evaluate the persistence of the chimeric genomes. Interestingly, we found that HI with three chimeric WHV-HBV genomes resulted in persistent antigenemia in mice. All of the persistent chimeric genomes contained the preC region and the part of the C region encoding the N-terminal 1–145 amino acids of the WHV genome. These results indicated that the preC region and the N-terminal part of the C region of the WHV genome may play a role in the persistent antigenemia. The chimeric WHV-HBV genomes were able to stably express viral antigens in the liver and could be further used to express hepadnaviral antigens to study their pathogenic potential.

Construction of a fusion plasmid containing the PSCA gene and cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) and its anti-tumor effect in an animal model of prostate cancer

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is a negative regulator of T cell activation, which competes with CD28 for B7.1/B7.2 binding, and which has a greater affinity. Fusion of specific antigens to extracellular domain of CTLA4 represents a promising approach to increase the immunogenicity of DNA vaccines. In this study, we evaluated this interesting approach for CTLA4 enhancement on prostate stem cell antigen (PSCA)-specific immune responses and its anti-tumor effects in a prostate cancer mouse model. Consequently, we constructed a DNA vaccine containing the PSCA and the CTLA-4 gene. Vaccination with the CTLA4-fused DNA not only induced a much higher level of anti-PSCA antibody, but also increased PSCA-specific T cell response in mice. To evaluate the anti-tumor efficacy of the plasmids, murine models with PSCA-expressing tumors were generated. After injection of the tumor-bearing mouse model, the plasmid carrying the CTLA4 and PSCA fusion gene showed stronger inhibition of tumor growth than the plasmid expressing PSCA alone. These observations emphasize the potential of the CTLA4-fused DNA vaccine, which could represent a promising approach for tumor immunotherapy.

Characterization of the Treg Response in the Hepatitis B Virus Hydrodynamic Injection Mouse Model

Regulatory T cells (Tregs) play an important role in counter-regulating effector T cell responses in many infectious diseases. However, they can also contribute to the development of T cell dysfunction and pathogen persistence in chronic infections. Tregs have been reported to suppress virus-specific T cell responses in hepatitis B virus (HBV) infection of human patients as well as in HBV animal models. However, the phenotype and expansion of Tregs has so far only been investigated in other infections, but not in HBV. We therefore performed hydrodynamic injections of HBV plasmids into mice and analyzed the Treg response in the spleen and liver. Absolute Treg numbers significantly increased in the liver but not the spleen after HBV injection. The cells were natural Tregs that surprisingly did not show any activation or proliferation in response to the infection. However, they were able to suppress effector T cell responses, as selective depletion of Tregs significantly increased HBV-specific CD8+ T cell responses and accelerated viral antigen clearance. The data implies that natural Tregs infiltrate the liver in HBV infection without further activation or expansion but are still able to interfere with T cell mediated viral clearance.

Lentiviral vector encoding ubiquitinated hepatitis B core antigen induces potent cellular immune responses and therapeutic immunity in HBV transgenic mice

Predominant T helper cell type 1 (Th1) immune responses accompanied by boosted HBV-specific cytotoxic T lymphocyte (CTL) activity are essential for the clearance of hepatitis B virus (HBV) in chronic hepatitis B (CHB) patients. Ubiquitin (Ub) serves as a signal for the target protein to be recognized and degraded through the ubiquitin-proteasome system (UPS). Ubiquitinated hepatitis B core antigen (Ub-HBcAg) has been proved to be efficiently degraded into the peptides, which can be presented by major histocompatibility complex (MHC) class I resulting in stimulating cell-mediated responses. In the present study, lentiviral vectors encoding Ub-HBcAg (LV-Ub-HBcAg) were designed and constructed as a therapeutic vaccine for immunotherapy. HBcAg-specific cellular immune responses and anti-viral effects induced by LV-Ub-HBcAg were evaluated in HBV transgenic mice. We demonstrated that immunization with LV-Ub-HBcAg promoted the secretion of cytokines interleukin-2 (IL-2), interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α), generated remarkably high percentages of IFN-γ-secreting CD8(+) T cells and CD4(+) T cells, and enhanced HBcAg-specific CTL activity in HBV transgenic mice. More importantly, vaccination with LV-Ub-HBcAg could efficiently decreased the levels of serum hepatitis B surface antigen (HBsAg), HBV DNA and the expression of HBsAg and HBcAg in liver tissues of HBV transgenic mice. In addition, LV-Ub-HBcAg could upregulate the expression of T cell-specific T-box transcription factor (T-bet) and downregulate the expression of GATA-binding protein 3 (GATA-3) in spleen T lymphocytes. The therapeutic vaccine LV-Ub-HBcAg could break immune tolerance, and induce potent HBcAg specific cellular immune responses and therapeutic effects in HBV transgenic mice.

Nucleic acid (DNA) immunization as a platform for dengue vaccine development

Since the early 1990s, DNA immunization has been used as a platform for developing a tetravalent dengue vaccine in response to the high priority need for protecting military personnel deployed to dengue endemic regions of the world. Several approaches have been explored ranging from naked DNA immunization to the use of live virus vectors to deliver the targeted genes for expression. Pre-clinical animal studies were largely successful in generating anti-dengue cellular and humoral immune responses that were protective either completely or partially against challenge with live dengue virus. However, Phase 1 clinical evaluation of a prototype monovalent dengue 1 DNA vaccine expressing prM and E genes revealed anti-dengue T cell IFNγ responses, but poor neutralizing antibody responses. These less than optimal results are thought to be due to poor uptake and expression of the DNA vaccine plasmids. Because DNA immunization as a vaccine platform has the advantages of ease of manufacture, flexible genetic manipulation and enhanced stability, efforts continue to improve the immunogenicity of these vaccines using a variety of methods.

IL-33 Enhances Humoral Immunity Against Chronic HBV Infection Through Activating CD4(+)CXCR5(+) TFH Cells

This study aimed to investigate the potential effect of interleukin 33 (IL-33) on humoral responses to hepatitis B virus (HBV) and the possible mechanisms underlying the action of IL-33 in regulating follicular helper T (TFH) cells. The impact of IL-33 treatment on the levels of serum HBV DNA, HBsAg, HBeAg, HBsAb, and HBeAb, as well as the frequencies of CD4(+)CXCR5(+) TFH cells in wild-type HBV transgenic (HBV-Tg) mice and in a transwell coculture of HepG2.2.15 with IL-33-treated peripheral blood mononuclear cells (PBMCs) were determined. Furthermore, the gene transcription profiles in IL-33-treated TFH cells were determined by microarrays. IL-33 treatment significantly reduced the levels of serum HBV DNA, HBsAg, and HBeAg, but increased the levels of HBsAb and HBeAb in HBV-Tg mice, accompanied by increased frequency of splenic infiltrating CD4(+)CXCR5(+) TFH cells in HBV-Tg. Similarly, coculture of HepG2.2.15 cells with IL-33-treated PBMCs reduced the levels of HBV DNA, HBsAg, and HBeAg, but increased the levels of HBsAb and HBeAb. Microarray analyses indicated that IL-33 significantly modulated the transcription of many genes involved in regulating TFH activation and differentiation. Our findings suggest that IL-33 may activate TFH cells, promoting humoral responses to HBV during the pathogenic process.

Persistence of the recombinant genomes of woodchuck hepatitis virus in the mouse model

Hydrodynamic injection (HI) with a replication competent hepatitis B virus (HBV) genome may lead to transient or prolonged HBV replication in mice. However, the prolonged HBV persistence after HI depends on the specific backbone of the vector carrying HBV genome and the genetic background of the mouse strain. We asked whether a genetically closely related hepadnavirus, woodchuck hepatitis virus (WHV), may maintain the gene expression and replication in the mouse liver after HI. Interestingly, we found that HI of pBS-WHV1.3 containing a 1.3 fold overlength WHV genome in BALB/c mouse led to the long presence of WHV DNA and WHV proteins expression in the mouse liver. Thus, we asked whether WHV genome carrying foreign DNA sequences could maintain the long term gene expression and persistence. For this purpose, the coding region of HBV surface antigen (HBsAg) was inserted into the WHV genome to replace the corresponding region. Three recombinant WHV-HBV genomes were constructed with the replacement with HBsAg a-determinant, major HBsAg, and middle HBsAg. Serum HBsAg, viral DNA, hepatic WHV protein expression, and viral replication intermediates were detected in mice after HI with recombinant genomes. Similarly, the recombinant genomes could persist for a prolonged period of time up to 45 weeks in mice. WHV and recombinant WHV-HBV genomes did not trigger effective antibody and T-cell responses to viral proteins. The ability of recombinant WHV constructs to persist in mice is an interesting aspect for the future investigation and may be explored for in vivo gene transfer.

Hepatitis B virus core protein inhibits Fas-mediated apoptosis of hepatoma cells via regulation of mFas/FasL and sFas expression

Hepatitis B virus core protein (HBc) has been implicated in hepatocarcinogenesis through several mechanisms. Resistance of hepatitis B virus (HBV)-infected hepatocytes to apoptosis is considered one of the major contributors to the progression of chronic hepatitis to cirrhosis and ultimately to hepatocellular carcinoma. The Fas receptor/ligand (Fas/FasL) system plays a prominent role in hepatocyte death during HBV infection. Here we report that HBc mediates resistance of hepatoma cells to agonistic anti-Fas antibody (CH11)-induced apoptosis. When HBc was introduced into human hepatoma cells, the cells became resistant to CH11 cytotoxicity in a p53-dependent manner. HBc significantly down-regulated the expression of p53, total Fas, and membrane-bound Fas at the mRNA and protein levels and reduced FasL mRNA expression. In contrast, HBc up-regulated the expression of soluble forms of Fas by increasing Fas alternative mRNA splicing. Mechanistically, HBc-mediated Fas alternative mRNA splicing was associated with up-regulation of polypyrimidine tract-binding protein 1 and down-regulation of Fas-activated serine/threonine kinase. These results indicated that HBc may prevent hepatocytes from Fas-induced apoptosis by the dual effects of reducing the expression of the proapoptotic form of Fas and enhancing the expression of the antiapoptotic form of the receptor, which may contribute to the survival and persistence of infected hepatocytes during chronic infection.

Woodchuck hepatitis virus core antigen-based DNA and protein vaccines induce qualitatively different immune responses that affect T cell recall responses and antiviral effects

T helper type 1 (Th1) immunity was considered to play a dominant role in viral clearance of hepadnaviral infection. However, pre-primed Th2 type responses were able to efficiently control hepadnaviral infection in animal models. We investigated how pre-primed Th1/2 responses control hepadnaviral replication using the newly established mouse models. DNA (pWHcIm, pCTLA-4-C) and protein vaccines based on the nucleocapsid protein (WHcAg) of woodchuck hepatitis virus (WHV) primed specific immune responses with distinct features. The pre-primed responses determined the characteristics of recall responses if challenged with a WHcAg-expressing adenoviral vector. Vaccination with pWHcIm and pCTLA4-C facilitated viral control in the hydrodynamic injection model and reduced WHV loads by about 3 and 2 logs in WHV-transgenic mice, respectively, despite of different kinetics of specific CD8+ T cell responses. Thus, pre-primed Th2-biased responses facilitate the development of CD8+ T cell responses in mice compared with naïve controls and thereby confer better viral control.

Fusion of CTLA-4 with HPV16 E7 and E6 enhanced the potency of therapeutic HPV DNA vaccine

Preventive anti-HPV vaccines are effective against HPV infection but not against existing HPV-associated diseases, including cervical cancer and other malignant diseases. Therefore, the development of therapeutic vaccines is urgently needed. To improve anti-tumor effects of therapeutic vaccine, we fused cytotoxic T-lymphocyte antigen 4 (CTLA-4) with HPV16 E7 and E6 as a fusion therapeutic DNA vaccine (pCTLA4-E7E6). pCTLA4-E7E6 induced significantly higher anti-E7E6 specific antibodies and relatively stronger specific CTL responses than the nonfusion DNA vaccine pE7E6 in C57BL/6 mice bearing with TC-1 tumors. pCTLA4-E7E6 showed relatively stronger anti-tumor effects than pE7E6 in therapeutic immunization. These results suggest that fusing CTLA-4 with E7E6 is a useful strategy to develop therapeutic HPV DNA vaccines. In addition, fusing the C-terminal of E7 with the N-terminal of E6 impaired the functions of both E7 and E6.

Coexistence of hepatitis B virus quasispecies enhances viral replication and the ability to induce host antibody and cellular immune responses

Hepatitis B virus (HBV) quasispecies contain a large number of variants that serve as a reservoir for viral selection under antiviral treatment and the immune response, leading to the acute exacerbation and subsequent development of liver failure. However, there is no clear experimental evidence for a significant role of HBV quasispecies in viral pathogenesis. In the present study, HBV sequences were amplified from a patient with severe liver disease and used for construction of HBV replication-competent plasmids. Western blotting, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence staining were performed to analyze the expression, secretion, and subcellular localization of viral proteins in vitro. Viral replication intermediates were detected by Southern blotting. HBV gene expression and replication and the induction of specific immune responses in an HBV hydrodynamic injection (HI) mouse model were investigated. The results demonstrated that two naturally occurring HBV variants, SH and SH-DPS, were identified. The variant SH-DPS expressed only a nonexportable hepatitis B virus surface antigen (HBsAg) with abnormal intracellular accumulation. The coexistence of the HBV variants at a ratio of 1 to 4 (SH to SH-DPS) increased HBV replication. Significantly stronger intrahepatic cytotoxic T lymphocyte (CTL) responses and antibody responses specific to HBsAg were induced in mice by the HBV variants when coapplied by HI. These findings uncovered an unexpected aspect of HBV quasispecies: the coexistence of different variants can significantly modulate specific host immune responses, representing a novel mechanism for the immunopathogenesis of HBV infection.

IMPORTANCE

Hepatitis B virus (HBV) is an important human pathogen. HBV quasispecies with genetically heterogenous variants are thought to play a role in the progression of HBV-associated liver diseases. So far, direct evidence is available in only a few cases to confirm the proposed role of HBV variants in the pathogenesis. We report here that the coexistence of two naturally occurring HBV variants at a ratio of 1 to 4 increased HBV replication and induced significantly stronger intrahepatic cytotoxic T lymphocyte responses and antibody responses specific to HBV surface antigen (HBsAg) in mice. Our discovery uncovered an unexpected aspect of HBV quasispecies: the coexistence of different variants can significantly modulate specific host immune responses and may enhance immune-mediated liver damage under some circumstances, representing a novel mechanism for the immunopathogenesis of HBV infection.

Immunosuppressive drugs modulate the replication of hepatitis B virus (HBV) in a hydrodynamic injection mouse model

Hepatitis B virus (HBV) reactivation and recurrence are common in patients under immunosuppression and can be controlled by hepatitis B immunoglobulin, antivirals, and hepatitis B vaccine. However, the detailed analysis of HBV infection under immunosuppression is essential for the prophylaxis and therapy for HBV reactivation and recurrence. In this study, HBV replication and T cell responses were analyzed in a HBV-transfected mouse model under immunosuppressive therapy. During the treatment, HBV replication was at a high level in mice treated with dexamethasone, cyclosporine, and cyclophosphamide, whereas was terminated in mice treated with mycophenolate mofetil. After the withdrawal, HBV replication was at low or high levels in the dexamethasone-treated mice or in both cyclosporine- and cyclophosphamide-treated mice. The early withdrawal of cyclosporine allowed the recovery of suppressed T cell responses and led to subsequent HBV clearance, while the adoptive immune transfer to the mice with HBV persistence led to HBV suppression. Taken together, long-term HBV persistence under immunosuppression depends on the immunosuppressive drugs used and on the treatment duration and is mediated by the suppressed intrahepatic CD8 T cell response. These data may be helpful for individualized immunosuppressive therapy in patients with high risk of HBV reactivation and recurrence, and the mouse system is suitable for studying HBV reactivation and recurrence under immunosuppression.

DNA vaccine cocktail expressing genotype A and C HBV surface and consensus core antigens generates robust cytotoxic and antibody responses in mice and Rhesus macaques

There are well over a quarter of a billion chronic hepatitis B virus (HBV) carriers across the globe. Most carriers are at high risk for development of liver cirrhosis and subsequent progression to hepatocellular carcinoma. It is therefore imperative to develop new approaches for immunotherapy against this infection. Antibodies and cytotoxic T cells to different HBV antigens are believed to be important for reducing viral load and clearing HBV-infected cells from the liver. Some of the major challenges facing current vaccine candidates have been their inability to induce both humoral and cellular immunity to multiple antigenic targets and the induction of potent immune responses against the major genotypes of HBV. In this study, highly optimized synthetic DNA plasmids against the HBV consensus core (HBc) and surface (HBs) antigens genotypes A and C were developed and evaluated for their immune potential. These plasmids, which encode the most prevalent genotypes of the virus, were observed to individually induce binding antibodies to HBs antigens and drove robust cell-mediated immunity in animal models. Similar responses to both HBc and HBs antigens were observed when mice and non-human primates were inoculated with the HBc-HBs cocktails. In addition to the cytotoxic T lymphocyte activities exhibited by the immunized mice, the vaccine-induced responses were broadly distributed across multiple antigenic epitopes. These elements are believed to be important to develop an effective therapeutic vaccine. These data support further evaluation of multivalent synthetic plasmids as therapeutic HBV vaccines.

A modified murine model based on hydrodynamic injection for the analysis of chronic human hepatitis B virus infection

Hepatitis B virus (HBV) is a persistent pathogen that causes acute and chronic necroinflammatory liver disease and is attributable to ~1 million deaths per year. In the present study, a conventional murine model was introduced based on the hydrodynamic injection of engineered replication‑competent HBV DNA into the tail veins of C57BL/6 mice. In a previous study, nine in‑frame ATG (start) codons in the S open reading frame (S1‑S9) were analyzed. The highly conserved ATG S5 was mutated to ACG by T378C, which led to the substitution sM75T and inhibition of the production and secretion of the hepatitis B surface antigen (HBsAg), and subsequent inhibition of HBV replication. In the present study, T378C was introduced into the pAAV‑HBV1.3 plasmid and was confirmed to affect HBsAg production and secretion, and HBV replication in vivo, which was in agreement with the previous in vitro results. Furthermore, the murine model was improved by co‑injection of the replication‑competent HBV plasmid DNA with Lipofectamine 2000 (LP). In this model, LP not only significantly enhanced HBV replication in mice, but also upregulated the expression of HBsAg and the hepatitis B core antigen. The current modified murine model was superior to the conventional murine HBV model based on HBV challenge by hydrodynamic injection.

Influence of the oncolytic parvovirus H-1, CTLA-4 antibody tremelimumab and cytostatic drugs on the human immune system in a human in vitro model of colorectal cancer cells

Introduction

Tumor-directed and immune-system-stimulating therapies are of special interest in cancer treatment. Here, we demonstrate the potential of parvovirus H-1 (H-1PV) to efficiently kill colorectal cancer cells and induce immunogenicity of colorectal tumors by inducing maturation of dendritic cells (DCs) alone and also in combination with cytostatic drugs in vitro. Using our cell culture model, we have additionally investigated the effects of anti-CTLA-4 (cytotoxic T-lymphocyte-associated antigen 4) receptor antibody tremelimumab on this process.

Materials and methods

Colon carcinoma cell lines were treated with different concentrations of cytostatic drugs or tremelimumab or were infected with H-1PV in different multiplicities of infection (MOIs), and viability was determined using MTT assays. Expression of CTLA-4 in colon carcinoma cell lines was measured by FACScan™. For the coculture model, we isolated monocytes using adherence, and differentiation into immature DCs (iDCs) was stimulated using interleukin-4 and granulocyte-macrophage colony-stimulating factor. Maturation of iDCs into mature DCs (mDCs) was induced by a cytokine cocktail. SW480 colon carcinoma cells were infected with H-1PV or treated with cytostatic drugs. Drug treated and H-1PV-infected SW480 colon carcinoma cells were cocultured with iDCs and expression of maturation markers was measured using FACScan™. Cytokine measurements were performed using enzyme-linked immunosorbent assay.

Results

Colon carcinoma cells SW480 were potently infected and killed by H-1PV. CTLA-4 expression in SW480 cells increased after infection with H-1PV and also after treatment with cytostatic drugs. Tremelimumab had no influence on viability of the colon carcinoma cell line. There was no maturation of iDCs after coculture with SW480; instead, H-1PV-infected or drug pretreated SW480 induced maturation. Cytokine production was higher for H-1PV-infected cells but was not significantly enhanced by tremelimumab treatment alone or in combination. Addition of tremelimumab did not interfere with the maturation process as measured by markers of maturation as well as by determination of cytokine levels.

Conclusion

By enhancing both cell death and immunogenicity of tumors, H-1PV is of special interest for tumor-directed therapy. These features make it a promising candidate for clinical application in human colorectal cancer. As tremelimumab does not significantly interfere with this process, an interesting therapeutic combination of active enhancement of tumor immunogenicity and independent masking of the CTLA-4 silencing process on tumor cells is highlighted.

HBsAg, HBcAg, and combined HBsAg/HBcAg-based therapeutic vaccines in treating chronic hepatitis B virus infection

BACKGROUND

As the host immunity is diminished in patients with chronic hepatitis B (CHB), different approaches have been used to up-regulate their immune responses to produce therapeutic effects. But, cytokines, growth factors and polyclonal immune modulators could not exhibit sufficient therapeutic effects in these patients. Immune therapy with HBV-related antigens (vaccine therapy) has been used in CHB patients. But there is a paucity of information about the design of HBV antigen-based immune therapy in these patients.

DATA SOURCE

Preclinical and clinical studies on immune therapy with HBsAg-based vaccine, HBcAg and combination of HBsAg/HBcAg-based vaccines have been discussed.

RESULTS

HBsAg-based prophylactic vaccine was used as an immune therapeutic agent in CHB patients; however, monotherapy with HBsAg-based immune therapy could not lead to sustained control of HBV replication and/or liver damages. HBsAg-based vaccine was used as a combination therapy with cytokines, growth factors, and antiviral drugs. HBsAg-based vaccine was also used for cell-based therapy. However, satisfactory therapeutic effects of HBsAg-based vaccine could not be documented in CHB patients. In the mean time, evidences have supported that HBcAg-specific immunity is endowed with antiviral and liver protecting capacities in CHB patients. Recent data concentrate on the clinical use of combined HBsAg- and HBcAg-based vaccines in CHB patients.

CONCLUSION

Antigen-based immune therapy with HBV-related antigens may be an alternative method for the treatment of CHB patients but proper designs of antigens, types of adjuvants, dose of vaccinations, and routes of administration need further analyses for the development of an effective regimen of immune therapy against HBV.

Inhibition of hepatitis B virus (HBV) gene expression and replication by HBx gene silencing in a hydrodynamic injection mouse model with a new clone of HBV genotype B

Background

It has been suggested that different hepatitis B virus (HBV) genotypes may have distinct virological characteristics that correlate with clinical outcomes during antiviral therapy and the natural course of infection. Hydrodynamic injection (HI) of HBV in the mouse model is a useful tool for study of HBV replication in vivo. However, only HBV genotype A has been used for studies with HI.

Methods

We constructed 3 replication-competent clones containing 1.1, 1.2 and 1.3 fold overlength of a HBV genotype B genome and tested them both in vitro and in vivo. Moreover, A HBV genotype B clone based on the pAAV-MCS vector was constructed with the 1.3 fold HBV genome, resulting in the plasmid pAAV-HBV1.3_B and tested by HI in C57BL/6 mice. Application of siRNA against HBx gene was tested in HBV genotype B HI mouse model.

Results

The 1.3 fold HBV clone showed higher replication and gene expression than the 1.1 and 1.2 fold HBV clones. Compared with pAAV-HBV1.2 (genotype A), the mice HI with pAAV-HBV1.3_B showed higher HBsAg and HBeAg expression as well as HBV DNA replication level but a higher clearance rate. Application of two plasmids pSB-HBxi285 and pSR-HBxi285 expressing a small/short interfering RNA (siRNA) to the HBx gene in HBV genotype B HI mouse model, leading to an inhibition of HBV gene expression and replication. However, HBV gene expression may resume in some mice despite an initial delay, suggesting that transient suppression of HBV replication by siRNA may be insufficient to prevent viral spread, particularly if the gene silencing is not highly effective.

Conclusions

Taken together, the HI mouse model with a HBV genotype B genome was successfully established and showed different characteristics in vivo compared with the genotype A genome. The effectiveness of gene silencing against HBx gene determines whether HBV replication may be sustainably inhibited by siRNA in vivo.

Potentiating functional antigen-specific CD8⁺ T cell immunity by a novel PD1 isoform-based fusion DNA vaccine

Understanding and identifying new ways of mounting an effective CD8⁺ T cell immune response is important for eliminating infectious pathogens. Although upregulated programmed death-1 (PD1) in chronic infections (such as HIV-1 and tuberculosis) impedes T cell responses, blocking this PD1/PD-L pathway could functionally rescue the "exhausted" T cells. However, there exists a number of PD1 spliced variants with unknown biological function. Here, we identified a new isoform of human PD1 (Δ42PD1) that contains a 42-nucleotide in-frame deletion located at exon 2 domain found expressed in peripheral blood mononuclear cells (PBMCs). Δ42PD1 appears to function distinctly from PD1, as it does not engage PD-L1/PD-L2 but its recombinant form could induce proinflammatory cytokines. We utilized Δ42PD1 as an intramolecular adjuvant to develop a fusion DNA vaccine with HIV-1 Gag p24 antigen to immunize mice, which elicited a significantly enhanced level of anti-p24 IgG1/IgG2a antibody titers, and important p24-specific and tetramer⁺CD8⁺ T cells responses that lasted for ≥7.5 months. Furthermore, p24-specific CD8⁺ T cells remain functionally improved in proliferative and cytolytic capacities. Importantly, the enhanced antigen-specific immunity protected mice against pathogenic viral challenge and tumor growth. Thus, this newly identified PD1 variant (Δ42PD1) amplifies the generation of antigen-specific CD8⁺ T cell immunity when used in a DNA vaccine.

The amino acid substitutions rtP177G and rtF249A in the reverse transcriptase domain of hepatitis B virus polymerase reduce the susceptibility to tenofovir

Long term antiviral therapy with nucleoside/nucleotide analogs have been routinely used to treat chronic hepatitis B virus (HBV) infection but may lead to the emergence of drug-resistant viral mutants. However, the HBV resistance mutations for tenofovir (TDF) remain controversial. It is speculated that the genetic barrier for TDF resistance may be high for HBV. We asked whether selected amino acid substitutions in HBV polymerase may reduce susceptibility to TDF. A series of amino acids in HBV polymerase were selected based on bioinformatics analysis for mutagenesis. The replication competence and susceptibility to TDF of the mutated HBV clones were determined both in vitro and in vivo. nineteen mutations in HBV polymerase were included and impaired the replication competence of HBV genome in different degrees. The mutations at rtL77F (sS69C), rtF88L (sF80Y), and rtP177G (sR169G) also significantly affected HBsAg expression. The HBV mutants with rtP177G and rtF249A were found to have reduced susceptibility to TDF in vitro with a resistance index of 2.53 and 12.16, respectively. The testing in in vivo model based on the hydrodynamic injection revealed the antiviral effect of TDF against wild type and mutated HBV genomes and confirmed the reduced the susceptibility of mutant HBV to TDF.

Synthetic DNA immunogen encoding hepatitis B core antigen drives immune response in liver

The prevalence of hepatitis B virus (HBV) infection in Asia and sub-Sahara Africa is alarming. With quarter of a billion people chronically infected worldwide and at risk of developing liver cancer, the need for a prophylactic or therapeutic vaccination approach that can effectively induce protective responses against the different genotypes of HBV is more important than ever. Such a strategy will require both the induction of a strong antigen-specific immune response and the subsequent deployment of immune response towards the liver. Here, we assessed the ability of a synthetic DNA vaccine encoding a recombinant consensus plasmid from genotype A through E of the HBV core antigen (HBcAg), to drive immunity in the liver. Intramuscular vaccination induced both strong antigen-specific T cell and high titer antibody responses systematically and in the liver. Furthermore, immunized mice showed strong cytotoxic responses that eliminate adoptively transferred HBV-coated target cells. Importantly, vaccine-induced immune responses provided protection from HBcAg plasmid-based liver transfection in a hydrodynamic liver transfection model. These data provide important insight into the generation of peripheral immune responses that are recruited to the liver-an approach that can be beneficial in the search for vaccines or immune-therapies to liver disease.

Future prevention and treatment of chronic hepatitis B infection

Vaccination for hepatitis B virus (HBV) infection and treatment for chronic hepatitis B, while effective for primary prevention and control of the disease, still have their limitations. Global coverage of HBV immunization needs improvement. Several patient populations are noted to have suboptimal seroprotective rates after HBV vaccination. There are currently several potential new vaccines undergoing animal and human studies, most notably vaccines containing immunostimulatory DNA sequences. Long-term nucleoside analogue therapy is necessary in achieving permanent virologic suppression. Potential new treatments explore new mechanisms of action, including the inhibition of hepatitis B surface antigen release, targeting antifibrotic mechanism, and immunomodulation through novel interferons and therapeutic vaccines. The clinical application of potential new vaccines and therapies would enhance the prevention of HBV infection and treatment of chronic hepatitis B.

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.

Amino acid substitutions at positions 122 and 145 of hepatitis B virus surface antigen (HBsAg) determine the antigenicity and immunogenicity of HBsAg and influence in vivo HBsAg clearance

A variety of amino acid substitutions, such as K122I and G145R, have been identified around or within the a determinant of hepatitis B surface antigen (HBsAg), impair HBsAg secretion and antibody binding, and may be responsible for immune escape in patients. In this study, we examined how different substitutions at amino acid positions 122 and 145 of HBsAg influence HBsAg expression, secretion, and recognition by anti-HBs antibodies. The results showed that the hydrophobicity, the presence of the phenyl group, and the charges in the side chain of the amino acid residues at position 145 reduced HBsAg secretion and impaired reactivity with anti-HBs antibodies. Only the substitution K122I at position 122 affected HBsAg secretion and recognition by anti-HBs antibodies. Genetic immunization in mice demonstrated that the priming of anti-HBs antibody response was strongly impaired by the substitutions K122I, G145R, and others, like G145I, G145W, and G145E. Mice preimmunized with wild-type HBsAg (wtHBsAg) or variant HBsAg (vtHBsAg) were challenged by hydrodynamic injection (HI) with a replication-competent hepatitis B virus (HBV) clone. HBsAg persisted in peripheral blood for at least 3 days after HI in mice preimmunized with vtHBsAg but was undetectable in mice preimmunized with wtHBsAg, indicating that vtHBsAgs fail to induce proper immune responses for efficient HBsAg clearance. In conclusion, the biochemical properties of amino acid residues at positions 122 and 145 of HBsAg have a major effect on antigenicity and immunogenicity. In addition, the presence of proper anti-HBs antibodies is indispensable for the neutralization and clearance of HBsAg during HBV infection.