Establishment of a monoclonal antibody against human NTCP that blocks HBV infection

Hepatitis B virus (HBV) infects 240 million people worldwide. Current therapy profoundly suppresses HBV replication but requires long-term maintenance therapy. Therefore there is still a medical need for an efficient HBV cure. HBV enters host cells by binding via the preS1-domain of the viral L protein to the Na + /Taurocholate Cotransporting Polypeptide (NTCP). Thus, NTCP should be a key target for the development of anti-HBV therapeutics. Indeed, Myrcludex B, a synthetic form of the myristoylated preS1 peptide, effectively reduces HBV/HDV infection and has been approved as Hepcludex® in Europe for the treatment of patients with chronic hepatitis D virus (HDV) infection. We established a monoclonal antibody (mAb) N6HB426-20 that recognizes the extracellular domain of human NTCP and blocks HBV entry in vitro into human liver cells but has much less of an inhibitory effect on bile acid uptake. In vivo , administration of the N6HB426-20 mAb prevented HBV viremia for an extended period of time after HBV inoculation in a mouse model system without strongly inhibiting bile acid absorption. Among the extracellular loops (ECLs) of NTCP, regions of amino acids (aa) 84-87 in ECL1 and aa 157-165 near ECL2 of transmembrane domain 5 are critically important for HBV/HDV infection. Epitope-mapping and the 3D model of the NTCP structure suggested that the N6HB426-20 mAb may recognize aa 276/277 at the tip of ECL4 and interfere with an binding of HBV to the aa 84-87 region. In summary, we identified an in vivo neutralizing NTCP-targeting antibody capable of preventing HBV infection. Further improvements in efficacy of this drug will pave the way for its clinical applications. IMPORTANCE A number of entry inhibitors are being developed to enhance the treatment of HBV patients with oral nucleos(t)ide analogues (NA). To amplify the effectiveness of NA therapy, several efforts have been made to develop therapeutic mAbs with neutralizing activity against HBs antigens. However, the neutralizing effect of these mAbs may be muted by a large excess of HBsAg-positive noninfectious particles in the blood of infected patients. The advantage of NTCP-targeted HBV entry inhibitors is that they remain effective regardless of viral genotype, viral mutations and the presence of subviral particles. Although N6HB426-20 requires a higher dose than Myrcludex to obtain equivalent suppression of HBV in a model mouse system, it maintained the inhibitory effect for a long time post administration in proportion to the half-life of an IgG mAb. We believe that further improvements will make this antibody a promising treatment option for patients with chronic hepatitis B.

The global hepatitis delta virus (HDV) epidemic: what gaps to address in order to mount a public health response?

Background Co-infection between hepatitis B virus (HBV) and hepatitis delta virus (HDV) causes the severest chronic hepatitis and is associated with a high risk of cirrhosis and hepatocellular carcinoma (HCC). The Global Health Sector Strategy on Viral Hepatitis called for the elimination of hepatitis (− 65% mortality and − 90% incidence) by 2030. Our aims were to summarize key points of knowledge and to identify the gaps that need to be addressed to mount a public health response to HDV. Methods We performed a current literature review in terms of epidemiology by WHO regions, genotypes distribution and their pathogenicity, factors associated with HDV infection, mortality due to HDV infection, testing strategies and treatment. Results Prevalence of infection and genotypes are heterogeneous distributed, with highest prevalence in foci around the Mediterranean, in the Middle East, and in Central, Northern Asia and Eastern Asia. Persons who inject drugs (PWID) and migrants from highly endemic areas are highly affected. While antibody detection tests are available, HDV RNA tests of current infection are not standardized nor widely available. The few therapeutic options, including lofartinib, are not widely available; however several new and promising agents have entered clinical trials. Conclusion HDV infection is an poorly known cause of chronic liver disease. To mount a public health response, we need a better description of the HDV epidemic, standardized testing strategies and better treatment options.

The kinesin KIF4 mediates HBV/HDV entry through regulation of surface NTCP localization and can be targeted by RXR agonists in vitro.

Intracellular transport via microtubule-based dynein and kinesin family motors plays a key role in viral reproduction and transmission. We show here that Kinesin Family Member 4 (KIF4) plays an important role in HBV/HDV infection. We intended to explore host factors impacting the HBV life cycle that can be therapeutically addressed using siRNA library transfection and HBV/NLuc (HBV/NL) reporter virus infection in HepG2-hNTCP C4 cells. KIF4 silencing resulted in a 3-fold reduction in luciferase activity following HBV/NL infection and suppressed both wild-type HBV and HDV infection. Transient KIF4 depletion reduced surface and raised intracellular NTCP (HBV/HDV entry receptor) levels, according to both cellular fractionation and immunofluorescence analysis (IF). Overexpression of wild-type KIF4 but not ATPase-null KIF4 regains the surface localization of NTCP in these cells. Furthermore, IF revealed KIF4 and NTCP colocalization across microtubule filaments, and a co-immunoprecipitation study revealed that KIF4 physically binds to NTCP. KIF4 expression is regulated by FOXM1. Interestingly, we discovered that RXR agonists (Bexarotene, and Alitretinoin) down-regulated KIF4 expression via FOXM1 mediated suppression, resulting in a substantial decrease in HBV-Pre-S1 protein attachment to HepG2-hNTCP cell surface and subsequent HBV infection in HepG2-hNTCP and primary human hepatocytes (PXB) (Bexarotene, IC 50 1.89 ± 0.98 μM). Overall, our findings show that human KIF4 is a critical regulator of NTCP surface transport and localization, which is required for NTCP to function as a receptor for HBV/HDV entry. Furthermore, small molecules that suppress or alleviate KIF4 expression would be potential antiviral candidates that target HBV and HDV entry phase.

HBV and HDV: New Treatments on the Horizon

Despite the accumulating knowledge, chronic hepatitis B (CHB) and HDV infection represent a global health problem, and there are still several critical issues, which frequently remain uncovered. In this paper, we provided an overview of the current therapeutic options and summarized the investigational therapies in the pipeline. Furthermore, we discussed some critical issues such as a “functional cure” approach, the futility of long-term NA therapy and the relevance of understanding drug actions and safety of antivirals, especially in special populations.

Digital Droplet PCR (ddPCR) for Detection and Quantitation of Hepatitis Delt Virus

Background & Aims The prevalence of hepatitis delt virus (HDV) far exceeds our expected level, there remains a lack of reliable quantitative assays for HDV RNA detection. We sought to develop a new method based on digital droplet PCR (ddPCR) for HDV RNA quantitative detection. Methods With plasmid (pMD19T) containing HDV full-genome, we determined the method for ddPCR-based HDV RNA quantification. To compare various assays for HDV detection, 30 cases diagnosed hepatitis D and 14 controls were examined by ELISA, RT-PCR and ddPCR. 728 HBV-related patients including 182 chronic hepatitis B (CHB), 182 liver cirrhosis (LC), 182 hepatocellular carcinoma (HCC) and 182 liver failure (LF) were screened for HDV infection. Results The limit of detection of ddPCR for HDV is significantly low, which lower limit of detection (LLoD) and lower limit of quantitation (LLoQ) to be 5.51 copies/reaction (95% CI: 1.15–6.4*105) and 0.18 copies/reaction (95% CI: 0.0012151- 0.76436), respectively. Among the 44 samples, ELISA detected 30 cases positive for anti-HDV, ddPCR reported 24 samples and RT-PCR reported 10 samples positive for HDV RNA. Moreover, the positive rates of anti-HDV IgG were 1.1%, 3.3%, 2.7% and 7.1% in patients with CHB, LC, HCC, and LF; the detection rates of RT-PCR in HDV RNA were 0%, 16.67%, 15.4% and 20%, however, the detection rates of ddPCR were 0%, 33.33%, 30.77% and 60%. Conclusion We establish a high sensitivity and high specificity quantitative HDV RNA detection method based on ddPCR compared to RT-PCR. HBV-related end-stage liver disease, especially liver failure, are associated with a remarkably high rate of HDV infection.

Endemicity And Genetic Diversity of Hepatitis Delta Virus Among Pygmies In Cameroon, Central Africa.

A single study conducted two decades ago on hepatitis delta virus (HDV) infections among Baka Pygmies in Cameroon reported a very high antibody prevalence of 46%, but HDV genetic diversity has not yet been studied in this remote population. In the present study, we investigated the HDV seroprevalence and the genotype diversity in the three main Cameroonian Pygmy populations with chronic HBV infection. An unusually high (69.2%) level of HDV infection was found among HBsAg-positive Pygmies in Cameroon. Phylogenetic analyses showed the co-circulation of highly diverse HDV genotypes HDV-1 and HDV-7 in this population. These results highlighted the endemicity of HDV infection in Central Africa and suggest an african origin of HDV.

Effectiveness and safety of orally administered silymarin (milk thistle) for pegylated interferon unresponsive chronic delta hepatitis patients

Objective: Silymarin is a natural extract from milk thistle (Silybum marianum), a natural herb that contains flavonoids. Silymarin also has anti-inflammatory properties and lipid peroxidation effects on human hepatocytes. It has also been used for the treatment of acute alpha-amanitin poisoning and chronic hepatitis C infection. Chronic Hepatitis D virus (HDV) infection is a severe health problem leading to fibrosis and hepatocellular carcinoma. Patients with chronic HDV infection can be treated with Peg-IFN with lower treatment success. Most patients with chronic HDV are unable or unwilling to use interferon (IFN)-based treatment due to liver cirrhosis. Our objective was to establish the long-term clinical outcomes with silymarin for interferon-experienced chronic HDV patients. Materials and Methods: We studied ten patients from one centre with interferon who experienced chronic HDV, of which 8 had cirrhosis, and 2 had chronic hepatitis who received HDV treatment with silymarin 600 mg/day after a median period of 12 months. Information collected included demographic, clinical, virologic, and outcomes data. MELD and Child-Pugh (CP) scores were also obtained. Friedman test was used to evaluate the laboratory parameters during the study period. Results: 10 chronic HDV patients (median age 54 yrs, six female, all of them previous null responders to Peg-IFN with mildly decompensated cirrhosis [CP 7 (range 6-11), MELD 11 (range 6-20] were followed for 12 months from the start of silymarin 600 mg/day. There was no decompensation of both MELD and CP scores among patients at the end of therapy. In addition, no patients stopped silymarin treatment early due to side effects. At the end of treatment, there was no significant change in prothrombin time (p= 0.949), AST (p=0.662) and AFP (p=0.983) levels and platelets counts (p=0.988) compared to the pre-treatment period (all p>0.005). Finally, HDV-RNA suppression was seen in all patients at the end of treatment (p=0.009). Conclusions: In the light of the presented data, silymarin seems to be effective in treating chronic HDV infection. Further research is needed for validation. The study is ongoing with a collection of data on sustained viral response.

Seroprevalence and risk factors of hepatitis B, C and D virus infection amongst patients with features of hepatitis in a referral hospital in Botswana: A cross-sectional study

Background: Viral hepatitis is a major global health problem. There is a paucity of data from Botswana on the seroprevalence of markers of hepatitis. The objective of the study was to determine the seroprevalence and risk factors of hepatitis B virus (HBV), hepatitis D virus (HDV) and hepatitis C virus (HCV) infections in patients with clinical features of hepatitis and/or altered liver function tests.Method: This cross-sectional study was done at Princess Marina Hospital (PMH) in Gaborone, Botswana, from February 2015 to July 2016. It involved 328 adult patients with any of the following: jaundice, history of liver disease and/or increased serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and serum bilirubin of 2 times the upper limit of normal (ULN).Results: Active or chronic active hepatitis (hepatitis B surface antigen [HBsAg] positive) was identified in 46.7% of patients. Antibodies to HDV infection were detected in 4.6% of the HBsAg-positive patients and antibodies to HCV infection in 4.3% of the study patients. Immunity against HBV infection was noted in 34.5% of patients. Human immunodeficiency virus (HIV) co-infection was self-reported by 42.7% of HBsAg-positive patients with known HIV status.Conclusion: High prevalence rate of HBV, HCV, HDV infection and HIV co-infection was observed in patients with liver disease attending PMH.