Prolonged suppression of HBV in mice by a novel antibody that targets a unique epitope on hepatitis B surface antigen.

OBJECTIVE: This study aimed to investigate the therapeutic potential of monoclonal antibody (mAb) against HBV as a novel treatment approach to chronic hepatitis B (CHB) in mouse models. METHODS: Therapeutic effects of mAbs against various epitopes on viral surface protein were evaluated in mice mimicking persistent HBV infection. The immunological mechanisms of mAb-mediated viral clearance were systematically investigated. RESULTS: Among 11 tested mAbs, a novel mAb E6F6 exhibited the most striking therapeutic effects in several HBV-persistent mice. Single-dose administration of E6F6 could profoundly suppress the levels of hepatitis B surface antigen (HBsAg) and HBV DNA for several weeks in HBV-transgenic mice. E6F6 regimen efficiently prevented initial HBV infection, and reduced viral dissemination from infected hepatocytes in human-liver-chimeric mice. E6F6-based immunotherapy facilitated the restoration of anti-HBV T-cell response in hydrodynamic injection (HDI)-based HBV carrier mice. Immunological analyses suggested that the Fcγ receptor-dependent phagocytosis plays a predominant role in E6F6-mediated viral suppression. Molecular analyses suggested that E6F6 recognises an evolutionarily conserved epitope (GPCK(R)TCT) and only forms a smaller antibody-viral particle immune complex with limited interparticle crosslinking when it binds to viral particles. This unique binding characteristic of E6F6 to HBV was possibly associated with its effective in vivo opsonophagocytosis for viral clearance. CONCLUSIONS: These results provided new insight into understanding the therapeutic role and mechanism of antibody against persistent viral infection. The E6F6-like mAbs may provide a novel immunotherapeutic agent against human chronic HBV infection.

The modulation of hepatitis C virus 1a replication by PKR is dependent on NF-kB mediated interferon beta response in Huh7.5.1 cells.

Protein kinase R (PKR), a sensor of double-stranded RNA, plays an important role in the host response to viral infection. Hepatitis C genotype 2a virus (HCV2a) has been shown to induce PKR activation to suppress the translation of antiviral interferon stimulated genes (ISGs), suggesting that PKR inhibitor can be beneficial for treating chronically HCV-infected patients in conjunction with interferon alpha and ribavirin. However, in this study, we found that PKR inhibition using siRNA PKR, shRNA PKR or PKR inhibitor enhanced HCV 1a replication and rendered Huh7.5.1 cells more susceptible to HCV1a infection. Additionally, PKR silencing suppressed NF-kB activation and NF-kB mediated STAT1 phosphorylation in Huh7.5.1 cells and HCV1a persistently infected Huh7.5.1 cells (2HDD4). These effects were accompanied by a reduction of interferon beta response and thereby enhanced HCV1a replication in Huh7.5.1 cells. We conclude that host cells can employ PKR activation to restrict HCV1a replication through regulation of NF-kB expression.

Mycoplasma fermentans infection promotes immortalization of human peripheral blood mononuclear cells in culture.

Chronic infection or colonization by mycoplasma(s) could gradually and significantly alter many biologic properties of mammalian host cells in culture, including induction of malignant transformation. We examined effects of Mycoplasma fermentans infection on the continuing survival and immortality of human peripheral blood mononuclear cells (PBMCs) from healthy blood donors. Without specific supplemental growth factors, human PBMCs normally die rapidly, with few cells other than macrophages/monocytes surviving after 2 weeks in cultures. Only occasional Epstein-Barr virus (EBV)-positive B lymphocytes would continue to proliferate and undergo spontaneous immortalization. Our present study revealed that infection of human PBMCs in culture with the incognitus and PG18 strains of M fermentans, but surprisingly not with some other strains tested in parallel, markedly enhanced the rate of EBV-positive B lymphocytes to undergo immortalization (74% vs 17%). Compared with spontaneously immortalized PBMCs, the PBMCs immortalized in cultures infected with the mycoplasmas often had prominent karyotype changes with chromosomal loss, gain, or translocations. Furthermore, many of these immortalized B lymphocytes were found to be monoclonal in nature. The in vitro findings would be of relevance to lymphoproliferative disorders that occurred in patients with immune suppression. The mycoplasma-mediated promotional effect in cell immortalization and its potential clinical implications warrant further study.

Mycoplasma hominis lipid-associated membrane protein antigens for effective detection of M. hominis-specific antibodies in humans.

Lipid-associated membrane proteins (LAMPs) from 14 Mycoplasma hominis isolates or strains share similar protein and antigenicity profiles. Of 31 human immunodeficiency virus-infected patients from whose samples M. hominis was cultured, 28 tested strongly positive for serum antibodies to M. hominis LAMPs. The remaining 3 serum samples showed low antibody titer to LAMPs from all of the 14 M. hominis isolates or strains, which was likely the result of the compromised immune systems of the patients. Thus, M. hominis LAMPs as a whole are homogenous in antigenicity within the species, despite having many different serotypes. Serological study involving 564 healthy blood donors and 211 patients attending sexually transmitted disease clinics by LAMPs showed that general populations were widely exposed to M. hominis. Women were infected with M. hominis at a younger age than were men. The prevalence of infection increased markedly among sexually active persons.