The function of the hepatitis E virus (HEV) open reading frame 3 (ORF3) protein remains unclear. To elucidate the role of the ORF3 protein in the virus life cycle, an infectious cDNA clone (pJE03-1760F/wt) that can replicate efficiently in PLC/PRF/5 and A549 cells and release progeny into the culture medium was used to generate a derivative ORF3-deficient (DORF3) mutant whose third in-frame AUG codon of ORF3 was mutated to GCA. The DORF3 mutant in the culture medium of mutant RNA-transfected PLC/PRF/5 cells was able to infect and replicate within PLC/ PRF/5 and A549 cells as efficiently as the wild-type pJE03-1760F/wt virus. However, less than 1/100 of the number of progeny was detectable in the culture medium of DORF3 mutant-infected PLC/PRF/5 cells compared with wild-type-infected PLC/PRF/5 cells, and the HEV RNA level in the culture medium of DORF3 mutant-infected A549 cells was below or near the limit of detection. An immunocapture PCR assay revealed that the ORF3 protein is present on the surface of cell-culture-generated wild-type HEV but not on the DORF3 mutant. Wild-type HEV in the culture supernatant peaked at a sucrose density of 1.15-1.16 g ml , in contrast with the DORF3 mutant in culture supernatant, which banded at 1.27-1.28 g ml , similar to HEV in cell lysate and faecal HEV. These results suggest that the ORF3 protein is responsible for virion egress from infected cells and is present on the surface of released HEV particles, which may be associated with lipids.

Dengue virus (DENV) is one of the most important arthropod-borne pathogens that cause life-threatening diseases in humans. However, no vaccine or specific antiviral is available for dengue. As seen in other RNA viruses, the innate immune system plays a key role in controlling DENV infection and disease outcome. Although the interferon (IFN) response, which is central to host protective immunity, has been reported to limit DENV replication, the molecular details of how DENV infection is modulated by IFN treatment are elusive. In this study, by employing a gain-of-function screen using a type I IFN-treated cell-derived cDNA library, we identified a previously uncharacterized gene, C19orf66, as an IFN-stimulated gene (ISG) that inhibits DENV replication, which we named Repressor of yield of DENV (RyDEN). Overexpression and gene knockdown experiments revealed that expression of RyDEN confers resistance to all serotypes of DENV in human cells. RyDEN expression also limited the replication of hepatitis C virus, Kunjin virus, Chikungunya virus, herpes simplex virus type 1, and human adenovirus. Importantly, RyDEN was considered to be a crucial effector molecule in the IFN-mediated anti-DENV response. When affinity purification-mass spectrometry analysis was performed, RyDEN was revealed to form a complex with cellular mRNA-binding proteins, poly(A)-binding protein cytoplasmic 1 (PABPC1), and La motif-related protein 1 (LARP1). Interestingly, PABPC1 and LARP1 were found to be positive modulators of DENV replication. Since RyDEN influenced intracellular events on DENV replication and, suppression of protein synthesis from DENV-based reporter construct RNA was also observed in RyDEN-expressing cells, our data suggest that RyDEN is likely to interfere with the translation of DENV via interaction with viral RNA and cellular mRNA-binding proteins, resulting in the inhibition of virus replication in infected cells.

Ten murine monoclonal antibodies (MAbs) against a synthetic peptide corresponding to the well-conserved, C-terminal 24-amino acid portion of ORF3 protein of hepatitis E virus (HEV) were produced and characterized. Immunofluorescent assays using the anti-ORF3 MAbs revealed accumulation of ORF3 protein in the cytoplasm of PLC/PRF/5 cells transfected with ORF3-expressing plasmid or inoculated with cell-culture-generated HEV. The anti-ORF3 MAbs could capture HEV particles in culture medium and serum at variable efficiency of up to 61 and 49%, respectively, but not those in feces. By sandwiching between immobilized and enzyme-labeled anti-ORF3 MAbs in ELISA, ORF3 antigen was detected in the culture media with an HEV RNA titer of >10(6) copies/ml and increased in parallel with the increase in HEV load. HEV progenies in the culture supernatant, with ORF3 protein on the surface, banded at a low buoyant density of 1.15 g/cm(3) in sucrose. A representative anti-ORF3 MAb (TA0536) could partially neutralize the infection of cell-culture-generated HEV in a cell culture system. These results indicate that ORF3 protein, at least its C-terminal portion, is present on the surface of HEV virions released from infected cells and support a previously proposed assumption that ORF3 protein is associated with virus release from infected cells.

High prevalence of infection with high-risk human papilloma virus (HPV) ranging from 25 to 100% (average 31%) was observed in breast cancer (BC) patients in Singapore using novel DNA chip technology. Early stage of BC demonstrated higher HPV positivity, and BC positive for estrogen receptor (ER) showed significantly higher HPV infection rate. This unique association of HPV with BC in vivo prompted us to investigate a possible involvement of HPV in early stages of breast carcinogenesis. Using normal breast epithelial cells stably transfected with HPV-18, we showed apparent upregulation of mRNA for the cytidine deaminase, APOBEC3B (A3B) which is reported to be a source of mutations in BC. HPV-induced A3B overexpression caused significant γH2AX focus formation, and DNA breaks which were cancelled by shRNA to HPV18 E6, E7 and A3B. These results strongly suggest an active involvement of HPV in the early stage of BC carcinogenesis via A3B induction.

The roles of Type I interferon (IFN) in human immunodeficiency virus Type 1 (HIV-1) neuropathogenesis are poorly understood; both protective and deleterious effects of IFN signaling have been described. We used genetically modified mice deficient in the Type I IFN receptor (IFNRKO) to analyze the progress of HIV-1 brain infection and neuropathogenesis in the absence of IFN signaling. IFNRKO and wild-type (WT) mice on the 129xSv/Ev or C57BL/6 strain backgrounds were infected systemically with EcoHIV, a chimeric HIV-1 that productively infects mice. IFNRKO mice showed higher HIV-1 expression in spleen and peritoneal macrophages and greater virus infiltration into the brain compared to WT mice. Neuropathogenesis was studied by histopathological, immunohistochemical, immunofluorescence, and polymerase chain reaction analyses of brain tissues after the virus was inoculated into the brain by stereotaxic intracerebral injection. Both IFNRKO and WT mice showed readily detectable HIV-1 and brain lesions, including microglial activation, astrocytosis, and increased expression of genes coding for inflammatory cytokines and chemokines typical of human HIV-1 brain disease. Parameters of HIV-1 neuropathogenesis, including HIV-1 expression in microglia/macrophages, were significantly greater in IFNRKO than in WT mice. Our results show unequivocally that Type I IFN signaling and responses limit HIV-1 infection and pathogenesis in the brains of mice.