The development of a safe and efficient dengue vaccine represents a global challenge in public health. Chimeric dengue viruses (DENV) based on an attenuated flavivirus have been well developed as vaccine candidates by using reverse genetics. In this study, based on the full-length infectious cDNA clone of the well-known Japanese encephalitis virus live vaccine strain SA14-14-2 as a backbone, a novel chimeric dengue virus (named ChinDENV) was rationally designed and constructed by replacement with the premembrane and envelope genes of dengue 2 virus. The recovered chimeric virus showed growth and plaque properties similar to those of the parental DENV in mammalian and mosquito cells. ChinDENV was highly attenuated in mice, and no viremia was induced in rhesus monkeys upon subcutaneous inoculation. ChinDENV retained its genetic stability and attenuation phenotype after serial 15 passages in cultured cells. A single immunization with various doses of ChinDENV elicited strong neutralizing antibodies in a dose-dependent manner. When vaccinated monkeys were challenged with wild-type DENV, all animals except one that received the lower dose were protected against the development of viremia. Furthermore, immunization with ChinDENV conferred efficient cross protection against lethal JEV challenge in mice in association with robust cellular immunity induced by the replicating nonstructural proteins. Taken together, the results of this preclinical study well demonstrate the great potential of ChinDENV for further development as a dengue vaccine candidate, and this kind of chimeric flavivirus based on JE vaccine virus represents a powerful tool to deliver foreign antigens.

The attenuated Japanese encephalitis virus (JEV) strain SA14-14-2 has been successfully utilized to prevent JEV infection; however, the attenuation determinants have not been fully elucidated. The envelope (E) protein of the attenuated JEV SA14-14-2 strain differs from that of the virulent parental SA14 strain at eight amino acid positions (E107, E138, E176, E177, E264, E279, E315, and E439). Here, we investigated the SA14-14-2-attenuation determinants by mutating E107, E138, E176, E177, and E279 in SA14-14-2 to their status in the parental virulent strain and tested the replication capacity, neurovirulence, neuroinvasiveness, and mortality associated with the mutated viruses in mice, as compared with those of JEV SA14-14-2 and SA14. Our findings indicated that revertant mutations at the E138 or E107 position significantly increased SA14-14-2 virulence, whereas other revertant mutations exhibited significant increases in neurovirulence only when combined with E138, E107, and other mutations. Revertant mutations at all eight positions in the E protein resulted in the highest degree of SA14-14-2 virulence, although this was still lower than that observed in SA14. These results demonstrated the critical role of the viral E protein in controlling JEV virulence and identified the amino acids at the E107 and E138 positions as the key determinants of SA14-14-2 neurovirulence.

Hepatitis B virus X protein (HBx) is a multi-functional regulatory protein that is known to be involved in viral proliferation, transcriptional activation and cell growth control. However, the actual role of HBx in cell growth control remains controversial. In this study, the impact of HBx on cell growth in vitro and in vivo was further investigated. HBx was able to inhibit the growth of hepatocellular carcinoma (HCC) cells and induce G2/M arrest in vitro. Moreover, unlike many other G2/M arrest mechanisms, HBx did not inhibit cyclin B1-CDK1 kinase activity, but it persistently activated the cyclin B1-CDK1 kinase. In vivo, HBx inhibited tumor cell growth and induced apoptosis as well as inhibited the growth of vascular endothelial cells. In conclusion, HBx induced G2/M arrest and apoptosis through sustained activation of cyclin B1-CDK1 kinase, and negatively regulated cell growth in vitro and in vivo.

Although the treatment of lung carcinoma has improved, at least 65% of patients with this tumor succumb to progressive disease. Measles virus oncolytic therapy has been reported to be effective in reducing tumor burden in immunocompetent or nude mice; however, its potential to reduce tumor burden in lung carcinoma remains to be determined. Herein, we report the potent antitumor effects of a live attenuated measles vaccine virus Hu-191 strain (MV) against lung carcinoma. Immunocompetent C57BL/6 mice bearing Lewis lung carcinoma (LLC) cells were treated with MV (1x104 to 1x106 CCID50/ml) once every other day for 10 days. Our results showed that treatment with MV effectively suppressed tumor growth and significantly prolonged the survival time of tumor-bearing animals. Histological examination revealed that the antitumor effects of MV therapy may result from increased induction of apoptosis, tumor necrosis and elevated lymphocyte infiltration. Our data suggest that MV, one of the widely used vaccines in China, has the ability to inhibit the growth of mouse lung carcinoma and may prove useful in the further exploration of the application of this approach in the treatment of human advanced lung cancer.