Serious outbreaks of severe acute respiratory syndrome (SARS), caused by the newly discovered coronavirus SARS-CoV, occurred between late 2002 and early 2003 and there is an urgent need for effective antiviral agents. RNA interference in animals and post-transcriptional gene silencing plants is mediated by small double-stranded RNA molecules named small interfering RNA (siRNA). Recently, siRNA-induced RNA interference(RNAi) may provide a new approach to therapy for pathogenic viruses, e.g. HIV and HCV. In this study, the silencing potential of seven synthetic siRNAs against SARS-CoV leader, TRS, 3'-UTR and Spike coding sequence have been applied to explore the possibility for prevention of SARS-CoV infection. We demonstrate that siRNAs directed against Spike sequences and the 3'-UTR can inhibit the replication of SARS-CoV in Vero-E6 cells, and holds out promise for the development of an effective antiviral agent against SARS-CoV.

Screened modified gravity (SMG) is a kind of scalar-tensor theories with screening mechanisms, which can generate screening effect to suppress the fifth force in high density environments and pass the solar system tests. Meanwhile, the potential of scalar field in the theories can drive the acceleration of the late universe. In this paper, we calculate the parameterized post-Newtonian (PPN) parameters γ and β, the effective gravitational constant G eff and the effective cosmological constant Λ for SMG with a general potential V and coupling function A. The dependence of these parameters on the model parameters of SMG and/or the physical properties of the source object are clearly presented. As an application of these results, we focus on three specific theories of SMG (chameleon, symmetron and dilaton models). Using the formulae to calculate their PPN parameters and cosmological constant, we derive the constraints on the model parameters by combining the observations on solar system and cosmological scales.

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Emergent theory assumes that the universe originates from an Einstein static (ES) state rather than the big bang singularity, and, thus, provides a possible way to resolve the singularity problem. The stability against all kinds of perturbations that ensures the past eternity of the ES state is crucial for a successful realization of the emergent scenario. Recently, it has been found that in the context of the Jordan-Brans-Dicke (JBD) theory there exists a stable ES solution under homogenous and anisotropic perturbations. In this paper, we extend the analysis to the stability against tensor and inhomogeneous scalar perturbations. We find that, different from general relativity and fðRÞ theory, a stable ES solution is allowed in the JBD theory when different kinds of perturbations are considered, although the stability conditions are tighter for tensor and inhomogeneous scalar perturbations than those for homogenous and anisotropic ones.

We have previously shown that a plasmid (pE) encoding the Japanese encephalitis virus (JEV) envelope (E) protein conferred a high level of protection against a lethal viral challenge. In the present study, we used adoptive transfer experiments and gene knockout mice to demonstrate that the DNA-induced E-specific antibody alone can confer protection in the absence of cytotoxic T-lymphocyte (CTL) functions. Plasmid pE administered by either intramuscular or gene gun injection produced significant E-specific antibodies, helper T (Th)-cell proliferative responses, and CTL activities. Animals receiving suboptimal DNA vaccination produced low titers of anti-E antibodies and were only partially or not protected from viral challenge, indicating a strong correlation between anti-E antibodies and the protective capacity. This observation was confirmed by adoptive transfer experiments. Intravenous transfer of E-specific antisera but not crude or T-cell-enriched immune splenocytes to sublethally irradiated hosts conferred protection against a lethal JEV challenge. Furthermore, experiments with gene knockout mice showed that DNA vaccination did not induce anti-E titers and protective immunity in Ig ؊/؊ and I-A␤ ؊/؊ mice, whereas in CD8␣ ؊/؊ mice the pE-induced antibody titers and protective rate were comparable to those produced in the wild-type mice. Taken together, these results demonstrate that the anti-E antibody is the most critical protective component in this JEV challenge model and that production of anti-E antibody by pE DNA vaccine is dependent on the presence of CD4 ؉ T cells but independent of CD8 ؉ T cells.

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