Anti-HBV activity of TRL mediated by recombinant adenovirus

Inhibition of KIT RNAi mediated with adenovirus in gastrointestinal stromal tumor xenograft

AIM: To investigate a therapeutic method for gastrointestinal stromal tumor (GIST) based on KIT RNA interference (RNAi) with AdMax adenovirus.

METHODS: KIT short hairpin RNA (shRNA), whose lateral sides were decorated with restriction endonuclease sequences, was designed. T₄ DNA ligase catalyzed the joint of the KIT shRNA and the green fluorescent protein-containing PDC316-EGFP-U6 to form PDC316-EGFP-U6-KIT. Homologous recombination of AdEGFP-U6-KIT was performed with the AdMax system. Heterotopically transplanted GISTs were established in nude mice. AdEGFP-U6-KIT was intratumorally injected. The volume, inhibition ratio of tumor and CD117 expression of GIST graft tumor in nude mice were compared between test and control groups.

RESULTS: The length of KIT shRNA was determined to be about 50bp by agarose electrophoresis. Gene sequencing detected the designed KIT RNAi sequence in PDC316-EGFP-U6-KIT. After transfection with AdEGFP-U6-KIT, 293 cells displayed green fluorescence. The physical and infective titers of AdEGFP-U6-KIT were 5 × 10¹¹ viral particles/mL and 5.67 × 10⁷ plaque forming units/mL, respectively. The mean volume of the grafted tumor was significantly smaller in test mice than in control mice (75.3 ± 22.9 mm³vs 988.6 ± 30.5 mm³, t = -18.132, P < 0.05). The inhibition ratio of the tumors was 59.6% in the test group. CD117 positive expression was evident in two cases (20%) in the test group and 10 cases (100%) in the control group (χ² = 10.2083, P < 0.005).

CONCLUSION: AdEGFP-U6-KIT is successfully constructed, and KIT RNAi mediated with Admax vector system can effectively inhibit the expression of the KIT gene and the growth of GIST in nude mice.

Antiviral gene therapy

This chapter describes the major gene therapeutic approaches for viral infections. The vast majority of published approaches target severe chronic viral infections such as hepatitis B or C and HIV infection. Two basic gene therapy strategies are introduced here. The first involves the expression of a protein or an RNA that inhibits viral replication by targeting crucial steps of the viral life cycle or by interfering with a cellular factor required for virus replication. The major limitation of this approach is that primary levels of gene modification have generally not been sufficient to reduce the availability of target cells permissive for virus replication to a level that significantly decreases overall viral load. Thus, investigators have banked on the expectation that gene-protected cells have a sufficient selective advantage to accumulate and gain prevalence over time, a prediction that so far could not be confirmed in clinical trials. In vivo levels of gene modification can be improved, however, by introducing an additional selectable marker. In addition, a secreted antiviral gene product that exerts a bystander effect could significantly reduce overall virus replication despite relatively low levels of gene modification. In addition to these direct antiviral approaches, several strategies have been developed that employ or aim to enhance host immune responses. The innate immune response has been enhanced, for example, by the in vivo expression of interferons. Alternatively, T cells can be grafted with recombinant receptors to boost adaptive virus-specific immunity. These approaches are especially promising for chronic virus infection, where natural immune responses are evidently not sufficient to effectively control virus replication.