Adenovirus DNA synthesized in the presence of aphidicolin

Induction of the human heat shock promoter HSP70B by nutritional stress: implications for cancer gene therapy

BACKGROUND

We designed and tested, in vitro, an adenoviral construct containing the feline interleukin-12 (IL-12) gene under control of the heat-inducible promoter HSP70B. This construct, AdhspfIL12, was used in a phase I trial in feline soft tissue sarcomas. During the course of our experiments, we noted that IL-12 was being produced in the transfected Crandell Feline Kidney (CrFK) cells under certain conditions even in the absence of hyperthermia. This observation was further explored to identify the cause of this unintended HSP70B induction.

MATERIALS AND METHODS

We used real-time PCR as a sensitive method to quantitatively detect the presence of even small amounts of IL-12 mRNA. This served as a surrogate indicator of HSP70B induction. Various conditions were tested to induce the heat shock promoter, including nutritional deprivation, radiation and changes in pH.

RESULTS

Nutritional stresses, specifically the absence of glucose and glutamine, could induce the heat shock promoter, thus, resulting in production of the downstream gene product. Other factors known to trigger the heat shock response, pH change, and reactive oxygen species production were also studied but were not found to contribute to heat shock promoter induction in our setting.

CONCLUSIONS

The human heat shock promoter (HSP70B) is reported to be an efficient and tightly regulated promoter. We discovered, using sensitive real-time PCR techniques, that it can also be induced in response to cellular nutrient stresses. The pros and cons of this phenomenon and its implications for cancer gene therapy are discussed.

Susceptibility of Autographa californica multiple nucleopolyhedrovirus to inhibitors of DNA replication

The objectives of this study were to develop methods to evaluate the susceptibility of the type baculovirus AcMNPV to various antiviral compounds and to select potential inhibitors for investigating baculovirus DNA replication. In concert with the classical cytopathic effects (CPE) and cytotoxicity inhibition assays, two approaches, which could be amenable for high throughput application for evaluating several classes of known antiviral compounds were developed. (i) An indirect approach based on spectrofluorimetric analysis of EGFP expression in Sf21 cells infected with a recombinant AcMNPV (AcEGFP) and (ii) a direct DNA quantitative assay based on quantitative real time PCR (qPCR). Initial CPE results suggested that of 21 compounds tested, aphidicolin, abacavir, camptothecin, (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU), l-mimosine, hydroxyurea and phosphonoacetic acid (PAA) were selective inhibitors of AcMNPV replication. Consistent with the CPE results, the EGFP fluorescence and the qPCR of viral DNA accumulation exhibited a dose dependent depression of EGFP expression and DNA accumulation, respectively, in infected cells exposed to them. The inhibitory effects of aphidicolin, abacavir, l-mimosine and hydroxyurea on AcMNPV DNA replication were reversible. Taken together, both spectrofluorimetric and qPCR assays are suitable and rapid quantitative approaches to investigate inhibitors of baculovirus DNA replication in infected cells.