Demonstration of Tightly Radiation-Controlled Molecular Switch Based on CArG Repeats by In Vivo Molecular Imaging.

PURPOSE: Promoters developed for radiogene therapy always show non-negligible transcriptional activities, even when cells are not irradiated. This study developed a tightly radiation-controlled molecular switch based on radiation responsive element (CArG) repeats for in vivo molecular imaging using the Cre/loxP system. PROCEDURES: Different numbers of CArG repeats were cloned as a basal promoter directly, and its pre- and postirradiation transcriptional activities were analyzed by luciferase assay. Nine CArG repeats (E9) were chosen for use as a radiation-controlled molecular switch for the Cre/loxP system, and the feasibility of the switch in vitro and in vivo was demonstrated by luciferase assay and bioluminescence imaging, respectively. RESULTS: The E9 promoter, which exhibits extremely low transcriptional activity, showed a 1.8-fold enhancement after irradiation with a clinical dose of 2 Gy. Both in vitro and in vivo results indicated that E9 is relatively inert but sufficient to trigger the Cre/loxP system. The luciferase activity of stable H1299/pSTOP-FLuc cells transfected with pE9-NLSCre and exposed to 2-Gy radiation can reach 44 % of that of the same cells transfected with pCMV-NLSCre and not subjected to irradiation. By contrast, no appreciable difference was observed in reporter gene expression in both H1299/pSTOPFluc cells and tumors transfected with pE4Pcmv-NLSCre before and after irradiation, because the strong basal transcriptional activity of the CMV promoter, which acts as a copartner of E4, masked the response of E4 to radiation. CONCLUSIONS: Our results provide detailed insight into CArG elements as a radiation-controlled molecular switch that can facilitate the development of radiogene therapy.

[Comparison of effectiveness between two HIV screening strategies in outpatient setting].

OBJECTIVE: To determine whether non-targeted testing strategy (screening all patients with blood sample withdrawn) could identify more patients with newly diagnosed HIV infection than symptom and risk behavior based targeted testing strategy or not. METHODS: Controlled trial design was applied in this study.From July to November 2011, outpatient department of L and J county hospital in Guangxi province were selected to conduct the targeted strategy and non-targeted strategy respectively. The two counties had similar population, outpatient volume, previous testing rate and number of newly identified HIV cases.Outpatients older than 15 years were recruited as study subjects, with 62 106 person time in L hospital and 58 257 in J hospital. Data about visit number, persons receiving HIV testing and HIV positive cases were collected by outpatient department. Chi-square test was used to compare the percentage of newly identified HIV cases, HIV positive detection rate and proportion of cases in early AIDS phase between two strategies. RESULTS: During the study period, 9.69% (5627/58 057) of all outpatients in J hospital with non-targeted strategy and 1.38% (859/62 106) of all outpatients in L hospital with targeted strategy received HIV test. The average age of patients receiving HIV testing was 46.23 ± 16.81 and 40.75 ± 15.48 respectively, which was statistically different (t = 8.81, P < 0.05). The percentage of newly identified HIV cases was significantly greater in J hospital (0.03% (19/58 057)) than that in L hospital (0.02% (10/62106)) (P < 0.05) while the HIV positive detection rate was lower in J hospital (0.34% (19/5627)) than that in L hospital (1.16% (10/859)) (χ(2) = 9.66, P < 0.05). CONCLUSION: In a concentrated epidemic, a hospital based non-targeted strategy could detect more unidentified HIV cases than targeted strategy.