As a genetic adjuvant, CTA improves the immunogenicity of DNA vaccines in an ADP-ribosyltransferase activity- and IL-6-dependent manner.

Cholera toxin (CT) and its subunits (A and B) have been intensively investigated as adjuvants for protein-based vaccines. Their underlying mechanisms vary with respect to the inoculation route used. By fusing the CTA gene to either the HIV-1-derived Tat-Rev-Vif-Integrase-Nef fusion gene or the OVA gene, our study showed that the fusion of CTA in these DNA vaccines had no cytotoxic effect in vitro and significantly improved both the quantity and quality of the elicited CD8(+) T cell responses. Further experiments identified that the fusion of CTA in these DNA vaccines augmented the secretion of IL-6 in a manner that was dependent on its ADP-ribosyltransferase activity, and protein kinase A (PKA) was found to be the major mediator of its downstream signaling. By site-directed mutagenesis of the ADP-ribosyltransferase catalytic center and in vivo RNAi, we demonstrated that the ADP-ribosyltransferase activity and the upregulation of IL-6 were required for the CTA gene-mediated adjuvant effect. These findings demonstrate that when fused to an immunogen gene, the CTA gene could serve as a potent genetic adjuvant, providing new insights into the mechanisms of CTA as an adjuvant.

[Effect of early high-loading-dose tirofiban on platelet activity in patients with acute ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention].

OBJECTIVE: To investigate the effect of early high-loading-dose tirofiban on platelet activity for patients with acute ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention. METHODS: A total of 120 acute STEMI patients were treated with 300 mg aspirin and 600 mg loading dose clopidogrel and randomized to high-dose tirofiban (25 µg/kg bolus followed by 0.15 µg×kg(-1)×min(-1) infusion for 36 hours, n = 40), standard-dose tirofiban (10 µg/kg bolus followed by 0.15 µg×kg(-1)×min(-1) infusion for 36 hours, n = 40) or control (no tirofiban, n = 40) before angiography. Inhibition of platelet aggregation (IPA) was assessed before angiography, at 10 min and 24 hours after tirofiban infusion, and at 12 and 24 hours after stopping tirofiban infusion by the thrombelastography assay. RESULTS: There was no significant difference in baseline of IPA between the 3 groups (P > 0.05). IPA was significantly higher in high-dose tirofiban group compared with standard-dose tirofiban and no tirofiban group at 10 minutes after tirofiban infusion [(84.2 ± 12.0)% vs. (67.8 ± 26.8)% and (31.5 ± 21.9)%, all P < 0.01]. At 24 hours after tirofiban infusion, the IPA of high-dose and standard-dose tirofiban was similar [(93.0 ± 9.8)% vs. (88.5 ± 18.1)%, P > 0.05] and was significantly higher than no tirofiban group [(40.4 ± 22.8)%, all P < 0.01]. IPA was similar at 12 and 24 hours after stopping tirofiban use among the 3 groups (all P > 0.05). The maximum amplitude of high-dose tirofiban and standard-dose tirofiban groups at different time points was similar (all P > 0.05), and maximum amplitude in both tirofiban groups was significantly lower than in no tirofiban group at 10 min [(47.2 ± 7.6) mm and (50.0 ± 9.8) mm vs. (57.7 ± 6.5) mm, all P < 0.01] and at 24 hours after stopping tirofiban infusion [(54.6 ± 5.6) mm and (54.3 ± 9.0) mm vs. (59.6 ± 4.0) mm, all P < 0.01]. CONCLUSION: Early use of high-loading-dose of tirofiban on top of 600 mg loading dose clopidogrel is more efficient on inhibiting platelet activity than standard dose of tirofiban in patients with acute STEMI undergoing primary primary percutaneous coronary intervention.