HTLV-1 is a human retrovirus responsible for adult T-cell leukemia (ATL) and certain other clinical disorders. The viral Tax oncoprotein plays a central role in HTLV-1 pathogenicity, mainly due to its capacity of inducing the transcriptional activity of various transcriptional factors like NFқB. Eucalyptus camaldulensis (Ec) is considered as a traditional medicinal plant with valuable therapeutic effects. Here we evaluated the activity of its ethanolic leave extract on different Tax activities by testing its influence on Tax-induced activity of NFқB and HTLV-1 LTR in Jurkat cells. Our results showed that Ec inhibited Tax induced activation of NFқB -, SRF- dependent promoters and HTLV-1 LTR. Ec extract has no effect on the binding of Tax to NFқB while it strongly prevented the degradation of IҝBα induced by Tax probably as a result of preventing the link between Tax and IKKγ. In addition, increasing the cellular level of P-TEFb-cyclinT1 significantly reduced the inhibitory effect of Ec on Tax activities, probably by preventing the interaction between Tax and P-TEFb-cyclin T1. The 40%-MeOH fraction of this extract, which is rich with polyphenols, offered the highest inhibitory effect against Tax activities. Further studies are required for the isolation and identification of active component/s in this extract which may be developed in the future as preventive/curing drugs for HTLV-1 related diseases.

HTLV-1 是导致成人 T 细胞白血病 (ATL) 和某些其他临床疾病的人类逆转录病毒。病毒税癌蛋白在 HTLV-1 致病性中起核心作用，主要是由于其能够诱导各种转录因子（如 NFқB）的转录活性。Eucalyptus camaldulensis ( Ec ) 被认为是具有宝贵治疗作用的传统药用植物。在这里，我们通过测试其对 Jurkat 细胞中 NFқB 和 HTLV-1 LTR 的税收诱导活性的影响来评估其乙醇叶提取物对不同税收活动的活性。我们的结果表明，Ec抑制了税收诱导的 NFқB -、SRF 依赖性启动子和 HTLV-1 LTR 的激活。欧共体提取物对税收与 NFқB 的结合没有影响，但它有力地阻止了税收引起的 IҝBα 的退化，这可能是防止税收与 IKKγ 之间的联系的结果。此外，增加 P-TEFb-cyclinT1 的细胞水平显着降低了Ec对 Tax 活动的抑制作用，可能是通过阻止 Tax 和 P-TEFb-cyclin T1 之间的相互作用。该提取物的 40%-MeOH 部分富含多酚，对税收活动的抑制作用最高。需要进一步研究以分离和鉴定该提取物中的活性成分，这些成分可能在未来开发为 HTLV-1 相关疾病的预防/治疗药物。