致癌病毒如何阻挡人体免疫反应

科学家已经发现一种致癌病毒可逃避人体的免疫应答反应。这一发现可能有助于解释为什么一些治疗癌症的方法对某些癌症治疗会失败。

EB病毒是一种疱疹病毒科，每年该病毒会引起估计20，0000例新发癌症病例,包括淋巴瘤、鼻咽癌和胃癌。好的抗病毒药物可以帮助成千上万的患有这些癌症的病人。

包括EB病毒在内的许多病毒,通常会携带一种小分子核糖核酸,它们会干扰感染中宿主细胞内的自然过程。已知的小分子核糖核酸病毒会防止宿主细胞死亡,促进宿主细胞生长,抑制宿主细胞内病毒的防御能力。然而,科学家们还不知道哪个小分子核糖核酸病毒具有该功能。

研究人员确定这些小分子核糖核酸是由几个疱疹病毒组成,这些病毒阻止人类先天免疫系统的一个干扰素反应组成部分。体内免疫细胞释放干扰素来防止病毒复制,而这往往导致感染的宿主细胞生长放缓或死亡。研究人员发现,一些疱疹病毒已经具有独立的相似进化机制以阻止宿主的干扰素反应。

“我非常惊讶的是所有这些不同的病毒会聚集在一起以阻止人体的防御机制。”Sullivan说。

有时干扰素会与化疗方法结合治疗淋巴瘤。虽然这对某些癌症是一个有效的治疗方法,但对其他癌症却没有明显影响。最新研究表明干扰素疗法对EB病毒引发淋巴瘤比较有效。（转化医学网360zhyx.com）

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原文：Scientists at The University of Texas at Austin and the University of California at San Francisco have revealed how a type of cancer-causing virus outwits the human body's immune response. The discovery might help explain why some cancer therapies fail to treat certain cancers .

Epstein Barr Virus (EBV), a virus of the herpes family, causes an estimated 200,000 cancers every year, including lymphomas, nasopharyngeal cancers and some stomach cancers. Better anti-viral drugs could help thousands of people suffering from these cancers.

Many viruses, including EBV, carry small molecules called microRNAs that they use to hijack natural processes in a host's cells during an infection. Viral microRNAs are known to prevent host cell death, promote host cell growth and dampen the host cell's viral defenses. However, scientists don't yet know which viral microRNAs perform which functions.

Jennifer Cox, a graduate student working with Associate Professor Chris Sullivan at UT Austin, identified microRNAs made by several herpes viruses that block a component of a human's innate immune system called the interferon response. Immune cells within the body release interferon to prevent viral replication, and this often results in slower growth or death of infected host cells. The researchers found that several herpes viruses have independently evolved similar mechanisms to block the host's interferon response.

"I was actually surprised that all these different viruses had converged on the same mechanism for blocking the body's defenses," said Sullivan. 

Interferon is sometimes used in combination with chemotherapy to treat lymphomas. While an effective treatment for some cancers, it does not significantly affect others. This latest research has demonstrated that EBV lymphoma cells are less susceptible to interferon therapy.