今天前程百利小编为大家分享的是托福听力的背景学习。备考托福听力就要把听力文本吃透分析彻底。这样不仅能积累背景材料，还能把听力的专业词汇积累起来一块背诵，为托托福听力打下坚实的基础。下面跟小编一起看一下寄生虫疫苗这篇文章吧!
An experimental leishmaniasis vaccine relies on eliciting an immune response to a protein from the saliva of the sand fly that carries the leishmania parasite, rather than on anything from the parasite itself. Cynthia Graber reports
Leishmaniasis is a sometimes fatal disease marked by skin ulcers, fever, and spleen and liver problems. It currently affects about 12 million people, mostly in the developing world, with about 2 million new infections annually. It’s caused by a parasite, which is spread by sand flies.
There is not yet a good vaccine against leishmaniasis. But researchers have shown that it may be worthwhile to target not the parasite—but its fly host. The report good results in non-human primates in the journal Science Translational Medicine.
Vaccines usually trigger our immune systems to rally against a pathogenic agent. If that agent should actually show up, the immune system can disarm it.
But in this case, scientists aimed at the carrier—the sand fly. When an infected fly bites a victim, it injects parasites and its own saliva. So the researchers subjected monkeys to repeated bites from uninfected sand flies, then to bites from infected sand flies. And the monkeys bitten first by uninfected flies were partially protected when confronted with the leishmaniasis parasite. Seems that exposure to fly saliva alone could elicit an immune response.
The researchers then determined that one particular protein in the sand fly’s saliva kicked the immune system into action. A vaccine based on that protein offered partial protection, with 7 of 10 monkeys that got it developing smaller ulcers and a stronger immune response than their unvaccinated peers when infected with the parasite.
This protein can be generated and purified easily from E. coli, which means that it’s possible to get large quantities of it to produce a potential future human vaccine against leishmaniasis. Which would make this saliva-based protection nothing to spit at.
疑难词汇：
Eliciting v. 诱发，刺激;引起(elicit的现在分词)
Protein n. 蛋白质;朊adj. 蛋白质的
Saliva n. 唾液;涎
Parasite n. 寄生虫;食客
Ulcer n. [病理] 溃疡;腐烂物;道德败坏
Spleen n. 脾脏;坏脾气;怒气
Vaccine n. 疫苗;牛痘苗adj. 疫苗的;牛痘的
Pathogenic adj. 致病的;病原的;发病的(等于pathogenetic)
Disarm vt. 解除武装;裁军;缓和vi. 放下武器;裁减军备
长难句解析：
1. When an infected fly bites a victim, it injects parasites and its own saliva.
难句类型：
When引导的时间状语从句
句子主干：
it injects parasites and its own saliva
难句拆分：
When an infected fly bites a victim ，When引导的时间状语从句
2. And the monkeys bitten first by uninfected flies were partially protected when confronted with the leishmaniasis parasite..
难句类型：
When引导的时间状语从句
句子主干：
they don't really share food
难句拆分：
when confronted with the leishmaniasis parasite，When引导的时间状语从句
文本结构特点：
本篇文章主要讲的是研究表明疫苗旨在依赖于一个实验性的利什曼病疫苗诱发与沙蝇免疫反应的蛋白质唾液,而不是从寄生虫本身。寄生虫疫苗旨在预防苍蝇带来的疾病。
好了，以上就是前程百利小编为大家整理的备考托福听力背景材料以及专业词汇的学习。大家学会了吗?希望能在备考托福的路上助大家一臂之力。预祝大家在托福考试中取得好成绩。
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