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为什么包皮环切降低HIV感染风险
Why Circumcision Lowers Risk of HIV

为什么包皮环切降低HIV感染风险

时代周刊
2013-4-17

作者:Alice Park

 

有前途的试验显示,包皮环切术可以降低HIV感染率,但到现在为止,研究人员并没有完全明白为什么。

 

现在,在MBIO杂志上发表的一项研究中,科学家们表示,生存在阴茎及其周围的细菌群落的改变可能部分地起了作用。

 

利用更快、更方便的基因测序最新技术,转化基因组学研究所(TGen)的Lance Price及其同事对一组乌干达男子包皮环切术前??及手术一年后采集自阴茎上的微生物群落标本进行了详细的基因分析。

 

在包皮环切手术前男性显示了相似的微生物群落,12个月后,包皮环切的男性窝藏的能在低氧条件下生存的细菌急剧减少。与未接受包皮环切的男性相比,总体上减少了81%的细菌,这可能对男性抵抗感染(如HIV)的能力具有极大的影响,Price说。先前的研究表明,包皮环切能降低男性感染艾滋病毒的风险高达50%,使得包皮环切术成为预防HIV感染的重要工具。为什么呢?大量的细菌可能会破坏被称为朗格汉斯细胞的特化免疫细胞激活免疫防御。通常,朗格汉斯细胞负责捕获入侵的微生物,如细菌或病毒,并递呈给免疫细胞以训练和引发身体识别并对入侵的病原体做出防御反应。但是,当细菌数量增加时,正如在未接受包皮环切的阴茎环境里的表现一样,炎症反应就会增加,这些细胞实际上开始利用入侵的微生物感染健康细胞,而不是仅仅展示它们。

 

这也许可以解释为什么未接受包皮环切的男性比切除包皮的男性更容易感染艾滋病毒,Price说,因为朗格汉斯细胞可直接将HIV提供给健康细胞。他的研究小组还在研究细胞因子水平上的变化如何受到细菌种群的影响。细胞因子是免疫细胞用来互相通讯的信号分子。

 

“在我们了解微生物方面正在进行一场真正的革命”,Price也是乔治·华盛顿大学职业与环境健康教授。“微生物几乎像其他器官系统,而我们才刚刚触及理解微生物和免疫系统之间相互作用的表面。”

 

先前的研究提示,肠道中的细菌种群的变化,可能会影响肥胖,其他研究发现微生物群落和癌症,哮喘和其他慢性疾病的风险之间潜在的关系。

 

新闻来源:http://healthland.time.com/2013/04/17/why-circumcision-lowers-risk-of-hiv/


TIME

Health & Family

AIDS

Why Circumcision Lowers Risk of HIV


By Alice Park

April 17, 2013

 

Promising trials hinted that circumcision could lower rates of HIV infection, but until now, researchers didn’t fully understand why.


Now, in a study published in the journal mBio, scientists say that changes in the population of bacteria living on and around the penis may be partly responsible.


Relying on the latest technology that make sequencing the genes of organisms faster and more accessible, Lance Price of the Translational Genomics Research institute (TGen) and his colleagues conducted a detailed genetic analysis of the microbial inhabitants of the penis among a group of Ugandan men who provided samples before circumcision and again a year later.


(MORE:  If Circumcision Rates Keep Falling, Health Costs and Infections Will Spike)


While the men showed similar communities of microbes before the operation, 12 months later, the circumcised men harbored dramatically fewer bacteria that survive in low oxygen conditions. They also had 81% less bacteria overall compared to the uncircumcised men, and that could have a dramatic effect on the men’s ability to fight off infections like HIV, says Price. Previous studies showed that circumcised men lowered their risk of transmitting HIV by as much as 50%, making the operation an important tool in preventing infection with the virus. Why? A high burden of bacteria could disrupt the ability of specialized immune cells known as Langerhans cells to activate immune defenses. Normally, Langerhans are responsible for grabbing invading microbes like bacteria or viruses and presenting them to immune cells for training, to prime the body to recognize and react against the pathogens. But when the bacterial load increases, as it does in the uncircumcised penile environment, inflammatory reactions increase and these cells actually start to infect healthy cells with the offending microbe rather than merely present them.


(MORE: Can New Circumcision Devices Help Fight AIDS in Africa?)


That may be why uncircumcised men are more likely to transmit HIV than men without the foreskin, says Price, since the Langerhans cells could be feeding HIV directly to healthy cells. His group is also investigating how changes in the levels of cytokines, which are the signaling molecules that immune cells use to communicate with each other, might be influenced by bacterial populations.


“There is a real revolution going on in our understanding of the microbiome,” says Price, who is also professor of occupational and environmental health at George Washington University. “The microbiome is almost like another organ system, and we are just scratching the surface of understanding the interplay between the microbiome and the immune system.”


Previous work suggested that changes in the bacterial populations in the gut, for example, could affect obesity, and other studies found potential connections between microbial communities and the risk for cancer, asthma and other chronic conditions.


MORE: Study Identifies Four New Genetic Markers For Severe Childhood Obesity



Alice Park @aliceparkny


Alice Park is a staff writer at TIME and covers health, medicine, nutrition and fitness.


Read more: http://healthland.time.com/2013/04/17/why-circumcision-lowers-risk-of-hiv/#ixzz2TbDuraiE

 
 
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