艾滋病的盲区：揭开男-男同性恋传播HIV机理
2010-02-27 10:39:05 来源: 南方周末(广州)
同性恋并不等于艾滋病，但是，同性恋却与艾滋病密切相关。这种密切相关体现为，同性恋人群一直是艾滋病的薄弱防区，相当于这一领域的盲区。
2009年同志运动“骄傲周”中的一位男同性恋者
2008年同性恋运动游行上一对拥吻的同志情侣 图/Flikr
南方周末2月27日报道 同性恋并不等于艾滋病，但是，同性恋却与艾滋病密切相关。这种密切相关体现为，同性恋人群一直是艾滋病的薄弱防区，相当于这一领域的盲区。
艾滋病首先于1981年6月5日在美国洛杉矶5名男-男同性恋者身上发现。此后又发现，男-男同性恋者之间艾滋病传染的几率高于艾滋病的其他几种传播方式，即异性性行为、血液传播和母婴传播等。同时，男-男同性恋传播艾滋病的几率也远大于女-女同性恋。究其原因，有两大类。一是生物医学原因，二是行为方式的原因。现在，艾滋病的这一盲区正在变得明亮起来。
艾滋病是由人免疫缺陷病毒（HIV）引起的，但HIV为何容易在男-男同性恋者之间传播呢？现在美国加利福尼亚大学圣迭戈艾滋病研究中心（CFAR）的传染病副教授、病毒发病机理研究室主任戴卫·史密斯（Davey M. Smith）等人最新的研究揭示了其中的一些奥秘，例如，HIV在精浆中以RNA（核糖核酸）的形式在发生性关系的男-男同性恋者之间传播。
史密斯等人收集了6对男-男同性恋者的血液和精液样本进行研究，发现了HIV在同性恋者之间传播的方式。
RNA病毒颗粒是元凶
现在已知，全世界大多数HIV的感染是由于暴露于精液中的HIV造成的。精液是由精子、蛋白质、免疫细胞和精浆等构成的。如果一名男性已经感染HIV或是艾滋病患者，其精液中的精子、精浆和免疫细胞中都可能会有HIV。
但是，精浆中的HIV是以RNA病毒颗粒的形式存在，但精子和免疫细胞中的HIV则以DNA的形式存在，即前病毒DNA。用系统发生分析法，即比较遗传特征的方法可以知道HIV是如何在有性关系的男性之间传播的。因为，系统发生模式可以让研究人员评估不同病毒群的起源时间。因此，通过分析从同性恋伴侣血液和精液中提取的HIV的基因序列，可以确认迅速突变的HIV的来源。
史密斯的研究小组发现，被感染的同性恋者的HIV共享有一个最近共有的病毒祖先，它来自源性伴侣（首先感染了HIV并由他们把病毒传染给其他性伴侣的男性同性恋者）的精浆，而不是源性伴侣精子细胞中的前病毒DNA。
这一发现的意义非常重要。因为，此前人们并不知道通过性行为发生HIV感染时是通过HIV 的RNA病毒颗粒传染还是通过整合后的HIV前病毒DNA传染。但是，通过对这两种HIV病毒形式（RNA和DNA）的基因差异与通过同性性关系而新近感染了HIV的同性恋者身上提取的HIV的基因差异进行比较，研究人员最终确认，是精浆中的HIV的RNA病毒颗粒造成对男性性伴侣的传染。
史密斯认为，这一发现对阻止HIV的传播很有帮助。因为，如果知道了感染病毒的来源，研究人员就可能研发新的疫苗、阴道微生物杀灭剂和药物来防治经性途径的HIV传播。
当然，由于这一研究只包含几对男-男同性恋者，可能并不能解释所有性传播途径的感染，尤其是异性性行为的HIV传播，例如，男性对女性的传染。但是，由于大多数通过性行为染上HIV的女性是暴露于男性的精液而感染的，所以精浆中的HIV的RNA病毒颗粒有可能是疾病传播的真凶。但是，史密斯认为，这还需要进一步的研究来证实。
这一研究当然也证明，男性精浆中的HIV的RNA病毒颗粒最具危险。这也可能是为何男－男同性恋者比较容易受HIV感染的原因。
纽约国际抗艾滋病疫苗中心正在致力于艾滋病疫苗的研发 工作。
助纣为虐的其他因素
目前，公共卫生专家倾向于用“发生同性性行为的男子”来称呼这类同性恋人群，简称MSM。而MSM人群的其他生物和生理特性也为HIV的传播创造了有利机会。
MSM人群主要的性行为之一是肛交。与异性性行为相比，直肠弹性不及阴道，而且直肠比较脆弱，直肠黏膜较薄，更容易破损。在直肠破损时，精液里含有的大量HIV就很容易进入人体，感染T细胞。现在，史密斯的研究小组发现是精浆中的RNA病毒颗粒进行感染的，因此，RNA病毒颗粒与脆弱和破损的直肠结合起来便成为MSM人群最容易染上HIV的原因之一。
另一方面，精浆中的RNA病毒颗粒成为感染的真凶也能解释一种情况，即MSM人群通过性行为感染HIV的几率更高。世界卫生组织2008年的新统计表明，全球大约70％-80％的HIV感染者是通过性行为发生的。发生一次无保护性交后，在MSM人群中感染HIV的几率约为0.5%-3%；但在异性性行为中，男传女的几率约为0.1%-0.2%，女传男的几率大约是0.03%-0.1%。以此来换算，MSM人群一次无保护的性交染上HIV的几率是同样条件下男传女的5-15倍，女传男的16-30倍。
此外，男性精液中的一些特殊物质也为HIV的传播起到了助纣为虐的作用。例如，德国研究人员发现，人类精液中的前列腺酸性磷酸酶（PAP）能够极大提高HIV的感染能力。研究人员从精液中收集了多肽和小蛋白分子，并在细胞培养基中观测了它们对HIV易感性的作用。结果表明，PAP多肽能够强有力地促进HIV的传播。而且，当这些PAP片断集合成淀粉样原纤维时，它们的活性最强。
所以，这些淀粉样原纤维被称为HIV感染的精液源性增强因子（SEVI），它们的作用是，通过捕获HIV病毒颗粒来促进HIV感染，并促进其与T细胞融合，从而将HIV病毒的易感性提高几个数量级，有时甚至提高10万倍。研究人员也在HIV易感小鼠模型上检验了这些纤维的作用，结果发现，同时注射该纤维和HIV病毒的小鼠血液中HIV前病毒DNA的含量是单纯注射HIV小鼠的5倍。
尽管尚无研究证明精液中的PAP在MSM人群中更强大，在异性恋中就减弱，但综合多种因素，男-男性行为是最危险的HIV传播途径之一。
社会和文化原因
毫无疑问，MSM人群最容易导致艾滋病的传播还在于社会和文化原因。无论是在对同性恋较为开放的西方还是在较为保守的东方和非洲，同性恋都不为社会所见容。这就造成了同性恋的地下状态，其性行为有几个特点。一是多个性伴侣；二是随意性大，在酒吧、公园、卫生间，甚至街头巷尾等进行一次性的性行为；三是不使用安全套。
这些特点更容易造成HIV在MSM人群中的传播。但同时，社会对于同性恋的不见容还造成了另一种隐性恶果。由于要掩饰自己的同性恋倾向，许多同性恋者不得不与异性结婚，用组成家庭的形式来加以掩盖，但同时又不放弃同性性行为。在与多个同性有不安全性行为后，又可能回家与妻子发生性行为，这就可能把HIV传播给家人和其他普通人群。这既是艾滋病更大的盲区，也是社会的盲区和更大的隐性悲剧。
2009年7月20日一期的英国医学杂志《柳叶刀》发表的一份研究表明，非洲一些地区男同性恋者的艾滋病感染率是其他地区男性的10倍。非洲撒哈拉地区的男-男同性间无保护措施的性行为在艾滋病的流行中所起的作用比想象的还严重。这也是引起非洲艾滋病流行的一大主因。原因在于，非洲地区对同性恋者有偏见，这导致同性恋群体不得不掩盖其真实性取向，从而引发更危险性的后果。
例如，布隆迪许多男人因为害怕受歧视而隐藏自己的性取向。因此，他们要和异性结婚并生育孩子，但在维持婚姻关系的同时仍然和其他男性发生关系。这些人大多数知道和女性发生不安全的性关系可能染上艾滋病，但绝大部分人不知道其实和男人发生不安全的性行为更容易患艾滋病。
牛津大学的研究人员史密斯（Adrian Smith）认为，艾滋病在撒哈拉以南的非洲大面积蔓延是因为“该地区的文化、宗教和政治因素不愿意将男同性恋者纳入平等的社会成员而导致的”。例如，由于当地对同性恋根深蒂固的歧视，让男-男同性恋者不敢使用安全套，以免留下蛛丝马迹被发现。这种无保护的男-男同性性行为等于为HIV的传播大开绿灯，甚至火上浇油。
亚洲和中国的情况
2006年8月美国艾滋病研究基金会和亚洲抗击艾滋病组织Treat Asia在一份联合报告中指出，由于男性之间的同性性行为，亚洲的艾滋病疫情正“螺旋上升至失控”。2009年2月17日，世界卫生组织和联合国艾滋病规划署在香港召开的一次艾滋病会议上也指出了同性性行为可能导致艾滋病失控的危险。
原因在于，在亚洲许多国家同性性行为是一种禁忌，亚洲很多地区男性同性性行为处于隐秘状态，这不仅加重了HIV在男-男同性恋人群中感染的速度和程度，而且无法通过教育和干预机构与他们正常联系和交流，因此扩大了艾滋病的社会风险。
例如，许多MSM成员同时结婚，并且与女性发生性行为，从而把HIV传给其他人群。在尼泊尔65%有同性性行为的男子经常和女性发生性关系，45%的男性性工作者既和女性也和男性发生性关系，越南胡志明市这一比例为22%。
在柬埔寨首都金边，MSM人群中的HIV感染率估计为14%；在印度南部的安得拉邦，这一数字为16%；在泰国曼谷则高达28%。而且，一些地区多达一半的男子在发生同性性行为时从不使用安全套。
另外，在亚洲还有一个很大的忧虑，即庞大的男-男同性恋群体。2009年2月世界卫生组织的统计表明，亚洲估计有1000万MSM成员，如果不尽快防范，艾滋病在亚洲将会急剧恶化。
中国的同性恋和艾滋病情况也不容乐观。1989年底，中国发现的本土第一例因性接触感染艾滋病病毒的人，就是与多个男子有性关系的男子。调查发现，中国艾滋病的感染模式正在发生变化。过去的传播形式主要是输血、吸毒（共用针头）、异性性行为、同性性行为和母婴传播。但是，现在同性性行为传播艾滋病的比率正在上升。
2009年11月24日中国卫生部部长陈竺表示，性传播已经成为我国艾滋病传播的主要途径，其中，同性性行为所引起的艾滋病传播已经占到传播总数的32%，异性性行为导致的艾滋病传播达到40%。卫生部疾病预防控制局副局长郝阳也透露，2008年专业人员对中国61个城市的同性恋群体进行了调查，发现平均有4.8%的同性恋者患有艾滋病，其中最高的一个城市高达18%。由于中国的同性恋者大多处于地下状态，这个数据可能还比较保守。另外，中国有500万男同性恋者，中国男-男性行为者感染HIV的几率较一般人高出45倍之多。
在中国也有地下男性性工作者，他们有相当一部分人并不使用安全套。而且，其他男-男同性恋者使用安全套的也不多。据长春一家艾滋病预防和同性恋人群健康干预组织的调查，2007年仅有20%的男-男同性恋者采取安全措施，但是，到了2009年这个数字已经提升到70%。
当然，这只是一个城市的情况，中国其他城市如何，尚不知晓。由于男-男同性恋者是一个不小的群体，再加上行为方式、文化和生物、生理的原因，艾滋病在男-男同性恋者中的传播在中国和世界都有可能急剧发展。采取科学和有效的应对措施是整个社会的责任。
(本文来源： 南方周末 作者：张田勘)
AIDS blind: reveal men - gay mechanism of spread of HIV
2010-02-27 10:39:05 Source: Southern Weekend (Guangzhou)
Homosexuality does not mean AIDS, however, homosexuality and AIDS are closely related. This is closely related to expression of homosexual AIDS population has been a weak zone, the equivalent of the blind spots in this area.
The gay rights movement in 2009, "Pride Week" in a male homosexual
2008 march on the gay rights movement comrades in a pair of kissing couples Map / Flikr
Southern Weekend February 27 reported that homosexuality does not mean AIDS, however, homosexuality and AIDS are closely related. This is closely related to expression of homosexual AIDS population has been a weak zone, the equivalent of the blind spots in this area.
AIDS first was June 5, 1981 in Los Angeles, five men - gay men found. Subsequently, he also found that men - the AIDS epidemic among gay men is higher than the chance of several other modes of transmission of AIDS, that is, heterosexual sex, blood-borne, and mother to child transmission and so on. Meanwhile, the men - gay men the chance of spread of AIDS is far greater than women - lesbianism. The reason is, there are two broad categories. First, bio-medical reasons, and second, the reasons for behavior. Now, AIDS is becoming brighter up this blind spot.
AIDS is a human immunodeficiency virus (HIV) caused by, but are easy to HIV in the male - male homosexual transmission do? Now the University of California San Diego Center for AIDS Research (CFAR), associate professor of infectious diseases, viral pathogenesis research director David Smith (Davey M. Smith), who the latest research has revealed some of the mystery, for example, HIV in the seminal plasma in order to RNA (ribonucleic acid) in the form of sexual relations between men - between gay men spread.
Smith, who collected six pairs of men - gay men's blood and semen samples studied was found between the spread of HIV in the gay way.
RNA virus-like particle is a prime culprit
Is now known, the world's most HIV infections are due to exposure to semen of HIV-caused. Semen from the sperm, proteins, such as immune cells and seminal plasma composition. If a man has been infected with HIV or AIDS, their semen in the sperm, seminal plasma and immune cells may have HIV.
However, the seminal plasma of HIV is based on the form of RNA virus-like particles, but the sperm and immune cells in HIV Zeyi the form of DNA that proviral DNA. With the phylogenetic analysis, the method of comparing the genetic characteristics of HIV is to know how to sexual relations between men spread. Because the phylogenetic model can allow researchers to assess different group of viruses is the origin of the time. Thus, by analyzing the blood and semen from a homosexual partner HIV-extracted gene sequences can confirm the source of the rapid mutation of HIV.
Smith's research team found that HIV-infected homosexuals share a recent common ancestor of the virus, it comes from endogenous partner (first infected with HIV by them to transmit the virus to other sexual partners of male homosexuals) in Precision pulp, rather than a partner sperm cells derived proviral DNA.
The significance of this discovery is very important. Because, after people are not aware of HIV infections occur through sexual intercourse through the transmission of HIV-RNA virus-like particles or through the integrated proviral DNA of HIV infection. However, by these two forms of HIV viruses (RNA and DNA) the genetic differences between same-sex sexual relations and adoption of the newly HIV-infected homosexuals who extracted the genetic differences in HIV compared, the researchers finally confirmed that it is in seminal plasma The HIV-RNA virus-like particles result in male sexual partners of infection.
Smith believes that this discovery helps to prevent the spread of HIV. Because, if you know the source of the virus, researchers could develop new vaccines, vaginal microbial biocides and drugs to combat HIV transmission through sexual route.
Of course, since this study includes only a few pairs of men - gay men, it may not explain all the ways of sexually transmitted infections, particularly in heterosexual transmission of HIV, for example, male to female transmission. However, because most of the sexually infected with HIV, women are exposed to the semen of men infected, so the seminal plasma of HIV-RNA virus-like particles may be spread of disease murderers. However, Smith believes that this needs further studies to confirm.
This study also proved that, of course, men in the seminal plasma HIV-RNA viral particles most dangerous. It may also be why the men - gay men more vulnerable to HIV infection.
New York International AIDS Vaccine Center is dedicated to AIDS vaccine research and development.
Other factors do evil
At present, public health experts tend to use "have sex with men took place" to refer to these gay people, referred to as MSM. The MSM populations in other biological and physiological characteristics of the spread of HIV has also created a favorable opportunity.
MSM population is one of the major sex anal sex. Compared with heterosexual sex, rectal elasticity is less than the vagina, and rectum is relatively weak, rectal mucosa is thinner, more prone to breakage. Damage in the rectum, the semen contains a large number of HIV where it is easy to enter the body, infected T cells. Now, Smith's research team found in the seminal plasma RNA virus-like particles to infect, and therefore, RNA virus-like particles with the fragile and damaged rectum combination has become the MSM population most vulnerable to HIV, one of the reasons.
On the other hand, seminal plasma in the RNA virus-like particles to become infected with the murderers can also explain a situation in which the MSM population infected with HIV through sexual intercourse were more likely to. World Health Organization in 2008 the new statistics show that about 70% -80% the world's HIV-infected through sexual activity occurred. After unprotected intercourse occurs once, in the MSM population infected with HIV, about 0.5% -3% chance; but in heterosexual sex, the men and woman risk of transmission is about 0.1% -0.2%, male-female odds are roughly 0.03% -0.1%. As a means of conversion, MSM crowd unprotected intercourse once risk of HIV infection is the same woman under the conditions of men and 5-15 times the mass, women of 16-30 times that of male.
In addition, the semen of some special material for the spread of HIV have played a role in siding with the bully. For example, the German researchers found that human semen in the prostate acid phosphatase (PAP) can greatly improve the capacity of HIV infection. The researchers collected semen from a number of peptides and small protein molecules, and observed in cell culture in their role in HIV susceptibility. The results show that, PAP polypeptide can be a powerful catalyst for the spread of HIV. Moreover, when these set of synthetic PAP fragments of amyloid fibrils, they are the strongest activity.
Therefore, these amyloid fibrils is known as HIV infected semen-derived enhancing factor (SEVI), their role is that by capturing HIV virus-like particles to promote HIV infection, and to promote its cooperation with T-cell fusion, thus HIV virus increased susceptibility to several orders of magnitude, and sometimes even increase by 10 million times. The researchers also tested HIV-susceptible mouse model of the role of these fibers found at the same time injected with the HIV virus in mice fibers and blood levels of HIV proviral DNA is simply injected five times more HIV in mice.
Although no studies have shown that semen in the PAP in the MSM population more powerful in heterosexual on the wane, but a combination of factors, male - male behavior is the most dangerous route of transmission of HIV.
Social and cultural reasons
There is no doubt, MSM groups most likely to lead to the spread of AIDS lies in the social and cultural reasons. Whether it is more open about homosexuality in the West or in the more conservative East and Africa, homosexuality is not seen as a social capacity. This has resulted in homosexual underground status, there are several features of their sexual behavior. First, multiple sexual partners; second is arbitrary large, in bars, parks, toilets, and even the streets and other one-time sex; third, do not use condoms.
These features more likely to cause HIV transmission among people in the MSM. At the same time, society has no place for homosexuality also caused another hidden evil. Attempts to conceal his homosexuality, and many had to contend with the opposite sex gay marriage, a family in the form of used to conceal, but do not give same-sex sexual behavior. In unsafe sex with multiple sex are after, they may go home with his wife having sex, which might bring HIV transmission to family members and other ordinary people. This is a bigger blind spot of AIDS, it is a social blind spots and larger hidden tragedy.
July 20, 2009 issue of the British medical journal "Lancet" published a study shows that male homosexuals in some parts of Africa, HIV infection rates in other regions of the male 10 times. Sub-Saharan Africa, male - male homosexual unprotected sex in the AIDS epidemic in the role but also a serious than imagined. This is also caused by the AIDS epidemic in Africa a major culprit. The reason is that the African region are biased against homosexuals, which leads to gay groups, had to cover up the truth of orientation, giving rise to more dangerous consequences.
For example, many men in Burundi because of fear of discrimination and to hide their sexual orientation. Therefore, they should be, and the opposite sex to marry and have children, but in maintaining the marital relationship and other men while still a relationship. Most of these people know and unsafe sexual relations of women may be infected with AIDS, but most people do not know if in fact men who have unsafe sex is more susceptible to AIDS.
Researchers at the University of Oxford Smith (Adrian Smith) believed that AIDS in sub-Saharan Africa the spread of a large area because "the region's cultural, religious and political factors that are unwilling to gay men into equal members of society caused." For example, the local deep-rooted discrimination against homosexuals, so that men - gay men reluctant to use condoms to avoid leaving clues have been discovered. Such unprotected male - male homosexual sex is equal to the spread of HIV, the green light, and even fuel.
Asia and the situation in China
In August 2006 the United States and the Asia Foundation for AIDS Research to Fight AIDS organizations Treat Asia in a joint report that because homosexual acts between men, Asia's AIDS epidemic are "spiraling out of control." February 17, 2009, WHO and UNAIDS held in Hong Kong AIDS Conference also noted that a same-sex sexual behavior may lead to AIDS, the risk of loss of control.
The reason is that many countries in Asia, homosexual sex is a taboo in many parts of Asia have sex with men in a hidden state, which not only increased the HIV in men - gay men in the speed and extent of infection, and can not be through education and intervention institutions and their regular contacts and exchanges, it expanded the social risks of AIDS.
For example, many members of the MSM the same time, married, and having sex with women, thus bringing the HIV transmission to other people. In Nepal, 65% had sex with men and women often have sexual relations, 45% of men and women have both sex workers and men who have sexual relations, Vietnam, Ho Chi Minh City compared to 22%.
In the Cambodian capital Phnom Penh, MSM populations in the HIV prevalence is estimated at 14%; in the southern Indian state of Andhra Pradesh, the figure was 16%; in Bangkok, Thailand is as high as 28%. In addition, as many as half in some areas in the event of homosexual men never use condoms when having sex.
In addition, in Asia, there is a big fear that the huge male - gay group. In February 2009 the World Health Organization statistics show that an estimated 10 million MSM in Asia members, if not as quickly as possible to prevent the AIDS epidemic in Asia will be deteriorating rapidly.
China's homosexuality and AIDS situation is not optimistic. By the end of 1989, China's first case found in the local HIV infection through sexual contacts of people, that is, with a number of men who have sex with men. The survey found that China's HIV infection patterns are changing. The spread is mainly made in the past, blood transfusion, drug use (sharing needles), heterosexual sex, homosexual sex and mother to child transmission. But now the ratio of same-sex sexual spread of AIDS is on the rise.
November 24, 2009, Chinese Health Minister Chen Zhu said that sexual transmission has become a major means of HIV transmission in China, where same-sex sexual behavior caused by the spread of AIDS has accounted for 32% of the total transmission, the spread of AIDS resulting from heterosexual sex 40%. Ministry of Health, Bureau of Disease Control and Prevention Hao Yang, deputy director also revealed that in 2008 professionals in 61 cities in China conducted a survey of gay groups, and found an average of 4.8 percent of homosexuals with AIDS, the highest being a city of up to 18% . As China's gays are mostly underground state, the data may also be more conservative. In addition, China has five million male homosexuals, the Chinese men - men, actors infected with HIV-risk 45 times higher than the average person as much.
In China there are underground male sex workers, they have a considerable number of people do not use condoms. Moreover, other men - gay men do not have much use of condoms. According to Changchun, an AIDS prevention and gay organizations, population health intervention survey, 2007 was only 20% of the men - gay men to take security measures, but by 2009 this figure had been raised to 70%.
Of course, this is just a situation in cities, how other cities in China, is not known. As the men - gay men is not a small group, combined with patterns of behavior, cultural and biological, physiological causes of AIDS in men - gay men in the spread of both China and the world may be undergoing rapid development. Adopt a scientific and effective response is the responsibility of society as a whole.
(This article Source: Southern Weekly Author: ZHANG Tian-Kan)
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