【作者】 田利光；

【导师】 周晓农；

【作者基本信息】 中国疾病预防控制中心 ， 流行病与卫生统计学， 2010， 博士

【摘要】 我国是寄生虫病流行较严重的国家,某些经济欠发达的农村地区寄生虫病的发病率仍然维持在较高水平,同时由于非法采供血等原因,我国中部的农村地区也是HIV流行严重的地区,因此HIV和寄生虫合并感染的情况可能大量存在。有关研究显示,寄生虫感染后常引起的机体免疫应答由Th1型向Th2型转化,有利于HIV病毒DNA的复制并促进病程的进展,导致HIV进展为AIDS的病程加速；另外,HIV感染也会恶化寄生虫感染的自然病情,造成某些寄生虫病临床症状加重以及治疗困难。HIV感染者合并寄生虫感染,尤其是肠道寄生虫混合感染造成的HIV感染者体内病毒复制增加以及慢性腹泻、消瘦、营养不良等是造成HIV感染者病情进展加速甚至死亡的重要原因之一。因此,研究艾滋病的防治同时,肠道寄生虫引起的混合性感染是一个不容忽视的问题。如何预防和控制HIV与寄生虫合并感染已经成为国内外研究的热点,但是我国相关研究报道较少。本研究通过开展相关调查研究来了解我国HIV/AIDS高流行地区肠道寄生虫病的流行情况及HIV阳性人群合并寄生虫感染现状,探索合并感染对免疫功能的影响以及常见合并感染寄生虫的种类和可能的影响因素,为预防和控制合并感染的发生,减少合并感染对HIV/AIDS感染者的危害提供参考数据。本次研究首先开展了针对全部人群的现况调查,共调查了1291人,其中参与粪检720人,参与血检568人,接受问卷调查607人。检测了9种常见肠道寄生虫,其感染率分别为蛔虫0.56%、钩虫4.03%、鞭虫0.28%、华支睾吸虫0.42%、人芽囊原虫21.39%、贾第虫3.89%、阿米巴1.67%、隐孢子虫4.44%、粪类圆线虫0%。肠道蠕虫的感染率为4.72%，肠道原虫的感染率为24.31%。贾第虫和隐孢子虫感染与年龄存在相关关系(P<0.05),贾第虫感染率最高的是小于6岁年龄组,感染率为7.84%；隐孢子虫感染率最高的是60岁以上年龄组,感染率为6.76%。贫血的患病率为34.7%,HIV感染率为8.1%,HIV合并肠道寄生虫的感染率为2.3%。在调查的46名HIV阳性感染者中,合并人芽囊原虫感染率为19.6%,合并隐孢子虫感染率为13.0%,HIV阳性感染者合并隐孢子虫的感染率显著高于HIV阴性人群(P<0.001)。结果显示,当地肠道寄生虫感染率高。其中蠕虫感染率较低,以钩虫感染为主；原虫感染率较高,以人芽囊原虫、隐孢子虫和贾第虫为主。HIV阳性人群中,合并蠕虫感染率低,合并原虫感染率高,合并隐孢子虫感染率显著高于普通人群,提示在HIV/AIDS人群中开展合并肠道寄生虫的研究,尤其是合并肠道原虫感染的研究应该引起广大科研和医务工作者的关注。在对一般人群调查的基础上,又开展了针对HIV阳性人群和HIV阴性人群寄生虫感染情况研究,共调查了HIV阳性309人,HIV阴性315人,结果显示,当地HIV感染者合并肠道蠕虫感染率为4.3%(13/302),感染率最高的为钩虫3.64%(11/302),HIV阳性人群和HIV阴性人群在肠道蠕虫感染方面差别无统计学意义。HIV感染者合并肠道原虫的感染率为23.2%(70/302),感染率最高的为人芽囊原虫16.23%(49/302),其次为隐孢子虫8.28%(25/302)。在HIV阳性人群中女性人芽囊原虫感染率(20.13%)显著高于男性(11.89%),而隐孢子虫感染率(4.40%)则显著低于男性(12.59%)。人芽囊原虫感染率在HIV阳性人群和HIV阴性人群之间差别无统计学意义,而HIV阳性人群隐孢子虫感染率(8.28%)显著高于HIV阴性人群(2.97%),两者差别有统计学意义(P<0.001)。提示HIV感染者合并隐孢子虫感染的机会增加,应加强HIV感染人群合并隐孢子虫感染的监测和研究。对HIV与隐孢子虫合并感染影响因素的多因素Logistic回归分析结果显示,最终进入模型的变量为男性(OR=6.700,95%CI：2.030,22.114)、年龄42岁以下(OR=4.148,95%CI：1.348,12.761)、体内IL-2水平<77pg/ml(OR=0.226,95%CI：0.076,0.674)和个人卫生习惯好(OR=0.324,95%CI：0.105,0.994)。即男性、年龄在42岁以下、体内IL-2水平大于77pg/ml以及个人卫生习惯不好的HIV感染者更易合并隐孢子虫感染。提示我们在预防和控制HIV合并隐孢子虫感染时应当将上述人群作为重点防治对象。本研究对HIV阳性人群和HIV阴性对照人群进行了免疫因子检测,结果显示HIV合并蠕虫感染者体内IL-10和IFN-r水平下降,IL-4上升,Th2型细胞免疫效应增强,抑制Th1型细胞免疫效应,T值(T=Th1/(Th1+Th2))下降,不利于机体的抗HIV病毒免疫反应。HIV与蠕虫合并感染的联合作用可使机体Th1/Th2免疫失衡呈增强效应,合并蠕虫感染可加速使体内CD4+T淋巴细胞水平下降。HIV合并人芽囊感染后体内IL-2水平上升,其他各免疫因子变化不明显。HIV合并隐孢子虫感染后体内CD4+T淋巴细胞和CD4/CD8比值明显下降。提示HIV阳性人群合并肠道蠕虫或隐孢子虫感染可加破坏机体的免疫平衡,影响机体的免疫功能,对机体的抗HIV病毒免疫反应不利,有加速HIV感染进展为AIDS的可能。本研究结果显示,HIV阳性人群合并隐孢子虫感染几率最高。隐孢子虫体积微小,普通病原学诊断方法误诊、漏诊率较高。本研究探索使用巢式PCR技术来检测粪便中隐孢子虫卵囊,并利用基因测序以及构建系统发育树等方法来确定隐孢子虫的基因型。通过巢式PCR检测、基因测序和系统发育树分析,证实本次检测到的隐孢子虫为火鸡隐孢子虫(Cryptosporidium meleagridis)和贝氏隐孢子虫(C.baileyi)。本次研究采用Whatman公司生产的FTA Card来抽提粪便中隐孢子虫DNA的技术,其操作简单,敏感度高,证明是一个较好的抽提粪便中隐孢子虫卵囊的方法,值得推广。本研究开展了对隐孢子虫水源性传播途径的探索性调查,使用Filta-Max xpress快速法对当地地表水和日常生活饮用水进行检测,发现当地生活饮用水隐孢子虫卵囊的阳性率为30.43%,地表水的阳性率为55.56%。池塘水中隐孢子虫卵囊检出率高于河水,桶装水隐孢子虫卵囊检出率高于井水,直接饮用受到隐孢子虫卵囊污染的桶装水可能是当地隐孢子虫感染的主要途径之一。综合上述研究结果,当地蠕虫感染率较低,以钩虫感染为主；原虫感染率较高,以人芽囊原虫、隐孢子虫和贾第虫感染为主。HIV阳性人群合并肠道寄生虫感染率高,其中合并蠕虫感染率低,合并原虫感染率高。HIV阳性人群合并隐孢子虫感染的几率高。HIV与蠕虫合并感染可引起HIV阳性人群体内Th2型细胞反应增强,抑制了Th1型细胞反应,有利于HIV病毒在体内的复制,可加速HIV感染者进展为AIDS。合并人芽囊原虫感染对机体免疫功能无显著影响。HIV与隐孢子虫合并感染的联合作用造成CD4+T淋巴细胞数量下降呈相加效应。HIV阳性人群合并感染的隐孢子虫有火鸡隐孢子虫(C.meleagridis)和贝氏隐孢子虫(C.baileyi)两种。当地地表水和浅井水隐孢子虫卵囊阳性检出率高,饮用受到隐孢子虫卵囊污染的桶装水或浅井水是当地感染隐孢子虫的主要途径之一。更多还原

【Abstract】 Co-infecton of HIV and intestinal parasites in highly endemic areas of HIV/AIDS in ChinaParasitic disease is still a public health problem in China, notably in certain underdeveloped rural areas in central China where the incidence of parasitic disease remains high. Illegal blood collection and supply and other factors have triggered a HIV epidemic in some of these areas, and thus considerable HIV and parasite co-infections may exist. Parasitic infections often elicit an immune response shift from a T helper 1 (Th1) type to a Th2 type. This change is conducive to HIV viral DNA replication and promotes the progression of HIV towards AIDS. HIV infections also exacerbate the clinical symptoms of parasite infections and complicate treatment. Therefore, the prevention and control of HIV and parasite co-infections have become a focus of international parasitological research. However, there is a lack of relevant research information in China, so that our cross-sectional surveys and studies have mainly focused on the following questions:(ⅰ) to investigate the prevalence of intestinal parasite infections in highly endemic areas of HIV/AIDS; (ⅱ) to understand the local rate of parasite and HIV co-infection; (ⅲ) to study the effects of parasite and HIV co-infection on immune functions and possible risk factors contributed to the co-infection. The objectives of the present study were two folds, first, to provide data on the control and prevention of parasite and HIV co-infections, and second, to decrease the adverse effects of parasitic infections on people living with HIV.First, a cross-sectional survey was carried out among the common population in rural areas of Fuyang in Anhui province, focusing on the incidence of intestinal parasite infections. A total of 1,291 individuals were recruited, and eight species of intestinal parasites were detected. Their respective prevalences were 0.56% for Ascaris lumbricoides,4.03% for hookworm,0.28% for Trichuris trichiura,0.42% for Clonorchis sinensis,21.39% for Blastocystis hominis,3.89% for Giardia intestinalis, 1.67% for Entamoeba spp. and 4.44% for Cryptosporidium spp. Strongyloides stercoralis was not found. The intestinal helminth infection rate was 4.72%(34/720) in total population, the intestinal protozoa infection rate was 24.31%(175/720), and the prevalence of anemia was 34.7%. The co-infection rate of HIV and intestinal protozoa was 28.3%(13/46), with B. hominis and Cryptosporidium spp. co-infection rates of 19.6%(9/46) and 13.0%(6/46), respectively. The prevalence of Cryptosporidium spp. among HIV positives was significantly higher than among HIV negatives (P<0.001). Results showed that local intestinal helminth infection rates were low but elevated prevalences of intestinal protozoa can be found. HIV co-infections with intestinal helminths are rare but co-infections with protozoan were common. HIV positives had a disproportionately high prevalence of Cryptosporidium spp. Further studies on HIV co-infections with intestinal parasites, especially with intestinal protozoa, should be the focus for future studies.Second, an investigation of co-infections of HIV and parasites among HIV positive people and a HIV negative control group was conducted. A total of 624 people were recruited, including 309 people with HIV and 315 HIV negative controls. There were 302 people with HIV and 302 HIV negative controls that were eligible. Results showed that intestinal helminth co-infection rate was 4.3% (13/302) among people with HIV positive, with hookworm being the most common species (3.64%; 11/302). The prevalence among HIV negative individuals was not significantly different from that among HIV positives. The co-infection rate with intestinal protozoa was 23.2%(70/302) among those with HIV; B. hominis was the most common species (16.23%; 49/302), followed by Cryptosporidium spp. (8.28%; 25/302). No significant difference was found between the prevalences of B. hominis among the HIV negative and the HIV positive group. However, significant difference was found in Cryptosporidium spp. co-infected with HIV (8.28%) than the negative control group (2.97%). A multivariate logistic regression analysis showed that the factors significantly associated with parasite co-infections included sex (men: OR=6.700,95% CI:2.030,22.114), age (less than 42 years old:OR=4.148,95% CI: 1.348,12.761), and poor personal hygiene habits (OR=0.324,95% CI:0.105,0.994). These results confirmed that HIV positive people were more susceptibility to Cryptosporidium spp. than HIV negative ones, and that surveillance and research on Cryptosporidium spp. co-infections among HIV positive individuals should be strengthened.Results from cytokine test showed that intestinal helminth co-infections among HIV positives decreased the level of interferon gamma (IFN-y) and interleukin 10 (IL-10), and increased the level of interleukin 4 (IL-4). Th2-type immune response was increased and T values (T=Th1/(Th1+Th2) decreased among intestinal helminth co-infection people. The CD4 count was not significantly different between those with and without intestinal helminth co-infections. The interleukin 2 (IL-2) level increased notably in people co-infected with B. hominis but the levels of other cytokines did not change significantly. CD4 counts and the CD4/CD8 ratio were significantly lower in the group with Cryptosporidium spp. co-infection in comparison with the non-infected. Results suggested that a co-infection with Cryptosporidium spp. may aggravate the stress on the immune system of HIV positive people, and accelerate the progression of the infection to AIDS.Results of the cross-sectional survey show that Cryptosporidium spp. is an important parasite among people with HIV. However, employing the common diagnostic methods resulted in a considerable number of mis-or undiagnosed infections. In the present study, the use of a nested PCR essay was explored for the detection of Cryptosporidium spp. oocysts in feces. Gene sequencing was employed to determine the genotype. The results suggest that Whatman’s FTA Card is a better method to extract Cryptosporidium spp. DNA from stool samples compared to the QIAamp DNA Stool Mini Kit. It is simple to operate and highly sensitive compared to the QIAamp DNA Stool Mini Kit. The Cryptosporidium spp. detected among HIV positive individuals were C. meleagridis and C. baileyi.A survey of the water-borne transmission cycle of Cryptosporidium spp. was also carried out, using the Filta-Max xpress rapid method to detect the parasite in surface and drinking water. Cryptosporidium spp. oocysts were found in 30.43% of all drinking water samples and in 55.56% of the surface water samples. Cryptosporidium spp. oocysts were found more often in ponds than in rivers, and more frequently in bottled water as compared to well water.We conclude that the local prevalence of intestinal helminths is low, with hookworm being the main species. Infections with protozoa were more common, and B. hominis and Cryptosporidium spp. are the most common parasites. The prevalence of Cryptosporidium spp was significantly higher among HIV positive individuals in comparison with their HIV negative peers. Helminth infections can lead to an immune response shift from the Thl type to the Th2-type and further the progression of HIV towards AIDS. B. hominis infections have no significant effect on immune function but the impact of Cryptosporidium spp. infections on the immune system remains to be further studied. Contaminated bottled water and shallow well water are the main source of infection for Cryptosporidium spp.更多还原