来自蒙大纳州立大学（Montana State University）等处的研究人员发现了一种会威胁包括从婴儿到艾滋病患者在内的每一个人的常见寄生虫，受到了科学界的关注，这些研究成果发表在《Nature》（12月20日在线版），《Science》（12月15日）和《PLoS Pathogens》（11月27日）。
弓形虫病（Toxoplasmosis）是一种由弓形虫寄生引起的感染，世界各地的弓形虫感染非常普遍。美、英的成年人中，大约16—40%发生过感染，有的调查达70%，而欧洲大陆和拉丁美洲的成年人，50—80%发生过感染，法国人高达90%。1985—90年我国的23个省、市、自治区的调查，大都在10%以下。
虽然这种寄生虫引起的疾病可能很轻微，但是有严重免疫缺陷的病人，如爱滋病人等，如果发生感染，后果就很严重。怀孕妇女感染可传染给胎儿，也有可能发生严重后果。
近期研究发现寄生虫和宿主之间的分子作用会直接调控疾病的严重程度，而且寄生虫的基因也会导致宿主免疫系统紊乱，引起长时间慢性疾病的发生。
MSU的研究人员发现这些寄生虫会在宿主中注入一种蛋白，极大的调节了宿主的免疫应答，MSU兽医分子生物学教授Michael White就说，“I类菌株对于人类系统而言十分重要，因为他们部分的导致了AIDS病人脑部的感染，以及一些从孕妇传染到婴儿十分严重的天生疾病。”
这一研究成果为研究toxoplasmosis以及其它与疟疾，Eimeria相关的疾病提供了一个研究模式，也为治疗这些疾病带了希望。
英文原文：
Montana Parasite Researchers Score A Prestigious Triple
Montana State University researchers and their collaborators are gaining widespread attention for discoveries involving a common parasite that can threaten everyone from babies to AIDS patients.
Their findings about "Toxoplasma gondii" and toxoplasmosis were published recently in three major scientific journals. "Nature" published a paper Wednesday, Dec. 20, in its advanced online version. "Science" published a paper on Dec. 15 and "PLoS Pathogens" on Oct. 27.
"It's not often you get such a cluster of papers coming out," said Michael White, one of the authors and an MSU professor of veterinary molecular biology. He added that MSU researchers will have another opportunity to explain the studies when they host an international conference on toxoplasmosis from June 29-July 2, 2007 at Chico Hot Springs.
Toxoplasmosis is normally associated with medical advice that pregnant women avoid changing cat litter, but it's gaining new attention because of the AIDS epidemic and bioterrorism, the researchers said. Severe toxoplasmosis can cause AIDS patients to go into a deep dementia and become unconscious of their surroundings.
"It's one of the worst syndromes an AIDS patient can die from," said Jay Radke, another of the MSU authors.
Toxoplasmosis is a disease caused by the parasite "Toxoplasma gondii." Symptoms usually appear only in people with weakened immune systems, but on rare occasions, healthy people suffer serious eye and central nervous system problems from toxoplasmosis. Their babies can have birth defects. White said toxoplasmosis also may be linked to some cases of schizophrenia and bipolar disease. It can kill livestock and has devastated efforts to restore sea otters near Monterey, Calif. Because it's common, yet complex, toxoplasmosis is a potential weapon for bioterrorists.
People usually acquire toxoplasmosis by eating commercial meat or drinking water that's contaminated with "Toxoplasma gondii," White said. They can also pick it up by handling soil or anything that has come in contact with cat feces. "It's a complex cell just likes ours in terms of metabolism and biochemistry, which makes it a tough nut to crack," he added.
The recently-published studies show that molecular interactions between the parasite and host directly regulate the disease's severity, White said. Genes from the parasite also disrupt signals in the host's immune system and control the establishment of life-long chronic disease.
Genetic crosses produced at MSU were critical in the study that discovered that the parasite dumps a protein into the host to dramatically regulate its immune response, White said. Labs in MSU's Department of Veterinary Molecular Biology and MSU's microarray facility helped establish the role of a second pathogen protein that makes one strain of "Toxoplasma" especially dangerous. "Type I strains are extremely important to human medicine as they are disproportionately responsible for inflammation of the brain in AIDS patients and for severe congenital disease that is passed from mother to baby," White said.
MSU led the study that was published in "PloS", White said. MSU made major contributions to the "Nature" and "Science" papers which were collaborations with Stanford University and Washington University in St. Louis. The studies give other scientists a model for studying toxoplasmosis or related diseases like malaria and Eimeria, which causes coccidiosis, White added. Eimeria parasites kill chickens and other commercially-raised animals like cattle.
A press release from Washington University said researchers in the future will try to develop more effective treatments against toxoplasmosis by blocking ROP18, the gene largely responsible for making toxoplasmosis so dangerous to humans. The "Toxoplasma gondii" parasite has approximately 6,000 genes in all. Scientists will also look for other genes that work together with ROP18.
