來自蒙大納州立大學(xué)（Montana State University）等處的研究人員發(fā)現(xiàn)了一種會威脅包括從嬰兒到艾滋病患者在內(nèi)的每一個人的常見寄生蟲,，受到了科學(xué)界的關(guān)注,，這些研究成果發(fā)表在《Nature》（12月20日在線版）,，《Science》（12月15日）和《PLoS Pathogens》（11月27日）,。
弓形蟲?。═oxoplasmosis）是一種由弓形蟲寄生引起的感染,，世界各地的弓形蟲感染非常普遍,。美,、英的成年人中,，大約16—40%發(fā)生過感染,，有的調(diào)查達(dá)70%，而歐洲大陸和拉丁美洲的成年人,，50—80%發(fā)生過感染,，法國人高達(dá)90%。1985—90年我國的23個省,、市,、自治區(qū)的調(diào)查，大都在10%以下,。
雖然這種寄生蟲引起的疾病可能很輕微,，但是有嚴(yán)重免疫缺陷的病人，如愛滋病人等,，如果發(fā)生感染,，后果就很嚴(yán)重。懷孕婦女感染可傳染給胎兒,，也有可能發(fā)生嚴(yán)重后果,。
近期研究發(fā)現(xiàn)寄生蟲和宿主之間的分子作用會直接調(diào)控疾病的嚴(yán)重程度，而且寄生蟲的基因也會導(dǎo)致宿主免疫系統(tǒng)紊亂,，引起長時間慢性疾病的發(fā)生,。
MSU的研究人員發(fā)現(xiàn)這些寄生蟲會在宿主中注入一種蛋白，極大的調(diào)節(jié)了宿主的免疫應(yīng)答,，MSU獸醫(yī)分子生物學(xué)教授Michael White就說,，“I類菌株對于人類系統(tǒng)而言十分重要，因?yàn)樗麄儾糠值膶?dǎo)致了AIDS病人腦部的感染,，以及一些從孕婦傳染到嬰兒十分嚴(yán)重的天生疾病,。”
這一研究成果為研究toxoplasmosis以及其它與瘧疾，Eimeria相關(guān)的疾病提供了一個研究模式,，也為治療這些疾病帶了希望,。
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.
