?瘧疾產生的最嚴重傷害就是對孕婦和兒童的傷害。瑞典Karolinska學院和烏干達Makerere大學的聯(lián)合研究對于瘧原蟲本身是如何在胎盤中隱藏的現象有了一些重要的發(fā)現,。
??Plasmodium falciparium是目前傳染人類的最有毒力的4大瘧原蟲之一,。他的極其危險性在于他也感染孕婦的胎盤，對孕婦和胎兒有致命的影響,。因此,，遭受瘧疾國家的醫(yī)療資源常常也很薄弱，這樣就造成了孕婦在分娩過程中死亡的嚴重后果,。
??“由于某些原因,，通常在成人中發(fā)現，懷第一胎的婦女丟失半免疫性,，”一邊工作一邊學習的KI畢業(yè)生 Niloofar Rasti解釋說,，“胎盤似乎是諸蟲亞群體最有利的解剖學環(huán)境。”
??在Mats Wahlgren教授領導下的Karolinska學院的研究小組和Uganda大學KI同事一起詳細研究了寄生蟲是如何感染胎盤的,。他們的結果出版在美國科學雜志PNAS上,，促進了抗嚴重瘧疾感染的疫苗和治療的研究,。
??寄生蟲在其生命的特定階段進入人體紅細胞，在紅細胞里能夠產生自身黏附的蛋白血脈壁的受體結合,。這會引起紅細胞在機體毛細管處聚積,，產生危及生命的征兆。感染過幾次瘧原蟲成人的防御系統(tǒng)開始逐漸識別寄生蟲蛋白,，變得部分免疫,。然而，一旦胎盤形成,，不同的受體就會誘導形成新的環(huán)境,。這就意味著一個適合諸蟲亞群體生存的環(huán)境形成。
??早期研究表明,，寄生蟲來源的每個蛋白只識別某個特異的胎盤蛋白受體,。然而，Ms Rasti和他的同事懷疑天然機制比實驗室的研究更復雜,。因此,，他們在烏干達對胎盤進行收集分析研究。
??“我們研究的大多數諸蟲能結合胎盤上不同的受體,，”她說,，“這就意味著未來的疫苗不能只局限于以往研究的一個蛋白一個受體的原則。”
??既然科學家知道,，幾個胎盤受體結合的機制,，那么研究就應該轉移到寄生蟲本身上來，看是否產生不同的表面蛋白,，或者一個和一類蛋白是否能結合許多不同的宿主受體,。
英文原文：
New findings could lead to vaccine for severe malaria
The most severe form of malaria hits pregnant women and children the hardest. A joint study between Karolinska Institutet in Sweden and Makerere University in Uganda has now produced some important findings on how the malaria parasite conceals itself in the placenta.
Plasmodium falciparium is the name of by far the most virulent of the four malaria parasites that infect man. It is particularly dangerous in that it also infects the placenta of pregnant women, with fatal consequences for both her and the foetus. This, combined with the often feeble medical resources of malaria-stricken countries, can lead to such serous complications that the mother dies during delivery.
"For some reason, women in their first pregnancy lose the semi-immunity that is normally found in adults," explains Niloofar Rasti, a KI graduate student who has been working with the study. "The placenta seems to be an anatomically favourable environment for a subpopulation of the parasites."
The research group from Karolinska Institutet, under the leadership of Professor Mats Wahlgren, has been working with colleagues from KI's partner university in Uganda to study in detail how the parasite infects the placenta. Their results, which are published in the American scientific journal PNAS, can enable the development of vaccines and therapies to combat severe malarial infections.
During one particular phase of its lifecycle, the parasite enters human red blood cells, where it produces proteins that attach themselves to receptors in the wall of the blood vessels. This causes the red blood cells to accumulate in organ capillaries, and gives rise to life-threatening symptoms. Adults who have been infected several times can become partly immune as their defence system gradually starts to recognise the parasite's proteins. When the placenta is formed, however, a new environment is introduced with a different set of receptors. This means that a new growth niche is made available to a subpopulation of the parasites.
Earlier studies have suggested that each protein from the parasite attaches to only one specific protein, a receptor, in the placenta. Ms Rasti and her colleagues suspected, however, that the natural mechanisms are more complex than laboratory studies have shown. They therefore collected and analysed placentas on site in Uganda.
"Most of the parasites we studied could bind to three different receptors in the placenta," she says. "This would mean that a future vaccine cannot be based on the principle of one protein-one receptor, as was previously believed."
Now that scientists know that several placental receptors are involved in the binding mechanism, attention will be shifted to the parasite itself, and whether it produces many different surface proteins or if one and the same protein is able to bind to many host receptors.
