Lodes M J, Connors V A, Yoshino T P
Department of Pathobiological Sciences, University of Wisconsin-Madison 53706.
Mol Biochem Parasitol. 1991 Nov;49(1):1-10. doi: 10.1016/0166-6851(91)90124-o.
Infection with larval trematodes has been shown to inhibit several snail-host defences, including hemocyte phagocytosis, cytotoxicity, motility, and adherence. Certain plasma factors which mediate snail defence responses, and which may be produced by host hemocytes, also appear to be altered by these parasites. In this study we present protocols for the isolation of 2 proteins from larval Schistosoma mansoni excretory-secretory (ES) products and detail the effects of these components on Biomphalaria glabrata hemocyte protein synthetic/secretory (S/S) activity. Schistosome ES proteins, separated with a combination of membrane ultrafiltration, size exclusion, and ion exchange chromatography, were tested for their in vitro effect on cultured snail hemocytes, in the presence and absence of homologous plasma. A high-molecular-weight ultrafiltration fraction of parasite ES products (H30), in combination with plasma, was found to differentially affect susceptible (M-line) and resistant (10-R2) snail hemocytes. Secretion of metabolically labeled polypeptides by M-line cells was inhibited significantly while the S/S response of 10-R2 hemocyte polypeptides was not affected. In the absence of homologous plasma, little or no differential affect of ES polypeptides on hemocyte S/S activity was seen. Much of the inhibitory activity of H30 was attributable to a partially purified fraction, Peak I (PkI), of ES products. Evidence suggests that, in its native state, PkI is a high-molecular-weight protein aggregate comprising subunits of approximately 22-24 kDa. Thus, PkI, in the presence of homologous plasma components, is a potential mediator of schistosome-induced suppression of polypeptide synthesis or secretion in hemocytes of susceptible snails. In combination with other parasite and host factors, PkI may be involved in the host-parasite interaction which leads to the state of susceptibility or resistance found in our strains of B. glabrata.
已证明幼虫期吸虫感染会抑制几种蜗牛宿主防御机制，包括血细胞吞噬作用、细胞毒性、运动性和黏附性。某些介导蜗牛防御反应且可能由宿主血细胞产生的血浆因子，似乎也会被这些寄生虫改变。在本研究中，我们介绍了从曼氏血吸虫幼虫排泄-分泌（ES）产物中分离两种蛋白质的方法，并详细说明了这些成分对光滑双脐螺血细胞蛋白质合成/分泌（S/S）活性的影响。通过膜超滤、尺寸排阻和离子交换色谱相结合的方法分离出的血吸虫ES蛋白，在有和没有同源血浆的情况下，测试了它们对培养的蜗牛血细胞的体外作用。发现寄生虫ES产物的高分子量超滤级分（H30）与血浆结合，对易感（M系）和抗性（10-R2）蜗牛血细胞有不同影响。M系细胞中代谢标记多肽的分泌受到显著抑制，而10-R2血细胞多肽的S/S反应不受影响。在没有同源血浆的情况下，ES多肽对血细胞S/S活性几乎没有差异影响。H30的大部分抑制活性归因于ES产物的部分纯化级分峰I（PkI）。有证据表明，在其天然状态下，PkI是一种高分子量蛋白质聚集体，由约22-24 kDa的亚基组成。因此，在同源血浆成分存在的情况下，PkI是血吸虫诱导易感蜗牛血细胞中多肽合成或分泌抑制的潜在介质。与其他寄生虫和宿主因子结合，PkI可能参与宿主-寄生虫相互作用，导致我们的光滑双脐螺菌株出现易感或抗性状态。
