Ultrastructural alterations in adult Schistosoma mansoni, harbored in non-antihelminthic treated and low-inflammatory mice by transmission electron microscopy (TEM)

This original study suggests that alterations observed on tegumental structure and egg quality of adult Schistosoma mansoni harvested from TS mice are due to their high immune tolerogenic and low-inflammatory capacity. The tegument of worms harvested from genetically selected mice for extreme phenotypes of immune oral tolerance, resistance (TR) and susceptibility (TS) were analyzed by transmission electron microscopy (TEM). Parasites recovered from TR mice showed no tegumental morphological changes. However, specimens collected from TS mice exhibited tubercle swelling with blunted and shortened spines in lower density. These tegumental alterations were similar to those described with artemether or praziquantel treatment, but without to affecting the worm surveillance, supporting observations that the host immune system influences the development and function of the tegument of worms harbored in non-antihelminthic treated TS mice. TS mice showed a higher percentage of dead eggs and a lower percentage of immature eggs than TR mice, but had similar quantities of collected eggs. This suggests that in TS mice the alterations in adult worm tegument prevented egg development, but not egg production or worm survival. These results corroborate our previous scanning electron microscopy (SEM) study indicating the influence of the host immune regulatory profile on the development and function of the worm's reproductive system and tegument.     

蒿甲醚对感染小鼠体内埃及血吸虫皮层的损害

目的 评价蒿甲醚对小鼠体内埃及血吸虫皮层的损害作用。 方法 8只小鼠于感染埃及血吸虫尾蚴后81 d，用单剂蒿甲醚400 mg/kg口服治疗。治疗后1、3、7和14 d各剖杀2只小鼠，用灌注法收集血吸虫，并按常规方法固定和处置虫体，作扫描电镜观察。从另2只未作治疗的感染小鼠取虫作对照。 结果 用蒿甲醚治疗后24 h，雄虫的皮层结节肿大、破溃或从皮层上剥落; 在雄虫和雌虫的体表可查见有局灶性或广泛的皮层肿胀、融合、空泡变化、糜烂和剥落，以及感觉结构的破坏。治疗后3 d，雌、雄虫的皮层损害加重，最严重的损害为口吸盘肿胀和破溃，并查见皮层褶嵴有广泛和严重的肿胀、糜烂和剥落，以及雌虫盘状感觉结构的破坏。治疗后7至14 d，有些虫仍示有中或重度皮层损害，而有些仍存活的虫则示其大部分皮层已有明显恢复。 结论 蒿甲醚对埃及血吸虫的皮层具有广泛和严重的损害作用。     

Tegumental changes in 21-day-old Schistosoma mansoni harboured in mice treated with artemether

Alterations in the tegument of 21-day-old Schistosoma mansoni, caused by artemether administered to the infected mice, were studied using scanning electron microscopy (SEM). Mice were infected with S. mansoni cercariae, and after 21 days a single dose of artemether (400 mg/kg) was administered intragastrically. After 24, 72 h and 7 days groups of three mice were killed and the schistosomules collected by perfusion, fixed and processed routinely, and examined by SEM. After 24 h, all male and female worms examined showed alterations in the tegument, characterised by swelling, vesiculation and fusion of tegumental ridges; peeling, erosion and collapse of damaged tegumental surface, and also destruction of the oral sucker and acetabulum. After 72 h, severe damage to the tegument was seen, usually including extensive peeling, swelling and vesiculation, and host leukocytes were adhered to the damaged surface. Some worms were surrounded by clusters of host leukocytes or had even disintegrated. Seven days after treatment, some schistosomules still showed severe tegumental damage, but in some cases the damage was less than at earlier times, which suggested that those schistosomules that had survived were beginning to recover. The ability of artemether to cause severe damage to the tegument correlates with its high efficacy in killing 21-day-old schistosomules.     

蒿甲醚对感染小鼠体内埃及血吸虫超微结构的影响

目的 观察蒿甲醚对小鼠体内埃及血吸虫成虫超微结构的损害。 方法 8只小鼠于感染埃及血吸虫尾蚴后81 d用单剂蒿甲醚400 mg/kg口服治疗。治后24 h、3 d、7 d和14 d各剖杀2只小鼠，用灌注法收集血吸虫，并按常规方法固定和处置虫体，作透射电镜观察。从另2只未治疗的感染小鼠体内取虫作对照。 结果 蒿甲醚对血吸虫皮层超微结构的损害主要是皮层基质的肿胀、溶解和空泡变化，基底膜消失和部份受损皮层破裂；在感觉器和皮层结节中，常见其内部结构广泛溶解。在肌层、实质组织、合体细胞和肠管上皮细胞中，查见局灶性或广泛的溶解、粗面内质网减少及线粒体空泡变化和变性。雌虫卵黄细胞的严重变化是空泡变化、粗面内质网减少、卵黄球融合以及受损卵黄细胞破溃等。上述雌、雄虫变化于感染小鼠用蒿甲醚治疗后24 h即可见到，并逐渐加重，3~7 d后最重。治后14 d，部分雌、雄虫仍示有超微结构的损害，但同时亦观察到受损虫组织的恢复。 结论 蒿甲醚对埃及血吸虫成虫的皮层和皮层下组织具有广泛和严重的超微结构损害。     

Immunization with newly transformed Schistosoma mansoni schistosomula tegument elicits tegument damage, reduction in egg and parasite burden

The surface of the schistosomula is an important target for host immune system attack because the tegument represents the interface between host and parasite and thus is a potential candidate for the development of new intervention strategies. In this study, we evaluated the ability of schistosomula tegument (Smteg) to induce protection in mice. Immunization of mice with Smteg together with Freund adjuvant induced a Th1 type of immune response associated with a significant reduction in worm burden (43-48%), eggs trapped in the liver (65%), eggs eliminated in the faeces (59-60%) and granuloma number (41%). Lastly, during an in vitro study, worms from mice immunized with Smteg showed damage in the adult worm tegument and impaired egg laying.     

环孢素A体外抗曼氏血吸虫雄虫的时间生物学研究

目的：探讨环孢素Ａ体外抗曼氏血吸虫的作用。方法：ＭＦ１小鼠实验感染曼氏血吸虫６ｗｋ后，经主动脉和门静脉灌注收虫。将雄虫放入含有１μｇ／ｍｌ、１０μｇ／ｍｌ、１５μｇ／ｍｌ、２０μｇ／ｍｌ和２５μｇ／ｍｌ环孢素Ａ的１９９培养液中体外培养。用扫描电镜对药物所致的虫体皮层损害作时间生物学观察。结果：在体外，雄虫经１μｇ／ｍｌ环孢素Ａ作用后，体嵴的结构疏松；经１０μｇ／ｍｌ环孢素Ａ作用２４ｈ后，雄虫皮层肿胀；雄虫经１５μｇ／ｍｌ环孢素Ａ作用８ｈ－２４ｈ后，虫体皮层破溃；虫体经２０μｇ／ｍｌ药物作用２４ｈ后，雄虫皮层明显破溃；雄虫经２５μｇ／ｍｌ环孢素Ａ作用８ｈ后，皮层褶嵴受损；作用１６ｈ后，皮层肿胀；作用２４ｈ后，皮层极度破溃，皮棘脱落。药物所致的虫体皮层损害与剂量和时间呈依赖关系。结论：环孢素Ａ具有直接杀曼氏血吸虫的作用。     

Schistosoma mansoni: interactions of adult parasites with the complement system

The interaction of the mouse complement system with adult male Schistosoma mansoni was studied by immunocytochemical localization procedures and in-vitro assays for complement mediated tegument damage. Mouse C3 was demonstrated to be associated with the parasite's tegument, but was localized only in the infoldings of the tegument and not on its free surface. Freshly harvested parasites manifested no detectable tegumental modification when incubated in normal mouse serum or in immune mouse serum. However, parasites which had been allowed to lose their adsorbed host components by elution (incubation in serum free media for 3 h at 37 degrees C) were severely damaged by incubation in normal mouse serum, but not by incubation in immune mouse serum. This damage was shown to be mediated by the alternative complement pathway and appeared to be initially limited to the tubercles of the adult male parasite. Tegument disruption could be blocked by pre-incubation of the eluted worms in either immune mouse serum or an IgG fraction of immune mouse serum. An IgG fraction of normal mouse serum did not protect the parasite, and infected mouse serum (IMS) which had been depleted of IgG produced tegument damage equivalent to that observed with normal mouse serum (NMS). The addition of I-IgG to NMS abrogated tegument damage. These data suggest that while adult schistosomes possess surface molecules bearing alternative pathway complement activation sites, these sites are masked by adsorbed host components in vivo. These results further indicate that in the absence of these masking host molecules anti-schistosome IgG may play a role in protecting the adult worm from alternative pathway activation, perhaps by binding to and blocking the activation sites on the tegument associated molecules.     

对硝基苯甲酰还原青蒿素对日本血吸虫童虫的作用

小鼠感染血吸虫尾蚴后第7d,1次灌服对硝基苯甲酰还原青蒿素300mg/kg。结果表明:给药后4h童虫皮层即有变化,8h已十分明显。主要表现为表皮水肿,皮层褶嵴融合,形成大量球状物或小泡。12h后皮层糜烂破溃剥落,并有白细胞附着于皮层损害处。从体表面积和体积的测量计算看,7～12d龄童虫生长基本停滞,而第13d又趋恢复。此结果为本药预防血吸虫病的最佳疗程的设计提供了科学依据。     

Liposomal-praziquantel: Efficacy against Schistosoma mansoni in a preclinical assay

Currently, schistosomiasis mansoni is treated clinically with praziquantel (PZQ). Nevertheless, cases of tolerance and resistance to this drug have been reported, creating the need to develop new drugs or to improve existing drugs. Considering the small number of new drugs against Schistosoma mansoni, the design of nanotechnology-based drug delivery systems is an important strategy in combating this disease. The aim of this study was to evaluate the activity of PZQ containing liposome (lip.PZQ) on S. mansoni, BH strain. Mice were treated orally with different concentrations of PZQ and lip.PZQ 30 and 45 days following infection. The number of worms, recovered by perfusion of the hepatic portal system, and the number of eggs found in the intestine and liver were analysed. Parasite egg counts were also performed. The most active formulation for all parameters was 300 mg/kg of lip.PZQ, since as it decreased the total number of worms by 68.8%, the number of eggs in the intestine by 79%, and the number of hepatic granulomas by 98.4% compared to untreated controls. In addition, this concentration decreased egg counts by 55.5%. The improved efficacy of the treatment with lip.PZQ, especially when administered 45 days following infection, compared with the positive-control group (untreated) and the groups that received free PZQ, can be explained by greater bioavailability in the host organism; the preferred target of lip.PZQ is the liver, and lip.PZQ is better absorbed by the tegument of S. mansoni, which has an affinity for phospholipids.     

Time-dependent tegumental surface changes in juvenile Fasciola gigantica in response to triclabendazole treatment in goat

Triclabendazole (TCBZ), the anthelmintic drug active against both mature and immature liver flukes, was used to investigate the effect of in vivo treatment on the tegumental surface of juvenile Fasciola gigantica. Five goats were infected with 150 F. gigantica metacercariae each by oral gavage. Four of them were treated with single dose of TCBZ at 10 mg/kg at four weeks post-infection. They were euthanized at 0 (untreated), 24, 48, 72 and 96 h post treatment. Juvenile flukes were manually retrieved from the goat livers and processed for scanning electron microscopy. In control flukes, the anterior region was adorned with sharply pointed spines projecting away from the surface, while in the posterior region, spines become shorter and narrower, loosing serration and with the appearance of distinct furrows and papillae. The dorsal surface retained the same pattern of surface architecture similar to that of ventral surface. Flukes obtained from 24 h post-treatment did not show any apparent change and were still very active. However, there were limited movements and some blebbing, swelling, deposition of tegumental secretions and some flattening displayed by the flukes of 48 h post-treatment. All the worms were found dead 72 h post-treatment and showed advanced level of tegumental disruptions, consisting of severe distortion of spines, sloughing off the tegument to expose the basal lamina, formation of pores and isolated patches of lesions. By 96 h post-treatment, the disruption was extremely severe and the tegument was completely sheared off causing deeper lesions that exposed the underlying musculature. The disruption was more severe at posterior than anterior region and on ventral than dorsal surface. The present study further establishes the time-course of TCBZ action in vivo with 100% efficacy against the juvenile tropical liver fluke.     

Antischistosomal action of atorvastatin alone and concurrently with medroxyprogesterone acetate on Schistosoma haematobium harboured in hamster: surface ultrastructure and parasitological study

Aiming to study the influence of long-term administration of lipid lowering agents (atorvastatin; AV), and to study the action of combined treatment with injectable contraceptive (medroxyprogesterone acetate; MPA) on tegumental ultrastrucutre and survival of Schistosoma worms, this study was established. AV (0.9 mg kg-1) was administered orally for 49 successive days to Schistosoma heamatobium-infected hamster starting from day 35 post-infection (pi). Another group of infected hamster was administrated MPA intramuscularly (0.1 ml kg-1) at days 7 and 35 pi followed by AV treatment regimen. Both treatment regimens significantly affected the surface ultrastructure of the male worms more pronouncedly than the female ones. Combined treatment was more severe in action compared to single one. The combined treatment was characterized by losing of spines and damaging of tubercles throughout the tegument, severe erosion and peeling and appearance of deep crakes in different parts of the tegument. Moreover, mild to sever destruction to the oral suckers of both female and male worms was noticed. On the other hand, both treatment regimens significantly reduced numbers of recovered S. haematobium worms and tissue egg load. Oogram pattern was affected only in case of combined treatment with high percentage of dead eggs. In conclusion, AV, if given continuously for long time, has a pronounced antischistosomal action especially when accompanied with contraceptive intake. These promising results may encourage further investigation with the intention of their possible application on treatment of schistosomiasis as a complement strategy to praziquantel chemotherapy.     

血吸虫对吡喹酮抗药性的研究Ⅴ吡喹酮对曼氏血吸虫吡喹酮抗性株和敏感株成虫皮层的损伤

目的 体内比较吡喹酮对曼氏血吸虫吡喹酮抗性株与敏感株成虫皮层的损伤程度。方法 用各虫株尾蚴分别感染小鼠,感染后第57天,以300mg/kg微粒化吡喹酮悬液对小鼠作灌胃治疗;在灌药后10、30min和1、12、24h后剖杀感染小鼠,门静脉灌注收集成虫,按常规方法制成扫描电镜标本,扫描电镜下观察成虫体表的变化。结果 吡喹酮诱导的皮层损伤主要为虫体表形成泡状结构的薄壁隆起;给药10min,敏感株雄虫皮层可见较多小泡状物,而抗性株则少见;1h后,敏感株虫体表可见大量的泡状物,泡状物溃破可形成皮层损伤灶,抗性株仅见少量的泡状物;24h后,敏感株雄虫体表完全受损,部分皮层剥落,暴露出肌肉层,而抗性株仅见少量泡状物和破损的泡状物。给药1h后,敏感株雌虫开始出现少量泡状物,抗性株雌虫体表未见泡状损伤;12h后,敏感株雌虫泡状物数量增加,抗性株仅在有限区域见少量泡状物。结论 抗性株和敏感株成虫体表吡喹酮诱导的皮层损伤程度存在明显差异,敏感株的损伤程度重于抗性株,雄虫重于雌虫。     

东方田鼠感染日本血吸虫后肺和肝的组织细胞反应及虫体的扫描电镜观察

目的：通过东方田鼠（Microtus fortis,Mf）感染日本血吸虫（Schistosoma japonicum,Sj）后肺和肝的组织细胞反应以及虫体受损情况，探寻Mf体内杀伤Sj的效应细胞和Sj的受损原因。方法：以Sj尾蚴经腹部皮肤感染Mf5d和11d后剖杀，分别取肺和肝，固定，切片，光镜下观察虫全周围的组织细胞反应，并与同时期的感染小鼠组织切片进行比较，同时，对Mf体内的Sj童虫进行扫描电镜观察。结果：Mf肺脏虫体周围有一定量的嗜酸性粒细胞浸润，而肝脏虫体周围有大量的嗜酸性粒细胞和少量的中性粒细胞，巨噬细胞等浸润，同时期的感染小鼠组织内虫体周围炎症反应不明显，电镜观察显示Mf体内的Sj存在明显的畸形和发育延迟，结论：嗜酸性粒细胞可能是Mf体内杀伤Sj的重要效应细胞，Sj在Mf体内不能正常发育。     

日本血吸虫吡喹酮耐药虫体筛选及其超微结构观察

目的应用吡喹酮(PZQ)亚治疗剂量对感染小鼠体内日本血吸虫虫体进行药物压力下的耐药虫体筛选,并探讨经筛选后的虫体对PZQ的敏感性及其超微结构变化。方法应用日本血吸虫雄虫PZQ半数有效致死剂量(ED50)为亚治疗剂量,对感染6周后小鼠喂饲给药30d;肝门静脉灌注法收集雄性成虫体外培养,加入不同浓度PZQ连续培养5d,根据虫体活力,评价对PZQ的敏感性,同时用扫描电镜观察虫体超微结构的变化。结果经实验获得日本血吸虫雄虫PZQ的ED50为20.89mg/kg;应用该剂量对感染小鼠体内连续用药30d后,体外培养观察显示虫体对PZQ敏感性显著下降,扫描电镜观察表明皮层及抱雌沟损害较正常虫体明显减轻;筛选后虫体再用治疗剂量PZQ200mg/kg连续给药5d后,体外培养观察显示,虫体在不同浓度PZQ作用下存活率仍达100%,扫描电镜显示体表及抱雌沟损害比单纯用药30d的虫体更轻。结论在持续药物压力下,感染宿主体内的日本血吸虫可能对PZQ产生一定的耐受性。     

蒿甲醚对曼氏血吸虫的作用:剂量与效应的关系和虫的形态学和组织病理学的变化

目的　应用感染曼氏血吸虫 (利比里亚株 )的小鼠观察蒿甲醚单剂量与效应的关系,虫体肝移及蒿甲醚所引起的虫的形态学和组织病理学变化。　方法　感染21d童虫的小鼠一次口服蒿甲醚12.5mg/kg至600mg/kg不同剂量 ,治后28d剖检观察各组虫数。感染46d或70d成虫的小鼠一次口服蒿甲醚40 0mg/kg后8～14d ,观察虫体肝移及其形态和组织病理学变化。　结果　蒿甲醚对21d童虫的最低有效剂量为200mg/kg ,减虫率为 81%。用蒿甲醚治疗后8h成虫开始肝移,3～7d全部肝移,14d有31%的虫返回肠系膜静脉。成虫虫体萎缩,咽部扩大,肠管膨胀及其色素减少。雌虫局部体表受损,白细胞附着,卵巢及卵黄腺变性退化,以及雄虫睾丸萎缩等。在肝内的虫体被嗜酸粒细胞为主的炎细胞包围和浸润。　结论　蒿甲醚对小鼠曼氏血吸虫21d童虫的最低有效剂量为200mg/kg ,可引起曼氏血吸虫成虫萎缩、退化或死亡。在肝内受损的虫体主要是被嗜酸粒细胞包围和侵袭所致。     

Differential expression and localization of saposin-like protein 2 of Fasciola hepatica

FhSAP2 is a novel antigen isolated from the adult fluke of Fasciola hepatica. Based on sequence similarity with amoebapores and other related proteins, it belongs to the saposin-like protein (SAPLIP) family. FhSAP2 has been shown to be highly immunogenic and capable of inducing protective immune responses in mice and rabbits challenged with F. hepatica. Moreover, FhSAP2 is also reactive with sera from humans with chronic fascioliasis. In the present study, we investigated the expression of FhSAP2 in various developmental stages of F. hepatica by qPCR and demonstrated that FhSAP2–mRNA species are up-regulated in undeveloped eggs, newly excysted juveniles, and adults, but down-regulated in the miracidium stage. Monoclonal antibodies against FhSAP2 were produced, and two clones that are positive to F. hepatica whole-body extract, but not reactive with extracts from other trematodes, were selected, expanded and used for histolocalization studies. Confocal immunofluorescence revealed the presence of native FhSAP2 in epithelial cells surrounding the gut, toward the outermost part of the tegument, and toward the tegumental cells of both adults and newly excysted juveniles.     

Production and characterization of a monoclonal antibody against 28.5 kDa tegument antigen of Fasciola gigantica

A monoclonal antibody (MoAb) against the 28.5 kDa tegumental antigen of Fasciola gigantica was produced by the hybridoma technique using spleen cells from BALB/c mice immunized with the tegumental extract from adult F. gigantica. This MoAb was found to be of the isotype IgG(1), kappa-light chain, and shown by immunoblotting to specifically react with the 28.5 kDa antigen present in the tegument, excretion-secretion material of the adult, whole-body extracts of newly excysted juveniles, 5-week-old juvenile and adult parasites. It did not cross-react with antigens from other trematode parasites, including Schistosoma mansoni, Eurytrema pancreaticum and Paramphistomum spp. Immunolocalization of this antigen by indirect immunofluorescence indicated that it was present as a major component of the adult tegument, particularly in its outer rim, tegumental cells, and their processes. Furthermore, the epithelium linings of the oral sucker, buccal tube, pharynx, caecal bifurcation, both male and female genital canals, which were the continuation of the tegumental-type epithelium, were also positively stained with this MoAb. A similar pattern of immunolocalization, but with weaker staining intensity, was observed in newly excysted, 5- and 7-week-old juveniles. Thus this antigen is expressed in all developmental stages of the parasite, and it could be a strong candidate for immunodiagnosis and vaccine development.     

Surface topography and ultrastructural architecture of the tegument of adult Carmyerius spatiosus Brandes, 1898

Adult Carmyerius spatiosus or stomach fluke has an elongate, cylindrical-shaped, straight to slightly curved body, with conical anterior end and truncated posterior end. The worm measures about 8.7–11.2 mm in body length and 2.3–3.0 mm in body width across the mid-section. When observed by SEM, the tegumental surface in all part of the body appears highly corrugated with ridges and furrows, and having no spines. The ventral surface has more complex corrugation than those of the dorsal surface. Both anterior and posterior suckers have thick edges covered with transverse folds and appear spineless. The genital pore is located at the anterior part of the body. There are two types of sensory papillae on the surface: type 1 is bulbous in shape with nipple-like tips; type 2 has a similar shape with short cilia on the tip. The dorsal surface exhibits similar surface features, but papillae appear less numerous and are smaller. When observed by TEM, the tegument is divided into four layers. The first layer includes the ridges and furrows which are covered by a trilaminate membrane underlined by a dense lamina and coated externally with the glycocalyx. The second layer of the tegument is a narrow region of cytoplasm that contains high concentrations of ovoid electron lucent tegumental granules (TG₁), and disc-shaped electron dense tegumental granules (TG₂) as well as lysosomes. TG₁ close to the surface invariably exocytose their content into bottoms of the ridges, while some TG₂ are fused and have their membrane joined up with the surface membrane. The third layer is the widest middle area of the tegument which contains numerous and evenly distributed mitochondria. Both TG₁ and TG₂ granules are present but in much fewer number than in the first and second layers. The fourth layer is the innermost zone that rests on and couples with a thick basal lamina. The cytoplasm in this layer is loosely packed and contains numerous infoldings of the basal plasma membrane with closely associated mitochondria. It also contains fairly large numbers of TG₁ and TG₂ granules which are produced and transported to the tegument by one type of tegumental cells lying in rows underneath the muscular layers.     

紫外线致弱日本血吸虫尾蚴感染小鼠引起的肺组织细胞反应及虫体扫描电镜观察

目的通过观察日本血吸虫(Schistosoma japonicum,Sj)紫外线辐照致弱尾蚴感染小鼠后肺组织的细胞反应以及肺期虫体的受损情况,探寻致弱尾蚴在小鼠体内诱导免疫效应机制和Sj受损情况。方法以紫外线致弱Sj尾蚴经腹部皮肤感染小鼠4d、7d、14d和45d后剖杀,分别取肺组织,固定、切片,光镜下观察虫体周围的组织细胞反应,并与同时期的感染小鼠组织切片进行比较,同时,对小鼠体内肺期Sj童虫进行扫描电镜观察。结果感染后4~7d,小鼠肺期童虫虫体周围出现较明显的出血灶和炎症反应,并有一定量的嗜酸性粒细胞、中性粒细胞、巨噬细胞等炎症细胞的浸润,同时期的正常感染小鼠组织内虫体周围炎症反应却不明显;虫体体壁可见不同程度的损伤,电镜观察显示小鼠体内的肺期童虫存在明显的畸形和发育延迟。结论紫外线辐照致弱尾蚴感染后Sj在小鼠体内不能正常发育成熟,和正常尾蚴相比,致弱尾蚴在肺期滞留时间较长,仅有极少数虫体可移行至肠系膜或肝脏,但宜不能发育成熟,引起的病理损害主要表现为在肺期弥漫性出血灶、炎症细胞浸润等反应,这些特征可能与血吸虫致弱尾蚴感染免疫机制有关。     

Antigenicity and immunogenicity of the tegumental outer membrane of adult Schistosoma mansoni

The tegumental membranes of adult Schistosoma mansoni have been isolated and purified and shown to function as potent immunogens; they elicit an essentially identical immune response in rabbits, rats and mice. Anti-membrane antisera harvested from these animals consistently recognized common antigens, of relative molecular weight (mol. wt) 32 000 and 20 000, on the surface of young schistosomula, 5 day old lung worms and adult worm purified membranes. An additional molecule of 25 000 mol. wt was present on the surface of lung worms and adult worm membranes and was specifically recognised by serum from chronically infected mice and by serum from rabbits inoculated with adult worm purified membranes. The concept of antigenic identity between developmental stages that parasitize the mammalian host was further substantiated by the observation that anti-membrane antiserum bound to live schistosomula, lung worms and adult parasites as measured by indirect immunofluorescence. In complement-mediated in vitro cytotoxicity assays, the sera from rabbits inoculated with either adult worm purified membranes, or the 32 000 mol. wt antigen partially purified from adult worm membranes, mediated levels of schistosomula killing as high as those obtained with sera from chronically infected mice. These rabbit antisera also promoted eosinophil adherence and killing of newly transformed schistosomula, but lung stage parasites, despite binding the anti-membrane antiserum, were refractory to both humoral and cellular cytotoxicity. The significance of antigenic identity is discussed in relation to the concept of concomitant immunity.