IL-18 enhances protective effect in mice immunized with a Schistosoma japonicum FABP DNA vaccine

Two recombinant plasmids, pVAX/SjFABP and pVAX/mIL-18 containing Schistosoma japonicum 14 kDa fatty acid binding protein (SjFABP) and murine IL-18, were constructed and evaluated for their ability to induce immune responses and to protect against S. japonicum challenge in mice. Mice were intramuscularly immunized twice at three-weekly intervals, and challenged with S. japonicum cercariae at 4 weeks after the last vaccination. All animals vaccinated with pVAX/SjFABP alone or plus pVAX/mIL-18 developed specific anti-SWAP ELISA antibody and T lymphocyte proliferation. Co-injection of pVAX/mIL-18 significantly increased the production of IFN-γ and IL-2 compared with pVAX/SjFABP alone, indicating that IL-18 enhances the Th1-dominant immune response. The challenge experiment showed that co-injection of plasmid encoding IL-18 significantly enhances protective effect against S. japonicum infection, as demonstrated by worm reduction rates and the hepatic egg reduction rates 45 days post-challenge. These results indicated that IL-18 may become a novel vaccine adjuvant for development of vaccines against schistosomiasis.     

日本血吸虫可溶性虫卵抗原经两种免疫途径获得的鸡卵黄抗体IgY动态观察

目的对比两种免疫途径产生抗日本血吸虫可溶性虫卵抗原(SEA)的特异性IgY抗体水平动态变化。方法7只新西兰兔感染日本血吸虫尾蚴(1500/只)42d后解剖收集虫卵,制备SEA。将SEA分别经皮下和静脉注射免疫健康海蓝蛋鸡(3只/组),首次和第2次免疫间隔2周,之后每次间隔4周,共免疫5次,50μg/(只·次)。取两组免疫前,以及首次免疫后2～18周生产的鸡蛋,用水稀释法粗提IgY,ELISA检测每2周IgY的动态变化。IgY纯化试剂盒(EGGstract IgY Purifiction System)纯化静脉组首次免疫后8～18周的IgY,紫外吸收法检测抗体浓度,琼脂糖双扩散法和ELISA检测IgY峰值水平的抗体效价,十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)和蛋白质印迹(Western blotting)分析比较免疫前后抗体特异性。结果静脉组和皮下组分别在首次免疫后8和12周IgY抗体水平达高峰,A492值分别为1.28和0.78,静脉组IgY水平至18周仍维持较高水平,皮下组抗体水平达到峰值后逐渐下降。纯化后IgY浓度约为6.5～9.0mg/ml,琼脂糖双扩散法和ELISA测得静脉注射组峰值水平抗体效价分别为1∶16和1∶51200。经SDS-PAGE和Western blotting分析,纯化后的IgY在相对分子质量(Mr)25000和68000处各有一条清晰条带,且免疫后IgY可与SEA发生特异性反应。结论静脉注射法比皮下注射法能获得更高水平的鸡抗日本血吸虫SEA特异性IgY抗体,且纯化后的IgY抗体具有较好的特异性。     

日本血吸虫重组线粒体相关蛋白免疫学活性鉴定

分子筛进一步纯化并复性的融合蛋白均能刺激家兔产生特异性抗体 ,粗提包涵体蛋白免疫家兔 ,血清抗体滴度为 1∶2 5 6 0 0 ,复性蛋白及经分子筛纯化的蛋白免疫的家兔血清抗体滴度均为 1∶5 12 0 0 ,Westernblot结果显示 ,粗提包涵体蛋白、复性蛋白及经过分子筛进一步纯化并复性的蛋白均能被重感染兔血清和rSj338/2 6GST特异性免疫兔血清所识别。攻击实验中 ,粗提包涵体蛋白和经分子筛纯化的蛋白分别可诱导小鼠产生 2 7.8% (P <0 .0 1)和 30 .4 % (P <0 .0 1)的减虫率 ,4 0 .4 % (P <0 .0 1)和 4 3.5 % (P <0 .0 1)肝总减卵率。粗提包涵体蛋白中rSj338和经分子筛纯化的蛋白中rSj338分别可诱导小鼠产生 13.9% (P <0 .0 5 )和 2 0 .0 % (P <0 .0 5 )的减虫率 ,30 .0 % (P <0 .0 1)和 4 1.7% (P <0 .0 1)肝总减卵率。结论　获得的日本血吸虫线粒体相关的重组融合蛋白(rSj338/2 6GST)具有良好的免疫学活性 ,重组融合蛋白 (rSj338/2 6GST)及rSj338均可诱导宿主抗血吸虫感染的部分保护力。     

日本血吸虫体表蛋白Tetraspanin 2-A核酸疫苗的构建及其对小鼠的免疫试验

采用PCR法扩增日本血吸虫体表四跨膜家族蛋白2-A（SjTsp2-A）基因,构建重组质粒pcDNA3.1（+）/SjTsp2-A,将其转至大肠埃希菌DH5α制备DNA疫苗pcDNA3.1（+）/SjTsp2-A。24只BALB/c小鼠均分3组,每鼠于左股四头肌注射0.5 mg/ml盐酸布比卡因50 μl。次日,A组同法注射DNA疫苗pcDNA3.1（+）/SjTsp2-A,B组注射重组质粒pcDNA3.1（+）/SjGST,C组注射空质粒pcDNA3.1（+）。注射剂量均为100 μg/只。每隔2周注射1次,共3次,末次免疫后2周各组均经腹部皮下感染日本血吸虫尾蚴40±2条/鼠,45 d后剖杀,计数减虫率和减卵率。ELISA检测抗体效价,A组化分析股四头肌局部组织蛋白表达情况。结果A组的平均检虫数和每克肝组织虫卵数均显著低于B组和C组（P值均<0.05）,A组的减虫率和减卵率分别为44.4%和28.4%。A组血清抗体效价高达1 ∶ 25 600。A、B两组局部组织均有特异性蛋白表达。DNA候选疫苗pcDNA3.1（+）/SjTsp2-A能诱导小鼠产生一定的免疫保护作用。     

microRNA在小鼠血吸虫病及吡喹酮治疗中的表达特征

目的 目的 探究炎症调节基因miR?155和miR?146a及炎症相关基因在小鼠血吸虫病及吡喹酮治疗中的表达特征, 为 进一步阐明吡喹酮治疗血吸虫病的作用机制奠定基础。方法 方法 以BALB/c小鼠为研究对象, 建立日本血吸虫感染的动物模 型; 小鼠随机分为4组： 正常组、 感染6周组、 感染12周组和吡喹酮 （PZQ, 300 mg/kg 1次灌胃杀虫治疗） 治疗组。以HE染色 观察肝脏病理变化; 以Real?time PCR检测肝脏miR?155和miR?146a及炎症相关基因TNF?α、 IL?1β和IL?6的mRNA水平。 结果 结果 感染6周组小鼠的肝脏miR?155、miR?146a及TNF?α、 IL?1β和IL?6的mRNA水平均显著高于正常组和感染12周组 （P＜0.05）; 与感染12周组小鼠相比, PZQ治疗组小鼠肝脏虫卵肉芽肿反应减轻, 且肝脏miR?155、 miR?146a及TNF?α、 IL?1β 和IL?6的mRNA水平有所升高（P＜0.05）。结论 结论 本研究发现miR?155和miR?146a可能与血吸虫病肝脏炎症的发生发展 有关, 并且参与了吡喹酮对炎症的调节。     

Reversal of hepatic fibrosis after praziquantel therapy of murine schistosomiasis

We examined the effect of parasitologic cure of S. mansoni infection on liver fibrosis in mice. Praziquantel, 250 mg/kg body weight, was administered orally to mice 8 weeks after infection with 50 S. mansoni cercariae. We assessed liver fibrosis by chemical measurement of collagen content as measured by the estimation of hydroxyproline and by histologic examination at the time of treatment, and at 10 and 20 weeks post-treatment, in comparison with the same measurements in untreated S. mansoni-infected mice and age-matched normal control mice. The extent of infection was monitored by liver egg counts. Compared to normal uninfected mice, mice with untreated S. mansoni infection showed steady accumulation of liver collagen at the 3 measurement periods, reaching an average level of 15-fold greater than that found in normal mice at 28 weeks after infection. Mice treated with praziquantel showed a prompt decrease in S. mansoni liver egg load with no viable eggs 10 weeks after treatment. Liver fibrosis was modestly diminished in treated mice compared to untreated controls 10 weeks after treatment; fibrosis was arrested and liver collagen content had diminished to normal levels by 20 weeks after treatment. No praziquantel toxicity was noted. The survival of treated mice was markedly greater than that of untreated infected animals. We conclude that parasitologic cure of murine S. mansoni infection is followed by arrest and eventual partial reversal of liver fibrosis under the conditions employed.     

Detection of high molecular weight eosinophil chemotactic factor in murine schistosomiasis sera

Eosinophil chemotactic activity in sera from mice undergoing an acute stage of schistosomiasis japonica and mansoni was examined. Eosinophilotactic activity in the serum was dependent on the dose and time of infection. Eosinophilotactic activity in sera from S. japonicum-infected mice was higher than that from S. mansoni-infected mice when they were compared at the comparable dose and time of infection. After gel chromatography on Sephadex G-200, eosinophilotactic activity in sera from mice infected with 30 cercariae of S. japonicum for 5 weeks was detected in the high molecular weight component. On the other hand, when sera from mice infected with 30 cercariae of S. japonicum for 8 weeks was chromatographed through Sephadex G-200 columns, eosinophilotactic activity was segregated into high (greater than 455,000) and low (less than 13,000) molecular weight components. High molecular weight ECF in sera from mice infected with 30 cercariae of S. japonicum for 8 weeks had high affinity to Con A, and was stable to heating or pronase digestion, but was sensitive to periodate oxidation, indicating its polysaccharide or glycoprotein nature. This high molecular weight ECF could be adsorbed by, and eluted from immunoaffinity beads coated with rabbit IgG anti-S. japonicum adult worm antibody. Thus, at least some part of circulating high molecular weight ECF would be derived from adult parasites.     

The effect of praziquantel on the circulating antigen SJ 70 in murine schistosomiasis japonica

A circulating schistosome 70 kDa antigen (SJ 70) has been detected in the sera of mice infected with Schistosoma japonicum. For the detection of this antigen, a double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was employed. SJ 70 is first detected in the serum of S. japonicum-infected mice 4 weeks after infection. Antigen levels rise rapidly, plateau by 7 weeks after infection, and remain relatively unchanged for at least another 9 weeks. In mice infected with S. japonicum for 7 weeks and then treated with praziquantel (100 mg/kg body weight), there is a significant decrease in serum antigen levels within 2 weeks after treatment, and an almost complete disappearance of antigen from the serum 3-4 weeks after treatment.     

Protection of mice against Schistosoma mansoni infection by passive transfer of sera from infected rabbits

Sera from rabbits infected with unattenuated Schistosoma mansoni cercariae conferred significant levels of protection against S. mansoni challenge ( P  < 0.001) after passive transfer to mice. Infected rabbit sera were only effective in conferring protection when transferred during the first week of infection, and were not effective when administered against liver-stage worms. Immunoglobulins isolated from the infected rabbit sera with Protein A-Sepharose were shown to be responsible for the transfer of protection to mice. Immunofluorescence studies demonstrated that the sera were more reactive against the surface of three hour-old mechanically transformed schistosomula than against the surfaces of lung-stage schistosomula. The sera from infected rabbits reacted polyspecifically against antigens in cercaria, schistosomula, and the worm and egg stages of the S. mansoni life-cycle. The host parasite relationship of S. mansoni in the rabbit is discussed.     

Sequential analysis of helminth egg output in human stool samples following albendazole and praziquantel administration

Large-scale administration of anthelminthic drugs currently is the most widely used intervention for controlling morbidity due to schistosomiasis and soil-transmitted helminthiasis. An important issue is drug efficacy monitoring. However, the optimal time points post-treatment for assessing the efficacy of praziquantel against Schistosoma mansoni and albendazole against hookworm infections are not known. Forty-nine schoolchildren infected with S. mansoni and 52 infected with hookworm were treated with a single oral dose of praziquantel (40 mg/kg) and albendazole (400 mg), respectively. Stool samples were collected on 19 occasions over a 44-day post-treatment follow-up period, and two Kato-Katz thick smears per sample were examined at each time point. Both the mean egg counts and observed cure rates varied depending on the time point post-treatment. The highest reduction in the geometric mean egg counts (>97%) and the highest observed cure rate (>97%) of S. mansoni infections were found 15-20 days after praziquantel administration. Among the hookworm-infected children, egg counts decreased rapidly within the first week after albendazole administration (>95%), whereas infection rates showed high and heterogeneous (45.0-71.2%) levels at later time points. Both praziquantel and albendazole were highly efficacious in reducing the overall egg burden of S. mansoni and hookworm, respectively. We suggest that 15-20 days post-treatment is the most appropriate time point for efficacy evaluation of praziquantel against S. mansoni. Although no clear conclusion can be drawn for the optimal timing of efficacy evaluation of albendazole against hookworm, a 2-3-week time frame seems a reasonable compromise. This is justified on logistical grounds (i.e. collection of stool samples only once) and growing emphasis on integrating the control of schistosomiasis and soil-transmitted helminthiasis, including drug efficacy monitoring.     

吡喹酮治疗对实验小鼠日本血吸虫循环SJ70抗原的影响

采用双夹心酶联免疫吸附试验(双夹心ELISA)检测实验感染日本血吸虫小鼠体内循环SJ70抗原。发现感染后第4wk,即可检出此种抗原。此后,循环SJ70抗原的检出量与检出率逐周增高;至感染第7wk,全部小鼠均检出SJ70抗原,且其检出量达高峰。并持续到感染第16wk。吡喹酮治疗后,小鼠体内SJ70抗原水平逐周下降。至治疗后第5wk时,16只小鼠中14只已不再检出SJ70搞原。另2只小鼠的循环抗原水平降至近消失水平。而2只虽经吡喹酮治疗但未治愈小鼠的SJ70抗原水平无明显变化。     

血吸虫对吡喹酮抗药性的研究XⅧ日本血吸虫吡喹酮抗性株与敏感株混合感染子代成虫对吡喹酮的敏感性

目的　测定实验诱导产生的日本血吸虫吡喹酮抗性株与实验室保种传代的日本血吸虫吡喹酮敏感株混合感染后产生的子代成虫对吡喹酮的敏感性。方法　取实验室诱导产生的日本血吸虫吡喹酮抗性株[吡喹酮半数有效剂量（ED50值）为277.4 mg/kg]尾蚴与实验室传代保种的日本血吸虫吡喹酮敏感株（吡喹酮ED50值为99.6 mg/kg）尾蚴,分别按1∶1和2∶1混合后感染小鼠。后在实验室经小鼠⁃钉螺循环8代后,取尾蚴感染小鼠。感染35 d后将小鼠分为对照组及5个给药组。5个给药组分别按37.5、75、150、300 mg/kg和600 mg/kg剂量一次性灌胃给予吡喹酮,对照组给予2.5%聚氧乙烯蓖麻油。给药14 d后解剖鼠并以静脉灌注法收集成虫,计算减虫率及吡喹酮对虫株的ED50值。取经12轮亚治疗剂量吡喹酮诱导筛选的日本血吸虫吡喹酮抗性株,置实验室经小鼠⁃钉螺循环常规传代,取子8代日本血吸虫尾蚴感染实验鼠,测定吡喹酮对此子代成虫的ED50值。结果　日本血吸虫吡喹酮抗性株与敏感株尾蚴按1∶1混合感染小鼠后,吡喹酮对子8代成虫ED50值为135.2 mg/kg;日本血吸虫吡喹酮抗性株与敏感株尾蚴按2∶1混合感染小鼠后,吡喹酮对子8代成虫ED50值为129.2 mg/kg;日本血吸虫吡喹酮抗性株未予吡喹酮压力传代,吡喹酮对子8代后成虫ED50值为208.4 mg/kg。 结论　与实验室诱导的抗性株相比,日本血吸虫吡喹酮抗性株与敏感株尾蚴混合感染同一宿主后所获的子代成虫对吡喹酮抗性有所降低。日本血吸虫吡喹酮抗性株不经药物压力传代,其子代成虫仍可能够维持对吡喹酮的抗性。     

日本血吸虫模拟短肽诱导小鼠的免疫保护性研究

目的　研究日本血吸虫模拟短肽对小鼠的免疫保护效果,预测其在抗血吸虫感染中的作用。　方法　用粗提纯大鼠血清IgG为配基对噬菌体肽库进行3轮免疫学筛选。随机挑取噬菌体克隆,检测其特异性并进行序列分析;用阳性克隆免疫小鼠,以40条日本血吸虫尾蚴攻击感染,感染后42d剖杀取虫,计算减虫率和减卵率;用ELISA测定免疫鼠抗体反应。　结果　经过3轮筛选,特异性噬菌体得到有效富集;自动测序仪测序获得2个模拟肽分子;将其用于免疫小鼠后,各免疫组与对照组相比,2个模拟肽混合免疫组的减虫率为34.9%P<0.05,肝内减卵率为67.6%(P<0.001)。 2个模拟肽分子分别免疫小鼠 ,各组的减虫率为31.0%(P<0.05)和14.5%(P>0.05)及肝内减卵率为61.2%(P<0.001)和35.7%(P<0.05)。ELISA检测其免疫组鼠血清特异性IgG抗体滴度均大于1∶6 400以上。　结论　利用噬菌体表面呈现技术获得的2个模拟肽分子均可诱导部分抗日本血吸虫感染的免疫保护力     

Schistosomiasis from S. mansoni in mice: the relationship between acquired immunity and serum levels of lethal antibody

Acquired immunity to Schistosoma mansoni induced by a primary infection with cercariae of one or both sexes was assessed in mice by the recovery of parasites of a challenge infection from the lungs or the liver. In addition, the antibody-dependent complement-mediated cytotoxicity against schistosomula in vitro was titrated in sera obtained from both groups of animals. The degree of immunity as detected by the lung recovery technique in mice infected with a mixture of male and female cercariae was variable and lower than 50%. In contrast, no immunity was observed in the group of animals infected with 40 ‘single-sex’cercariae. The titre of lethal antibody in a pool of sera from these animals was about 10, whereas it was about 640 in a pool of sera from bisexually infected animals. Lethal antibody titres ranged from 20 to 120 for unisexual infection and 240 to 1920 for bisexually infected mice. In some cases a significant degree of immunity was detected by liver perfusion in mice with a primary unisexual infection. However, the lethal antibody titre of sera from mice with a 'single-sex’infection remained low, even when the immunity was apparent.     

日本血吸虫体表蛋白rSj29的保护性效果

目的 克隆表达日本血吸虫体表蛋白Sj29基因,分析其表达特性和免疫保护效果。 方法 根据日本血吸虫体表蛋白Sj29基因序列（GenBank登录号为AY814537）设计引物,PCR扩增目的基因,生物信息技术分析序列特性。将目的基因部分片段亚克隆到原核表达载体pET28c中,构建重组质粒pET28c-Sj29,将其转至大肠埃希菌后用异丙基-β-D-硫代半乳糖苷（IPTG）诱导表达,组氨酸（His）柱亲和层析法纯化重组蛋白;蛋白质印迹(Western blotting)分析其免疫原性。30只雌性BALB/c小鼠均分3组,实验组每鼠皮下多点注射重组蛋白rSj29共100 μl（0.1 mg/ml,用206佐剂配制）、佐剂对照组和空白（PBS）对照组,分别免疫3次,每次间隔2周。末次免疫后2周用血吸虫尾蚴攻击感染小鼠,每鼠40±2条,感染后第53天剖杀,收集虫体计算减虫率;取肝脏和粪便计算减卵率。ELISA法检测实验鼠血清特异性IgG抗体水平,免疫组织化学法检测rSj29蛋白在各期虫体的定位,荧光定量PCR法分析各期虫体及攻击感染后42 d虫体Sj29基因表达水平。 结果 获得576 bp的Sj29基因。重组蛋白的相对分子质量（Mr）为22 900,以包涵体形式存在。Western blotting表明,重组蛋白可被免疫小鼠血清和感染日本血吸虫的小鼠血清识别。攻击感染后42 d,小鼠体内Sj29基因转录水平分别为佐剂对照组和空白对照组虫体的9.1倍和51.8倍。实验组小鼠成虫数（15.4±5.9）、肝组织虫卵数（40 143.3±2 995.9）和粪便虫卵数（3 803.9±110.9）与空白对照组相比,差异均有统计学意义（P<0.05）。ELISA结果显示,免疫小鼠可产生高滴度（1 ∶ 32 000）特异性IgG抗体。免疫组织化学结果表明,重组蛋白rSj29可在7、14 d童虫,28、32 d成虫和42 d雄、雌虫的体表表达。荧光定量PCR结果表明,虫龄为32 d的日本血吸虫成虫Sj29基因转录水平最高。 结论 重组蛋白rSj29有一定的免疫保护效果。     

Praziquantel treatment of school children from single and mixed infection foci of intestinal and urogenital schistosomiasis along the Senegal River Basin: monitoring treatment success and re-infection patterns

Following major water development schemes in the 1980s, schistosomiasis has become a serious parasitic disease of children living in the Senegal River Basin. Both urogenital (Schistosoma haematobium) and intestinal (Schistosoma mansoni) schistosomiasis can be highly prevalent in school-aged children, with many individuals infected with both parasites. In order to investigate the transmission and re-infection dynamics of both parasite species, single and mixed infection foci at three villages (Nder and Temeye; S. mansoni and S. haematobium foci and Guia; S. haematobium focus) were studied. In each focus infected children were identified and selected for a 12-month study involving two treatments with praziquantel (40 mg/kg) three weeks apart at the beginning of the study and again 6 months into the study. Urine and stool samples were examined for schistosome eggs before and at 6 weeks and 6 months after chemotherapy. Prevalence and intensity of infection were recorded for each child at each time point. Before treatment, in all three villages, the prevalence and intensity of infection was extremely high for both S. mansoni (79–100%) and S. haematobium (81–97%). With the first round of chemotherapy sufficient cure rates (CRs) of both species were achieved in all villages (38–96%) with high egg reduction rates (ERRs) (97–99%). The data show that high and rapid re-infection rates occur, especially for S. mansoni, within a six-month period following treatment. Re-infection must be highly linked to ecological and seasonal factors. The persistence of S. mansoni in Nder could raise concern as levels of infection intensity remain high (geometric mean intensity at baseline 653 epg changed to 705 epg at 12 months) after four rounds of chemotherapy. This phenomenon could be explained by extremely rapid re-infection dynamics or a sub-optimal efficacy of praziquantel against S. mansoni in this village. High intensities in mixed infections may influence disease epidemiology and control warranting further studies. The disease situation in the SRB must be monitored closely and new treatment regimes should be designed and implemented to control schistosomiasis in the school-age population.     

应用磁分离酶联免疫技术检测抗日本血吸虫虫卵抗体

目的 建立检测日本血吸虫病患者血清中特异性虫卵抗体的磁微粒分离酶联免疫法（MPAIA）。方法 采用异硫氰酸荧光素（FITC）标记日本血吸虫可溶性虫卵抗原（Sj-SEA）为检测抗原, 标记羊抗FITC抗体的磁微粒为固相载体, 碱性磷酸酶（ALP）标记羊抗人免疫球蛋白G（IgG）作为酶标二抗, 以单磷酸酚酞溶液为底物, 检测日本血吸虫病患者血清中虫卵特异性抗体。 结果 用磁微粒分离酶联免疫法检测日本血吸虫虫卵抗体, 阳性检出率为96.7%（116/120）, 与旋毛虫、并殖吸虫、嚢尾蚴等其他寄生蠕虫抗体无交叉反应现象, 检测试剂4 ℃可保存12个月。灵敏度参考品的灵敏度为1 ∶ 1 600, 精密度参考品的精密度（CV）＜10%。 结论 磁微粒分离酶联免疫法具有灵敏度高、特异性强、技术先进, 试剂保存时间长等特点。     

Schistosoma japonicum: susceptibility of neonate mice born to infected and noninfected mothers following subsequent challenge

This study was to investigate the differences between neonate mice born to Schistosoma japonicum‐infected mothers and those born to noninfected mothers in subsequent challenge. The intensity of infection (evidenced by worm burden and liver egg burden) and liver immunopathology (number and size of liver granulomas) were significantly reduced in neonates from infected mothers (I.M.) compared with neonates from noninfected mothers (N.M.). Anti‐soluble worm antigen of S. japonicum (SWA) IgG could be detected in sera of neonates from I.M. (N.N./I.M.) at 1 week after delivery, remained a plateau for 2 weeks and gradually decreased until 8 weeks of age. Parasite‐specific IgM was not detected in sera from N.N./I.M. at any time after delivery. At 6 weeks after infection, the level of anti‐SWA IgG in infected neonates from I.M. (I.N./I.M.) was significantly higher than that of infected neonates from N.M. (I.N./N.M.). In addition, production of IFN‐γ, IL‐12 and TGF‐β by cultured splenocytes from I.N./I.M. was significantly increased, while the level of IL‐4 was significantly decreased when compared to those from I.N./N.M.. These data demonstrate that congenital exposure to schistosomiasis japonica may render neonatal mice born to I.M. less susceptible to subsequent challenge and result in down‐regulation of both infection intensity and immunopathology.     

Infection induces antibodies against the cercarial secretions, but not against the cercarial elastases of Schistosoma mansoni, Schistosoma haematobium, Schistosoma japonicum and Trichobilharzia ocellata

Cercarial secretions from different species of the parasite Schistosoma and from Trichobilharzia ocellata contain a proteolytic activity, cercarial elastase, which was demonstrated by a 30 kDa band in gelatin gels. Sera of patients infected with Schistosoma mansoni, Schistosoma haematobium or Schistosoma japonicum contain immunoglobulin G which react in ELISA with cercarial secretions from all schistosomes and cross-react among the different parasite species. In Western blots, however, infection sera from patients, as well as heavily infected mice or rabbits, did not react with a 30-kDa protein. Moreover, when sections from infected snails (Biomphalaria, Bulinus and Lymnaea) were analysed by immunofluorescence using the same infection sera, only the tegument of the developing cercariae was recognized, but not the acetabular glands. In contrast, when antisera against purified cercarial elastase from either S. mansoni or S. haematobium were tested with sections of infected Biomphalaria or Bulinus, fluorescence was strong in the preacetabular glands of the cercariae of either species, but undetectable with the tegument. Cross-reactivity of both antisera extended to T. ocellata-infected Lymnaea, but not to S. japonicum-infected Oncomelania. In conclusion, although immunization with purified cercarial elastase results in antibody production, the enzyme does not induce an apparent antibody response following natural infection.