Dehydroepiandrosterone increases resistance to experimental infection by Trypanosoma cruzi

Dehydroepiandrosterone (DHEA) enhances immune responses against a wide range of viral, bacterial, and parasitic pathogens. In a previous study, we reported that administration of DHEA significantly decreased the numbers of blood parasites in Trypanosoma cruzi experimental infection. The present study was undertaken to determine the effectiveness of DHEA in reducing the severity of acute phase T. cruzi infection of male and female Wistar rats. Animals were treated subcutaneously with 40 mg/kg body weight/day of DHEA. The concentration of nitric oxide (NO) was determined in spleen peritoneal cavity. Interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) were determined in the sera of uninfected and infected animals. DHEA treatment augments NO production for both sexes after in vitro LPS treatment for uninfected animals. Infection triggered enhanced NO levels although not significant. IL-2 and IFN-gamma were detectable in higher concentrations in treated and infected rats of both genders when compared to untreated controls. These data suggest that DHEA may have a potent immunoregulatory function that can affect the course of T. cruzi infection.     

Large granular lymphocytosis in a cynomolgus macaque (Macaca fascicularis) with a subclinical Trypanosoma cruzi infection

A 5.25-year-old cynomolgus macaque (Macaca fascicularis) was found to have a marked leukocytosis due to a lymphocytosis on routine quarantine laboratory data prior to inclusion in a preclinical research study. The majority of lymphocytes were characterized as intermediate to large with round to convoluted nuclei, coarse to clumped chromatin, rare prominent nucleoli, and moderate amounts of lightly basophilic cytoplasm that frequently contained small magenta granules and/or clear vacuoles. The animal had tested negative for several viruses and other etiologic agents found in nonhuman primates 1 week prior to shipment to the research facility. However, further evaluation of the blood smear revealed rare hemoflagellates, and later testing using real-time PCR and ELISA was confirmatory for Trypanosoma cruzi (T cruzi). Trypanosoma cruzi is a zoonotic pathogen responsible for Chagas disease in people and can have negative consequences on study results when positive animals are inadvertently used for preclinical research. This case report describes a marked large granular lymphocytosis in an otherwise healthy macaque as the only indication of infection with T cruzi in an animal believed to be negative for the infection. Additionally, it highlights the diagnostic limitations of screening tests to rule out diseases in animals intended to be used in preclinical studies.     

Effect of zinc supplementation in pregnant mice during experimental Trypanosoma cruzi infection

Zinc is an essential micronutrient and has significant effects on human growth, development, and immune function. Zinc supplementation or deficiency may affect the course of infection. Zinc enhances immune response against a wide range of viral, bacterial, and parasitic pathogens. In the present study, we investigated the effects of zinc sulphate (ZnSO₄) supplementation (20 mg/kg/day) during pregnancy in mice, Swiss Webster strain infected by the Y strain of Trypanosoma cruzi. Oral supplementation of zinc sulphate in pregnant and non-pregnant infected animals did not affect the count of blood parasites as well as tissue parasitism in the heart, liver, and spleen. Zinc supplementation did not alter female body weight, the length of fetuses and neonates, placental size/weight and mortality rate. Among zinc supplied animals, no significant plasmatic zinc concentrations were observed. Concerning to tissue zinc concentrations, only the liver displayed enhanced values as compared to other organs. For placental parasitism, zinc supplied group displayed a significant decrease in amastigote burdens (P < 0.05). However due to the reduced number of parasite burdens in placenta of animals supplied with zinc, these data suggest that zinc was partially effective in up-regulating the host’s immune response against parasite, probably attenuating the infection in fetuses.     

Myeloid differentiation factor 88 is required for resistance to Neospora caninum infection

Neospora caninum is an intracellular parasite that causes major economic impact on cattle raising farms, and infects a wide range of warm-blooded hosts worldwide. Innate immune mechanisms that lead to protection against this parasite are still unknown. In order to investigate whether myeloid differentiation factor 88 (MyD88) is required for resistance against N. caninum, genetically deficient mice (MyD88^−/−) and wild type littermates were infected with live tachyzoites and the resistance to infection was evaluated. We found that sub-lethal tachyzoite doses induced acute mortality of MyD88^−/− mice, which succumbed to infection due to uncontrolled parasite replication. Higher parasitism in MyD88^−/− mice was associated with the lack of IL-12 production by dendritic cells, delayed IFN-γ responses by NKT, CD4⁺ and CD8⁺ T lymphocytes, and production of high levels of IL-10. MyD88^−/− mice replenished with IL-12 and IFN-γ abolished susceptibility as the animals survived throughout the experimental period. We conclude that protective IFN-γ-mediated immunity to N. caninum is dependent on initial MyD88 signaling, in a mechanism triggered by production of IL-12 by dendritic cells. Further knowledge on Toll-like receptor recognition of N. caninum antigens is encouraged, since it could generate new prophylactic and therapeutic tools to control parasite burden.     

Failure of acid secretion during infection of the ovine abomasum by the nematode parasite Teladorsagia circumcincta

Elevation of the abomasal pH of ruminants is a well known consequence of nematode parasitism. Many have argued that the nematodes seek to increase pH to promote their survival. Indeed, there is limited evidence that substances released by the parasites are capable of directly influencing parietal cell activity. In one experimental series, excretions/secretions (ES) of Teladorsagia circumcincta reduced the apparent activity of rabbit gastric glands. Worm ES were shown to contain ammonia, probably accounting for the observed activity, and the effects of ES/ammonia are almost certainly an in-vitro phenomenon only. An alternative hypothesis contends that the loss of acid secretion arises as a consequence of the profound host response elicited by the presence of the parasites. Invariably, presence of parasites is accompanied by an inflammatory response in which eosinophils are conspicuous. Recent research has shown that exudates from inflamed tissues were also inhibitory to gastric gland activity and that during infection, expression of the pro-inflammatory cytokine interleukin 1-beta, the most potent known inhibitor of acid secretion by parietal cells, was increased. Further, the elevation of abomasal pH may prove to have adverse effects on the ability of the parasites to maintain their position within the abomasum.     

外源过氧化氢提高燕麦耐盐性的生理机制

以燕麦品种‘定莜6号’为材料,采用水培法,研究喷施过氧化氢(H₂O₂)对盐胁迫下燕麦幼苗生长、渗透调节物质积累和活性氧代谢的影响。结果表明:1)150 mmol/L NaCl胁迫显著抑制燕麦幼苗生长,提高叶片游离氨基酸和脯氨酸水平,降低谷胱甘肽(GSH)和可溶性糖含量;喷施0.01 mmol/L H₂O₂对NaCl胁迫引起的生长抑制有明显的缓解作用,并提高了幼苗叶片可溶性蛋白质、可溶性糖和脯氨酸含量,降低了游离氨基酸含量。2)NaCl胁迫下,虽然燕麦叶片超氧化物歧化酶、过氧化氢酶、过氧化物酶和抗坏血酸过氧化物酶活性提高,但O2·-、H₂O₂和丙二醛(MDA)积累;喷施H₂O₂进一步提高了NaCl胁迫下燕麦的上述抗氧化酶活性和GSH含量,却降低了O2·-产生速率及H₂O₂和MDA含量,说明外施H₂O₂能够增强盐胁迫燕麦的抗氧化能力,减轻氧化伤害。以上结果表明,外源H₂O₂可通过调控渗透调节物质积累和活性氧代谢提高燕麦耐盐性。     

猪圆环病毒2型感染对猪瘟疫苗体液免疫应答的影响

采用ELISA方法对单独接种猪瘟疫苗组(CSFV组,n=3)、PCV2感染且出现病毒血症后接种猪瘟疫苗组(PCV2/CSFV组,n=3)及PCV2感染同时接种猪瘟疫苗组(CSFV/PCV2组,n=3)不同时相血清中的猪瘟抗体进行检测;并对PCV2感染对照组(PCV2组)及PCV2/CSFV和CSFV/PCV2组血清中PCV2特异的抗体和核酸分别进行ELISA和PCR检测.结果表明,在接种后52 d CSFV组血清中抗体的阻断值显著高于CSFV/PCV2组(P<0.05);接种后42 d和52 d CSFV组平均抗体效价明显高于PCV2/CSFV和CSFV/PCV2组,其中在52 d CSFV组抗体阳性率这100%(3/3)而PCV2/CSFV和CSFV/PCV2在相应时相抗体阳性率仅为67%(2/3).结果提示PCV2感染可在一定程度上抑制猪瘟疫苗特异性的抗体反应.     

抗猪繁殖与呼吸综合征病毒转基因细胞系的建立

采用脂质体法将具有抑制猪繁殖与呼吸综合征病毒(PRRSV)复制的shRNA质粒pEGFP-N1-shRNA导入PK-15细胞中,经G418药物筛选后,分离扩增绿色荧光蛋白阳性细胞,获得抗PRRSV转基因PK细胞系。通过对转染方法和条件的优化,确立最佳的转染及筛选步骤;对得到的阳性转基因细胞进行冷冻-解冻,并作PCR检测。结果表明,G418最佳筛选浓度为600μg/mL,脂质体与质粒的最佳转染比例为7∶2,最佳转染时间为24 h。本研究成功建立抗PRRSV转基因细胞系,为进一步的功能验证及体细胞核移植奠定了基础。     

黄腐酸改善连作马铃薯生长发育及抗性生理的研究

研究了黄腐酸对连作马铃薯幼苗生长发育、块茎营养和抗性生理的影响。结果表明,连作马铃薯幼苗生长发育受到显著抑制,而黄腐酸处理对连作马铃薯的生长发育表现出显著的促进作用;黄腐酸处理相对提高了马铃薯块茎的淀粉含量、Vc含量和可溶性蛋白含量;黄腐酸处理显著减小了连作引起的叶片叶绿素、脯氨酸和可溶性糖含量下降的幅度,相对提高了SOD和CAT活性,并降低了MDA含量和活性氧水平。黄腐酸处理减轻了连作所造成的生理障碍,从而提高了马铃薯幼苗对连作障碍的整体抗性,促进了连作马铃薯的生长发育,改善了马铃薯块茎营养。     

栀子四黄散抗猪繁殖与呼吸综合征的研究

为探索栀子四黄散对猪繁殖与呼吸综合征（porcine reproductive and respiratory syndrome,PRRS）的治疗效果,本研究将45头组随机分为对照组、病毒组及中药高、中、低剂量组5组,每味中药400目超微粉碎后分别添加饲喂接种猪繁殖与呼吸综合征病毒（porcine reproductive and respiratory syndrome virus,PRRSV）的试验猪,连续饲喂14 d,每日观察临床症状,7、14和21 d时随机采集5组血清样品进行细胞因子检测,并进行病理剖检和采集肺脏样品进行病理组织切片观察。结果显示,添加中药7 d后临床症状均减轻,中剂量和高剂量组第14天时体温恢复正常,呼吸困难症状消失,食欲恢复,中药治疗组肺脏未见肉样变,肺脏表面有出血点或出血斑。中剂量组肺泡间隔增厚,轻度淤血,肺实质轻度炎性细胞浸润。病毒组猪血清中IgG和γ-干扰素（IFN-γ）含量逐渐降低,白介素-10（IL-10）含量逐渐上升。添加中药的3组血清中IgG含量均高于病毒组,并且IgG含量均随时间延长逐渐上升,中剂量组血清中IgG含量均极显著高于对照组和病毒组（P<0.01）;添加中药的3组IFN-γ含量逐渐上升,14和21 d时中剂量组血清中IFN-γ含量均极显著高于对照组和病毒组（P<0.01）;中剂量组血清中IL-10含量逐渐降低,14和21 d时与病毒组差异极显著（P<0.01）,与对照组差异不显著（P>0.05）。综上,栀子四黄散可有效改善试验猪临床症状、病理变化和细胞因子的分泌,中剂量组效果最好。本研究为中药防治PRRS提供了试验依据。