Mancuso G, Tomasello F, von Hunolstein C, Orefici G, Teti G
Istituto di Microbiologia, Facoltà di Medicina e Chirurgia, Università degli Studi di Messina, Italy.
Infect Immun. 1994 Jul;62(7):2748-53. doi: 10.1128/iai.62.7.2748-2753.1994.
Previous studies suggested that circulating tumor necrosis factor alpha (TNF-alpha) may have a pathophysiologic role in experimental neonatal sepsis induced by group B streptococci (GBS). This study was undertaken to investigate the ability of the type III and group-specific polysaccharides of GBS to induce TNF-alpha production and TNF-alpha-dependent lethality in neonatal rats. The cytokine was detected in plasma samples by the L929 cytotoxicity assay. Intracardiac injections of either polysaccharide induced dose-dependent, transient elevations in plasma TNF-alpha levels that returned to baseline values after 5 h. The group-specific antigen induced significantly higher mean peak TNF-alpha levels than the type III antigen (125 +/- 47 versus 44 +/- 15 U/ml with 70 mg/kg of body weight). Glycogen (70 mg/kg), used as a negative control, did not induce TNF-alpha. The lipopolysaccharide-neutralizing agent polymyxin B did not decrease TNF-alpha levels induced by either polysaccharide, ruling out contamination with endotoxin as a possible cause of TNF-alpha induction. Fifty percent lethal doses of the type III and group-specific antigens given as intracardiac injections were 105 and 16 mg/kg, respectively. Salmonella endotoxin, used as a positive control, had a 50% lethal dose of 0.1 mg/kg. The lethal activities of GBS polysaccharides, as well as endotoxin, were completely prevented by pretreatment of neonatal rats with the respective specific antibodies or anti-murine TNF-alpha serum. To assess the relative importance of the type-specific substance in TNF-alpha induction by whole bacteria, two unrelated GBS transposon mutants devoid of only the type-specific capsular polysaccharide (COH1-13 and COH31-15) were employed. Each of the heat-killed unencapsulated mutants was able to produce plasma TNF-alpha level elevations or TNF-alpha-dependent lethality but was significantly less efficient in these activities than the corresponding encapsulated wild-type strain. These data suggest that the presence of type-specific material on GBS is not necessary for the stimulation of TNF-alpha production. Type III capsular polysaccharide, however, can significantly increase the ability of GBS to induce TNF-alpha. Further studies will be needed to assess the importance of TNF-alpha induction by the group- and type-specific antigens in the pathophysiology of GBS disease.
先前的研究表明，循环肿瘤坏死因子α（TNF-α）可能在B族链球菌（GBS）诱导的实验性新生儿败血症中发挥病理生理作用。本研究旨在探讨GBS的III型和群特异性多糖诱导新生大鼠产生TNF-α以及TNF-α依赖性致死率的能力。通过L929细胞毒性试验检测血浆样本中的细胞因子。心内注射任何一种多糖均可诱导血浆TNF-α水平呈剂量依赖性短暂升高，5小时后恢复至基线值。群特异性抗原诱导的平均TNF-α峰值水平显著高于III型抗原（体重70mg/kg时分别为125±47和44±15U/ml）。用作阴性对照的糖原（70mg/kg）未诱导TNF-α产生。脂多糖中和剂多粘菌素B并未降低任何一种多糖诱导的TNF-α水平，排除了内毒素污染作为TNF-α诱导可能原因的可能性。心内注射的III型和群特异性抗原的半数致死剂量分别为105mg/kg和16mg/kg。用作阳性对照的沙门氏菌内毒素的半数致死剂量为0.1mg/kg。用相应的特异性抗体或抗小鼠TNF-α血清预处理新生大鼠可完全预防GBS多糖以及内毒素的致死活性。为评估全菌诱导TNF-α产生时型特异性物质的相对重要性，使用了两种仅缺失型特异性荚膜多糖的不相关GBS转座子突变体（COH1-13和COH31-15）。每种热灭活的无荚膜突变体均能够使血浆TNF-α水平升高或产生TNF-α依赖性致死率，但在这些活性方面明显低于相应的有荚膜野生型菌株。这些数据表明，GBS上型特异性物质的存在并非刺激TNF-α产生所必需。然而，III型荚膜多糖可显著增强GBS诱导TNF-α的能力。需要进一步研究以评估群特异性和型特异性抗原诱导TNF-α在GBS疾病病理生理学中的重要性。
