Institute of Experimental Medicine, Department of Pharmacology, Videnska 1083, 142 20 Prague 4, Czech Republic.
Nitric Oxide. 2010 Dec 15;23(4):300-10. doi: 10.1016/j.niox.2010.09.001. Epub 2010 Sep 17.
Lipoteichoic acid (LTA) is a structural component of the cell walls of Gram-positive bacteria. Similar to lipopolysaccharide (LPS) which is expressed in Gram-negative bacteria, LTA exhibits immunostimulatory properties. Frequently observed positive response of LTA in the Limulus amebocyte lysate (LAL) assay has been interpreted as a sign of LPS contamination, raising doubts about the intrinsic immune activities of LTA. Regarding many similarities in immunobiological and physicochemical properties of LTA and LPS, we hypothesized that similar to LPS, the LAL reactivity of LTA might be due to its ability to bind to LAL. Our data confirm the positivity of Bacillus subtilis, Staphylococcus aureus, Streptococcus faecalis and Streptococcus pyogenes LTAs in the LAL test. The estimates of suspected LPS content were 605, 10.3, 6.2 and 127 pg/μg LTA, respectively. The effectiveness of LTAs to induce the NO production in rat peritoneal cells was remarkably higher than that of equivalent concentrations of reference LPS (Escherichia coli). The LPS-induced NO was inhibited by polymyxin B (PMX), the IC(50) of PMX:LPS concentration ratio (pg:pg) being 1050:1. Many fold higher concentrations of PMX were needed to partially suppress the NO-augmenting effects of LTAs, applied at concentrations representing the equivalents of LPS. Transposed to the concentrations of LTAs per se, the IC(50)s of the PMX:LTA ratios (μg:μg) ranged from 0.3:1 (S. aureus) to 7.5:1 (B. subtilis). It is concluded that LTA is not necessarily contaminated with LPS. The results prove the intrinsic immunostimulatory properties of LTAs of Gram-positive bacteria. The positive response of LTA in the LAL assay results from its capacity to bind to LAL. In addition, LTA binds with high affinity to PMX.
脂磷壁酸（LTA）是革兰氏阳性菌细胞壁的结构成分。与革兰氏阴性菌中表达的脂多糖（LPS）相似，LTA 具有免疫刺激特性。在鲎变形细胞溶解物（LAL）检测中频繁观察到 LTA 的阳性反应，被解释为 LPS 污染的迹象，这引起了对 LTA 固有免疫活性的怀疑。鉴于 LTA 和 LPS 在免疫生物学和理化性质上有许多相似之处，我们假设与 LPS 相似，LTA 在 LAL 中的反应性可能是由于其与 LAL 结合的能力。我们的数据证实了枯草芽孢杆菌、金黄色葡萄球菌、粪肠球菌和化脓链球菌 LTA 在 LAL 试验中的阳性。疑似 LPS 含量的估计值分别为 605、10.3、6.2 和 127 pg/μg LTA。LTA 诱导大鼠腹腔细胞产生 NO 的效力明显高于等效浓度的参考 LPS（大肠杆菌）。LPS 诱导的 NO 被多粘菌素 B（PMX）抑制，PMX:LPS 浓度比（pg:pg）的 IC50 为 1050:1。需要多倍于 PMX 的浓度才能部分抑制 LTA 的增强 NO 效应，应用浓度代表 LPS 的等效浓度。转化为 LTA 本身的浓度，PMX:LTA 比值（μg:μg）的 IC50 范围从 0.3:1（金黄色葡萄球菌）到 7.5:1（枯草芽孢杆菌）。结论是 LTA 不一定含有 LPS。结果证明了革兰氏阳性菌 LTA 的固有免疫刺激特性。LTA 在 LAL 检测中的阳性反应源自其与 LAL 结合的能力。此外，LTA 与 PMX 具有高亲和力。
