Pretreatment Sublethal B. Anthracis Lethal Toxin in Rats

在体外，B的致死因子组分。炭疽LeTx灭活丝裂原活化蛋白激酶激酶，并抑制响应于LPS和IFNg的TNF α和NO释放。这些抗炎作用是否与B的致病性有关。炭疽病感染尚不清楚。然而，如果它们是，我们假设亚致死剂量的LeTx在致死LPS攻击期间也可能在体内具有抗炎作用。在实验中，在用LPS输注24小时之前3小时，将具有静脉和动脉导管的Sprague-Dawley大鼠随机接受低、中或高亚致死剂量的LeTx或仅稀释剂的注射。在LPS输注期间，测量平均动脉血压（MAP）（q1 h）和血浆细胞因子（IL-1 a和B，IL-2、4、6和10，IFNg，TNF α，GM-CSF，MIP 1、2和3a，以及RANTES）和NO水平（2、8和24 h）。观察动物168 h。与高剂量的LeTx相比，中剂量和低剂量导致生存风险比降低接近显著性（高剂量与低剂量和中剂量组合的p=0.08）。与仅稀释剂相比，LeTx在2 h降低了12种细胞因子中的10种（无显著性），所有13种细胞因子，其中4种显著或接近（IL-6，IL-10，IFNg，MIP 2a，p<=0.08），NO水平从2至24小时显著增加（LeTx随时间的影响p=0.02），MAP在24小时内显著增加（p=0.001）。因此，与体外数据一致，亚致死LeTx降低LPS攻击大鼠中的细胞因子和NO水平。这与血压升高有关，并且在低剂量和中等剂量下，有益的生存趋势。这些相同的抗炎作用与LeTx是否将是有益的，而是在细菌感染过程中损害宿主防御需要进一步研究。研究正在进行中，以调查低亚致死剂量的LeTx在E.大肠杆菌感染。

In vitro the lethal factor component of B. anthracis LeTx inactivated mitogen-activated protein kinase kinases and inhibited TNFa and NO release in response to LPS and IFNg. Whether these anti-inflammatory effects are relevant to the pathogenicity of B. anthracis infection is not known. If they are however, we hypothesized that sublethal doses of LeTx might also have anti-inflammatory effects in vivo during lethal LPS challenge. In experiments, 3 h before a 24 h infusion with LPS, Sprague-Dawley rats with venous and arterial catheters were randomized to receive injections of low, medium or high sublethal doses of LeTx or diluent only. During LPS infusion, mean arterial blood pressure (MAP) (q1h) and plasma cytokines (IL-1a and b, IL-2, 4, 6, and 10, IFNg, TNFa, GM-CSF, MIP1,2 and 3a, and RANTES) and NO levels (2, 8, and 24 h) were measured. Animals were observed for 168 h. Compared to high doses of LeTx, medium and low doses caused decreases in the hazards ratio of survival approaching significance (p=0.08 for high vs low and medium doses combined). Compared to diluent only, LeTx decreased 10 of 12 cytokines at 2 h (none significantly), all 13 cytokines, 4 of them significantly or approaching it (IL-6, IL-10, IFNg, MIP2a,p<=0.08) at 8 h, and NO levels significantly from 2 to 24 h (p=0.02 for the effect of LeTx across time) and increased MAP significantly over the 24 h (p=0.001). Thus, consistent with in vitro data, sublethal LeTx decreased cytokine and NO levels in LPS challenged rats. This was associated with increased blood pressure and, with low and medium doses, beneficial survival trends. Whether these same anti-inflammatory effects with LeTx would be beneficial or instead impair host defense during bacterial infection requires further study. Studies are ongoing to investigate the effects of low sublethal doses of LeTx before E. coli infection in this rat model.