Inverse relation between disease severity and expression of the streptococcal cysteine protease, SpeB, among clonal M1T1 isolates recovered from invasive group A streptococcal infection cases
Inverse relation between disease severity and expression of the streptococcal cysteine protease, SpeB, among clonal M1T1 isolates recovered from invasive group A streptococcal infection cases
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DOI：
10.1128/iai.68.11.6362-6369.2000
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发表时间：
2000-11-01
影响因子：
3.1
通讯作者：
Kotb, M
中科院分区：
文献类型：
--
作者：
Kansal, RG;McGeer, A;Kotb, M
链球菌半胱氨酸蛋白酶（SpeB）是A群链球菌（GAS）产生的主要毒力因子之一。在这项研究中，我们调查了来自侵袭性感染患者的克隆相关M1T1临床分离株是否存在SpeB产生的差异。其中29株来自非重症病例，48株来自重症病例，包括链球菌中毒性休克综合征（STSS）和坏死性筋膜炎（NF）病例。Western blotting法测定28kda SpeB蛋白的表达量和表达量，荧光酶法测定蛋白酶活性。在分离株中观察到SpeB表达的高度差异，这种差异似乎与侵袭性感染的严重程度和/或临床表现有关。非严重病例分离株产生的28-kDa SpeB蛋白的平均量和半胱氨酸蛋白酶活性显著高于STSS病例（P = 0.001）。造成这种差异的部分原因是，41%的STSS分离株产生很少或不产生SpeB，而在非严重病例中，只有14%的分离株恢复。此外，在那些表达SpeB的分离株中，STSS分离株的半胱氨酸蛋白酶活性显著低于非严重病例分离株（P = 0.001）。SpeB产量的增加也与完整M蛋白的表达呈负相关，抑制半胱氨酸蛋白酶活性可以阻断表面M蛋白的裂解。总之，这些数据支持控制SpeB产生的“开-关”和翻译后调控机制的存在，他们表明，SpeB基因处于“关”状态的分离物更有可能避免表面M蛋白，并且从严重而非非严重侵袭性感染的病例中分离出来。这些发现可能对SpeB通过调节GAS毒力基因的表达和侵袭性疾病的严重程度在宿主-病原体相互作用中的作用具有重要意义。
The streptococcal cysteine protease (SpeB) is one of the major virulence factors produced by group A streptococci (GAS). In this study we investigated if differences exist in SpeB production by clonally related M1T1 clinical isolates derived from patients with invasive infections. Twenty-nine of these isolates were from nonsevere cases and 48 were from severe cases, including streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis (NF) cases. The expression and amount of the 28-kDa SpeB protein produced were determined by quantitative Western blotting, and protease activity was measured by a fluorescent enzymatic assay. A high degree of variation in SpeB expression was seen among the isolates, and this variation seemed to correlate with the severity and/or clinical manifestation of the invasive infection. The mean amount of 28-kDa SpeB protein and cysteine protease activity produced by isolates from nonsevere cases was significantly higher than that from STSS cases (P = 0.001). This difference was partly due to the fact that 41% of STSS isolates produced little or no SpeB compared to only 14% of isolates recovered in nonsevere cases. Moreover, the cysteine protease activity among those isolates that expressed SpeB was significantly lower for STSS isolates than for isolates from nonsevere cases (P = 0.001). Increased SpeB production was also inversely correlated with intact M protein expression, and inhibition of cysteine protease activity blocked the cleavage of the surface M protein. Together, the data support the existence of both an "on-off" and a posttranslational regulatory mechanism(s) controlling SpeB production, and they suggest that isolates with the speB gene in the "off" state are more likely to spare the surface M protein and to be isolated from cases of severe rather than nonsevere invasive infection. These findings may have important implications for the role of SpeB in host-pathogen interactions via regulation of the expression of GAS virulence genes and the severity of invasive disease.