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首页> 外文期刊>Infection and immunity >Role of lgtC in Resistance of Nontypeable Haemophilus influenzae Strain R2866 to Human Serum
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Role of lgtC in Resistance of Nontypeable Haemophilus influenzae Strain R2866 to Human Serum

机译：lgtC在不可分型流感嗜血杆菌R2866株对人血清抗性中的作用

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摘要

We are investigating a nontypeable Haemophilus influenzae (NTHI) strain, R2866, isolated from a child with meningitis. R2866 is unusually resistant to killing by normal human serum. The serum 50% inhibitory concentration (IC50) for this strain is 18%, approaching that of encapsulated H. influenzae. R3392 is a derivative of R2866 that was found to have increased sensitivity to human serum (IC50, 1.5%). Analysis of tetrameric repeat regions within lipooligosaccharide (LOS) biosynthetic genes in both strains indicated that the glycosyltransferase gene lgtC was out of frame (“off”) in most colonies of R3392 but in frame with its start codon (“on”) in most colonies of the parent. We sought antigenic and biochemical evidence for modification of the LOS structure. In a whole-cell enzyme-linked immunosorbent assay, strain R3392 displayed reduced binding of the Galα1,4Gal-specific monoclonal antibody 4C4. Mass spectrometry analysis of LOS from strain R2866 indicated that the primary oligosaccharide glycoform contained four heptose and four hexose residues, while that of R3392 contained four heptose and three hexose residues. We conclude that the R2866 lgtC gene encodes a galactosyltransferase involved in synthesis of the 4C4 epitope, as in other strains, and that expression of lgtC is associated with the high-level serum resistance that has been observed for this strain. This is the first description of the genetic basis of high-level serum resistance in NTHI, as well as the first description of LOS composition in an NTHI strain for which the complete genome sequence has been determined.
机译：我们正在研究从一名脑膜炎患儿分离出的不可分型的流感嗜血杆菌（NTHI）株R2866。 R2866对正常人血清杀伤具有非凡的抵抗力。该菌株的血清50％抑制浓度（IC 50 ）为18％，接近包囊的 H。流感。 R3392是R2866的衍生物，被发现对人血清的敏感性增加（IC 50 ，1.5％）。分析两个菌株中脂寡糖（LOS）生物合成基因内的四聚体重复区域，发现在R3392的大多数菌落中，糖基转移酶基因 lgtC 不在框架内（“ off”），但其起始密码子在框架内（在父母的大多数殖民地中“上”。我们寻求改变LOS结构的抗原和生化证据。在全细胞酶联免疫吸附测定中，菌株R3392显示出Galα1,4Gal特异性单克隆抗体4C4的结合减少。菌株R2866的LOS的质谱分析表明，初级寡糖糖型包含四个庚糖和四个己糖残基，而R3392的寡糖形式包含四个庚糖和三个己糖残基。我们得出的结论是，与其他菌株一样，R2866 lgtC 基因编码参与4C4表位合成的半乳糖基转移酶，并且 lgtC 的表达与高水平血清有关已经观察到该菌株的抗性。这是对NTHI中高水平血清抗性的遗传基础的首次描述，也是对NTHI菌株已确定完整基因组序列的LOS组成的首次描述。

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