Serum resistance in Haemophilus ducreyi requires outer membrane protein DsrA
Serum resistance in Haemophilus ducreyi requires outer membrane protein DsrA
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DOI：
10.1128/iai.68.3.1608-1619.2000
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发表时间：
2000-03-01
影响因子：
3.1
通讯作者：
Olsen, B
中科院分区：
文献类型：
--
作者：
Elkins, C;Morrow, KJ;Olsen, B
杜氏嗜血杆菌能抵抗正常血清抗体和补体的杀伤作用。我们发现了一种表达血清耐药所需的杜氏杆菌外膜蛋白，并将其命名为DSRA(“杜氏血清耐药A”)。对DsrA基因座进行克隆、测序和诱变，构建了亲本菌株35000的等位基因突变株FX517，并对其进行了鉴定，发现该突变株不再表达DsrA基因。FX517的血清易感性至少是35000的10倍。除3株自然产生、无毒、血清敏感的杜氏嗜血杆菌外，所有供试的杜氏嗜血杆菌都表达DSRA。FX517和三株自然产生的DSRA非表达菌株被一个表达DSRA的质粒在反式中互补。所有四株都转化为抗血清表型，其中两株含有截短型脂寡糖(LOS)。因此，杜氏嗜血杆菌的血清耐药性不需要表达全长LOS，但需要表达DSRA。对另外8株杜氏嗜血杆菌的DSRA基因座进行了测序，推导的氨基酸序列有85%以上的同源性。DSRA蛋白之间的主要差异是由于存在一个、两个或三个拷贝的七聚体氨基酸重复NTHNINK。这些重复序列解释了在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳中观察到的DSRA单体形式(28至35 kDa)的表观分子质量的变化。由于DSRA存在于强毒株中，高度保守，是血清耐药所必需的，我们推测它可能是一个毒力因子和潜在的候选疫苗。
Haemophilus ducreyi is resistant to killing by normal serum antibody and complement. We discovered an H. ducreyi outer membrane protein required for expression of serum resistance and termed it DsrA (for "ducreyi serum resistance A"). The dsrA locus was cloned, sequenced, and mutagenized, An isogenic mutant (FX517) of parent strain 35000 was constructed and characterized, and it was found to no longer express dsrA. FX517 was at least 10-fold more serum susceptible than 35000. DsrA was expressed by all strains of H. ducreyi tested, except three naturally occurring, avirulent, serum-sensitive strains. FX517 and the three naturally occurring dsrA-nonexpressing strains were complemented in trans with a plasmid expressing dsrA. All four strains were converted to a serum-resistant phenotype, including two that contained truncated lipooligosaccharide (LOS). Therefore, serum resistance in H. ducreyi does not require expression of full-length LOS but does require expression of dsrA. The dsrA locus from eight additional H. ducreyi strains was sequenced, and the deduced amino acid sequences were more than 85% identical. The major difference between the DsrA proteins was due to the presence of one, two, or three copies of the heptameric amino acid repeat NTHNINK. These repeats account for the variability in apparent molecular mass of the monomeric form of DsrA (28 to 35 kDa) observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Since DsrA is present in virulent strains, is highly conserved, and is required for serum resistance, we speculate that it may be a virulence factor and a potential vaccine candidate.