Evolutionary and functional analyses of variants of the toxin-coregulated pilus protein TcpA from toxigenic Vibrio cholerae nonO1/non-O139 serogroup isolates
Evolutionary and functional analyses of variants of the toxin-coregulated pilus protein TcpA from toxigenic Vibrio cholerae nonO1/non-O139 serogroup isolates
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DOI：
10.1099/00221287-148-6-1655
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发表时间：
2002-06-01
期刊：
影响因子：
2.8
通讯作者：
Waldor, MK
中科院分区：
文献类型：
--
作者：
Boyd, EF;Waldor, MK
毒素协同调节菌毛（TCP）是霍乱弧菌致病性的关键决定因素。这种束状的菌毛是一种重要的肠道定植因子，也是编码霍乱毒素（CT）的丝状噬菌体CTXphi的受体。TCP是一种由主要肽蛋白TcpA重复亚基组成的聚合物，而TcpA存在于弧菌致病性岛（Vibrio pathogenicity island， VPI）中。本研究对霍乱弧菌产毒分离株tcpA位点的遗传变异进行了研究，并从分别属于0141、037和08血清群的霍乱弧菌V46、V52和V54株中鉴定出3个新的tcpA序列。这些新的tcpA等位基因分为三个不同的克隆谱系。TcpA的多态性主要位于TCP纤维表面暴露区域的TcpA的羧基区。将霍乱弧菌分离株tcpA位点与VPI内另一个位点aldA和染色体位点mdh的遗传多样性进行比较，发现tcpA序列的多样性远高于其他位点。最有可能的是，这种多样性反映了适应宿主免疫反应或CTXphi易感性的多样化选择。通过分析非01霍乱弧菌菌株是否能被CTXphi感染并在乳鼠中定植，对tcpA变异序列的功能特性进行了评价。与霍乱弧菌01的El - Tor菌株类似，这些菌株的体外CTXphi感染需要外源表达toxT，这表明在这些菌株中，toxT调节TCP的表达，这些TcpA变体可以作为CTXphi受体。所有非01血清组霍乱弧菌分离株均能在乳鼠小肠定植，提示不同的TcpA变异可能是定植因子。
The toxin-coregulated pilus (TCP) is a critical determinant of the pathogenicity of Vibrio cholerae. This bundle-forming pilus is an essential intestinal colonization factor and also serves as a receptor for CTXphi, the filamentous phage that encodes cholera toxin (CT). TCP is a polymer of repeating subunits of the major pilin protein TcpA and tcpA is found within the Vibrio pathogenicity island (VPI). In this study genetic variation at the tcpA locus in toxigenic isolates of V. cholerae was investigated and three novel TcpA sequences from V. cholerae strains V46, V52 and V54, belonging to serogroups 0141, 037 and 08, respectively, were identified. These novel tcpA alleles grouped into three distinct clonal lineages. The polymorphisms in TcpA were predominantly located in the carboxyl region of TcpA in surface-exposed regions of TCP fibres. Comparison of the genetic diversity among V. cholerae isolates at the tcpA locus with that of aldA, another locus within the VPI, and mdh, a chromosomal locus, revealed that tcpA sequences are far more diverse than these other loci. Most likely, this diversity is a reflection of diversifying selection in adaptation to the host immune response or to CTXphi susceptibility. An assessment of the functional properties of the variant tcpA sequences in the non-01 V. cholerae strains was carried out by analysing whether these strains could be infected by CTXphi and colonize the suckling mouse. Similar to El Tor strains of V. cholerae 01, in vitro CTXphi infection of these strains required the exogenous expression of toxT, suggesting that in these strains ToxT regulates TCP expression and that these TcpA variants can serve as CTXphi receptors. All the V. cholerae non-01 serogroup isolates tested were capable of colonizing the suckling mouse small intestine, suggesting that the different TcpA variants could function as colonization factors.