Pichel M, Binsztein N, Viboud G
Departamento de Bacteriología, Instituto Nacional de Enfermedades Infecciosas-ANLIS "Carlos G. Malbrán," 1281 Capital Federal, Argentina.
Infect Immun. 2000 Jun;68(6):3280-5. doi: 10.1128/IAI.68.6.3280-3285.2000.
Enterotoxigenic Escherichia coli (ETEC) expresses a broad spectrum of O:H antigens. Serogroup O20 is one of the most prevalent among the ETEC strains lacking any of the defined colonization factors (CFs), in Argentina. An O20:H- strain, ARG-3, adhered to Caco-2 cells and exhibited a thermoregulated 15.7-kDa protein band upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). An antiserum against this protein inhibited ARG-3 adhesion to Caco-2 cells and bound to very thin fibrilla-like structures on the bacterial surface. A 15.7-kDa protein-defective mutant failed to adhere to Caco-2 cells and lacked immunogold-labeled surface structures. The N-terminal amino acid sequence of the structural subunit showed 95% homology to that of CS15 of ETEC (former antigen 8786) and 65% homology with fimbria SEF14 of Salmonella enterica serovar Enteritidis. Nevertheless, the molecular size of ARG-3 adhesin was different from that of CS15, as revealed by SDS-PAGE and mass spectrometry. Both proteins are immunologically related, yet not identical, since an antiserum against the 15.7-kDa protein reacted solely with ARG-3 after absorption with bacteria bearing CS15. Moreover, only under low stringency conditions could DNA from strain ARG-3 be amplified by PCR using primers derived from the nfaA sequence of CS15. Thus, from the DNA sequence obtained from the ARG-3 PCR product, it could be deduced that the subunit protein differed in 30 residues from that of CS15. ARG-3 adhesin was found in 60% of the O20:H- CF-negative ETEC strains from Argentina; however, it appeared restricted to this serotype. We propose the designation CS22 for the herein identified nonfimbrial adhesin of human ETEC.
产肠毒素大肠杆菌（ETEC）表达多种O:H抗原。在阿根廷，O20血清型是缺乏任何已确定定植因子（CFs）的ETEC菌株中最常见的血清型之一。一株O20:H-菌株ARG-3能黏附于Caco-2细胞，在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）上呈现一条温度调节的15.7 kDa蛋白条带。针对该蛋白的抗血清可抑制ARG-3对Caco-2细胞的黏附，并与细菌表面非常细的纤维状结构结合。一个15.7 kDa蛋白缺陷型突变体无法黏附于Caco-2细胞，且缺乏免疫金标记的表面结构。该结构亚基的N端氨基酸序列与ETEC的CS15（原抗原8786）有95%的同源性，与肠炎沙门氏菌肠炎血清型的菌毛SEF14有65%的同源性。然而，SDS-PAGE和质谱分析显示，ARG-3黏附素的分子大小与CS15不同。这两种蛋白在免疫上相关，但并不相同，因为针对15.7 kDa蛋白的抗血清在用携带CS15的细菌吸收后仅与ARG-3发生反应。此外，只有在低严谨条件下，使用源自CS15的nfaA序列的引物通过PCR才能扩增ARG-3菌株的DNA。因此，从ARG-3 PCR产物获得的DNA序列可以推断，该亚基蛋白与CS15的亚基蛋白在30个残基上不同。在来自阿根廷的60%的O20:H- CF阴性ETEC菌株中发现了ARG-3黏附素；然而，它似乎仅限于这种血清型。我们建议将本文鉴定的人ETEC非菌毛黏附素命名为CS22。
