Delivery of heterologous protein antigens via hemolysin or autotransporter systems by an attenuatedlermutant of rabbit enteropathogenicEscherichia coli

• Published in: Vaccine Vol. 24; no. 18; p. 3821
• Main Authors: Zhu, Chengru, Ruiz-Perez, Fernando, Yang, Zhuolu, Mao, Ying, Hackethal, Veronica L, Greco, Karla M, Choy, Wendy, Davis, Katherine, Butterton, Joan R, Boedeker, Edgar C
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Limited 01.05.2006
• Subjects: Bacteriology; E coli; Infections; Inflammatory bowel disease; Plasmids; Proteins; Rabbits; Toxins; Vaccines
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2005.07.024

In this report, we describe the use of an attenuated regulatory mutant of a rabbit enteropathogenicEscherichia coli(rEPEC) as a live vaccine vector to deliver heterologous protein antigens using two dedicated transport systems, aSalmonellaautotransporter and theE. colihemolysin apparatus. We previously reported that an isogeneicler(LEE encoded regulator) mutant of rEPEC O103:H2 is attenuated and immunogenic in rabbits. We first evaluated theSalmonellaautotransporter MisL containing the immunodominant B-cell epitope of the circumsporozoite protein fromPlasmodium falciparum, (NANP)8, fused to the C-terminal translocator domain under the control of the constitutive Tac17 promoter. The rEPEClermutant was able to express and to translocate the (NANP)8passenger peptide to the bacterial surface. We next investigated the delivery of Shiga toxin B subunit (Stx1B) from human enterohemorrhagicE. coliby the rEPEClermutant via the MisL autotransporter or theE. colihemolysin secretion apparatus. The autotransporter and hemolysin plasmids expressed similar levels of Stx1B (30-40ng/ml/OD600). Only 6% of Stx1B was found in the autotransporter supernatants; the rest was cell-associated, with a small fraction of the Stx1B surface-exposed as determined by immunofluorescence. In contrast, 88% of Stx1B was secreted into culture supernatants by the hemolysin secretion system. In an in vivo study, no significant protection was observed in rabbits inoculated with thelermutant harboring the Stx1B-autotransporter plasmid following experimental challenge with RDEC-H19A, the prototype rEPEC containing an Stx-converting phage. In contrast, rabbits inoculated with the rEPEClermutant containing the Stx1B-hemolysin fusion were partially protected from RDEC-H19A infection as demonstrated by decreased weight loss (p<0.008) when compared to rabbits inoculated with the parentlermutant. Our results suggest that attenuated rEPEC are capable of serving as vaccine vectors to express heterologous protein antigens from different cellular locations and deliver these antigens to the intestinal mucosa. With this system, secreted proteins may be more effective than cell-associated antigens in generating protection.