Surface display of heterologous proteins in bacteria has been employed as a tool for fundamental and applied research in microbiology, molecular biology, immunology and biotechnology (36). The most common application is the development of live-bacterialvaccine. A good induction of antigen-specific immune response was generally observed after immunization by live recombinant cells displaying heterologous antigenic determinant (16, 25, 37, 41). Among all outer cell surface proteins, flagellin, the major subunit of flagella, presents numerous advantages for the immune system function. Flagellin proteins are present only in the prokaryotic kingdom. Each flagellum contains a filament composed of 20,000 flagellin molecules (40), and Enterobacteria have three to eight filaments on the bacterial surface (1). The central surface-exposed region of flagellin (29) is not necessary for function (15) and can be easily exchanged with foreign peptides (25). Eubacterial flagellins contain conserved sequences in the amino and carboxy ends of the protein allowing the assembly of the flagella (38). Recently, these sequences have been shown to belong to a group of molecular patterns, the PAMPs (Pathogenes Associated Molecular Patterns), recognized by eukaryotic PRRs (Pattern-Recognition Receptors) cell receptors implicated in animal innate immune response against bacteria, viruses and yeast. The receptor for the flagellin (TLR5) belongs to the Toll-like receptor (TLR) family (12). Additionally, McSorley et al. (21) presented evi