**Construction and Characteristics of a Recombinant Single-Chain Antibody Fragment against Bacterial Type III Secretion Single-Chain Antibody Fragment against Bacterial Type III Secretion**

**Construction and Characteristics of a Recombinant** 

DOI: 10.5772/intechopen.70316

Teiji Sawa, Atsushi Kainuma, Kiyoshi Moriyama and Yoshifumi Naito and Yoshifumi Naito Additional information is available at the end of the chapter

Teiji Sawa, Atsushi Kainuma, Kiyoshi Moriyama

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.70316

#### **Abstract**

*Pseudomonas aeruginosa*, a Gram-negative pathogen, causes life-threatening infections. Lung injury and the development of sepsis depend largely on expression of the virulence genes associated with the type III secretion system of this bacterium. The type III secretion system functions as a molecular syringe to deliver type III secretory toxins directly into the cytosol of eukaryotic cells and also acts to inhibit innate immune mechanisms, thereby preventing bacterial clearance. Antibodies against PcrV, the cap structure in the translocational needle of type III secretory apparatus of *P. aeruginosa*, block toxin translocation of the type III secretion system. We have been investigating the therapeutic use of a recombinant anti-PcrV single-chain antibody. In this chapter, as a preliminary step toward an antibody-based immunotherapy against bacterial infections, we summarize our experience of constructing a recombinant single-chain antibody (called scFv166), in which the heavy (VH) and light chain (VL) variable regions of the anti-PcrV monoclonal IgG are joined by a flexible peptide linker. The practical methodologies used to make recombinant scFv166 against a bacterial protein component are described in detail.

**Keywords:** single-chain antibody, PcrV, *Pseudomonas aeruginosa*, type III secretion system
