A Foreign Protein Incorporated on the Tip of T3 Pili in Lactococcus lactis Elicits Systemic and Mucosal Immunity

• Type of Material: Article
• Authors: Bernard R. Quigley, Emory University; Matthew Hatkoff, Emory University; David G. Thanassi, Emory University; Mahamoudou Ouattara, Emory University; Zehava Eichenbaum, Emory University; June R Scott, Emory University
• Language: English
• Date: 2010-03
• Publisher: American Society for Microbiology (ASM)
• Publication Version: Final Published Version
• Copyright Statement: © 2010, American Society for Microbiology
• Final Published Version (URL): http://iai.asm.org/content/78/3/1294
• Title of Journal or Parent Work: Infection and Immunity
• Volume: 78
• Issue: 3
• Start Page: 1294
• End Page: 1303
• Grant/Funding Information: This study was funded in part by a grant from the Georgia Research Alliance (J.R.S. and Z.E.) and grants AI055621 and GM062987 (D.G.T.) and AI05605 (J.R.S.) from the National Institutes of Health.
• Research Categories: Biology, Microbiology; Health Sciences, Immunology

Abstract

The use of Lactococcus lactis to deliver a chosen antigen to the mucosal surface has been shown to elicit an immune response in mice and is a possible method of vaccination in humans. The recent discovery on Gram-positive bacteria of pili that are covalently attached to the bacterial surface and the elucidation of the residues linking the major and minor subunits of such pili suggests that the presentation of an antigen on the tip of pili external to the surface of L. lactis might constitute a successful vaccine strategy. As a proof of principle, we have fused a foreign protein (the Escherichia coli maltose-binding protein) to the C-terminal region of the native tip protein (Cpa) of the T3 pilus derived from Streptococcus pyogenes and expressed this fusion protein (MBP*) in L. lactis. We find that MBP* is incorporated into pili in this foreign host, as shown by Western blot analyses of cell wall proteins and by immunogold electron microscopy. Furthermore, since the MBP* on these pili retains its native biological activity, it appears to retain its native structure. Mucosal immunization of mice with this L. lactis strain expressing pilus-linked MBP* results in production of both a systemic and a mucosal response (IgG and IgA antibodies) against the MBP antigen. We suggest that this type of mucosal vaccine delivery system, which we term UPTOP (for unhindered presentation on tips of pili), may provide an inexpensive and stable alternative to current mechanisms of immunization for many serious human pathogens.