Development of Safe and Non-Self-Immunogenic Mucosal Adjuvant by Recombinant Fusion of Cholera Toxin A1 Subunit with Protein Transduction Domain.

Eunji Yang,Eugene Lee,Jae-Ouk Kim,Man Ki Song,June Young Chun,Sung-Moo Park,Youngjoo Choi,Dae-Im Jung,Cecil Czerkinsky,Byoung-Shik Shim,In Su Cheon,Jung-ah Choi,Cheol-Heui Yun

doi:10.1155/2018/9830701

Abstract

Potential use of cholera toxin (CT) as a mucosal vaccine adjuvant has been documented in a variety of animal models. However, native CT is highly toxic to be used as a mucosal adjuvant in humans. Here, we demonstrate a new approach to generate a mucosal adjuvant by replacing the B subunit of CT with HIV-1 Tat protein transduction domain (PTD), which efficiently delivers fusion proteins into the cell cytoplasm by unspecific binding to cell surface. We compared the adjuvanticity and toxicity of Tat PTD-CTA1-Tat PTD (TCTA1T) with those of CT. Our results indicate that intranasal (i.n.) delivery of ovalbumin (OVA) with TCTA1T significantly augments the OVA-specific systemic and mucosal antibody responses to levels comparable to those seen with CT adjuvant. Moreover, in vivo cytotoxic T lymphocyte activity elicited by TCTA1T was significantly higher than that elicited by a mutant TCTA1T (TmCTA1T) lacking ADP-ribosyltransferase function. In addition, coadministration of influenza M2 protein with TCTA1T conferred near complete protection against lethal influenza virus challenge. Importantly, TCTA1T, in contrast to CT, did not induce serum IgG antibody responses to itself and was shown to be nontoxic. These results suggest that TCTA1T may be a safe and effective adjuvant when given by mucosal routes.

Highlights

Mucosal surfaces function as a barrier between the host interior and the external environment [1]
The polymerase chain reaction (PCR) product was digested with Xho I and BamH I and ligated to the pET15bTat-GFP-Tat plasmid which was linearized with the same enzymes, resulting in the recombinant plasmid pET15bTCTA1T
We constructed our candidate adjuvant Tat PTD-CTA1-Tat PTD (TCTA1T) by fusing HIV-1 Tat protein transduction domain (PTD) onto both N-terminus and C-terminus of CTA1 subunit, which allowed bypassing of CTBdependent cellular internalization of CTA1 (Figure 1(a))

Summary

Introduction

Mucosal surfaces function as a barrier between the host interior and the external environment [1]. Only few mucosal vaccines have been licensed for human use and no mucosal adjuvant has yet been approved [2, 5] Despite their obvious advantages, the evident challenge faced by many candidate mucosal vaccines has been their inability to elicit adequate immune responses when administered via mucosal routes [6, 7]. The evident challenge faced by many candidate mucosal vaccines has been their inability to elicit adequate immune responses when administered via mucosal routes [6, 7] Such a challenge indicates that these candidate vaccines may require the use of Journal of Immunology Research proper adjuvant to efficiently generate immune responses that can offer protection against invading pathogens

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