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Protective efficacy of the recombinantly expressed C-terminal domain of Mannheimia haemolytica leukotoxin in mice and goats Cover

Protective efficacy of the recombinantly expressed C-terminal domain of Mannheimia haemolytica leukotoxin in mice and goats

Open Access
|Oct 2025

Abstract

Introduction

Bovine respiratory disease (BRD) complex is a leading cause of economic losses in the beef and dairy cattle industries. Mannheimia haemolytica is recognised as the primary pathogen associated with this disease. While antibiotics and vaccines are widely used against it, antimicrobial resistance and limited vaccine efficacy remain obstacles. Mannheimia haemolytica leukotoxin A (LktA) has been identified as a promising candidate for subunit vaccine development against BRD. However, the low expression and biological instability of the full-length LktA complicate its production. This study evaluated the immunogenic potential of the truncated LktA protein for subunit vaccine development.

Material and Methods

Truncated proteins of LktA N-terminal (nLktA) and C-terminal (cLktA) were expressed in E. coli which were small enough for stable expression yet large enough to function as effective immunogens. The immunogenicity of the recombinant truncated LktA proteins was evaluated in mouse and goat models against a phosphate-buffered saline (PBS) negative-control group. Recombinant cLktA was emulsified with oil adjuvant and used to immunise mice and goats.

Results

The cLktA group had significantly higher antibody levels at four weeks post-immunisation (wpi) than the PBS group. In goats, cLktA elicited high antibody responses up to six wpi. A single administration of cLktA conferred 80% and 100% survival against a M. haemolytica challenge.

Conclusion

These findings show the C-terminal region of Mannheimia haemolytica LktA to be a highly immunogenic and protective antigen and suggest its potential as a candidate for subunit vaccine development.

Language: English
Submitted on: Apr 1, 2025
Accepted on: Oct 9, 2025
Published on: Oct 18, 2025
Published by: National Veterinary Research Institute in Pulawy
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year

© 2025 Thu-Dung Doan, Teerajet Laohasatian, Hsing-Chieh Wu, Chun-Yen Chu, published by National Veterinary Research Institute in Pulawy
This work is licensed under the Creative Commons Attribution 4.0 License.

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