Recombinant lactococcal-based oral vaccine for protection against Streptococcus agalactiae infections in tilapia (Oreochromis niloticus)

Kuan Yee Wong; Megat Hamzah Megat Mazhar Khair; Adelene Ai Lian Song; Mas Jaffri Masarudin; Jiun Yan Loh; Chou Min Chong; John Beardall; Michelle Yee Mun Teo; Lionel Lian Aun In

doi:10.1016/j.fsi.2024.109572

Recombinant lactococcal-based oral vaccine for protection against Streptococcus agalactiae infections in tilapia (Oreochromis niloticus)

Fish Shellfish Immunol. 2024 Apr 16:149:109572. doi: 10.1016/j.fsi.2024.109572. Online ahead of print.

Authors

Kuan Yee Wong¹, Megat Hamzah Megat Mazhar Khair², Adelene Ai Lian Song³, Mas Jaffri Masarudin⁴, Jiun Yan Loh⁵, Chou Min Chong⁶, John Beardall⁷, Michelle Yee Mun Teo¹, Lionel Lian Aun In⁸

Affiliations

¹ Department of Biotechnology, Faculty of Applied Sciences, UCSI University, Kuala Lumpur, Malaysia.
² Department of Microbiology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Selangor, Malaysia.
³ Department of Microbiology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Selangor, Malaysia; Institute of Bioscience, Universiti Putra Malaysia, Selangor, Malaysia.
⁴ Department of Cell and Molecular Biology, Faculty of Biotechnology and Biomolecular Sciences, University Putra Malaysia, Selangor, Malaysia; Nanomaterials Synthesis and Characterisation Laboratory, Institute of Nanoscience and Nanotechnology, Universiti Putra Malaysia, Selangor, Malaysia.
⁵ Tropical Futures Institute (TFI), James Cook University Singapore, 149 Sims Drive, 387380, Singapore.
⁶ Laboratory of Sustainable Aquaculture (AquaLab), International Institute of Aquaculture and Aquatic Sciences (I-AQUAS), Universiti Putra Malaysia, Port Dickson, Negeri Sembilan, Malaysia.
⁷ School of Biological Sciences, Monash University, Clayton, Australia.
⁸ Department of Biotechnology, Faculty of Applied Sciences, UCSI University, Kuala Lumpur, Malaysia. Electronic address: lionelin@ucsiuniversity.edu.my.

PMID: 38636739
DOI: 10.1016/j.fsi.2024.109572

Abstract

Streptococcosis outbreaks caused by Streptococcus agalactiae infection in tilapia aquaculture have been consistently reported and associated with high mortality and morbidity leading to significant economic losses. Existing vaccine candidates against Streptococcus spp. are designed for intraperitoneal injections that are not practical and labor-intensive which have prompted farmers to protect aquatic animals with antibiotics, thus encouraging the emergence of multidrug resistant bacteria. In this study, a live recombinant L. lactis vaccine expressing a 1403 bp surface immunogenic protein (SIP) and a 1100 bp truncated SIP (tSIP) gene was developed and evaluated against S. agalactiae infection in tilapia. Both SIP and tSIP sequences were cloned and transformed into L. lactis. The recombinant L.lactis vaccine was orally administered to juvenile tilapia for a month. Detection of SIP-specific serum IgM in vaccinated groups compared to control groups indicated that recombinant proteins expressed from L. lactis could elicit immunogenic reactions in tilapia. Fish immunized with the tSIP vaccine also showed the highest level of protection compared to other test groups, and the mortality rate was significantly reduced compared to both control groups. The relative percentage of survival (RPS) against S. agalactiae for both SIP and tSIP-vaccinated groups was 50 % and 89 %, respectively, at 14 days post-challenge. Significant up-regulation of IgM, IL-1β, IL-10, TNF-α and IFN-γ were observed at day 34 between the vaccinated and control groups. These results indicated that the recombinant lactococcal tSIP vaccine can elicit both cell-mediated and humoral responses and is recommended as a potential oral vaccine against S. agalactiae infection. Future work will include further in vivo challenge assessments of this vaccine candidate fused with adjuvants to boost immunogenicity levels in tilapia.

Keywords: Antibiotic resistance; Lactococcus lactis; Orally administered vaccine; Streptococcus agalactiae; Surface immunogenic protein; Tilapia.