Abstract
Aquaculture is one of the fastest-growing food-producing sectors in the world. However, its growth is hampered by various disease problems due to infectious microorganisms, including Gram-negative bacteria in finfish aquaculture. Disease control in aquaculture by use of antibiotics is not recommended as it leads to antibiotic residues in the final product, selection, and spread of antibiotic resistance in the environment. Therefore, focus is on disease prevention by vaccination. All Gram-negative bacteria possess surface-associated outer membrane proteins (OMPs), some of which have long been recognized as potential vaccine candidates. OMPs are essential for maintaining the integrity and selective permeability of the bacterial membrane and play a key role in adaptive responses of bacteria such as solute and ion uptake, iron acquisition, antimicrobial resistance, serum resistance, and bile salt resistance and some adhesins have virulence attributes. Antigenic diversity among bacterial strains even within the same bacterial species has constrained vaccine developments, but OMPs that are conserved across serotypes could be used as potential candidates in vaccine development, and several studies have demonstrated their efficacy and potential as vaccine candidates. In this review, we will look into the application of OMPs for the design of vaccines based on recombinant proteins, subunit vaccines, chimeric proteins, and DNA vaccines as new-generation vaccine candidates for major bacterial pathogens of fish for sustainable aquaculture.
Highlights
Asia accounts for more than 80% of the global aquaculture production of which India is the third largest producer [1, 2]
outer membrane proteins (OMPs) are essential molecules of Gram-negative bacteria as they play various roles including adaptation, immunogenicity, and pathogenesis of bacterium. They possess epitopes essential for binding to B and T lymphocytes, rendering them to be ideal vaccine candidates for both extra- and intra-cellular replicating bacteria. They have been widely used in vaccine development for the Indian aquaculture, which has a high prevalence of both extra- and intracellular replicating bacterial pathogens such as Edwardsiella spp., Aeromonads, Vibrio spp., and Flavobacterium spp
The quest to develop safe vaccines that do not pose the danger of reversion to virulence, such as live attenuated vaccines, coupled with the need for vaccines able to evoke both humoral and cell-mediated immune (CMI) responses, unlike whole cell inactivated (WCI) vaccines, has extended the search for protective vaccines to include OMPs in vaccine development
Summary
Asia accounts for more than 80% of the global aquaculture production of which India is the third largest producer [1, 2]. We provide an up-to-date status of ongoing research on OMP vaccines being developed against major pathogens infecting the top-farmed fish species in Indian aquaculture. In the case of Indian aquaculture where intracellular replicating bacteria such as A. hydrophila and Edwardsiella spp. account for a large proportion of pathogens infecting top farmed fish species, there is a need for vaccines able to evoke both humoral and CMI responses. Patterns (PAMPs) such as lipopolysaccharide (LPS) recognized by pathogen recognition receptors (PRRs) found on host cells such as monocytes, macrophages, neutrophils, and dendritic cells involved in antigen uptake, processing, and presentation to cells of the adaptive immune system for induction of long-term protective immunity Overall, this supports the use of OMPs as ideal vaccine candidates for both intra- and extracellular bacteria that are endemic in Indian aquaculture. Genetically engineered vaccines help remove undesired harmful antigens or cleave
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