Abstract
As the causative agent of Glässer’s disease, Glaesserella (Haemophilus) parasuis has led to serious economic losses to the swine industry worldwide. Due to the low cross-protection of vaccines and increasing antimicrobial resistance of G. parasuis, it is important to develop alternative approaches to prevent G. parasuis infection. Defensins are host defense peptides that have been suggested to be promising substitutes for antibiotics in animal production, while porcine β-defensin 2 (PBD-2) is a potent antimicrobial peptide discovered in pigs. Our previous study generated transgenic (TG) pigs overexpressing PBD-2, which displayed enhanced resistance to Actinobacillus pleuropneumoniae. In this study, the antibacterial activities of PBD-2 against G. parasuis are determined in vitro and in the TG pig model. The concentration-dependent bactericidal activity of synthetic PBD-2 against G. parasuis was measured by bacterial counting. Moreover, after being infected with G. parasuis via a cohabitation challenge model, TG pigs overexpressing PBD-2 displayed significantly milder clinical signs and less severe gross pathological changes than their wild-type (WT) littermates. The TG pigs also exhibited alleviated lung and brain lesions, while bacterial loads in the lung and brain tissues of the TG pigs were significantly lower than those of the WT pigs. Additionally, lung and brain homogenates from TG pigs possessed enhanced antibacterial activity against G. parasuis when compared with those from the WT pigs. Altogether, these proved that overexpression of PBD-2 could also endow pigs with increased resilience to G. parasuis infection, which further confirmed the potential of using the PBD-2 coding gene to develop disease-resistant pigs and provided a novel strategy to combat G. parasuis as well.
Highlights
Defensins are endogenous antimicrobial peptides that are widely distributed in vertebrates, invertebrates, plants, and fungi [1,2]
To explore potential therapeutic and prophylactic methodologies against Glässer’s disease, this study aims to determine the antibacterial activity of PBD-2 against G. parasuis both in vitro and in TG pigs, would contribute to further use of the gene coding for PBD-2 as a potential
These results indicate that synthetic PBD-2 has a dose-dependent direct bacterial killing effect against effect against G. parasuis
Summary
Defensins are endogenous antimicrobial peptides that are widely distributed in vertebrates, invertebrates, plants, and fungi [1,2]. They constitute a major family of host defense peptides, which have been suggested to be attractive alternatives to the usage of antibiotics in animal production [3,4]. Genes encoding defensins have been widely used as candidates to produce disease-resistant animals. Overexpression of the mouse defensin Bin1b in mice could protect against Escherichia coli infection [8]. Transgenic expression of human defensin 5 in mice conferred enhanced resistance to Salmonella enterica serotype
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