Abstract
Swine dysentery caused by Brachyspira hyodysenteriae, results in substantial economic losses in swine producing countries worldwide. Although a number of different vaccine approaches have been explored with regard to this disease, they show limitations and none of them have reached the market. We here determine the vaccine potential of a weakly haemolytic B. hyodysenteriae strain. The virulence of this strain was assessed in experimental infection trials and its protection against swine dysentery was quantified in a vaccination-challenge experiment using a seeder infection model. Systemic IgG production and local IgA production were monitored in serum and faeces respectively. Across all trials, pigs that were colonized by virulent, strongly haemolytic B. hyodysenteriae strains consistently developed swine dysentery, in contrast to none of the pigs colonized by the weakly haemolytic B. hyodysenteriae vaccine strain. In the seeder vaccination trial nearly all immunised animals developed swine dysentery on subsequent challenge with a virulent strain, but the speed of spread of swine dysentery and faecal score were significantly reduced in animals immunised with the weakly haemolytic strain compared to sham-immunised animals. The IgA response of immunised animals upon challenge with a virulent B. hyodysenteriae strain significantly correlated to a later onset of disease. The correlation between local IgA production and protection induced by a weakly haemolytic B. hyodysenteriae strain provides leads for future vaccine development against swine dysentery.
Highlights
Swine dysentery (SD) caused by Brachyspira hyodysenteriae (B. hyodysenteriae), results in substantial economic losses in swine producing countries worldwide
For the seeder vaccination trial, cultures were obtained in grossly the same way as for the virulence trials except that bacteria were grown in Brain Heart Infusion (BHI) broth with 10% Foetal Bovine Serum (FBS) for 30 h, after which the anaerobe broth was centrifuged at 1500 g for 20 min and the pellet was suspended in a volume leading to a final concentration of approximately 1 × 109 B. hyodysenteriae per mL
The low haemolytic B. hyodysenteriae strain D28 is avirulent in pigs In all virulence trials, faeces of all animals were negative for B. hyodysenteriae on arrival, some animals of each trial tested positive for B. innocens
Summary
Swine dysentery (SD) caused by Brachyspira hyodysenteriae (B. hyodysenteriae), results in substantial economic losses in swine producing countries worldwide. Several reports describe the use of whole cell bacterins [8,9,10,11,12] or protein digests of whole cell bacterins [13,14,15]. Some of these bacterins, administered intramuscularly or intravenously, induce partial protection, demonstrated by a lower proportion of animals developing clinical SD, or animals developing less severe disease signs of SD [8,9,10, 16]. Olson et al [12] described animals developing a more severe form of SD with an earlier onset after vaccination with
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