Abstract
BackgroundPoultry is the world's most popular animal-based food and global production has tripled in the past 20 years alone. Low-cost vaccines that can be combined to protect poultry against multiple infections are a current global imperative. Glycoconjugate vaccines, which consist of an immunogenic protein covalently coupled to glycan antigens of the targeted pathogen, have a proven track record in human vaccinology, but have yet to be used for livestock due to prohibitively high manufacturing costs. To overcome this, we use Protein Glycan Coupling Technology (PGCT), which enables the production of glycoconjugates in bacterial cells at considerably reduced costs, to generate a candidate glycan-based live vaccine intended to simultaneously protect against Campylobacter jejuni, avian pathogenic Escherichia coli (APEC) and Clostridium perfringens. Campylobacter is the most common cause of food poisoning, whereas colibacillosis and necrotic enteritis are widespread and devastating infectious diseases in poultry.ResultsWe demonstrate the functional transfer of C. jejuni protein glycosylation (pgl) locus into the genome of APEC χ7122 serotype O78:H9. The integration caused mild attenuation of the χ7122 strain following oral inoculation of chickens without impairing its ability to colonise the respiratory tract. We exploit the χ7122 pgl integrant as bacterial vectors delivering a glycoprotein decorated with the C. jejuni heptasaccharide glycan antigen. To this end we engineered χ7122 pgl to express glycosylated NetB toxoid from C. perfringens and tested its ability to reduce caecal colonisation of chickens by C. jejuni and protect against intra-air sac challenge with the homologous APEC strain.ConclusionsWe generated a candidate glycan-based multivalent live vaccine with the potential to induce protection against key avian and zoonotic pathogens (C. jejuni, APEC, C. perfringens). The live vaccine failed to significantly reduce Campylobacter colonisation under the conditions tested but was protective against homologous APEC challenge. Nevertheless, we present a strategy towards the production of low-cost “live-attenuated multivalent vaccine factories” with the ability to express glycoconjugates in poultry.
Highlights
Poultry is the world’s most popular animal-based food and global production has tripled in the past 20 years alone
We present a strategy towards the production of low-cost “live-attenuated multivalent vac‐ cine factories” with the ability to express glycoconjugates in poultry
The homology arms result in the introduction of the pgl cassette into a pseudogene, with the loss of 12 bp of the pseudogene between genes gidB and atpI, an integration site that was previously shown to promote efficient expression of a reporter protein [48]. pCVD442 was used as a suicide vector backbone as it carries a pir-dependent R6K origin of replication, requiring λpir + strains for its maintenance, and the sacB gene of Bacillus subtilis conferring sensitivity to sucrose, allowing positive selection for double recombinants that have lost the vector and carry the endogenous copy of the target region [49]
Summary
Poultry is the world’s most popular animal-based food and global production has tripled in the past 20 years alone. Low-cost vaccines that can be combined to protect poultry against multiple infections are a current global imperative. We use Protein Glycan Coupling Technology (PGCT), which enables the production of glycoconjugates in bacterial cells at considerably reduced costs, to generate a candidate glycan-based live vaccine intended to simultaneously protect against Campylobacter jejuni, avian patho‐ genic Escherichia coli (APEC) and Clostridium perfringens. Infectious diseases remain a significant impediment to poultry welfare and productivity. There is a growing demand to identify successful strategies to prevent the spread of diseases within and from flocks, to avert significant economic losses and to mitigate the healthcare burden resulting from zoonoses arising from poultry products
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