Corynebacterium pseudotuberculosis as Vaccine-vectors
Corynebacterium pseudotuberculosis, a gram-positive intracellular bacterium, is the etiological agent of the economically important disease caseous lymphadenitis (CLA) in both sheep and goats. With an in-depth study of its molecular biological characteristics, some attenuated mutants of Corynebacterium pseudotuberculosis have the potential to act as novel vaccines against CLA and as veterinary vaccine vectors. Importantly, the immune response to an antigen delivered by this vector can potentially be long lasting, thus circumventing the requirement for multiple vaccinations.
Corynebacterium pseudotuberculosis
Corynebacterium pseudotuberculosis (C. pseudotuberculosis) is a gram-positive, mycolic acid-containing facultative intracellular pathogen which is phylogenetically related to Mycobacterium tuberculosis. C. pseudotuberculosis is the etiological agent of the disease caseous lymphadenitis (CLA) or cheesy gland, a chronic and subclinical disease that affects sheep and goats worldwide. The pathogenic process of CLA in sheep and goats is not well defined, and at least two major virulence determinants have been identified. One of them is the toxic lipid cell wall, which mediates the bacterium’s resistance to killing by phagocytic cells. The other identified virulence determinant is a sphingomyelin-degrading phospholipase D (PLD) exotoxin. PLD enhances the virulence of C. pseudotuberculosis by limiting bacterial opsonization, increasing vascular permeability to promote bacterial transmission, allowing bacteria to escape from neutrophils, and impairing the chemotaxis of neutrophils toward the site of infection.
The Mutation of the Corynebacterium pseudotuberculosis
- C. pseudotuberculosis was attenuated by inactivation of the major virulence factor, PLD, to produce a strain designated Toxminus. This Δpld mutant strain has been shown to retains the ability to stimulate host protective immune response and can be used to deliver recombinant proteins to the sheep immune system when delivered orally or subcutaneously.
- The aroQ gene encodes a type II 3-dehydroquinase enzyme that may be involved in the biosynthesis of aromatic amino acids in the bacterium. The aroQ mutant of C. pseudotuberculosis is constructed by allelic exchange and remains attenuated even in immunocompromised animals. The reduced virulence of these bacterial strains may be due to their requirement for p-aminobenzoic acid, a precursor of folic acid and a compound that is not synthesized by the chordate. Since bacteria cannot take up exogenous folate and the availability of p-aminobenzoic acid in vertebrate tissue is limited, the growth of aro mutants in vivo is severely limited.
Antigen Expression in Corynebacterium pseudotuberculosis
An important requirement in adapting C. pseudotuberculosis for use as a vaccine vector is to establish methods for heterologous gene expression. Creative Biolabs has developed the basic methods needed to study heterologous gene expression. Expression has been achieved from both plasmid-borne and chromosomally integrated expression cassettes. The E. coli-Mycobacterium-Corynebacterium shuttle plasmid is used as the starting vector for the construction of the expression plasmids and integration cassettes.
Construction of plasmids expressing foreign antigens
A plasmid expressing foreign antigen is made by inserting foreign gene downstream of the PLD promoter and secretion signal sequence. The recombination plasmid is electroporated into C. pseudotuberculosis and transformants were screened by the antibiotic.
Chromosomal integration
The integration cassette consists of the foreign gene to be moved to the chromosome flanked by PLD gene sequences. Creative Biolabs has designed a number of expression vectors to contain expressed genes within PLD sequences, making them useful not only for plasmid-based expression but also for generating chromosomal integrants.
C. pseudotuberculosis represents an effective vehicle for delivery veterinary vaccine antigen genes. With years of experience and advanced vaccine technology platform, Creative Biolabs has designed a variety of methods to deliver foreign antigens to host cells. If you have any need, we are your best choice.
All of our products can only be used for research purposes. These vaccine ingredients CANNOT be used directly on humans or animals.
