Mycobacterium bovis BCG as Vaccine-vectors

The Bacillus Calmette-Guerin (BCG) is an attenuated strain of Mycobacterium bovis that has been widely used as a vaccine against human tuberculosis. This live bacterial vaccine is capable of establishing persistent infections and inducing cellular and humoral immune responses. With the development of the genetic system of mycobacteria and its adjuvant nature, its potential use as bacterial carrier for heterologous antigens appears as extremely attractive.

Mycobacterium bovis BCG

Mycobacterium bovis BCG as Vaccine-vectors– Creative Biolabs

The Bacillus Calmette-Guérin (BCG) is a strain of Mycobacterium bovis (M. bovis) that was attenuated by more than 200 passages on glycerinated bile-potato medium between 1906 and 1920. During in vitro passage, BCG undergoes loss and/or rearrangement of several gene complexes. BCG is currently the most widely used vaccine in the world and has been given to more than 3 billion people since 1921. In addition to being used as a vaccine against human tuberculosis, the special adjuvant properties of BCG make it an attractive living vehicle for the development of recombinant vaccines against other diseases. In recent years, a variety of viral, bacterial and parasitic antigens have been expressed in recombinant BCG (rBCG), many of which induce strong humoral and/or cellular immune responses following oral or parenteral immunization.

The Features of Mycobacterium bovis BCG Vaccine-vectors

BCG offers a number of unique and beneficial features that make it suitable as a vaccine carrier:

  • Low cost
  • Stable and safe
  • Uninfluenced by maternal antibodies
  • Can be administered orally
  • Highly immunogenic
  • Single dosage can trigger long-lasting immunity

The Strategies for Mycobacterium bovis BCG as Vaccine-vectors in Creative Biolabs 

Promoters

The expression of foreign genes in mycobacteria can be regulated by the promoter for driving expression of the foreign gene. Several promoters have been widely used in the E. coli-mycobacterial shuttle vectors. The most commonly used is the promoter from the heat shock protein gene hsp60 or hsp70. In addition, we designed other promoters in the shuttle vector including the promoter from M. kansasii (α) antigen, M. paratuberculosis PAN, M. tuberculosis 19 kDa antigen and the M. fortuitum β lactamase pBlaF.

The design of the expression vector

The expression of heterologous genes in BCG can be achieved using either replicative or integrative vectors. Most of the mycobacterial replicative vectors are designed using the origin of replication from the pAL5000, with up to 5 plasmid copies per bacterial cell. As an alternative, integration-proficient vectors utilizing the mycobacteriophage L5 integration system were developed in Creative Biolabs which exhibit excellent stability. In addition to this, we have developed different genetic systems for the expression of foreign antigens in mycobacteria, including the development of different shuttle vectors, systems to express and secrete heterologous antigens and strategies for transformation of mycobacteria.

  • The E. coli cosmid is inserted into the temperate mycobacterial phage Li to produce shuttle phasmids that replicate as plasmids in E. coli and phage capable of lysogenizing the mycobacterial host. These temperate shuttle phasmids form turbid plaques after lysogenization and confer resistance to superinfection and integrate within the mycobacterial chromosome.
  • We design a foreign antigen secretion system in mycobacteria in which an extracellular ɑ antigen (ɑ-K) of Mycobacterium kansasii was utilized as a carrier. The constructed vector consists of a promoter, a signal peptide region and a structural gene of ɑ-K. They are introduced into BCG and M. smegmatis by electroporation.
  • A plasmid transformation system was developed in mycobacteria. Mycobacterium fortuitum / E. coli hybrid plasmid containing a mycobacteria and E. coli replicon and a kanamycin resistance gene is constructed. These shuttle plasmids confer stable kanamycin resistance upon transformants when introduced into M. smegmatis or BCG by electroporation.

BCG represents an effective vehicle for delivery of heterologous antigens due to its good characteristics. With years of experience and advanced vaccine technology platform, Creative Biolabs has designed a variety of methods based on BCG to deliver foreign antigens to host cells. If you are interested in this service, please feel free to contact us.


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