HYPEREXPRESSION SYSTEM FOR RECOMBINANT BCG VACCINES

BCG, A LIVE ATTENUATED STRAIN OF MYCOBACTERIUM BOVIS, OFFERS A NUMBER A DISTINCT ADVANTAGES AS A LIVE RECOMBINANT VACCINE VEHICLE. THESE ADVANTAGES INCLUDE POTENT ADJUVANT ACTIVITY AND AHISTORY OF SAFE USE IN HUMANS AS A TUBERCULOSIS VACCINE. MAJOR GENETIC OBSTACLES IMPEDING THE DEVELOPMENT OF BCG AS A VACCINE VEHICLE HAVE NOW BEEN LARGELY OVERCOME WITH THE DEVELOPMENT OF ESCHERICHIA COLI/MYCOBACTERIAL SHUTTLE VECTORS. RECENT IMMUNOGENICITY STUDIES WITH SEVERAL RECOMBINANT BCG-BASED VACCINES ARE PROMISING AND SUGGEST THAT HIGH-LEVEL EXPRESSION OF TARGET ANTIGEN MAY CONTRIBUTE TO ITS ANTIGEN IMMUNODOMINANCE IN THE COMPLEX BACKGROUND OF MYCOBACTERIAL PROTEINS. SINCE IT HAS BEEN OBSERVED THAT CONSTITUTIVE HIGH-LEVEL EXPRESSION OF SOME FOREIGN ANTIGENS IN BCG IS DELETERIOUS TO THE BCG HOST STRAIN, WE WILL DEVELOP A BCG VECTOR/HOST SYSTEM INCORPORATING BCG STRESS PROMOTERS WITH TRANSCRIPTIONAL COMPONENTS FROM BACTERIOPHAGE T7 (T7 RNA POLYMERASE) AND THE E. COLI LACTOSE OPERON (LAC REPRESSOR AND OPERATOR TO REGULATE THE HIGH-LEVEL SYNTHESIS OF RECOMBINANT ANTIGENS IN BCG. IN ADDITION TO PROVIDINGAN INEXPENSIVE SOURCE OF ANTIGEN IN AN IMMUNOGENIC FORMAT WITHOUT ANTIGEN PURIFICATION, IT IS ALSO POSSIBLE THAT THE BCG/T7 SYSTEM COULD PROVIDE AN ALTERNATIVE TO LIVE RECOMBINANT BCG VACCINES WHICH MIGHT NOT BE SUITABLE IN IMMUNOCOMPROMISED INDIVIDUALS.