Live antigen carriers as tools for improved anti-tuberculosis vaccines

Recombinant (r) Mycobacterium bovis BCG strains have been constructed which secrete biologically active listeriolysin (Hly) fusion protein of Listeria monocytogenes. In human and murine macrophage-like cell lines: intracellul ar persistence of these r-BCG strains was reduced as compared to the parent al BCG strain. By immunogold labelling Hly was detected in membrane structu res and within the phagosomal space of macrophages. Hly fusions consistentl y co-localized with a lysosome-associated membrane glycoprotein (LAMP-1) su ggesting that membrane attack conformation of Hly was not altered. Although r-BCG microorganisms apparently did not egress into the cytoplasmic compar tment of host cells. they both improved major histocompatibility complex cl ass I presentation of co-phagocytosed soluble ovalbumin as compared with wi ld-type BCG microbes. These data suggest that Hly secretion endows BCG with an improved capacity to stimulate CD8 T cells. Because CDS T cells play a major role in protection against tuberculosis such Hly-secreting r-BCG cons tructs are anti-tuberculosis vaccine candidates. In addition, we report on our r-Salmonella typhimurium expression system combined with the HlyB/HlyD/ TolC export machinery for delivering the prominent mycobacterial antigen Ag 85B for immune recognition. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.