Novel recombinant BCG expressing perfringolysin O and the over-expression of key immunodominant antigens; pre-clinical characterization, safety and protection against challenge with Mycobacterium tuberculosis.
Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), has infected approximately two billion individuals worldwide with approximately 9.2 million new cases and 1.6 million deaths annually. Current efforts are focused on making better BCG priming vaccines designed to induce a comprehensive and balanced immunity followed by booster(s) targeting a specific set of relevant antigens in common with the BCG prime. We describe the generation and immunological characterization of recombinant BCG strains with properties associated with lysis of the endosome compartment and over-expression of key Mtb antigens. The endosome lysis strain, a derivative of BCG SSI-1331 (BCG(1331)) expresses a mutant form of perfringolysin O (PfoA(G137Q)), a cytolysin normally secreted by Clostridium perfringens. Integration of the PfoA(G137Q) gene into the BCG genome was accomplished using an allelic exchange plasmid to replace ureC with pfoA(G137Q) under the control of the Ag85B promoter. The resultant BCG construct, designated AERAS-401 (BCG(1331) DeltaureC::OmegapfoA(G137Q)) secreted biologically active Pfo, was well tolerated with a good safety profile in immunocompromised SCID mice. A second rBCG strain, designated AFRO-1, was generated by incorporating an expression plasmid encoding three mycobacterial antigens, Ag85A, Ag85B and TB10.4, into AERAS-401. Compared to the parental BCG strain, vaccination of mice and guinea pigs with AFRO-1 resulted in enhanced immune responses. Mice vaccinated with AFRO-1 and challenged with the hypervirulent Mtb strain HN878 also survived longer than mice vaccinated with the parental BCG. Thus, we have generated improved rBCG vaccine candidates that address many of the shortcomings of the currently licensed BCG vaccine strains.
Sun
Ronggai
R
Aeras Global TB Vaccine Foundation, 1405 Research Blvd., Rockville, MD 20850, USA.
Skeiky
Yasir A W
YA
Izzo
Angelo
A
Dheenadhayalan
Veerabadran
V
Imam
Zakaria
Z
Penn
Erica
E
Stagliano
Katherine
K
Haddock
Scott
S
Mueller
Stefanie
S
Fulkerson
John
J
Scanga
Charles
C
Grover
Ajay
A
Derrick
Steven C
SC
Morris
Sheldon
S
Hone
David M
DM
Horwitz
Marcus A
MA
Kaufmann
Stefan H E
SH
Sadoff
Jerald C
JC
D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D001500:BCG Vaccine / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D001427:Bacterial Toxins / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D004912:Erythrocytes / Q000382:microbiology; D005260:Female; D005798:Genes, Bacterial; D006168:Guinea Pigs; D006460:Hemolysin Proteins / Q000235:genetics / Q000276:immunology*; D006461:Hemolysis; D016056:Immunodominant Epitopes / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D009163:Mycobacterium bovis / Q000235:genetics / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000276:immunology; D010957:Plasmids; D012756:Sheep; D014376:Tuberculosis / Q000276:immunology / Q000517:prevention & control*
D000942:Antigens, Bacterial; D001500:BCG Vaccine; D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D016056:Immunodominant Epitopes; C072681:Mycobacterium tuberculosis antigens; C020452:Clostridium perfringens theta-toxin