Gene Deletions in Mycobacterium bovis BCG Stimulate Increased CD8⁺T Cell Responses

Abstract

c Mycobacteria, the etiological agents of tuberculosis and leprosy, have coevolved with mammals for millions of years and have numerous ways of suppressing their host's immune response. It has been suggested that mycobacteria may contain genes that reduce the host's ability to elicit CD8 ؉ T cell responses. We screened 3,290 mutant Mycobacterium bovis bacillus Calmette Guerin (BCG) strains to identify genes that decrease major histocompatibility complex (MHC) class I presentation of mycobacterium-encoded epitope peptides. Through our analysis, we identified 16 mutant BCG strains that generated increased transgene product-specific CD8 ؉ T cell responses. The genes disrupted in these mutant strains had disparate predicted functions. Reconstruction of strains via targeted deletion of genes identified in the screen recapitulated the enhanced immunogenicity phenotype of the original mutant strains. When we introduced the simian immunodeficiency virus (SIV) gag gene into several of these novel BCG strains, we observed enhanced SIV Gag-specific CD8؉ T cell responses in vivo. This study demonstrates that mycobacteria carry numerous genes that act to dampen CD8 ؉ T cell responses and suggests that genetic modification of these genes may generate a novel group of recombinant BCG strains capable of serving as more effective and immunogenic vaccine vectors.

Inhibition of apoptosis by Rv2456c through Nuclear factor-κB extends the survival of Mycobacterium tuberculosis

“…2B ), we would expect to see an increased ability of FID19 to induce a CD8 + T cell response [ 17 , 18 ]. To test this hypothesis, we utilized a variation of a previously described in vitro assay [ 30 , 31 ]. Briefly, BMDMs were infected with H37Rv or FID19 expressing SIINFEKL.…”

Interleukin-17A as a Biomarker for Bovine Tuberculosis

“…In immunocompetent mice, the BCG deletions ⌬fdr8, ⌬mmaA4, and ⌬pks16 each result in enhanced mycobacterial immunogenicity through enhanced cross-presentation of mycobacterial antigens (⌬fdr8), cytokine modulation (⌬mmaA4), and biofilm formation (⌬pks16), compared to the parental BCG (21; Berney-Meyer et al, unpublished). BCG mutants, such as these, may also be used as vaccine vectors to promote epitope-specific responses (e.g., BCG ⌬pks12 for enhanced CD8 responses) (23).…”

Increased TNF-α/IFN-γ/IL-2 and Decreased TNF-α/IFN-γ Production by Central Memory T Cells Are Associated with Protective Responses against Bovine Tuberculosis Following BCG Vaccination

“…In immunocompetent mice, the BCG deletions Δ fdr8 , Δ mmaA4 , and Δ pks16 each result in enhanced mycobacterial immunogenicity through enhanced cross-presentation of mycobacterial antigens (Δ fdr8 ), cytokine modulation (Δ mmaA4 ), and biofilm formation (Δ pks16 ), as compared to the parental BCG [( 48 ) and Berney-Meyer et al, unpublished data]. BCG mutants, such as these, may also be used as vaccine vectors to promote epitope-specific responses (e.g., BCG Δ pks12 for enhanced CD8 responses) ( 50 ). In the present study and as presented elsewhere ( 51 ), BCG Danish and the cocktail of BCG Danish deletions (hereafter called BCG mutants) were equally protective and induced similar IFN-γ- and Th17-associated cytokine responses, as evaluated in ex vivo assays for diagnostic purposes.…”