T Cell Expression Cloning of aMycobacterium tuberculosisGene Encoding a Protective Antigen Associated with the Early Control of Infection

Abstract

Infection of C57BL/6 mice with Mycobacterium tuberculosis results in the development of a progressive disease during the first 2 wk after challenge. Thereafter, the disease is controlled by the emergence of protective T cells. We have used this infection model in conjunction with direct T cell expression cloning to identify Ags involved with the early control of the disease. A protective M. tuberculosis-specific CD4 T cell line derived from mice at 3 wk postchallenge was used to directly screen an M. tuberculosis genomic expression library. This screen resulted in the identification of a genomic clone comprising two putative adjacent genes with predicted open reading frames of 10 and 41 kDa, MTB10 and MTB41, respectively (the products of Rv0916c and Rv0915c, respectively, in the TubercuList H37Rv database). MTB10 and MTB41 belong to the PE and PPE family of proteins recently identified to comprise 10% of the M. tuberculosis genome. Evaluation of the recombinant proteins revealed that MTB41, but not MTB10, is the Ag recognized by the cell line and by M. tuberculosis-sensitized human PBMC. Moreover, C57BL/6 mice immunized with MTB41 DNA developed both CD4- (predominantly Th1) and CD8-specific T cell responses to rMTB41 protein. More importantly, immunization of C57BL/6 mice with MTB41 DNA induced protection against infection with M. tuberculosis comparable to that induced by bacillus Calmette-Guérin. Thus, the use of a proven protective T cell line in conjunction with the T cell expression cloning approach resulted in the identification of a candidate Ag for a subunit vaccine against tuberculosis.

Therapeutic effect of DNA vaccines combined with chemotherapy in a latent infection model after aerosol infection of mice with Mycobacterium tuberculosis

“…34,35 Many attempts have been made to elucidate the natures of the TB antigens involved in stimulating protective IFN-g production. Actually, it was reported that IFN-g production specific for antigens of M. tuberculosis such as Ag85A, 35,36 Ag85B, 35,37 MTB41, 38 and ESAT-6 39 dramatically reduces in patients with active TB but not in HTR, suggesting that these antigens may be candidate protective antigens. 8 In the case of Ag85A, it was also demonstrated that the reduced production of IFN-g in response to Ag85A was significantly restored in PBMCs 35 after anti-TB chemotherapy in patients with active disease, suggesting that Ag85A-specific IFN-g response might be involved in the clinical phenotype and immunopathogenesis of human active pulmonary TB.…”

Classically Restricted Human CD8+ T Lymphocytes Derived fromMycobacterium tuberculosis-Infected Cells: Definition of Antigenic Specificity

“…mAbs were generated from hybridoma supernatants from the anti-panHLA (W6/32), anti-HLA-B,C (B1. 23 (24,25), 38 kDa (26), and ESAT-6 (27) proteins were prepared as previously described (18).…”

Detecting selection using a single genome sequence of M. tuberculosis and P. falciparum

“…In fact, the PE and PPE genes are ten times more frequent among the 100 most volatile M. tuberculosis genes than they are in the genome as a whole. The elevated volatility of these genes indicates increased pressure for amino-acid substitutions, presumably because of diversifying selection mediated by interactions with the host immune system 12,13 . These results, based on a single genome sequence, agree with an extensive study in which the authors compared the genomes of two fully sequenced M. tuberculosis strains 2 .…”

“…2). For both pathogens, the genes with extreme volatility are distributed throughout the genome.The PE and PPE gene families of M. tuberculosis, which are putatively expressed on the extracellular surface and exhibit extensive non-synonymous variability 2 , have been identified as potential antigens for the host immune response [11][12][13] . The PE family (81 genes) and the PPE family (57 genes) both exhibit significantly greater volatility than the other genes in the M. tuberculosis genome (P w ¼ 6 £ 10 28 for PE and P w ¼ 3 £ 10 222 for PPE; Wilcoxon Figure 1 Two examples of calculating codon volatility.…”