Induction of cytotoxic T-cell responses against culture filtrate antigens in Mycobacterium bovis bacillus Calmette-Guérin-infected mice

Abstract

CD8 ؉ T cells are essential for protection against mycobacteria, as is clearly demonstrated by the fatal outcome of experimental infection of ␤-2 microglobulin knockout mice. However, the mechanisms and antigens (Ags) leading to CD8 ؉ T-cell activation and regulation have been poorly characterized. Here we show that, upon immunization of major histocompatibility complex (MHC)-congenic mice with Mycobacterium bovis bacillus Calmette-Guérin (BCG), a cytotoxic response against BCG culture filtrate (CF) Ags (CFAgs) is induced in H-2 b and H-2 bxd haplotypes but not in H-2 d haplotype. This response is mediated by CD8 ؉ T cells and absolutely requires the activation of CD4 ؉ T cells and their secretion of interleukin 2. The lack of cytotoxic response in H-2 d mice cannot be explained by impaired cytokine production or by a defect in Ag presentation by H-2 d macrophages. Using the MHC class I mutant B6.C-H-2 bm13 mouse strain, we demonstrate that cytotoxic T lymphocytes (CTLs) recognize CFAgs exclusively in association with D b molecules. These Ags are cross-reactive in mycobacteria, since BCG-induced CTLs also recognize macrophages pulsed with CF from Mycobacterium tuberculosis H37Rv and H37Ra and from two virulent strains of M. bovis. Moreover, immunization with Mycobacterium kansasii induces CTLs able to lyse macrophages pulsed with BCG CF. Finally, we have found that these Ags can be characterized as hydrophilic proteins, since they do not bind to phenyl-Sepharose CL-4B. Our results indicate that MHC-linked genes exert a profound influence on the generation of CD8 ؉ CTLs following BCG vaccination.

Protection by CD4 or CD8 T Cells against PulmonaryMycobacterium bovisBacillus Calmette-Guérin Infection

“…Thus, we have demonstrated in this study an important role of T cells in the development of protective immune responses against pulmonary mycobacterial infection by M. bovis BCG. Normally, as in C57BL/6 mice, it is likely that increased CD4 T cells and, to a lesser degree, CD8 T cells contribute to such protection by the release of type 1 cytokines and by cytotoxic activities (2,4,14,16,17,21). However, in the absence of CD8 T cells, CD4 T cells themselves are functionally sufficient in mounting appropriate immune responses in the lungs which were both qualitatively and quantitatively almost indistinguishable from those in immunocompetent C57BL/6 mice.…”

Cellular interactions in bovine tuberculosis: release of active mycobacteria from infected macrophages by antigen‐stimulated T cells

“…The presentation of mycobacterial antigens remains a complex issue. 13 There is evidence for major histocompatibility complex (MHC) class II‐restricted CD4 + , 5 , 27 MHC class I‐restricted CD8 + , 8 , 13 , 21 CD1‐restricted CD8 + 28 and CD1‐restricted CD4 – CD8 – T cells. 29 We recently demonstrated presentation of soluble antigen to CD8 + T cells by an endogenous pathway in bovine tuberculosis.…”

“…Whether mycobacteria or their products escape from the phagosome to the cytoplasm remains a question open to debate. 13 , 30–32 In addition to the reasons discussed in our previous work, 21 the generation of CD8 + clones to MBSE could have been facilitated by the use of interleukin‐2 (IL‐2) in the cloning medium. Similarly, other authors using IL‐2 in conjunction with soluble antigens were able to activate class I MHC‐restricted CD8 + CTL populations.…”

“…7 The functional role for the CD8 + subset has been identified in several studies in humans 8–10 and mice. 11 , 12 Functionally, this subset of T cells can exert both immunoregulatory functions and CTL activity, 13–15 but there is still a lack of information on antigens and epitopes required for generation of CD8 + responses, as well as how these antigens are directed into the appropriate antigen‐processing pathways. While most reports have focused on the study of individual subpopulations, there is recent evidence in mice that either CD4 + or CD8 + T cells are required for protection, and when lacking both of these subpopulations the host fails to control mycobacterial infection.…”

Pathophysiology of Antigen 85 in Patients with Active Tuberculosis: Antigen 85 Circulates as Complexes with Fibronectin and Immunoglobulin G

“…Ag85 complex proteins induce delayed hypersensitivity, protective immune responses, and specific antibodies in infected mice and guinea pigs (2,9,15,(18)(19)(20)27). They also induce readily elicitable cellular immune responses in cultured peripheral blood mononuclear cells of most healthy purified protein derivative of tuberculin (PPD)-positive people and a few patients with clinically active tuberculosis (16,22).…”