The Mycobacterium tuberculosis Phagosome Is a HLA-I Processing Competent Organelle

PLoS Pathogens

Jeff E. Grotzke¹  David M. Lewinsohn¹  Deborah A. Lewinsohn²  Jacob Delepine²  Dawn Nolt²  Anne C. Siler³  Melanie J. Harriff³ 

[1] Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, Oregon, United States of America;Division of Infectious Diseases, Department of Pediatrics, Oregon Health & Science University, Portland, Oregon, United States of America;Division of Pulmonary & Critical Care Medicine, Department of Medicine, Oregon Health & Science University / Portland VA Medical Center, Portland, Oregon, United States of America

关键词: Phagosomes;    Mycobacterium tuberculosis;    Antigen presentation;    Cell membranes;    Antigen-presenting cells;    T cells;    Cytotoxic T cells;    Enzyme-linked immunoassays;   

DOI  :  10.1371/journal.ppat.1000374

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Mycobacterium tuberculosis (Mtb) resides in a long-lived phagosomal compartment that resists maturation. The manner by which Mtb antigens are processed and presented on MHC Class I molecules is poorly understood. Using human dendritic cells and IFN-γ release by CD8+ T cell clones, we examined the processing and presentation pathway for two Mtb–derived antigens, each presented by a distinct HLA-I allele (HLA-Ia versus HLA-Ib). Presentation of both antigens is blocked by the retrotranslocation inhibitor exotoxin A. Inhibitor studies demonstrate that, after reaching the cytosol, both antigens require proteasomal degradation and TAP transport, but differ in the requirement for ER–golgi egress and new protein synthesis. Specifically, presentation by HLA-B8 but not HLA-E requires newly synthesized HLA-I and transport through the ER–golgi. Phenotypic analysis of the Mtb phagosome by flow organellometry revealed the presence of Class I and loading accessory molecules, including TAP and PDI. Furthermore, loaded HLA-I:peptide complexes are present within the Mtb phagosome, with a pronounced bias towards HLA-E:peptide complexes. In addition, protein analysis also reveals that HLA-E is enriched within the Mtb phagosome compared to HLA-A2. Together, these data suggest that the phagosome, through acquisition of ER–localized machinery and as a site of HLA-I loading, plays a vital role in the presentation of Mtb–derived antigens, similar to that described for presentation of latex bead-associated antigens. This is, to our knowledge, the first description of this presentation pathway for an intracellular pathogen. Moreover, these data suggest that HLA-E may play a unique role in the presentation of phagosomal antigens.

【 授权许可】

CC BY