Superoxide dismutase A antigens derived from molecular analysis of sarcoidosis granulomas elicit systemic Th-1 immune responses

Abstract

Background: Sarcoidosis is an idiopathic granulomatous disease with pathologic and immunologic features similar to tuberculosis. Routine histologic staining and culture fail to identify infectious agents. An alternative means for investigating a role of infectious agents in human pathogenesis involves molecular analysis of pathologic tissues for microbial nucleic acids, as well as recognition of microbial antigens by the host immune system. Molecular analysis for superoxide dismutase A (sodA) allows speciation of mycobacteria. SodA is an abundantly secreted virulence factor that generates cellular immune responses in infected hosts. The purpose of this study is to investigate if target antigens of the sarcoidosis immune response can be identified by molecular analysis of sarcoidosis granulomas.

Development of a Sarcoidosis Murine Lung Granuloma Model UsingMycobacteriumSuperoxide Dismutase A Peptide

“…The sodA peptide, AAAIAGAFGSFDKFR, was synthesized as described previously (11). Each peptide was synthesized by solid-phase F-moc chemistry (Genemed Synthesis, San Diego, CA) to a purity of greater than 70%.…”

“…Most recently, antigen-specific immune responses to mycobacterial virulence factors were reported to be present in sarcoidosis bronchoalveolar lavage (BAL) at the time of diagnosis, as mediated via Toll-like receptor 2 signaling (10). The molecular analysis of sarcoidosis granulomas for microbial virulence factors led to the identification of genetically distinct sequences of mycobacterial superoxide dismutase A (sodA; GenBank accession number DQ768096) (11). Unlike other proteins reported in sarcoidosis granulomas, these sequences had not been previously associated with other mycobacterial infections such as tuberculosis.…”

Programmed Death-1 Inhibition of Phosphatidylinositol 3-Kinase/AKT/Mechanistic Target of Rapamycin Signaling Impairs Sarcoidosis CD4+ T Cell Proliferation

“…Numerous elegant studies demonstrate that sarcoidosis T cells have increased cytokine production, as well as evidence of TCR stimulation (22,23). These studies have been complemented by molecular analyses demonstrating that microbial antigens are present within sarcoidosis granulomas (24)(25)(26)(27)(28) and that these same antigens are targets of the sarcoidosis adaptive immune response (14,26,(29)(30)(31). The expression of Th1 cytokines is the healthy adaptive immune response attempt to signal immune mediators that can clear foreign antigen, leading to its clearance.…”

Evidence for Mycobacteria in Sarcoidosis

“…Most of these sequences were identified as MTB SodA, but two were non-MTB (80). Using a distinct approach and in situ hybridization, Song and coworkers found evidence of mycobacterial catalase-peroxidase antigen (mKatG), another mycobacterial virulence factor, and MTB 16S rRNA DNA in a similar proportion of sarcoidosis tissues (z 40%) (81,82).…”

“…In other recent studies, sensitive techniques such as real-time PCR and sequencing detected several amplicons for the mycobacterial virulence factor superoxide dismutase A (SodA) in 12 of 17 sarcoidosis samples, compared with 2 of 16 negative control subjects (80). Most of these sequences were identified as MTB SodA, but two were non-MTB (80).…”