Editor’s Comment: Heat shock proteins (HSP) prevent cellular damage when an organism is exposed to elevated temperatures or other stress. Consequently, HSPs are increased by infections, as well as inflammation, exercise and exposure to environmental toxins. HSP protein 60 (HSP60) also plays an important role in mitochondrial function and in immune system activation. Recent research indicates that when bacterial HSP60 cross-reacts with human HSP60 (let’s say through a bacterial infection) an autoimmune cascade may be initiated.
The authors of this study speculate that high levels of anti-HSP60 (autoantibodies) in a subset of people with ME indicates the presence of autommunity. They also speculate that because HSP60 plays an important role in mitchondrial function, the easy fatigability of patients with ME could be due to the same mechanism. In a further link to immune system abnormalities commonly found in ME patients, the authors conclude that “It is conceivable that a disturbance in HSP60 turnover brought about by anti-HSP60 could influence NK cell activity.”
Myalgic encephalomyelitis (ME, also called Chronic Fatigue Syndrome), a common disease with chronic fatigability, cognitive dysfunction and myalgia of unknown etiology, often starts with an infection.
The chaperonin human heat shock protein 60 (HSP60) occurs in mitochondria and in bacteria, is highly conserved, antigenic and a major autoantigen. The anti-HSP60 humoral (IgG and IgM) immune response was studied in 69 ME patients and 76 blood donors (BD) (the Training set) with recombinant human and E coli HSP60, and 136 30-mer overlapping and targeted peptides from HSP60 of humans, Chlamydia, Mycoplasma and 26 other species in a multiplex suspension array. Peptides from HSP60 helix I had a chaperonin-like activity, but these and other HSP60 peptides also bound IgG and IgM with an ME preference, theoretically indicating a competition between HSP60 function and antibody binding. A HSP60-based panel of 25 antigens was selected.
When evaluated with 61 other ME and 399 non-ME samples (331 BD, 20 Multiple Sclerosis and 48 Systemic Lupus Erythematosus patients), a peptide from Chlamydia pneumoniae HSP60 detected IgM in 15 of 61 (24%) of ME, and in 1 of 399 non-ME at a high cutoff (p<0.0001). IgM to specific cross-reactive epitopes of human and microbial HSP60 occurs in a subset of ME, compatible with infection-induced autoimmunity.
Source: Elfaitouri A, Herrmann B, Bölin-Wiener A, Wang Y, Gottfries C-G, et al. (2013) Epitopes of Microbial and Human Heat Shock Protein 60 and Their Recognition in Myalgic Encephalomyelitis. PLoS ONE 8(11): e81155. doi:10.1371/journal.pone.0081155