PoM No 5,2013

Publication of the Month

May 05/13: Are ASCA more Immunologically Significant than we thought?

Key messages: 

  • S.cerevisiae shares antigenic epitopes with several auto-antigens
  • Anti- S.cerevisiae antibodies may play a role in many autoimmune diseases and their clinical use should be improved and better defined.

Rinaldi M, Perricone R, Blank M, Perricone C, Shoenfeld Y.
Anti-Saccharomyces cerevisiae Autoantibodies in Autoimmune Diseases: from Bread Baking to Autoimmunity
Clinic Rev Allerg Immunol; 2013: DOI 10.1007/s12016-012-8344-9

Background:

Saccharomyces cerevisiae is a commensal organism widely found in baked and brewed products as well as many vaccines. However, even such a classically non-pathogenic organism can trigger autoimmunity when the fine regulation of immune tolerance does not work properly. Anti- S.cerevisiae antibodies (ASCAs) are considered specific for Crohn’s Disease (CD) but are also being more and more frequently linked to other autoimmune diseases including anti-phospholipid syndrome, SLE, Type I diabetes mellitus and rheumatoid arthritis. This group looked at possible overlaps in molecular structure between yeast mannan and the most common autoantigens and also reviewed the data associating ASCAs with other autoimmune disorders.  

 Summary:

The review identified clear pathways by which yeast proteins can function antigenically. It also found significant cross reactivity between ASCAs and many antigens associated with autoimmune disorders. These included the ones mentioned above as well as systemic sclerosis, Behçet’s disease and, interestingly, acute myocardial infarction.   

Conclusions:

Given this, the authors raise the importance of defining the clinical use of ASCA tests, suggest a closer management of comorbidities (especially concerning increased cardiovascular risk) and question the ongoing use of vaccines containing S.cerevisiae plus adjuvants.   

Comment:

Although the data is too preliminary to suggest preventative yeast-free diet, the authors are keen to promote further evaluation of the clinical use of ASCAs, especially as they are known to be present years before the diagnosis of some related autoimmune diseases. Further, the demonstrated ability of S.cerevisiae to elicit an adaptive immune response – even autoreactive antibodies, may mean that its inclusion in vaccine preparations should be limited or at least further considered.

 

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.