Tuesday, 10 January 2012

Autism and Sutterella

Barely a few days into 2012 and like the tulips in my garden sprouting very early this year because of our exceptionally mild winter, the first research papers of the new year are popping up through the scientific soil. Two studies have so far caught my eye: the first by Harumi Jyonouchi and colleagues* (full-text) looked at some potential overlap between cases of autism spectrum condition and specific polysaccharide antibody deficiency (SPAD); the second by Brent Williams and colleagues** (full-text) reported on some of the differences in gastrointestinal (GI) bacteria present in children with autism compared with controls.

I am going to leave the Jyonouchi paper for now, except for pointing out quite an interesting detail from the paper suggesting that levels of the anti-inflammatory cytokine IL-10 seemed to be an issue (lower) for many participants with autism compared with asymptomatic controls. IL-10 has cropped up before in autism research circles and might yet hold some interesting clues about things like inflammation.

The last paper that I discussed on this blog from Brent Williams holds a special place for me in terms of it uniting gut bacteria, carbohydrate metabolism and GI issues in some cases of autism. His latest offering was therefore always going to be one to watch for me. Before progressing with the summary, it is interesting to note the involvement of Prof. Ian Lipkin in this research. I have quite a bit of time for Prof. Lipkin and his pretty extensive repertoire of research that he has published on ranging from maternal infection inducing subtle neuropathology in offspring to the continuing saga of viral infections 'associated' (?) with conditions like CFS/ME. This is a chap who is not afraid of a little controversy.

The paper is open-access but just in case:

  • Biposy samples from 23 participants diagnosed with autism and gastrointestinal (GI) symptoms were compared with 9 samples from control participants with GI symptoms. Ages ranged from 3-10 years old.
  • Same as last time, pinch biopsies were taken from the terminal ileum and cecum. Various methods were used to analyse these samples including a novel PCR method used to detect and quantify bacteria from the Sutterella genus.
  • Following on from the previous findings of a high abundance of sequences from the Alcaligenaceae family in quite a few of the samples from the autistic group, further more detailed analysis showed that "all sequences of Alcaligenaceae found in AUT-GI patients’ biopsy samples were classified as members of the genus Sutterella". Sutterella presence was confirmed by their super-duper PCR method and the presence of various strains of Sutterella are reported for individual participants. Wikipedia has a more in-depth discussion about categorising bacteria on the basis of their taxonomic rank.
  • Plasma antibodies against a specific strain of Sutterella (Sutterella wadsworthensis) were also detected in the autistic group (IgG) (IgM antibodies in one case) confirming its presence. 
  • In total 12/23 (52%) of the autism group were PCR positive for Sutterella compared with none of the control group. This is the point that most of the media so far have focused on.

Sutterella, apparently named in memory of one Vera Sutter, who as the linked article suggests worked with Sydney Finegold (remember this paper) is a bacteria that I've not come across before. This paper describing the discovery of S.wadsworthensis explains it as a gram-negative bacteria thriving in low oxygen or anaerobic conditions. Sutterella has been previously linked to inflammatory bowel disease such as Crohn's disease although the more recent data has cast some doubt on the exclusivity of this link.

Whilst the methods and findings used in the current study are interesting, I wait to see where this work will go. It is interesting that in the discussion, the authors talk about abnormal intestinal permeability (the so-called leaky gut) and the potential resulting consequences of the the immune system meeting GI bacteria in places where they shouldn't really be meeting. In this study they specifically looked at plasma antibodies against S.wadsworthensis. The question is: what other antibodies might be present in cases of autism against other GI bacterial companions and what the net effect of this antibody load might be on a person. Interesting that increased epithelial IgG density has been noted before in cases of autism and bowel enteropathy.

I remain very attentive to this whole area of gut bacteria and autism (and other conditions) and hope to see a few more papers like this one in 2012 further probing the various goings-on of our bacterial masters. To finish, a song about a different type of bloom.

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* Jyonouchi H. et al. Immunological characterization and transcription profiling of peripheral blood (PB) monocytes in children with autism spectrum disorders (ASD) and specific polysaccharide antibody deficiency (SPAD): Case study. Journal of Neuroinflammation. January 2012.

** Williams B. et al. Application of novel PCR-based methods for detection, quantitation, and phylogenetic characterization of Sutterella species in intestinal biopsy samples from children with autism and gastrointestinal disturbances. mBio. January 2012

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ResearchBlogging.org Williams BL, Hornig M, Parekh T, & Lipkin WI (2012). Application of novel PCR-based methods for detection, quantitation, and phylogenetic characterization of Sutterella species in intestinal biopsy samples from children with autism and gastrointestinal disturbances. mBio, 3 (1) PMID: 22233678