HLA alleles and specific language impairment

I've talked about the [almighty] major histocompatibility complex (MHC) before on this blog (see here). The important duties that this biological system performs in relation to identification and communication insofar as antigen presentation and importantly, the process of differentiation between 'self' and 'non-self' from an immunological perspective, are not to be sniffed at.

Harold? @ Wikipedia

I've found myself quite interested in all things MHC (also referring to the human leukocyte antigen, HLA, genes) from quite a few different perspectives. Be it with reference to the genetics of coeliac (celiac) disease (see here) or the very preliminary work being discussed on HERVs [human endogenous retroviruses], or rather HERV proteins, as being possible superantigens in relation to a condition such as myalgic encephalomyelitis (ME) (see here), there's lots to think about when it comes to the MHC.

So when I stumbled across the paper by Ron Nudel and colleagues [1] (open-access here) talking about "a possible role for HLA loci in language disorders" my attention was piqued. Before progressing into some of the details behind the Nudel paper, it's important to note the authorship team involved in this research paper. Alongside some quite well-known names attached to autism research (see here and see here for example), I was also interested to see Gillie Baird as one of the research team. Prof. Baird has impressed me in recent times; not only with her research involvement looking into the whole functional bowel issues in autism research (see here) but also with that recent 'leaky gut' paper with autism in mind (see here) which despite some methodological 'issues' gave me cause to smile that this area was at last starting to be taken seriously in more orthodox circles. Who knows, one day even the NICE guidance might recognise it as a potentially important comorbidity?

No mind, a few details from the Nudel paper are noteworthy, accepting that the paper is open-access:

• This was a multi-centre study looking at "the possible involvement of HLA loci in SLI [specific language impairment]". Loci by the way, is the plural of locus, and with genes in mind, refers to specific locations on a gene, DNA sequence or chromosome; a sort of area or postcode if you will. Participants were mostly derived from the SLIC (SLI consortium) groups with additional families included. All were assessed as having a SLI; all did not have autism, but some had comorbid features of ADHD and/or dyslexia. A control group was also included for some of the analyses.
• OK here's where is starts to get a little bit complicated. I found quite a nice website talking about the ways and means that HLA genes are indexed in terms of nomenclature. The complexity of the HLA genes and their molecules derives from the fact that HLA genes are highly polymorphic (see here). Regular readers might have heard me talk about SNPs (Single Nucleotide Polymorphisms) before reflecting single changes to the genetic alphabet. In the case of HLA genes it gets a little more complex (see here) and, as such, specific terminology has been introduced. I'll also draw your attention the description of an allele too (see here). 
• So, first researchers went looking for SNPs "across the HLA [genetic] region". Further, they then imputed HLA type from the SNP data to see if there was any connection between HLA type(s) and SLI or the specific parts of SLI from a psychometric point of view.
• Results: The HLA-A locus seemed to show a possible connection for "susceptibility to SLI". The A1 allele (HLA-A A1) in particular came out as the "most highly positively correlated allele". When it came to looking at SLI cases vs. controls, the "DR10 allele of HLA-DRB1 was more frequent in individuals with SLI than population controls". There are some other findings reported in terms of parental inheritance patterns but I'm going to leave those for now.
• The authors conclude that their preliminary data requires further study but: "provide an intriguing link to those described by previous studies of other neurodevelopmental disorders suggesting a possible role for HLA loci in language disorders".

I'm sure you can see why I was so interested in this paper. The bigger picture of the HLA (MHC if you prefer) being potentially implicated in something other than just immune function and all those 'self' and 'non-self' duties, opens up a whole new world of research. Given also my increasing interest in all things autoimmunity with an autism research slant, I'm minded to suggest that this may go some much further than anyone ever suspected [2]. That being said I would direct readers to the graphs showing the frequencies of alleles across the different HLA genes to see how aside from the HLA-DRB1 DR10 allele, this is more of a 'shades of grey' over and above 'there or not' pattern of findings when comparing SLI and non-SLI groups.

Looking back at some of the quite limited autism research in this area, I did find some clues that HLA involvement in SLI should perhaps not be totally unexpected as a function of the potential overlap between autism and SLI [3]. I say this acknowledging the debates are still on-going about the links or not between the two conditions and also that Nudel and colleagues ruled out autism as a diagnosis in their particular cohort. As an aside, readers might also find a recent post by Dorothy Bishop of interest, and in particular her model C for language development.

HLA alleles and autism? Well, you might say this is an emerging area in light of results like those from Mostafa and colleagues [4]. I dare say there may be other HLA overlap with other findings from autism research (see the open-access review from Torres and colleagues [5] for further reading). More recently I also stumbled across the paper by Al-Hakbany and colleagues [6] (open-access) which continued discussions about overlapping alleles (I'll probably formulate a separate post on that research soon).

The late Reed Warren also talked about the null allele of C4B [7] (see here for some more explanation on this) quite a few years back now, and as intimated in a past blog entry on his later work, reading disorders and ADHD actually turned up as being more relevant to the null allele than autism did (67%, 56% and 48% respectively). OK SLI is not necessarily reading disorder or ADHD, but as Nudel and colleagues noted there is a "high degree of co-occurrence for SLI and ADHD or dyslexia".

I think it's also important to recognise that those HLA types talked about in the Nudel study aren't just limited to behavioural or psychiatric conditions. I'm not going to go through the myriad of conditions and clinical findings related to the HLA alleles identified, but suffice to say that we perhaps need to look at a bigger picture when interpreting this data. This includes whether there may be other comorbidity present in those SLI cases - including somatic comorbidity - which might link into HLA genotype as per previous work looking at coeliac disease and ADHD for example (see here). SLI like autism like every other behavioural, developmental or psychiatric condition does not just exist in a diagnostic vacuum.

Still, I'll say again that this is a potentially very important paper which potentially opens up a whole new world of research...

Music. The life and times of Nelson Mandela will always remain in the public consciousness. I always fondly remember the Special AKA tribute to the great man.

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[1] Nudel R. et al. Associations of HLA alleles with specific language impairment. J Neurodev Disord. 2014 Jan 17;6(1):1.

[2] Choudhury N. & Benasich AA. A family aggregation study: the influence of family history and other risk factors on language development. J Speech Lang Hear Res. 2003 Apr;46(2):261-72.

[3] Bishop DV. Autism and specific language impairment: categorical distinction or continuum? Novartis Found Symp. 2003;251:213-26

[4] Mostafa GA. et al. The link between some alleles on human leukocyte antigen system and autism in children. J Neuroimmunol. 2013 Feb 15;255(1-2):70-4.

[5] Torres AR. et al. HLA Immune Function Genes in Autism. Autism Res Treat. 2012;2012:959073.

[6] Al-Hakbany M. et al. The Relationship of HLA Class I and II Alleles and Haplotypes with Autism: A Case Control Study. Autism Res Treat. 2014; 2014: 242048

[7] Warren RP. et al. Increased frequency of the null allele at the complement C4b locus in autism. Clin Exp Immunol. 1991 Mar;83(3):438-40.

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Nudel R, Simpson NH, Baird G, O Hare A, Conti-Ramsden G, Bolton PF, Hennessy ER, Monaco AP, Knight JC, Winney B, Fisher SE, & Newbury DF (2014). Associations of HLA alleles with specific language impairment. Journal of neurodevelopmental disorders, 6 (1) PMID: 24433325

HERVs and ADHD

HERVs. Human endogenous retroviruses. The remnants of our evolutionary struggle with the viruses of the times of our distant ancestors, now part and parcel of our modern-day genome. Yes, genetically, we are all part virus to various extents [so embrace your viral self].

HMS Beagle @ Wikipedia

I've talked HERVs on a few occasions on this blog, in relation both to the autism spectrum conditions (see here) and myalgic encephalomyelitis (ME) (see here).

Without getting too technical, the crux of those posts was to suggest that although those bits of virus in our genomes are not necessarily 'active viruses' (i.e. not able to produce infectious virus or replicate) they may have implications for things like autoimmunity given that HERV proteins are supposedly recognised as 'self' by the almighty MHC [1] and seem to be able to provoke autoimmunity (in mice) [2]. That and the fact that the expression of HERVs may be kept in check by epigenetic means (methylation) [3] and 'hypomethylation [of DNA] = more genomic instability' [4] so, theoretically under certain circumstances could mean HERVs get a chance to start expressing (something). Or that's the theory (I think)...

With all that in mind, I move to the paper by Balestrieri and colleagues [5] (yes, the same group who completed the HERV paper with autism in mind) who discussed some very preliminary data on the expression of certain families of HERVs. Indeed, they reported: "The expression levels of HERV-H are significantly higher in patients with ADHD [attention-deficit hyperactivity disorder] compared to healthy controls".

I can't pretend to know all the ins-and-outs of how one goes about assaying for the expression of HERVs - "expression of retroviral mRNAs from the three HERV families was evaluated in peripheral blood mononuclear cells (PBMCs)" apparently. It was however interesting to see that HERV-H 'over-expression' was "significantly higher in patients with ADHD compared to healthy controls". HERV-H was also the same family reported to be 'more abundantly expressed' in cases of autism.

A search of some of the literature covering HERV-H reveals that it is a gamma-retrovirus (yes, similar to those letters X-M-R-V and that de-discovery issue). In terms of associations and roles, it "contributes to pluripotency in human cells" according to the paper by Santoni and colleagues [6] and their finding of high levels of HERV-H RNA in human embryonic stem cells. The HERV-H family have also been suggested to have immunosuppressive properties [7].

HERV-H has been linked to conditions such as multiple sclerosis as per papers like this one by Christensen [8] which also hinted at how other viruses may 'interact' with HERVs; in that paper concluding that: "retroviruses and herpes viruses have complex interactions". That being said, not all results have arrived at the same conclusion.

I was also particularly interested to read the paper by Shuvarikov and colleagues [9] who seemed to suggest "HERV-H elements as a mechanism of deletion formation", as in genetic deletions. I might be making mountains out of molehills but their case report that HERV-H elements seemed to flank "recurrent, 3.4-Mb, de novo deletions of 3q13.2-q13.31" could potentially lead down some very important paths as intimated in a previous post. The fact that they mention autism as being part and parcel of some of their participant group description is likewise intriguing.  As I've indicated in other posts on this blog where the term 'de novo' has been used, the uncertainty or chance finding of de novo now, might not be so in X numbers of years time. And the future may already be here [10] with schizophrenia in mind.

I'm going to stop there with this quite heavy going post and the chatter about HERVs and ADHD (or autism or anything else). Science is to quite a large extent still feeling it's way around the HERVs and their role - if any - in health and wellbeing. The reported link between the expression of HERVs and a condition as complicated as ADHD needs a lot more work on it before anyone can arrive at any firm conclusions. That being said, I find this to be a fascinating area of science which really does add a new layer of complexity to the whole genetics-environment relationship.

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[1] Lavie L. et al. CpG Methylation Directly Regulates Transcriptional Activity of the Human Endogenous Retrovirus Family HERV-K(HML-2). J. Virol. 2005; 79: 876-883

[2] Perron H. et al. Human Endogenous Retrovirus Protein Activates Innate Immunity and Promotes Experimental Allergic Encephalomyelitis in Mice. PLoS ONE 8(12): e80128. doi:10.1371/journal.pone.0080128

[3] Wilson AS. et al. DNA hypomethylation and human diseases. Biochimica et Biophysica Acta. 2007; 1775: 138–162.

[4] Tugnet N. et al. Human Endogenous Retroviruses (HERVs) and Autoimmune Rheumatic Disease: Is There a Link? Open Rheumatol J. 2013; 7: 13–21.

[5] Balestrieri E. et al. Human endogenous retroviruses and ADHD. World J Biol Psychiatry. 2013 Nov 28. [Epub ahead of print]

[6] Santoni FA. et al. HERV-H RNA is abundant in human embryonic stem cells and a precise marker for pluripotency. Retrovirology. 2012; 9: 111.

[7] Mangeney M. et al. The full-length envelope of an HERV-H human endogenous retrovirus has immunosuppressive properties. J General Virology. 2001; 82: 2515-2518.

[8] Christensen T. Association of human endogenous retroviruses with multiple sclerosis and possible interactions with herpes viruses. Rev Med Virol. 2005 May-Jun;15(3):179-211.

[9] Shuvarikov A. et al. Recurrent HERV-H-Mediated 3q13.2-q13.31 Deletions Cause a Syndrome of Hypotonia and Motor, Language, and Cognitive Delays. Hum Mutat. 2013 Oct;34(10):1415-23.

[10] Bundo M. et al. Increased L1 Retrotransposition in the Neuronal Genome in Schizophrenia. Neuron. 2014. 2 Jan.

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Balestrieri E, Pitzianti M, Matteucci C, D'Agati E, Sorrentino R, Baratta A, Caterina R, Zenobi R, Curatolo P, Garaci E, Sinibaldi-Vallebona P, & Pasini A (2013). Human endogenous retroviruses and ADHD. The world journal of biological psychiatry : the official journal of the World Federation of Societies of Biological Psychiatry PMID: 24286278

Coeliac Disease - a training post

You're probably wondering why, with all the reams of autism research being produced every day, that I'm dedicating a post to describing coeliac (celiac) disease on this blog? Well, the answer is simple; I've talked about coeliac disease (CD) quite a bit in relation to autism (here) and schizophrenia (here) and other conditions (here) but I'm mindful that not everyone actually knows what it is or what we think we currently know about it.

Gluten @ Wikipedia  

So in future occasions when I talk about CD in relation to some wonderful new study, I've got this training post as mine and yours go-to reference for the condition.

If you want the long and complicated story of CD, there are plenty of peer-reviewed papers which I could suggest you read such as this one from Kagnoff* (open-access) or this one from Meresse and colleagues** (open-access). There are lots of other papers on the topic too but if you want the Mr Men version, read on.

Gluten protein and peptides
CD is a condition governed by genes and environment in pretty equal measure. I suppose it all starts with foods containing the protein gluten. Actually gluten is a bit of a catch-all word because it combines two types of protein: gliadin and glutenin. Gluten is a protein which consists of long chains of amino acids. When ingested, various enzymes go to work on chopping up the protein into those nutritious rich amino acids that our bodies so rely on. But digestion does not just see the gluten protein immediately exploded into its constituent amino acids but rather breaking the protein down chunk by chuck to form small chains of amino acids called peptides along with way.

If you're a follower of autism research and in particular the whole gluten- and casein-free dietary intervention thing, you'll probably have heard about peptides as per the opioid-excess theory*** (open-access) put forward as one explanation for why diet might 'work' for some on the autism spectrum. It's still a little bit contentious but that's perhaps a topic for another day.

Anyhow, gluten is not an easy protein to digest as per the presence of certain amino acids such as glutamine and proline in that protein chain, the chemistry of which don't like being degraded easily. So what you potentially get are quite a few peptides swimming around our gastrointestinal (GI) tract which are not completely degraded into their simplest building block form, the amino acids.

Gut access
These gluten, sorry gliadin, peptides however don't just stay in the gut; some of them are also able to gain access to a part of the gut barrier called the lamina propria. Once there, something rather interesting seems to happen in cases of CD. The peptides come across something called tissue transglutaminase (tTG) something else which has cropped up on this blog with autism in mind (see here). The clue is in the name about tTG (also called TG2) and what it can do: -ase means it's an enzyme and the glutaminase bit means that it does things to the amino acid glutamine. The specific duty it does is a process called deamidation which basically involves the conversion of glutamine to glutamic acid (otherwise known as glutamate). Without getting too much into the chemistry of this process, the newly deamidated gliadin peptide is now 'super-charged' (neutral into negatively charged amino acids) in terms of its attraction (binding affinity) to molecules of the almighty MHC - major histocompatability complex or HLA in humans (see here).

DQ2 and DQ8
OK, so a quick recap. Gluten protein digested into gluten peptides. Said peptides meet and greet tTG and funny things start to happen to them.

Next in the process chain of CD is how these newly enhanced peptides from an immunogenicity point of view are met by the cells of the MHC and the sparks that fly as a result. Just in case you didn't click on my link talking about the MHC, it's all about how things are presented to the immune system and in particular, the tricky task of making sure that 'self' is not confused with 'other' by the immune system.

The genetics of CD represent the important part of this next stage of proceedings as per the HLA-DQ2 and DQ8 heterodimers; in effect the genes of CD. It's all about inheritance patterns as to whether or not a person will have two or one or no copies of these genes as a consequence of genetic zygosity.

HLA DQ2 or DQ8 molecules are part of the antigen presenting cells (APCs). Those newly enhanced gluten peptides fit nicely into the 'pocket' of the DQ2 and/or DQ8 molecules and once there activate T cells or more specifically a Th1 CD4+ response**** (open-access) focused on gliadin. This eventually leads to the release of cytokines such as IFN-γ (see here also) and TNF which then go on to damage the gut mucosa as a function of their important role in the process of inflammation.

This is quite a simplistic overview of the main processes involved in CD. As per the discussions on the Kagnoff and Meresse papers, there are still quite a few unknowns about the whole process of CD. There's also the relatively newer work coming into the science of CD such as a role for zonulin (see this post) and its 'gatekeeper' role in relation to the gut barrier and things like the wheat amylase trypsin inhibitors (thanks Jad).

The gluten-free diet
As you'll probably already know, management of CD is primarily via the use of a gluten-free diet. The theory being that if there is still no starting material (gluten) to form those peptides, even though the genetics may be there, there is nothing or only little material for tTG or the DQ2/DQ8 molecules to go to work on.

That being said, you'll probably also see a few other potential areas where other interventions might also be developed***** (open-access). So how about helping to degrade those gluten peptides? What about stopping those peptides from meeting tTG? Blocking DQ8 and DQ2 molecules? Or even reducing the release or blocking the effects of those cytokines? And the good things is that research is underway in some of these areas.

Testing for coeliac disease
Just before you go it might also be worthwhile mentioning about how one goes about testing for CD in light of some confusion in this area over the years. It's worth pointing out that an accurate diagnosis of CD relies on more than one test (see here) covering serology, gut biopsy and on occasion, genetic testing. One of the more recent professional consensus statements on testing can be seen here****** (open-access).

And finally.... please don't take my word for it, do some research yourself.

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* Kagnoff MF. Celiac disease: pathogenesis of a model immunogenetic disease. J Clin Invest. 2007 Jan;117(1):41-9.

** Meresse B. et al. Celiac disease: from oral tolerance to intestinal inflammation, autoimmunity and lymphomagenesis. Mucosal Immunol. 2009 Jan;2(1):8-23. doi: 10.1038/mi.2008.75.

*** Whiteley P. et al. How Could a Gluten- and Casein-Free Diet Ameliorate Symptoms Associated with Autism Spectrum Conditions? Autism Insights 2010:2 39-53.

**** Nilsen EM. et al. Gluten induces an intestinal cytokine response strongly dominated by interferon gamma in patients with celiac disease. Gastroenterology 1999; 115: 551-563.

***** Bakshi A. et al. Emerging Therapeutic Options for Celiac Disease: Potential Alternatives to a Gluten-Free Diet. Gastroenterol Hepatol (N Y). 2012 Sep;8(9):582-588.

****** Husby S. et al. European Society for Pediatric Gastroenterology, Hepatology, and Nutrition Guidelines for the Diagnosis of Coeliac Disease. JPGN. 2012; 54: 136-160.

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Meresse B, Ripoche J, Heyman M, & Cerf-Bensussan N (2009). Celiac disease: from oral tolerance to intestinal inflammation, autoimmunity and lymphomagenesis. Mucosal immunology, 2 (1), 8-23 PMID: 19079330

Immune reactivity to gluten in autism

When I first saw the paper from Nga Lau and colleagues* (open-access) looking for markers of gluten sensitivity and/or coeliac (celiac) disease in children with autism I have to admit to raising a smile. I smiled because in a previous post on this blog I talked about a 'wish-list' for autism research specifically focused on the gluten and casein-free dietary intervention**. Part of that wish list was some further inquiry into why, biochemically, some people on the autism spectrum might benefit from dietary intervention. My prayers it seems have started to be answered.

Smiler @ Wikipedia  

When it comes to the area of dietary intervention for conditions like schizophrenia (no really), there seemed to be a lot more enthusiasm for looking at why some cases of schizophrenia might overlap with dietary issues over investigations into autism. I can't pretend to know why schizophrenia research took the lead; maybe something to do with Dohan and his original discussions on diet and schizophrenia or that schizophrenia research has some very talented people like Emily Severance and colleagues (see here and here and here) taking an interest. One might also speculate that some of the politics of autism - diet, gastrointestinal (GI) issues = (see here) - might also creep into this lack of autism research interest too? Who knows.

No mind, Lau et al did look at immune reactivity to gluten (or rather a fraction of gluten called gliadin) in a group of children with autism (n=37) compared with their asymptomatic siblings (n=27) and typically developing controls (n=76). They looked for anti-gliadin antibodies (IgA and IgG). They looked for antibodies to deamidated gliadin (that is where gliadin has already been subjected to some kind of enzymatic modification). They looked at antibodies to tissue transglutaminase (tTG). They even examined HLA genotype for the DQ2 and DQ8 haplotypes (linked to the genetics of coeliac disease). All in all, the primary bases were covered.

Results: well, the serum samples all came from AGRE - the Autism Genetic Resource Exchange - so no quibbling about the diagnosis of autism. They also subdivided the autism group up into those with GI symptoms and those without and remarked on those who were following a gluten-free diet too.

The authors report that levels of IgG anti-gliadin antibody were elevated in the autism group compared to siblings and controls. This differences lasted even when certain confounders such as age, gender and race were taken into account and the calculated odds ratio of an having an elevated IgG antibody levels to gliadin was not to be sniffed at either (OR 4.97; CI 1.39 - 17.8). That being said, there was cross-over between the relatively small participant groups and levels of IgA antibody to gliadin were not significantly different between the groups. Very interestingly, the presence of comorbid GI symptoms appearing alongside autism seemed to be linked to that elevated IgG antibody response to gliadin compared with no comorbid GI symptoms.

Just short of 50% of the children with autism were "positive for HLA-DQ2 and/or -DQ8 (6 DQ2, 12 DQ8)". I probably didn't explain this well, but a significant proportion of people with coeliac disease carry these haplotypes which all relates back to the almighty MHC and antigen presentation (see here for explanation).

Insofar as the other parameters on antibodies to deamidated gliadin and tTG, there was little difference to write home about. Although not wholly relevant, I'll refer you back to some interesting work down on tTG with autism in mind from a while back (see here).

A few choice quotes from the authors: "The findings indicate that the observed anti-gliadin immune response in patients with autism is likely to involve a mechanism that is distinct from celiac disease, without the requirement for TG2 activity or antigen presentation through DQ2/DQ8 MHC molecules". Well, we know that coeliac disease, when it is tested for in cases of autism, is probably not greatly over-represented in ASD despite some interesting evidence (see here). The Lau study kinda confirms that fact. But.... with all the talk about non-coeliac gluten sensitivity which has surfaced over the past few years (see here and here) one has to wonder whether for some on the autism spectrum, a similar mode of action might pertain outside of the more classical coeliac serology and markers?

It's interesting also that the authors talk about issues like the potential cross-reactivity of gluten as one implication of their findings. I'm taken back to the work of Ari Vojdani and colleagues*** on this matter. Oh and those Emily Severance findings about critters like T.gondii mixing it up with gluten reactivity (see here). I'm not necessarily saying that everyone with autism who presents with gluten antibodies has been in contact with the gondii but merely that the infection connection is an interesting one as per all that autoimmunity chatter with autism in mind.

It's interesting too that the authors also make mention of intestinal permeability as potentially being a factor to be looked at further. I know some people still look on things like 'leaky gut' as being the stuff of tree-huggers, but the evidence is growing for some effect in cases of autism (see here) with the promise of more investigations to come (see here for the Paul Patterson mouse work and here for a video from everyone's favourite autism - gut specialist researcher, Alessio Fasano).

Whilst I am pretty buoyed by seeing that this area is starting to get some research interest, I'm containing my excitement for now. It's still a long haul from gluten antibodies to suggesting that gluten may 'cause' or 'exacerbate' a complex set of conditions like the autisms even with all that gut-brain chatter which I'm certainly guilty of elevating. But due credit where it is deserved, at least Lau and colleagues have started asking some questions about this interesting area of autism research and the potential links with diet....

To finish, how about a song about Alejandro? (something for everyone in that video...)

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* Lau NM. et al. Markers of Celiac Disease and Gluten Sensitivity in Children with Autism. PLoS ONE 8(6): e66155. doi:10.1371/journal.pone.0066155

** Whiteley P. et al. Gluten- and casein-free dietary intervention for autism spectrum conditions. Front Hum Neurosci. 2013; 6: 344.

*** Vojdani A. et al. Immune response to dietary proteins, gliadin and cerebellar peptides in children with autism. Nutr Neurosci. 2004 Jun;7(3):151-61.

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Lau, N., Green, P., Taylor, A., Hellberg, D., Ajamian, M., Tan, C., Kosofsky, B., Higgins, J., Rajadhyaksha, A., & Alaedini, A. (2013). Markers of Celiac Disease and Gluten Sensitivity in Children with Autism PLoS ONE, 8 (6) DOI: 10.1371/journal.pone.0066155

Myalgic encephalomyelitis (ME) and HERVs

Viruses. Apparently there are quite a lot of them on this old rock we call home and I've started to become quite interested in some of them, or at least how we as a species have, and continue to interact with them down the ages.

I must start by thanking Natasa for bringing me into contact with the paper by Kenny De Meirleir and colleagues* (open-access) looking at human endogenous retrovirus (HERV) expression in a small cohort of patients diagnosed with myalgic encephalomyelitis (ME). I'm going to try and talk about this potentially quite important paper as best I can, bearing in mind my considerable non-expertise in all things HERVs and indeed, ME. And just in case you want another viewpoint on this study, the article by Joel (Snowathlete) is pretty good.

Voyage of Discovery @ Wikipedia  

OK, so HERVs. Think ghosts of viruses past, bits of which are communicated down the generations and comprise a very surprising 8% of the human genome. I've talked about HERVs before with autism and schizophrenia in mind (see this post) and the involvement of epigenetic means in keeping HERVs in some kind of check. Consider this post a bit of an extension of that discussion albeit with ME in mind. Consider also how some of the De Meirleir results might also be potentially investigated with autism and schizophrenia in mind.

Before progressing to the findings, the first thing that struck me about this paper is its point of origin: the Whittemore Peterson Institute. While this name probably means very little to many people, those with a particular interest in ME (and Chronic Fatigue Syndrome, CFS) will perhaps know about some of the recent history which included the WPI, and those magic letters X-M-R-V (see this post). I might add that this point should not in any way, shape or form alter or affect the findings or conclusions offered by De Meirleir et al. This is peer-reviewed stand-alone science. And science is after all [mostly] self-correcting; the XMRV story is quite a good example of that.

So back to the paper, and a very quick summary:

• The proposed connection between HERV expression in various conditions with an 'autoimmune' element** (systemic lupus erythematosus, SLE for example) led the authors to look at the expression of HERV proteins in gastrointestinal biopsies taken from 12 participants diagnosed with ME compared with those from 8 asymptomatic (at least for ME) control participants.
• Punch biopsies came from the stomach and duodenum and were analysed for "the presence of HERV and gamma-retroviral Env and Gag proteins" based on immunohistochemistry.
• Results: well alongside "the presence of substantial disruption of gut microbiota composition" in all ME cases (dysbiosis to you and me) and "a lympho-plasmatic infiltrate in the submucosa in all specimens"(question?), 8 of the 12 duodenal samples from participants with ME were immunoreactive to antibodies "raised against HERV proteins" compared with none of the controls. 
• Another quite important quote from the paper: "These observations suggest that the presence of the HERV protein in pDC's [plasmacytoid dendritic cells] may be associated with a pathological manifestation in at least a subset of individuals with ME".

I've probably not done justice to the final paper and the work that went into producing it with such a short summary. Nonetheless, I find these to be some quite exciting preliminary findings for quite a few reasons. I should point out that HERVs are seemingly becoming quite fashionable where ME and CFS are concerned as evidenced by the paper from Oakes and colleagues. I'll maybe come back to their findings on HERV-K in a later post.

Back to the De Meirleir paper and a few comments...

First is the suggestion that words like 'autoimmunity', 'antigen-presentation', 'inflammation' and 'gastrointestinal' might actually be part and parcel of the pathology of at least some cases of ME or at the very least, significant comorbidity. Accepting the continuing issue of definition and criteria for definition when it comes to ME (and CFS), and that there is still lots of debate as to what the underlying causes of ME might be and best treatment options are, I find myself drawn back to some of the work done in autism research; particularly that connected to the almighty MHC. Without going over already trodden ground, the MHC is perhaps best described as the way the body tells the immune system what is self and what is a foreign contaminant (to borrow a phrase from Disney's WALL-E). I note for example that MHC class II antigens have been talked about before, at least in CFS, as per the paper by Smith and colleagues*** (open-access).

As Meirleir points out, HERV proteins should normally be treated as 'self' by the MHC. They speculate however that several elements combine: (i) "Inflammation is known to increase HERV expression", (ii) "some HERV proteins act as superantigens", (iii) "pDCs are most remarkable for their ability to produce copious amount of type-1 IFN" and how an issues with pDC response might impact on interferon production with some potentially important knock-on effects****. Perhaps some food for thought?

Next is the possibility of a relationship between ME and that bright new discipline of epigenetics, bearing in mind the concept of jumping genes and the mantra: hypomethylation = more genomic instability with the connection back to HERVs. I should caution that nothing is specifically mentioned about epigenetics in the De Meirleir paper given their focus on identifying immunoreactivity to HERV protein in cases. Indeed I was very surprised to see that a PubMed search of the keywords 'myalgic encephalomyelitis and epigenetics' showed only 2 hits (20/02/13). An unexplored area if ever there was one....

Finally, I can't end this post without referencing the gut bacteria findings and indeed the fact that "Gastritis (mainly antritis) was present in all cases". Some years ago, two colleagues of mine speculated that within the spectrum of ME/CFS there seemed to be two primary phenotypes: one where symptoms appeared to coincide with gastrointestinal (GI) issues; another with a more neurological presentation - the word 'brain fog' seemed to be quite a well-used description. Now I'm not saying that these categorisations are entirely accurate, but certainly the GI symptoms element does seem to cropping up in quite a bit of the ME/CFS literature as for example in the paper by Clark and colleagues***** (full-text) on reports of things like childhood gastrointestinal symptoms potentially being risk factors for a diagnosis. Indeed, the overview provided by Lakhan & Kirchgessner****** (full-text) on gut inflammation and CFS covers quite a lot of the material in this area and again, a call for quite a bit more research to be done too.

The De Meirleir paper, whilst small in participant numbers and preliminary in nature is an interesting one; of that there is no doubt. The next stage of the HERV-ME journey - learning the lessons of XMRV - is independent replication with the appropriate statistical power and relevant control groups (fibromyalgia and various other autoimmune related conditions for example) and then, depending on those results, the real adventure can begin.

But also I would caution that we not forget all the other areas of potential importance to ME and CFS... (see here and here and here and here) in our prospective new-found fixation with HERVs and ME.

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* De Meirleir KL. et al. Plasmacytoid dendritic cells in the duodenum of individuals diagnosed with myalgic encephalomyelitis are uniquely immunoreactive to antibodies to human endogenous retroviral proteins. In Vivo. 2013; 27: 177-187.

** Balada E. et al. Molecular mechanisms mediated by human endogenous retroviruses (HERVs) in autoimmunity. Rev Med Virol. 2009; 19: 273-286.

*** Smith J. et al. Association of chronic fatigue syndrome with human leucocyte antigen class II alleles. J Clin Pathol. 2005; 58: 860–863.

**** Martinet J. et al. Altered functions of plasmacytoid dendritic cells and reduced cytolytic activity of natural killer cells in patients with chronic HBV infection. Gastroenterology. 2012; 143: 1586-1596.

***** Clark C. et al. Premorbid risk markers for chronic fatigue syndrome in the 1958 British birth cohort. Br J Psychiatr. August 2011.

****** Lakhan SE. & Kirchgessner A. Gut inflammation in chronic fatigue syndrome. Nutr Metab (Lond). 2010; 7: 79.

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KENNY L. DE MEIRLEIR, SVETLANA F. KHAIBOULLINA, MARC FRÉMONT, JAN HULSTAERT, ALBERT A. RIZVANOV, ANDRÁS PALOTÁS, & VINCENT C. LOMBARDI (2013). Plasmacytoid dendritic cells in the duodenum of individuals diagnosed with myalgic encephalomyelitis are uniquely immunoreactive to antibodies to human endogenous retroviral proteins In Vivo, 27 (2), 177-187

The major histocompatibility complex and autism

Fancy a beer son? @Lucasfilm

"Your destiny lies with me Skywalker". So said Darth Vader as he tried his very best to work on his father-son relationship skills (shortly after chopping off his son's hand).

I don't necessarily see it as my destiny to keep talking about the immune system in connection to autism and other conditions but there was perhaps an air of inevitability that I would eventually end up talking about the major histocompatibility complex (MHC) and autism. Indeed two quite recent papers by Needleman & McAllister* and Torres and colleagues** (full-text) bring the MHC into full view with autism in mind.

What is the MHC?

It's all about identification and communication. In effect the very flexible MHC lets the immune system know what is 'self' and what is 'other' by promoting 'self' peptides on the surface of all cells. This means that when 'other', foreign peptides from an invading pathogen are presented on some cells by the MHC, the immune system knows that these are not-self and acts accordingly. So lymphocyte recognition and the presentation of antigens represent two quite big tasks of the cell-surface molecules which make up the MHC (also called the human leukocyte antigen). When things go wrong with the MHC and 'self' gets confused with 'other' you get autoimmunity; something which has been speculatively linked to some cases of autism (see here).

"Always two there are" (well two main ones).

Two classes of MHC molecules play a big role, MHC class I and MHC class II although there are others; all genetically encoded for on various regions of chromosome 6. I don't really want to get too bogged down by structure and different chains between the two classes but if you want a good review have a look at this paper by Hewitt*** (full-text) and this paper by Wang and colleagues**** (full-text). A big difference seems to be where each class of glycoprotein is found; MHC class I are present on most cells in the body, MHC class II glycoproteins are only found on antigen-presenting cells such as T cells and B cells. That and the different types of 'antigen' being presented (endogenous vs. exogenous) and to what (cytotoxic T cells vs. helper T cells) respectively.

Involvement of the MHC with regards to health and ill-health is never more prominent than in the example of coeliac (celiac) disease (CD). There, CD is strongly associated with the the presentation of specific genetic alleles of the MHC known as the (HLA) DQ2 and DQ8 haplotypes (see here for a description of haplotypes). This page is about a good an explanation that there is showing how HLA DQ2 and DQ8 fit into CD; the watchwords are: glutamine and prolamin rich gluten peptides, binding to HLA DQ2 / DQ8 haplotypes, initiation of an inflammatory response, tissue damage, flat mucosa and so forth.

Assuming that I've understood and conveyed all that information accurately, the next step is to discuss where autism may (or may not) fit into the MHC story.

And autism?

If I said that the late Reed Warren was there pretty much at the beginning when it comes to looking at the MHC in cases of autism would you be surprised? Indeed if ever there was a loss to autism research, it was the fact that Dr Warren passed away far too soon leaving us all wondering what he might have accomplished had he still be on the scene.

I've posted previously about his work on the C4B null allele (here) and more recently on his IgA deficiency findings in cases of autism (here). His paper from 1992***** suggested, quote: "a gene related to, or included in, the extended major histocompatibility complex may be associated with autism". In later work, Warren together with another big name in the immune side of autism Vijendra Singh, even talked about a possible association between issues with the MHC in autism and elevations in levels of serotonin (here******). Indeed Singh still holds some scientific interest with his notion of 'autoimmune autistic disorder'.

So what did Warren and colleagues find? Well it all boils down to quite a few cases of autism presenting with the "extended or ancestral haplotype B44-SC30-DR4". That and similar findings being reported in first-degree relatives as per this study by Lee and colleagues******* and this study by Johnson and colleagues********. I interpret this as meaning that within the class II MHC - the one involved in presenting exogenous (outside-derived) antigens from bacteria and such like - where the HLA-DR4 haplotype features, cases of autism might show a link. Bear in mind also, that HLA-DR4 is also a risk factor for conditions such as type 1 diabetes (see here) thus extending the autoimmune side of things too. 

I assume you are perhaps wondering where all this MHC talk is going when it comes to a behaviourally defined condition like autism outside of just autoimmunity. Well, this is where the tie up between the immune system and other organs like the brain come into their own and the suggestion that MHC molecules might do much more than just offer antigens to the immune system. Wekerle********* (full-text) provides an excellent overview of the MHC with neurons in mind, reviewing the suggestion that the MHC may regulate important processes like synaptic pruning.

Indeed with plasticity and pruning in mind, Belmonte and colleagues********** (full-text) talked about the possibility that a decreased expression of class 1 MHC molecules may impair pruning in cases of autism, pertinent to the early brain 'overgrowth' noted in some cases. There is also another potential side to the MHC story in autism as per the suggestion of  "an increased proportion of MHC class II-expressing microglia" at least in a mouse model of autism; indeed a mouse model already covered on this blog. I'm not however going any further with this at this time but would refer you to a recent post on microglia and autism.

Based on all this and other research, I'd like to think that there is a case for involvement of the MHC at least in some cases of autism. I can't really offer a sound explanation as to the how and why outside of speculation on things like the autoimmunity comorbidity or possibly some contribution from maternal infection during pregnancy (on the basis of the familial MHC connection) as being involved. All I can say is that there is some degree of likelihood of MHC involvement at least for some diagnosed with autism. Perhaps another potential research avenue in need of further investigation?

To end, readers in the UK whether interested or not, will have probably heard about the departure of Chris Moyles from BBC Radio 1. I'm more of a Radio 2 man myself (particularly when Ask Elvis is on) but Chris Moyles played some good tunes on Friday to bow out to, one of which I always really enjoyed in a melancholic way ... The Streets and Dry your eyes. 

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* Needleman LA. & McAllister AK. The major histocompatibility complex and autism spectrum disorder. Developmental Neurobiology. July 2012.
DOI: 10.1002/dneu.22046

** Torres AR. et al. HLA immune function genes in autism. Autism Research & Treatment. 2012; 959073.

*** Hewitt E. The MHC class I antigen presentation pathway: strategies for viral immune evasion. Immunology. 2003; 110: 163-169.

**** Wang P. et al. A Systematic Assessment of MHC Class II Peptide Binding Predictions and Evaluation of a Consensus Approach. PLoS Computational Biology. 2008; 4: e1000048.

***** Warren R. et al. Possible association of the extended MHC haplotype B44-SC30-DR4 with autism. Immunogenetics. 1992; 36: 203-207.

****** Warren RP. & Singh VK. Elevated serotonin levels in autism: association with the major histocompatibility complex. Neuropsychobiology. 1996; 34: 72-75.

******* Lee LC. et al. HLA-DR4 in families with autism. Pediatric Neurology. 2006; 35: 303-307.

******** Johnson WG. et al. HLA-DR4 as a risk allele for autism acting in mothers of probands possibly during pregnancy. Archives of Pediatrics & Adolescent Medicine. 2009; 163: 542-546.

********* Wekerle H. Planting and pruning in the brain: MHC antigens involved in synaptic plasticity? PNAS. 2005; 102: 3-4.

********** Belmonte MK. et al. Autism and abnormal development of brain connectivity. The Journal of Neuroscience. 2004; 24: 9228-9231.