This is basically an update of my 2017 Allergy paper where I asked about sequelae of early vitamin D supplementation.
Two extensively examined hypotheses are the hygiene hypothesis (lack of protective bacterial exposure which leads to subsequent allergy) and the vitamin D hypothesis (early vitamin D supplementation sensitizes newborns against allergens) … The interesting question is: Are these concepts exclusive? … There is some preliminary evidence that – like many other environmental factors –vitamin D may modify the human microbiome.
Only yesterday a paper popped up during a presentation of Amelie Baud about the influence of social partners and the gut microbiome. This 2018 study tested gut microbial composition from 16S rRNA sequencing during the first year of life and subsequent risk of asthma in 690 participants
1-year-old children with an immature microbial composition have an increased risk of asthma at age 5 year … the microbial composition was not affected by maternal asthma status suggests that only susceptible children, exposed to inappropriate microbial stimulation during the first year of life, may express their inherited asthma risk …. The five most discriminating indicator OTUs for each cluster were identified for PAM cluster 1 as Enterobacteriaceae, Staphylococcus, Streptococcus, Bifidobacterium and Enterococcus, and for PAM cluster 2 as Faecalibacterium, Bacteroides(x3), and Anaerostipes … the risk of developing persistent asthma was increased (adjusted hazard ratio (aHR) 2.87 (1.25−6.55), P = 0.013) if the microbiome remained in PAM cluster 1 at age 1.
IMHO this doesn’t look very much like direct microbiome effects but some colliding factor. The authors discuss cesarean section-birth and antibiotics as relevant factors while I wonder why the last author (who is a known pro vitamin D lobbyist ) doesn’t take into account vitamin D here?
there was a significant association between community composition and vitamin D supplementation at the genus level. The vitamin D group had a higher abundance of genus Lachnospira, and lower abundance of genus Blautia (linear discriminate analysis >3.0). Moreover, individuals with 25(OH)D >75 nmol/L had a higher abundance of genus Coprococcus and lower abundance of genus Ruminococcus compared to those with 25(OH)D <50 nmol/L.
Vitamin D supplementation significantly increased gut microbial diversity. Specifically, the Bacteroidetes to Firmicutes ratio increased, along with the abundance of the health-promoting probiotic taxa Akkermansia and Bifidobacterium. Significant variations in the two-dominant genera, Bacteroides and Prevotella, indicated a variation in enterotypes following supplementation.
So is the microbiome just an indicator of vitamin D exposure in genetic susceptible children?
We had a major discussion before our 2010 paper where I argued that rare variants should have been included. Ten years after there is a nice paper using massive exome sequencing that finally includes them. The respiratory tract isn’t so much influenced by rare variants but there is a strong effect in the immune system.
And there is another interesting fact.
Surveying the contribution of rare variants to the genetic architecture of human disease through exome sequencing of 177,882 UK Biobank participants …if we look at the …. European population who are carriers of a filaggrin (FLG) PTV, we find those carriers have significantly higher risk for well-known associations, such as dermatitis … and asthma … Concomitant increases in vitamin D levels suggest risk of melanoma and basal cell carcinoma in FLG PTV carriers could be attributable to increased sensitivity to ultraviolet B radiation.
So far, I have only assumed some asthma/allergy priming effect of oral vitamin D in the newborn gut.
This something that I always avoided in human research – blaming genes for resistance to environmental stressors.
Nevertheless a Californian group (https://doi.org/10.1371/journal.pgen.1008528) now tested 101 mouse strains for lung resistance with exposure to diesel exhaust particles (DEP). After sensitizing the animals with dust mite and aluminium they could also test metacholine hyperreactivity (AHR).
Strains that exhibited the highest lung resistance after control exposure were not necessarily the same as those with high lung resistance after DEP exposure. It is unclear which strain was used for the consecutive GWAS. Did they put all mice into one cage for that?
The metacholine AHR GWAS results are not very impressive. And there seem to be also errors, as for example the lead SNP on chr 19 (rs51547574, near IL33) is shown with different allele frequencies in text and Fig 2. As the expression quantitative trait locus (eQTL) for Il33 is not in the lung, I think there is nothing to memorize here – IL33 is just a gatekeeper for surface integrity.
In a next step I wouldhave expected a GWAS for resistance change after DEP but FIG 3 only gives the result of Δ AHRDEP—AHRPBS data at an abitrary methacholine dose of 10mg/ml. The identifed locus could be interesting but as the LD there is rather high without any corresponding eQTL (I always wondered why there has never been a significance threshold for LD blocks, only for isolated SNPs?), the logic of the paper is broken here. Induction of lung resistance by DEP was significantly blunted in Dapp1-/- female mice? What about male Gm5105-/-, Mttp-/-, and Lamtor3-/- animals?
Hopefully nobody else will now try to find diesel, ozone, NOx resistance genes in humans as this is not a a scientific but a political issue…
Third, in PARSIFAL dust from children’s mattresses were collected by vacuuming — it is not very likely that many helminthic eggs were transported from stable to bedroom. In GABRIELA, only airborne dust samples were collected which again may miss helminth eggs although being certainly present in stable dust.
Fourth, more microbial exposure and more fungal taxa on farms are a trivial finding.
The inverse associations of the diversity scores with asthma were not confounded by status with respect to living on a farm because adjustment did not change the respective point estimates for asthma (Table 2), although the associations became nonsignificant.
Small sample size, borderline p-values even after a long fishing expedition?
What do these strange “probability” plots really show – the probability of asthma or the probability to live on a farm?
The plots are misleading if adjustment for farm living does not change the parameter estimates for bacterial/fungal diversity.
Sixth – even many years later, the main findings of this study have not been independently replicated. There is not any single study that shows listeriosis (Listeria) or diphtheria (Corynebacterium) to be protective.
The main arguments in favour of sharing work in its preliminary form are, firstly, that science works faster if work is made available sooner after it is completed and, secondly, that articles are improved by feedback from a wider group of readers, alongside formal peer review by a few experts. Simple estimates suggest that halving the delay to sharing a research result can double the speed at which research progresses. Ambitious research funders are now embracing preprints and other measures that aim to accelerate the pace of research.
MedArXiv will have a hard time attracting preprints if mainstream medical journal editors decide they won’t publish final versions of the papers. Currently, The BMJ and The Lancet are among the few medical journals that have explicitly said that posting a preprint doesn’t preclude publication; Nature and Science, which both occasionally publish medical studies, have the same policy. But at the JAMA Network, which publishes a dozen journals, the issue is hotly debated.
@medRxiv opened on June 6. So far they have only 304 followers on Twitter (and no allergy paper in the archive).
These reviews do not tell you so much about the regulation while regulation has recently elucidated by Gour et al. who describe a tropomyosin–dectin-1 interaction of the human host. Why is tropomyosin such a frequent target of human IgE?
Muscle protein tropomyosin is an important IgE target in a number of nematode infections; Onchocerca volvulus ; Ascaris lumbricoides; Anisakis simplex; and tropomyosin from the blood fluke Schistosoma mansoni is also a human IgE antigen. Tropomyosin is highly conserved across many invertebrates and is responsible for much of the IgE cross-reactivity between Ascaris and dust-mites.
I haven’t found any good answer to this question. As tropomyosin affects contractility – this seems like “shooting into the leg” of worms whenever they attempt to invade.
Maybe Gour et al. did not know the earlier dissertation from Berlin that already showed a reduced inflammation in the OVA mouse model by administration of recombinant tropomyosin.
The broad cross reactivity to tropomyosin gives rise to the question if helminth tropomyosin could induce allergic reactions to itself and/or tropomyosin of different organisms. Considering the fact that filarial nematodes express tropomyosin on their surface […] and that the continuing turnover of microfilariae confronts the host with relevant amounts of tropomyosin makes this question even more appropriate.
Worms seems to be attacked by anti-worm-surface-tropomyosin IgE whenever the worm tries to invade the epithelium during an acute infection. During invasion extracellular IL33 is cleaved into a shorter form with enhanced activity attracting more immune cells.
During chronic infestation nothing happens as long as the worm does not invade and doesn’t trigger any IL33 alarmin. As there is continuous tropomyosin antigen antigen contact, the host is slowly desensitzed, clearing IgE in favor of IgG4.
Is this also a model that explains allergy? We don’t know the details but maybe this antigen recognition / response system is being disturbed where allergens like Der p1 mimicking a worm infection by tropomyosin can trigger the allergic reaction in particular as Der p1 a cysteine protease also mimicks an invasion signal.
… association between serum 25-hydroxyvitamin D3 (25[OH]D3) levels and food allergy at age 1 year (338 challenge-proven food-allergic and 269 control participants) and age 2 years (55 participants with persistent and 50 participants with resolved food allergy)… Analyses were stratified by genotype at rs7041 as a proxy marker of DBP levels… Low serum 25(OH)D3 level (<50 nM/L) at age 1 years was associated with food allergy, particularly among infants with the GG genotype (odds ratio [OR], 6.0; 95% CI, 0.9-38.9) … Maternal antenatal vitamin D supplementation was associated with less food allergy, particularly in infants with the GT/TT genotype (OR, 0.10; 95% CI, 0.03-0.41)… This increases the biological plausibility of a role for vitamin D in the development of food allergy.
Maybe it would be helpful to have also “real” DBP levels for estimating bioavailability (and even data of supplement use) but already the reported results are another strong argument for the vitamin D – allergy axis. This is also largely in line with what I predicted back in 2012
Both vitamin D insufficiency and vitamin D supplementation have been linked to allergy and asthma. This apparent paradox is explained by epigenetic programming in pregnancy by low vitamin D levels and the excessive high supplementation in the newborn period.
Maybe I should have emphasized that genetic variants in the vitamin D pathway are also important for biological effects.
Home cleanliness resulted only in quantitative reduction of floor dust, which mainly indicates removal of superficial dirt with a rather cosmetic effect. Conventional cleaning does not eradicate microorganisms sustainably, because emptied microbial niches are instantly recolonized by ventilation and living carrier.
Maybe this is a difficult task – defining an agenda for future research. Here are some thoughts as we don’t know the reasons for the allergy epidemic even after 100 years of research. And we don’t have any cure yet, there is some relief of symptoms and there are some limited curative efforts but we don’t have any real understanding of what is going on. The following research areas may therefore be identified in NON-therapeutic research: Bullet points for future allergy research weiterlesen →
If you are writing some kind of online diary your mood is already surveilled by wefeelfine.
However, if you are an allergic patient, you may be interested in a new project of the German Pollenstiftung that runs an online pollen diary. We have pollen counts for a long time but we do not know so much about thresholds and individual variation. We feel good weiterlesen →
Just recently I came across a paper of David Marsh in 1992 on a major allergy gene “Fact or Fancy”. Many years later, the response is clear! Nevertheless the title remains popular at pubmed for reviews (N=42) – did they all read Asimov?