Review article

INTRODUCTION

The most effective treatment of coeliac disease (CD) is a rigorous, lifelong gluten free diet (GFD). Foods not allowed in GFD include all products containing wheat, rye, barley. The harmful effects are caused by gliadin fraction of wheat gluten and similar prolamines of rye (secalins) and barley (hordeins). Patients should be warned that some medications, as well as certain vitamin and mineral supplements, may also contain gluten as an inactive ingredient. Untreated CD can result in malapsorption, anaemia, vitamine deficiencies, osteoporosis, malignancy, short stature in children, etc. A question very commonly posed is: whether there is a safe threshold for gluten consumption in CD patients which will not result in inflicting any damage on small bowel mucosa. In reality there is no scientifically determined answer whatsoever (1). The reason for this fact lies in the extremely variable tolerance among CD patients. Therefore, every possible effort should be made to preserve coeliac patients diet as gluten-free as possible (2). Although found to be most effective, GFD is difficult to comply with and it certainly adds up to a household monthly expenditure. Some gluten-free products are relatively unpalatable which may lead to poor compliance or inadvertent gluten ingestion. Regarding this as an undeniable fact, there are increasing demands to modify GFD and make it more tolerable to patients (3). Recent researches constantly being done have been brought about by the growing interest in the alternative forms of therapy.

IS LABEL “GLUTEN-FREE” EVERYWHERE REAL?

Products labeled as being gluten-free (instant food for infants, flours, breads, biscuits, “pastes”) made by domestic manufacturers are scarce at Serbian market. Most of gluten-free products are mainly imported from Germany, Finland and Hungary. Such sorts of food available at our market, regardless of their being domestic or foreign, are totally devoid of any gluten and are based on naturally gluten-free products such as: maize, rice, soya, potato and broccoli. In the United Kingdom, Sweden and Finland gluten-free products based on wheat starch may still contain some trace amounts of gluten. They have been successfully used in CD therapy and their compliance has been proved to be good in the majority of CD patients (4,5,6). However, the safe amount of gluten in these products labeled as gluten-free remained undetermined since there is no existing reliable method capable of measuring such scarce gluten amounts. Due to this fact, wheat starch products are not recommended by CD societies in southern Europe, United States and Canada (2,7).

A new test capable of detecting small amounts of gluten in food has recently been put into practice. Valdes et al. have introduced a novel sandwich ELISA test [based on prolamin toxic epitope Q glutamine P proline F phenylalanine (QQPFP) detection by monoclonal antibodies]. This test in combination with a new gluten extraction procedure can detect very low levels of gluten (equal to 3.2ppm=mg/kg) in wheat, ray and barley (8). This highly specific and sensitive test has been used by some Finnish researches in their study in adults, thus recommending that the safe gluten contamination threshold can be set at 100ppm (9). Provided that daily flour intake is 300g a level of 100ppm corresponds to 30mg daily gluten consumption. Differences in histology, serology and life quality between groups of patients treated with naturally gluten-free and wheat starch based products over the period of 1 to 10 years were not found. The Codex Alimentarius Comission of the World Health Organization had previously suggested that gluten-free products should not contain more than 200ppm of gluten (10).

Cross-contamination of naturally gluten-free products with toxic cereals can be one of the problems in practical dietary management (7). It can happen during harvesting, milling or preparing cereals that are allowed in diet (rice, maize and soya).

SAFETY OF OATS IN GFD

The issue of whether oats should be included in GFD has been discussed since the 1995, the year in which the largest and the most scientifically rigorous study on the safety of oats was published proposing the safety of oats consumption for adults with CD (11). Since then, there has been quite a great number of reports on oats being used safely as a GFD component in both adults and children with CD (12,13,14). For example, Janatuinen et al. study gave no evidence that a five-year oats consumption (50-70g daily) could result in either inducing any damage to small bowel villi or acquiring immunological response in adults (15). In their new article Peräaho and colleagues, pointed out that, although there was no evidence of any intestinal damage, oats containing GFD caused some more intestinal symptoms than the traditional diet (16). Högberg et al. have recently published the first randomized, double blind, multicentre study on the toxicity of oats in a large population of coeliac children (17). Their results indicated that oats in a GFD (at the average daily intake of l5g) did not prevent normalization of the small bowel mucosa and coeliac serology markers. Swedish researchers concluded that oats addition to GFD has improved its nutritional value, gave it a better taste and was well accepted by adult CD patients (18). Moreover, oats addition increased small amounts of fibre in the traditional GFD.

Different tolerability to these cereals is due to the existing structural differences among oats, wheat, barley and rye. It might be possible that the absence of certain amino acids sequences found in wheat gliadin, but not in oat avenin, makes oats torelable to coeliac patients. However, with respect to the safety of oats, some concerns still remain. Lundin et al. reported a case of 45 year old woman with biopsy-proven CD who responded poorly to GFD with oats and had clinical and histological relapses (19).

In practice, the vast majority of physicians and dietitians are reluctant to recommend oats in diet because most of commercially available oat flour is contaminated with wheat, ray or barley.

CD NON-RESPONSIVE TO GFD

Noninvasive CD diagnostic tests (detection of anti-tissue transglutaminase antibodies, antiendomysium antibodies and antigliadin antibodies) are currently available only in the largest medical centers in our country. Since, none of these tests possesses absolute sensitivity and specificity, performing small bowel biopsy remains a golden standard procedure in CD diagnosis. Biopsy should be reexamined by an expert in GI pathology in each of the cases when CD is non-responsive to GFD. The commonest reason for such a poor response to GFD in all age groups is a low compliance and an inadvertent gluten ingestion. Lactose intolerance, pancreatic insufficiency, bacterial small bowel contamination, colagenous colitis, food allergies, ulcerative jejunitis, refractory sprue and lymphoma should be considered in every single case with poor response to diet in adults (20). In children under the age of 2 the cause of a severe villous atrophy and bad response on GFD could be the following: lactose intolerance, allergy to cow milk and soya, giardiasis, bacterial small bowel contamination, autoimmune enteropathy, aquired hypogamaglobulinemia, microvillous atrophy and tufting enteropathy (21,22,23).

Refractory sprue is the entity known in adults and defined as a disease non-responsive to GFD in the initial therapeutic phase or after the clinical improvement and the period of remission achived on GFD. In up to 75% of patients with refractory sprue intraepithelial T-cells subset with an abnormal phenotype (CD3+, CD8-) and monoclonal TCRγ gene rearrangement can be detected by applying small bowel biopsies immunohistochemical and TCR gene rearrangement tests (24). These patients are considered to have one stage of developing enteropathy associated T-cell lymphoma. In the past, they were treated with various regimes including steroids, azathioprine, cyclosporine or elemental diet (25,26,27, 28). However, if patients did not respond to these treatments, a total parenteral nutrition was what was required. There still is the absence of a large and controlled study that compare drugs efficiency in refractory sprue. The treatment is largely empiric and is usually based on steroids and/or immunosupresants, but is nevertheless often ineffective. Goerres et al. suggested that small bowel T-cells immunophenotyping is mandatory in the work up of refractory sprue (29). They have pointed out that patients with type I refractory sprue, and the normal intraepithelial T-cells (CD3+, CD8+), had good clinical response to azathioprine combined with prednisone for 1 year. On the other hand, patients with type II refractory sprue, with aberrant intraepithelial population (CD3+, CD8-, TCRγ gene rearrangement), had bad response to the same therapy, and most of them died of enteropathy associated T-cell lymphoma. Authors proposed that other (chemo)therapeutic agents should be considered in patients with type II refractory sprue.

IS “NEW THERAPY” OF CD ON A HORIZON?

Although, the pathogenesis of CD is not fully discovered, we are now able to explain the interplay between gluten, tissue-transglutaminase, HLA DQ 2/8 and T-cells, as well as how this leads to a strong immunological response in the small intestine of CD patients. This knowledge has opened up some new possibilities for intervention strategies in affected individuals.

The idea to create genetically modified wheat devoid of toxic peptides was very promising. However, a lot of toxic peptides capable of inducing small bowel villi atrophy were identified not only in gliadin fractions of gluten, but also in glutenin. This fact was disappointing to the researchers because the great number of toxic peptides as well as a complex form of gluten genome make genetic engineering not achievable by any of the currently known techniques.

An interesting hypothesis comes from Shan et al. who describe a 33-mer gluten peptide resistant to decomposition by luminal digestive enzymes and peptidases of brush border membrane (30). This peptide efficiently stimulates mucosal CD4 T-cells rising values after deamination by tissue transglutaminase. A 33-mer peptide (containing six partially overlapping antigenic hot spots) was found in toxic but not in non-toxic cereals such as: oats, corn and rice. According to both in vitro and in vivo study results cleavage of 33-mer peptide by bacterial prolyl-endopeptidase caused the loss of antigenicity and deactivated its immunostimulatory properties. Shan et colleagues pointed out the possibility of bacterial endopeptidase addition to the gluten containing diet could be used to detoxify this and other immunostimulatory peptides of gluten.

This seemingly attractive hypothesis opened up quite a new scientific debate. Cerf-Bensussan and Heyman speculated that prolyl-endopeptidase addition was not required because 33-mer peptide was actually decomposed by lysosomal enzymes of epithelial cells during the transepithelial transport (paracellular diffusion is not possible due to the size of 33-mer peptide) (31). Koning and Vader proposed cautious approach regarding the “new therapy” because of the fact that enzymatic decomposition could be difficult due to the presence of gluten in food matrix together with many other components (32). Whatever the case may be, resistance to luminal hydrolysis of the 33-mer gliadin peptide and a possible new therapy intervention by external endopeptidase (in the form of capsules) should be taken into consideration as the subject in further researches.

Mauri et al. proposed IL-15 blockage, which is one of the main cytokine in CD pathogenesis, and is responsible for both the intraepithelial lymphocytes activation and their migration (a hallmark of CD, not observed in other inflammatory diseases) (33). It induces the interferon-γ secretion as well as the intraepithelial lymphocytes cytotoxic action. This therapy option could be achived by using IL-15 antibodies and could be considered as a possible solution, especially in refractory sprue when patients are non-responsive to drugs. The very possibility of some unpredictable systemic effects can represent one of this therapy practical problems.

Since one of the crucial role in CD pathogenesis belongs to the small bowel tissue-transglutaminase, it has been speculated that one kind of therapy could be this enzyme blockage (34). However this enzyme blockage is yet not clear. Furthermore, tissue transglutaminase can be found in other tissues and body fluids so that possible side effects must be taken into account.

One of the potential strategies in CD therapy could be the use of a vaccine. Experimental work by Sanger et al. has shown that intranasal administration of four doses of 50g wheat gliadin or recombinant α-gliadin in DQ8 transgenic mice could partially down-regulate systemic T-cell response to the

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SAŽETAK

Celijačna bolest (CB) je česta, doživotna bolest u genetski predisponiranih pacijenata, koja se odlikuje oštećenjem vilusa tankog creva, nastalim usled ingestije glutena. Veliki broj epidemioloških studija novijeg datuma ukazuje da je prevalenca celijačne bolesti među Evropskim populacijama u intervalu od 1:85 do 1:300. Klinički spektar celijačne bolesti je krajnje varijabilan i veći broj slučajeva danas ostaje nedijagnostikovan zbog atipične manifestacije. U poslednjoj dekadi sa pojavom visoko senzitivnih i specifičnih dijagnostičkih testova baziranih na serologiji, dolazi do daleko veće spoznaje o celijačnoj bolesti širom sveta. U isto vreme, svedoci smo velikog napretka u razumevanju patogeneze celijačne bolesti. U ovom prikazu razmotrićemo neke od vrlo aktuelnih tema iz domena terapije celijačne bolesti, uključujući i pokušaje na otkrivanju alternativa dijeti bez glutena kao što su: proizvodnja genetski modifikovane pšenice koja ne sadrži toksične peptide, uključivanje proteolitičkih enzima u dijetu pacijenata u cilju detoksifikacije glutena, primena vakcine i blokada glavnog patogenetskog citokina i enzima u celijačnoj bolesti.

UVOD

Najefikasnija terapija celijačne bolesti (CB) je striktna, doživotna dijeta bez glutena(DBG). Hrana koja nije dozvoljena u DBG uključuje sve proizvode koje sadrže pšenicu, raž i ječam. Štetni efekti izazvani su glijadinskom frakcijom pšeničnog glutena i sličnim prolaminima raži (sekalini) i ječma (hordeini). Pacijenti treba da budu upozoreni da neki lekovi, kao i neki vitamini i minerali mogu takođe da u sebi sadrže gluten kao neaktivni sastojak. Nelečena celijačna bolest može rezultirati malapsorpcijom, anemijom, deficitom vitamina, osteoporozom, malignitetom, niskim rastom kod dece itd. Pitanje koje se veoma često postavlja je: da li postoji bezbedni prag za konzumiranje glutena kod pacijenata sa celijačnom bolešću koji ne dovodi do oštečećnja mukoze tankog creva? U stvarnosti još nema odgovora zasnovanog na naučnim dokazima (1). Razlog za ovu činjenicu leži u izrazito varijabilnoj toleranciji među celijačnim bolesnicima. Zbog toga treba nastojati da pacijenti budu na što striktnijoj DBG (2). Iako se DBG smatra najefikasnijom terapijom, ona se teško prihvata i povećava mesečne troškove domaćinstva. Neki od proizvoda koji ne sadrže gluten su dosta neukusni, što može prouzrokovati izostanak saradnje pacijenata i nehotično konzumiranja glutena. U vezi sa ovim, kao nepobitna činjenica nameće se potreba za modifikovanjem DBG kako bi se učinila prihvatljivijom za pacijente (3). Istraživanja koja se u poslednje vreme sprovode pokazuju sve veće interesovanje za alternativnim formama terapije.

DA LI JE ETIKETA “BEZ GLUTENA” SVUDA TAČNA?

Proizvodi sa etiketom ’’bez glutena’’ (instant hrana za decu, različite vrste brašna, keksevi, ’’pasta’’) proizvedeni od strane domaćih proizvođača su veoma retki na Srpskom tržištu. Najveće količine proizvoda bez glutena se uvoze, uglavnom iz Nemačke, Finske i Mađarske. Takva vrsta hrane na našem tržištu, bez obzira da li s radi o domaćim ili stranim proizvodima, u potpunosti je bez glutena i bazirana je na prirodnim bezglutenskim proizvodima kao što su kukuruz, pirinač, soja, krompir i prokelj. U Velikoj Britaniji, Švedskoj i Finskoj bezglutenski proizvodi na bazi pšeničnog skroba ipak sadrže male količine glutena. Oni su u prošlosti uspešno korišćeni u terapiji CB i njihova prihvatljivost je bila dobra kod većine pacijenata (4,5,6). Međutim, bezbedna količina glutena u ovim proizvodima koji imaju etiketu “bez glutena” ostala je neodređena, zbog nepostojanja pouzdane metode za detekciju malih količina glutena. Zbog ove činjenice proizvodi od pšeničnog skroba se ne preporučuju za korišćenje od udruženja za celijačnu bolest u Južnoj Evropi, Sjedinjenim Američkim Državama i Kanadi (2,7). U praksu je nedavno uveden novi test za otkrivanje malih količina glutena u hrani. Valdes i sar. su uveli novi “sendvič ELISA test” (baziran na detekciji toksičnog prolaminskog epitopa QQPFP pomoću monoklonalnih antitela). Ovaj test u kombinaciji sa novom gluten ekstrakcijskom procedurom može da detektuje najmanje nivoe glutena (u količini do 3.2 ppm = mg / kg) u pšenici, raži i ječmu (8). Ovaj visoko specifičan i senzitivan test je korišćen od strane finskih istraživača koji su ispitivali odrasle bolesnike, preporučujući bezbedan prag za glutensku kontaminaciju od 100ppm. Pod uslovom da je dnevni unos glutena 300g, 100ppm odgovara količini od 30 mg glutena dnevno. Razlike u histološkom nalazu, serologiji i kvalitetu života među grupama pacijenata lečenih sa prirodno bezglutenskim sa jedne i proizvodima od pšeničnog skroba sa druge strane, u periodu od 1 do 10 godina nisu nađene. Komisija Codex Alimentarius-a Svetske Zdrastvene Organizacije je ranije predložila da bezglutenski proizvodi ne bi trebalo da sadrže više od 200 ppm glutena (10).

Ukrštena kontaminacija prirodnih bezglutenskih proizvoda sa toksičnim cerealijama može biti jedan od problema u praktičnoj primeni dijete (7). To se može desiti za vreme žetve, mlevenja ili pripremanja cerealija koje su dozvoljene za korišćenje u dijeti (pirinač, kukuruz i soja).

BEZBEDNOST OVSA U DBG

O spornom pitanju da li ovas treba uključiti u DBG raspravlja se još od 1995 godine, kada su bile publikovane najveće i najstrože naučne studije koje su savetovale bezbednu upotrebu ovsa kod odraslih sa CB (11). Od tada postoji veliki broj izveštaja o ovsu kao bezbednoj komponenti DBG, kako kod odraslih, tako i kod dece sa CB (12,13,14). Na primer Janatuinen i sar. u svojoj studiji ne daju dokaze da petogodišnje konzumiranje ovsa (50-70 g dnevno) dovodi do oštećenja vilusa tankog creva i pojave imunološkog odgovora kod odraslih (15). U svom novom članku Peräaho i sar. ističu da iako nije bilo dokaza o bilo kakvom oštećeju sluzokože tankog creva, DBG koja sadrži ovas izaziva nešto više intestinalnih simptoma od tradicionalne dijete (16). Högberg i sar. su nedavno publikovali prvu randomiziranu, dvostruko slepu, multicentričnu studiju u kojoj su ispitivali toksičnosti ovsa kod velike populacije dece sa CB (17). Njihovi rezultati pokazuju da ovas u DBG (kod prosečnog dnevnog unosa od 15g) nije nepovoljno uticao na normalizaciju kako mukoze tankog creva, tako i seroloških markera kod ispitivanih pacijenata. Švedski istraživači su zaključili da dodatak ovsa bezglutenskoj dijeti poboljšava njenu hranljivu vrednost, ukus i dobro se toleriše od strane odraslih pacijenata sa CB (18). Šta više, dodatak ovsa povećava malu količinu vlakana u tradicionalnoj bezglutenskoj dijeti.

Razičita podnošljivost ovsa, pšenice, ječma i raži zavisi od postojećih strukturalnih razlika među ovim cerealijama. Moguće je da odsustvo određenih aminokiselinskih sekvenci koje se ne nalaze u aveninu ovsa za razliku od pšeničnog glijadina, čini ovas tolerantnim za pacijenate sa CB. Međutim, u pogledu bezbedne upotrebe ovsa, određena zabrinutost i dalje ostaje. Lundin i sar. su prikazali slučaj 45-godišnje žene kod koje je biopsijom dokazana CB, koja je imala klinički i histološki relaps na DBG sa ovsom (19).

U praksi, velika većina lekara i nutricionista nevoljno preporučuje ovas u DBG jer su proizvodi od ovsa na tržištu uglavnom kontaminirani sa pšenicom, raži ili ječmom.

CB BEZ ODGOVORA NA DBG

Neinvazivni dijagnostički testovi za CB (detekcija antitela na tkivnu transglutaminazu, antiendomizijumskih antitela i antiglijadinskih antitela) su danas dostupni samo u najvećim medicinskim centrima u našoj zemlji. Pošto nijedan od ovih testova ne poseduje apsolutnu senzitivnost i specifičnost, uzimanje biopsije tankog creva i dalje ostaje zlatni standard u dijagnostici CB. Biopsija treba da bude ponovo pregledana od strane eksperta za gastrointestinalnu patologiju u svakom pojedinačnom slučaju kada je CB bez odgovora na DBG. Najčešći razlog za slab odgovor na bezglutensku dijetu u svim starosnim grupama je loša saradnja pacijenta i nehotična konzumacija glutena. Nepodnošljivost laktoze, insuficijenciju pankreasa, bakterijsku kontaminaciju tankog creva, kolagenozni kolitis, alergiju izazvanu hranom, ulcerozni jejunitis, refraktorni sprue i limfom treba uzeti u razmatranje u svakom pojedinačnom slučaju sa lošim odgovorom na dijetu kod odraslih (20). Kod dece uzrasta do 2 godine loš odgovor na DBG uz pojavu teške vilusne atrofije može se naći u slučaju: nepodnošljivosti laktoze, alergije na kravlje mleko i soju, bakterijske kontaminacije tankog creva, autoimune enteropatije, stečene hipogamaglobulinemije, mikrovilusne atrofije i ’’tufting’’ enteropatije (21,22,23)

Refraktorni spru je entitet poznat kod odraslih osoba. Definisan je kao bolest kod koje nema odgovora na DBG u inicijalnoj terapijskoj fazi ili posle kliničkog poboljšanja i perioda remisije na DBG. U skoro 75% pacijenata sa refrektornim spru klon intraepitelijalnih T-ćelijskih limfocita sa abnormalnim fenotipom (CD3+,CD8־) i monoklonskim TCRγ genetskim preuređenjem može biti otkriven pomoću imunohistohemijskih i genetskih testova na biopsijama tankog creva (24). Smatra se da ovi pacijenti imaju jedan stadijum razvoja T-ćelijskog limfoma udruženog sa enteropatijom . Do sada su ovi pacijenti bili lečeni pomoću različitih lekova, uključujući steroide, azatiopirin, ciklosporin ili elementalnu dijetu (25,26,27,28). Ako pacijenti ne odgovore na terapiju, totalna paranteralna ishrana je terapijska metoda izbora. Za sada ne postoji velika i kontrolisana studija koja upoređuje delotvornost lekova u lečenju refraktornog spru. Lečenje je u većini slučajeva empirijsko i obično se bazira na steroidima i/ili imunosupresivima (ali je vrlo često neefikasno). Goerres i sar. su predložili da imunofenotipizacija T-ćelija tankog creva bude obavezna metoda ispitivanja bolesnika sa refraktornim spru (29). Oni ističu da su pacijenti sa tip I refraktornim spru, sa normalnim intraepitelijalnim T-ćelijama (CD3+, CD8+), imali dobar odgovor na jednogodišnju terapiju azatioprinom i prednizonom. Sa druge strane, pacijenti sa tip II refraktornim spru, sa aberantnom populacijom intraepitelijalnih limfocita (CD3+, CD8-, TCRγ) su imali loš odgovor na istu terapiju, i kod većine njih je došlo do letalnog ishoda usled T-ćelijskog limfoma udruženog sa enteropatijom. Autori predlažu da se i drugi (hemo)terapeutski agensi trebaju uzeti u obzir kao terapijski izbor kod pacijenata sa refraktornim spru tip II.

DA LI JE NA HORIZONTU “ NOVA TERAPIJA” CB ?

Iako patogeneza CB nije potpuno poznata, danas se može objasniti uzajamno delovanje glutena, tkivne transglutaminaze HLA DQ 2/8 i T-ćelija, kao i način na koji ova interreakcija dovodi do jakog imunološkog odgovora u sluzokoži tankog creva. Ova saznanja su otvorila nove mogućnosti u terapiji obolelih.

Ideja o stvaranju genetski modifikovane pšenice bez toksičnih peptida je u prošlosti puno obećavala. Međutim, mnogo toksičnih peptida sposobnih da izazovu vilusnu atrofiju u tankom crevu je identifikovano ne samo u glijadinskoj frakciji glutena, već i u gluteninu. Ova činjenica je razočaravajuća za istraživače jer zbog velikog broja toksičnih peptida, kao i zbog složenosti glutenskog genoma, genetski inženjering je praktično neizvodljiv sa bilo kojom danas primenjivanom tehnikom.

Interesantna hipoteza dolazi od strane Shana i sar., koji opisuju 33-mer glutenski peptid rezistentan na razgradnju od strane luminalnih crevnih enzima i peptidaza četkaste membrane enterocita (30). Ovaj peptid efikasno povećava nivo CD4 T-ćelija nakon njegove deaminacije tkivnom transglutaminazom. 33-mer peptid (koji sadrži šest delimično preklopljenih antigenskih tačaka) je bio pronađen u toksičnim, ali ne i u cerelijama kao što su: ovas, kukuruz i pirinač. Prema rezultatima “in vitro” i “in vivo” studija razgradnja bakterijskom prolil-endopeptidazom izaziva gubitak antigenskih i deaktivaciju imunostimulativnih svojstava 33-mer peptida. Shan i sar. ističu da se bakterijska endopeptidaza može dodati dijeti koja sadrži gluten i na taj način izvršiti detoksikacija ovog i drugih imunostimulativnih peptida glutena.

Ova na prvi pogled privlačna hipoteza otvorila je sasvim nove naučne rasprave. Cerf-Bensussan i Heyman smatraju dodatak prolil-endopeptidaze nepotrebnim, jer se 33-mer peptid razgrađuje lizozomalnim enzimima epitelijalnih ćelija u toku transepitelijalnog transporta (paracelularna difuzija nije moguća zbog veličine 33-mer peptida) (31). Koning i Vader predlažu oprezan pristup u primeni “nove terapije” zbog činjenice da enzimska razgradnja može biti onemogućena prisustvom mnogih drugih komponenati u hrani osim glutena (32). U svakom slučaju rezistentnost 33-mer glijandinskog peptida u procesu intraluminalne hidrolize i mogućnost nove terapijske primene dodavanjem endopeptidaze (u obliku kapsula) će biti predmet budućih istraživanja.

Mauri i saradnici su predložili blokadu IL-15, jednog od glavnih citokina u patogenezi CB, koji je odgovoran za aktivaciju i intraepitelijalnu migraciju CD8 limfocita (histološhi znak CB, koji nije nađen u drugim bolestima tankog creva) (33). Dejstvo IL-15 proizvodi sekreciju interferona-γ kao i citotoksično dejstvo intraepitelijalnih limfocita. Ova terapijska opcija se može postići korišćenjem IL-15 antitela, što može biti korisno posebno u refraktornom spru gde pacijenti i pored terapije ne postižu remisiju. Jedan od praktičnih problema u ovoj terapiji bi mogla biti velika mogućnost pojave nepredvidljivih sistemskih efekata.

Pošto jedna od najvažnijih uloga u patogenezi CB pripada tkivnoj transglutaminazi tankog creva, smatra se da bi se blokada ovog enzima mogla iskoristiti u terapijske svrhe (34). Međutim, mehanizam ovakve enzimske blokade još nije sasvim poznat. Osim toga, tkivna transglutaminaza se može naći u drugim tkivima i tkivnim tečnostima, tako da je neophodno uzeti u obzir moguće neželjene efekte.

Jedna od potencijalnih strategija u terapiji CB može biti upotreba vakcine. Eksperimentalni rad Sangera i sar. je pokazao da bi intranazalna primena četiri doze 50g pšeničnog gliadina ili rekombinantnog α-gliadina kod DQ8 transgenetskih miševa mogla delimično suzbitii sistemski T-ćelijski odgovor koji nastaje posle paranteralnog unosa glijadina (35). Potencijalni rizik primene vakcine se sastoji u izazivanju imunizacije umesto tolerancije.

ZAKLJUČCI

I pored postojanja nekih veoma obećavajućih hipoteza, još je rano zaključiti da je “nova terapija CB” na pomolu. Stalna istraživanja koja se vrše na ovom polju, potpuno razumevanje dosta komplikovane patogeneze CB, zajedno sa pokušajima da se razvije precizan animalni model ove bolesti, će učiniti zamenu DBG nekom drugom vrstom terapije mnogo izvesnijom. Iako je opterećujuća za bolesnike, bezglutenska dijeta i dalje ostaje efikasna, bezbedna i relativno jeftina terapija. Danas raspoloživi podaci ukazuju da je umerena količina čistog ovsa bezbedna za većinu pacijenata sa CB. Osim toga, ovas poboljšava kvalitet i prihvatljivost DBG. Na kraju, neke nove tehnike za merenje nivoa glutena u hrani će doprineti prikladnom obeležavanju hrane na tržištu i eliminisanju slučajne ingestije glutena od strane pacijenata