Scientific Data and Guidance

Scientific Data and Guidance for inflammatory bowel diseases as an example for autoimmune diseases

The inflammatory bowel diseases (IBD) are comprised of two major phenotypes, Crohn’s disease (CD) and ulcerative colitis (UC). It is likely that chronic inflammation in IBD is due to aggressive cellular immune responses to intestinal antigens which are not yet well characterized in genetically predisposed individuals. Standard therapy for the symptomatic treatment of IBD includes sulfasalazine, mesalazine, systemic and topical glucocorticoids, immunosuppressants like azathioprine or 6-mercaptopurine, and in severe cases also treatment with anti-TNF-α therapy, methotrexate, or cyclosporine as monotherapy or in combination with other agents.

Profound alterations in mucosal immunity have been demonstrated in patients with IBD. The cross-inhibitory Th1/Th2 balance is an important regulatory mechanism of the gastrointestinal immune system. The Th1/Th2 balance is regulated by the local cytokine environment within the intestinal mucosa. There is a reciprocal down-regulation of Th1 proliferation by Th2 cytokines and vice versa. Particularly in CD, there is strong evidence of a CD4 T helper cell type 1 (Th1) immune response that contributes to the pathogenesis of disease. Originally, the rationale for performing research with helminths was based on the hygiene hypothesis, which was refined from the “Old friends Hypothesis” for diseases resulting from disorders of the immune system, which postulates that multiple childhood exposures to parasites and pathogens protect an individual from allergic and autoimmune disease later in life, whereas individuals raised in a more sanitary environment are more likely to develop autoimmune diseases and allergies. In line with these hypotheses, epidemiologic evidence, case control observations, animal studies and clinical studies all suggest that exposure to helminth parasites which followed the whole human evolution since its early beginnings may afford protection from or even treat autoimmune disorders and also IBD.

Helminth infections shift the host’s immune bias from Th1 response to augmented Th2 responses. Typically, this helminth-induced response involves the production of the cytokines interleukin-4 (IL-4), IL-5, IL-9, IL-10, and IL-13, as well as immunoglobulin E (IgE) and the expansion and mobilization of specific effector cells, such as mast cells, eosinophils, and basophils. A stimulation of a Th2 response by a helminthic infection may suppress a predominant Th1 situation by the inherent cross-inhibitory mechanisms. However, it seems unlikely that helminths simply alter the Th1/Th2 balance. Recent studies indicate that helminths stimulate the development of regulatory T-helper cells (Treg) that reduce both Th1 and Th2 responsiveness.
Treg lymphocytes actively suppress the differentiation of both, Th1 and Th2 lymphocytes by the secretion of IL-10 and transforming growth factor-β (TGF-β).

Early experiences suggest that embryonated eggs of the porcine whipworm Trichuris suis (Trichuris suis ova, TSO®) colonize the human intestine without invading or infecting.

Safety and efficacy of TSO® have been investigated in clinical studies with patients suffering from IBD, Multiple Sclerosis, allergies and other autoimmune diseases. The results of the previous trials indicate that Trichuris suis therapy might be effective in both forms of IBD, CD and UC. Results of treatment with a single dose were temporary in some patients, but it was possible to maintain a remission with a scheduled administration of TSO® every 2-3 weeks for longer periods.
The clinical trials in IBD demonstrated improvement of disease activity, with remission observed in many patients, i.e., TSO® has been shown to be effective not only in treating active disease, but also in maintaining remission. Treatment with TSO® appeared to be safe in all clinical trials.

Immune Dysregulation in IBD

Mucosal homeostasis is a balancing act between effector T cells (T helper cells type l and type 2, Th1/Th2) and regulatory T cells. An increase in the effector cell population with excessive inflammatory responses or a decreased function of regulatory T cells may result in mucosal inflammation.

Profound alterations in mucosal immunity have been demonstrated in patients with IBD. Particularly in CD, there is strong evidence of a CD4 T helper cell type 1 (Th1) immune response that contributes to the pathogenesis of disease. The Th1 response typically occurring in viral and bacterial infections is characterized by an increase in interleukin (IL)-12 and interferon-γ. In contrast, Th2 response is characterized by increased IL-4, IL-5, and IL-13. Polarized Th1 responses impede expression of Th2 cytokines and polarized Th2 responses impede Th1 activity.

The cross-inhibitory Th1/Th2 balance is an important regulatory mechanism of the
gastrointestinal immune system. The Th1/Th2 balance is regulated by the local cytokine environment within the intestinal mucosa. There is a reciprocal down-regulation of Th1 proliferation by Th2 cytokines and vice versa. The cytokine profile in active UC shows significant interferon-γ release but is not as polarized as that seen in CD. It is currently accepted that UC is an untypical Th2-dominated disease. The proinflammatory cytokines IL-6, IL-8, IL-10 and tumor necrosis factor are increased in both active UC and CD.

Hygiene Hypothesis and IBD

The history of helminths living in the intestinal tract or other locations of their host can be traced back to the earliest record of human beings, and colonization of humans with these organisms was nearly universal until the early 20th century. Although effective preventive and therapeutic measures have been developed for most parasitic worms, helminth infections are still very common in the developing world today. It has been estimated that more than one billion individuals worldwide are infected with one or more helminths, with the highest frequency found in children subjected to poor sanitation. The hygiene hypothesis postulates that multiple childhood exposures to enteric pathogens protect an individual from autoimmune diseases (e.g. IBD) later in life, whereas individuals raised in a more sanitary environment are more likely to develop immunological disease like IBD. Modern
hygienic practices and absence of exposure to intestinal helminths appears to be an important factor contributing to immune dysregulation and increased susceptibility to immunological diseases. This theory was originally expressed as the “Old friends”-hypothesis.

Epidemiological studies show that like other autoimmune diseases, IBD is most common in Western industrialized countries that are characterized by affluent societies living in sanitized environments. IBD is rare in developing countries with less clean environments and more crowded living conditions. These epidemiologic findings suggest that the prevalence of IBD is inversely correlated to the prevalence of helminthic parasites in that population.

Helminth parasites are the classic inducer of Th2 responses. The Th2-polarized T cell response driven by helminth infection has been linked to attenuation of damaging Th1 driven inflammatory responses. This may prevent some Th1-mediated autoimmune diseases with overly active Th1 inflammatory response such as occurs in CD. In addition to stimulating vigorous Th2 response, helminth infections are also capable of inducing suppressive T-cell populations known as regulatory T cells (Treg), which may help control morbidity and dampen resistance to reinfection through their potent immune regulatory mechanisms. Genetically predisposed persons who never were exposed to helminths might lack a strong counteractive Th2 immune response and Treg cell clones, rendering the intestinal immune system more prone to Th1-mediated diseases like CD.

Physical and Chemical Properties

TSO® is a natural probiotic product. It is presented as a non-sterile aqueous suspension of the viable embryonated eggs of the whipworm Trichuris suis for oral use. The eggs are suspended in an isotonic phosphate buffered saline solution of pH2.4. TSO® bottles contain either 500, 1000 or 2500 viable Trichuris suis ova (TSO®) in 15 ml of the suspension supplied in a 30 ml glass container with polypropylene screw cap.

Nonclinical Studies

Initial nonclinical studies with TSO® were aimed to identify appropriate and relevant animal models mimicking the transient colonization of T. suis observed in humans. The monkey and the rabbit were identified as relevant animal models and were used in the main program of pharmacological and toxicological studies. Due to the lack of disease models in these species all studies with TSO® were conducted in healthy animals. However, studies with other helminths mainly conducted in rodent models provide insight in several immune-modulatory mechanisms that are probably responsible for the therapeutic effect.

Immunological host response to Trichuris suis

The host response to Trichuris suis was studied in the pig which is the natural host of T. suis as well as in the monkey and the rabbit, which are foreign hosts but allow a transient colonization with T. suis. Because of the transit nature the monkeys and rabbits are considered as appropriate models for the treatment of humans with TSO®.

As expected for a parasitic colonization, a marked increase in blood eosinophilic granulocytes was noted in all three species. Levels of eosinophilic granulocytes peaked 6-8 weeks after first administration in pigs and within 3-4 weeks after first administration in monkeys and rabbits probably reflecting the earlier expulsion from the foreign hosts (monkey and rabbit). White blood cell counts and levels of lymphocytes, neutrophils and monocytes remained unaffected. Only in rabbits a transient decrease of basophilic granulocytes was noted in parallel to the increased eosinophilic granulocytes. In monkeys treated every two weeks with 500 or 2500
TSO®/kg the increase of blood eosinophilic granulocytes was dose-dependent.

In pigs and rabbits, a marked infiltration of eosinophilic granulocytes was also observed in the lamina propria and the submucosa of the caecum and anterior part of the colon, which are the target sites of T. suis. The adjacent regions of ileum and distal colon were affected to a lesser extent. In addition, an increased infiltration of mast cells was noted in the proximal colon of pigs colonized with T. suis. Only slight effects were noted in monkeys, probably due to the relatively high spontaneous infiltration rates of eosinophilic granulocytes and mast cells in the intestinal mucosa of the animals. Formation of antibodies directed against the excretory/secretory (E/S) antigen of T. suis was observed in all species. In pigs, levels of E/S-Antigen specific IgG1, IgG2 and IgM peaked approximately 9 weeks after administration of a single dose and declined after worm expulsion, while IgA rose earlier and remained elevated after expulsion. In monkeys E/S antigen specific IgG peaked 6 weeks after beginning treatment with either 500 or 2500 TSO®/kg administered every two weeks. In rabbits, peak levels of E/S antigen specific IgG were reached within 4 weeks after treatment with 2500 TSO®/kg every two weeks. Mean antibody titers appeared to be correlated to the TSO® dose.

In all three species the treatment with TSO® led to induction of a Th2 immune response. In pigs the stimulation of peripheral blood mononuclear cells (PBMC) with T. suis E/S antigen led to a pronounced increase in IL-4 secreting cells from week 4 to week 8 after administration. Secretion of IL-10, IFN-γ and TNF-α from E/S antigen activated PBMC was not affected. In rabbits, an increased expression of IL-4 and IL-13 in PBMC was demonstrated approximately 4 weeks after start of TSO® treatment, while expression of IL-10, interferon gamma (IFN-γ) and TGF-f3 remained unaffected. Monkeys demonstrated a pronounced Th2 response already 1-2 weeks after the first administration of TSO®. In PBMC, activated in vitro with T. suis E/S antigen, a marked increase of secretion of IL-4, IL-5 and IL-13 was noted. Secretion of IL-2 and IFN-γ from activated PBMC was elevated to a less extent. No difference to the control group was observed for secretion of IL-10, IL-12, IL-17, IFN-γ, TGF-P, and TNF-α from activated PBMC. The increase in cytokine secretion from E/S antigen activated PBMC appeared to be dose dependent. The secretion of Th2 cytokines from activated PBMC remained elevated through the dosing period.
An increased expression of Th2 cytokines was also observed in the intestinal mucosa at the site of colonization. In pigs, elevated levels of IL-4, IL-5 and IL-13, but not IL-10 mRNA were observed in the mucosa of the proximal colon 2-11 weeks after administration of a single TSO® dose. In vitro treatment of intestinal pig epithelial cells (IPEC-1) led to production of IL-6 and IL-10 within 24 hours. In rabbits increased IL-13 mRNA levels were detected in the mucosa of the proximal colon at week 7 after repeated treatment with TSO®. Levels of IL-4, IL-10, IFN-y and TGF-13 mRNA were not changed.
Treatment with TSO® did not change the pattern of lymphocyte types in peripheral blood of pigs, rabbits or monkeys at various stages of the TSO® treatment.

These studies in pigs have demonstrated that the immunological host response is due to treatment with viable embryonated TSO®. None of the above described effects was seen after treatment with inactivated TSO®.

Pharmacokinetics and Drug Metabolism in Animals

There is no pharmacokinetic information regarding TSO®, as neither the ova nor the developing larvae and mature worms are systemically absorbed, and thus measurement of concentrations in blood is not relevant. In lieu of pharmacokinetic data, the life cycle of the whipworm is provided as follows:

Following ingestion of infective T. suis ova by pigs (natural host), all subsequent larval development occurred in the mucosa of the caecum and colon. Eggs hatched in the distal region of the small intestine and throughout the large intestine. Twenty-four hours after ingestion the majority of the infective eggs were found in the large intestine, larvae were seen in the intestinal contents. Three days after infection 85% of eggs remaining in the colon had hatched but no larvae were found in the intestinal contents after the 5th day. Larvae penetrated the colonic mucosa via the crypts of Lieberkühn, where they entered the cells lining the crypts. The growing larvae entered the lamina propria and became equally distributed between crypt cells and cells of the lamina propria.

Approximately 10 days after hatching the larvae migrated to the mucosal surface. Damage to the lamina propria appeared to be very localized and slight as the larvae only appeared to disrupt the crypt and lamina propria cells in which they were lying. No evidence of any visceral migration could be found. From the 28th day, the larvae were found lying in a shallow depression on the mucosal surface covered by a raised sheath of mucosal epithelial cells. Fully formed eggs were first observed in the uterus of female worms on day 41; this was the earliest date that eggs were detected in the feces of the host. Little or no host tissue reaction was seen in any of these infections. Expulsion of the mature worms from the host occurred between week 9 and 11 after ingestion. In monkeys and rabbits, which are considered as appropriate models for TSO® treatment in humans, the majority of the ingested TSO® hatched after ingestion. Hatching occurred mainly in the cecum and the anterior part of the colon. Twelve hours after ingestion the larvae were associated with the mucosa of the caecum and the anterior part of the colon. Also at later stages, similar to the pig, the colonization of the gut mucosa was confined to the caecum and colon; a colonization of the upper part of the gastrointestinal tract was not observed. Detailed macroscopy and histopathology of other organs gave no evidence for an aberrant migration of T. suis into visceral tissues in monkeys and rabbits. After administration of a large single TSO® dose, larvae remained established in the mucosa of the large intestines for at least 2 weeks in the rabbit. In the monkey the time-point of expulsion was variable: several animals expelled T. suis larvae within 10-15 days, while remained established in other animals over 20 days. Larvae were not detected in the intestines at later time-points after ingestion of a single dose indicating only transient colonization and expulsion of before reaching the adult larval stages. The early expulsion from the foreign host is also reflected by an earlier onset of the immunological host response seen in monkeys and rabbits compared to pigs.
Mature worms or an excretion of eggs in the feces of the hosts, which would have indicated sexual maturity of the larvae, were neither observed in monkeys nor in rabbits. After multiple dosing (7 doses) in monkeys every other week simulating the schedule in clinical trials, larvae were not detectable in the intestinal mucosa one week after the last dosing, which indicates that larvae are digested and expelled earlier after induction of the host immune response.

Single and Repeated Dose Studies

The pig was generally not considered as a suitable animal model for toxicity studies with TSO® as pigs are the natural hosts of T. suis allowing a highly efficient permanent colonization and a full maturation to adult worms. Non-natural hosts as monkeys and rabbits which are susceptible to a transient colonization with T. suis similar to the transient colonization in humans have been identified as relevant models for toxicity studies. Based on the pharmacodynamic and pharmacokinetic characteristics and the close similarity with the human regarding anatomy, physiology and immune function, the monkey is considered as primary toxicity model for TSO®. The rabbit was selected as an additional model for reproduction toxicity studies.

Several exploratory studies employing various TSO® doses and treatment schedules were conducted in monkeys and rabbits (up to 25,000 TSO®/kg in monkeys and up to 33,000 TSO®/kg in rabbits). In all studies TSO® was well tolerated and did not provoke signs of systemic toxicity. The clearest sign of the host reaction to T. suis was a marked increase of eosinophilic granulocytes in the peripheral blood (peaking around day 20 in the monkey and day 30 in the rabbit) as well as a marked infiltration of eosinophilic granulocytes into the mucosa and submucosa of the caecum and colon which are the target regions of T. suis. In some of the treated animals, small focal alterations were observed in the otherwise unaffected mucosa of the caecum and colon. The occurrence of the focal alterations did not show a clear dependence on the dose or dosing frequency. The focal alterations presented as small red discolored foci (size usually 1-2 mm) and were in some cases partly thickened and indurated.
The foci were considered to be probably related to T. suis; however, at least in monkeys similar alterations occurred also spontaneously in control animals. As no clear histopathological changes were observed, in particular no epithelial damage, the focal alterations were considered to be of no pathological relevance. A general inflammation of larger parts of the intestinal mucosa was not observed even when the animals were treated with high TSO® doses of 25,000 TSO®/kg (monkeys) or 33,000 TSO®/kg (rabbits). In rabbits, increased mesenterial lymph nodes and after treatment with a high dose also thickened Peyers patches were observed.

A 13-week subchronic toxicity study with TSO® was conducted in cynomolgus monkeys. Six animals per sex/group were orally treated every two weeks with placebo, 500 TSO®/kg or 2500 TSO®/kg. According to the mean body weight, the female animals received in total 7 doses of 1500 TSO® or 7500 TSO®, while the male animals received 7 doses of 2250 TSO® or 11500 TSO®, respectively. Scaled on a dose per body weight base the highest dose in the subchronic toxicity study was more than 20-fold above the highest dose proposed in future clinical studies (7500 TSO® or 107 TSO®/kg). Four animals per sex/group were sacrificed after 13 weeks, while the remaining animals were sacrificed after a 12-week recovery period.

During treatment the typical host response to TSO® was noted in a dose-dependent manner. However, no signs of treatment related toxicity was noted. In particular, treatment with TSO® did not influence clinical signs, mortality, body weight, food consumption, body temperature, hematological parameters (except eosinophilia), blood coagulation, urinary parameters, clinical biochemistry parameters, ophthalmological and auditory parameters and organ weights. TSO® did not affect the level of total IgE. No diarrhea or increased frequency of occult blood in stool was noted in the treatment groups. Only in the male animals of the high dose group on day 40 of treatment showed a tendency to softened feces was noted, however the fecal consistency was considered to be in the normal range. At macroscopy, 8 days after the last treatment, no larvae were detected in the intestinal mucosa indicating early expulsion of the larvae after repeated dosing. In a subgroup with 4 animals treated with a single TSO® dose, a high hatching rate and colonization of the caecal mucosa with T. suis was demonstrated. In animals of all groups small focal alterations, as described above, were observed in the otherwise unaffected mucosa of the caecum and colon.

However, the frequency was higher only for the females of the low-dose group when compared to the control group. A detailed macroscopical and microscopical inspection of other organs did not reveal any evidence for an aberrant migration of T. suis into other tissues. Two of the female animals of the high dose group showed increased mesenteric lymph node weights, which subsided in the recovery period. At the histopathological level a slight trend towards increased infiltration of eosinophilic granulocytes and mast cells into the mucosa of caecum and colon was noted for the male monkeys. An increased infiltration of eosinophilic granulocytes was also noted in mesenteric lymph nodes of single TSO® treated animals. No further histopathological changes were noted. The observed changes in the treated monkeys were considered to be the expected (pharmacodynamic) host response. None of the findings was considered to be of pathological/toxicological relevance. After repeated treatment of monkeys with TSO® every other week over 13 weeks a NOAEL (no-observed adverse effect level) of > 2500 TSO®/kg can be concluded (> 7500 TSO®/female, > 11250 TSO®/male animal).

Special Studies

Since the broad-spectrum anthelminthic mebendazole is the recommended drug for treatment of human Trichiasis its effectiveness against T. suis was studied as an antidote. The study was conducted in Goettingen mini-pigs as these animals allow a permanent colonization with high numbers of T. suis larvae/worms. Monkeys and rabbits were not considered appropriate for this study as these non-natural hosts allow only a transient colonization with T. suis with early and spontaneous digestion and expulsion. Two groups of minipigs (4 male and 4 females/group) were treated with a single dose of 2500 TSO® (300-380 TSO®/kg).

Fifty days after administration of TSO® one group was treated with 2×100 mg mebendazole/day over 4 days, which is the recommended treatment for human trichuriasis (according to the prescribing directions for Vermox®) while the other group served as control. Treatment with mebendazole led to a complete elimination of T. suis in all animals of the group as was demonstrated by a 100% reduction of fecal egg excretion and complete absence of intestinal T. suis larvae/worms at dissection.

Summary of Toxicity Studies

Monkeys and rabbits were identified as relevant animal models for TSO®. Both species demonstrated a transient colonization with T. suis, which was confined to the mucosa of the caecum and colon. No aberrant migration into other tissues and no signs of systemic toxicity were observed. The typical host reaction was characterized by an increase of eosinophilic granulocytes in peripheral blood and infiltration of eosinophilic granulocytes in the mucosa of caecum and colon, the formation of T. suis antigen specific IgG, and an increase in expression of Th2 cytokines in activated peripheral blood mononuclear cells and intestinal tissue. In some treated animals minor focal alterations in the otherwise unaffected mucosa of the caecum and colon were observed. As no clear histopathological changes were observed, in particular no epithelial damage, the focal alterations were considered to be of no pathological relevance. However, as the mucosa was otherwise unaffected and as no general inflammation of larger parts of the mucosa were observed, the small focal alterations were not considered as local intolerance reactions.

Neither diarrhea nor an increased frequency of occult blood in stool was observed. No systemic or local adverse effects were noted up to a dose of 2500 TSO®/kg when administered every two weeks over 13 weeks. Treatment with TSO® had no effect on fertility and embryo-fetal development and did not express teratogenic properties at a dose of 2500 TSO®/mg, given every two weeks. In conclusion, the nonclinical studies with TSO® in monkeys and rabbits did not cause a safety concern for the planned clinical trial. It was demonstrated in pigs that mebendazole when used in the dose regime recommended for human Trichiasis is also effective against T. suis. Therefore, if elimination of T. suis from patients is necessary, mebendazole appears to be the antidote of choice.

Pharmacokinetics and Drug Metabolism in Humans

Fate of TSO®/ T. suis in humans

The microenvironment of the intestine induces the hatching of larvae from embryonated eggs and the release of the first-stage juvenile larvae of Trichuris suis. The eggs have two polar plugs, which are detached/opened upon hatching. Preparations of TSO® for clinical application consist of more than 80% embryonated eggs. Non-embryonated eggs will by nature not be triggered to hatch. The manufacturing process controls embryonation which occurs after >5-6 weeks. Under natural conditions, the eggs embryonate in soil after >5-6 weeks, provided conditions are favorable. Only after embryonation the eggs are able to hatch in humans. To the best of our knowledge T. suis eggs are not absorbed systemically and Trichuris suis has not been shown to be invasive.

By nature, neither the eggs nor the larvae are converted chemically at the intestinal wall or other digestive processes. Dead larvae are digested like food proteins. Therefore, the traditional model of pharmacokinetics (absorption, plasma protein binding, distribution, elimination, and bioavailability) is not applicable. Egg excretion has not been detected in regular stool samples from IBD patients but has been reported by Beer. No living worms or larvae have been found in stool samples or during endoscopy in studies done by Summers, et. al., in IBD patients. There is a single case report about detection of an adult Trichuris by biopsy in a 16-year old patient who underwent TSO® treatment for CD. Segments of immature larvae were identified directly beneath attenuated ileocecal mucosal epithelium. The site of colonization and the ultrastructural localization within the epithelial surface are similar to the migration of T. suis in pigs. Since the worm was identified free-floating in the lumen, without evidence of mucosal attachment, it may have been in the midst of being expelled from the bowel.

Up to now to the best of our knowledge no cases of symptomatic or pathologic invasion or infestation of T. suis were described neither in humans nor in other non-natural hosts like rabbits or monkeys. Based on the experience with T. suis in humans, the possibility of errant larvae of T. suis establishing in vital organs or sites in humans seems unlikely.

Overdose

Clinical signs and symptoms of overdose have never been reported. A description of overdose is unknown. Since the broad-spectrum anthelminthic mebendazole is the recommended drug for treatment of human Trichuriasis and since mebendazole has been demonstrated to effectively eliminate T. suis from pigs when administrated at the dose regime recommended for human patients, mebendazole is considered to be the antidote of choice.

Effect on QT Interval

TSO® is not systemically absorbed and therefore is not expected to have systemic bioavailability. The distribution of TSO® is relegated to the gut, and specifically the intestinal tract. In light of this, TSO® is not expected to affect QT interval.

Literature Case Reports and Reviews

Early data on the tolerability of TSO® in humans was obtained after an experimental self-infection of a 23-year old healthy individual with TSO®. Beer (1971) reported in the British Medical Journal a case of experimental self-infection of T. suis in a 23 year old male. A single oral dose of 1000 eggs were taken orally. The patient experienced no symptoms of distress and no diarrhea. There was no change in the differential white count. Beer reports an infection was established by day 60 with recovery of approximately 20 eggs per gram of stool following the estimated time for maturation. Beer reported that humans were able to be infected with T. suis. This observation was one of several considerations that led to the original proposal that T. suis would be a good therapeutic choice.

Kradin et al (Kradin 2006) found what he and his colleagues described as a sexually mature adult trichurid by cecal biopsy in a 16 year old patient who underwent TSO® treatment for CD. They identified immature helminths in the ileocecal region. However, they concluded that the presence of an adult male helminth in the cecum indicates that maturation to the sexual stage of T. suis does occur in man. Summers et al (2006) commented on this case by stating it was highly unlikely that T. suis causes prolonged colonization of humans. In their studies of T. suis ova therapy in ulcerative colitis and Crohn’s disease, they performed colonoscopy in some patients and occasionally saw helminths of variable size and maturity. Ova in the stool were never detected despite regular examinations, suggesting that the worms never reached maturity. In patients who had been off ova therapy for several months, including some patients who were taking various immunosuppressants, they never saw eggs in the stool or parasitic forms on colonoscopy. Also, even if eggs are produced, they will be immature. They cannot autoinfect the host or directly transmit infection to people nearby; the eggs need to rest in moist soil for perhaps a month to reach maturity and become the infective form. Normal hygienic practice will prevent any transmission of infection because only immature eggs can be passed in the stool. Once again, even farmers who raise pigs do not get sick from T. suis exposure. Farmers who are frequently exposed to T. suis by close contact with colonized pigs have never develop clinically associated disease or chronic T. suis colonization. Thus, Kradin suggestion that prolonged parasitic colonization may be a concern is speculation.

Van Kruiningen and West (Van Kruiningen 2005) speculated that aberrant migration of the developing larvae could occur. However, based on the biology and structure of the T. suis larvae, Reddy & Fried (2009) consider it unlikely that T. suis could enter the human lymphatic or venous system by means of the gut submucosa. There are no observations of T. suis producing disease in humans. Humans have cohabitated with pigs for centuries. In unhygienic areas where porcine stool is distributed onto the soil, eggs from these infected pigs can reach maturity in the surrounding soil. People would have been constantly exposed to viable mature eggs. A complete lack of reported disease suggests they are remarkably safe. In addition, Trichuris trichiura has not been reported to migrate aberrantly even in HIV-infected individuals in Africa.

Van Kruiningen cites Henry (Henry 1970) as an example of aberrant migration in an unnatural host. “When T. suis was identified in wild boars (Sus scrofa), a foreign host for them, they had traveled an aberrant pathway to as far as the kidneys”. However, the Appalachian wild boar is the same animal as the domesticated pig; the American wild boar is simply a feral pig (Susscrofa). Thus, it is not a “foreign host”. Furthermore, the Henry report is from field autopsies of killed trapped boars. The helminth they found on top of a kidney likely resulted from artifactual spillage rather than true migration. Aberrant migration has not been reported in domestic pigs
(same host).

Hsu et al (Hsu 2005) raised the theoretical concerns regarding the fate of TSO® in patients who do not respond to therapy (theoretical risk:benefit ratio). Summers et al (Summers 2006) countered this concern by stating that hundreds of patients had received TSO® treatment in Europe without reported side-effects and added that if symptoms were to occur the causative agent could be easily treated with antihelminthics.

Heitman et al. (Heitman 2007) published a case report of an 8-year old boy who was treated with TSO® for refractory eosinophilic colitis. After receiving 10 doses of TSO® (titration from 100 to 2000 eggs), lactoferrin decreased from 500 mg/1 to 14.5 mg/1 and his colitis symptoms improved (bloody diarrhea subsided). No adverse events were reported.

Abner et al (Abner 2002) demonstrated that Campylobacter jejuni to be pathogenic in the presence of T. suis in pigs. Shin et al (Shin 2004) reported a case of life-threatening C. jejuni colitis associated with concomitant Trichuris ova in the feces in a Somalian patient. Summers et al (Summers 2006) pointed out that Campylobacter jejuni alone causes a severe life- threatening colitis and it is highly speculative whether coinfection with Trichuris accentuates such infections. Although the abstract of the article reported T.suis ova in the stool, the actual text stated that “microscopy showed Trichuris trichiura larvae”. Trichuris larvae are not normally seen in stool specimens, no adult forms were seen on colonoscopy, and improvement occurred
prior to treatment with mebendazole. If this Somolian immigrant was colonized, it was almost certainly the result of a helminth other than T. suis or the patient may have had strongyloides. We suspect this was an error that the authors failed to address.

When patients have an IBD flare, they will usually develop diarrhea (often bloody diarrhea). Stool is always checked for bacterial pathogens. These patients then receive powerful immune suppressants like high dose steroids, azathioprine, methotrexate, and biologics (e.g anti-TNF). Any of these medications would worsen a Campylobacter jejuni infection. So this concern is nothing new. Co-infection with bacterial pathogens, worsening IBD and use of powerful immune suppressants has not proven to be a significant concern in current medical practice.