Effect of hookworm infection on wheat challenge in celiac disease--a randomised double-blinded placebo controlled trial

Abstract

Background and aims: The association between hygiene and prevalence of autoimmune disease has been attributed in part to enteric helminth infection. A pilot study of experimental infection with the hookworm Necator americanus was undertaken among a group of otherwise healthy people with celiac disease to test the potential of the helminth to suppress the immunopathology induced by gluten.

Methods: In a 21-week, double-blinded, placebo-controlled study, we explored the effects of N. americanus infection in 20 healthy, helminth-naïve adults with celiac disease well controlled by diet. Staged cutaneous inoculations with 10 and 5 infective 3(rd) stage hookworm larvae or placebo were performed at week-0 and -12 respectively. At week-20, a five day oral wheat challenge equivalent to 16 grams of gluten per day was undertaken. Primary outcomes included duodenal Marsh score and quantification of the immunodominant α-gliadin peptide (QE65)-specific systemic interferon-γ-producing cells by ELISpot pre- and post-wheat challenge.

Results: Enteric colonisation with hookworm established in all 10 cases, resulting in transiently painful enteritis in 5. Chronic infection was asymptomatic, with no effect on hemoglobin levels. Although some duodenal eosinophilia was apparent, hookworm-infected mucosa retained a healthy appearance. In both groups, wheat challenge caused deterioration in both primary and several secondary outcomes.

Conclusions: Experimental N. americanus infection proved to be safe and enabled testing its effect on a range of measures of the human autoimmune response. Infection imposed no obvious benefit on pathology.

Trial registration: ClinicalTrials.gov NCT00671138.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist. Envoi Specialist Pathologists, Brisbane, QLD, Australia contributed to the processing and the interpretation (Prof. Clouston) of the histological material, but neither the organisation nor any employee has any commercial interest beyond this support nor a competing interest. Envoi's involvement does not affect or alter the authors' adherence to all the PLoS ONE policies on sharing data and materials.

Figures

Figure 1. CONSORT flowchart.

Figure 2. Recruitment and Protocol.

Recruitment and summation of those excluded post screening (A), and trial outline (B).

Figure 3. Representative photographs of parasitic infection (A) Adult hookworm (B) Inoculation site.

Figure 4. Symptom responses to hookworm infection.

Control group is indicated by black circles, hookworm group by grey squares, values are mean +/− SEM. (A) pain events, (B) bowel motions/day, (C) flatulence, (D) skin rash, (E) lethargy, (F) wellbeing. Area under the curve analysis followed by Mann-Whitney U test to compare between groups showed that pain events (A) was significantly different between the groups.

Figure 5. Blood cell and marker levels.

(A) white cell, (B) eosinophil (C) hemoglobin. Control group is indicated by black circles, hookworm group by grey squares, values are mean +/− SEM. Data was analyzed by two-way ANOVA: significant effects of time and interaction was shown in (B), and post-hoc one-way ANOVA on each group showed the differences between timepoints as indicated.

Figure 6. Histological and immunological results.

(A) Marsh score and (B) IFN-γ ELISpot. Data was analyzed by two-way ANOVA: significant effects of time only were shown as indicated, no significant effect of group or interaction was found in (A) or (B).