A Prospective Longitudinal Study of Fecal Microbiome and Calprotectin to Predict Response to Biological Therapy in Patients With Crohn's Disease

Crohn's disease (CD) is a chronic relapsing-remitting systemic inflammatory disease, affecting any part of the gastrointestinal tract. Patients frequently present with abdominal pain, fever, and symptoms of bowel obstruction or diarrhea with passage of blood or mucus, or both. It can lead to significant morbidity and disability in some cases. Population-based studies revealed that up to 50% of CD patients required surgery within 10 years from diagnosis.Only 24% remain in remission over their lifetime disease course.

Biological therapy with anti-tumor necrosis factor (TNF) alpha is the established treatment of choice for the management of moderate to severe Crohn's disease. However, its efficacy in an individual patient is the unpredictable and long-term outcome is still suboptimal. Almost one-third of CD patients showed no response to anti-TNF and two-thirds do not achieve remission.The rate of loss of response after 1 year of infliximab therapy ranges between 23% and 46%.4 Identifying biomarkers which can predict treatment response is thus of utmost importance and can allow personalized management.

Several biomarkers have been identified in predicting treatment response. C reactive protein (CRP) is an acute phase reactant with a short half-life of only 19 hours. CD Patients with elevated baseline CRP levels (>3mg/L) responded to infliximab treatment better and early normalisation of CRP correlated with sustained long-term response to infliximab therapy. Similar results were shown in adalimumab therapy. CD patients who had achieved normalisation of CRP (<3mg/L) at both week 4 and week 12 were less likely to discontinue adalimumab and had sustained clinical benefit.

Fecal calprotectin (FC) is a calcium and zinc binding protein largely confined to the neutrophil granulocytes and macrophages and is a very sensitive marker for detection of inflammation in the gastrointestinal tract. FC levels dropped significantly in CD patients who responded to infliximab therapy. A decrease in FC level after therapy has been demonstrated to be associated with clinical, endoscopic and histological improvements. Moreover, a study has demonstrated that combination of CRP and FC represented a good predictor of relapse of CD among patients on anti-metabolite therapy after infliximab was stopped.

In inflammatory bowel disease , altered fecal microbiota signatures have been consistently reported which included a reduction in biodiversity with lower proportions of Firmicutes and increases in Proteobacteria and Bacteroidetes phylum members.Moreover, overall bacterial diversity is consistently decreased during intestinal inflammation. Besides, CD patients have richer fungal species and higher microbiome diversities in mucosal biopsies. Several fungal species, including Candida spp., Gibberella moniliformis, Alternaria brassicicola and Cryptococcus neoformans, are increased in tissues from CD patients. CD patients may harbor increased numbers of bacteriophages in inflamed tissue and feces, though no specific viruses have been associated with human IBDs to date.