Biopeptides and immune exclusion

Successful probiotics have the ability to adhere to the gut preventing attachment of pathogenic bacteria and help to restore immunologic quiescence. Unfortunately, Nandini Dendukuri and colleagues' systematic review1 was unable to find clinical benefit for treatment of Clostridium difficile–associated diarrhea (CDAD).

The important question is, Can probiotics or biologically active peptides induce a lasting immune response? Probiotics stimulate the synthesis and secretion of polymeric IgA, the antibody that protects mucosal surfaces against harmful bacterial invasion, the concept underlying immune exclusion. Appropriate colonization with probiotics can thus help to produce a balanced T helper (Th) cell response. An imbalance in Th cells partly contributes to clinical disease: Th2 imbalance contributes to atopic disease and Th1 imbalance contributes to Crohn's disease and Helicobacter pylori-induced gastritis.

LeBlanc and colleagues2 demonstrated that oral administration of an immunologically active peptide (derived after extensive proteolysis by Lactobacillus helveticus) enhanced immunomodulatory action and increased IgA+ B-lymphocytes in the intestinal lamina propria of mice, and offered protection against further Escherichia coli 0157:H7 challenge. Benyacoub and colleagues3 showed that the probiotic organism Enterococcus faecium SF68 offered specific humoral and cellular (increased CD4+ in Peyer's patches and spleen) responses against Giardia intestinalis infection in mice.

Perhaps we are just beginning to understand the complex coexistence and interdependence between microbes and man.