The therapeutic efficacy of live probiotic strains may be limited

Kuitunen reported that probiotic supplementation of pregnant mothers and their offspring conferred protection from allergic disease only to cesarean-delivered children, suggesting that probiotic treatment may be beneficial only in subpopulations of patients (ie, those with abnormal or disrupted gut microbiota). It is also clear that the immunoregulatory actions of certain LAB can be inhibited in the presence of other strains. L reuteri, a poor inducer of IL-12 from murine DCs, inhibits IL-12, IL-6, and TNF-a induction by the otherwise strong HQ Viagra online  cytokine inducer L casei, whereas both Bifidobacterium bifidum and L reuteri can inhibit Lactobacillus acidophilus-induced IL-12 production by DCs and accordingly abrogate IFN-g production by NK cells.

This suggests that the benefits of mixed strain probiotic preparations may actually be less than the sum of their parts. How the existing commensal LAB and other bacteria composing the host microbiota might influence immunomodulatory action of a single orally administered strain is also unknown. Other factors that have not been fully explored and may influence therapeutic efficacy include the fact that the immune response to candidate probiotics may depend on the growth phase of the bacteria. Furthermore, there has also been little examination of the immunomodulatory effects of long-term exposure to probiotics, and one study in mice suggests that some of the extraintestinal immune effects may be lost with sustained treatment.

Conclusions

For the reasons outlined previously, the therapeutic efficacy of live probiotic strains may be limited. However, alternative approaches may be developed. To date a number of microbial cell wall components, including polysaccharides! and lipoteichoic acids as well as potential secreted products, have been identified as being critical to the immunoregulatory effects of certain bacteria and/or to mimic the effect of whole organisms, including the ability to attenuate the allergic airway response in mice (Fig 2).

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