nature publishing group Articles Basic Science Investigation Lactobacillus rhamnosus GG and its SpaC pilus adhesin modulate inflammatory responsiveness andTLR -related gene expression in the fetal human gut Kriston Ganguli1, Maria C. Collado2,3, Jaana Rautava4, Lei Lu1, Reetta Satokari5, Ingemar von Ossowski5, Justus Reunanen5, Willem M. de Vos5, Airi Palva5, Erika Isolauri6, Seppo Salminen2, W. Allan Walker1 and Samuli Rautava6 BACKGROUND: Bacterial contact in utero modulates fetal be regularly detected in amniotic fluid and placentae from and neonatal immune responses. Maternal probiotic supple- healthy term pregnancies (3–5). The presence of microbial mentation reduces the risk of immune-mediated disease in the DNA in infant meconium samples also suggests a prenatal infant. We investigated the immunomodulatory properties of origin for bacteria (6). The significance of this fetal microbial live Lactobacillus rhamnosus GG and its SpaC pilus adhesin in contact unrelated to infection remains poorly understood. human fetal intestinal models. It has gradually become evident that in utero microbial METHODS: Tumor necrosis factor (TNF)-α mRNA expression contact can modulate fetal immune function and this might was measured by qPCR in a human fetal intestinal organ cul- have an impact on both short- and long-term disease risk ture model exposed to live L. rhamnosus GG and proinflam- (1). Bacteria detected in the placenta after preterm birth matory stimuli. Binding of recombinant SpaC pilus protein to are reportedly associated with changes in systemic neonatal intestinal epithelial cells (IECs) was assessed in human fetal inflammatory responses (7). We have recently reported that intestinal organ culture and the human fetal intestinal epi- DNA from nonpathogenic bacteria in the placenta or amni- thelial cell line H4 by immunohistochemistry and immuno- otic fluid can modulate toll-like receptor (TLR)–related gene fluorescence, respectively. TLR-related gene expression in fetal expression in the fetal gut in term pregnancies without evi- ileal organ culture after exposure to recombinant SpaC was dence of chorionamnionitis (5). We have also provided data assessed by qPCR. suggesting that fetal intestinal innate immune gene expres- RESULTS: Live L. rhamnosus GG significantly attenuates sion can be modulated by maternal supplementation with pathogen-induced TNF-α mRNA expression in the human fetal specific probiotic bacteria (5). This may represent one of the gut. Recombinant SpaC protein was found to adhere to the mechanisms by which maternal probiotic supplementation fetal gut and to modulate varying levels of TLR-related gene during pregnancy is able to reduce the risk of immune-medi- expression. ated disease such as eczema in the infant (8,9). To date, the CONCLUSION: The human fetal gut is responsive to lumi- mechanisms responsible for in utero probiotic action have nal microbes. L. rhamnosus GG significantly attenuates fetal not been characterized. ­intestinal inflammatory responses to pathogenic bacteria. We hypothesized that Lactobacillus rhamnosus GG (ATCC The L. rhamnosus GG pilus adhesin SpaC binds to immature 53013) (L. rhamnosus GG), one of the most extensively investi- human IECs and directly modulates IEC innate immune gene gated probiotics, might elicit direct immunomodulatory effects expression. in the fetal gut. Moreover, we suggest that pilus structures on the surface of L. rhamnosus GG may be pivotal in this regard. We have recently reported that the adhesion of L. rhamnosus ontrary to the prevailing dogma, recent advances in under- GG is mediated by SpaCBA pili and that the SpaC pilus adhe- Cstanding the micro-ecology of the human placenta and sin, which is positioned at the pilus tip as well as decorates the fetus suggest that the fetus does not develop devoid of micro- shaft, is the major binding factor to human intestinal mucus, bial contact (1). Thus far, most research efforts to understand collagen and intestinal epithelial cells (IECs) (10–13). SpaC fetal bacterial contact have focused on chorionamnionitis, has also been shown to stimulate biofilm development and a major cause of preterm birth and neonatal infection (1,2). elicit immunomodulatory effects (14,15). We sought to test our Interestingly, however, microbes and microbial DNA can also hypothesis and investigate the immunomodulatory properties 1Mucosal Immunology and Biology Research Center, Massachusetts General Hospital for Children, Boston, Massachusetts; 2Functional Foods Forum, University of Turku, Turku, Finland; 3Department of Biotechnology, Institute of Agrochemistry and Food Technology, Spanish National Research Council (IATA-CSIC), Valencia, Spain; 4Institute of Dentistry, University of Turku, Turku, Finland; 5Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland; 6Department of Paediatrics, University of Turku, Turku, ­Finland. Correspondence: Samuli Rautava ([email protected]) Received 8 April 2014; accepted 3 October 2014; advance online publication 4 February 2015. doi:10.1038/pr.2015.5 528 Pediatric Research Volume 77 | Number 4 | April 2015 Copyright © 2015 International Pediatric Research Foundation, Inc. Probiotics and immunity in the fetal gut Articles of L. rhamnosus GG and its SpaC pilus adhesin using human Exposure to L. rhamnosus GG reduced this inflammatory fetal gut models. response to 3.1-fold (P = 0.009). In the fetal IEC line H4, exposure to live L. rhamnosus GG was observed to attenuate RESULTS IL-1β and TNF-α–induced IL-6 secretion on protein level as L. rhamnosus GG attenuates inflammatory cytokine production assessed by ELISA (Figure 2b,c) suggesting that fetal IECs are in response to pathogenic bacteria and proinflammatory signals susceptible to immunomodulation by L. rhamnosus GG. in the human fetal gut and IECs To assess the antiinflammatory potential of L. rhamnosus GG L. rhamnosus GG SpaC pilus adhesin binds to IECs in the fetal in the fetal human gut, we examined its effect on Salmonella human gut and modulates inflammatory cytokine responses enterica serovar Typhimurium SL1344 (S. Typhimurium)- To determine whether the adhesive SpaC pilin subunit of the induced tumor necrosis factor (TNF)-α mRNA expression L. rhamnosus GG SpaCBA pilus can bind to the human fetal in human fetal ileal organ culture. As shown in Figure 1a, intestinal epithelium, we used recombinant SpaC protein and TNF-α mRNA expression was increased 4.4-fold (P = 0.049) assessed its adhesion capacity using both human fetal ileal compared to baseline after exposure to viable S. Typhimurium. organ culture and cell culture models. In the fetal ileum, bind- On the other hand, live L. rhamnosus GG did not result in ing of recombinant SpaC to the epithelial lining was detected a significant increase in TNF-α mRNA levels (Figure 1a). by immunohistochemistry (Figure 3a,b). In a similar fashion, However, when human fetal ileal organ culture was exposed SpaC was observed to bind to the immature human intestinal to both S. Typhimurium and L. rhamnosus GG, TNF-α mRNA epithelial cell line H4 by immunofluorescence (Figure 3c,d). expression was reduced to −1.4-fold compared to baseline (P To test whether the binding of SpaC to IECs modulates = 0.026). Similar results were obtained when S. Typhimurium- inflammatory responses in fetal human IECs, H4 cells were induced IL-8 responses were measured on protein level in T84 incubated for 60 min with increasing concentrations of recom- cells (Figure 2a) suggesting that IECs are the target for poten- binant SpaC before stimulation with IL-1β, a proinflammatory tial probiotic action by L. rhamnosus GG. cytokine that shares the same intracellular signaling pathway To exclude the possibility that the observed reduction in with TLRs. A modest, dose-dependent reduction in inflam- inflammatory responsiveness might be the result of L. rham- matory responses as assessed by IL-6 protein secretion was nosus GG directly inhibiting S. Typhimurium, an experi- observed after exposure to SpaC (Figure 4a). Interestingly, ment using lipopolysaccharide (LPS), a cell wall component however, when H4 cells were stimulated with TNF-α, a potent of Gram-negative bacteria known to induce an inflammatory endogenous proinflammatory mediator using a distinct recep- response through TLR4 signaling, was conducted (Figure 1b). tor and intracellular pathway, exposure to SpaC lead to a mod- After LPS stimulation, TNF-α mRNA expression in the fetal est but statistically significant increase in IL-6 protein secretion gut was increased 11.9-fold compared to baseline (P = 0.003). (Figure 4b). ab 7 16 6 14 5 12 4 10 8 3 mRNA (fold change) α mRNA (fold change) α 6 TNF- 2 TNF- 4 ** * 1 2 0 0 Control LPS Control + LPS S. Typhimurium L. rhamnosus GGL. rhamnosus GG L. rhamnosus GG L. rhamnosus GG + S. Typhimurium Figure 1. Live Lactobacillus rhamnosus GG attenuates inflammatory responses in the fetal gut. (a) Salmonella Typhimurium induces expression of TNF-α mRNA in human fetal intestinal culture which is significantly attenuated by live L. rhamnosus GG. (b) Lipopolysaccharide (LPS), a proinflammatory cell wall component of Gram negative organisms, also induces a strong TNF-α mRNA in response in the human fetal gut and this reaction is significantly decreased by live L. rhamnosus GG. (*P < 0.05, **P < 0.01.) Copyright © 2015 International Pediatric Research Foundation, Inc. Volume 77 | Number 4 | April 2015 Pediatric Research 529 Articles Ganguli et al. L. rhamnosus GG SpaC pilus adhesin modulates immune gene a pathogenic organism, whereas