Anti-LPS antibodies protect against Klebsiella pneumoniae by empowering neutrophil-mediated clearance without neutralizing TLR4

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Abstract

Initial promising results with immune sera guided early human mAb approaches against Gram-negative sepsis to an LPS neutralization mechanism, but these efforts failed in human clinical trials. Emergence of multidrug resistance has renewed interest in pathogen-specific mAbs. We utilized a pair of antibodies targeting Klebsiella pneumoniae LPS, one that both neutralizes LPS/TLR4 signaling and mediates opsonophagocytic killing (OPK) (54H7) and one that only promotes OPK (KPE33), to better understand the contribution of each mechanism to mAb protection in an acutely lethal pneumonia model. Passive immunization 24 hours prior to infection with KPE33 protected against lethal infection significantly better than 54H7, while delivery of either mAb 1 hour after infection resulted in similar levels of protection. These data suggest that early neutralization of LPS-induced signaling limits protection afforded by these mAbs. LPS neutralization prevented increases in the numbers of γδT cells, a major producer of the antimicrobial cytokine IL-17A, the contribution of which was confirmed using il17a-knockout mice. We conclude that targeting LPS for OPK without LPS signaling neutralization has potential to combat Gram-negative infection by engaging host immune defenses, rather than inhibiting beneficial innate immune pathways.

Authors

Taylor S. Cohen, Mark Pelletier, Lily Cheng, Meghan E. Pennini, Jessica Bonnell, Romana Cvitkovic, Chew-shun Chang, Xiaodong Xiao, Elisabetta Cameroni, Davide Corti, Elena Semenova, Paul Warrener, Bret R. Sellman, JoAnn Suzich, Qun Wang, C. Kendall Stover

ATG16L1 governs placental infection risk and preterm birth in mice and women

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Abstract

The placenta is a barrier against maternal-fetal transmission of pathogens. Placental infections can cause several adverse pregnancy outcomes, including preterm birth (PTB). Yet, we have limited knowledge regarding the mechanisms the placenta uses to control infections. Here, we show that autophagy, a cellular recycling pathway important for host defense against pathogens, and the autophagy gene Atg16L1 play a key role in placental defense and are negatively associated with PTB in pregnant women. First, we demonstrate that placentas from women who delivered preterm exhibit reduced autophagy activity and are associated with higher infection indicators. Second, we identify the cellular location of the autophagy activity as being in syncytial trophoblasts. Third, we demonstrate that higher levels of autophagy and ATG16L1 in human trophoblasts were associated with increased resistance to infection. Accordingly, loss of autophagy or ATG16L1 impaired trophoblast antibacterial defenses. Fourth, we show that Atg16l1-deficient mice gave birth prematurely upon an inflammatory stimulus and their placentas were significantly less able to withstand infection. Finally, global induction of autophagy in both mouse placentas and human trophoblasts increased infection resistance. Our study has significant implications for understanding the etiology of placental infections and prematurity and developing strategies to mitigate placental infection–induced PTB.

Authors

Bin Cao, Colin Macones, Indira U. Mysorekar

Bladder catheterization increases susceptibility to infection that can be prevented by prophylactic antibiotic treatment

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Abstract

Catheter-associated urinary tract infections (CAUTI) are the most common hospital-associated infections. Here, we report that bladder catheterization initiated a persistent sterile inflammatory reaction within minutes of catheter implantation. Catheterization resulted in increased expression of genes associated with defense responses and cellular migration, with ensuing rapid and sustained innate immune cell infiltration into the bladder. Catheterization also resulted in hypersensitivity to Enterococcus faecalis and uropathogenic Escherichia coli (UPEC) infection, in which colonization was achieved using an inoculum 100-fold lower than the ID₉₀ for infection of an undamaged urothelium with the same uropathogens. As the time of catheterization increased, however, colonization by the Gram-positive uropathogen E. faecalis was reduced, whereas catheterization created a sustained window of vulnerability to infection for Gram-negative UPEC over time. As CAUTI contributes to poorer patient outcomes and increased health care expenditures, we tested whether a single prophylactic antibiotic treatment, concurrent with catheterization, would prevent infection. We observed that antibiotic treatment protected against UPEC and E. faecalis bladder and catheter colonization as late as 6 hours after implantation. Thus, our study has revealed a simple, safe, and immediately employable intervention, with the potential to decrease one of the most costly hospital-incurred infections, thereby improving patient and health care economic outcome.

Authors

Matthieu Rousseau, H.M. Sharon Goh, Sarah Holec, Matthew L. Albert, Rohan B.H. Williams, Molly A. Ingersoll, Kimberly A. Kline

Paneth cell defects in Crohn’s disease patients promote dysbiosis

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Abstract

BACKGROUND. Paneth cell dysfunction has been implicated in a subset of Crohn’s disease (CD) patients. We previously stratified clinical outcomes of CD patients by using Paneth cell phenotypes, which we defined by the intracellular distribution of antimicrobial proteins. Animal studies suggest that Paneth cells shape the intestinal microbiome. However, it is unclear whether Paneth cell phenotypes alter the microbiome complexity in CD subjects. Therefore, we analyzed the correlation of Paneth cell phenotypes with mucosal microbiome composition and ileal RNA expression in pediatric CD and noninflammatory bowel disease (non-IBD) patients.

METHODS. Pediatric CD (n = 44) and non-IBD (n = 62) patients aged 4 to 18 were recruited prior to routine endoscopic biopsy. Ileal mucosal samples were analyzed for Paneth cell phenotypes, mucosal microbiome composition, and RNA transcriptome.

RESULTS. The prevalence of abnormal Paneth cells was higher in pediatric versus adult CD cohorts. For pediatric CD patients, those with abnormal Paneth cells showed significant changes in their ileal mucosal microbiome, highlighted by reduced protective microbes and enriched proinflammatory microbes. Ileal transcriptome profiles showed reduced transcripts for genes that control oxidative phosphorylation in CD patients with abnormal Paneth cells. These transcriptional changes in turn were correlated with specific microbiome alterations. In non-IBD patients, a subset contained abnormal Paneth cells. However, this subset was not associated with alterations in the microbiome or host transcriptome.

CONCLUSION. Paneth cell abnormalities in human subjects are associated with mucosal dysbiosis in the context of CD, and these changes are associated with alterations in oxidative phosphorylation, potentially in a feedback loop.

FUNDING. The research was funded by Helmsley Charitable Trust (to T.S. Stappenbeck, R.J. Xavier, and D.P.B. McGovern), Crohn’s and Colitis Foundation of America (to N.H. Salzman, T.S. Stappenbeck, R.J. Xavier, and C. Huttenhower), and Doris Duke Charitable Foundation grant 2014103 (to T.C. Liu).

Authors

Ta-Chiang Liu, Bhaskar Gurram, Megan T. Baldridge, Richard Head, Vy Lam, Chengwei Luo, Yumei Cao, Pippa Simpson, Michael Hayward, Mary L. Holtz, Pavlos Bousounis, Joshua Noe, Diana Lerner, Jose Cabrera, Vincent Biank, Michael Stephens, Curtis Huttenhower, Dermot P.B. McGovern, Ramnik J. Xavier, Thaddeus S. Stappenbeck, Nita H. Salzman