Microbiology
Abstract
Secreted phospholipase A2-IIA (sPLA2-IIA) hydrolyzes phospholipids to liberate lysophospholipids and fatty acids. Given its poor activity toward eukaryotic cell membranes, its role in the generation of proinflammatory lipid mediators is unclear. Conversely, sPLA2-IIA efficiently hydrolyzes bacterial membranes. Here, we show that sPLA2-IIA affects the immune system by acting on the intestinal microbial flora. Using mice overexpressing transgene-driven human sPLA2-IIA, we found that the intestinal microbiota was critical for both induction of an immune phenotype and promotion of inflammatory arthritis. The expression of sPLA2-IIA led to alterations of the intestinal microbiota composition, but housing in a more stringent pathogen-free facility revealed that its expression could affect the immune system in the absence of changes to the composition of this flora. In contrast, untargeted lipidomic analysis focusing on bacteria-derived lipid mediators revealed that sPLA2-IIA could profoundly alter the fecal lipidome. The data suggest that a singular protein, sPLA2-IIA, produces systemic effects on the immune system through its activity on the microbiota and its lipidome.
Authors
Etienne Doré, Charles Joly-Beauparlant, Satoshi Morozumi, Alban Mathieu, Tania Lévesque, Isabelle Allaeys, Anne-Claire Duchez, Nathalie Cloutier, Mickaël Leclercq, Antoine Bodein, Christine Payré, Cyril Martin, Agnes Petit-Paitel, Michael H. Gelb, Manu Rangachari, Makoto Murakami, Laetitia Davidovic, Nicolas Flamand, Makoto Arita, Gérard Lambeau, Arnaud Droit, Eric Boilard
Abstract
Commensal microbes critically regulate skeletal homeostasis, yet the impact of specific microbiota communities on osteoimmune response mechanisms is unknown. To discern osteoimmunomodulatory effects imparted by the commensal oral microbiota that are distinct from the systemic microbiota, osteoimmunology studies were performed in both alveolar bone and non-oral skeletal sites of specific-pathogen-free (SPF) vs. germ-free (GF) mice, and SPF mice subjected to saline vs. chlorhexidine oral rinses. SPF vs. GF mice had reduced cortical/trabecular bone and an enhanced pro-osteoclastic phenotype in alveolar bone. Toll-like receptor signaling and TH17 cells that have known pro-osteoclastic actions were increased in alveolar, but not long-bone marrow, of SPF vs. GF mice. MHC class-II antigen presentation genes, activated dendritic cells, and activated CD4+ T-cells were elevated in alveolar, but not long-bone marrow, of SPF vs. GF mice. These findings were substantiated by in vitro allostimulation studies demonstrating increased activated dendritic cells derived from alveolar, but not long-bone marrow, of SPF vs. GF mice. Chlorhexidine antiseptic rinse depleted the oral, but not gut, bacteriome in SPF mice. Findings from saline- vs. chlorhexidine-treated SPF mice corroborated outcomes from SPF vs. GF mice, which reveals that the commensal oral microbiota imparts osteoimmunomodulatory effects separate from the systemic microbiome.
Authors
Jessica D. Hathaway-Schrader, Johannes D. Aartun, Nicole A. Poulides, Megan B. Kuhn, Blakely E. McCormick, Michael E. Chew, Emily Huang, Richard P. Darveau, Caroline Westwater, Chad M. Novince
Abstract
A hallmark of chronic bacterial infections is the long-term persistence of 1 or more pathogen species at the compromised site. Repeated detection of the same bacterial species can suggest that a single strain or lineage is continually present. However, infection with multiple strains of a given species, strain acquisition and loss, and changes in strain relative abundance can occur. Detecting strain-level changes and their effects on disease is challenging because most methods require labor-intensive isolate-by-isolate analyses, and thus, only a few cells from large infecting populations can be examined. Here, we present a population-level method for enumerating and measuring the relative abundance of strains called population multi-locus sequence typing (PopMLST). The method exploits PCR amplification of strain-identifying polymorphic loci, next-generation sequencing to measure allelic variants, and informatic methods to determine whether variants arise from sequencing errors or low-abundance strains. These features enable PopMLST to simultaneously interrogate hundreds of bacterial cells that are cultured en masse from patient samples or are present in DNA directly extracted from clinical specimens without ex vivo culture. This method could be used to detect epidemic or super-infecting strains, facilitate understanding of strain dynamics during chronic infections, and enable studies that link strain changes to clinical outcomes.
Authors
Sarah J. Morgan, Samantha L. Durfey, Sumedha Ravishankar, Peter Jorth, Wendy Ni, Duncan T. Skerrett, Moira L. Aitken, Edward F. McKone, Stephen J. Salipante, Matthew C. Radey, Pradeep K. Singh
Abstract
Identification and analysis of fungal communities commonly rely on internal transcribed spacer (ITS)-based amplicon sequencing. There is no gold standard to infer and classify fungal constituents since methodologies have been adapted from analyses of bacterial communities. To achieve high resolution inference of fungal constituents, we customized a DADA2-based pipeline using a mix of eleven medically relevant fungi. While DADA2 allowed the discrimination of ITS1 sequences differing by single nucleotides, quality filtering, sequencing bias, and database selection were identified as key variables determining the accuracy of sample inference. Due to species-specific differences in sequencing quality, default filtering settings removed most reads that originated from Aspergillus species, Saccharomyces cerevisiae, and Candida glabrata. By fine-tuning the quality filtering process, we achieved an improved representation of the fungal communities. By adapting a wobble nucleotide in the ITS1 forward primer region, we further increased the yield of S. saccharomyces and C. glabrata sequences. Finally, we showed that a BLAST-based algorithm based on the UNITE+INSD or the NCBI NT database achieved a higher reliability in species-level taxonomic annotation than the naïve Bayesian classifier implemented in DADA2. These steps optimized a robust fungal ITS1 sequencing pipeline that, in most instances, enabled species level-assignment of community members.
Authors
Thierry Rolling, Bing Zhai, John Frame, Tobias M. Hohl, Ying Taur
Abstract
Oral conditions are relatively common in patients with inflammatory bowel disease (IBD). However, the contribution of oral maladies to gut inflammation remains unexplored. Here, we investigated the impact of periodontitis on disease phenotypes of IBD patients. In all, 60 IBD patients (42 with ulcerative colitis [UC] and 18 with Crohn’s disease [CD]) and 45 non-IBD healthy controls (HCs) were recruited for this clinical investigation. The effects of incipient periodontitis on the oral and gut microbiome, IBD characteristics were examined. In addition, patients were prospectively monitored up to 12 months after enrollment. We found that in both UC and CD patients, the gut microbiome was significantly more similar to the oral microbiome than in HCs, suggesting that ectopic gut colonization by oral bacteria is increased in IBD patients. Incipient periodontitis did not further enhance gut colonization by oral bacteria. The presence of incipient periodontitis did not significantly affect the clinical outcomes of UC and CD patients. However, the short Crohn’s disease activity index increased in CD patients with incipient periodontitis but declined or unchanged during the study period in patients without periodontitis. Thus, early periodontitis may associate with worse clinically symptoms in some patients with CD.
Authors
Jin Imai, Hitoshi Ichikawa, Sho Kitamoto, Jonathan L. Golob, Motoki Kaneko, Junko Nagata, Miho Takahashi, Merritt G. Gillilland, Rika Tanaka, Hiroko Nagao-Kitamoto, Atsushi Hayashi, Kohei Sugihara, Shrinivas Bishu, Shingo Tsuda, Hiroyuki Ito, Seiichiro Kojima, Kazunari Karakida, Masashi Matsushima, Takayoshi Suzuki, Katsuto Hozumi, Norihito Watanabe, William V. Giannobile, Takayuki Shirai, Hidekazu Suzuki, Nobuhiko Kamada
Abstract
Cerebral malaria (CM) affects children and adults, but brain swelling is more severe in children. To investigate features associated with brain swelling in malaria, we performed blood profiling and brain MRI in a cohort of pediatric and adult patients with CM in Rourkela, India, and compared them with an African pediatric CM cohort in Malawi. We determined that higher plasma Plasmodium falciparum histidine rich protein 2 (PfHRP2) levels and elevated var transcripts that encode for binding to endothelial protein C receptor (EPCR) were linked to CM at both sites. Machine learning models trained on the African pediatric cohort could classify brain swelling in Indian children CM cases but had weaker performance for adult classification, due to overall lower parasite var transcript levels in this age group and more severe thrombocytopenia in Rourkela adults. Subgrouping of patients with CM revealed higher parasite biomass linked to severe thrombocytopenia and higher Group A–EPCR var transcripts in mild thrombocytopenia. Overall, these findings provide evidence that higher parasite biomass and a subset of Group A–EPCR binding variants are common features in children and adult CM cases, despite age differences in brain swelling.
Authors
Praveen K. Sahu, Fergal J. Duffy, Selasi Dankwa, Maria Vishnyakova, Megharay Majhi, Lukas Pirpamer, Vladimir Vigdorovich, Jabamani Bage, Sameer Maharana, Wilson Mandala, Stephen J. Rogerson, Karl B. Seydel, Terrie E. Taylor, Kami Kim, D. Noah Sather, Akshaya Mohanty, Rashmi R. Mohanty, Anita Mohanty, Rajyabardhan Pattnaik, John D. Aitchison, Angelika Hoffman, Sanjib Mohanty, Joseph D. Smith, Maria Bernabeu, Samuel C. Wassmer
Abstract
BACKGROUND. Catheterization facilitates continuous bacteriuria, for which the clinical significance remains unclear. This study aimed to determine the clinical presentation, epidemiology, and dynamics of bacteriuria in a cohort of long-term catheterized nursing home residents. METHODS. Prospective urine culture, urinalysis, chart review, and assessment of signs and symptoms of infection were performed weekly for 19 study participants over 7 months. All bacteria ≥103 cfu/ml were cultured, isolated, identified, and tested for susceptibility to select antimicrobials. RESULTS. 226 of the 234 urines were polymicrobial (97%), with an average of 4.7 isolates per weekly specimen. 228 urines (97%) exhibited ≥106 CFU/ml, 220 (94%) exhibited abnormal urinalysis, 126 (54%) were associated with at least one possible sign or symptom of infection, 82 (35%) would potentially meet a standardized definition of CAUTI, but only 3 had a caregiver diagnosis of CAUTI. 286 (30%) of bacterial isolates were resistant to a tested antimicrobial agent, and bacteriuria composition was remarkably stable despite a combined total of 54 catheter changes and 23 weeks of antimicrobial use. CONCLUSIONS. Bacteriuria composition was largely polymicrobial, including persistent colonization by organisms previously considered to be urine culture contaminants. Neither antimicrobial use nor catheter changes sterilized the urine, at most resulting in transient reductions in bacterial burden followed by new acquisition of resistant isolates. Thus, this patient population exhibits a high prevalence of bacteriuria coupled with potential indicators of infection, necessitating further exploration to identify sensitive markers of true infection. FUNDING. This work was supported by the NIH (R00 DK105205, R01 DK123158, UL1 TR001412)
Authors
Chelsie E. Armbruster, Aimee L. Brauer, Monica S. Humby, Jiahui Shao, Saptarshi Chakraborty
Abstract
The syndrome of spontaneous preterm birth (sPTB) presents a challenge to mechanistic understanding, effective risk stratification, and management. Individual associations between sPTB, ethnicity, vaginal microbiota, metabolome and innate immune response are known, but not fully understood and knowledge has yet to impact clinical practice. Here we use multi-data type integration and composite statistical models to gain insight into sPTB risk by exploring the cervicovaginal environment of an ethnically heterogenous pregnant population (n=346 women; n=60 sPTB <37 weeks’ gestation, including n=27 sPTB <34 weeks). Analysis of cervicovaginal samples (10-15+6 weeks) identified novel interactions between risk of sPTB and microbiota, metabolite, and maternal host defense molecules. Statistical modelling identified a composite of metabolites (leucine, tyrosine, aspartate, lactate, betaine, acetate and Ca2+) associated with risk of sPTB <37 weeks (Area Under the Curve - AUC 0.752). A combination of glucose, aspartate, Ca2+ and Lactobacillus crispatus and L. acidophilus relative abundance, identified risk of early sPTB <34 weeks, (AUC 0.758); improved by ethnicity stratification (AUC 0.835). Increased relative abundance of L. acidophilus appeared protective against sPTB <34 weeks. By using cervicovaginal fluid samples, we demonstrate the potential of multi-datatype integration for developing composite models towards understanding the contribution of the vaginal environment to risk of sPTB.
Authors
Flavia Flaviani, Natasha L. Hezelgrave, Tokuwa Kanno, Erica M. Prosdocimi, Evonne Chin-Smith, Alexandra E. Ridout, Djuna K. von Maydell, Vikash Mistry, William G. Wade, Andrew H. Shennan, Konstantina Dimitrakopoulou, Paul T. Seed, Andrew James Mason, Rachel M. Tribe
Abstract
Background: The fungal cell-wall constituent 1,3-beta-D-glucan (BDG) is a pathogen-associated molecular pattern that can stimulate innate immunity. We hypothesized that BDG from colonizing fungi in critically-ill patients may translocate into the systemic circulation and be associated with host inflammation and outcomes. Methods: We enrolled 453 mechanically-ventilated patients with acute respiratory failure (ARF) without invasive fungal infection and measured BDG, innate immunity and epithelial permeability biomarkers in serially collected plasma samples. Results: Compared to healthy controls, ARF patients had significantly higher BDG levels (median [interquartile-range] 26 [15-49]pg/ml, p<0.001), whereas ARF patients with high BDG levels (≥40pg/ml, 31%) had higher odds for assignment to the prognostically adverse hyperinflammatory subphenotype (odds ratio [confidence interval] 2.88 [1.83-4.54], p<0.001). Baseline BDG levels were predictive of fewer ventilator-free days and worse 30-day survival (adjusted p<0.05). Integrative analyses of fungal colonization and epithelial barrier disruption suggested that BDG may translocate from either the lung or gut compartment. We validated the associations between plasma BDG and host inflammatory responses in 97 hospitalized patients with COVID-19. Conclusions: BDG measurements offered prognostic information in critically-ill patients without fungal infections. Further research in the mechanisms of translocation and innate immunity recognition and stimulation may offer new therapeutic opportunities in critical illness.
Authors
Georgios D. Kitsios, Daniel Kotok, Haopu Yang, Malcolm A. Finkelman, Yonglong Zhang, Noel Britton, Xiaoyun Li, Marina S. Levochkina, Amy K. Wagner, Caitlin Schaefer, John J. Villandre, Rui Guo, John W. Evankovich, William Bain, Faraaz Shah, Yingze Zhang, Barbara A. Methé, Panayiotis V. Benos, Bryan J. McVerry, Alison Morris
Abstract
TNFRSF13B encodes the "transmembrane-activator and CAML-interactor" (TACI) receptor, which drives plasma cell differentiation. Although TNFRSF13B supports host defense, dominant-negative TNFRSF13B alleles are common in humans and other species and only rarely associate with disease. We reasoned the high frequency of disruptive TNFRSF13B alleles reflects balancing selection, the loss of function conferring advantage in some settings. Testing that concept, we asked whether and how a common human dominant negative variant, TNFRSF13B A181E, imparts resistance to enteric pathogens. Mice engineered to express mono-allelic or bi-allelic A144E variants of tnrsf13B, corresponding to A181E exhibited striking resistance to pathogenicity and transmission of C. rodentium, a murine pathogen that models enterohemorrhagic E. coli, and resistance was principally owed to deficiency of natural IgA in the intestine. In wild type mice with gut IgA and in mutant mice fed IgA, binding of Ig induces expression of LEE encoded virulence genes, which confer pathogenicity and transmission. C. rodentium and probably some other enteric organisms thus appropriated binding of otherwise protective antibodies to signal induction of the virulence program and the high prevalence of TNFRSF13B dominant negative variants thus reflects balancing selection.
Authors
Jeffrey L. Platt, Mayara Garcia de Mattos Barbosa, Daniel Huynh, Adam R. Lefferts, Juhi Katta, Cyra Kharas, Peter L. Freddolino, Christine Marie Bassis, Christiane E. Wobus, Raif Geha, Richard J. Bram, Gabriel Nunez, Nobuhiko Kamada, Marilia Cascalho
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