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Surana, Neeraj K.

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Surana

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Neeraj K.

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Surana, Neeraj K.

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Author's Publications: search.filters.isAuthorOfPublication.188a3dd0-c8e7-4b34-b2c4-593da51a97e1

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    Moving beyond microbiome-wide associations to causal microbe identification
    (2017) Surana, Neeraj K.; Kasper, Dennis
    Microbiome-wide association studies have established that numerous diseases are associated with changes in the microbiota1,2. These studies typically generate a long list of commensals implicated as biomarkers of disease, with no clear relevance to disease pathogenesis1–5. If the field is to move beyond correlations and begin to address causation, an effective system is needed for refining this catalog of differentially abundant microbes and allow for subsequent mechanistic studies1,4. Herein, we demonstrate that triangulation of microbe–phenotype relationships is an effective method for reducing the noise inherent in microbiota studies and enabling identification of causal microbes. We found that gnotobiotic mice harboring different microbial communities exhibited differential survival in a colitis model. Co-housing of these mice generated animals that had hybrid microbiotas and displayed intermediate susceptibility to colitis. Mapping of microbe–phenotype relationships in parental mouse strains and in mice with hybrid microbiotas identified the bacterial family Lachnospiraceae as a correlate for protection from disease. Using directed microbial culture techniques, we discovered Clostridium immunis, a previously unknown bacterial species from this family, that—when administered to colitis-prone mice—protected them against colitis-associated death. To demonstrate the generalizability of our approach, we used it to identify several commensal organisms that induce intestinal expression of an antimicrobial peptide. Thus, we have used microbe–phenotype triangulation to move beyond the standard correlative microbiome study and identify causal microbes for two completely distinct phenotypes. Identification of disease-modulating commensals by microbe–phenotype triangulation may be more broadly applicable to human microbiome studies.
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    Type I interferon signaling restrains IL-10R+ colonic macrophages and dendritic cells and leads to more severe Salmonella colitis
    (Public Library of Science, 2017) Stefan, Kailyn; Fink, Avner; Surana, Neeraj K.; Kasper, Dennis; Dasgupta, Suryasarathi
    Type I interferons (IFNα, IFNβ) are key regulators of innate and adaptive immunity, modulating the severity of both viral and bacterial infections. While type I IFN signaling leads to improved outcomes in viral infections, its role in bacterial infections is more contextual and depends on the specific pathogen and route of infection. Given the limited evidence on whether type I IFN signaling affects enteric bacterial pathogens, we investigated the role of this signaling pathway in Salmonella enterica serovar Typhimurium (S. typhimurium)–induced colitis. Comparing mice deficient in IFNAR1- the common receptor for IFNα and IFNβ- with wild-type mice, we found that type I IFN signaling leads to more rapid death, more severe colonic inflammation, higher serum levels of pro-inflammatory cytokines, and greater bacterial dissemination. Specific ablation of plasmacytoid dendritic cells (pDCs), which are prominent producers of type I IFNs in antiviral responses, did not alter survival after infection. This result established that pDCs do not play a major role in the pathogenesis of S. typhimurium colitis. Flow cytometric analysis of macrophages and conventional dendritic cells (cDCs) during active colitis demonstrated an increase in CD11c- macrophages and CD103+ cDCs in the colon of Ifnar1-/- animals. Interestingly, cells expressing the anti-inflammatory cytokine receptor IL-10R are more abundant within these subsets in Ifnar1-/- than in wild-type mice. Moreover, blockade of IL-10R in Ifnar1-/- mice increased their susceptibility to S. typhimurium colitis, suggesting that altered numbers of these immunoregulatory cells may underlie the difference in disease severity. This cross-talk between type I IFN and IL-10R signaling pathways may represent a key host cellular mechanism to investigate further in order to unravel the balance between pathogenic inflammation and homeostasis of the colon. Taken together, our data clearly demonstrate that type I IFN signaling is pathogenic in S. typhimurium colitis.