One Sentence Summary: Potent antimicrobial activity of human MAIT cells overcomes carbapenem-resistance in control of Escherichia coli Category of manuscript: Research Article. Abstract word count: 220 References: 69 Display items: 6 figures, 7 supplementary figures, 3 supplementary tables. Word count incl. main text, references, and figure legends: 10041. 3 Abstract Mucosa-associated invariant T (MAIT) cells are abundant antimicrobial T cells in humans, and recognize antigens derived from the microbial riboflavin biosynthetic pathway presented by the MHC-Ib-related protein (MR1). However, the mechanisms responsible for MAIT cell antimicrobial activity are not fully understood, and the efficacy of these mechanisms against antibiotic resistant bacteria has not been explored. Here, we show that MAIT cells mediate MR1restricted antimicrobial activity against E. coli clinical strains in a manner dependent on the activity of cytolytic proteins, but independent of production of pro-inflammatory cytokines or induction of apoptosis in infected cells. The combined action of the pore-forming antimicrobial protein granulysin and the serine protease granzyme B released in response to TCR-mediated recognition of MR1-presented antigen is essential to mediate control against both cell-associated and free-living E. coli. Furthermore, MAIT cell-mediated bacterial control extend to multidrugresistant E. coli primary clinical isolates additionally resistant to carbapenems, a class of last resort antibiotics. Notably, high levels of granulysin and granzyme B in the MAIT cell secretomes directly damage bacterial cells by increasing their permeability, rendering initially resistant E. coli susceptible to the bactericidal activity of carbapenems. These findings define the role of cytolytic effector proteins in MAIT cell-mediated antimicrobial activity, and indicate that granulysin and granzyme B synergize to restore carbapenem bactericidal activity and overcome carbapenem resistance in E. coli. 4 [Main Text: ] Introduction Mucosa-associated invariant T (MAIT) cells are innate-like T cells that are highly abundant in mucosal tissues, the liver, lungs and gastrotintestinal tract, and in peripheral blood [1]. MAIT cells are mostly CD8α + [2, 3], express a semi-invariant T cell receptor (TCR), and recognize antigens in complex with the MHC-Ib-related protein (MR1) [4]. MR1 displays an extraordinary level of evolutionary conservation among placental and marsupial mammals [5], strongly supporting the notion that MR1 and MAIT cells perform critical functions in the immune system. The MR1presented antigens recognized by MAIT cells are derivatives of intermediates in the microbial synthesis of vitamin B 2 (riboflavin) and are produced by many bacteria [6-8]. Riboflavin is a critical component in a wide variety of bacterial cellular processes [9]. MAIT cells are thus able to recognize and respond to a broad set of bacteria [10]. Following TCR-mediated recognition of MR1-presented bacterial riboflavin metabolite antigens, MAIT cells rapidly media...

Vor über hundert Jahren begann Professor Julius Bredt seine Forschungskarriere auf dem Gebiet der verbrückten bicyclischen Systeme, die durch ein Brückenkopf‐Alken unter Ringspannung stehen. Seine kritischen Betrachtungen mündeten in der Formulierung dessen, was wir heute als die Bredtsche Regel kennen. Seitdem versuchen Physikochemiker, Theoretiker und Synthesechemiker gleichermaßen, die Grenzen dieses physikalische Phänomens auszuloten, um es besser kennenzulernen. Der Bauplan der Natur sieht durchaus Brückenkopf‐Doppelbindungen nach der Bredtschen Regel vor. In diesem Aufsatz wird erstmals die Anwendung der Bredtschen Regel auf Naturstoffe umfassend erörtert.

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IFN-gamma, intracellular, lung, human, mouse, riboflavin. 59All rights reserved. No reuse allowed without permission.was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/231472 doi: bioRxiv preprint first posted online Dec. 9, 2017; 4 Mucosal-associated invariant T (MAIT) was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. we had disrupted the MR1 gene using a CRISPR/Cas9 lentiviral system (THP1:MR1-). 125MAIT cells also expressed IFN-g in the presence of MR1-over-expressing cells 126All rights reserved. No reuse allowed without permission.was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/231472 doi: bioRxiv preprint first posted online Dec. 9, 2017; 7 (THP1:MR1+), but expression was minimal using the parental cell line (THP1), which 127 has very low constitutive surface expression of MR1. was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/231472 doi: bioRxiv preprint first posted online Dec. was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/231472 doi: bioRxiv preprint first posted online Dec. 9, 2017; 9 To explore MAIT cell function we investigated the dynamics of their cytokine profile was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/231472 doi: bioRxiv preprint first posted online Dec. 9, 2017; was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. 10 MAIT cell protection against life-threateningThe was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.copyright holder for this preprint (which . http://dx.doi.org/10.1101/231472 doi: bioRxiv preprint first posted online Dec. 9,The copyright holder for this preprint (which . http://dx.doi.org/10.1101/231472 doi: bioRxiv preprint first posted online Dec. 9, 2017; 12 mice, which express the anti-GK1.5 antibody and are CD4+ T cell deficient 24 , and 238 compared these with GK1.5.MR1-/-mice which lack both CD4+ cells and MAIT cells. completely Rag2-/-gC-/-mice from fatal infection with 10 3 CFU L. longbeachae ( Figure 259 All rights reserved. No reuse allowed without permission.was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to...

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