Torres Lab - Microbiology
Victor J. Torres, Ph.D.
Associate Professor, Department of Microbiology
Microbiology, and Immunology and Inflammation Graduate Training Programs
Joan and Joel Smilow Research Center, 10th Floor
522 First Avenue , New York, NY 10016
Office: (212) 263-9232
Fax: (212) 263-9180
Staphylococcus aureus, MRSA, CA-MRSA, toxin, infection, macrophages, neutrophils, PMN, leukotoxin, gene expression, bacterial pathogenesis, toxin-cell interaction, immune response to infection, regulation of virulence factors, in vivo models of infection, leukocytes, toxin receptors.
Ph.D. in Microbiology and Immunology in 2004,
2005-2008 Vanderbilt University School of Medicine
2008, Assistant professor
2014, Associate professor
RESEARCH INTERESTS:The Torres laboratory is devoted to the study of Staphylococcus aureus (S. aureus), a Gram-positive bacterium that infects more than 1.2 million individuals per year in US hospitals. S. aureus is responsible for a wide spectrum of diseases, ranging from minor skin and soft tissue infections to more invasive and serious infections such as sepsis, pneumonia, osteomyelitis, and endocarditis. The pathogenesis of S. aureus is linked to the production of an arsenal of virulence factors that promote evasion of the host innate and adaptive immune responses. Among these virulence factors, we are interested in those that are secreted to the extracellular milieu. These "exoproteins" have the potential to interact with host cells to alter the host’s response to infection. Specifically, we are currently studying two types of exoproteins, toxins that directly kill mammalian cells (cytotoxins) and proteins that target and alter immune responses without necessarily affecting the viability of the host cell (immunomodulatory exoproteins). The goals of our laboratory are to: (i) define how S. aureus senses signals encountered during infection to regulate the expression and elaboration of virulence factors that are critical to infection, (ii) elucidate the contribution of cytotoxins to S. aureus virulence using diverse models of infection, and (iii) examine the contribution of innate and adaptive immune responses in controlling S. aureus pathobiology. To accomplish these goals, we employ a multidisciplinary approach that combines techniques from bacteriology, genetics, molecular biology, biochemistry, structural biology, cellular biology, and immunology with ex vivo tissue culture models and in vivo murine models of infection. Our ultimate goal is to provide a platform for the rational design of novel drugs that target virulence factors. Such therapeutics are desperately needed to improve our ability to combat S. aureus, one the most significant microbial threats worldwide.
I. Regulation of S. aureus virulence factors. We are investigating the molecular mechanism by which S. aureus differentially regulates the expression of genes that encode for exoproteins. Most of our efforts have been devoted to studying the transcription factor known as Repressor of Toxins (Rot). Rot is a ~16 kDa conserved helix turn helix (HTH)-type transcriptional regulator that is a member of the staphylococcal accessory regulator family (Sar). Rot is responsible for regulating gene expression in a manner that is linked to bacterial density (quorum). In S. aureus, the accessory gene regulator (Agr) is a two-component quorum sensing system (Agr-TCS) that influences the expression of a large number of virulence factors critical for the pathogenesis of S. aureus. Thus, the Agr-TCS is considered a master regulator. Under low bacterial density the Agr-TCS is mainly inactive and Rot is produced resulting in the repression of a collection of target genes including toxin-coding genes. Once S. aureus reaches quorum, the Agr-TCS is activated resulting in the expression of RNAIII, a regulatory RNA that inhibits the translation of rot mRNA, which ultimately results in derepression of Rot-repressed genes. We are studying the molecular means by which Rot influences both the invasive and evasive potential of S. aureus by differentially regulating the expression of genes that code for exoproteins. Surprisingly, our studies have revealed that Rot, in addition to influencing gene expression on its own, can also work together with other transcriptional regulators to amplify its regulatory network resulting in the activation of a select number of virulence factors. Thus, Rot is a dual regulator that can both activate and repress gene expression. The current goals for this project are to:
1. Define the molecular mechanism of Rot-mediated regulation of virulence factors.
2. Elucidate the impact of the cross talk between Rot and additional regulators on the expression of virulence factors.
3. Define the kinetics of Rot-mediated regulation in vivo during different types of infection.
4. Characterize the contribution of Rot-mediated regulation to S. aureus pathogenesis.
II. S. aureus leukotoxins and their contribution to S. aureus pathogenesis.
A hallmark of S. aureus infections is the formation of abscesses, a battleground where S. aureus combats host leukocytes, a critical line of defense against infection. To avoid killing by immune cells, S. aureus elaborates a collection of bi-component, beta-barrel pore-forming toxins which include LukSF-PV,HlgAB, HlgCB, LukED, and LukAB. These toxins are secreted into the extracellular milieu as water-soluble proteins but upon recognition of target host cells, they bind and insert into the plasma membrane forming transmembrane pores. The pores then induce a variety of cellular responses, which can ultimately lead to cell death. The staphylococcal bi-component leukotoxins exhibit a high degree of amino acid similarity, which has given rise to the perception that these are redundant toxins produced by S. aureus. However, we believe that this presumption is incorrect and that each toxin exhibits both conserved as well as unique properties that facilitate S. aureus avoidance of killing by leukocytes. The current goals for this project are to:
1. Identify cellular factors involved in the tropism of leukotoxins towards different type of leukocytes.
2. Exploit structure-function studies to reveal how these toxins transition from water-soluble monomers to membrane embedded oligomeric pores.
3. Determine the molecular mechanism by which these toxins kill mammalian cells.
4. Define the contribution of toxin-mediated leukocyte injury to S. aureus pathogenesis using in vivo models of infection.
5. Elucidate the role of leukocytes and leukocyte receptors in the protection against S. aureus pathogenesis in vivo.
Evolution of hypervirulence by a MRSA clone through acquisition of a transposable element.
Benson MA, Ohneck EA, Ryan C, Alonzo F 3rd, Smith H, Narechania A, Kolokotronis SO, Satola SW, Uhlemann AC, Sebra R, Deikus G, Shopsin B, Planet PJ, Torres VJ.
Mol Microbiol. 2014 Jun 24. doi: 10.1111/mmi.12682.
The bicomponent pore-forming leucocidins of Staphylococcus aureus.
Alonzo F 3rd, Torres VJ.
Microbiol Mol Biol Rev. 2014 Jun;78(2):199-230. doi: 10.1128/MMBR.00055-13.
Identification of a crucial residue required for Staphylococcus aureus LukAB cytotoxicity and receptor recognition.
DuMont AL, Yoong P, Liu X, Day CJ, Chumbler NM, James DB, Alonzo F 3rd, Bode NJ, Lacy DB, Jennings MP, Torres VJ.
Infect Immun. 2014 Mar;82(3):1268-76. doi: 10.1128/IAI.01444-13. Epub 2013 Dec 30.
Cell targeting by the Staphylococcus aureus pore-forming toxins: it's not just about lipids.
DuMont AL, Torres VJ.
Trends Microbiol. 2014 Jan;22(1):21-7. doi: 10.1016/j.tim.2013.10.004. Epub 2013 Nov 11.
Staphylococcus aureus targets the chemokine receptors CXCR1/CXCR2 to kill leukocytes and promote infection.
Reyes-Robles T, Alonzo F 3rd, Kozhaya L, Lacy DB, Unutmaz D, and Torres VJ.
Cell Host & Microbe, 2013 Oct 16;14(4) 453-59
Staphylococcus aureus LukAB cytotoxin kills human neutrophils by targeting the CD11b subunit of the integrin Mac-1.
Dumont AL, Yoong P, Day CJ, Alonzo F 3rd, McDonald WH, Jennings MP, Torres VJ.
Proc Natl Acad Sci U S A. 2013 Jun 10.
Staphylococcus aureus elaborates leukocidin AB to mediate escape from within human neutrophils.
DuMont AL, Yoong P, Surewaard BG, Benson MA, Nijland R, van Strijp JA, Torres VJ.
Infect Immun. 2013 May;81(5):1830-41.
Staphylococcus aureus and CCR5: unveiling commonalities in host-pathogen interactions and potential treatment strategies.
Alonzo F, Torres VJ.
Future Microbiol. 2013 Apr;8(4):425-8.
The effects of Staphylococcus aureus leukotoxins on the host: cell lysis and beyond.
Yoong P, Torres VJ.
Curr Opin Microbiol. 2013 Feb;16(1):63-9.
Bacterial survival amidst an immune onslaught: the contribution of the Staphylococcus aureus leukotoxins.
Alonzo F 3rd, Torres VJ.
PLoS Pathog. 2013 Feb;9(2):e1003143.
A lesson in survival: S. aureus versus the skin.
Alonzo F 3rd, Torres VJ.
Cell Host Microbe.2013 Jan 16;13(1):3-5.
CCR5 is a receptor for Staphylococcus aureus leukotoxin ED.
Alonzo F 3rd, Kozhaya L, Rawlings SA, Reyes-Robles T, DuMont AL, Myszka DG, Landau NR, Unutmaz D, Torres VJ.
Nature. 2013 Jan 3;493(7430):51-5.
Rot and SaeRS cooperate to activate expression of the staphylococcal superantigen-like exoproteins.
Benson MA, Lilo S, Nygaard T, Voyich JM, Torres VJ.
J Bacteriol. 2012 Aug;194(16):4355-65.
Staphylococcus aureus leucocidin ED contributes to systemic infection by targeting neutrophils and promoting bacterial growth in vivo.
Alonzo F 3rd, Benson MA, Chen J, Novick RP, Shopsin B, Torres VJ.
Mol Microbiol. 2012 Jan;83(2):423-35.
Staphylococcus aureus regulates the expression and production of the staphylococcal superantigen-like secreted proteins in a Rot-dependent manner.
Benson MA, Lilo S, Wasserman GA, Thoendel M, Smith A, Horswill AR, Fraser J, Novick RP, Shopsin B, Torres VJ.
Mol Microbiol. 2011 Aug;81(3):659-75.
Characterization of a new cytotoxin that contributes to Staphylococcus aureus pathogenesis.
Dumont AL, Nygaard TK, Watkins RL, Smith A, Kozhaya L, Kreiswirth BN, Shopsin B, Unutmaz D, Voyich JM, Torres VJ.
Mol Microbiol. 2011 Feb;79(3):814-25.
Rita Chan - Research Associate
David BA James - Postdoctoral fellow
Ashira Lubkin - MSTP student
Elizabeth Ohneck - Postdoctoral fellow
Aidan O'Malley - Research Associate
Tamara Reyes-Robles - Graduate student
Pauline Yoong - Postdoctoral fellow
Francis Alonzo III - Ph.D. (Postdoctoral fellow)
Meredith Benson, Ph.D. (Former graduate student)
Ashley Dumont, Ph.D. (Former graduate student)
TORRES LAB NEWS:
April 02, 2013: Meredith and Ashley successfully defended their doctoral thesis!
July 01, 2014: Francis started his independent lab at the Department of Microbiology and Immunology, Loyola University, Chicago