Staphylococcus aureus is a major public health concern and is responsible for over 300,000 hospitalizations in the United States each year (1-2). The organism is a leading cause of suppurative skin lesions, bacterial endocarditis, bacteremia, and pneumonia. Treatment of S. aureus infection is complicated by the emergence of numerous antibiotic resistant strains (2). Once previously limited to hospital settings, community acquired infections due to S. aureus continue to arise, often in otherwise healthy individuals (2). S. aureus secretes an arsenal of virulence factors that promote the organism's survival in susceptible hosts. Among these factors are a number of secreted toxins that directly interact with and kill/damage host cells (3-5). The coordinated regulation of toxin expression is critical to S. aureus pathogenesis. Our data demonstrate that regulation of toxin production by transcriptional repression is critical to optimal expression of the leukotoxin LukED. When such regulatory patterns are perturbed, S. aureus strains become hypervirulent in mouse models of infection due to increased LukED production. Experiments described in this application are designed to (i) elucidate the regulatory mechanism(s) of lukED gene expression in S. aureus and (ii) determine the functional impact of LukED intoxication in vitro, ex vivo, and in vivo. Bacterial genetics, promoter binding assays, in vitro cell toxicity and survival assays, in vivo models of septicemic infection, and immunological techniques will be critical to the execution of the above aims. Experiments will investigate the impact of coordinated lukED gene expression in vivo, the role of the toxin in bacterial mediated mammalian cell killing, and the toxin's effecton immune cell recruitment/viability in vivo. Ultimately, we will determine the major contributions of LukED to pathogenesis in vivo and will provide insight into the optimal toxin expression patterns required for infection. Importantly, this work will further the mission of the National Institutes f Health by examining the mechanistic underpinnings of disease caused by S. aureus, with an end goal of improving prevention and treatment strategies.

Public Health Relevance

Staphylococcus aureus infections continue to be a major public health concern in the United States where they result in over 300,000 hospitalizations yearly. More than 1.3 million people are affected by S. aureus-related infections in any given year, further highlighting the need to investigate the underlying mechanisms that allow this organism to cause disease. This application will investigate the regulation and activity of an important toxin that promotes disease in S. aureus;such studies have the potential to determine the mechanism of action of a novel target for inhibitory drug design and vaccine therapy.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Postdoctoral Individual National Research Service Award (F32)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-F13-C (20))
Program Officer
Huntley, Clayton C
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
New York University
Schools of Medicine
New York
United States
Zip Code
DuMont, Ashley L; Yoong, Pauline; Liu, Xiang et al. (2014) Identification of a crucial residue required for Staphylococcus aureus LukAB cytotoxicity and receptor recognition. Infect Immun 82:1268-76
Alonzo 3rd, Francis; Torres, Victor J (2014) The bicomponent pore-forming leucocidins of Staphylococcus aureus. Microbiol Mol Biol Rev 78:199-230
Benson, Meredith A; Ohneck, Elizabeth A; Ryan, Chanelle et al. (2014) Evolution of hypervirulence by a MRSA clone through acquisition of a transposable element. Mol Microbiol 93:664-81
Alonzo 3rd, Francis; Torres, Victor J (2013) Bacterial survival amidst an immune onslaught: the contribution of the Staphylococcus aureus leukotoxins. PLoS Pathog 9:e1003143
Alonzo, Francis; Torres, Victor J (2013) Staphylococcus aureus and CCR5: unveiling commonalities in host-pathogen interactions and potential treatment strategies. Future Microbiol 8:425-8
DuMont, Ashley L; Yoong, Pauline; Day, Christopher J et al. (2013) Staphylococcus aureus LukAB cytotoxin kills human neutrophils by targeting the CD11b subunit of the integrin Mac-1. Proc Natl Acad Sci U S A 110:10794-9
Reyes-Robles, Tamara; Alonzo 3rd, Francis; Kozhaya, Lina et al. (2013) Staphylococcus aureus leukotoxin ED targets the chemokine receptors CXCR1 and CXCR2 to kill leukocytes and promote infection. Cell Host Microbe 14:453-9