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Proceedings Paper

Photodynamic therapy can induce non-specific protective immunity against a bacterial infection
Author(s): Masamitsu Tanaka; Pawel Mroz; Tianhong Dai; Manabu Kinoshita; Yuji Morimoto; Michael R. Hamblin
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Paper Abstract

Photodynamic therapy (PDT) for cancer is known to induce an immune response against the tumor, in addition to its well-known direct cell-killing and vascular destructive effects. PDT is becoming increasingly used as a therapy for localized infections. However there has not to date been a convincing report of an immune response being generated against a microbial pathogen after PDT in an animal model. We have studied PDT as a therapy for bacterial arthritis caused by Staphylococcus aureus infection in the mouse knee. We had previously found that PDT of an infection caused by injection of MRSA (5X107 CFU) into the mouse knee followed 3 days later by 1 μg of Photofrin and 635- nm diode laser illumination with a range of fluences within 5 minutes, gave a biphasic dose response. The greatest reduction of MRSA CFU was seen with a fluence of 20 J/cm2, whereas lower antibacterial efficacy was observed with fluences that were either lower or higher. We then tested the hypothesis that the host immune response mediated by neutrophils was responsible for most of the beneficial antibacterial effect. We used bioluminescence imaging of luciferase expressing bacteria to follow the progress of the infection in real time. We found similar results using intra-articular methylene blue and red light, and more importantly, that carrying out PDT of the noninfected joint and subsequently injecting bacteria after PDT led to a significant protection from infection. Taken together with substantial data from studies using blocking antibodies we believe that the pre-conditioning PDT regimen recruits and stimulates neutrophils into the infected joint which can then destroy bacteria that are subsequently injected and prevent infection.

Paper Details

Date Published: 9 February 2012
PDF: 9 pages
Proc. SPIE 8224, Biophotonics and Immune Responses VII, 822403 (9 February 2012); doi: 10.1117/12.906012
Show Author Affiliations
Masamitsu Tanaka, Wellman Ctr. for Photomedicine, Massachusetts General Hospital (United States)
Harvard Univ. Medical School (United States)
National Defense Medical College (Japan)
Pawel Mroz, Wellman Ctr. for Photomedicine, Massachusetts General Hospital (United States)
Harvard Univ. Medical School (United States)
Northwestern Memorial Hospital (United States)
Tianhong Dai, Wellman Ctr. for Photomedicine, Massachusetts General Hospital (United States)
Harvard Univ. Medical School (United States)
Manabu Kinoshita, National Defense Medical College (Japan)
Yuji Morimoto, National Defense Medical College (Japan)
Michael R. Hamblin, Wellman Ctr. for Photomedicine, Massachusetts General Hospital (United States)
Harvard Univ. Medical School (United States)
Harvard-MIT Division of Health Sciences and Technology (United States)


Published in SPIE Proceedings Vol. 8224:
Biophotonics and Immune Responses VII
Wei R. Chen, Editor(s)

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