Anti-TACI single and dual-targeting CAR T cells overcome BCMA antigen loss in multiple myeloma

Chimeric Antigen Receptor (CAR) T cells directed to B cell maturation antigen (BCMA) mediate profound responses in patients with multiple myeloma, but most patients do not achieve long-term complete remissions. In addition, recent evidence suggests that high-affinity binding to BCMA can result in on-target, off-tumor activity in the basal ganglia and can lead to fatal Parkinsonian-like disease. Here we develop CAR T cells against multiple myeloma using a binder to targeting transmembrane activator and CAML interactor (TACI) in mono and dual-specific formats with anti-BCMA. These CARs have robust, antigen-specific activity in vitro and in vivo. We also show that TACI RNA expression is limited in the basal ganglia, which may circumvent some of the toxicities recently reported with BCMA CARs. Thus, single-targeting TACI CARs may have a safer toxicity profile, whereas dual-specific BCMA-TACI CAR T cells have potential to avoid the antigen escape that can occur with single-antigen targeting.

Mesenchymal stromal cells expressing a dominant-negative high mobility group A1 transgene exhibit improved function during sepsis

High mobility group (HMG)A proteins are nonhistone chromatin proteins that bind to the minor groove of DNA, interact with transcriptional machinery, and facilitate DNA-directed nuclear processes. HMGA1 has been shown to regulate genes involved with systemic inflammatory processes. We hypothesized that HMGA1 is important in the function of mesenchymal stromal cells (MSCs), which are known to modulate inflammatory responses due to sepsis. To study this process, we harvested MSCs from transgenic (Tg) mice expressing a dominant-negative (dn) form of HMGA1 in mesenchymal cells. MSCs harvested from Tg mice contained the dnHMGA1 transgene, and transgene expression did not change endogenous HMGA1 levels. Immunophenotyping of the cells, along with trilineage differentiation revealed no striking differences between Tg and wild-type (WT) MSCs. However, Tg MSCs growth was decreased compared with WT MSCs, although Tg MSCs were more resistant to oxidative stress-induced death and expressed less IL-6. Tg MSCs administered after the onset of Escherichia coli-induced sepsis maintained their ability to improve survival when given in a single dose, in contrast with WT MSCs. This survival benefit of Tg MSCs was associated with less tissue cell death, and also a reduction in tissue neutrophil infiltration and expression of neutrophil chemokines. Finally, Tg MSCs promoted bacterial clearance and enhanced neutrophil phagocytosis, in part through their increased expression of stromal cell-derived factor-1 compared with WT MSCs. Taken together, these data demonstrate that expression of dnHMGA1 in MSCs provides a functional advantage of the cells when administered during bacterial sepsis.

Reversible ON- and OFF-switch chimeric antigen receptors controlled by lenalidomide

Cell-based therapies are emerging as effective agents against cancer and other diseases. As autonomous "living drugs," these therapies lack precise control. Chimeric antigen receptor (CAR) T cells effectively target hematologic malignancies but can proliferate rapidly and cause toxicity. We developed ON and OFF switches for CAR T cells using the clinically approved drug lenalidomide, which mediates the proteasomal degradation of several target proteins by inducing interactions between the CRL4CRBN E3 ubiquitin ligase and a C2H2 zinc finger degron motif. We performed a systematic screen to identify "super-degron" tags with enhanced sensitivity to lenalidomide-induced degradation and used these degradable tags to generate OFF-switch degradable CARs. To create an ON switch, we engineered a lenalidomide-inducible dimerization system and developed split CARs that required both lenalidomide and target antigen for activation. Subtherapeutic lenalidomide concentrations controlled the effector functions of ON- and OFF-switch CAR T cells. In vivo, ON-switch split CARs demonstrated lenalidomide-dependent antitumor activity, and OFF-switch degradable CARs were depleted by drug treatment to limit inflammatory cytokine production while retaining antitumor efficacy. Together, the data showed that these lenalidomide-gated switches are rapid, reversible, and clinically suitable systems to control transgene function in diverse gene- and cell-based therapies.

A Distinct Transcriptional Program in Human CAR T Cells Bearing the 4-1BB Signaling Domain Revealed by scRNA-Seq

T cells engineered to express chimeric antigen receptors (CARs) targeting CD19 have produced impressive outcomes for the treatment of B cell malignancies, but different products vary in kinetics, persistence, and toxicity profiles based on the co-stimulatory domains included in the CAR. In this study, we performed transcriptional profiling of bulk CAR T cell populations and single cells to characterize the transcriptional states of human T cells transduced with CD3ζ, 4-1BB-CD3ζ (BBζ), or CD28-CD3ζ (28ζ) co-stimulatory domains at rest and after activation by triggering their CAR or their endogenous T cell receptor (TCR). We identified a transcriptional signature common across CARs with the CD3ζ signaling domain, as well as a distinct program associated with the 4-1BB co-stimulatory domain at rest and after activation. CAR T cells bearing BBζ had increased expression of human leukocyte antigen (HLA) class II genes, ENPP2, and interleukin (IL)-21 axis genes, and decreased PD1 compared to 28ζ CAR T cells. Similar to previous studies, we also found BBζ CAR CD8 T cells to be enriched in a central memory cell phenotype and fatty acid metabolism genes. Our data uncovered transcriptional signatures related to costimulatory domains and demonstrated that signaling domains included in CARs uniquely shape the transcriptional programs of T cells.

Chimeric Antigen Receptor T Cells Targeting CD79b Show Efficacy in Lymphoma with or without Cotargeting CD19

PURPOSE

T cells engineered to express a chimeric antigen receptor (CAR) against CD19 have recently been FDA approved for the treatment of relapsed or refractory large B-cell lymphoma. Despite the success and curative potential of CD19 CAR T cells, several reports describing disease relapse due to antigen loss are now emerging.

EXPERIMENTAL DESIGN

We developed a novel CAR construct directed against CD79b, a critical receptor for successful B-cell development that remains highly expressed in several subtypes of B-cell lymphoma, including mantle cell lymphoma (MCL). We tested CAR T cells directed against CD79b alone or in combination with CD19 targeting in a single construct, against cell line- and patient-derived xenograft models.

RESULTS

We demonstrate CAR79b antigen-specific recognition and cytotoxicity against a panel of cell lines and patient-derived xenograft models of MCL. Importantly, we show that downregulation of CD19 does not influence surface expression of CD79b and that anti-CD79b CAR T cells alone or arranged in a dual-targeting format with a CD19 single-chain variable fragment (scFv) are able to recognize and eliminate CD19+, CD19-, and mixed CD19+/CD19-B-cell lymphoma.

CONCLUSIONS

Our findings demonstrate that CAR T cells targeting CD79b alone or in combination have promise for treating and preventing CD19 antigen escape in B-cell lymphomas.

CRISPR-Cas9 disruption of PD-1 enhances activity of universal EGFRvIII CAR T cells in a preclinical model of human glioblastoma

Despite remarkable success in the treatment of hematological malignancies, CAR T-cell therapies for solid tumors have floundered, in large part due to local immune suppression and the effects of prolonged stimulation leading to T-cell dysfunction and exhaustion. One mechanism by which gliomas and other cancers can hamper CAR T cells is through surface expression of inhibitory ligands such as programmed cell death ligand 1 (PD-L1). Using the CRIPSR-Cas9 system, we created universal CAR T cells resistant to PD-1 inhibition through multiplexed gene disruption of endogenous T-cell receptor (TRAC), beta-2 microglobulin (B2M) and PD-1 (PDCD1). Triple gene-edited CAR T cells demonstrated enhanced activity in preclinical glioma models. Prolonged survival in mice bearing intracranial tumors was achieved after intracerebral, but not intravenous administration. CRISPR-Cas9 gene-editing not only provides a potential source of allogeneic, universal donor cells, but also enables simultaneous disruption of checkpoint signaling that otherwise impedes maximal antitumor functionality.

Glycoengineering of chimeric antigen receptor (CAR) T-cells to enforce E-selectin binding

Tissue colonization (homing) by blood-borne cells critically hinges on the ability of the cells to adhere to vascular endothelium with sufficient strength to overcome prevailing hemodynamic shear stress. These adhesive interactions are most effectively engendered via binding of the endothelial lectin E-selectin (CD62E) to its cognate ligand, sialyl Lewis-X (sLe ^X ), displayed on circulating cells. Although chimeric antigen receptor (CAR) T-cell immunotherapy holds promise for treatment of various hematologic and non-hematologic malignancies, there is essentially no information regarding the efficiency of CAR T-cell homing. Accordingly, we performed integrated biochemical studies and adhesion assays to examine the capacity of human CAR T-cells to engage E-selectin. Our data indicate that CAR T-cells do not express sLe ^X and do not bind E-selectin. However, enforced sLe ^X display can be achieved on human CAR T-cells by surface fucosylation, with resultant robust E-selectin binding under hemodynamic shear. Importantly, following intravascular administration into mice, fucosylated human CAR-T cells infiltrate marrow with 10-fold higher efficiency than do unfucosylated cells. Collectively, these findings indicate that custom installation of sLe ^X programs tissue colonization of vascularly administered human CAR T-cells, offering a readily translatable strategy to augment tissue delivery, thereby lowering the pertinent cell dosing and attendant cell production burden, for CAR T-cell immunotherapy applications.

Anti-CD37 chimeric antigen receptor T cells are active against B- and T-cell lymphomas

Chimeric antigen receptor (CAR) T cells have emerged as a novel form of treatment of patients with B-cell malignancies. In particular, anti-CD19 CAR T-cell therapy has effected impressive clinical responses in B-cell acute lymphoblastic leukemia and diffuse large B-cell lymphoma. However, not all patients respond, and relapse with antigen loss has been observed in all patient subsets. Here, we report on the design and optimization of a novel CAR directed to the surface antigen CD37, which is expressed in B-cell non-Hodgkin lymphomas, in chronic lymphocytic leukemia, and in some cases of cutaneous and peripheral T-cell lymphomas. We found that CAR-37 T cells demonstrated antigen-specific activation, cytokine production, and cytotoxic activity in models of B- and T-cell lymphomas in vitro and in vivo, including patient-derived xenografts. Taken together, these results are the first showing that T cells expressing anti-CD37 CAR have substantial activity against 2 different lymphoid lineages, without evidence of significant T-cell fratricide. Furthermore, anti-CD37 CARs were readily combined with anti-CD19 CARs to generate dual-specific CAR T cells capable of recognizing CD19 and CD37 alone or in combination. Our findings indicate that CD37-CAR T cells represent a novel therapeutic agent for the treatment of patients with CD37-expressing lymphoid malignancies.

Frontline Science: Targeted expression of a dominant-negative high mobility group A1 transgene improves outcome in sepsis

High mobility group (HMG) proteins are a family of architectural transcription factors, with HMGA1 playing a role in the regulation of genes involved in promoting systemic inflammatory responses. We speculated that blocking HMGA1-mediated pathways might improve outcomes from sepsis. To investigate HMGA1 further, we developed genetically modified mice expressing a dominant negative (dn) form of HMGA1 targeted to the vasculature. In dnHMGA1 transgenic (Tg) mice, endogenous HMGA1 is present, but its function is decreased due to the mutant transgene. These mice allowed us to specifically study the importance of HMGA1 not only during a purely pro-inflammatory insult of endotoxemia, but also during microbial sepsis induced by implantation of a bacterial-laden fibrin clot into the peritoneum. We found that the dnHMGA1 transgene was only present in Tg and not wild-type (WT) littermate mice, and the mutant transgene was able to interact with transcription factors (such as NF-κB), but was not able to bind DNA. Tg mice exhibited a blunted hypotensive response to endotoxemia, and less mortality in microbial sepsis. Moreover, Tg mice had a reduced inflammatory response during sepsis, with decreased macrophage and neutrophil infiltration into tissues, which was associated with reduced expression of monocyte chemotactic protein-1 and macrophage inflammatory protein-2. Collectively, these data suggest that targeted expression of a dnHMGA1 transgene is able to improve outcomes in models of endotoxin exposure and microbial sepsis, in part by modulating the immune response and suggest a novel modifiable pathway to target therapeutics in sepsis.

CpG oligodeoxynucleotide as immune adjuvant enhances photodynamic therapy response in murine metastatic breast cancer

Breast cancer is the most common cause of cancer death in women. The side effects and complications following current breast cancer therapy can be devastating. Moreover, the prognosis in late stages of the diseases is usually poor. Photodynamic therapy (PDT) is a promising cancer treatment modality that is capable of both local tumor destruction and immune stimulation. However, treatment with PDT alone is often non-curative due to tumor-induced immune cell dysfunction and immune suppression. This phenomenon has motivated a new approach by combining immunostimulants with PDT to enhance anti-tumor immunity. In the present study, we investigated PDT mediated by verteporfin and 690 nm light delivered 15 min later, in combination with an immunomodulation approach using CpG oligodeoxynucleotide for the treatment of 4T1 metastatic breast cancer in a BALB/c immunocompetent mouse model. In vitro, CpG primed immature dendritic cells (DC) via toll like receptor 9 to phagocytose PDT killed tumor cells leading to DC maturation and activation. Peritumoral injection of CpG after PDT in mice gave improved local tumor control and a survival advantage compared to either treatment alone (p < 0.05). CpG may be a valuable dendritic cell targeted immunoadjuvant to combine with PDT.

Mechanisms in photodynamic therapy: part two-cellular signaling, cell metabolism and modes of cell death

Photodynamic therapy (PDT) has been known for over a hundred years, but is only now becoming widely used. Originally developed as a tumor therapy, some of its most successful applications are for non-malignant disease. In the second of a series of three reviews, we will discuss the mechanisms that operate in PDT on a cellular level. In Part I [Castano AP, Demidova TN, Hamblin MR. Mechanism in photodynamic therapy: part one-photosensitizers, photochemistry and cellular localization. Photodiagn Photodyn Ther 2004;1:279-93] it was shown that one of the most important factors governing the outcome of PDT, is how the photosensitizer (PS) interacts with cells in the target tissue or tumor, and the key aspect of this interaction is the subcellular localization of the PS. PS can localize in mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus and plasma membranes. An explosion of investigation and explorations in the field of cell biology have elucidated many of the pathways that mammalian cells undergo when PS are delivered in tissue culture and subsequently illuminated. There is an acute stress response leading to changes in calcium and lipid metabolism and production of cytokines and stress proteins. Enzymes particularly, protein kinases, are activated and transcription factors are expressed. Many of the cellular responses are centered on mitochondria. These effects frequently lead to induction of apoptosis either by the mitochondrial pathway involving caspases and release of cytochrome c, or by pathways involving ceramide or death receptors. However, under certain circumstances cells subjected to PDT die by necrosis. Although there have been many reports of DNA damage caused by PDT, this is not thought to be an important cell-death pathway. This mechanistic research is expected to lead to optimization of PDT as a tumor treatment, and to rational selection of combination therapies that include PDT as a component.

Mechanisms in photodynamic therapy: part one-photosensitizers, photochemistry and cellular localization

The use of non-toxic dyes or photosensitizers (PS) in combination with harmless visible light that is known as photodynamic therapy (PDT) has been known for over a hundred years, but is only now becoming widely used. Originally developed as a tumor therapy, some of its most successful applications are for non-malignant disease. In a series of three reviews we will discuss the mechanisms that operate in the field of PDT. Part one discusses the recent explosion in discovery and chemical synthesis of new PS. Some guidelines on how to choose an ideal PS for a particular application are presented. The photochemistry and photophysics of PS and the two pathways known as Type I (radicals and reactive oxygen species) and Type II (singlet oxygen) photochemical processes are discussed. To carry out PDT effectively in vivo, it is necessary to ensure sufficient light reaches all the diseased tissue. This involves understanding how light travels within various tissues and the relative effects of absorption and scattering. The fact that most of the PS are also fluorescent allows various optical imaging and monitoring strategies to be combined with PDT. The most important factor governing the outcome of PDT is how the PS interacts with cells in the target tissue or tumor, and the key aspect of this interaction is the subcellular localization of the PS. Examples of PS that localize in mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus and plasma membranes are given. Finally the use of 5-aminolevulinic acid as a natural precursor of the heme biosynthetic pathway, stimulates accumulation of the PS protoporphyrin IX is described.

MicroRNA-21 promotes fibrosis of the kidney by silencing metabolic pathways

Scarring of the kidney is a major public health concern, directly promoting loss of kidney function. To understand the role of microRNA (miRNA) in the progression of kidney scarring in response to injury, we investigated changes in miRNA expression in two kidney fibrosis models and identified 24 commonly up-regulated miRNAs. Among them, miR-21 was highly elevated in both animal models and in human transplanted kidneys with nephropathy. Deletion of miR-21 in mice resulted in no overt abnormality. However, miR-21(-/-) mice suffered far less interstitial fibrosis in response to kidney injury, a phenotype duplicated in wild-type mice treated with anti-miR-21 oligonucleotides. Global derepression of miR-21 target mRNAs was readily detectable in miR-21(-/-) kidneys after injury. Analysis of gene expression profiles up-regulated in the absence of miR-21 identified groups of genes involved in metabolic pathways, including the lipid metabolism pathway regulated by peroxisome proliferator-activated receptor-α (Pparα), a direct miR-21 target. Overexpression of Pparα prevented ureteral obstruction-induced injury and fibrosis. Pparα deficiency abrogated the antifibrotic effect of anti-miR-21 oligonucleotides. miR-21 also regulated the redox metabolic pathway. The mitochondrial inhibitor of reactive oxygen species generation Mpv17l was repressed by miR-21, correlating closely with enhanced oxidative kidney damage. These studies demonstrate that miR-21 contributes to fibrogenesis and epithelial injury in the kidney in two mouse models and is a candidate target for antifibrotic therapies.

The melanoma-associated transmembrane glycoprotein Gpnmb controls trafficking of cellular debris for degradation and is essential for tissue repair

Kidney damage due to injury rarely resolves completely, and there are currently no therapies capable of promoting repair. In addition to understanding mechanisms by which tissues are damaged, illuminating mechanisms of repair and regeneration is also of great importance. Here we show that the melanoma-associated, transmembrane glycoprotein, Gpnmb, is up-regulated 15-fold following ischemic damage in kidney tissue and by more than 10-fold in macrophages and 3-fold in surviving epithelial cells. Gpnmb-expressing macrophages and epithelial cells were found to contain apoptotic bodies at 3 times the rate of nonexpressing cells. Either mutation of Gpnmb or ablation of inflammatory macrophages prevents normal repair of the kidney. Significantly, the kidneys from postischemic Gpnmb mutant mice exhibited a 5-fold increase in apoptotic cellular debris compared to wild-type mice. These mice also experienced an 85% increase in mortality following bilateral ischemic kidney. Finally, we demonstrate that Gpnmb is a phagocytic protein that is necessary for recruitment of the autophagy protein LC3 to the phagosome where these proteins are colocalized and for lysosomal fusion with the phagosome and hence bulk degradation of their content. Therefore, Gpnmb is a novel prorepair gene that is necessary for crosstalk between the macroautophagic degradation pathway and phagocytosis.

Effect of chitosan acetate bandage on wound healing in infected and noninfected wounds in mice

HemCon bandage is an engineered chitosan acetate preparation designed as a hemostatic dressing, and is under investigation as a topical antimicrobial dressing. We studied its effects on healing of excisional wounds that were or were not infected with Staphylococcus aureus, in normal mice or mice previously pretreated with cyclophosphamide (CY). CY significantly suppressed wound healing in both the early and later stages, while S. aureus alone significantly stimulated wound healing in the early stages by preventing the initial wound expansion. CY plus S. aureus showed an advantage in early stages by preventing expansion, but a significant slowing of wound healing in later stages. In order to study the conflicting clamping and stimulating effects of chitosan acetate bandage on normal wounds, we removed the bandage from wounds at times after application ranging from 1 hour to 9 days. Three days application gave the earliest wound closure, and all application times gave a faster healing slope after removal compared with control wounds. Chitosan acetate bandage reduced the number of inflammatory cells in the wound at days 2 and 4, and had an overall beneficial effect on wound healing especially during the early period where its antimicrobial effect is most important.

Intravascular detection of inflamed atherosclerotic plaques using a fluorescent photosensitizer targeted to the scavenger receptor

Inflammation plays an important role in the pathophysiology of atherosclerotic disease. We have previously shown that the targeted photosensitizer chlorin (e(6)) conjugated with maleylated albumin (MA-ce6) is taken up by macrophages via the scavenger receptor with high selectivity. In a rabbit model of inflamed plaque in New Zealand white rabbits via balloon injury of the aorto-iliac arteries and high cholesterol diet we showed that the targeted conjugate showed specificity towards plaques compared to free ce6. We now show that an intravascular fiber-based spectrofluorimeter advanced along the -iliac vessel through blood detects 24-fold higher fluorescence in atherosclerotic vessels compared to control rabbits (p < 0.001 ANOVA). Within the same animals, signal derived from the injured iliac artery was 16-fold higher than the contralateral uninjured iliac (p < 0.001). Arteries were removed and selective accumulation of MA-ce6 in plaques was confirmed using: (1) surface spectrofluorimetry, (2) fluorescence extraction of ce6 from aortic segments, and (3) confocal microscopy. Immunohistochemical analysis of the specimens showed a significant correlation between MA-ce6 uptake and RAM-11 macrophage staining (R = 0.83, p < 0.001) and an inverse correlation between MA-ce6 uptake and smooth muscle cell staining (R = -0.74, p < 0.001). MA-ce6 may function as a molecular imaging agent to detect and/or photodynamically treat inflamed plaques.

Low-level laser therapy for zymosan-induced arthritis in rats: Importance of illumination time

BACKGROUND

It has been proposed for many years that low-level laser (or light) therapy (LLLT) can ameliorate the pain, swelling, and inflammation associated with various forms of arthritis. Light is thought to be absorbed by mitochondrial chromophores leading to an increase in adenosine triphosphate (ATP), reactive oxygen species and/or cyclic AMP production and consequent gene transcription via activation of transcription factors. However, despite many reports about the positive effects of LLLT in arthritis and in medicine in general, its use remains controversial. For all indications (including arthritis) the optimum optical parameters have been difficult to establish and so far are unknown.

METHODS

We tested LLLT on rats that had zymosan injected into their knee joints to induce inflammatory arthritis. We compared illumination regimens consisting of a high and low fluence (3 and 30 J/cm(2)), delivered at high and low irradiance (5 and 50 mW/cm(2)) using 810-nm laser light daily for 5 days, with the positive control of conventional corticosteroid (dexamethasone) therapy.

RESULTS

Illumination with 810-nm laser was highly effective (almost as good as dexamethasone) at reducing swelling and a longer illumination time (10 or 100 minutes compared to 1 minute) was more important in determining effectiveness than either the total fluence delivered or the irradiance. LLLT induced reduction of joint swelling correlated with reduction in the inflammatory marker serum prostaglandin E2 (PGE2).

CONCLUSION

LLLT with 810-nm laser is highly effective in treating inflammatory arthritis in this model. Longer illumination times were more effective than short times regardless of total fluence or irradiance. These data will be of value in designing clinical trials of LLLT for various arthritides.

Macrophage-targeted photosensitizer conjugate delivered by intratumoral injection

A conjugate between maleylated albumin and a photosensitizer (PS) shows cell type specific targeting to macrophages via the scavenger receptor. Administration of this conjugate to a tumor-bearing mouse followed by illumination may allow selective destruction of macrophages within tumors. There is accumulating evidence that tumor-associated macrophages contribute to tumor growth, invasiveness, metastasis, and immune suppression. We tested the intravenous (IV) injection of a conjugate between maleylated albumin and chlorin(e6) to BALB/c mice bearing three tumor types with differing proportions of tumor-associated macrophages. The accumulation of PS within the tumors after IV injection and 24 h incubation time was disappointing, and we therefore investigated intratumoral (IT) injection. This gave 20-50 times greater concentrations of PS within the tumor compared to IV injection as determined by tissue extraction. Furthermore the amounts of PS in each tumor type correlated well with the numbers of macrophages both as determined by extraction from bulk tumor and fluorescence quantification and as determined by tissue dissociation to a single cell suspension and two-color flow cytometry with macrophage-specific antibodies. IT injection of nonconjugated PS gave lower tumor accumulation that did not correlate with macrophage content. IT injection of targeted macromolecular delivery systems is an underexplored area and worthy of further study.

Photodynamic therapy and anti-tumour immunity

Photodynamic therapy (PDT) uses non-toxic photosensitizers and harmless visible light in combination with oxygen to produce cytotoxic reactive oxygen species that kill malignant cells by apoptosis and/or necrosis, shut down the tumour microvasculature and stimulate the host immune system. In contrast to surgery, radiotherapy and chemotherapy that are mostly immunosuppressive, PDT causes acute inflammation, expression of heat-shock proteins, invasion and infiltration of the tumour by leukocytes, and might increase the presentation of tumour-derived antigens to T cells.

Use of chitosan bandage to prevent fatal infections developing from highly contaminated wounds in mice

HemCon bandage is an engineered chitosan acetate preparation used as a hemostatic control dressing, and its chemical structure suggests that it should also be antimicrobial. We tested its ability to rapidly kill bacteria in vitro and in mouse models of infected wounds. We used the Gram-negative species Pseudomonas aeruginosa and Proteus mirabilis and the Gram-positive Staphylococcus aureus that had all been stably transduced with the entire bacterial lux operon to allow in vivo bioluminescence imaging. An excisional wound in Balb/c mice was inoculated with 50-250 million cells followed after 30 min by application of HemCon bandage, alginate sponge bandage, silver sulfadiazine cream or no treatment. HemCon was more adhesive to the wound and conformed well to the injury compared to alginate. Animal survival was followed over 15 days with observations of bioluminescence emission and animal activity daily. Chitosan acetate treated mice infected with P. aeruginosa and P. mirabilis all survived while those receiving no treatment, alginate and silver sulfadiazine demonstrated 25-100% mortality. Chitosan acetate was much more effective than other treatments in rapidly reducing bioluminescence in the wound consistent with its rapid bactericidal activity in vitro as well as its light-scattering properties. S. aureus formed only non-lethal localized infections after temporary immunosuppression of the mice but HemCon was again more effective in reducing bioluminescence. The data suggest that chitosan acetate rapidly kills bacteria in the wound before systemic invasion can take place, and is superior to alginate bandage and silver sulfadiazine that may both encourage bacterial growth in the short term.

A green fluorescent protein-expressing murine tumour but not its wild-type counterpart is cured by photodynamic therapy

The ideal cancer treatment should both destroy the primary tumour and at the same time educate the immune system to recognise the tumour as foreign so that distant metastases will also be eradicated. Photodynamic therapy (PDT) involves the i.v. administration of photosensitisers followed by illumination of the tumour with red light producing reactive oxygen species that eventually cause vascular shutdown and tumour cell death by apoptosis and necrosis. Anti-tumour immunity is stimulated after PDT due to the acute inflammatory response, generation of tumour-specific antigens, and induction of heat-shock proteins. Green fluorescent protein (GFP) is used as an optical reporter to noninvasively image the progression of mouse tumours, and in addition, may act as a foreign (jellyfish) antigen. We asked whether GFP-expressing tumours could be used to monitor the response of tumour-bearing mice to PDT, and whether the tumour response differed when a nonimmunogenic tumour cell line was transduced with GFP. We injected RIF-1 or RIF-1 EGFP (stably transduced with a retroviral vector) cells in the leg of C3H/HeN mice and both the cells and tumour grew equally well. We used PDT with benzoporphyrin derivative and a short drug-light interval. There were complete cures and 100% mouse survival of RIF-1 EGFP while RIF-1 wild-type tumours all recurred. Cured mice were resistant to rechallenge with RIF-1 EGFP cells and a rechallenge with wild-type RIF-1 cells grew significantly slower. There was also slower RIF-1 EGFP rechallenge growth but no rejection when RIF-1 EGFP tumours were surgically removed. There was a low rate of PDT cure of tumours when RIF-1 cells were transduced with an empty retroviral vector. The presence of antibodies against EGFP in mouse serum suggests EGFP can act as a foreign antigen and PDT can then stimulate a long-term memory immune response.

Photosensitizer delivery to vulnerable atherosclerotic plaque: comparison of macrophage-targeted conjugate versus free chlorin(e6)

We have previously shown that a conjugate (MA-ce6) between maleylated serum albumin and the photosensitizer chlorin(e6) (ce6) is targeted in vitro to macrophages via class A scavenger receptors. We now report on the ability of this conjugate to localize in macrophage-rich atherosclerotic plaques in vivo. Both the conjugate and the free photosensitizer ce6 are studied after injection into New Zealand White rabbits that are rendered atherosclerotic by a combination of aortic endothelial injury and cholesterol feeding into normal rabbits. Rabbits are sacrificed at 6 and 24 h after injection and intravascular fluorescence spectroscopy is carried out by fiber-based fluorimetry in intact blood-filled arteries. Surface spectrofluorimetry of numbered excised aortic segments together with injured and normal iliac arteries is carried out, and quantified ce6 content by subsequent extraction and quantitative fluorescence determination of the arterial segments and also of nontarget organs. There is good agreement between the various techniques for quantifying ce6 localization, and high contrast between arteries from atherosclerotic and normal rabbits is obtained. Fluorescence correlates with the highest burden of plaque in the aorta and the injured iliac artery. The highest accumulation in plaques is obtained using MA-ce6 at 24 h. Free ce6 gives better accumulation at 6 h compared to 24 h. The liver, spleen, lung, and gall bladder have the highest uptake in nontarget organs. Macrophage-targeted photosensitizer conjugates may have applications in both detecting and treating inflamed vulnerable plaque.

Mechanisms in photodynamic therapy: Part three-Photosensitizer pharmacokinetics, biodistribution, tumor localization and modes of tumor destruction

Photodynamic therapy (PDT) has been known for over a hundred years, but is only now becoming widely used. Originally developed as cancer therapy, some of its most successful applications are for non-malignant disease. The majority of mechanistic research into PDT, however, is still directed towards anti-cancer applications. In the final part of series of three reviews, we will cover the possible reasons for the well-known tumor localizing properties of photosensitizers (PS). When PS are injected into the bloodstream they bind to various serum proteins and this can affect their phamacokinetics and biodistribution. Different PS can have very different pharmacokinetics and this can directly affect the illumination parameters. Intravenously injected PS undergo a transition from being bound to serum proteins, then bound to endothelial cells, then bound to the adventitia of the vessels, then bound either to the extracellular matrix or to the cells within the tumor, and finally to being cleared from the tumor by lymphatics or blood vessels, and excreted either by the kidneys or the liver. The effect of PDT on the tumor largely depends at which stage of this continuous process light is delivered. The anti-tumor effects of PDT are divided into three main mechanisms. Powerful anti-vascular effects can lead to thrombosis and hemorrhage in tumor blood vessels that subsequently lead to tumor death via deprivation of oxygen and nutrients. Direct tumor cell death by apoptosis or necrosis can occur if the PS has been allowed to be taken up by tumor cells. Finally the acute inflammation and release of cytokines and stress response proteins induced in the tumor by PDT can lead to an influx of leukocytes that can both contribute to tumor destruction as well as to stimulate the immune system to recognize and destroy tumor cells even at distant locations.