Showing papers by "Otto C. Boerman published in 2001"

Imaging infection/inflammation in the new millennium

Abstract: In the closing half of the past century a wide variety of approaches were developed to visualise infection and inflammation by gamma scintigraphy. Use of autologous leucocytes, labelled with indium-111 or technetium-99m, is still considered the "gold standard" nuclear medicine technique for the imaging of infection and inflammation. However, the range of radiopharmaceuticals used to investigate infectious and non-microbial inflammatory disorders is expanding rapidly. Developments in protein/peptide chemistry and in radiochemistry should lead to agents with very high specific activities. Recently, positron emission tomography with fluorine-18 fluorodeoxyglucose has been shown to delineate infectious and inflammatory foci with high sensitivity. The third millennium will witness a gradual shift from basic (non-specific) or cumbersome, even hazardous techniques (radiolabelled leucocytes) to more sophisticated approaches. Here a survey is presented of the different approaches in use or under investigation.

In vivo applications of PEG liposomes: unexpected observations.

Abstract: Recent studies with PEG liposomes in patients have consistently shown that liposomes can induce side effects (flushing, tightness of the chest). Furthermore, the blood clearance of PEG liposomes was shown to be dose-dependent: at lipid doses lower than 1 micromol/kg, PEG liposomes do not show the long-circulation property but instead are cleared relatively rapidly from the bloodstream. Another remarkable observation was that repeated injections of PEG liposomes led to significant pharmacokinetic changes: the circulatory half-life of a second dose of radiolabeled PEG liposomes dramatically decreased when given from 5 days to up to 4 weeks after a first injection. In these three unexpected phenomena, proteins of the complement system seem to play a key role. Therefore, one has to consider that PEG liposomes are not inert drug-carrying vehicles in vivo. Pharmacological effects can occur, induced solely by using liposomal particles irrespective of the drug content.

Rapid imaging of experimental colitis with (99m)Tc-interleukin-8 in rabbits.

Abstract: UNLABELLED Radiolabeled autologous leukocytes (WBCs) are the gold standard for imaging inflammatory bowel disease (IBD). For the rapid and adequate management of patients with IBD, there is need for a new agent at least as good as radiolabeled WBCs, but easier to prepare and without its inherent risks. In this study, the potential of interleukin-8 (IL-8) labeled with (99m)Tc using hydrazinonicotinamide (HYNIC) to image IBD was investigated in a rabbit model of acute colitis and compared with that of (99m)Tc-HMPAO-labeled granulocytes. METHODS In rabbits with chemically induced acute colitis, inflammatory lesions were scintigraphically visualized after injection of either IL-8 or purified granulocytes, both labeled with (99m)Tc. Gamma camera images were acquired at 2 min and at 1, 2, and 4 h after injection. Four hours after injection, the rabbits were killed, and the uptake of the radiolabel in the dissected tissues was determined. The dissected colon was imaged and the inflammatory lesions were scored macroscopically. For each affected colon segment, the colitis index (affected colon-to-normal colon uptake ratio, CI) was calculated and correlated with the macroscopically scored severity of inflammation. RESULTS Both agents visualized the colitis within 1 h after injection. (99m)Tc-HYNIC-IL-8 images of the colonic abnormalities were more accurate and the intensity of uptake in the affected colon continuously increased until 4 h after injection, whereas no further increase 1 h after injection was noticed scintigraphically for (99m)Tc-HMPAO-granulocytes. The absolute uptake in the affected colon was much higher for IL-8 than for the radiolabeled granulocytes with the percentage injected dose per gram (%ID/g) 0.41 +/- 0.04 %ID/g and 0.09 +/- 0.05 4 %ID/g h after injection, respectively. With increasing severity, the CI at 4 h after injection for (99m)Tc-HYNIC-IL-8 was 4.4 +/- 0.6, 13.5 +/- 0.5, and 25.8 +/- 1.0; for granulocytes, the CI at 4 h after injection was 1.5 +/- 0.1, 3.4 +/- 0.2, and 6.4 +/- 0.5, respectively. The CI correlated with the severity of the inflammation (r = 0.95, P < 0.0001 for IL-8; r = 0.95, P < 0.0001 for granulocytes). CONCLUSION Within 1 h after injection, visualization of the extent of colonic inflammation in vivo was possible with (99m)Tc-HYNIC-IL-8 and (99m)Tc-HMPAO-granulocytes. Within 2 h after injection, (99m)Tc-IL-8 allowed a good evaluation, and within 4 h after injection, a meticulous evaluation of the severity of IBD. Although (99m)Tc-HMPAO-granulocytes were able to delineate the extent of IBD within 2 h after injection, an accurate estimation of severity of inflammation was not possible. (99m)Tc-HYNIC-IL-8 is an inflammation-imaging agent that showed promising results in this study. (99m)Tc-IL-8 can be prepared off-the-shelf and yields excellent imaging with high target-to-background ratios.

(99m)Tc-interleukin-8 for imaging acute osteomyelitis.

Abstract: Early and accurate diagnosis of osteomyelitis remains a clinical problem. Acute osteomyelitis often occurs in infants and most often is located in the long bones. Radiologic images show changes only in advanced stages of disease. Scintigraphic imaging with 99mTc-methylene diphosphonate (MDP), or bone scanning, is much more sensitive in detecting acute osteomyelitis but lacks specificity. We evaluated the performance of 99mTc-interleukin-8 (IL-8) in an experimental model of acute osteomyelitis. Methods: Acute pyogenic osteomyelitis was induced in 10 rabbits by inserting sodium morrhuate and Staphylococcus aureus into the medullary cavity of the right femur. The cavity was closed with liquid cement. A sham operation was performed on the left femur. Routine radiographs were obtained just before scintigraphy. Ten days after surgery, the rabbits were divided into 2 groups of 5 animals, received an injection of either 18.5 MBq 111In-granulocytes or 18.5 MBq 67Ga-citrate, and were imaged both 24 h after injection and 48 h after injection. On day 12, the rabbits received either 18.5 MBq 99mTc-MDP or 18.5 MBq 99mTc-IL-8, and serial images were acquired at 0, 1, 2, 4, 8, 12, and 24 h after injection. Uptake in the infected femur was determined by drawing regions of interest. Ratios of infected femur (target) to sham-operated femur (background) (T/Bs) were calculated. After the final images were obtained, the rabbits were killed and the right femur was dissected and analyzed for microbiologic and histopathologic evidence of osteomyelitis. Results: Acute osteomyelitis developed in 8 of 10 rabbits. All imaging agents correctly detected the acute osteomyelitis in these animals. The extent of infection was optimally visualized with 67Ga-citrate and delayed bone scanning, whereas diaphyseal photopenia was noted with both 99mTc-IL-8 and 111In-granulocytes. In 1 rabbit with osteomyelitis, imaging results were falsely negative with 111In-granulocytes and falsely positive with 99mTc-MDP. Quantitative analysis of the images revealed that the uptake in the infected region was highest with 67Ga-citrate (4.9 ± 0.8 percentage injected dose [%ID]) and 99mTc-MDP (4.7 ± 0.7 %ID), whereas the uptake in the infected area was significantly lower with 99mTc-IL-8 (2.2 ± 0.2 %ID) and 111In-granulocytes (0.8 ± 0.2 %ID) (P

Radioimmunotherapy of B-cell non-Hodgkin's lymphoma.

Abstract: In the past decade, several new antibody-based therapies – using either radiolabelled or unlabelled monoclonal antibodies – have become available for the treatment of patients with refractory or recurrent non-Hodgkin's lymphoma (NHL). Unlabelled monoclonal antibodies (mAbs) kill lymphoma cells by activating host immune effector mechanisms, or by inducing apoptosis. These mAbs can also be used to guide radionuclides to the lymphoma. This radioimmunotherapy (RIT) has been studied with various nuclides (131I, 90Y, 67Cu and 186Re) and with various mAbs. In this review the radionuclides, methods of dosing and recent RIT studies in patients with B-cell NHL are reviewed. Most of these studies demonstrate that RIT is an effective new treatment modality for NHL.

(99m)Tc-E-selectin binding peptide for imaging acute osteomyelitis in a novel rat model.

Abstract: Introduction In the present study, 99m Tc-radiolabelled E-selectin binding peptide ( 99m Tc-IMP-178) was investigated for its potential to image acutem pyogenic osteomyelitis in a new animal model. Intraindividual comparisons were performed using an irrelevant peptide ( 99m Tc-IMP-100) to demonstrate specificity. Methods An acute pyogenic osteomyelitis was induced by injecting 0.05 ml of 5% sodium morrhuate and 5 x 10 8 CFU of Staphylococcus aureus into the medullary cavity of the right tibia in 16 rats. Sixteen additional rats served as untreated controls. Whole-body imaging of pyogenic (n = 4) and untreated (n = 4) animals was performed continously during the first 8 h (12 MBq i.v. of 99m Tc-IMP-178 and 99m Tc-IMP-100 for control), and one further single image was acquired after 16 h p.i. Tissue biodistribution studies were performed in 12 rats with an acute pyogenic osteomyelitis and in 12 untreated rats 1, 4 and 24 h after injection. Data of the histological/radiological and haematological investigations were obtained in all animals. Results Histopathologically, 15 of 16 treated rats (93%) developed an acute pyogenic osteomyelitis showing a major infiltration of the bone marrow by polymorphonuclear leukocytes as well as the formation of sequestra. Haematologically, the number of leukocytes increased by 100%, the lymphocytes by 11% and the granulocytes decreased by 39%. After i.v. injection, 99m Tc-IMP-178 rapidly cleared from the body resulting in good scintigraphic target-to-background (T/B) ratios. The highest uptake of the tracer in the pyogenic bone was observed at 60 min p.i. (0.43 ± 0.02% ID.g -1 for 99m Tc-IMP-178 and 0.30 ± 0.02% ID.g -1 for 99m Tc-IMP-100), resulting in a higher osteomyelitis-to-healthy collateral ratio with T/B of 2.40 ± 0.65 ( 99m Tc-IMP-178) compared with 1.85 ± 0.48 ( 99m Tc-IMP-100). No adverse reactions were seen after injection of 99m Tc-IMP-178. Conclusions 99m Tc-IMP-178 allows imaging of an acute osteomyelitic lesions, presumably by interaction of 99m Tc-IMP-178 with activated upregulated vascular endothelium.

A 3-Step Pretargeting Strategy to Image Infection

Abstract: A new 3-step approach to imaging infectious and inflammatory foci was developed and optimized in a rat model. The approach relies on the nonspecific localization of an anti-diethylenetriaminepentaacetic acid (DTPA) antibody in inflamed tissue. In this study, the 3-step strategy was optimized by selecting the most suitable radiolabeled hapten and tuning the dosing schedule. Methods: Wistar rats with Staphylococcus aureus infection in the left calf muscle were primed with the anti-DTPA antibody DTIn-1 (0.67, 2, or 6 nmol per rat). In the second step (1-24 h later), the anti-DTPA activity in the circulation was blocked with unlabeled bovine serum albumin DTPA-In (0.3, 1, or 3 nmol per rat). In the third step (5-30 min later), the radiolabeled hapten (monovalent or bivalent 111 In-DTPA) was administered. The in vivo distribution of the radiolabel was monitored by scintigraphic imaging and by ex vivo counting of dissected tissues. Results: Scatchard analysis revealed that the affinity of DTIn-1 for bivalent DTPA- 111 In ( 111 In-diDTPA) was 6 times higher than the affinity for monovalent 111 In-DTPA (K a 0.87 x 10 9 mol/L vs. 5.3 x 10 9 mol/L). The uptake of the bivalent chelate in the abscess was 2.5-fold higher than that of monovalent 111 In-DTPA. Most important, the bivalent chelate was completely retained in the abscess over time. Using the bivalent chelate, the optimal dosing scheme was determined with respect to the DTIn-1 dose (2 nmol per rat), the blocking agent dose (1 nmol per rat), and radiolabeled chelate dose (40 pmol per rat). The procedure was rapid; the infectious focus was clearly visualized 1 h after injection of the 111 In-labeled diDTPA, which was 5 h after administration of the anti-DTPA antibody. The nontargeted radiolabel rapidly cleared to the urine, only being retained in the abscess and the kidneys (4-6 percentage injected dose). Finally, an N 2 S 2 core was attached to the diDTPA compound, allowing the use of 99m Tc. Conclusion: This 3-step approach enables rapid imaging of infectious foci with minimal uptake in noninflamed tissues.

Progress in Gene Therapy: Seeing Is Believing

Abstract: he past few decades have seenenormous progress in molecular genet-ics. Techniques such as Southern blot-ting, Northern blotting, polymerasechain reaction, nucleotide sequencing,chromosome walking, and genetic trans-fer allow the specific isolation, charac-terization, and modification of geneticinformation. Optimists have character-ized these developments as “mankindabout to determine its destiny,”whereas others are afraid that scientistsare about to “start playing God.”Developments in molecular geneticshave given us insights, at the molecu-lar level, into vital processes in livingorganisms, such as embryonic devel-opment, growth regulation, differenti-ation, pathogenesis, and carcinogene-sis. Insights into the mechanism ofpathologic processes, such as develop-mental disorders and carcinogenesis,have stimulated efforts to develop ther-apeutic approaches to prevent or cor-rect these processes. Techniques to di-rectly change the genetic informationof a cell have raised high expectationsof the therapeutic potential of geneticmanipulation. In vitro, genes havebeen introduced successfully into cells,thus changing the genotype and thephenotype of cells. These develop-ments have raised hopes that diseasesappearing to be incurable can soon becured.Although the basic concept of genetherapy is simple and straightforward,it turned out to be much more compli-cated in actual practice. In their effortsto transfer genes into animals, investi-gators quickly realized that numeroustechnologic problems had to be over-come before gene therapy could beadded to the armamentarium of thera-peutic approaches of modern medi-cine. The main obstacles of effectivegene therapy are the limited efficiencyof the transfer, the limited specificityof the transfer, and the limited durationof the expression of the newly intro-duced gene.The design of an effective vehicle totransport the gene into the target cell,the so-called vector, appeared to be ofcrucial importance. For gene transfer,viral vectors are used. However, mostviruses do not allow the incorporationof large genes into their genome. Ret-roviruses seemed to be attractivecandidates because of their ability tostably incorporate their genetic informa-tion in the genome of the target cell.Unfortunately, the efficiency of theirtransfer was low and restricted to di-viding cells. Adenoviruses, althoughefficient vehicles for gene transfer, areeasily recognized and neutralized bythe immune system. Systematic re-search during the past decade has re-vealed new viral constructs for in vivogene transfer based on lentiviruses, ad-enovirus-associated viruses, and repli-cation-selective lytic viruses (1).As indicated, the concept of genetherapy has raised high expectations inthe medical community and in thegeneral public. However, progress isslower than expected, and in the late1990s, hope turned into skepticism.The death of 18-y-old Jesse Gelsinger,caused by an unexpectedly vigorousimmune response toward an injectedadenoviral vector in a gene therapytrial, marked the first crisis in the field(2). However, since this sad incident, afew encouraging successes have beenreported. A group at the Pasteur Insti-tute in Paris published the first un-equivocal results showing that genetherapy can treat patients with the rareimmune disease severe combined im-munodeficiency-X1 (3). Investigatorsat the Children’s Hospital of Philadel-phia and at Stanford University provedthat hemophilia in patients could bealleviated by intramuscular injection ofan adenovirus-associated viral vectorcontaining the factor VIII gene (4). Agroup at the University of Pittsburghused gene therapy to repair a defect inmice with a type of muscular dystro-phy mimicking Duchenne’s syndrome(5). With a replication-selective lyticviral construct, termed ONYX-015, tu-mor-selective tissue destruction hasbeen documented in patients with re-current refractory squamous cell carci-noma of the head and neck (6,7).For further development of genetherapy, it is of the utmost importancethat investigators have tools to deter-mine the success of the site-directedgene transfer. In virtually all gene ther-apy studies, determining whether thetransferred gene is expressed in thetarget cell is important. In that context,investigators need to determine the ef-ficiency, the specificity, and the dura-bility of expression of the therapeuticgene. Reporter gene imaging is a tech-nique that can potentially measuregene expression noninvasively. Imag-ing reporter gene expression can be avaluable tool to optimize in vivo genetransfer. The study that Yahoubi et al.(8) describe in this issue of The Jour-nal of Nuclear Medicine marks anotherstep in the development of gene ther-apy. The radiopharmaceutical in re-porter gene imaging is a substrate ofthe transferred gene, the marker gene.When the marker gene is expressed inthe target cell, the gene product (anenzyme) converts the radiopharmaceu-tical into a metabolite that is selec-tively trapped within the transfectedcell. Alternatively, the transferred genecan induce the expression of a receptoron the cell membrane (i.e., the NaIsymporter gene or the dopamine recep-