| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Basic Science Investigations |
-Radiation Versus Radioimmunotherapy with 
- and ß-Emitting Radioisotopes
1 Department of Nuclear Medicine, Albert Einstein College of Medicine, Bronx, New York
2 Department of Radiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey
3 Department of Medicine, Albert Einstein College of Medicine, Bronx, New York
4 Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
-radiation, such that the doses of several thousand gray are required for 90% cell killing, whereas for mammalian cells the lethal dose is only a few gray. We compared the susceptibility of human pathogenic fungi Cryptococcus neoformans (CN) and Histoplasma capsulatum (HC) to external -radiation and to the organism-specific mAbs 18B7 and 9C7, respectively, conjugated to 213Bi and 188Re radionuclides. Methods: CN and HC cells were irradiated with up to 8,000 Gy (137Cs source, 30 Gy/min). RIT of CN with 213Bi- and 188Re-labeled specific mAb and of HC with 188Re-labeled specific mAb used 0–1.2 MBq per 105 microbial cells. After irradiation or RIT, the cells were plated for colony-forming units (CFUs). Cellular dosimetry calculations were performed, and the pathway of cell death after irradiation was evaluated by flow cytometry. Results: Both CN and HC proved to be extremely resistant to -radiation such that significant killing was observed only for doses of >4,000 Gy. In contrast, these cells were much more susceptible to killing by radiation delivered with a specific mAb, such that a 2-logarithm reduction in colony numbers was achieved by incubating them with 213Bi- and 188Re-labeled mAb 18B7 or with 188Re-9C7 mAb. Dosimetry calculations showed that RIT was 
1,000-fold more efficient in killing CN and 100-fold more efficient in killing HC than -radiation. Both -radiation and RIT caused cell death via an apoptotic-like pathway with a higher percentage of apoptosis observed in RIT-treated cells. Conclusion: Conjugating a radioactive isotope to a fungal-specific antibody converted an immunoglobulin with no antifungal activity into a microbicidal molecule. RIT of fungal cells using specific antibodies labeled with 
- and ß-emitting radioisotopes was significantly more efficient in killing CN and HC than -radiation when based on the mean absorbed dose to the cell. These results strongly support the concept of using RIT as an antimicrobial modality.
Key Words: radioimmunotherapy • infection • dosimetry • pathogenic fungi
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
-radiation relative to other microorganisms and mammalian cells (1–5). For example, a dose of several thousand gray is required to achieve 90% cell killing of fungal cells, whereas the lethal dose for mammalian cells is only a few gray. The mechanisms responsible for these differences are not well understood but could involve more efficient mechanisms of DNA repair by fungi when the damage is caused by -rays. A dramatic example of the radioresistance of fungi is provided by reports of numerous melanotic fungal species colonizing the walls of the damaged nuclear reactor at Chernobyl in extremely high radiation fields (6).
We have recently shown that the human pathogenic fungus Cryptococcus neoformans (CN) is susceptible to killing by radioimmunotherapy (RIT) in vitro with an organism-specific monoclonal antibody (mAb) radiolabeled with the -emitter 213Bi or the ß-emitter 188Re (7). For the purposes of this study, the term "RIT" is used to refer to the microbicidal effects of radiolabeled specific mAb on fungal cells in vitro. This process reflects an enhanced microbicidal activity resulting from the delivery of a radionuclide to the fungal cell by a specific antibody that binds to the microbe. Furthermore, we established that this modality was effective therapeutically in a murine model of experimental cryptococcosis (7). This result was encouraging for developing a new therapy for cryptococcosis since this fungus is a major cause of chronic and often lethal illness in immunocompromised individuals (8). Our protocol used radiolabeled mAb with activities of 1.85–7.4 MBq (50–200 µCi) per mouse, which were fungicidal in vivo. By using an antibody to deliver a radionuclide to the fungal cell surface we observed microbicidal effects with radiation doses that were several orders of magnitude lower than expected from assumptions based on studies using external -radiation sources. Consequently, by attaching a radionuclide to an immunoglobulin we converted an antibody with no inherent antifungal activity into a microbicidal molecule.
The apparent efficacy of RIT as an antifungal therapeutic modality may appear to be in conflict with older reports that fungi are highly resistant to radiation. Therefore, we have revisited the question of fungal susceptibility to radiation by studying the microbicidal properties of various types of radiation using 2 medically relevant fungal species CN and Histoplasma capsulatum (HC). CN and HC are the most common causes of fungal meningitis and pneumonia, respectively (8,9). Antibodies for HC have recently been described (10) and were available for use in RIT. In this study we have analyzed the susceptibility of CN and HC to -radiation versus RIT with - and ß-emitting radioisotopes, performed extensive cellular dosimetry calculations, and investigated the pathway of cell death after irradiation by flow cytometry.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
Antibodies
mAb 18B7 (IgG1) binds to CN capsular polysaccharide (11). mAb 9C7 (IgM) binds to a 17-kDa protein antigen on the surface of the HC cell wall (10). mAb MOPC21 (ICN Biomedicals) was used as an irrelevant isotype-matched control for 18B7, and mAb UNLB (clone 11E10; Southern Biotechnology Associates) was used for 9C7.
Radioisotopes and Quantification of Radioactivity
188Re in the form of Na perrhenate Na188ReO4 was eluted from a 188W/188Re generator (Oak Ridge National Laboratory [ORNL]). 225Ac for construction of a 225Ac/213Bi generator was acquired from ORNL. The 225Ac/213Bi generator was constructed using an MP-50 cation-exchange resin column and 213Bi was eluted with 0.15 mol/L hydroiodic acid in the form of 213BiI3 as described (12).
The radioactive samples were counted in a dose calibrator when their activity was >185 kBq (>5 µCi) and counted in a -counter with or without appropriate dilution when their activity was <185 kBq (<5 µCi). A -counter (Wallac) with an open window was used to count the 188Re and 213Bi samples. Samples containing known activities were counted to obtain experimentally determined conversion factors of 23 cpm/Bq (840,000 cpm/µCi) for 188Re and 41 cpm/Bq (1,500,000 cpm/µCi) for 213Bi.
Susceptibility of CN and HC to External -Radiation
Approximately 105 CN or HC cells were placed in microcentrifuge tubes in 0.5 mL PBS and irradiated at room temperature in a cell irradiator equipped with a 137Cs source at a dose rate of 30 Gy/min. The cells were exposed to doses of up to 8,000 Gy (800 krad). To determine if unlabeled antibody might contribute to killing of fungal cells, in several experiments CN or HC cells were irradiated with 4,000 Gy (0–400 krad) in the presence of 10 µg 18B7 or 9C7 mAb, respectively. The potential protective effect of the polysaccharide capsule surrounding CN cells was investigated by irradiating acapsular CN strain CAP67. After radiation exposure, 103 cells were removed from each tube, diluted with PBS, and plated to determine viability as measured by colony-forming units (CFUs). Experiments were performed in duplicate.
Radiolabeling of Antibodies with 188Re and 213Bi
Our previously described procedure (7) was used. Briefly, mAbs were labeled directly with 188Re via reduction of antibody disulfide bonds by incubating the antibody with a 75-fold molar excess of dithiothreitol for 40 min at 37°C followed by centrifugal purification on Centricon-30 or Centricon-50 microconcentrators with 0.15 mol/L NH4OAc, pH 6.5. Simultaneously, 110–370 MBq (3–10 mCi) 188ReO4- in saline were reduced with SnC12 by incubation in the presence of Na gluconate, combined with purified reduced antibodies and kept at 37°C for 60 min. Radioactivity not bound to the antibody was removed by centrifugal purification on Centricon microconcentrators.
For radiolabeling with 213Bi, mAbs were conjugated to the bifunctional chelator N-[2-amino-3-(p-isothiocyanatophenyl)propy1]-trans-cyclohexane-1,2-diamine-N,N',N'',N''',N''-pentaacetic acid (CHXA''). CHXA''-conjugated mAbs were radiolabeled with 213Bi by incubating them for 5 min with 213BiI3 at room temperature. If required, the radiolabeled antibodies were purified by size-exclusion high-performance liquid chromatography (TSK-Gel G3000SW; TosoHaas).
In Vitro RIT of CN and HC with Radiolabeled Antibodies
The RIT of HC was performed only with 188Re-labeled antibodies as 9C7 mAb proved to be not amenable to conjugation with CHXA" for further radiolabeling with 213Bi. 188Re- or 213Bi-radiolabeled mAb 18B7 and 188Re-radiolabeled 9C7 were used to determine the susceptibility of CN and HC to RIT, respectively, in vitro. mAbs MOPC21 and UNLB were radiolabeled in the same manner and served as isotype-matching controls for 18B7 and 9C7, respectively. The cells were incubated at 37°C for 30 min in PBS containing 10 µg 188Re-mAb (1.2 MBq [0–32 µCi]) or 213Bi-mAb (0.12 MBq [0–3.2 µCi]) to allow time for the radiolabeled antibodies to bind to the cell surfaces. For the control, CN or HC cells were incubated with 10 µg prereduced or CHXA"-conjugated unlabeled mAbs. To measure the kinetics of antibody binding to the cells, aliquots of cell suspension were removed at 0, 10, 20, and 30 min, centrifuged to separate the cell pellet from the supernatant, and the cell pellet was counted in a -counter. After a 30-min incubation with the antibodies, the cells were washed free of extracellular activity and maintained in suspension on a rocker at 4°C in PBS for a period of either 1 or 48 h for 213Bi-mAbs or 188Re-mAbs, respectively. The cells were not dividing during the incubation and maintenance periods because they were maintained in PBS, which lacks nutrients. To ascertain that the radioactivity remained bound to the cells at the end of the 1- or 48-h incubation period, aliquots of cell suspension were removed, counted in the -counter, centrifuged to separate the cell pellet from the supernatant, and washed with PBS, and the cell pellet was counted in a -counter. At the end of incubation, 103 cells were plated for CFUs and the colonies were counted after 48 h at room temperature.
Cellular Dosimetry
Following the general formalism for cellular dosimetry given by Equation 7 in (13), the mean absorbed dose to the cell from cellular radioactivity is given by:
 | (Eq. 1) |
CS) is the cellular S value (absorbed dose to the cell per unit cumulated activity) for the jth radionuclide localized on the cell surface (CS) of the cell (C). The cumulated activity à can be written as:
 | (Eq. 2) |
Cumulated Activity During Incubation Period at 37°C.
According to Makrigiorgos et al. (14), when the cellular uptake is linear in time and there is no biologic elimination of the radioactivity, the cellular radioactivity at time t of the incubation period is given by:
 | (Eq. 3) |
is the physical decay constant for the radionuclide ( = 0.693/Tp, where Tp is the physical half-life). Makrigiorgos et al. (14) have also shown that the cumulated activity at time t = tI is given by:
 | (Eq. 4) |
Cumulated Activity During Maintenance Period at 4°C.
The activity present in the cell at the beginning of the maintenance period is given by:
 | (Eq. 5) |
Assuming no biologic elimination of the radioactivity from the cells, the cellular activity as a function of time t during the maintenance period is then:
 | (Eq. 6) |
The cumulated activity during the maintenance period tM is then given by:
 | (Eq. 7) |
Cumulated Activity During Colony-Forming Period at Room Temperature.
Finally, assuming that the activity is eliminated from the cells by both biologic processes of an exponential nature and physical decay, the activity present in the cell at time t during the colony-forming period is given by:
 | (Eq. 8) |
The quantity e is the effective decay constant, where e = + b, and b is the biologic disappearance constant (15). The cumulated activity during the colony-forming period tCF is therefore given by:
 | (Eq. 9) |
Cellular S Values and Physical Decay Constants.
The cellular S values are obtained from the tabulations in the Society of Nuclear Medicine’s MIRD Cellular S Values monograph (13). Since the antibodies remain on the cell surfaces, only S(CCS) is required. The radii of the CN and HC cells are approximately 10 and 5 µm, respectively. The corresponding S values for 188Re are 6.82 x 10-5 and 3.34 x 10-4 Gy Bq-1s-1 for CN and HC, respectively. As expected, the cellular S values are quite sensitive to cell size. Deciding which S values are required for 213Bi dosimetry is more complex due to its decay to various daughter radionuclides (Fig. 1). The violence of the 213Bi -decay can be assumed to disrupt the radionuclide-antibody bond with consequent departure of the daughter 209Tl from the cell surface before it has a chance to decay. The same is assumed for 209Pb, the daughter of 213Po. Therefore, only S values for 213Bi and 213Po are required. For 213Bi localized on the surface of cells having radii of 10 and 5 µm, S(CCS) is 4.14 x 10-4 and 1.64 x 10-3 Gy Bq-1s-1, respectively. No S values are tabulated in (13) for 213Po, which emits an 8.375-MeV -particle. Interpolation of the cellular S values for -particles given in Appendix III of MIRD Cellular S Values (13) gives S(CCS) = 1.21 x 10-2 and 4.74 x 10-2 Gy Bq-1s-1 for 213Po on the surface of cells with radii of 10 and 5 µm, respectively. The physical decay constant for a radionuclide is given by = 0.693/Tp. Therefore, (188Re) = 6.80 x 10-4 min-1 and (213Bi) = 1.52 x 10-2 min-1.
|
-irradiation or RIT, the cells were permeabilized and fixed with 70% ethanol, cellular RNA was destroyed by treatment with ribonuclease A at 50°C for 1 h, the DNA was stained with propidium iodide at pH 7, and the fluorescence per cell was measured in a flow cytometer (16). |
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
-Radiation-radiation, with 10% of the cells surviving at the doses of 4,000 Gy ( 400 krad), and <1% surviving a dose of 8,000 Gy (800 krad) (Figs. 2A and 2B).
|
|
CS) = (0.218, s)Ao (6.82 x 10-05, Gy Bq-1 s-1) = 0.0149 Ao, Gy, where Ao is the kBq added to the tube of cells.
CN, 213Bi-18B7 mAb.
Substituting k = 8.5 x 10-8 min-1, (213Bi) = 1.52 x 10-2 min-1, tI = 30 min, tM = 60 min, and tCF = 2,880 min into Equations 4 and 7 gives ÃI = (0.00170, s)Ao, ÃM = (0.00382, s)Ao, and ÃCF = (0.00256, s)Ao. The total cumulated activity à = (0.00808, s)Ao. Assuming that only the 213Bi and 213Po decays deposit energy in the cell and that 213Po is in equilibrium with 213Bi, Equation 1 gives DC = à (S(213Bi,CCS) + 0.9784 S(213Po,CCS)). Substitution of the S values gives DC = 0.0990 Gy/kBq of 213Bi added to the tube.
HC, 188Re-9C7 mAb.
Uptake of this mAb is reasonably linear up to 20 min; therefore, the dosimetry can be simplified by taking tI = 20 min. The remaining 10 min of this period can then be added to the maintenance period so that tM = 2,890 min. Finally, as before, tCF = 2,880 min. There is no biologic elimination during tI or tM so only physical decay occurs during these periods. Substituting k = 1.38 x 10-7 min-1 (Fig. 2) and the various parameters into Equations 4 and 7 gives ÃI = (0.00164, s)Ao and ÃM = (0.207, s)Ao. During cell division, which takes about 2 h, the membrane is shared between parent and daughter HC cells. Therefore, it is assumed that the bound radioactivity is divided between the 2 cells. Consequently, the effective half-time of the radioactivity in the cell during the colony-forming period is e = + b = 6.8 x 10-4 min-1 + 0.693/120 min-1 = 0.00646 min-1. Substituting the various parameters into Equation 9 gives ÃCF = (1.77 x 10-4, s)Ao. Finally, as per Equation 2, the sum is à = ÃI + ÃM + ÃCF = 0.209 Ao s. The absorbed dose is given by Equation 1, where DC = à S(CCS) = (0.209, s) Ao (3.34 x 10-4 Gy Bq-1 s-1) = 0.0698 Ao, Gy, where Ao is the kBq added to the tube of cells.
Susceptibility of CN and HC to RIT with 188Re- and 213Bi-Radiolabeled Antibodies
The RIT of CN cells was performed with both 188Re- and 213Bi-radiolabeled antibodies. The dependence of the RIT-treated CN and HC cell survival on the amount of radioactivity added to the cells and the cellular absorbed dose delivered by radiolabeled antibodies is presented in Figure 4. Control experiments demonstrated that unlabeled mAbs in either prereduced form or conjugated with CHXA" did not cause the death of fungal cells. Interestingly, in the case of CN, the doses of 2 and 1 Gy (0.2 and 0.100 krad) for 188Re-18B7 and 213Bi-18B7, respectively, eradicated >99% of CN cells (Figs. 4A and 4B). In contrast, radiolabeled control antibody MOPC21 with the same specific activity produced only minimal killing within the investigated range of doses (P < 0.001). The significantly higher killing associated with the specific antibody almost certainly reflects higher radiation exposure for CN as a consequence of antibody binding to the CN capsule.
|
-rays, and cells treated with RIT are presented in Table 1 for both CN and HC. Exposure of fungal cells to 4,000 Gy (400 krad) of -radiation caused an apoptosis-like phenomenon in a significant percentage of CN and HC cells. Strikingly, RIT of CN with 213Bi-18B7 caused 80%–90% of the cells to die through an apoptotic-like pathway, which is consistent with the very low survival rate of 213Bi-18B7-treated cells at the highest dose of 11.7 Gy (1.17 krad) (Fig. 4B).
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
-radiation and RIT using well-established methods of dosimetry.
Comparing the response of CN and HC fungi to -radiation and RIT with 188Re- and 213Bi-labeled antibodies revealed that RIT with organism-specific radiolabeled antibodies (Figs. 4A and 4B) was significantly more efficient in mediating fungal cell killing than exposure to external -radiation (Fig. 1). The radiation doses required to kill CN fungal cells were 1,000-fold lower when delivered by radiolabeled antibodies compared with -radiation and, consistent with classical radiobiology, the -emitter 213Bi was about 2 times more lethal than the ß-emitter 188Re, presumably due to the emission of high linear-energy-transfer -particles that can kill a cell with 1 or 2 hits. The dose from -particles constitutes >97% of the cellular absorbed dose from 213Bi.
Furthermore, the dose rates delivered by the radiolabeled antibodies were thousands of times lower than those delivered acutely with the external -irradiation (30 Gy/min). This is consistent with clinical RIT, where peak dose rates of 0.1 Gy/h (10 rad/h) (18) are observed. For comparison, high-dose rate radiation, which is typical for external beam radiation therapy, delivers 60 Gy/h (6 krad/h). Thus, from the viewpoint of radiation therapy, RIT delivers suboptimal dose rates to tumors (or to microbial cells in our case). However, despite this, targeted radionuclide therapy can be effective through mechanisms such as the induction of apoptosis in irradiated cells, "bystander" effect (death of adjacent, nonirradiated cells), and cell cycle arrest (18,19,22,23). The flow cytometry results in Table 1 indicate that low doses of particulate radiation delivered by organism-specific antibody caused the majority of treated cells to die by an apoptotic-like mechanism, whereas much higher doses of -radiation induced this apoptosis-like phenomenon only in 30% of irradiated cells. These results are consistent with and supportive of the fact that RIT using - and ß-emitters is effective despite radiation doses that seem inadequate for microbicidal effects according to standard cellular dosimetry calculations. The surprising efficacy of RIT could reflect the occurrence of a different cascade of events resulting from the interaction of the electrons and -particles (emitted by radiolabeled antibodies on the cell surface) with the cell membrane itself or with structures within the cell. In fact, there is new evidence to suggest that cellular radioactivity can cause uniquely different gene expression profiles than external -rays (24). Alternatively, it is conceivable that antibody molecules also mediate local effects that enhance the microbicidal efficacy of radiation. In this regard, antibody molecules have recently been shown to be catalysts for the production of microbicidal oxygen-related oxidants (25). Hence, particulate radiation combined with local production of toxic oxidative molecules could result in synergistic antimicrobial effects that translate into significantly greater efficacy for RIT than would be expected from dosimetry calculations alone.
Despite the fact that HC and CN responded similarly to external -radiation (Figs. 2A and 2B), HC was less susceptible to the RIT with 188Re-labeled specific antibody than CN (Figs. 4A and 4C). A cellular absorbed dose of about 80 Gy (8 krad) was required to eradicate 80% of HC cells (Fig. 4C), whereas <1 Gy was required to eradicate a similar fraction of CN cells (Fig. 4A). The difference in calculated cellular absorbed doses is, in part, attributed to their very different cell diameters (5 µm for HC and 10 µm for CN), which in turn affects their mean absorbed dose per decay (S value). Although the cellular absorbed doses required to eradicate a specific fraction of cells may be quite different, it is possible that the local absorbed doses on the cellular membrane are more similar. Another factor that may be involved in the observed differences in responses is a lower density of antibody molecules on the surface of HC cells relative to CN cells. For CN, 108 antibody molecules were bound to each cell whereas, for HC, only 2 x 107 antibody molecules were bound to each cell. Furthermore, the fact that the mAbs used in CN and HC RIT are of IgG1 and IgM isotypes, respectively, raises the possibility that isotype-related effects contribute to the lethality of RIT. Nevertheless, regardless of the mechanisms involved, the cellular absorbed dose of 80 Gy (8 krad) delivered by 188Re-9C7 mAb was almost 100 times lower than the dose of -radiation needed to cause comparable killing of HC cells (Figs. 1B and 4C). The killing was antibody-specific since incubation of HC with radiolabeled control antibody resulted in only negligible killing of HC cells.
|
CONCLUSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
-radiation. The results provide strong experimental support for the concept of using RIT as an antimicrobial modality. The mechanism for this effect is uncertain but may involve a cascade of different events that ultimately lead to cell death by apoptosis. These results suggest that the relative sensitivity of fungi toward particulate radiation delivered by specific radiolabeled antibodies can be used for designing novel therapeutic strategies against difficult-to-treat fungal infections.
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
For correspondence or reprints contact: Ekaterina Dadachova, PhD, Department of Nuclear Medicine, Albert Einstein College of Medicine, 1695A Eastchester Rd., Bronx, NY 10461.
E-mail: edadacho{at}aecom.yu.edu.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
This article has been cited by other articles:
|
|
 |
|
  R. A. Bryan, X. Huang, A. Morgenstern, F. Bruchertseifer, A. Casadevall, and E. Dadachova Radiofungicidal Effects of External Gamma Radiation and Antibody-Targeted Beta and Alpha Radiation on Cryptococcus neoformans Antimicrob. Agents Chemother., June 1, 2008; 52(6): 2232 - 2235. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Dadachova, R. A. Bryan, X. Huang, G. Ortiz, T. Moadel, and A. Casadevall Comparative Evaluation of Capsular Polysaccharide-Specific IgM and IgG Antibodies and F(ab')2 and Fab Fragments as Delivery Vehicles for Radioimmunotherapy of Fungal Infection Clin. Cancer Res., September 15, 2007; 13(18): 5629s - 5635s. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Ikeda, F. Saito, M. Matsuo, K. Kurokawa, K. Sekimizu, M. Yamaguchi, and S. Kawamoto Contribution of the Mannan Backbone of Cryptococcal Glucuronoxylomannan and a Glycolytic Enzyme of Staphylococcus aureus to Contact-Mediated Killing of Cryptococcus neoformans J. Bacteriol., July 1, 2007; 189(13): 4815 - 4826. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. R. Martinez, R. A. Bryan, C. Apostolidis, A. Morgenstern, A. Casadevall, and E. Dadachova Antibody-guided alpha radiation effectively damages fungal biofilms. Antimicrob. Agents Chemother., June 1, 2006; 50(6): 2132 - 2136. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. V.S.V. Neti and R. W. Howell Log Normal Distribution of Cellular Uptake of Radioactivity: Implications for Biologic Responses to Radiopharmaceuticals J. Nucl. Med., June 1, 2006; 47(6): 1049 - 1058. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. A. Bryan, O. Zaragoza, T. Zhang, G. Ortiz, A. Casadevall, and E. Dadachova Radiological Studies Reveal Radial Differences in the Architecture of the Polysaccharide Capsule of Cryptococcus neoformans Eukaryot. Cell, February 1, 2005; 4(2): 465 - 475. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Dadachova, J. D. Nosanchuk, L. Shi, A. D. Schweitzer, A. Frenkel, J. S. Nosanchuk, and A. Casadevall Dead cells in melanoma tumors provide abundant antigen for targeted delivery of ionizing radiation by a mAb to melanin PNAS, October 12, 2004; 101(41): 14865 - 14870. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY | THE JOURNAL OF NUCLEAR MEDICINE |
) and 188Re-9C7 mAb (
) to the cell surfaces of CN and HC, respectively. The 188Re-18B7 mAb data are fitted to a linear function with a resulting slope of k = 8.50E-08 min-1. The 188Re-9C7 data up to a time of 20 min are similarly fitted with a resulting slope of k = 1.38E-07 min-1. mAb 18B7 has IgG1 isotype, and 9C7 has IgM isotype.