(Circulation. 1995;92:202-205.)
© 1995 American Heart Association, Inc.
Articles |
From the Departments of Surgery (J.M.DiM., P.V.T., J.W.G., R.D.D., E.C., B.M.C., H.K.L.) and Pathology (H.K.L.), Duke University Medical Center, Durham, NC.
| Abstract |
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Methods and Results An EBV-expressing BCL from a heart transplant recipient was isolated and expanded in culture. EBV-CTL were generated by stimulation of peripheral blood leukocytes with irradiated autologous tumor cells in low-dose interleukin-2. Autologous BCL, HLA-mismatched BCL, lymphokine-activated killer target cell line (Daudi), and the natural killer target cell line (K562) were used in a standard 4-hour cytotoxicity assay using 51CrO4 after 7, 14, and 28 days of stimulation. There was significant percent specific lysis of autologous BCL targets (78%) at an effector-to-target ratio as low as 20:1 as compared with control cells. EBV-CTL were then adoptively transferred into SCID mice (provided by Duke University Vivarium) that had been engrafted with autologous BCL 7 days before. There was a significant survival advantage to those mice engrafted with EBV-CTL as compared with control cells.
Conclusions The results indicate that ex vivo expansion of EBV-CTL in the absence of immunosuppressive agents results in a population that has significant antitumor activity. This strategy may be useful in the generation of EBV-CTL that might be effective antitumor agents in transplant recipients with EBV-associated lymphomas.
Key Words: lymphocytes transplantation cells heart transplant lymphoma immunodeficiency
| Introduction |
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As many as 89% of these tumors regress in thoracic organ transplant patients when immunosuppression is discontinued if the tumor appeared within the first year of transplantation.4 5 6 This phenomenon is thought to be the result of the repopulation of EBV-CTL, which are suppressed by cytotoxic agents such as cyclosporine. Therefore, it is hypothesized that autologous EBV-CTL expanded in the absence of these immunosuppressive agents may demonstrate an antitumor effect against an autologous EBV-expressing human BCL in vitro and in vivo.
| Methods |
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FACS Analysis
FACS was performed by single- or
double-staining of isolated
cells by direct techniques using phycoerythrin- or
fluorescein isothiocyanateconjugated monoclonal
antibodies. Cells were washed with cold PBS containing 0.5% BSA and
0.1% NaN3. The cells were then incubated with directly
labeled antibodies for 30 minutes at 4°C. The cells were washed and
analyzed in an EPICS C flow cytometer (Coulter) at 488 nm for
percent positivity on a log fluorescent scale. Background
control tubes were incubated with directly labeled class-matched
mouse Igs. Monoclonal antibodies CD4 (OKT4), CD8 (OKT8), and CD19
(OKB-PanB) from Ortho Diagnostics and CD3 (Leu-4), CD19
(Leu-12), CD20 (Leu-16), CD22 (Leu-14), CD23 (Leu-20), and CD56
(Leu-19) from Becton-Dickinson were used for single and dual
color-flow cytometry.
SCID Mice
SCID mice were obtained from a
hysterectomy-rederived
central inbred colony of defined flora-gnotobiotic stock maintained
at Duke University. After transfer to a biosafety level 3 isolation
facility, mice were maintained in filter-capped Micro-Isolator
cages (Lab Products Inc). Cages were housed within a HEPA-filtered
Blickman isolator system (Blickman), and mice were fed sterilized
rodent chow. Before all manipulations, Micro-Isolator cages were
transferred to a laminar flow Bioguard hood (The Baker Co), and animals
were handled aseptically by investigators wearing sterile gloves,
masks, and gowns. Blood samples were obtained from all mice before
their induction into experiments by retroorbital sinus bleeding. Serum
from mice was screened for murine Ig by ELISA and total murine Ig
levels were quantified using goat antimouse Ig. Mice with Ig levels
greater than 0.01 mg/mL, indicative of leakiness of the SCID defect,
were excluded from study.
Histopathology
The primary human tumor and SCID mice tumors
were processed
simultaneously. Formalin-fixed specimens were
dehydrated and embedded in paraffin, and 5-µm sections were cut and
stained with hematoxylin and eosin for morphological evaluation.
Immunohistochemistry
Frozen sections (5 µm) prepared in
the usual fashion were
stained by an avidin-biotin procedure with a panel of monoclonal
antibodies including CD20 (L26, B cell antigen; Dako), CD3 (pan-T cell
antigen; Becton-Dickinson), and CD45 RO (UCHL-1, pan leukocyte antigen;
Dako).
Frozen sections were also stained with antibodies to EBNA 2 (EBV-encoded nuclear antigen 2) and LMP-1 (EBV-encoded latent membrane protein) from Dako Corp.
Both frozen and paraffin sections were stained with polyclonal rabbit antihuman to kappa and lambda Ig light chain (Calbiochem-Behring Corp) for determination of clonality.
In Situ Hybridization
A biotinylated probe for EBV-DNA
(Epstein-Barr virus
Bioprobe-labeled probe; Enzo Diagnostics) was used for
the detection of EBV genomes in formalin-fixed sections.
Generation of AntiEBV CTL
Peripheral blood from the
patient was diluted 1:3
with PBS and layered over a Ficoll-Hypaque gradient. The mononuclear
cell layer was then washed twice and cocultivated with
gamma-irradiated BCL in AIM-V media with 5%
heat-inactivated autologous plasma for 7 days at a
concentration of 1x106 cell/mL with a
responder-to-stimulator ratio of 5:1. Repeated
stimulations of EBV-CTL were performed at days 7 and 21 with irradiated
BCL and a similar responder-to-stimulator ratio. After the
second stimulation, recombinant interleukin-2 (rIL-2); 10 IU/mL,
Chiron) was added, and the cells were counted and expanded every 3 days
with the addition of fresh rIL-2.
Cytotoxicity Assay
Target cells were incubated with
51CrO4
washed, resuspended at 5x104 cells/mL, and combined in
triplicate wells of 98-well round-bottom plates with effector cells
for E-T (effector to target) ratios of varying numbers. Final volumes
of each well were adjusted to 0.2 mL with AIM-V media. Wells containing
only culture media and target cells or 5% triton and target cells
served as spontaneous and maximum 51Cr release controls,
respectively. The plates were incubated at 37°C in 5%
CO2 for 4 hours; then 0.10 mL of medium from each well was
removed for counting in a Packard Prias gamma spectrometer. Percent
specific lysis was calculated by standard methods.
Tumor Cell Engraftment and Development
A reliable and
reproducible model of human B-cell tumors
(SCID-BCL) in SCID mice has been developed in this laboratory. After
engraftment with PBL (peripheral blood leukocytes), engraftment with
PBL followed by inoculation with EBV, and engraftment of LCL
(lymphoblastoid cell line) results in the development of B cell tumors.
To test the effect of adoptive transfer of EBV-CTL on SCID/BCL
development 25x106 EBV-CTL were inoculated into the
peritoneal cavity of SCID mice 7 days after IP inoculation of
5x106 tumor cells or Dulbecco's PBS (Gibco). Mice
were monitored twice weekly, weight and examination for tumor
development. Mice were anesthetized with halothane (Fluothane;
Ayerst), killed by cardiac puncture, and autopsied. At autopsy,
thoracic and abdominal cavities were examined, and tumors were
sectioned and cryopreserved in liquid nitrogen or fixed in 10%
neutral-buffered formalin. All procedures were approved and
conducted in accordance with institutional guidelines.
| Results |
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FACS Analysis
As shown in the Table
, the
EBV-CTL generated
progressed to 97% CD3+ (pan-T cell) and 88% CD8+ (cytotoxic T cell)
after 28 days of stimulation. The majority of CD8+ cells were positive
for S6F1 (cytotoxic T cell). The population of B cells or natural
killer (NK) target cells diminished with time, to near zero.
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Cytotoxicity Assay
Effective cytolysis of the autologous
targets was demonstrated by
EBV-CTL 7, 14, and 21 days after stimulation as seen in Fig 3
.
No cytolysis of HLA-mismatched EBV-expressing cell
lines was seen. Minimal cytolysis of the NK target K562 was seen on day
7, which diminished by day 14. There was no activity against LAK
(lymphokine activated killer) cell target Daudi (data not shown).
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Adoptive Transfer of EBV-CTL
Results of SCID-BCL and BJAB-BL
engraftment and survival as well
as the inoculation of EBV-CTL are shown in Fig 4
.
Engraftment of posttransplant B-cell lymphoma and Burkitt's lymphoma
led to the characteristic tumor development and death of the animals in
50 days. Animals inoculated with EBV-CTL 7 days after engraftment
with the EBV-negative cell line BJAB (Burkitt's lymphoma) showed no
significant difference in survival from the animals engrafted with
tumor and then given PBS (P=NS via log rank test). In
contrast, animals given autologous EBV-CTL 7 days after engraftment of
EBV-expressing BCL had no deaths (P<.05 via log rank
test).
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| Discussion |
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Wherever productively infected cells are cleared by the immune system, latently infected B cells persist for the life of the host. In fact, B cells infected with EBV become immortalized B-cell lines and provide a model system of EBV latency.12 13
Evidence suggests that cellular immune response may be effective in controlling EBV-associated LPDs and BCLs in patients who have undergone transplantation.14 15 The term LPD applies to the development of continuously proliferating B lymphocytes, presumably stimulated by EBV infection. This is believed to be related to the failure of the immune system, especially the T-cell population, which is suppressed by drugs such as cyclosporine, to respond normally to EBV-infected B lymphocytes.16 17 The fact that the risk of LPD and the mortality from it increases with the duration of immunosuppression adds validity to this theory. In approximately 89% of patients in whom BCL developed within 1 year of transplantation, there was complete regression of the lesions after reduction of immunosuppressive therapy alone.18 19 Thus, the decrease in number or function of EBV-CTL may allow for unchecked proliferation of EBV-driven LPD.
One report on EBV-associated LPD after allogeneic bone marrow transplantation documented successful eradication of disease after infusions of donor-derived pooled leukocytes. Because of the known high-frequency of EBV-specific CTL precursors in the blood of seropositive normal donors, it is reasonable to suggest that donor-derived EBV-reactive T cells had a critical role in the response noted. More specific therapy with just EBV-CTL may provide a tailored approach with less systemic side effects. Continued study of the mechanisms underlying the cause of EBV-driven LPD and the cellular immune response, including the EBV-specific CTL response to it, may provide novel treatment strategies against BCLs in the organ-transplant recipient.
| Selected Abbreviations and Acronyms |
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| Acknowledgments |
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| Footnotes |
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| References |
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