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By
Catherine M. Bollard, M.D.
With the exception of Hodgkin’s disease
(HD), patients who received
minimal previous therapy or patients relapsing years after
therapy, patients with lymphoma who do not enter remission or
who subsequently relapse are rarely cured using therapy at
conventional doses.
Non-fatal sequelae of therapy, such as altered somatic growth,
infertility and restrictive lung disease can seriously affect
the quality of life of survivors. It is desirable to
develop novel therapies that could improve disease-free survival
in relapsed/refractory patients and might ultimately reduce the
incidence of long-term treatment related complications in all
patients.
Cellular immune responses have significant therapeutic potential
as evidenced by the graft versus lymphoma effect following
allogeneic stem cell transplantation for lymphoma, which has
resulted in reduced relapse rates. Minor histocompatibility
antigen disparities are the presumed targets of donor T cells
with anti-lymphoma activity in the allogeneic setting.
In addition, the development of autologous graft-versus-host
disease (GVHD) is thought to occur from recognition of host
cells by autoreactive T cells and occurs in up to 8 percent of
autologous transplants. The autologous GVHD reaction usually is
mild and only involves the skin and self-limiting
compared to GVHD occurring post-allogeneic transplant. Recently,
it has been observed in phase I clinical trials that Cyclosporin
A, tacrolimus and Interleukin-2 are able to induce a clinical
GVHD following autologous transplant by potentially modulating
cytotoxic autoregulatory T cells. Clinical studies where autologous GVHD is induced post transplant have shown promising
results.
Initial approaches to expand T cells from heavily pre-treated
patients proved difficult due to the degree of lymphopenia these
patients had pre transplant. Several groups have explored the
feasibility of expanding CD4+ve T cells for adoptive transfer
for clinical use. CD3/28 expanded T cells were administered in a
dose escalation study to patients with refractory or relapsed
non-Hodgkin's lymphoma (NHL) 14 days following high dose
chemotherapy and CD34-selected autologous rescue. Although a
rapid reconstitution of lymphocytes and complete clinical
responses were observed, there were persistent defects in CD4 T
cells.
The ability of DLI to effect anti tumor responses initially was
described in patients with CML in hematologic relapse post
allogeneic SCT. The list of malignancies that are sensitive to
the effects of DLI has been expanded to include lymphoma. The
timing and dosage of unmanipulated T cells that can be
administered with relative safety remain poorly defined, and
such therapy is limited by potentially fatal complications that
arise from alloreactive T cells also present in the lymphocyte
infusion.
Probably the gold standard to demonstrate the efficacy of T cell
therapy is for the treatment of EBV-associated post transplant
lymphoma. Immunotherapeutic strategies aimed at reconstituting T
cell responses to EBV have now been used for more than 10 years
and have improved the outcome of this disease post-stem cell
transplant. The rationale for this strategy was that most EBV
seropositive individuals have a high frequency of EBV specific
precursors so that transfer of unmanipulated donor lymphocyte
populations should be able to restore the immune response to EBV.
In the Sloan Kettering experience, the overall response rate is
high with 20 of 22 patients attaining complete remissions. Other
centers have seen lower response rates to donor leukocyte
infusions, which may reflect different patient populations or
better outcome with early diagnosis and treatment.
Several groups also have used DLI for the treatment of residual
Hodgkin's and non-Hodgkin's lymphoma following allogeneic stem cell
transplant. The existence of significant graft versus Hodgkin
lymphoma activity following allogeneic transplantation has
proven difficult to establish and is probably hindered by the
particularly high treatment related mortality rates in this
heavily pretreated patient population. There is evidence from
transplant registry-based studies that relapse rates are lower
in HD patients who develop GVHD post
allogeneic SCT versus those who do not. One study specifically
examined the toxicity and efficacy of escalating doses of
unmanipulated DLIs in recipients of so called submyeloablative
stem cell transplants. In 12 lymphoma patients who received DLI for residual disease or disease progression, five
HD patients were complete responders. Further investigation
of allogeneic approaches in HD and NHL are clearly warranted. However, the development of strategies to
maximize efficacy and minimize the toxicity of these T cell
therapies for the treatment of lymphoma is critical.
EBV-specific CTL for the treatment of EBV-associated post
transplant lymphoma
The efficacy of antigen-specific cytotoxic T cells (CTL) has
been clearly demonstrated for the treatment of EBV-associated
post (stem cell) transplant lymphoma where a physiological
approach to restore the balance between Epstein Barr virus and
immune system is the adoptive transfer of virus-specific CTL.
Our group has used donor-derived EBV-specific T cell lines as
prophylaxis for EBV-induced lymphoma in more than 60 patients
post HSCT. None of the patients treated with this approach
developed post-transplant lymphoproliferative disease (PTLD), compared with an incidence of 11.5 percent in a
historical non-treated control group. Gene-marking of donor CTLs
allowed us to show persistence of infused CTL for as long as
seven years. Furthermore, high EBV genome loads that existed
prior to CTL administration rapidly decreased to normal levels
with an increase of EBV-specific cytotoxicity. We have also used
EBV-CTL to treat three patients with overt post transplant
lymphoma. Two of them were successfully treated and gene-marked
CTL were shown to accumulate at sites of disease.
When targeting EBV-associated post transplant lymphoma in the
solid organ transplant setting, the application of CTL therapy
is limited by the fact that patients must remain on immune
suppression and the failure of standard techniques to generate
CTL from EBV-seronegative recipients. Generation of EBV-specific
CTL after seroconversion can circumvent this problem. However,
since rapid intervention after the diagnosis of PTLD is often
necessary, this approach may not allow for enough time to expand
the required number of CTL.
EBV antigen-specific CTL for the treatment of EBV-positive
Hodgkin Disease and non-Hodgkin Lyphoma developing in the immune
competent patient
Having shown that the EBV-positive cells in PTLD, which express a wide range
of EBV encoded antigens, are susceptible to immunotherapy the
next strategy was to evaluate if the malignant cells of Hodgkin
disease, which express a more restricted pattern of antigens,
are also targets for this approach. EBV-associated HD and NHL
that develop in
the immune competent host show type II latency. This viral gene
expression is limited immunosubdominant proteins such as latent
membrane protein (LMP) 1 and 2. However, these antigens could
still serve as targets for immunotherapy approaches. In a Phase
I dose escalation study, we evaluated the use of autologous EBV-specific
CTL for patients with EBV-positive Hodgkin disease. Viral load
decreased, demonstrating the biologic activity of the infused
CTLs. Gene-marking studies showed that infused effector cells
could further expand by several logs in vivo (persisting up to
12 months), as well as traffic to tumor sites. Tetramer and
functional analyses showed that T cells reactive with the
tumor-associated antigen LMP2 were present in the infused lines,
expanded in peripheral blood following infusion and also
entered tumor. Following CTL infusion, five patients were in
complete remission at up to 40 months, two of whom had clearly
measurable tumor at the time of treatment.
Although these results using EBV-specific CTL have been
promising, apart from the patients with relatively low tumor
burden who have demonstrated durable responses, the majority of
the anti-tumor responses have been transient. No patient
with aggressive, bulky relapsed HD has been cured
by CTL therapy alone.
We have hypothesized that by expanding CTL specifically
targeting type II viral latency antigens, it might have
greater efficacy in these patients. We have generated CTL lines
specific for the tumor-associated antigen LMP2, in more than 17
patients with EBV+ve HD or EBV positive B-cell or T/NK-cell NHL.
So far, we have treated 14 patients. Although this study is
ongoing at Texas Children’s Hospital and Baylor College of
Medicine, immunotherapy with autologous LMP2-CTL appears well
tolerated in patients with relapsed EBV+ve HD/NHL and infused
LMP2-CTL cells can accumulate to tumor sites and induce clinical
responses.
Viral antigens such as the EBV associated proteins expressed on
tumor cells are an attractive target for immunotherapeutic
strategies. However, the approach is limited by virtue of the
fact that at least 60 percent of Hodgkin's and non-Hodgkin's tumors
are negative for EBV. Therefore, other targets need to be
identified to broaden the use of antigen-specific T cells for
lymphoma. Cancer testis (CT) antigens have an expression pattern
that is predominantly restricted to testis and placenta in
normal tissues, yet they are expressed in many different
histological types of cancers including Hodgkin's Lymphoma and
NHL. These cancer testes antigens therefore have potential to be
used as a target for many cancer immunotherapies. However, the
difficulty lies in the in vitro expansion of T cells specific
for these tumor-associated antigens to the numbers required for
clinical use.
The generation of tumor specific T-cells either ex-vivo or by
immunization is limited by poor antigenicity of most tumors. A
novel way of circumventing this problem is the transduction of T
cells with chimeric surface proteins, which transmit TCR signals
in response to target cells. The generation of T lymphocytes
with an antibody-dictated specificity allows targeting toward
any tumor-associated antigen for which a monoclonal antibody
exists. Since chimeric T cell receptors based on immunoglobulin
provide T cell activation in a non-MHC-restricted manner,
mechanisms of tumor escape from T cell recognition, such as
downregulation of HLA class I molecules and defects in
antigen-processing, are bypassed. Furthermore, T cell mediated
effector functions are much more likely to result in tumor cell
lysis than humoral immune responses alone.
Genetic engineering of CTL redirected for CD30, CD20 and
CD19-specific target cell recognition has been achieved. Approaches are in the process of being translated to the
clinic, including Texas Children’s Hospital (Baylor College of
Medicine).
These CTL are
capable of mediating a variety of CD30, CD20-and CD19-specific
anti-lymphoma effector functions including cytolytic activity
against lymphoma cells, secretion of Th1 cytokines and CTL
proliferation in the presence of stimulating tumor cells.
The introduction of immunotherapeutic T cell strategies such as
the adoptive transfer of EBV-specific CTL has improved the
outcome of PTLD especially among stem cell transplant
recipients. After encouraging results were obtained in the PTLD
setting, the effect of T cell therapy on other EBV-associated
lymphomas such as Hodgkin disease and non-Hodgkin Lymphoma are
now being evaluated. The first results in Hodgkin patients are
promising but indicate that more potent strategies to stimulate
and expand T cells with tumor-specific antigens are required. In
addition, genetic modification of tumor-specific CTLs might be
needed to overcome the immune evasion strategies employed by the
tumor cells.
Catherine Bollard, M.D., is a pediatric oncologist/hematologist
and member of the
Bone Marrow Transplant Team at Texas Children’s Cancer Center and assistant professor of
pediatrics at Baylor College of Medicine. Dr. Bollard's research
interests involve using cytotoxic T cells (CTL) for viral and
malignant diseases. She is a principal investigator on two
clinical trials assessing the safety of adoptively transferred
donor-derived virus-specific CTL for the prophylaxis and
treatment of CMV and adenoviral infection post-allogeneic stem
cell transplant. She is also evaluating the efficacy of
tumor-specific CTL in patients with relapsed EBV positive
Hodgkin's disease and non-Hodgkin's Lymphoma.
Bollard CM, Huls MH, Buza E, Weiss H,
Torrano V, Gresik MV, Chang J, Gee A, Gottschalk SM, Carrum G,
Brenner MK, Rooney CM, Heslop HE. Administration of latent
membrane protein 2-specific cytotoxic T lymphocytes to patients
with relapsed Epstein-Barr virus-positive lymphoma. Clin
Lymphoma Myeloma. 2006 Jan;6(4):342-7.
Bollard CM, Straathof KC, Huls MH, Lacuesta KC, Brenner
MK, Rooney CM, Heslop HE. “The use of EBV-specific Cytotoxtic T
cells for EBV+ve Hodgkin Disease”.
J Exp Medicine, 2004 Dec 20;200(12):1623-33.
Karin C Straathof, Catherine M Bollard, Uday R Popat M
Helen Huls, Terisita Lopez, M Craig Morriss, Adrian P Gee, Heidi
V Russell, Malcolm K Brenner, Cliona M Rooney and Helen E Heslop.
“Virus Specific T cells as Treatment for Nasopharyngeal
Carcinoma” Blood, 2005 Mar 1;105(5):1898-904.
CM Bollard, I Kuehnle, A Leen, CM Rooney and HE Heslop.
“CTL Therapy for Viral Infections Post Stem Cell Transplant”
Biol Blood and Marrow Transplant;10 (3) 143-155,2004
KM Straathof, CM Bollard, CM Rooney, HE Heslop.
Immunotherapy for EBV associated cancers in children. The
Oncologist. 8:83-98, 2003
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