Posttransplant lymphoproliferative disease (PTLD) after lung transplantation occurs due to immunosuppressant therapy which limits antiviral host immunity and permits Epstein-Barr viral (EBV) replication and transformation of B cells. Mechanistically, EBV survives due to latency, escape from cytotoxic T cell responses, and downregulation of host immunity to EBV. Clinical presentation of EBV may occur within the lung allograft early posttransplantation or later onset which is more likely to be disseminated. Improvements in monitoring through EBV viral load have provided a means of earlier detection; yet, sensitivity and specificity of EBV load monitoring after lung transplantation may require further optimization. Once PTLD develops, staging and tissue diagnosis are essential to appropriate histopathological classification, prognosis, and guidance for therapy. The overall paradigm to treat PTLD has evolved over the past several years and depends upon assessment of risk such as EBV-naïve status, clinical presentation, and stage and sites of disease. In general, clinical practice involves reduction in immunosuppression, anti-CD20 biologic therapy, and/or use of plasma cell inhibition, followed by chemotherapy for refractory PTLD. This paper focuses upon the immunobiology of EBV and PTLD, as well as the clinical presentation, diagnosis, prognosis, and emerging treatments for PTLD after lung transplantation.
After lung transplantation, the allograft recipient is typically prescribed immunosuppressant therapy to inhibit adaptive immunity and cellular rejection, thus concurrently limiting innate and antiviral host response. The presence of Epstein Barr virus (EBV) affects 90% of the world’s population, with immunity to EBV present in the majority of adults [
In general, PTLD occurs after EBV infection of the nasopharynx and epithelial cells, with subsequent B cell transformation due to altered host immunity after transplantation. Initial EBV infection results in a cellular program aimed at viral production through ultimately lytic infection of tonsillar B cells and establishment of a latent infection which is a life-long one. During type III latency, a period of growth and survival of infected B cells, genes expressed include Epstein Barr nuclear antigens (EBNAs 1-3C), latent membrane proteins (LMPs 1-2B), and nuclear RNAs (EBERs). Subsequently, during type II latency, LMP 1 and LMP 2 provide differentiation within germinal centers, through CD40, a common pathway for T helper signaling of B cells. Lastly, during type I latency, no genes are expressed, thus evading cytotoxic T cell responses [
Host immunity to EBV is inhibited by EBV-derived cytokines which downregulate cytotoxic T cell responses and induction of anti-apoptosis pathways which prevent cell death by EBV latency proteins. During lytic infection, viral interleukin-10 (vIL-10), bearing homology to human IL-10, reduces IL-12 and
This proposed model of pathogenesis shows EBV infection of B cells (1), concurrent immunosuppression of plasmacytoid dendritic cells, PDCs, (2), net increase in IL-10, release of
Antiviral responses are predominantly mediated by cytotoxic T cells, primed by prior immunological stimuli, with specific antigen-specific memory. Mifsud and colleagues described EBV-specific CD8+ T cells in a longitudinal study cohort of lung transplant recipients, focusing upon an HLA-B8 restricted cohort with reactivity directed towards epitope FLRGRAYGL on the EBV protein EBNA3A. The authors found the frequency of EBV-specific T cells in immunosuppressed lung transplant patients to be 4-5-fold greater compared to healthy controls. Although ex vivo stimulation of EBV specific T cells revealed alloreactive responses,
Identifiable risk factors for PTLD in lung and solid organ transplantation may be related to multiple factors unique to the type of organ transplanted, as the rate of PTLD increases from the lowest in kidney, intermediate for pancreas, liver, heart, and lung, to highest in small intestine transplantation [
Early means of testing for primary EBV infection and the immunological program associated with current or past infection relied upon serological sampling and an understanding of the phases of EBV infection. Sequentially, IgM antibodies to EBV viral capsid and early antigen rise and fall within the first month, followed by antibodies to EBNA and the sustained IgG antibody response to viral capsid antigen [
Recognition of predisposing risk factors for PTLD and the routine testing of EBV viral load after lung transplantation have contributed towards earlier diagnosis and have likely altered overall mortality. The clinical presentation of PTLD may also depend upon time from transplantation to diagnosis of PTLD, with earlier disease occurring within the first year more likely to present within the thorax including allograft parenchyma or mediastinal lymph nodes [
Clinical symptoms of PTLD relate to the systemic effects of lymphoproliferation and may include lymph gland tenderness, fever and sweats, fatigue, sinus pain, cough, headache, intestinal pain, and neurological deficits. Examination of patients with PTLD may reveal enlarged lymph nodes or nodules, tonsillar prominence, hepatosplenomegaly, intestinal obstruction, and neurologic deficits.
Since PTLD presents with systemic manifestations, laboratory testing may provide additional insight into localization of PTLD. Testing of complete CBC, chemistries, liver function tests, LDH, uric acid, and hemoccult positivity may reveal systemic anemia, involvement of the reticuloendothelial system of the liver and spleen, tumor lysis from rapid cell growth and turnover, and GI bleeding from neoplastic lesions. Concurrent viral infection furthers host immunosuppression and may be a cofactor in PTLD tumor growth. Thus, assessment of quantitative CMV viral load should be routinely performed. EBV serology is an insensitive and nonspecific test for PTLD due to altered host antibody responses and may be difficult to interpret as well after transfusion of red blood cell or plasma products. Quantitative measurement of EBV viral load used for surveillance monitoring and indication of systemic disease may be limited by insensitivity and lack of specificity but, nevertheless, remain consistent within individual laboratory testing [
Since PTLD is likely to present within the thorax, chest X-ray (CXR) may reveal parenchymal lesions, infiltrates, and nodules, followed by CT scan of the chest, abdomen, and pelvis, to assess lymphadenopathy. Concurrent imaging of the head and neck may be performed given PTLD predilection for the CNS and cervical lymph nodes. In recipients of solid organ transplant, pulmonary nodules as noted on CXR and CT scanning in EBV seronegative patients and lung transplant recipients proved to be associated with PTLD (odds ratios 21.7 and 36.6, resp.) [
In terms of localization of PTLD, intrathoracic location is present in >70% of lung transplant recipients [
Current standard diagnosis of PTLD requires a tissue diagnosis, evaluation of histopathological morphology, immunophenotype, presence of clonality, and testing of tissue for EBV using in situ hybridization for EBER. Categories of PTLD as categorized by the WHO classification of tumors of hematopoietic and lymphoid tissues list early lesions, polymorphic PTLD, monomorphic PTLD including B and T cell tumors, and classical Hodgkins disease. Early lesions are considered benign and include infectious mononucleosis-like and plasmacytic hyperplasia. Polymorphic PTLD demonstrates mature lymphocytes and polyclonal or monoclonal B cells for the majority, while monomorphic lesions are comprised of clonal B lymphocytes. B cell neoplasms may include diffuse large B cell lymphoma (DLBCL), Burkitt’s lymphoma, plasma cell myeloma, and plasmacytoma-like lesion, while T cell neoplasms may include peripheral T cell lymphoma and hepatosplenic T cell lymphoma [
Recent consensus statements conclude that classification according to WHO categories describes histopathological features alone and therefore requires a complement of additional studies to characterize immunohistochemistry, testing for CD20 positivity, clonality, and in situ studies demonstrating a clear EBV-related neoplasm, as related to the clinical context such local or disseminated disease [
In addition to histopathology and ancillary testing to provide insight into subsequent focused therapy, advances in molecular and genetic analyses define additional features of PTLD. As reviewed by Ibrahim and colleagues, distinct genetic rearrangement, amplification, and somatic hypermutation involving point mutations of the immunoglobulin (Ig) variable region are associated with BCL6, BCL2, p53, and PAX5 genes in PTLD. Gain or loss of chromosomal material is frequently identified in PTLD such as DLBCL, for example, a gain of chromosomes 5p and 11p and deletions of 12p, 4p, 4q, 12q, 17p, and 18q.
Deletions of 4q, 17q, and Xp are unique to PTLD as contrasted to lymphomas in immunocompetent patients. Interestingly, in PTLD-related DLBCLs, a lack of del(13q14.3) which is hypothesized to play a role in immune surveillance avoidance may reflect genetic alterations in immunosuppressed patients [
In general, poor performance status, wide-spread disease, CNS involvement, monoclonality, and T-, NK-, or EBV-negative PTLD are associated with less favorable outcome [
Whether PTLD results from donor or recipient origin may also play a role in prognosis, as Olagne and colleagues documented in a large cohort of kidney transplant patients, noting survival of 68% at 5 years in PTLD of recipient origin, compared to 85% survival in PTLD of donor origin, although this did not attain statistical significance [
Data from individual lung transplant centers’ experiences cite a mortality figure of 30%–60% due to PTLD [
Summary of outcomes of lung transplant patients with PTLD from US and European lung transplant centers.
Study/year/ |
#PTLD total | PTLD incidence | Time to Dx PTLD after transplant | Sites of presentation | Pathology | Treatment | Survival |
---|---|---|---|---|---|---|---|
Armitage et al. 1991, [ |
5/87 | 7.9% | 4 months | Lung, mediastinum, GI tract | NA | RI, surgical resection, CH | 36% mortality <1 year, |
Aris et al. 1996, [ |
6/94 | 6.4% | 4.5 months | Mediastinal mass, tonsil enlargement, lung nodules, bowel obstruction, skin nodules | Polymorphic B cell hyperplasia and lymphoma, monoclonal | RI, surgical excision of mediastinal mass, CH | Average survival ~11 months |
Wigle et al. 2001, [ |
12/242 | 5.0% | 17.6 months | Lung, mediastinum, abdomen | NA | RI, CH | 1 year survival rate of 58% |
Paranjothi et al. 2001, [ |
30/494 | 6.1% | 402 days | Lung, mediastinal lymph nodes, liver, testicle, GI tract, bone marrow, skin, ovary | Monomorphic lymphoma, polymorphic lymphoma | RI, surgical resection, rituximab, CH | Median survival 1.0 ± 1.5 years |
Ramalingam et al. 2002, [ |
8/244 | 3.3% | 12 months | Lung, small bowel, colon, skin | Monomorphic lymphoma, polymorphic lymphoma | RI, rituximab, interferon, CH, XRT | 5/8 patients died of complications from PTLD |
Reams et al. 2003, [ |
10/400 | 2.5% | 343 days | Lung, small bowel, liver, periaortic adenopathy, tongue, supraclavicular | Monomorphic lymphoma, polymorphic lymphoma, T cell lymphoma | RI, rituximab, surgical resection, CH, XRT | 5/10 survival over 1992–2002 time period |
Tsai et al. 2008, [ |
17/206 | 8.3% | NA | Lung, extranodal | Monomorphic lymphoma | RI, rituximab, surgical resection, CH, XRT | Median survival 12 months |
Knoop et al. 2006, [ |
17/224 |
8.0% | 68 months | Lung, mediastinum, cervical nodes, liver, bone marrow | Monomorphic lymphoma | RI, rituximab | 4/6 complete remission with relapse free survival of 34 months |
Baldanti et al. 2011, [ |
5/111 | 4.5% | 270 days | Lung, mediastinum | Hodgkins, monomorphic lymphoma | RI, rituximab, CH | 4/5 have died |
Wudhikarn et al. 2010, [ |
29/639 | 5.0% | 40 months | Lung, GI tract, intraabdominal lymph nodes, CNS, bone marrow | Monomorphic lymphoma, Burkitt’s, lymphoid granulomatosis, anaplastic large cell | RI, rituximab, surgical resection, CH, XRT | Median survival 10 months |
Kremer et al. 2012, [ |
35/705 | 4.8% | 38 months | Lung, GI tract, nasopharynx, skin, CNS, kidney, liver | Polymorphic lymphoma, monomorphic lymphoma | RI, rituximab, CH, XRT | Median survival 18.5 months |
*This study examined 6/17 lung transplant patients with PTLD who received rituximab as a first-line therapy.
RI: reduced immunosuppression; CH: chemotherapy, XRT: radiation therapy.
Essential steps in preventing PTLD include a combination of strategies, including identification of high-risk EBV-naïve patients and routine surveillance for EBV viral load, antiviral prophylaxis, and reduction in immunosuppression in appropriate high-risk patients who have seroconverted their EBV status and have detectable and/or rising EBV quantitative PCR. Prior to transplantation at the time of evaluation, patients at risk for primary EBV or CMV infection should be identified, and appropriate serological testing should be performed. After transplantation, patients whose immunosuppression is being escalated, or who have received T cell depleting therapies, should be monitored as well. Antiviral prophylaxis is routinely given after lung transplantation, primarily for HSV and CMV, but likely has added chemoprophylaxis for EBV. Malouf and colleagues described a significantly diminished rate of PTLD in lung transplant recipients after elimination of induction therapy and institution of viral prophylaxis in EBV seronegative patients, decreasing from 4.2% to 0.76% [
Although limited data exists in lung transplantation regarding the prophylactic reduction of immunosuppression in patients with presumptive PTLD, studies have shown that under unique circumstances, immunosuppression may be reduced safely without risk for acute or chronic allograft dysfunction. Bakker and colleagues followed EBV viral loads in a cohort of lung transplant patients on average 4 years posttransplant, and reduced immunosuppression after finding evidence of EBV reactivation, with no acute rejection, acceleration of BOS, or poorer survival. The authors hypothesized that EBV viral loads in this setting late after transplant indicated the net state of immunosuppression [
The overall approach to treatment of PTLD will vary according to the individual risk, clinical presentation, and stage and sites of disease, as depicted in Figure
This algorithm proposes routine surveillance of high-risk patients to enable diagnosis at an early stage. Starting with EBV viral load monitoring, patients who manifest elevated levels with symptoms would progress to imaging studies and biopsy of enlarged lymph nodes or nodules. Identification of CD20 lesion positivity, cytogenetics, immunostaining for LMP and EBER, and assessment of monoclonal or polyclonal proliferation can focus further therapy. In localized disease, reduction of immunosuppression or surgery may be sufficient to control disease, while rituximab may be given concurrently. High-grade extensive disease may require chemotherapy, bortezomib, or EBV-specific cytotoxic T lymphocytes if available. From [
Chemotherapy may be required for patients with disseminated disease, clinical progression on rituximab, or non-B cell PTLD. Regimens used by individual lung transplant centers include a combination of the following chemotherapeutic agents: cyclophosphamide, adriamycin, vincristine, etoposide, and prednisone [
Promising therapies are emerging in the treatment of PTLD, such as EBV-specific cytotoxic T cell therapy, which as yet is still in experimental phase. Cytotoxic T lymphocytes (CTLs) from healthy, EBV-experienced donors are adoptively transferred in order to better respond to EBV-positive tumor cells in immunosuppressed solid organ transplant patients. Optimally, HLA-matched allo-CTLs provide better results and may be stored in a frozen bank after being obtained from donors. This therapy was applied to solid organ transplant patients with advanced PTLD in a phase II clinical trial and resulted in
Lastly, patients who survive PTLD and have chronic lung allograft dysfuntion or experienced allograft dysfunction due to drug toxicity, may be considerd for retransplantation. In a review of solid organ transplant recipients who survived PTLD and underwent retransplant, time from PTLD to retransplant was greater than 1 year in 75% of patients, with median number of days 862 in the 9 lung transplant recipients who were part of the analysis. The majority of lung transplant patients in this analysis were pediatric. At the time of analysis, 55.6% of the lung retransplant patients were alive with a mean followup of 776 ± 249 days [
As collective experience grows with management of PTLD after lung transplantation, optimal care, monitoring of high-risk recipients, and treatment continue to be refined. Additional monitoring tools may include soluble CD30 which has been associated with lymphoproliferative disorders [