Prevalence and association of human papillomavirus 16, Epstein-Barr virus, herpes simplex virus-1 and cytomegalovirus infection with human esophageal carcinoma: a case-control study

Recent research shows esophageal carcinoma (EC) as the ninth most common malignancy in the world. The association of viral infection and EC has been reported in the last 30 years. However, geographic variation in infection rates and the key mechanisms of the viral action have yet to be resolved. This study aimed to determine the prevalence and association of human papillomavirus 16 (HPV-16), herpes simplex virus 1 (HSV-1), Epstein-Barr virus (EBV) and cytomegalovirus (CMV) infection in the etiology of EC in the area of Shantou, Guangdong, China. Nested PCR was used to detect viral DNA in the mucosa of 70 cases of EC and in paracancerous tissues, as well as 100 cases of normal esophagus mucosa. Data were analyzed by χ2 test, Fisher's exact test and bivariate correlation analysis. The infection rates of HPV-16, HSV-1 and EBV were 40.0, 30.0 and 30.0%, respectively, in EC mucosa, and were significantly higher than those in normal mucosa. However, no CMV DNA was detected in either EC or normal mucosa. HPV-16 or EBV infection was mainly detected in EC patients 48-58 years old, and the infection rate was positively associated with pathological grade of EC (P<0.05). Tobacco smoking and alcohol consuption were high risk factors for HPV-16 infection for male patients [odds ratio (OR), 5.9; 95% confidence interval (CI), 1.4-24.6; OR = 3.8; 95% CI, 1.1-13.8]. Rates of infection with a mixture of these 3 viruses were all more than 10.0% in cancerous mucosa and closely related to the pathological grade of EC (P = 0.001). Infection with HPV-16, HSV-1 or EBV may be an important etiological factor in EC.

Strategies to prevent EBV reactivation and posttransplant lymphoproliferative disorders (PTLD) after allogeneic stem cell transplantation in high-risk patients

Epstein-Barr virus (EBV)-associated postallogeneic stem cell transplantation (SCT) lymphoproliferative disorder (PTLD) is often life threatening. The risk of EBV reactivation is highest in older patients, T cell-depleted SCT (in vivo or vitro), and in unrelated or mismatched SCT. Cumulative numbers of patients with EBV reactivation and PTLD are rising as more patients at high risk for EBV reactivation and PTLD are receiving allo-SCT. Novel but easily applicable strategies are needed to prevent EBV reactivation and PTLD to serve the needs of the increasingly enlarging population of high-risk SCT recipients across the globe.

Epstein-Barr virus infection as a cause of cervical lymphadenopathy in children

OBJECTIVE

Cervical lymphadenopathy is a common pediatric problem; reactive hyperplasia, specific infective agents, and malignancy are mainly the differential diagnosis. The aim of our study was to detect the prevalence of Epstein-Barr virus infection among children who complained of cervical lymphadenopathy and also to evaluate the clinical manifestations of the disease in pediatric patients.

METHODS

One hundred and sixty children presented with cervical lymphadenopathy were subjected to Epstein-Barr Virus (EBV) serology testing. Cases that showed positivity to heterophile antibody test, and/or EBV-specific antibodies; IgM against viral capsid antigen (VCA-IgM) and IgG against viral capsid antigen (VCA-IgG) were evaluated clinically for manifestations of the disease.

RESULTS

Twenty-four cases (15%) showed positivity to EBV serology, all of them had posterior cervical lymph nodes enlargement, 70.8% had fever, 66.6% had tonsillo-pharyngitis, 58.3% had splenomegaly, 25% had hepatomegaly, 41.6% had generalized lymphadenopathy, while skin rash was detected in 12.5%, and both palatal petechiae and palpebral edema were detected in 8.3%.

CONCLUSIONS

EBV infection is not a rare cause of cervical lymphadenopathy in children. Posterior cervical lymphadenopathy in pediatric age group may represent a password for suspicion of EBV infection, while other clinical manifestations of the disease may include hepato-splenomegaly, skin rash, palpebral edema and palatal petechiae.

Frequency of blood-borne viral infections among leukemic patients in central Iraq

OBJECTIVE

To determine the prevalence of hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human immunodeficiency virus (HIV) and other epidemiological criteria among leukemic patients to establish basic knowledge for future leukemic patients care.

METHODS

This cross-sectional study was carried out between February 2006 and June 2008 in the Children's Central Teaching Hospital and Medical City Teaching Hospital in Baghdad, Iraq. A total of 641 blood samples (291 samples from leukemic patients and 350 samples from controls) were collected and the sera were tested for the presence of HBV, HCV, CMV, EBV, and HIV serological markers.

RESULTS

A significantly higher prevalence of hepatitis B surface antigen (HBsAg) was detected among leukemic patients (32.3%) than controls (2.3%). The seroprevalence of anti-HBs was 29.9% among patients, and 20.6% among controls. This difference was also found to be statistically significant. A significantly higher prevalence of anti-HCV antibodies among leukemic patients (3.4%) than controls (0.3%) was also detected. A higher prevalence of IgG and IgM markers specific for CMV (96.2% and 12% for patients; 91.6% and 8% for controls), and for EBV (88.3% and 26.5% for patients; 75.1% and 13.4% for controls), were detected among leukemic patients than controls, while none of the patients and controls were positive for HIV I and II markers.

CONCLUSION

We conclude that HBV, HCV, CMV, and EBV infections are more prevalent among leukemic patients. There was an increase in the seropositivity rates of HCV, CMV, and EBV infections with increasing ages of leukemic patients. The male leukemic patients were more exposed to HBV, HCV, and EBV infections than females.

Hodgkin lymphoma in Pakistan: an analysis of subtypes and their correlation with Epstein Barr virus

The epidemiology of Hodgkin lymphoma (HL) shows a wide geographic variation with regard to age, gender, histological subtypes and their association with Epstein-Barr virus. The proportion of EBV positive cases appears higher in developing than in developed countries. EBV is a common infection in Pakistan due to poor socioeconomic conditions, but reports regarding HL subtypes have been rather selective. Our aims were to establish the relative frequencies of the five subtypes of Hodgkin lymphoma, to determine their associations with Epstein-Barr virus, and finally to establish whether such association follows patterns seen in developing or developed countries. Among 100 cases, the male: female ratio was 4.5:1, with an age range of 4-82 years and an average of 26.6 years. Similar to the subtype distribution in developing countries, mixed cellularity was the commonest 57%, followed by nodular sclerosis 35%, lymphocyte rich 6% and nodular lymphocyte predominant 2%. EBV-LMP1 staining was demonstrated in 41/57 (71%) of the mixed cellularity and the 19/35 (54.2%) of nodular sclerosis subtypes. All 6 cases of lymphocyte rich and 2 cases of nodular lymphocyte predominant were negative for EBV-LMP 1. Speculation about prognostic effects of EBV infection on the course of HL are tempting. Thus the EBV-positive HL could in the future prove to be an excellent candidate for targeted cellular immunotherapy.

Epstein-Barr virus-associated diffuse large B-cell lymphoma of the hypopharynx

PROBLEMS/OBJECTIVES

Epstein-Barr virus (EBV) is commonly associated with nasopharyngeal carcinoma and Burkitt's lymphoma, but association with hypopharyngeal and laryngeal tumours is rare. To the best of our knowledge, this is the first case report of an EBV-associated diffuse large B-cell lymphoma (DLBCL) of the hypopharynx.

METHODOLOGY

A 63-year-old male patient suffering from chronic lymphocytic leukemia presented with swallowing disorders and a sore throat. Panendoscopy with laser surgical resection of tissue specimens was performed.

RESULTS

Immunohistochemical and molecular genetic diagnostics, including EBV-encoded small RNA in situ hybridization, confirmed the diagnosis of an EBV-associated DLBCL of the hypopharynx. Ten weeks after the diagnosis, the patient died of disease related to multiple complications.

CONCLUSIONS

We hypothesize that the EBV infection was triggered by long-term immunosuppressive therapy that led secondarily to the development of a DLBCL. Otorhinolaryngologists should keep in mind that lymphomas might develop in the entire pharynx.

Prevalence of viral (HPV, EBV, HSV) infections in oral submucous fibrosis and oral cancer from India

CONCLUSION

There is a high prevalence of human papilloma viruses (HPV) in oral submucous fibrosis (OSMF) and the etiologic implication of this finding warrants further studies.

OBJECTIVE

The prevalence of oral squamous cell carcinoma (OSCC) and OSMF is high in India, and the diseases are partly attributed to high consumption of betel quid containing areca nut and tobacco. This study investigated the prevalence of HPV, herpes simplex virus (HSV), and Epstein–Barr virus (EBV) DNA in two groups of patients using betel quid with tobacco, those with OSMF (n = 12) and those with OSCC (n = 62).

METHODS

DNA was extracted from all the samples and viral genome was examined by PCR/DNA sequencing. HPV-positive samples were analyzed separately for the high-risk types HPV 16 and 18.

RESULTS

HPV DNA, HSV DNA, and EBV DNA were detected in 11 (91%), 1 (8%), and 3 (25%) of the 12 samples from patients with OSMF compared with 15 (24%), 3 (5%), and 18 (29%), respectively, from 62 patients with OSCC. HPV 16 and 18 DNA was detected in 8/12 (67%) in the OSMF group and 10/62 (16%) in the OSCC group. The difference between presence of HPV DNA in OSMF and OSCC groups was statistically significant, while the difference between HSV and EBV DNA content in OSMF and OSCC groups was insignificant.

[Epstein-Barr virus and cytomegalovirus primary infections: a comparative study in 52 immunocompetent adults]

OBJECTIVE

The objective of this study was to compare epidemiological, clinical, and biological data of Epstein-Barr virus (EBV) and cytomegalovirus (CMV) primary infections in immunocompetent adults, admitted in the infectious disease department of the Reims Teaching Hospital between 2000 and 2005.

PATIENTS AND METHODS

Inclusion criteria were the presence of anti-VCA IgM antibodies or the presence of CMV specific IgM antibodies and the absence of any other positive serology. Differences in reported percentage were compared with a Khi(2) test or Fischer's exact test, when appropriate. Continuous variables were compared with the Mann-Whitney Test.

RESULTS

There were no significant changes over the years in the numbers of EBV (n=32) and CMV (n=20) primary infections. The patient's mean age was 22.7 years (14-48 years) in EBV primary infections and 38.6 years (13-66 years) in CMV primary infections (P<0.01). The clinical variables significantly associated with primary EBV infection were sore throat and cervical lymphadenopathy (P<0.01). Arthromyalgia and respiratory manifestations were less frequent in EBV primary infection (P<0.01). The biological variables significantly associated with EBV primary infection were a marked alanine aminotransferase elevation and a marked lymphocytosis with atypical lymphocytes (P<0.001). Thrombopenia was less frequently associated with EBV primary infection (P<0.001).

CONCLUSION

Clinical and biological presentations of EBV and CMV primary infections were similar. The simultaneous serologic diagnosis of these two infections remains necessary to provide a specific diagnosis, for the most efficient patient care.

Prospective evaluation of epstein-barr virus reactivation after stem cell transplantation: association with monoclonal gammopathy

Epstein-Barr Virus (EBV) reactivation and EBV-related post-transplant lymphoproliferative disease (PTLD) have emerged as a severe complication after stem cell transplantation (SCT). We prospectively evaluated 104 consecutive patients receiving SCT either autologous or allogeneic. Fifty-two patients (50%) presented EBV DNA-emia and five of them developed PTLD proven or probable. PTLD rate was 9.6% among patients with EBV DNA-emia. One patient developed PTLD without EBV DNA-emia (0.96%). Overall PTLD incidence was 5.7%. No PTLD developed after autologous SCT. EBV DNA-emia was significantly more frequent after allogeneic than autologous SCT (60.7% vs 17.4%, p = 0.0002). At EBV reactivation, serum protein electrophoresis and immunofixation were assessed. Global incidence of γ-peak after allogeneic SCT with EBV reactivation was 65.3% (32/49 patients) and monoclonal gammopathy (MG) was identified in 23/28 evaluable patients (82%). All patients with PTLD developed γ-peak and in five of them MG was identified. MG is consistently associated with EBV DNA-emia and may help identification of progression to PTLD after allogeneic SCT.

Epstein-Barr virus, cytomegalovirus, and infectious mononucleosis

Infectious mononucleosis (IM) is a clinical syndrome that is common in adolescents and young adults and is characterized by fever, lymphadenopathy, pharyngitis, and fatigue. IM is most commonly associated with Epstein-Barr virus (EBV) infection in which case laboratory findings include a lymphocytosis with an elevated number of atypical lymphocytes seen on peripheral smear and a heterophile or EBV-specific antibody response. Approximately 10% of those with IM will not be acutely infected with EBV. Many of these individuals will have their symptoms attributed to cytomegalovirus (CMV) infection. This chapter reviews the history, diagnosis, clinical management, and potential complications of both EBV- and CMV-associated IM in adolescents and young adults.

The prevalence of Epstein-Barr virus infection in different types and sites of lymphomas

To analyze the association of several types of malignant lymphomas in different anatomical sites with the Epstein-Barr virus (EBV) infection status, 127 cases of formalin-fixed paraffin-embedded samples of malignant lymphomas were investigated with in situ hybridization detecting EBV-encoded small RNA (EBER) in tumor cells. Forty-six out of 108 non-Hodgkin lymphoma (NHL) cases were positive for EBER (42.6%). The EBER-positivity rate of NHL in the nasal cavity and nasopharynx (35/60 cases, 58.3%) was higher than that of NHL in stomach (9/30 cases, 30%) and in the superficial lymph nodes (2/18 cases, 11.1%) (P<0.05). The EBER-positivity rate of Hodgkin lymphoma in the superficial lymph nodes was 26.3% (5/19 cases). These findings suggest that the EBV-positivity rate in lymphomas is related to their histological types and locations.

Lower respiratory tract viral infections in hospitalized adult patients

AIM

The epidemiology of lower respiratory tract (LRT) viral infections in adults is probably underestimated and the high frequency of multiple viral infections complicates the evaluation of the possible role of the single viruses. The aim of this study was to investigate the clinical epidemiology and impact of respiratory viral pathogens, in particular of those singularly detected, in bronchoalveolar lavage (BAL) specimens from hospitalized adult patients.

METHODS

A panel for the detection of 16 respiratory viruses was used to prospectively evaluate 324 consecutive specimens obtained from 219 patients over a full-year period.

RESULTS

Two-hundred-twenty-one specimens (68.2%) were positive for at least one virus, 119/324 (36.7%) to a single viral agent. The most commonly detected viruses were herpesviruses HHV-7 (26.2%), human cytomegalo-virus (HCMV, 22.2%), HHV-6 (19.8%), EBV (12.7%), enteroviruses and rhinoviruses (both 11.7%), parainfluenza viruses (4.9 %), and metapneumovirus (4.0%). Human cytomegalo-virus was significantly more prevalent as single viral pathogen with a viral load >105 copies/ml associated to pneumonia in solid organ transplant recipients. Other viral pathogens might account for some cases of pneumonia or respiratory insufficiency, although multiple infections were common.

CONCLUSIONS

The use of a comprehensive diagnostic panel for respiratory viral infections may be useful to clarify the epidemiology and clinical impact of viral pathogens in hospitalized adult patients. The occurrence of multiple infections is a common finding and results should be interpreted taking into account the clinical context as well as viral load and the biological characteristics of each virus.

Epstein – Barr viral load, interleukin-6 and interleukin-10 levels in post-transplant lymphoproliferative disease: A nested case – control study in a renal transplant cohort

The possible correlation among Epstein-Barr virus (EBV) load, interleukin-6 (IL-6) and interleukin-10 (IL-10) levels has become an attractive issue and can provide a useful tool for diagnosis and monitoring of patients at risk for post-transplant lymphoproliferative disease (PTLD) development. At the time of diagnosis of PTLD, 11 patients were prospectively enrolled and 55 nested controls were selected from a 1800 renal transplant cohort. Real-time polymerase chain reaction (PCR) was used to quantify EBV load in peripheral blood mononuclear cells (PBMC). Serum IL-6 and IL-10 levels were determined using an enzyme-linked immunosorbent assay (ELISA). The median EBV load of PTLD cases was 17400 copies/10(6) PBMC, statistically different from controls (P=0.001). The median IL-6 level of PTLD cases was not different from controls (P=0.079). However, median IL-10 levels showed a significant difference in both groups (P < or = 0.001). The receiver-operating characteristic (ROC) curve analysis was applied to estimate the IL-10 cut-off value predictive of PTLD development. We found that 73.5 pg/ml has high sensitivity (1.00) and specificity (0.85). Also, Pearson's analysis showed a strong correlation between EBV load and serum IL-10 concentration (P < or = 0.001). This nested case-control study demonstrates that EBV load at diagnosis of PTLD correlates with IL-10 levels, and that monitoring of IL-10 can provide a less expensive and less time-consuming tool for PTLD diagnosis and close follow-up of patients at risk. Furthermore, we were able to define a cut-off value of IL-10 mostly predictive of PTLD development in this cohort. Our data suggest that serial measurements prior to PTLD development must be carried out to validate our hypothesis.

The extent of genetic diversity of Epstein-Barr virus and its geographic and disease patterns: a need for reappraisal

Epstein-Barr virus (EBV) is a ubiquitous, gamma-1 lymphotrophic virus etiologically linked to nasopharyngeal carcinoma (NPC), endemic to Southern China, and Burkitt lymphoma (BL), endemic to equatorial Africa, both of which are rare elsewhere in the world. Why EBV is associated with different malignancies in different geographic regions remains puzzling and may be related to EBV genotypic variability through specific disease and geographic associations. We review the literature on sequence variation in EBV genes, focusing on LMP-1, EBNA-1, and BZLF-1 and their distribution by geography and disease. Given the limitations of current studies, definitive conclusions regarding the link between EBV genotypes, disease and geography are not possible. We suggest that the true extent of EBV diversity is likely to be greater than is currently recognized. Additional studies conducted in carefully selected populations, that are sufficiently powered to provide robust estimates, and that utilize testing approaches that permit full characterization of viral diversity are needed to further our understanding of patterns of EBV genetic variation and their association with malignancies in different regions.

Epstein – Barr virus infection is not the sole cause of high prevalence for Hodgkin's lymphoma in Saudi Arabia

The age-adjusted incidence of Hodgkin's lymphoma (HL) is markedly higher in Saudi Arabia than in the USA, and accounts for 10.5% of all neoplasias in children aged 15 years or older in Saudi Arabia. Epstein-Barr virus (EBV) infection has been suspected to cause high HL incidence in developing countries. To investigate the role of EBV for the high frequency of HL in Saudi Arabia, we analysed 169 HLs from Saudi Arabia and 30 HLs from Europe for EBV infection by in situ hybridization with fluorescence in-conjugated EBV on tissue microarray sections. All Saudi Arabian and European HLs were analysed in one experiment under identical conditions. Unexpectedly, our data show only minor, insignificant differences in EBV infection rates between Saudi Arabian (42 out of 147 informative cases 28.6%) and European HL (nine out of 30 informative cases; 30%; P = 0.8752). Within the Saudi Arabian population, EBV infection was most frequently seen in mixed cellularity HL (52.4%). This was significantly more frequent than in nodular sclerosing HL (26.1%; P = 0.0236). EBV positivity was unrelated to patient prognosis. In conclusion, our data strongly suggest that EBV is not the main cause for the high prevalence of HL in Saudi Arabia. This would be consistent with a major role of genetic susceptibility genes for HL in these populations. The Saudi Arabian population, with high consanguinity and large families, would prove ideal for identifying HL susceptibility genes.

Herpesviruses as possible cofactors in HPV-16-related oncogenesis

Cervical carcinogenesis is a complex problem with papillomavirus widely accepted as a causative agent. Integration of a human papillomavirus (HPV) of the high-risk type into the host cell genome is one of the major contributing factors to cervical malignant transformation. In this study, the correlation of CMV, EBV, HSV-1, HSV-2, HHV-6 and HHV-7 infections with the physical status of the HPV genome in cervical cancer and precancerous cervical lesions was investigated in sixty HPV-16-positive women. Cervical secretion samples were submitted to DNA extraction and analyzed by PCR. HPV-16 DNA was confirmed in genotyping with the reverse hybridization line probe assay. Multiplex PCR with specific primers for the E2/E6 genes was used to assess the viral integration status of HPV-16. Our results show that CMV DNA was more frequently present in samples with mixed forms of HPV-16 than in the episomal form (P < 0.025). Such a correlation was also observed in the case of EBV (P < 0.005). The presence of CMV resulted in a six-fold (OR 6.069; 95% CI 1.91-19.22; P = 0.002), while EBV caused a seven-fold (OR 7.11; 95% CI 1.70-29.67; P = 0.007) increase in the risk of the integrated or mixed HPV-16 genome occurrence. Our data suggest that coinfection with herpesviruses, especially CMV and EBV, may be involved in the integration of the HPV-16 genome and may contribute to the development of cervical cancer.

[Systemic lupus erythematosus and Epstein-Barr virus]

We determined the prevalence of antibodies to Epstein-Barr virus (EBV) in 44 patients with systemic lupus erythematosus (SLE) and 44 healthy blood donors matched for sex and age as controls. Of the cases, 39 were women; mean age was 33 years. Four cases (9%) and 5 controls (11%) were positive for IgM anti-viral capsid antigen (VCA) (P = 0.9). All the cases were positive for IgG anti-VCA compared with 91% of the controls (P = 0.12). The mean immunity ratio for this antibody was 2.341 in cases and 1.873 in controls (P = 0.068). Forty (91%) cases were positive for IgG anti-EBNA1 (EB nuclear antigen1) compared with 42 (95%) controls (P = 0.6).

Clinical analysis and follow-up study of chronic active Epstein-Barr virus infection in 53 pediatric cases

BACKGROUND

Chronic active Epstein-Barr virus infection (CAEBV) has been previously reported to be sometimes associated with an aggressive clinical course. The characteristics of CAEBV in Mainland Chinese pediatric patients are largely unreported. The main aims of this survey were to recognize the clinical features of CAEBV in children and to explore its diagnostic criteria and risk factors.

METHODS

A retrospective study was performed on 53 pediatric patients (36 boys and 17 girls) with CAEBV who were admitted to Beijing Children's Hospital between 2003 and 2007. All their medical records were reviewed and analyzed. For each patient, demographic, clinical, laboratory data and outcome were collected. Independent-samples t test was used for statistical analysis.

RESULTS

The age at onset of CAEBV was from 2 months to 14.6 years (mean (5.3+/-3.3) years). At the time of onset, 43.4% patients had an infectious mononucleosis-like symptom. Most patients exhibited intermittent fever (92.5%, 49/53), hepatomegaly (81.1%, 43/53) and splenomegaly (77.4%, 41/53). Life-threatening complications including hemophagocytic syndrome (24.5%, 13/53), interstitial pneumonia (24.5%, 13/53), hepatic failure (15.1%, 8/53) and malignant lymphoma (11.3%, 6/53) were also observed. The serum EBV DNA level in 23 patients with CAEBV was in the range of 5.05 x 10(2)-4.60 x 10(6) copies/ml with a mean value of 10(3.7) copies/ml. Many patients with CAEBV generally had continuous symptoms during the observational period. Eleven out of 42 patients (26.2%) died 7 months to 3 years after onset. Deceased patients were more likely to have had lower platelet counts and albumin levels than the living patients (P<0.05 for all comparisons).

CONCLUSIONS

The study reveals that CAEBV in Chinese pediatric patients has a severe clinical course and prognosis is poor. Thrombocytopenia and decreases in albumin might potentially be risk factors for a poor prognosis. EBV loads should be measured and tissue should be stained on hybridization probes for EBV-encoded small RNA (EBER) if a patient presents with the known symptoms of CAEBV.

Epstein-Barr virus detection in invasive and pre-invasive lesions of the uterine cervix

In the present study, our aim was to investigate whether EBV DNA could be found in association with invasive and pre-invasive cervical cancer lesions. We hypothesize that EBV is not merely a commensal agent when present in malignant cervical lesions. DNA was extracted from cervical scrapings followed by nested PCR-based amplification. The patients were 66 women with high grade cervical intraepithelial neoplasia and 14 women with invasive cervical cancer. The control group consisted of 89 women with a normal Pap smear and colposcopy as well as a negative HPV DNA test. Analysis of our results, in conjunction with the work of other authors, leads us to propose that EBV is not merely a commensal agent when present in malignant cervical lesions. The presence of DNA from EBV is significantly associated with cervical cancer.

Treatment for Epstein-Barr virus-associated PTLD

The association between Epstein-Barr virus (EBV) and post-transplant lymphoproliferative disease (PTLD) has been recognized since the early days of transplantation. The major pathogenetic defect is the insufficient EBV-specific cytotoxic T-cell control of EBV-driven B-cell proliferations. Despite this understanding, PTLD remains a significant cause of morbidity and mortality for transplant recipients. Determining the right therapy or therapies for any given patient with PTLD remains a major clinical problem. Productive areas of investigation include: identifying who will benefit from reduction of immunosuppression only; improving methods to predict those at highest risk of PTLD; developing safe and effective pre-emptive therapies; identifying who will benefit from rituximab; and developing more effective, less toxic therapies for resistant or aggressive disease. Obstacles that exist are heterogeneity of disease and patient populations, and divergent approaches to immunosuppression and therapeutic interventions. Greater collaboration is needed between infectious disease specialists, pathologists, transplant physicians and oncologists to overcome problems and develop agreed disease definitions and interventions that can be tested in large, prospective multicentre trials.