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While pre-emptive rituximab therapy for EBV has substantially reduced the incidence of post-transplant lymphoproliferative disorder, following allogeneic haematopoietic SCT (HSCT), cytomegalovirus (CMV) and adenovirus (ADV) still contribute to significant morbidity and mortality after HSCT. We therefore aimed to identify high-risk children who could benefit from recent advances in virus-specific immunotherapy, define the impact of viral reactivations on survival and estimate the economic burden of pre-emptive antiviral drug therapy. Between 2005 and 2010, prospective monitoring of 291 paediatric HSCT procedures revealed that reactivation of CMV (16%), ADV (15%) and EBV (11%) was frequent during period of CD4 T-cell lymphopenia (0.15 × 10(9) L(-1); P<0.05). We report significant risk factors for reactivation, most notably the use of serotherapy and development of GVHD (grade II) in the presence of pre-existing infection (ADV) or donor and/or recipient seropositivity (CMV, EBV). Most interestingly, CMV and ADV viraemia were the major independent predictors of mortality (P<0.05). CMV, ADV or EBV viral reactivation caused prolonged hospitalization (P<0.05), accounted for 15% of all mortality and substantially increased the cost of transplantation by ∼£22 500 ($34 000). This provides an economic rationale for targeting high-risk HSCT recipients with interventions such as virus-specific cell therapy.

Allogeneic stem cell transplant is curative for haemophagocytic lymphohistiocytosis (HLH) and refractory Langerhans cell histiocytosis (LCH). However, patients frequently have significant pre-transplant morbidity and there is high TRM. Because HLH is caused by immune dysregulation, we surmised that a reduced-intensity conditioned (RIC) regimen might be sufficient for cure, while decreasing the TRM. In 2006, we reported the outcome of 12 patients treated with RIC SCT from a matched family/unrelated or haploidentical donor. Here we discuss the update of these patients, including a total of 25 patients treated with RIC SCT for HLH and three for LCH. Twenty-one of the twenty-five patients with HLH (84%) are alive and well with remission at a median of 36 months from SCT. Mortality included pneumonitis (n=3) and hepatic rupture (n=1). All three patients treated with RIC SCT for LCH remain alive and in remission at a median of 5.1 years from SCT. Seven of twenty-four survivors (one with LCH) have mixed chimerism but remain disease-free. These data are supported by other groups including 100% survival in seven patients with HLH and 78% survival of nine patients with LCH. In summary, RIC compares favourably with conventional SCT with long-term disease control in surviving patients with both HLH and LCL, despite a significant incidence of mixed chimerism.

We report successful outcome in 13 children (median age 2.2 years) with high-risk AML who received SCT from an unrelated (11) or identical sibling (2) donor after a preparative regimen consisting of BU, CY and melphalan. Three children were 'poor'-risk in first CR, three in the second CR, five in PR and two had resistant disease. Immunotherapeutic strategies were employed to maximize a GVL response escalating through a reduced dose of alemtuzumab, early taper of CsA, donor lymphocyte infusion and treatment with alpha-IFN. Ten out of 13 (77%) children are alive in CR at a median of 41 months (range: 17-88) from SCT. There was no TRM, but three children relapsed and died 3, 4 and 17 months after SCT. These encouraging early results warrant further studies in children with very high-risk AML.

Infective diarrhoea is common among allogeneic stem cell transplant (SCT) recipients, frequently caused by viruses and may be difficult to differentiate from acute graft-versus-host disease (GVHD). Viral pathogens may directly or indirectly impact upon transplant-related mortality. Rotavirus is one of the most common causes of diarrhoea worldwide, but one of the least studied causes of diarrhoea post SCT. In this retrospective study we describe 21 cases of confirmed rotavirus infection in allogeneic SCT recipients. Most of these cases may occur in clusters during the winter and spring period. Symptoms of rotaviral infection were diarrhoea (95%), vomiting (62%), abdominal pain (38%), weight loss and loss of appetite in 38 and 29% of the cases, respectively. Possible extraintestinal manifestations of rotavirus infection were observed. The duration of the symptoms in this series ranged from 4 days to 4 months with median of 15 days. Patients with rotavirus infection were invariably lymphopenic and/or on immunosuppression for GVHD. Of the patients diagnosed with rotavirus, 86% required hospitalisation. In 57% of the cases, other viral pathogens were isolated near to the rotavirus infection period. Rotavirus infection is an important cause of prolonged diarrhoea post SCT, causing significant morbidity and frequently requiring hospitalisation.

CAMPATH-1H (C-1H) is widely used in vivo and / or in vitro for T cell depletion in hematopoietic SCT. This humanised monoclonal antibody is specific for CD52, a marker coexpressed on the majority of human lymphocytes with CD48 and other glycosylphosphatidyl-inositol (GPI) anchored proteins. We detected CD52 / CD48 dual expression on >99% of CD3(+) lymphocytes from normal individuals and all 15 post-SCT patients whose transplants did not utilise C-1H. By contrast, 23 / 26 patients with transplants involving C-1H (in vivo, in vitro or both) exhibited populations lacking CD52 expression that accounted for 49.7% (4.2-86.2%) of the CD3+ lymphocytes (median and range) in samples evaluated at a median of 2 months post-SCT. Most CD52- cells also lacked CD48 expression. These GPI- T cells were of either donor or mixed donor / recipient origin. They were predominant in the early months after SCT at times of profound lymphopenia and inversely correlated with the recovery of the absolute lymphocyte count (r= - 0.663, P<0.0001). The presence of CD52- cells has been correlated previously with clinical outcome after CAMPATH therapy for both malignant and nonmalignant diseases.

We conducted a retrospective review of the clinical features and outcome of adenovirus infection in 572 consecutive patients transplanted in a single centre over a 10 year period. One hundred patients (17%) had a total of 105 episodes of adenovirus infection diagnosed at a median of 18 days post transplant (range 2-150 days). The incidence was higher in children than adults (21% vs 9%, P < 0.001) and in unrelated donor vs matched sibling donor transplants (26% vs 9%, P < 0.001). Diarrhoea and fever were the most common presenting features. Reflecting these symptoms, the most common site of isolation was the stool. Serotypes 1, 2 and 7 were the most frequently seen (total of 41/68 or 60% of evaluable cases). In six patients (6%) adenovirus infection was the direct cause of death occurring at a median of 72 days post transplant (range 18-365 days). Five of these six patients had pulmonary involvement and four had associated graft-versus-host disease (GVHD). Three further patients were considered to have severe adenoviral disease (total incidence 9%). Isolation of virus from multiple sites correlated with a poor outcome (P < 0.001). Comorbid viral infection was common in this group with 50% of all patients having other viruses isolated (predominantly polyoma virus and cytomegalovirus). We conclude that adenovirus is commonly isolated after bone marrow transplant and is a cause of significant morbidity but was a rare cause of mortality (6/572 = 1%) in our patient group as a whole. The relative infrequency of severe infection will make it difficult for the transplant physician to decide which patients should receive experimental antiviral drugs such as ribavirin and cidofovir or immunomodulatory therapy with donor white cell infusions.

Only 30% of children have a matched family donor (MFD). Alternative donors can be found from volunteer unrelated donor (UD) panels, and almost every child has a haploidentical parental donor (Haplo). The outcome of alternative donor BMT has previously been inferior due to increased graft rejection and GVHD. The recent outcome of 121 consecutive children undergoing MFD, UD, and Haplo BMT between 1994 and 1997 was analysed. [table in text] Preparative regimens for MFD/UD/Haplo BMT respectively included TBI in 30%/36%/11%, chemotherapy only in 59%/64%/89%, Campath 1G or none n 14%/ 0%/0%. The balance of GVHD and rejection was addressed by T-cell depletion (Campath 1M) in 2/71 MFD BMTs, T-cell depletion with addback of 5 x 10(4) T cells/kg on day zero in 33/41 UD BMTs, and T cell depletion of purified mobilised peripheral blood CD34+ cells and bone marrow in 9/9 Haplo BMTs. Stable engraftment was achieved in 68/71, and 35/41 (one patient after 2nd BMT) and 7/9 MFD, UD, and Haplo BMTs respectively. Median follow up, survival, disease free survival and, death rates for MFD/UD/Haplo BMT were 12/12/12 months, 74%/77%/78%, 69%/67%/67%, and 27%/23%/23% respectively. Within a wide range of paediatric diseases the outcome of alternative donor BMT now parallels that of MFD BMT.