G.D. Myers

Adenovirus infection rates in pediatric recipients of alternate donor allogeneic bone marrow transplants receiving either antithymocyte globulin (ATG) Or alemtuzumab (Campath)

Summary:Infectious complications due to adenovirus are of increasing concern after allogeneic stem cell transplantation. Over the past 4 years, we have modified our conditioning regimens to use alemtuzumab in preference to anti-thymocyte globulin (ATG) for pediatric patients receiving stem cell transplants from alternate donors. Recent reports in adult studies implicate alemtuzumab as a risk factor for adenovirus infection. We therefore evaluated the incidence of adenovirus infection in pediatric patients receiving either ATG or alemtuzumab in their conditioning regimens. Of the 111 patients evaluated, a total of 54 patients received ATG and 57 patients received alemtuzumab. In total, 35/111 (32%) patients were infected by adenovirus, and 9/111 (8%) had adenovirus disease (AD). Adenovirus infection was greater in the alemtuzumab group than the ATG group (23/57 vs 12/54) (P=0.039) and disseminated AD was more frequent in the alemtuzumab group vs the ATG group (8/57 and 1/54 respectively) (P=0.032). The presence of Grade 3–4 graft-versus-host disease was a risk factor for adenovirus infection. Our findings highlight the fact that adenovirus infection is a frequent complication after stem cell transplantation from alternate donors in the pediatric population and that alemtuzumab increases the risk of infection compared to ATG. This work will help in identifying at-risk populations for our upcoming immunotherapy trial using adoptively transferred donor-derived adenovirus-specific cytotoxic T lymphocytes.

Reconstitution of adenovirus-specific cell-mediated immunity in pediatric patients after hematopoietic stem cell transplantation

Adenovirus (adv) is a significant cause of morbidity and mortality in pediatric hematopoietic stem cell transplant recipients, and control of infection seems to require antigen-specific T cells. We evaluated the recovery of adv-specific cellular immunity in this patient population related to degree of T-cell immunosuppressive therapy and compared this to adv cellular immunity of normal donors. Over 12 months, we monitored for adv DNA in stool and blood of patients and in the blood of a normal donor group. Twenty-two pediatric hematopoietic stem cell transplant (HSCT) patients (14 months–20 years) who received matched-related (MRD n=6), mismatched related (Haplo n=6) or matched unrelated donor (MUD n=10) grafts, were followed and results compared to healthy controls (n=8). Adv was detected by polymerase chain reaction in blood and/or stool from 81.8% of patients on at least one occasion post-HSCT, but only 68% of patients developed symptomatic adv infections. Recovery of adv-specific T cells was significantly delayed in the MUD and Haplo recipients, whereas recovery in the MRD group was similar to levels detected in healthy donors within 30 days post-transplant. In conclusion, recipients of alternative donor transplants at our institution have significantly delayed adv-specific cellular immune recovery, which correlates to an increased risk of adv-associated morbidity and mortality.

T‐Cell Immunotherapy for Adenoviral Infections of Stem‐Cell Transplant Recipients

Abstract: Human adenoviruses are ubiquitous lytic DNA viruses that can be divided into 51 different serotypes, grouped from A to F on the basis of genome size, composition, homology, and organization. Adenovirus infections, although frequent, are rarely fatal in immunocompetent individuals, due to potent innate and adaptive immune responses. By contrast, adenoviruses are a significant cause of morbidity and mortality in immunosuppressed individuals, for whom there are limited treatment options. Since antiviral drugs have variable efficacy in the treatment of severe adenovirus disease, iatrogenic reconstitution with in vitro expanded virus‐specific cytotoxic T lymphocytes (CTLs) is an attractive option for prophylaxis and treatment, particularly because the endogenous recovery of adenovirus‐specific T cells has proved important in controlling infection in vivo. Thus, we have characterized human T‐cell responses to adenovirus in vitro and explored the potential of adoptive T‐cell immunotherapy as a prophylactic or therapeutic strategy for adenovirus infections posttransplant.

Outcome of hematopoietic stem cell transplant as salvage therapy for Hodgkin's lymphoma in adolescents and young adults at a single institution

For patients with relapsed Hodgkins lymphoma (HL), high dose chemotherapy with stem cell rescue (HDCT-SCT) may improve survival over chemotherapy alone. We assessed the outcomes of HDCT-SCT in 37 consecutive adolescent and young adult patients with relapsed HL whose malignancy was categorized based on sensitivity to chemotherapy. We determined whether current outcomes supported the use of HDCT-SCT in all of our patients or just those patients with lower-risk characteristics such as chemosensitivity. With a median follow-up of 6.5 years, the 2-year overall survival (OS) was 89% (95% CI: 62–97%) for the chemosensitive patients (n = 21), whereas for patients with resistant disease (n = 16), OS was 53% (95% CI: 25–74%). Both autologous and allogeneic transplants were well tolerated, with 100-day treatment-related mortality under 10%. Our data show encouraging outcomes for patients with chemosensitive relapsed HL who receive hematopoietic stem cell transplant (HSCT) and support the value of the procedure even when the disease is chemoresistant.

1074. The Use of Genetically Modified Antigen Presenting Cells to Generate Donor-Derived Virus-Specific Cytotoxic T Lymphocytes Reactive Against CMV and Adenoviral Antigens for Clinical Use

CMV and Adenovirus are major viral pathogens causing morbidity and mortality in immunocompromised patients undergoing allogeneic stem cell transplantation. Previous studies have shown that prophylactic adoptive immunotherapy with donor-derived Cytotoxic T Lymphocytes (CTL) directed against EBV and CMV can effectively prevent the clinical manifestations of these viruses. We have extended these studies by generating CTL from PBMC from CMV seropositive normal donors that should restore cellular immunity to both CMV and adenovirus simultaneously using gene transfer to modify antigen-presenting cells. We have generated a clinical grade recombinant adenovirus type 5 vector pseudotyped with a type 35 fiber (Ad5f35pp65) carrying a transgene for the immunodominant CMV antigen, pp65. We have developed a protocol utilizing an initial round of stimulation with autologous mononuclear cells transduced with Ad5f35pp65, followed by 2 rounds of weekly stimulation with autologous EBV-lymphoblastoid cell lines (LCL) transduced with the same vector using MOIs of 10 and 100 respectively. After 3 rounds of stimulation, four CTL cultures contained a mean of 96% (range 93–99%) CD8+ve and a mean of 4% (range 1.3–7%) CD4+ve cells. All CTL lines showed significant cytotoxicity in chromium release assays against CMV targets and 3/4 lines also showed specific lysis against adenovirus targets. Further, using MHC-peptide multimers we have been able to demonstrate the simultaneous presence of CD8+ve cells recognizing peptide epitopes from CMV pp65 (range 2.32–21%) and Adenovirus hexon (1.07–8.08%) in the CTL cultures. So far we have treated 3 patients in this phase I CMV prophylaxis study. All patients received 1 infusion of virus-specific CTL at a dose of 110e7/m2 from day 30 post transplant. We observed up to a 28-fold increase in CMV pentamer positive CD8+ve T cells post CTL. At last follow-up (2–10 weeks) all patients remain CMV negative. One patient was culture positive for adenovirus in her stool pre CTL therapy. Within 2 weeks of CTL infusion we observed a 2-log reduction of adenovirus copies/gram stool at which time the patients symptoms (fever, loose stools) resolved. In summary, we have developed a protocol for the efficient generation using genetically modified monocytes and LCL to expand CTL ex vivo with specificity for CMV and adenovirus. CMV-pentamer specific CD8+ve T cells increase in the peripheral blood post CTL infusion despite infusing relatively low numbers of cells. Further, reduction in adenovirus load in stool suggests efficacy of adenovirus specific CTL in vivo. However, expansion of virus-specific CTL in vivo may require presence of antigen. We will therefore complete this prophylaxis study and then proceed to using virus-specific CTL for the treatment of CMV and adenovirus infections post transplant.