Mycobacterium tuberculosis infection in autologous or allogeneic hematopoietic stem cell transplant recipients at the Pediatric Oncology Institute

Abstract

In spite of having medical centers of excellence where bone marrow transplantation is performed, Brazil is a country with a high incidence of tuberculosis, with 47 cases/100,000 inhabitants, 111,000 new cases/year and with 6,000 annual deaths. So the risk hematopoietic stem cell transplant (SCT) patients are exposed to in Brazil might be higher than the risk of M. tuberculosis infection in other countries. However, the diagnosis of infection in those patients is complex due to the degree of immunosuppression, in particular if the immunologic recovery after the SCT has not occurred satisfactorily. Recently, an assay to detect M tuberculosis infection has become commercially available. This in vitro assay measures interferon-gamma released from memory T cells in response to stimulation with M. tuberculosis antigens. The ELISPOT assay has been widely tested in several populations and has the advantage of being more specific and sensitive than the tuberculin skin test. Moreover, the patient does not need to return to the medical center in 48-72 hours as it is required for the tuberculin skin test. We intend to perform a transversal study to evaluate M tuberculosis infection among 80 patients previously submitted to SCT at the pediatric BMT Unit of the Instituto de Oncologia Pediátrica-GRAACC, in São Paulo, Brazil. Pediatric patients who have undergone SCT at least 12 months before study entry will be assessed. The control group will be 80 individuals selected among healthy subjects matched for age with the SCT patients and who are SCT donors or patients' siblings. Individuals who agree to participate in the study will be assessed on the same day of a routine appointment. They will answer a questionnaire and will be submitted to a physical examination, chest x-ray and a tuberculin skin test. Also, a blood sample will be collected to evaluate ELISPOT for tuberculosis and lymphocyte immunophenotyping by flow cytometry to assess T, B, NK cells and regulatory T cells.The results from this study will provide the frequency of M tuberculosis infection among SCT recipients in our country as well as its clinical manifestations. Moreover, it will assess the benefit of ELISPOT as an auxiliary method to diagnostic M tuberculosis infection in specific groups such as SCT recipients. (AU)