Viral Infections in Hematopoietic Stem Cell Transplant Recipients [chapter]

Per Ljungman
2009 Allogeneic Stem Cell Transplantation  
Hematopoietic stem cell transplant (HSCT) recipients are at an increased risk of bacterial, viral, fungal and parasitic infections. Past exposures to infections, the degree of immunosuppression, prolonged neutropenia and presence of graft versus host disease (GVHD) are some of the factors which make HSCT recipients more susceptible to infections. Viral infections have emerged as a major challenge causing high morbidity and mortality in stem cell transplant recipients. Myeloablative conditioning
more » ... lative conditioning regimens and GVHD prevention strategies which may delay immune reconstitution and serologic status of donors and recipients affect the incidence of viral infections. Community-acquired respiratory and gastrointestinal viral infections like respiratory syncytial virus (RSV), rhinovirus, adenovirus, influenza, norovirus and reactivation of latent viruses like herpes simplex virus (HSV), cytomegalovirus (CMV) are some of the important pathogens increasing the morbidity and mortality in transplant recipients. Clinical manifestations range from asymptomatic carriage to severe disease. Due to lack of effective agents to treat viral infections and emerging resistance patterns, preventive and prophylactic strategies are valuable. Our review article provides an overview of commonly encountered viral infections and their management in an allogeneic stem cell transplant setting in the adult age group. Keywords Viral infections; allogeneic stem cell transplants; hematopoietic stem cell transplants Introduction Viral infections can be asymptomatic or subclinical or even lead to severe disease in allogeneic HSCT recipients. Viral diseases of importance in HSCT include herpes simplex virus (HSV), varicellazoster virus (VZV), human herpesvirus 6 (HHV-6), cytomegalovirus (CMV), Epstein-Barr virus (EBV) and respiratory viruses (eg, respiratory syncytial virus, adenovirus, influenza, parainfluenza). Most of these viral infections are opportunistic in nature and are related to factors influencing engraftment and immune reconstitution [1] . Increase in HLA mismatched donor allogeneic transplants and using anti-thymocyte globulin (ATG) for GVHD prevention are few factors which predispose recipients to viral infections [2, 3]. Fortunately, based on molecular diagnostic methods, a polymerase chain reaction can offer an early diagnosis of these infections [4, 5] . Early diagnosis facilitates timely intervention controlling infection associated complications. Many prophylactic and pre-emptive treatment strategies are also aimed at decreasing viral infection-related complications [6] . Immunotherapy to restore virus-specific immunity are proven to be effective in treating CMV, EBV and adenovirus infections [7] . In our review article, we have made an attempt to discuss risk factors for post-HSCT viral infections, preventive strategies and treatment options. Risk Factors for Viral Infections Source of Stem Cells Peripheral blood stem cells achieve faster hematopoietic and immune reconstitution compared to bone marrow and cord blood source. Hence, this is associated with fewer incidences of viral infections [8, 9]. Donor and Patient Characteristics Serology status of donors and recipients affects the incidence of viral infections. For example, if a donor is CMV seronegative, then a CMV seropositive recipient is at a very high risk of CMV reactivation [10]. Similarly, previous recipient exposure to VZV, HSV and EBV pose a higher risk of reactivation during immunosuppression. Anti-viral prophylaxis and pre-emptive therapy can be given to avoid these complications [11]. Older age group and multiple lines of chemotherapy prior to HSCT also increase the risk of viral infections. Degree of HLA (Human Leukocyte Antigen) Match An increased risk of viral infections is noted in HLA-mismatch related and unrelated transplantation compared to HLA-match related transplantation. This is secondary to delayed
doi:10.1007/978-1-59745-478-0_29 fatcat:ymixlail7zgghilprqmw3wrzum