CMV and transfusions, an old story that's not quite over yet

Krishna G BadamiNew Zealand Blood Service, Christchurch, New ZealandAbstract: Cytomegalovirus (CMV), or human herpes virus 5, can cause a serious infection in immunocompromised patients. Primary infection can be vertical or horizontal – the latter includes transfusion-transmitted CMV (TT-CMV). The immune response against CMV involves both innate (eg, natural killer cells) and adaptive (humoral and cell-mediated) immunity. Through elaborate immune evasion mechanisms, CMV manages to stay latent, mainly in myeloid blood cells. T lymphocytes are mainly responsible for maintaining latency and preventing reactivation. In otherwise healthy individuals, the CMV infection is mild or subclinical. In immunocompromised patients (but also others), primary or reactivated CMV infection can cause significant disease. In addition to direct effects, a range of indirect effects – inflammatory, vasculopathic, etc – can be caused. Some of the indirect effects of CMV may be important even in immunocompetent but ill individuals. In immunocompromised patients, prophylaxis – either universal prophylaxis or preemptive treatment using antiviral drugs, such as ganciclovir against CMV – may be appropriate. The treatment of established CMV infection normally employs the same drugs. The role of intravenous immunoglobulin or CMV-specific hyperimmune globulin in prophylaxis and treatment is uncertain. New anti-CMV drugs, T-cell immunotherapy, and a vaccine are all being developed. From a transfusion medicine perspective, it is important to have a certain background knowledge of CMV, including: an understanding of its epidemiology; the immune response to it; and its clinical features. More specific areas of interest are blood donor selection using methodologies such as routine serology and, possibly, nucleic acid testing, to identify those who pose significant risks of TT-CMV. What are the ways of preventing TT-CMV even from potentially infective donors? The answer may, potentially, be achieved through leukoreduction and pathogen reduction technology.Keywords: cytomegalovirus, transfusion, infection, Herpesviridae, reactivation, transfusion medicine, leucoreductio