PerspectiveImmunology

B cells, CMV, and stem cell transplant

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Science  18 Jan 2019:
Vol. 363, Issue 6424, pp. 232-233
DOI: 10.1126/science.aav9867

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Summary

Hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for various malignant and nonmalignant conditions but can be complicated by infections such as reactivation of cytomegalovirus (CMV). CMV is a ubiquitous DNA herpes virus comprising various distinct strains (1). Around 60 to 90% of healthy adults are seropositive, indicating past exposure to the virus, although infections in healthy people are often mild or asymptomatic. After initial acute infection, CMV enters a latent phase, similar to other herpes viruses. It has been suggested that CMV infection may confer an immunological benefit, perhaps explaining its prevalence, because comparison of seropositive and seronegative individuals has shown that CMV infection results in greater responses to the flu vaccine (2). The immune system is essential to control the initial infection and to prevent later CMV reactivation, as demonstrated by the high incidence of CMV reactivation in immunosuppressed patients such as HSCT recipients. Whereas the incidence and severity of CMV transcriptional reactivation and cell-to-cell dissemination after HSCT has substantially diminished since the adoption of prophylactic or preemptive antiviral therapies (3), CMV remains the most important viral infection after HSCT, especially in high-risk patients (such as seropositive recipients of seronegative donors), and can lead to life-threatening CMV disease in ∼10% of HSCT recipients (4). On page 288 of this issue, Martins et al. (5) make the unexpected observation, in mice undergoing bone marrow transplantation (BMT) as a model of HSCT, that strain-specific CMV antibodies made by host B cells play a crucial role in preventing CMV dissemination after BMT. They propose that passive transfer of antibodies that are matched to the latent CMV strain in HSCT recipients might constitute a powerful and easy therapeutic approach to prevent CMV disease.