Human herpesvirus 6 reactivation and encephalitis in allogeneic bone marrow transplant recipients

To determine whether receipt of an investigational anti-CD3 monoclonal anti body (BC3) increased the risk of human herpesvirus 6 (HHV-6) reactivation a nd development of encephalitis in bone marrow transplant (BMT) recipients, persons who had and had not received BC3 were compared. Odds of HHV-6 react ivation were higher among BC3 recipients than among control patients (odds ratio, 2.5; 95% confidence interval [CI], 1.3-4.7). In addition, BC3 recipi ents were more likely than control patients to develop encephalitis (risk r atio [RR], 3.5; 95% CI, 1.3-9.5), and this association followed a BC3 dose- dependent relationship (P=.03, by Mantel-Haenszel chi (2) test). In a multi variable model, HHV-6 reactivation and receipt of BC3 were associated with increased risk of encephalitis (RR, 5.4; 95% CI, 1.9-15.3, and RR, 3.3; 95% CI, 1.2-9.1, respectively). In conclusion, both HHV-6 reactivation and rec eipt of BC3 for prophylaxis of acute graft-versus-host disease independentl y increased the risk of encephalitis in allogeneic BMT recipients. Prospect ive studies to better define the relationship between HHV-6 reactivation an d encephalitis in allogeneic BMT recipients are warranted.