MxA RNA quantification in febrile patients who underwent hematopoietic cell transplantation for primary immunodeficiency.

The presence of myxovirus resistance protein A (MxA) RNA was studied in 55 febrile children with primary immunodeficiency, 27 of whom underwent hematopoietic cell transplantation, and in 28 age-matched controls. The level of MxA RNA was above the cutoff, established as the 95th percentile found in controls, with primary immunodeficiency either undergoing transplantation or not in febrile patients, and with a documented diagnosis of infection by adenovirus, cytomegalovirus, Epstein-Barr virus, respiratory syncytial virus, and rotavirus. The presence of rare viral infections, unrecognized among those that more frequently occur in patients with primary immunodeficiency and in patients undergoing transplantation, may explain the high MxA RNA levels observed in some patients with fever but undetectable genomes or antibodies for the more common viruses. The level of MxA in febrile patients with acute graft versus host disease was below the cutoff, with a median level comparable with that observed in patients with primary immunodeficiency, who did not undergo transplantation and were without fever and infections, but significantly lower compared with controls. The level of MxA was well correlated with viral infections in follow-up samples. These data indicate that the measurement of MxA RNA is simple and useful to detect viral infections and in distinguishing them from acute graft versus host disease after allogeneic cell transplantation.