Human metapneumovirus infection in lung transplant recipients: clinical presentation and epidemiology

In immunocompromised patients, respiratory viruses are likely to lead to lower respiratory tract infections that cause severe morbidity and mortality. We conducted a prospective study from September 2003 to March 2004 to investigate the epidemiology and impact of human metapneumovirus (hMPV) on lung transplant recipients.

We collected 265 nasopharyngeal aspirates and bronchoalveolar lavages: 51 samples originated from immunocompromised adults, 49 from lung transplant recipients, and 2 from a bone marrow recipient. Additionally, 209 samples from hospitalized non-immunocompromised children and 5 samples from immunocompromised children were analyzed for replicating hMPV by a combined cell culture and reverse transcriptase polymerase chain reaction method that includes DNA sequencing of selected isolates.

Twelve samples from lung transplant recipients (25%), 29 from non-immunocompromised children (14%), and 2 from a child with a renal transplant were positive for hMPV. Most of the cases clustered within 2 outbreaks in October/November and March. In immunocompromised patients, hMPV was isolated throughout the entire observation period. The same viral strains circulated in hospitalized children and in lung transplant recipients. A different strain was isolated during the interepidemic period, suggesting that hMPV infections may be transmitted among lung transplant recipients independently from the community outbreak situation. Clinical signs and symptoms varied from no symptoms to severe pneumonia or acute graft rejection. Significantly, the only deaths occurred in the hMPV-positive group. Of interest, identification of replicating hMPV significantly correlated with rejection symptoms present at the time point of sample collection.

Results of the study suggest that hMPV may be added to the list of pathogens that are possibly associated with episodes of allograft rejection.