Diagnosis of human metapneumovirus infection in immunosuppressed lung transplant recipients and children evaluated for pertussis

Abstract

Human metapneumovirus (hMPV) is a recently discovered paramyxovirus that is known to cause respiratory tract infections in children and immunocompromised individuals. Given the difficulties of identifying hMPV by conventional culture, molecular techniques could improve the detection of this virus in clinical specimens. In this study, we developed a real-time reverse transcription-PCR (RT-PCR) assay designed to detect the four genetic lineages of hMPV. This assay and a commercial real-time nucleic acid sequence-based amplification (NASBA) assay (bioMérieux, Durham, NC) were used to determine the prevalence of hMPV in 114 immunosuppressed asymptomatic and symptomatic lung transplant recipients and 232 pediatric patients who were being evaluated for pertussis. hMPV was detected in 4.3% of the immunosuppressed lung transplant recipients and in 9.9% of children evaluated for pertussis. Both RT-PCR and NASBA assays were efficient in detection of hMPV infection in respiratory specimens. Even though hMPV was detected in a small number of the lung transplant recipients, it was still the most prevalent etiologic agent detected in patients with respiratory symptoms. In both of these diverse patient populations, hMPV infection was the most frequent viral respiratory tract infection identified. Given our findings, infection with hMPV infection should be determined as part of the differential diagnosis of respiratory illnesses.

FIG. 1.

Sensitivity of hMPV real-time RT-PCR. (A and B) Amplification plot and the external standard curve generated by serially diluted hMPV N-gene in vitro transcripts by real-time RT-PCR. The values shown in panel A represent hMPV RNA copies/RT-PCR. Based on copy numbers of the in vitro-transcribed RNA standards, the lower detection limit is 100 RNA copies/RT-PCR by real-time RT-PCR.

FIG. 2.

Seasonal variation of hMPV prevalence. (A) Graphical representation of the total number of respiratory specimens received from lung transplant recipients during May 2004 to April 2005 and the number of samples positive for hMPV RNA. (B) Graphical representation of the total number of respiratory specimens received from pediatric patients during February to May 2005 and the number of hMPV-positive samples detected during each month.