Prospective study of human metapneumovirus infection: diagnosis, typing and virus quantification in nasopharyngeal secretions from pediatric patients.
METHODS
During the winter-spring seasons 2004-2005 and 2005-2006, 965 nasopharyngeal aspirates from 871 patients were examined for human metapneumovirus (hMPV) by both monoclonal antibodies (MAbs) and reverse transcription (RT)-PCR.


RESULTS
Overall, 46 samples (4.8%) from 37 patients were positive for hMPV. Of these, 39 were positive by RT-PCR, and 35 by MAbs. Thus, using RT-PCR as a reference assay, the sensitivity, specificity, positive and negative predictive values of MAbs were 71.8%, 99.2%, 80.0% and 98.8%, respectively. Typing showed that concordant results were obtained in 32/46 (69.6%) strains (five untyped), whereas three strains were typed by MAbs only, and 11 by RT-PCR only. Finally, quantification of hMPV RNA allowed to correlate high viral load in nasopharyngeal secretions with acute respiratory symptoms in a group of 11 infants with acute lower respiratory tract infection examined upon admission and discharge from hospital, and a group of nine infants examined upon admission only. Conversely, hMPV etiology was questioned in a group of 14 infants with low viral load.


CONCLUSIONS
MAbs may represent an alternative to or a complement to RT-PCR for detection and typing of hMPV strains, while hMPV RNA quantification may help in associating viral load with clinical symptoms.
Gerna
Giuseppe
G
Servizio di Virologia, Fondazione IRCCS Policlinico San Matteo, 27100 Pavia, Italy. g.gerna@smatteo.pv.it
Sarasini
Antonella
A
Percivalle
Elena
E
Campanini
Giulia
G
Rovida
Francesca
F
Marchi
Antonietta
A
Baldanti
Fausto
F
D000208:Acute Disease; D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D002460:Cell Line; D002648:Child; D006801:Humans; D015994:Incidence; D007223:Infant; D029121:Metapneumovirus / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D017817:Nasal Lavage Fluid / Q000821:virology*; D018184:Paramyxoviridae Infections / Q000175:diagnosis* / Q000821:virology; D010802:Phylogeny; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012367:RNA, Viral / Q000097:blood; D012141:Respiratory Tract Infections / Q000175:diagnosis* / Q000821:virology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D012680:Sensitivity and Specificity; D019562:Viral Load
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D012367:RNA, Viral