title: Most human metapneumovirus and human respiratory syncytial virus in infant nasal secretions is cell free.
abstract: BACKGROUND
  Nasopharyngeal secretions aspirated from infants with bronchiolitis (NPA) are a valuable resource for the study of virus dynamics and local inflammatory responses, however samples are small and difficult to manipulate.
  
  
  OBJECTIVE
  To improve yield of NPA from infants. To establish if removal of the cellular component of NPA affects quantification of human metapneumovirus (hMPV) or human respiratory syncytial virus (hRSV) genome.
  
  
  METHODS
  Weight of NPA collected into traps from 30 infants was compared with that collected in trap plus catheter and washed through with saline from another 30 infants. hMPV (n=33) and hRSV (n=30) genome was measured by reverse-transcribed real-time polymerase chain reaction (RT-RT-PCR) in paired whole and cell-free NPA collected by the improved method.
  
  
  RESULTS
  The improved method of NPA collection gave near two-fold greater weight (p = 0.002) of NPA (mean = 0.52 g (S.D. = 0.30 g)) than the traditional method (0.32 g (S.D. 0.19)). There was strong agreement and no significant difference between viral load measured in whole and cell-free fractions of NPA for both viruses (samples (n), correlation coefficient (cc) and significance (p)); hMPV (n=33, cc=0.938, p<0.001) and hRSV (n=30, cc=0.977 and p<0.001).
  
  
  CONCLUSIONS
  The majority of hRSV and hMPV in nasal secretions is not associated with cells. Removal of the cellular component of NPA does not interfere with quantification of hRSV and hMPV.
authors.affiliation: Division of Child Health, School of Reproductive and Developmental Medicine, School of Infection and Host Defence, University of Liverpool, United Kingdom. m.g.semple@liv.ac.uk
authors.forename: M G
authors.initials: MG
authors.lastname: Semple
authors.forename: J A
authors.initials: JA
authors.lastname: Booth
authors.forename: B
authors.initials: B
authors.lastname: Ebrahimi
mesh_terms: D001990:Bronchiolitis, Viral / Q000821:virology; D006801:Humans; D007223:Infant; D029121:Metapneumovirus / Q000235:genetics / Q000302:isolation & purification*; D017817:Nasal Lavage Fluid / Q000166:cytology* / Q000821:virology*; D018184:Paramyxoviridae Infections / Q000821:virology; D012367:RNA, Viral / Q000032:analysis / Q000302:isolation & purification; D018357:Respiratory Syncytial Virus Infections / Q000821:virology; D018113:Respiratory Syncytial Virus, Human / Q000235:genetics / Q000302:isolation & purification*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013048:Specimen Handling / Q000379:methods*; D019562:Viral Load
chemical_list: D012367:RNA, Viral