title: Enhanced detection of respiratory viruses using cryopreserved R-Mix ReadyCells.
abstract: BACKGROUND
  R-Mix, which contains a fresh mixture of two cell lines, Mv1Lu (mink lung cells) and A549 cells, has shown good sensitivity and specificity for respiratory virus culture. However, it has until recently only been available in North America, in part due to the shipping constraints associated with cell aging and the difficulty in providing these cells to hard to reach regions. Recently, cryopreserved R-Mix ReadyCells for longer storage were developed. These cells, which are shipped on dry ice and have a shelf life as long as 6 months from date of manufacture, can be thawed and used as needed with minimal addition of refeeding media.
  
  
  OBJECTIVE
  Assess the potential for cryopreserved R-Mix ReadyCells to replace conventional culture.
  
  
  METHODS
  Two hundred and twenty-three nasopharyngeal aspirates confirmed as respiratory virus-positive by conventional culture were inoculated into cryopreserved R-Mix ReadyCells and re-inoculated into conventional culture cells simultaneously. After 1 and 3 days of incubation cryopreserved R-Mix ReadyCells and conventional culture cells were screened using a respiratory virus fluorescent antibody pool for the detection of seven major respiratory viruses (influenza A and B viruses, parainfluenza 1, 2 and 3 viruses, respiratory syncytial virus and adenovirus). Positive pool results were further differentiated with specific monoclonal antibodies against the individual viruses.
  
  
  RESULTS
  After 1 day of incubation detection rates for conventional culture were 25%, 39%, 39%, 49%, and 10% for influenza A virus, influenza B virus, parainfluenza viruses, respiratory syncytial virus, and adenovirus, respectively. Corresponding detection rates for cryopreserved R-Mix ReadyCells were 78%, 91%, 72%, 81%, and 65%. Average detection rates of cryopreserved R-Mix ReadyCells for all respiratory viruses were 80% after 1 day incubation and 95% after 3 days incubation, compared to 35% and 70% by conventional culture.
  
  
  CONCLUSIONS
  The cryopreserved R-Mix ReadyCells system offers a highly sensitive and rapid method for detection of respiratory viruses that may allow it to replace conventional cell culture systems.
authors.affiliation: Department of Laboratory Medicine, Korea University College of Medicine, Seoul, Republic of Korea. kjskyi@gmail.com
authors.forename: Jang Su
authors.initials: JS
authors.lastname: Kim
authors.forename: Sun Hyung
authors.initials: SH
authors.lastname: Kim
authors.forename: Sook Young
authors.initials: SY
authors.lastname: Bae
authors.forename: Chae Seung
authors.initials: CS
authors.lastname: Lim
authors.forename: Young Kee
authors.initials: YK
authors.lastname: Kim
authors.forename: Kap No
authors.initials: KN
authors.lastname: Lee
authors.forename: Chang Kyu
authors.initials: CK
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods*; D002460:Cell Line; D002648:Child; D002675:Child, Preschool; D015925:Cryopreservation; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D008907:Mink; D009305:Nasopharynx / Q000821:virology; D012141:Respiratory Tract Infections / Q000821:virology*; D012680:Sensitivity and Specificity; D013997:Time Factors; D014776:Virus Cultivation / Q000379:methods; D014780:Viruses / Q000302:isolation & purification*