Characterization of naturally occurring parainfluenza virus type 2 (hPIV-2) variants.
BACKGROUND
Human parainfluenza viruses (hPIV) are respiratory pathogens responsible for upper and lower respiratory tract infections. In most labs, the clinical diagnosis of hPIV is routinely done using techniques based on the detection of viral antigens such as immunofluorescence assay or/and viral isolation.


METHODS
Five hPIV-2 isolated from respiratory samples exhibited unusual phenotypic and antigenic characteristics. These isolates showed important syncytial cytopathic effect and failed to react with one specific monoclonal antibody. These variant strains were subsequently compared with hPIV-2 prototype strain by cellular and molecular techniques.


RESULTS
Both variant and prototype strains showed similar growth kinetics. Observation of plaque formation and syncytia assay indicated a more important fusogenic activity for the variant strains. Sequencing of fusion (F) and hemagglutinin-neuraminidase (HN) genes showed differences between the "atypical" hPIV-2 isolates and the Greer hPIV-2 prototype strain. These differences were analyzed with molecular modelling and structure prediction soft wares. A potential new glycosylation site in HN, in addition to minor changes observed in the predicted structure for the variant strains could explain their antigenic variation. Genetic changes in the fusion peptide and the cleavage site of F could also explain the difference observed in the fusion activity.


CONCLUSIONS
Continuous global viral surveillance is essential to monitor antigenic changes that may occur in nature particularly with regards to the implementation of diagnostic assays. The differences observed in F and HN between the prototype strain and clinical hPIV-2 variants could also provide new data for the analysis of Paramyxovirus fusion mechanisms and their pathogenesis.
Terrier
O
O
VirPath Laboratoire de Virologie et Pathologie Humaine, CNRS FRE 3011, Université Claude Bernard Lyon 1, Faculté de Médecine Laënnec, 69372 Lyon Cedex 08, France. olivier.terrier@sante.univ-lyon1.fr
Cartet
G
G
Ferraris
O
O
Morfin
F
F
Thouvenot
D
D
Hong
S S
SS
Lina
B
B
D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D000940:Antigenic Variation; D002460:Cell Line; D002648:Child; D006031:Glycosylation; D015707:HN Protein / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D000882:Haplorhini; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010223:Parainfluenza Virus 2, Human / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D010802:Phylogeny; D011487:Protein Conformation; D012367:RNA, Viral; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019351:Rubulavirus Infections / Q000821:virology*; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D010948:Viral Plaque Assay
D015707:HN Protein; D012367:RNA, Viral; D014760:Viral Fusion Proteins