Molecular characterization of a variant rhinovirus from an outbreak associated with uncommonly high mortality.

BACKGROUND: Human rhinoviruses (HRVs) are the most frequent cause of acute upper respiratory tract infection, however, they are also known to replicate in the lower respiratory tract and associate with more severe respiratory illnesses. An outbreak of HRV occurred in a long-term facility in Santa Cruz, California with unusually high morbidity and mortality. OBJECTIVES: To identify viral characteristics associated with this unique outbreak, genetic relationships between these clinical isolates (SCRVs) and prototype strains of rhinovirus were investigated. STUDY DESIGN: Sequence homology and phylogenetic analyses of the SCRV VP4/VP2 region were performed in conjunction with all HRV prototypes. Due to the importance of the 5'noncoding region (NCR) and the structural genes to viral replication and host immune responses, respectively, we focused on a segment of the HRV genome which includes these regions. Molecular models of SCRV were also assessed. RESULTS: SCRV showed closest similarity to HRV82 with some divergence from the prototype. Amino acid differences were concentrated within predicted neutralization epitopes within VP2, VP3 and VP1. CONCLUSION: Sequence analyses and differences in cell culture growth characteristics suggest that this virus is a variant of HRV which has distinctive properties from its respective prototype strain.