Relating plaque morphology to respiratory syncytial virus subgroup, viral load, and disease severity in children

Abstract

BackgroundViral culture plaque morphology in human cell lines are markers for growth capability and cytopathic effect, and have been used to assess viral fitness and select pre-attenuation candidates for live viral vaccines. We classified RSV plaque morphology and analyzed the relationship between plaque morphology as compared to subgroup, viral load and clinical severity of infection in infants and children.MethodsWe obtained respiratory secretions from 149 RSV-infected children. Plaque morphology and viral load was assessed within the first culture passage in HEp-2 cells. Viral load was measured by PCR, as was RSV subgroup. Disease severity was determined by hospitalization, length of stay, intensive care requirement, and respiratory failure.ResultsPlaque morphology varied between individual subjects; however, similar results were observed among viruses collected from upper and lower respiratory tracts of the same subject. Significant differences in plaque morphology were observed between RSV subgroups. No correlations were found among plaque morphology and viral load. Plaque morphology did not correlate with disease severity.ConclusionsPlaque morphology measures parameters that are viral-specific and independent of the human host. Morphologies vary between patients and are related to RSV subgroup. In HEp-2 cells, RSV plaque morphology appears unrelated to disease severity in RSV-infected children.

Respiratory Syncytial Virus: Infection, Detection, and New Options for Prevention and Treatment

“…Kim et al reported larger plaque sizes caused by RSVA isolates than by RSVB (247), and there was a distinct difference in plaque morphology between RSVA and RSVB isolates (247). However, the authors reported no significant correlation between clinical severity and plaque size or morphology of type A and type B viruses using a classic plaque-clearing assay (247). Some RSV isolates can be poor at causing plaque clearings in cultured cell monolayers, so it would be interesting to study plaque size and morphology using an antibody detection assay of RSV plaques.…”

“…These were cultured viral isolates, so the plaque morphologies that were observed were the product of intrinsic features of the virus's own genomic constitution. Kim et al reported larger plaque sizes caused by RSVA isolates than by RSVB (247), and there was a distinct difference in plaque morphology between RSVA and RSVB isolates (247). However, the authors reported no significant correlation between clinical severity and plaque size or morphology of type A and type B viruses using a classic plaque-clearing assay (247).…”

“…Immunological diversion by an RSV type during one season may render the population more susceptible to the other type in subsequent seasons (246). Whatever the cause of alternating epidemics of RSV types, it is generally well accepted that RSVA viral loads tend to be higher than RSVB viral loads by about a logarithm (247). The higher viral loads of RSVA in the nasopharynx may enable faster transmission between individuals because more virus is shed for digital inoculation via the eyes and nose (248,249).…”

“…The rates of spread and the virulence levels of RSV types have been compared by plaque assay in tissue culture (247). A unique report by Kim et al compared the morphologies of RSV plaques derived from pediatric patient isolates (247).…”

“…A unique report by Kim et al compared the morphologies of RSV plaques derived from pediatric patient isolates (247). These were cultured viral isolates, so the plaque morphologies that were observed were the product of intrinsic features of the virus's own genomic constitution.…”