Viral aggregation resulting in the failure to correctly identify an unknown rhinovirus

A seed lot of strain SF 1684 of rhinovirus type 2 prepared in human embryonic lung cells (WI-38) contained aggregates which interfered with its neutralization by homotypic or homologous antisera. The same virus showed no evidence of aggregation at five other passage levels studied. Virus in the seed lot was not identified correctly, and the titer of homologous antiserum was mistakenly considered to be low as a result of neutralization tests conducted with the aggregated virus. Filtration and a more easily effected treatment with sodium deoxycholate (1%) disaggregated the virus and restored its susceptibility to neutralization by homologous and homotypic antiserum.