Demonstration of dual rhinovirus infection in humans by isolation of different serotypes in human heteroploid (HeLa) and human diploid fibroblast cell cultures.

The ability to isolate rhinoviruses in human heteroploid cell cultures was investigated by inoculating HeLa cells (HeLa M) with specimens previously shown to be positive in human diploid cell cultures. The 135 positive specimens selected were representative of 22 different rhinovirus types, and 4 to 9 specimens were available for each serotype. Specimens were inoculated into human diploid fetal tonsil fibroblasts (FT), HeLa cells with 30 mM Mg2+, and HeLa cells without increased Mg2+. One hundred twelve rhinovirus strains (83%) were reisolated in FT cells, whereas 76 rhinovirus strains (56%) were recovered in HeLa cells with 30 mM Mg2+. All strains recovered in FT were the same serotype as that originally recovered in diploid cells, but five of the HeLa cell isolates (3.7% of total specimens) were different serotypes, indicating dual rhinovirus infections. Four rhinovirus serotypes, (3, 42, 48, and 70) were recovered in HeLa but not in diploid cells; these serotypes were rare in our previous studies. Isolation of rhinovirus in FT cells was usually accomplished at first passage, whereas rhinovirus cytopathic effects in HeLa cells were not observed at first passage, but required one, two, or (rarely) three blind passages. Only 28 rhinoviruses (21%) were recovered in HeLa cells without increased Mg2+; however, three serotypes, types 16, 36, and 58, were recovered as effectively in HeLa cells, with or without added Mg2+, as they were in FT cells. In general, rhinoviruses were less efficiently recovered in HeLa cells; however, certain serotypes may be detected better by HeLa cells.