Impact of cell lines included in enterovirus isolation protocol on perception of nonpolio enterovirus species C diversity

Abstract

There has been under-reporting of nonpolio enterovirus species Cs (NPESCs) in Nigeria despite the fact that most isolates recovered from the Nigerian vaccine derived poliovirus serotype 2 (VDPV2) outbreak were recombinants with nonstructural region of NPESC origin. It has been suggested that cell lines included in enterovirus isolation protocols might account for this phenomenon and this study examined this suggestion. Fifteen environmental samples concentrated previously and analysed using L20B and RD cell lines as part of the poliovirus environmental surveillance (ES) program in Nigeria were randomly selected and inoculated into two cell lines (MCF-7 and LLC-MK2). Isolates were identified as enteroviruses and species C members using different RT-PCR assays, culture in L20B cell line and sequencing of partial VP1. Forty-eight (48) isolates were recovered from the 15 samples, 47 (97.9%) of which were enteroviruses. Of the enteroviruses, 32 (68.1%) belonged to enterovirus species C (EC) of which 19 (40.4%) were polioviruses and 13 (27.7%) were NPESC members. All 13 NPESC isolates were recovered on MCF-7. Results of the study show that NPESCs are circulating in Nigeria and their under-reporting was due to the combination of cell lines used for enterovirus isolation in previous reports.

Keywords: Environmental surveillance; Isolation protocol; MCF-7; Nigeria; Nonpolio enterovirus species C.