Development of Echovirus 29 cytopathology in RD cell line might not happen within 10 days post inoculation

ABSTRACT Echovirus 29 (E29) is a member of Species Enterovirus B (EV-B) in the genus Enterovirus, family Picornaviridae , order Picornavirinae . In Nigeria, molecular characterization of E29 was first described in 2002. In 2015, we found that a new clade of E29 had replaced that described in Nigeria in 2002-2003. To date, E29 isolates described from Nigeria were isolated in cultures of RD cell line. In 2016, we characterised an E29 strain that did not show cytopathology on RD cell line within the recommended 10 days of culture. Here we show that the E29 in question grows with evident CPE in RD cell culture like other members of the clade when allowed to stay in culture for 13 to 14 days. The findings of this study therefore suggest that some of the samples declared negative for enteroviruses by the current WHO cell culture based detection algorithm might be false negatives. It is therefore encouraged that those particularly interested in non-polio enteroviruses endeavour to maintain at least 14 days incubation in cell culture in a bid to accommodate NPEVs like E29 that might need longer time to develop CPE especially when present at low titre.