Reimar Johne, German Federal Institute for Risk Assessment

Reimar Johne1, Roman Valusenko-Mehrkens1, Nkhasi Lekena2, Martin Visser2, Hester O’Neill2, Albie van Dijk2 and Alexander Falkenhagen1 1Federal Institute for Risk Assessment, Berlin, Germany 2Department of Microbiology and Biochemistry, University of the Free State, Bloemfontein, South Africa

Combatting and Exploiting dsRNA viruses

Rotavirus A represents the leading cause of severe diarrhea in young children in low- and middle-income countries. Although vaccination programs significantly decreased the rotavirus burden, vaccine efficacy is comparatively low in Sub-Saharan Africa. Among other factors, differences between vaccine strains and African wildtype strains might be responsible. As cell culture isolation and attenuation of human rotavirus field strains is difficult, reverse genetics systems (RGS) might be used to overcome this problem. We aimed to generate an RGS for a G9P[6] neonatal strain, GR10924, originating from South Africa and never isolated in cell culture. The 11 genome segments were synthetized and used together with an established RGS for simian strain SA11. Using GR10924-VP4 alone or in combination with GR10924-VP6/VP7 in the backbone of SA11, a spontaneous replication-enhancing mutation was identified in GR10924-VP4 after short-term passaging in MA-104 cells. However, even the mutated GR10924-VP4 did not support generation of infectious virus together with the remaining GR10924 plasmids. Therefore, combinations of plasmids were tested by stepwise substitution of SA11 and GR10924 genome segments. Eventually, a reassortant containing the NSP5-encoding segment of SA11, but the other 10 genome segments of GR10924, could be efficiently rescued in cell culture. Experiments are ongoing to determine potential reasons for the limiting role of GR10924-NSP5. The results show that a rotavirus containing nearly all genome segments of a representative African human strain can be generated using the applied RGS, which might represent a candidate for next-generation rotavirus vaccines for the African continent.