Application and comparison of lyophilisation protocols to enhance stable long-term storage of filovirus pseudotypes for use in antibody neutralisation tests

ABSTRACT Filoviruses encompass highly pathogenic viruses placing sporadic public health burden on countries affected. Efforts for improved diagnostics and surveillance are needed considering the recent Ebola outbreaks in Africa. The need for high containment facilities can be circumvented by the use of pseudotype viruses (PV), which can be handled in low containment, for tropism, drug screening, vaccine immunogenicity and serosurveillance studies. In this study we assessed stability and functionality after long-term storage of lyophilised filovirus pseudotypes for use in neutralisation assays. Lyophilised Ebola and Marburg PVs retained production titres for at least two years when stored at +4°C or less. Lyophilised Ebola PVs performed similarly to non-lyophilised PVs in neutralisation assays after reconstitution. When stored at high temperatures (+37°C), lyophilised PVs did not retain titres after one-month storage, however, when lyophilised using pilot scale facilities EBOV PVs retained titres and performed well in neutralisation assays after one-month storage at 37°C suggesting removing residual moisture might be crucial for avoiding cold-chain transportation. Lyophilisation could allow reagents to be transported more efficiently as well as reducing costs for a future serological kit.