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

AIMS: Filoviruses encompass highly pathogenic viruses placing significant public health burden on countries affected. Efforts for improved diagnostics and surveillance are needed. The requirement for high-containment can be circumvented by using pseudotype viruses (PV), which can be handled safely, in tropism, drug screening, vaccine evaluation, and serosurveillance studies. We assessed the stability and functionality after long-term storage of lyophilised filovirus pseudotypes for use in neutralisation assays.

METHODS AND RESULTS: We generated a panel of filovirus lentiviral pseudotypes followed by lyophilisation and storage in different conditions. Next, we reconstituted and tested PVs in infection experiments and pseudotype neutralisation assays where possible. 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 1-month storage, however, when lyophilised using pilot-scale facilities EBOV PVs retained titres and performed as standard in neutralisation assays after on 1-month storage at 37˚C.

CONCLUSIONS: Filovirus PVs are amenable to lyophilisation and can be stored for at least 2 years in a household fridge to be used in antibody assays. Lyophilisation performed in the right conditions would allow transportation at room temperature, even in warmer climates.