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Stability and biophysical properties of mumps and measles virus

Mumps (MuV) and measles viruses (MeV) are nonsegmented, negative stranded RNA viruses of the family Paramyxoviridae, subfamily Paramyxovirinae. MuV and MeV are the cause of mumps and measles disease, both preventable by vaccination. MuV and MeV have ribonucleocapsid enveloped with lipid bilayer which is spiked with two glycoproteins responsible for cell recognition and virus entry into the host cell. Biophysical properties of MuV and MeV are still not well known and these are important in the basic research of these viruses and especially in vaccine production. The aim of this research was to investigate virus stability and infectivity at various pH and temperature conditions as well as to test the impact of various buffer solutions on MuV and MeV. Also, effects of ultrafiltration and ultracentrifugation on viruses were investigated. Concentrations of live MuV or MeV were determined by 50% cell culture infective dose assay (CCID50 assay) and the result of this assay is the virus titer. Size and concentration of virus particles were determined by Nanoparticle Tracking Analysis (NTA) using NanoSight instrument. Size and concentration of virus particles are of utmost importance since they provide insight into particle integrity and possible aggregation which is presumed to be one of factors causing loss of infectivity. Functionality of MuV glycoproteins under different pH conditions was additionally monitored by in vitro MuV capability to agglutinate guinea pig red blood cells. Although the size of MuV and MeV is reported to be up to 600 nm, our results so far indicate that filtration through 450 nm filter does not affect virus titers. Mean sizes of MuV and MeV measured by NTA method were 222.2 ± 9.83 and 185.7 ± 13.98 nm, and 90 % of particles were below 308 and 272 nm respectively. Pelleting of viruses by ultracentrifugation resulted in poor titer recoveries and this correlated with increasing ultracentrifugation time. On the other hand, lower centrifugation times did not effectively pellet the virus as shown by the number of virus particles in supernatant. Ultrafiltration on 100 kDa membranes (regenerated cellulose and PES) proved to be effective in virus concentration. Hemagglutination assay showed irreversible deleterious impact of extreme pH conditions on viruses and these conditions also induced changes in size. It can be concluded that MuV and MeV are of very delicate structure and easily lose infectivity in procedures aimed for their purification although their structural integrity remains intact.

measles virus ; mumps virus ; Nanoparticle tracking analysis ; ultracentrifugation ; ultrafiltration

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