TDK conference 2022

One of the substantial challenges of the production of live virus vaccines is the reduction of the infectious titre of viruses during formulation and storage. Electrospinning (ES), an innovative method of nanotechnology may be a suitable option to enhance stability via the incorporation of viruses (along with other biologicals) into nanofibres. The virus-carrying nanofibre matrix may promote resistance to environmental impacts, providing protection for the integrated viruses. This method is more cost-effective and operates at less demanding temperature and pressure conditions than traditionally used freeze-drying or spray-drying.

During our experiments, we propagated viruses BoHV-1 and TGEV on MDBK and ST/E62 cell cultures, respectively. Viral suspensions that reached appropriate titre were concentrated and purified by preparative ultracentrifugation. In a preliminary experiment, viruses were mixed with solutions that can be used as the basis of ES to reveal their potential inactivating effect. Scaled-up production of nanofibres was performed using a high-speed electrospinning (HSES) platform. Mannitol and sucrose were used as stabilizing additives. The quantity of infective virions dissolved from the nanofibres was detected by titration, the virus-specific nucleic acid copy numbers were measured with qPCR technique, and the morphology of the finished nanofibers was demonstrated by scanning electron microscopy.

The tolerance test performed before ES revealed that a possible ES agent, β-cyclodextrin exerts antiviral effect on enveloped viruses. However, biopolymers PVPVA64 and PVA-PEO were compatible with the tested viruses, thus we used these materials for fibre-forming. The results of the experiments showed that viruses more preserve their virulence during ES and subsequent storage if the solution used for their resuspension contains proteins, if the fibres are stored at 4°C, and especially if mannitol or sucrose is added to the fibre-forming medium. In the cases of both BoHV-1 and TGEV the direct reduction of the viral titres upon fibre-production was between 0.8-0.10 log10, using the appropriate settings and combinations. During a one-month-long storage of nanofibres, the infectious titre of the viruses decreased only slightly (BoHV-1, using mannitol) or remained stable (TGEV).

Based on our results, ES is a suitable method for the solid formulation of viruses – the process is well tolerated even by sensitive, enveloped viruses. Using the proper excipients this method may serve as alternative to freeze-drying and spray-drying in vaccine production. It provides a notable opportunity to enhance peroral and aerosol mass vaccinations of swine and poultry, and its use might also be considered under unfavourable environmental conditions (e.g. tropical countries).