Thermolability of complex biological molecules is a major consideration for the long-term maintenance of titer during periods of storage.

The development of a simple, cost effective method for long term storage of virus samples, which maintains viral titer would prove useful for a wide variety of applications including the preservation of viral vaccines, and is paramount for alleviating the reliance upon the cold chain.

We have investigated the potential use of a method adapted for this purpose originating from a natural mechanism used by plants which helps to maintain the integrity of seeds, enabling them to overcome extensive periods of temperature elevation and desiccation.

As maturation of a seed progresses, many complex biological macromolecules are laid down which maintain the germination potential. Sucrose and raffinose (in addition to other oligosaccharides) are commonly found to accumulate. In addition highly charged protein molecules accumulate, Late Embryogenesis Abundant (LEA) proteins, reaching their maximal level when the seed is most desiccation and thermally tolerant, and indeed are among the first molecules to be lost when germination is initiated.

We have examined the potential use of sucrose and raffinose in concert with chemical replacements for the LEA, which when dried with the active product forms an amorphous solid able to maintain the titer of infectious Adenovirus at elevated temperatures for extended periods, in the case of lyophilized presentations several months at 37 °C, or as liquid, stability for several weeks at 37 °C was achieved.

We demonstrate that after embedding the active product in the matrix, the viral titer is preserved even at temperatures for relatively extended periods at temperatures significantly greater than ambient.

In addition we believe that these results could open the way for a new type of vaccine which we refer to as a hybrid stability vaccine, whereby for the first time the same excipient components are used to confer stability in both liquid and solid forms (albeit at different concentrations) which may ultimately result in a stable vaccine which has a very high stability index whilst dry, whereas upon reconstitution using nothing more than WFI at proscribed volumes, the vaccine would benefit from having much improved stability during the administration procedures.

This paper describes the use of Adenovirus (itself fast becoming a vector of choice for a new generation of vaccines) as a model system, and identifies non-toxic, inexpensive excipients which are compatible with current manufacturing processes which could be instrumental in removing the dependence upon the cold chain.

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