Nucleic acid vaccines methods

Although some cells in skin, muscle, brain, and so on can spontaneously take up exogenous injected naked pDNA or mRNA [18], this process is relatively inefficient and can consequently be used only when a local expression of a protein is desired, i.e., for vaccination. Even if physical methods exist to enhance the uptake of naked nuclei acids (electroporation or hydrodynamic delivery see Section 1222), increasing the efficacy of transfection in vivo is best reached using encapsulation of the nucleic acids. Two methods are used cationic polymers or liposomes. 

In current practice the fluorescence assay is often followed by the use of hybridization techniques when more selectivity is required. We have for instance used the fluorescence techniques to obtain data on the nucleic acid content of malaria vaccine proteins produced in Escherichia coli. The rapid turnaround time of the fluorescence assay is particularly useful during the early stages of purification to determine the optimal process conditions. After the final process has been arrived at and a variety of methods used to assess the nucleic acid content (including the hybridization techniques), the fluorescence method can be developed for routine quality-control purposes. In certain cases, particularly at high protein concentrations, the dye may bind to the protein with... 

Heat is the most reliable method of virus disinfection. Most human pathogenic viruses are inactivated following exposure at 60°C for 30 minutes. The virus of serum hepatitis can, however, survive this temperature for up to 4 hours. Viruses are stable at low temperatures and are routinely stored at -40 to -70°C. Some viruses are rapidly inactivated by drying, others survive well in a desiccated state. Ultraviolet light inactivates viruses by damaging their nucleic acid and has been used to prepare viral vaccines. These facts must be taken into account in the storage and preparation of viral vaccines (Chapter 15). 

The use of needle-free jet devices for the delivery of nucleic acids has been described for various disease models, and has been found to generally enhance DNA uptake in various tissues and to increase DNA vaccine efficacy. Jet injection has been found to be an efficient method to induce papillomas in rabbits by inoculation with cottontail rabbit papillomavirus DNA (Brandsma et al., 1991). Jet injection has been used to introduce DNA through the skin surface, effectively transfecting skin, muscle, fat and mammary tumor tissue (Furth et al., 1992). 

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