Heterologous Prime-Boost Immunisation Regimens Against Infectious Diseases

Development of prophylactic vaccines against infectious diseases (such as malaria, tuberculosis and HIV) has been hindered by the lack of effective immunisation strategies that induce the cellular arm of the immune system necessary for protection against these intracellular pathogens. DNA vaccines, recombinant proteins and recombinant viral vectors are all effective antigen delivery systems for inducing cellular immunity. However, when used alone, the levels of specific immune response they induce is often low. Heterologous prime – boost immunisation strategies involve using two different vaccines, each encoding the same antigen. In the past decade, numerous published reports have demonstrated that such prime – boost immunisation strategies effectively enhance cellular immunity in several different animal and disease models. Since several intracellular pathogens are considered potential biowarfare threats, the objective of this review is to assess whether prime-boost vaccination is likely to be effective in protecting against those intracellular pathogens of defence interest. This review focuses on heterologous prime – boost immunisation studies using DNA vaccines as the priming vehicle followed by either recombinant protein or recombinant viral vector boost. Included is a summary of studies up to July 2005, for a number of diseases. This paper evaluates if this approach may be applied to those intracellular pathogens considered a threat to the ADF in our vaccine development program.