Generic approaches to obtaining efficacious antigens from vector arthropods.

The development of vaccines to control ectoparasites is dependent upon the identification of key parasite antigens. While a rational, pragmatic approach to antigen identification has yielded a successful vaccine candidate from ticks, there may be problems with such an approach when dealing with other ectoparasites. As an alternative approach, the search for vaccine candidates may be facilitated by cloning and expressing parasite genes encoding proteins involved in key physiological roles. A number of criteria may be applied to short-list candidate vaccines, these being; (a) host antibodies should be able to gain access to the parasite antigen; (b) sufficient antibody must gain access to the antigen target; (c) the formation of antibody-antigen complex should disrupt the normal function of the parasite antigen (d) the antigen should share conserved structural/sequence motifs with related, characterised, proteins, thus allowing the use of recombinant DNA methods to clone and express the candidate antigen. We propose three major groups of parasite antigens which may fulfill these criteria; serine proteases, chemoreceptors/ion channels and neuropeptides.