Progress toward molecular characterization of ectoparasite modulation of host immunity

Ectoparasitic arthropods and vector-borne infectious agents are global medi cal and veterinary public health concerns. Economic impact due to direct ef fects of infestation and disease transmission are significant. These proble ms are increased by development of arthropod resistance to insecticides/aca ricides; drug resistance of vector-borne pathogens; and, lack of effective vaccines to prevent many of these diseases. There is much to be gained from understanding the complex array of immunological interactions occurring at the arthropod-host-pathogen interface. One application of that knowledge i s the development of novel vaccines for the control of both ectoparasitic a rthropods and the diseases they transmit. We now realize that blood-feeding arthropods are not simply flying or crawling hypodermic needles and syring es. Ectoparasitic arthropods are not passive partners in their relationship s with the immune systems of their hosts. These clever invertebrates produc e numerous pharmacologically active molecules that help them migrate throug h tissues of their hosts or to successfully obtain blood meals. Arthropod p arasites stimulate a spectrum of host immune responses that could potential ly impair development, reduce feeding success, or kill the ectoparasite. No t unexpectedly, arthropods have developed sophisticated arsenals of counter measures that modulate or deviate host immune responses, Not only does arth ropod modulation of host immunity facilitate survival in tissues or increas e the likelihood of obtaining a blood meal, but it is increasingly recogniz ed as a critical factor in pathogen transmission. Those countermeasures to host immune defenses are the topics of this review. Emphasis is placed on o ur current understanding of the molecular bases of those changes; the molec ules responsible for host immunomodulation; contemporary approaches for stu dying these complex relationships; and, the potential for using this inform ation to develop innovative vaccine-based control strategies. (C) 2001 Else vier Science B.V. All rights reserved.