Submitted to: Animal Health Research Reviews
Publication Type: Proceedings
Publication Acceptance Date: September 21, 2003
Publication Date: January 5, 2005
Citation: Zarlenga, D.S. 2004. Vaccinating against zoonotic parasitic diseases: myth or reality? Animal Health Research Reviews 5:219-222.
Interpretive Summary: Co-evolution at the host-parasite interface has resulted in the selection of reciprocal systems of host adaptation and immune evasion that scientists have only just begun to appreciate. Consequently, the battle to produce functional, genetically engineered vaccines against parasites has met with lackluster success. To date, no commercially available vaccine exists for control or eradication of any human parasitic disease. Of the successful animal parasite vaccines that have been generated, most have been predicated upon fully viable or attenuated organisms rather than recombinant DNA technology. This approach is more a management tool in that the parasites usually are not cleared from the host following vaccination. This paper examines approaches that parasites have made to skirt both innate and antigen-specific adaptive immune responses and stresses the need to link genetic, proteomic and phylogenetic data with changes in parasite development and behavior i.e. the era of functional genomics, to make vaccine development more targeted than days gone by and propel this field to the levels of success once envisioned.
The largely unanticipated difficulties of parasite vaccine development have led us to a renewed awareness of the survival strategies evolutionarily embedded within parasites over hundreds of millions of years. We have grown to appreciate that efforts to disrupt parasite-host relationships are substantially compounded by our incomplete understanding of the complex immune responses that occur in the naturally-infected host. Given the inability to transfer laboratory successes to field trials, research is leading us to conclude that genetically-defined animal models may not be good predictors of the unique and disparate protective immune responses one can expect from the genetically-heterogeneous populations of animals that represent the parasite=s natural environment. This is further compounded by the abundance of mechanisms parasites have created for themselves to defend against immune intervention. Thus, in the never ending saga of vaccine development, it is only appropriate that pitfalls and advancements be critiqued as they apply across parasite groups, with a look toward promising technologies that may propel this field to the level of scientific achievement once envisioned.