2011 Annual Report
1a.Objectives (from AD-416)
1. Develop serological assays that differentiate swine chronically infected with zoonotic T. spiralis from swine only transiently exposed to T. murrelli.
2. Estimate how frequently pastured pigs and feral swine are exposed to infection with enzootic and zoonotic species of trichinella.
1b.Approach (from AD-416)
Screen expression libraries of T. spiralis and T. murrelli with hyper-immune sera from swine to identify clones encoding species-specific diagnostic antigens. Develop antibodies that discriminate among the two types of infection. Test in experimentally infected swine. Apply to panels of serum collected from feral swine and pastured pigs. Validate against genotyped parasite specimens obtained from tissue samples matched with serum.
This work was initiated in April in order to develop serological assays to differentially diagnose swine exposure to Trichinella spiralis or Trichinella murrelli. The reason for doing so is that swine exposed to T. spiralis are likely to harbor abundant, life-long larval burdens posing significant risk to food safety, whereas swine exposed to T. murrelli generally mount successful immune responses; current methods to screen serum, however, make no distinction between the two conditions. In the few months since initiating this project, much progress can already be reported. A visiting scientist was recruited to commence experimental infections intended to procure needed numbers of larvae of each parasite type. Crude extracts, and preparations of Excretory-Secratory products (containing immunodominant antigens) were obtained. Peptides from each were fluorescently labeled and run on 2D gels, transferred to membranes, and probed with hyperimmune serum from pigs harboring infections with one or the other infection. In addition to a large suite of shared epitopes, these experiments have identified candidate constituents which may prove to be specific to one of the two parasites, and recognized by the immune repertoire of swine. In the future, we intend to sequence, clone, and express candidate loci in order to test their suitability as the basis for specific immunoscreening reagents. Meanwhile, working with our APHIS partners and using summer students hired for this purpose, we have commenced screening of swine sera in order to identify farmed and feral animals harboring antibodies to either of these zoonotic parasites. Pending completion of our reagent development, these sera (and their matched tissue samples) will provide a means to validate our diagnostic test and help characterize the regional epidemiology of each agent. This collaboration was coordinated via in-person meetings among all three coordinators and regular interaction with staff, via phone meetings with our APHIS collaborators, and by written communication via emails; a progress report was delivered at the Project Director’s Meeting, July 29th, 2011, accompanied by a poster presentation.