Immunogenetic analysis of Trichinella spiralis infections in swine.

The immune responses of outbred swine, inoculated with several different low doses of Trichinella spiralis muscle larvae (ML), was followed over 5-6 weeks of primary infection, in order to determine an inoculation dose which could be used to identify genetic controls on the response to this helminth parasite. Reproducible infections were established when swine were inoculated with 100-300 ML. Humoral antibody responses to different larval stages were evident at 4 weeks using enzyme-linked immunosorbent assay (ELISA) of antibody-binding to excretory-secretory (ES) products of ML, and flow cytometric (FCM) analysis of antibody-binding to newborn larvae. T-cell blastogenesis to T. spiralis ML antigens was predominantly in the CD4+, class II restricted, T-cell subset. Having established an appropriate inoculation dose, swine leukocyte antigen (SLA) inbred miniature swine were then inoculated with this low dose of T. spiralis ML, to determine whether major histocompatibility complex (MHC) genes regulate swine immune responses to T. spiralis, as has been found in rodent models. Preliminary evidence indicated that swine of the SLA c/c haplotype may exhibit a lower burden of T. spiralis larvae in the tongue and diaphragm. This lower muscle burden correlated with the earlier development of a humoral antibody response in these genetically-defined swine.