Antigenic shift during Trichinella cycle, consequences for vaccine developments

Parasites are complex pathogens, particularly in terms of their antigens, which can vary with life cycle stage and location in the host. Three main biological stages in Trichinella genus were described but it is an oversimplification of the complex Trichinella cycle. Trichinella antigens and immunodominant epitopes have been studied using various strategies requiring immunological reagents or the selection of specific gene targets to be expressed in several systems. Here, we review the Trichinella antigens used for vaccine development and their temporal and spatial variation with the parasite life cycle and in the parasite body. The first antigen studies were devoted to defining antigen profiles reacting with serum samples from various hosts. Trichinella antigens have been classified according to their immunoreactivity with different monoclonal antibodies obtained with various immunization protocols. Based on our knowledge of the Trichinella genome, specific targets have been evaluated. The first fully analyzed immunodominant epitope was s-tyvelose (3,6-dideoxy- d -arabinohexose), a carbohydrate initially found only in the Trichinella genus, but several other linear peptide epitopes have also been described. We discuss their use in vaccine developments taking into account the specific challenge of a foodborne zoonotic parasite. Recently, new data obtained from the use of recombinant antigens offer new challenges for vaccine development, but most studies focus only on rodent models and are far from the scale-up development stage. Adjuvants are of utmost importance in vaccine development and must be well designed to the target host. RNA vaccines may be more appropriate in the future. Ultimately, nematodes with an aborted cycle may be the ideal vaccine candidate in target animals with a local protective immune response and strong immunity, as in natural infection.