Helminth vaccines: from mining genomic information for vaccine targets to systems used for protein expression

Phenotype of hepatic infiltrates and hepatic lymph nodes of lambs primarily and challenge infected with Fasciola hepatica, with and without triclabendazole treatment

“…In recent years much attention has been focused on the study of vaccination strategies as an alternative to chemotherapy for the control of the disease due to the high cost of repetitive chemical treatments, drug-resistance and the hazard of chemical residues in food and the environment [8,9,29]. Resistance to reinfection and host response to F. hepatica vary greatly between species [12].…”

“…However, more recent studies have demonstrated that some immunisation protocols induce a significant protective response against challenge infection in sheep [1,25] and cattle [19,20]. Therefore, there are many questions concerning the immunological basis of susceptibility and resistance in sheep that should be elucidated [1,8,9,18].…”

Recombinant expression systems: the obstacle to helminth vaccines?

“…The advantages and disadvantages of each system have been discussed in detail in Ref. [4] and are summarized in Box 1. The bacterial expression system has been by far the most popular choice to express helminth antigens.…”

“…An additional problem with E. coli is that much of the recombinant protein generated can end up in insoluble inclusion bodies. As a consequence, use of eukaryotic expression systems, such as yeast and baculovirus, has been proposed to address these problems with the bacterial recombinants [4]. However, there is little experimental evidence that the protective capacity of recombinant helminth antigens actually improves by switching from a bacterial to a eukaryotic expression system.…”

“…The yeast Saccharomyces cerevisiae, for example, can cover the peptide core with very large glycan trees, which potentially mask important peptide epitopes [4] or which can make the protein hyperantigenic [10]. This seemed to be the case with the yeast-expressed F. hepatica cathepsin L3, which induced less protection compared with the baculovirus-produced version, despite the fact that both recombinants induced comparable serological responses [8].…”