Expression of Haemonchus contortus pepsinogen in Caenorhabditis elegans

A genomic copy of a gut-expressed Haemonchus contortus candidate vaccine antigen, pepsinogen, was isolated using the polymerase chain reaction (PCR). The isolated sequence was 4 kb in length and contained eight introns ranging in size from 54 to 1475 base pairs. This sequence, together with its 3' non-coding DNA region containing a polyadenylation signal sequence, was cloned into the Bluescript SK(+) vector immediately downstream of the Caenorhabditis elegans cpr-5 gene promoter. This promoter has been shown previously to direct protein expression to the gut of C. elegans. The construct was micro-injected into DR96 unc-76(e911) mutant C. elegans together with a rescue plasmid and transgenic worms identified by reversion back to wild-type phenotype. Two transgenic lines of C. elegans were established. The presence of the injected construct and of the Haemonchus pepsinogen transcript in transgenic worms was confirmed by PCR analysis. Correct splicing of intronic sequences was observed. Immunohistochemistry showed expression of the Haemonchus pepsinogen protein in the gut of transgenic C. elegans, with reactivity evident in the larval and adult stages. Expression of the Haemonchus pepsinogen in C. elegans affirms the role of C. elegans as a model for parasitic nematodes and demonstrates its potential as a vector for expression of candidate vaccine antigens from parasitic nematodes.