The red alga <i>Porphyridium</i> as a host for molecular farming: Efficient production of immunologically active hepatitis C virus glycoprotein.

Abstract

Microalgae are promising production platforms for the cost-effective production of recombinant proteins. We have recently established that the red alga <i>Porphyridium purpureum</i> provides superior transgene expression properties, due to the episomal maintenance of transformation vectors as multicopy plasmids in the nucleus. Here, we have explored the potential of <i>Porphyridium</i> to synthesize complex pharmaceutical proteins to high levels. Testing expression constructs for a candidate subunit vaccine against the hepatitis C virus (HCV), we show that the soluble HCV E2 glycoprotein can be produced in transgenic algal cultures to high levels. The antigen undergoes faithful posttranslational modification by N-glycosylation and is recognized by conformationally selective antibodies, suggesting that it adopts a proper antigenic conformation in the endoplasmic reticulum of red algal cells. We also report the experimental determination of the structure of the N-glycan moiety that is attached to glycosylated proteins in <i>Porphyridium</i>. Finally, we demonstrate the immunogenicity of the HCV antigen produced in red algae when administered by injection as pure protein or by feeding of algal biomass.