Role of oligosaccharides in the immune response of sheep vaccinated with Lucilia cuprina larval glycoprotein, peritrophin-95

The larvae of the fly Lucilia cuprina cause a cutaneous myiasis in mammalia n hosts, particularly sheep. The glycoprotein, peritrophin-95, isolated fro m Lucilia cuprina larval peritrophic matrix, is a candidate vaccine antigen . This protein induced an immune response in vaccinated sheep that inhibite d larval growth. Recombinant forms of peritrophin-95 were produced in bacte ria and baculovirus-infected insect cells. The bacterial protein was not gl ycosylated and incorrectly folded whereas the insect cell-expressed protein was glycosylated and probably correctly folded. Sheep immunised with purif ied native peritrophin-95 generated strong larval growth inhibitory activit y in their sera, whereas sheep immunised with either recombinant form of pe ritrophin-95 generated only relatively weak inhibitory activity. Ingested o vine antibodies to native peritrophin-95 mediated the anti-larval growth ac tivity and this was independent of the presence of ovine complement. The ac tivity was associated with IgC(1) and IgG(2) but not IgM. There were strong antibody responses to both the correctly folded native peritrophin-95 poly peptide and the oligosaccharides present on this glycoprotein. Immune-affin ity isolation of antibody to the peritrophin-95 polypeptide and antibody to peritrophin-95 oligosaccharides demonstrated that the larval growth inhibi tory activity resided with both antibodies. Lectin blots and ELISA data sho wed substantial differences between the oligosaccharides attached to native peritrophin-95 and insect cell-expressed recombinant peritrophin-95. It wa s concluded that the oligosaccharides attached to native peritrophin-95 and its unique polypeptide structure are essential for the induction of larval growth inhibitory activity in the sera of sheep vaccinated with this antig en. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Science ltd. All rights reserved.