Authors

E Hanks³; A Van Diepen¹; D Smith²; G F Newlands²; S Burgess²; D P Knox²; A J Nisbet²; T N McNeilly²; C Hokke¹; C Britton³;  ¹ Leiden University Medical Centre, Netherlands;  ² Moredun Research institute, UK;  ³ University of Glasgow , UK

Discussion

Haemonchus contortus is a highly pathogenic, blood feeding gastrointestinal nematode of small ruminants. High levels of protective immunity can be achieved against challenge infection by vaccinating sheep with the native H. contortus gut glycoprotein vaccine Barbervax. Previous studies have shown that vaccination induces high antibody titres to two main glycoproteins present in Barbervax, aminopeptidase H11 and the H-gal-GP complex. Approximately 90% of the antibody reactivity is targeted towards glycan components of these glycoproteins. To identify the specific glycan structures recognised by host antibody following vaccination, glycan array screening was carried out. Arrays were printed with Barbervax glycans fractionated by HPLC and screened with serum from 56 vaccinated lambs, predominantly from field trials carried out in Australia. These lambs all showed high levels of anti-Barbervax IgG based on ELISA titre at peak H. contortus challenge. From the serum recognition profiles, we identified a number of glycans that were recognised consistently by serum from these lambs. We examined any relationships between level of IgG binding to specific glycan fractions and three measures of protection to H. contortus infection: mean faecal egg count throughout the trials, antibody titre at peak challenge and change in haemoglobin level during the trials. We identified a small number of glycan fractions which were significantly related to protection. Synthetic glycans were also included on the arrays and synthetic LDNF was strongly recognised by some of this cohort. Further work is underway to determine the structures of the immunogenic Barbervax glycans and to examine whether specific glycans of interest may be involved in inducing protective immunity. This is important in identifying the mechanisms of vaccine-induced immunity to H. contortus and in development of a future synthetic vaccine.