The effect of a novel vaccine candidate against Haemonchus contortus in sheep on the immunoglobulin G concentrations in the sheep sera

Haemonchus contortus is an important pathogenic haematophagous nematode affecting small ruminants and South American camelids worldwide. A key challenge in treating H. contortus infections is the increasing resistance to antiparasitic drugs. This project aimed to develop a new glycoengineered recombinant anti-H. contortus vaccine. To assess its efficacy, a randomised, controlled vaccine trial was conducted. As part of this, immunoglobulin G (IgG) responses were analysed in blood samples from five trial groups, including positive and negative controls, the commercial Barbervax® vaccine (BVAX group) and two variations of the new vaccine candidate: the glycoengineered form (GEA group) and the non-glycoengineered form (NEA group). This diploma thesis specifically focused on the analysis of IgG responses within the framework of the trial. Blood samples from the jugular vein were taken at 24 events during the trial. To demonstrate the changes in the immunoglobulin G concentrations in the sheep sera, a Haemonchus-specific and a vaccine-specific ELISA was performed. The GEA and NEA groups showed a similar Haemonchus-specific IgG response to the Barbervax® vaccine. In the GEA group the antibody titer was not significantly higher than in the NEA group. However, the increase in IgG concentration after challenge was twice as high as that oberserved in the NEA group. Furthermore, egg shedding and worm burden were lower in the GEA group, which strongly indicates that glycoengineering improves the efficacy of the new vaccine candidate. Both the GEA and NEA groups appeared to be effective in inducing vaccine-specific IgG antibodies. Further studies are needed to optimise the glycoengineered vaccine against H. contortus by investigating the most effective recombinant antigen isoforms, vaccine doses and schedules of immunisation. A recombinant vaccine produced using glycoengineering in insect cells could reduce the reliance on anthelmintic drugs and thereby slow the progressive development of parasite resistence. Consequently, it may improve animal health and welfare and contribute to the development of vaccines against other nematodes.