Haemonchus contortus transthyretin domain - containing protein (HcTTR): A promising vaccine candidate against Haemonchus contortus infection

Authors: TIAN, XIAOWEI - Nanjing Agricultural University; LU, MINGMIN - Nanjing Agricultural University; JIA, CAIWEN - Nanjing Agricultural University; BU, YONGQIAN - Nanjing Agricultural University; AIMULAJIANG, KALIBIXIATI - Nanjing Agricultural University; ZHANG, YANG - Nanjing Agricultural University; Li, Charles; YAN, RUOFENG - Nanjing Agricultural University; XU, LIXIN - Nanjing Agricultural University; LI, XIANGRUI - Nanjing Agricultural University

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2020
Publication Date: 3/1/2020
Publication URL: https://handle.nal.usda.gov/10113/6830166
Citation: Tian, X., Lu, M., Jia, C., Bu, Y., Aimulajiang, K., Zhang, Y., Li, C.Z., Yan, R., Xu, L., Li, X. 2020. Haemonchus contortus transthyretin domain - containing protein (HcTTR): A promising vaccine candidate against Haemonchus contortus infection. Veterinary Parasitology. https://doi.org/10.1016/j.vetpar.2020.109045.
DOI: https://doi.org/10.1016/j.vetpar.2020.109045

Interpretive Summary: Haemonchosis, one of the most economically important diseases in small ruminants, is caused by gastrointestinal nematode -Haemonchus contortus parasites worldwide. The occurrence of drug resistant worms, the concerns about chemical residues in food, and the potential negative impact on the environment, emphasize the importance of alternatives to control the worms. Prophylaxis against this parasite infection by vaccine should possibly be the most efficient approach to protect animals. Haemonchus contortus transthyretin domain-containing protein (HcTTR) may have a potential used for vaccine development against the infection of H. contortus. In this study, the protective capacities of HcTTR against H. contortus infections via active and passive immunization trials were examined. For the passive protection trials, H. contortus-infected goats were intravenously immunized twice with 5 mg of total IgG containing anti-rHcTTR goat polyclonal antibodies. The results showed that the significant rates of reduction in egg shedding and worm burden was 58.12% and 64.61%, respectively, as compared with the positive control group. For the active protection trials, local goats were vaccinated twice with 500 µg of recombinant HcTTR to generate antigen-specific circulating antibodies, resulting in 63.7% reduction in eggs shedding and 66.4% reduction in worm burdens after H. contortus challenge. In both passive and active trials, the immunized goats displayed higher mucosal IgA levels and less anaemic compared to the challenged positive controls. Pen trials indicated that HcTTR generated partial immune protective effects against H. contortus challenge and it could be a promising vaccine candidate for development of effective strategy to control H. contortus.

Technical Abstract: Haemonchus contortus transthyretin domain-containing protein (HcTTR) with 136 amino acids belongs to a transthyretin-like (TTL) family member. In our previous study, it was reported that HcTTR was a novel antagonist of the goat cytokine Interleukin 4 (IL-4), and was involved in the regulation of host immune responses, implying that it might be applied for therapeutic strategies or vaccine development against the infection of H. contortus. Thus, the protective capacities of HcTTR against H. contortus infections via active and passive immunization trials were examined. For the passive protection trials, H. contortus-infected goats were intravenously immunized twice with 5 mg of total IgG containing anti-rHcTTR goat polyclonal antibodies. The results showed that the significant rates of reduction in egg shedding and worm burden was 58.12% and 64.61%, respectively, as compared with the positive control group. For the active protection trials, local goats were vaccinated twice with 500 µg of recombinant HcTTR to generate antigen-specific circulating antibodies, resulting in 63.7% reduction in eggs shedding and 66.4% reduction in worm burdens after H. contortus challenge. In both passive and active trials, the immunized goats displayed higher mucosal IgA levels and less anaemic compared to the challenged positive controls. Pen trials indicated that HcTTR generated partial immune protective effects against H. contortus challenge and it could be a promising vaccine candidate for development of effective strategy to control H. contortus.