Immunization with recombinant haemonchus contortus Y75B8A.8 partially protects local crossbred female goats from haemonchus contortus infection

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

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2022
Publication Date: 4/4/2022
Citation: Tian, X., Lu, M., Bu, Y., Zhang, Y., Aimulajiang, K., Liang, M., Li, C.Z., Yan, R., Xu, L., Song, X., Li, X. 2022. Immunization with recombinant haemonchus contortus Y75B8A.8 partially protects local crossbred female goats from haemonchus contortus infection. Frontiers in Veterinary Science. 9:765700. https://doi.org/10.3389/fvets.2022.765700.
DOI: https://doi.org/10.3389/fvets.2022.765700

Interpretive Summary: Haemonchosis, caused by parasite Haemonchus contortus, is one of the most important parasitic diseases of livestock worldwide, causing great losses of $ billions to the ruminant (sheep and goats) industry annually. One of this parasitic products (called Hc8) derived from H. contortus excretory–secretory (ES) products was identified as a functional inhibitor to inhibit the goat important interleukin-2 which is a type of molecule in the immune system and regulates the activities of white blood cells responsible for immunity. Hc8 may have the potential to be a vaccine candidate for the development of therapeutic strategies against H. contortus infection. In this research, recombinant Hc8 (rHc8) protein and goat anti-rHc8 specific antibodies were both employed to evaluate the protective capacities of Hc8 antigen against H. contortus infections. When the goats were vaccinated with this recombinant protein Hc8 twice to 9–12-month-old female goats with a 2-week interval, high levels of antigen-specific antibodies in blood and mucosa were produced. Compared with the challenged control, the vaccinated groups had more protection against parasitic challenges, as fecal egg worm burdens were reduced by more than 55%. When the goats were immunized with specific anti-Hc8 goat antibodies twice, worm burden was reduced by less than 46%. It seems that active immunization (with vaccine protein) could induce long-term protection, whereas passive immunization (injected with a specific antibody) confers short-term protection. These preliminary results demonstrated the Hc8 antigen may be useful in developing subunit recombinant vaccines against H. contortus.

Technical Abstract: Haemonchus contortus Y75B8A.8 (Hc8) derived from H. contortus excretory–secretory (ES) products was identified as a functional inhibitor of goat interleukin 2 (IL-2). It may act as a vaccine candidate for the development of therapeutic strategies against H. contortus infection. In this research, recombinant Hc8 (rHc8) and goat anti-rHc8 polyclonal antibodies were employed to evaluate the protective capacities of Hc8 antigen against H. contortus infections via active and passive immunization trials, respectively. In both trials, local crossbred female goats aged 9–12 months old were randomly divided into three groups, five in each group, respectively. Parasitological examinations, including fecal egg counts (FEC), cumulative FEC (cFEC), and worm burdens, were performed. In addition, antibody levels in mucosal homogenate (MH) samples and hematological and immunological parameters were detected. In the passive trial, goats were intravenously immunized with 5 mg total IgG containing anti-rHc8 goat polyclonal antibodies. After twice immunization, compared with the challenged control group, cFEC was reduced by 39%. In addition, there was a 46% reduction of worm burdens compared with the challenged controls. In the active immunization trials, 500 µg of recombinant Hc8 protein was given subcutaneously twice to 9–12-month-old local crossbred female goats with a 2-week interval, resulting in the generation of high levels of antigen-specific circulating antibodies. Besides, cFEC and abomasal worm burden were reduced by 70 and 55%, respectively, compared with the challenged control group. In addition, immunized goats had higher mucosal homogenate IgA and hemoglobin levels than the challenged controls in both passive and active immunization trials. These preliminary results demonstrated the immunoprophylactic effects of Hc8 antigen and will inform new studies on ES proteins in developing subunit recombinant vaccines against H. contortus.