Assay to compare cell-and antibody-mediated immune responses in domestic sheep and goats

Authors: HERNDON, MARIA - Washington State University; White, Stephen; Mousel, Michelle

Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2020
Publication Date: 9/22/2020
Citation: Herndon, M.K., White, S.N., Mousel, M.R. 2020. Assay to compare cell-and antibody-mediated immune responses in domestic sheep and goats. Veterinary Immunology and Immunopathology. 230. Article 110125. https://doi.org/10.1016/j.vetimm.2020.110125.
DOI: https://doi.org/10.1016/j.vetimm.2020.110125

Interpretive Summary: Livestock producers need means to combat infectious diseases that do not rely on antibiotics, antivirals, or antihelmintics. One method is genetic selection however when selecting for resistance or resilience to one infectious disease, producers may be inadvertently increasing the susceptibility to other infectious diseases. Determining how strong or weak the immune response is to intra- and extracellular stimulants may help balance a flocks' or herds' ability to prosper while conducting marker assisted selection for disease resistance or resilience. We evaluated a methodology used in cattle and pigs that measures the immune response, in sheep and goats. The first study determined that subcutaneous injection in sheep would produce a similar antibody and skin depth response as intramuscular injection. The second study indicated that the location of the subcutaneous injection, neck or axillary space, also produced similar immune responses allowing for flexibility in light of a valuable wool clip. The third study confirmed the methodology developed for sheep would detect variable immune responses in goats and that lymphocyte counts were greater for goats who had the lowest skin depth response. This work paves the way to provide producers a method to measure the immune fitness of their flock or herd and thereby make decisions to sustain a flock or herd capable of invoking a balanced response to locally prevalent infectious pathogens.

Technical Abstract: The ability to assay the immune fitness of sheep and goats is critical in determining immune consequences of selecting animals for increased disease resistance or resilience. Selection for animals with decreased susceptibility to one disease may in fact produce animals with an unbalanced cell mediated versus humoral immune response as that single disease may be fought primarily by a single arm of the immune system. Therefore, selecting for a strong response in one arm may result in animals with an unbalanced response system. The main objective of this study was to verify if a methodology used in cattle and pigs would also successfully measure both the humoral and cell mediated immune response in sheep and goats allowing for assessment of the immune response. Depth of injection, intramuscular or subcutaneous, of two antigens, Candida albicans and hen egg white lysozyme, were compared in sheep to determine if there was a difference in antibody production or cell-mediated immune response. Subcutaneous injection produced a larger (P=0.0031) antibody response, no differences (depth, P=0.2045; diameter, P=0.4537) were observed in the cell mediated response. Finally, methodology was confirmed in goats. Animals were categorized into high and low response groups to aid in the comparison of an animal’s immune fitness and complete blood cell counts were performed to compare leukocyte cell differences between the responder groups. This work paves the way to provide producers a means to measure the immune fitness of their flock and thereby make decisions to maintain a flock capable of invoking a balanced response to all pathogens.