PSV-B-14 - Bovine Luteal Cell Apoptosis Following Administration of a Commercial Inactivated or Modified-live Virus Vaccine at Time of AI

Abstract: Damage to the bovine corpus luteum (CL) has been reported following modified-live virus vaccination (MLV). The objective of this study was to investigate the degree of luteal apoptosis after MLV or inactivated vaccine (IV) administration at time of artificial insemination. Beef females were estrous synchronized and on d 0 were vaccinated with a MLV or IV after being transrectally ultrasounded to record presence and location of dominant follicles and CL. Thirteen cows (MLV, n=7; IV, n=6) were selected on d 10-13 across treatment based on dominant follicle size and estrus expression for ovariectomy. Ovaries were obtained and CL were frozen in OCT and sectioned for immunohistochemistry analysis. At the time of ovary collection, some MLV animals had two CL. These were characterized into old or new CL, relative to if ovulation had occurred in response to the synchronization protocol or afterward due to an abnormal cycle, respectively. For immunohistochemistry analysis, two nonconsecutive sections were evaluated for apoptosis using a TUNEL staining kit (ab66110) according to manufacturer’s instructions, with the modification of DAPI being used as a cell marker. Two random fields of view from each section were photographed with a Keyence BZ-X810 microscope and were evaluated for number of total and apoptotic cells. The GLIMMIX procedure of SAS was utilized to analyze percentage of apoptotic cells with image included as a random effect. Percentage of apoptotic cells were affected by treatment (P < 0.0001). MLV-new CL had the greatest percentage (35.56 ± 5.5%) of luteal cell apoptosis, while MLV-old CL (7.05 ± 4.6%) and IV (4.24 ± 4.9%) were similarly decreased. In summary, a greater degree of apoptosis in new CL which formed after an abnormal cycle following MLV administration indicates the ability of MLV to induce estrous cycle dysfunction and extend its effects to luteal cell development and function.