Effects of interferon tau and pregnancy specific protein B on gene expression during early pregnancy.
Open Access
- Author:
- Montgomery, Ty
- Graduate Program:
- Animal Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 22, 2022
- Committee Members:
- Adele Turzillo, Program Head/Chair
Troy Ott, Thesis Advisor/Co-Advisor
Joy Lee Pate, Committee Member
Chad Daniel Dechow, Committee Member - Keywords:
- maternal recognition of pregnancy
HSPE1
D2Dx Immunity Test
pregnancy associated glycoproteins - Abstract:
- Animal agriculture has selected for traits that increased production, improved profitability, but often disregarded animal fertility. Most reproductive failure is attributed failure of fertilization or early embryonic death. Implementation of estrus synchronization and timed artificial insemination have improved pregnancy rates in the dairy industries, but 60% of cows still required multiple artificial inseminations to calve. Approximately 40% of failed pregnancies are the result of early embryonic death with most of this loss occurring between fertilization and day 16 of the pregnancy. A deeper understanding of early pregnancy is needed to determine the cause of infertility in beef and dairy herds. This research focused on the effects of conceptus secretions on local and systemic transcription of early pregnancy factor (EPF/HSPE1) and differences in immune status between cows and heifers. Pregnancy success depends on communication between the embryo and maternal endometrium. In cattle, interferon tau (IFNT) is a primary conceptus-derived protein (days 8 to 30) known to induce luteal maintenance, a requirement for pregnancy success. IFNT regulates gene expression in the endometrium and peripheral blood leukocytes. Shortly after the onset of IFNT production, the conceptus secretes pregnancy associated glycoproteins (PAG; day 17 to calving) in high concentrations. However, the function of PAG remains unknown. One of the earliest maternal responses to pregnancy is transcription of heat shock protein family E member 1 (HSPE1). Originally termed early pregnancy factor, HSPE1 is produced by the ovary and present in blood serum 6 to 24 hours after mating. It is continuously synthesized throughout early pregnancy by the ovary and oviducts. Furthermore, embryos fail to attach when the mother is immunized with anti-HSPE1 antibodies. This study tested the hypothesis that IFNT and/or PAG modulate expression of HSPE1 in the uterus, corpus luteum, and peripheral blood leukocytes. Holstein heifers (n=6/treatment) were estrous (day 0) synchronized and received twice daily intrauterine infusions of 20 mL of saline including one of the following treatments: 200 μg/mL BSA from day 14 to 16 (vehicle control); vehicle + 200 μg IFNT from day 14 to 16; vehicle + 200 μg IFNT from day 14 to 19; vehicle + 200 μg IFNT from day 14 to 19 + 100 μg PSPB (a mixture of PAG isolated from mid-gestation bovine placenta) from day 17 to 19. Blood was collected daily, and the corpus luteum and an endometrial biopsy was collected at the end of the treatment period. Real-time quantitative polymerase chain reaction was used to quantify HSPE1 expression. Data were analyzed using the MIXED procedure in SAS, and the model tested the effects of treatment, day, and their interaction were applicable. Abundance of HSPE1 in endometrium did not differ between short-term BSA and BSA+IFNT treatments (P=0.82). Similarly, there was no difference in HSPE1 expression between long-term BSA+IFNT and BSA+IFNT+PAG treatments in endometrium (P=0.22). In the corpus luteum, there was a tendency for lower (P=0.07) HSPE1 expression in the three-day BSA+IFNT treatment compared to heifers infused with vehicle. Interestingly, abundance of HSPE1 in the corpus luteum was lower (P=0.04) after six-day BSA+IFNT+PAG treatment compared to six-day BSA+IFNT treatment. There was a main effect of day on HSPE1 in PBL expression over the duration of three-day treatments (P=0.01). There was a treatment by day interaction on HSPE1 expression over the duration of the six-day treatments (P<0.01). Relative to the first day of treatment, there was a 4-fold increase in HSPE1 expression after six days of BSA+IFNT treatment (quadratic, P<0.01). On the other hand, there was no change in HSPE1 expression throughout the BSA+IFNT+PAG treatment (quadratic, P=0.8). These results indicate that HSPE1 expression is suppressed in the corpus luteum, and it may be modulated in peripheral blood leukocytes. Further work is needed to confirm how pregnancy affects HSPE1 expression and if it important for pregnancy establishment. Our lab hypothesizes cows experience inflammation over their life which contributes to the decreased fertility in cows compared to heifers. An adaptive immune response that is mediated by TH2 cells promotes the differentiation of B-cells and production of immunoglobulins. In a process called class switching, B-cells will shift production of IgM antibodies to producing IgG, IgE, or IgA. It was demonstrated that class switch occurs during pregnancy in humans and mice, and there is preliminary evidence class switching occurs in cattle. This study tested the hypothesis that immunoglobin subtypes in systemic circulation differ between pregnant and cyclic cows and heifers due to the shift to TH2-mediated immunity during pregnancy. A novel diagnostic assay platform, the D2Dx immunity test, was used to assess the ratio of immunoglobin G (IgG) subclasses 1 and 2 (indicated by a change in absorbance) in blood serum. There was no effect of pregnancy status (P=0.99) on the change in absorbance of blood serum. Likewise, change in absorbance did not differ between serum collected at estrus (day 0) and serum collected 17.5 days later (P=0.49). There was a main effect of parity (P=0.01) on the ratio of IgG subtypes as measured by the D2Dx immunity test, as there was a greater change in absorbance in cows than heifers. Our unpublished results demonstrated the overall pregnancy rate for this experiment was 53%, but heifers had a greater pregnancy rate (68%) than cows (42%). We found the higher the D2Dx score correlated to decreased pregnancy rate. Little is known about the role of immunoglobulins during early pregnancy. Future work is needed to determine how differences in antibody subclasses between cows and heifers affect fertility.