Pregnancy-associated glycoprotein levels in pregnant goats inoculated with Toxoplasma gondii or Listeria monocytogenes: a retrospective study

Effect of ambient lead on progesterone and pregnancy-associated glycoprotein 1 and their relationship with abortion in Zaraibi goats: a field study

This study aimed to investigate the impact of ambient lead (Pb) exposure on progesterone (P4) and pregnancy-associated glycoprotein 1 (PAG1) and their relationship with abortion in Egyptian Zaraibi goats (C. hircus). To achieve this, 40 female goats (does) were mated with highly fertile male goats, resulting in a total of 28 pregnant goats. Eight of them aborted, and each of the 12 pregnant goats gave birth to one kid, whereas the remaining eight gave birth to twins. The levels of PAG1, P4, and Pb in serum were estimated by enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), and inductively coupled plasma mass spectrometry (ICP-MS) respectively. Statistically, the repeated measure two-way ANOVA, regression analysis, correlation coefficient, and receiver operating characteristic (ROC) curves were applied. The current data demonstrated that the levels of blood Pb in aborted goats were significantly higher than those in non-aborted goats at the early, mid, and late gestations, and this was followed by significant decreases in serum PAG1 and P4. Furthermore, there were substantial inverse associations between blood Pb concentration and levels of PAG1 and P4, with markedly negative correlation coefficients of - 0.88 and - 0.77, respectively, in aborted goats. The threshold level of Pb required to cause abortion was ≥ 32.08 μg/dl, but for PAG1 and P4 were respectively ≤ 0.95 ng/ml and ≤ 0.48 ng/ml. Additionally, threshold levels of ≥ 12.34 ng/ml and ≥ 31.52 ng/ml for P4 and PAG1, respectively, were needed to deliver twins. In conclusion, pollution-induced increases in Pb bioavailability resulted in dramatic decreases in P4 and PAG1 levels, leading to abortions. PAG1 and P4 levels are also key factors in determining whether Zaraibi goats will give birth to twins.

Using Pregnancy-Associated Glycoproteins (PAGs) to Improve Reproductive Management: From Dairy Cows to Other Dairy Livestock

Simple Summary

Pregnancy loss is a major cause of infertility in dairy animals, particularly in cattle, which affects the productivity and profitability of farms. Detecting these unsuccessful pregnancies could offer farmers the opportunity to reduce the economic damage caused by pregnancy loss. The determination of proteins secreted by the placenta and related to the presence of a viable conceptus called pregnancy-associated glycoproteins (PAGs) represents a diagnostic tool to identify pregnant or non-pregnant animals and to predict early pregnancy failures. This review describes the state of the art related to PAGs’ function, pregnancy profile, and use in reproductive management in bovine and other dairy livestock.

Abstract

Pregnancy success represents a major issue for the economic income of cattle breeders. Early detection of pregnant and non-pregnant animals, as well as the prediction of early pregnancy failure, can influence farm management decisions. Several diagnostic tools for pregnancy are currently available. Among these, pregnancy-associated glycoproteins (PAGs) have been shown to be useful for identifying the presence of vital embryos and for pregnancy follow-up monitoring. This review presents an overview of the PAGs’ functions, their pregnancy trends, and their use as a tool to improve reproductive management in bovine and other dairy livestock, such as small ruminants and buffalos.

Identification of pregnancy-associated glycoprotein family (PAG) in the brown bear (Ursus arctos L.)

Pregnancy-associated glycoproteins (PAGs) are abundant embryo-originated products expressed in the pre-placental trophoblast and, later, in the post-implantational chorionic epithelium of some mammalian species. This paper describes the identification and cellular immunolocalization of the chorionic PAG family in the discoidal-type placenta of the brown bear (Ursus arctos L. - Ua), in which the PAGs were named 'UaPAG-Ls'. The study used: 1) Western blot for total placental glycoproteins; and 2) cross-species heterologous double fluorescent immunohistochemistry (IHC) for cellular immune-localization of the PAGs. This is the first study reporting the identification and immunolocalization of the UaPAG-L family in placental cells during early pregnancy in the brown bear. Our Western analysis revealed a dominant mature 72 kDa UaPAG-L isoform was expressed in all Ua placentas during early pregnancy. Various other UaPAG-L isoforms (16-66 kDa) were also identified. Using IHC, the UaPAG-L proteins were localized to trophectodermal cells (TRD), where signal intensity resembled intense TRD proliferation within developing placenta. The data increases our general knowledge of PAG proteins localized in discoidal-type placenta during early pregnancy in the brown bear.

Using beef-breed semen in seropositive dams for the control of bovine neosporosis

A program for controlling bovine neosporosis based only on the use of beef semen, without culling seropositive animals, was evaluated in a closed dairy cattle herd over a 5-year period (2013-2017). The program was based on individual and periodic serological screenings to identify seropositive breeders. Seropositive cows were inseminated with beef-breed semen, thus excluding their descendants from the remount in order to prevent the vertical transmission of the disease. Seronegative animals, as well as heifers at first insemination, were tested before each insemination. Sera of 1097 cattle were examined by a commercial indirect ELISA for the detection of antibodies anti-Neospora caninum. To verify the difference in seropositivity values among years of sampling, statistical analysis through generalized estimation equations (GEEs) was performed, also considering the effects of age, lineages, and occurrence of abortion. A seroprevalence of 33.8% was found in the first screening. The prevalence and incidence of the infection within the herd decreased significantly in 2017 (P = 28.9%, I = 1.4%) (p-value = 0.0001). The family line investigation detected a higher risk of being seropositive for a cow born to a seropositive dam (p-value = 0.0001) than to a seronegative dam, decreasing both the apparently vertical and horizontal transmissions. The number of spontaneous abortions decreased after the first year of the study (23 in 2013 to 6 in 2017). Seropositive animals were associated with abortion events (p-value = 0.0001). Although an eradication of N. caninum was not achieved at the end of the study period, a significant reduction in prevalence and incidence of neosporosis in the herd and a reduction of the abortion rate was achieved with the application of this control plan in five years, without culling a high number of seropositive potential milk-producing animals.

Time-dependent changes in pregnancy-associated glycoproteins and progesterone in commercial crossbred sheep

The ruminant placenta functions as an endocrine and paracrine organ secreting proteins, growth factors, and steroid hormones, including pregnancy-associated glycoproteins (PAG), proteins with elusive function, which are readily detectable in maternal serum after placental attachment. In sheep, circulating progesterone beyond gestational Day 50 is predominantly of placental origin. The relationship among placental secreted factors, including progesterone, remains uncertain in sheep. The first aim of the study was to determine the relationship between gestational PAG profiles-using two commercial ELISA assays-progesterone, and fetal growth during pregnancy. The second aim of the study was to assess the presence and clearance of PAG in neonatal lambs and peripartum ewes in commercial crossbred sheep. Maternal serum samples were collected during mid-pregnancy and assayed for PAG1, pregnancy-specific protein B (PSPB), and progesterone. Maternal serum samples were also collected weekly starting 1-month prepartum until 10 weeks postpartum. Serum samples from newborns were collected at birth until Day 12 after birth and assayed for PAG1. Circulating maternal PAG1 concentrations steadily increased throughout mid-gestation, whereas PSPB exhibited a bimodal pattern of secretion. A strong positive correlation was observed between progesterone and PAG1 (r² = 0.779, P < 0.0001), but not between PSPB and progesterone. No relationship was found between placental factors (PAG1, PSPB, and progesterone) and fetal size. PAG1 concentrations were lower before and after parturition in singleton compared with twin pregnancies (P < 0.05). Maternal PAG1 concentrations began declining at parturition and continued to decline until 10 weeks after parturition (P < 0.05). In newborns, PAG1 concentrations continuously declined in both singleton and twins regardless of sex (P < 0.05) and cleared from newborn serum by 12 days after birth. Our findings reported for the first time how different assays used to determine circulating PAG concentrations display different gestational profiles in sheep and how it allows the differentiation between singleton and multiple pregnancies. In conclusion, the strong correlation between PAG1 and progesterone during gestation reports that PAG1 can be effectively used as a marker of placental function.

Factors affecting plasma prolactin concentrations throughout gestation in high producing dairy cows

The aim of the present study was to investigate possible relationships between plasma concentrations of prolactin and the following factors throughout gestation in lactating dairy cows: photoperiod, season, milk production, Neospora caninum-seropositivity, twin pregnancy, and plasma concentrations of pregnancy associated glycoproteins-1 (PAG-1), progesterone and cortisol. Pregnancy was diagnosed by trans-rectal ultrasonography on Day 40 post-insemination and by palpation per rectum on Days 90, 120, 150, 180 and 210 or until abortion in aborting cows. Blood samples were collected from each animal immediately before each pregnancy diagnosis. The study population was comprised of 73 non-aborting (54 Neospora-seropositive cows) and 20 aborting cows (all Neospora-seropositive) cows. In non-aborting cows, GLM repeated measures of analysis of variance revealed that lactation number and days in milk had no effect on plasma prolactin concentrations throughout gestation, whereas high plasma prolactin concentrations were significantly associated with high plasma levels of cortisol and PAG-1, with Neospora-seropositivity, positive photoperiod (increasing day length), twin pregnancy, and with low plasma progesterone concentrations. An interaction among plasma prolactin, plasma cortisol and milk production was observed in that plasma prolactin concentrations differed significantly throughout gestation and were highest in high-producing cows with high cortisol levels. In Neospora-seropositive non-aborting versus aborting cows, mean prolactin concentrations failed to differ on Days 40, 90, 120, 150 and 180 of pregnancy, whereas prolactin values were significantly lower (P=0.03) in aborting animals on Day 210 of pregnancy. Our results indicate that a positive photoperiod and Neospora-infection lead to increased plasma prolactin concentrations throughout gestation. Reduced prolactin concentrations detected in Neospora-seropositive aborting cows compared to non-aborting animals suggests a protective effect of prolactin in N. caninum infection.

Specific anti-Neospora caninum IgG1 and IgG2 antibody responses during gestation in naturally infected cattle and their relationship with gamma interferon production

Gamma interferon (IFN-gamma) production has been attributed a protective role against abortion in Neospora-infected dairy cows. This study investigate possible relationships between plasma levels of the N. caninum-specific immunoglobulin (Ig) isotypes IgG1 and IgG2 and IFN-gamma production throughout gestation in dairy cows naturally infected with the parasite. Data were obtained from 31 pregnant Neospora-seropositive animals. Blood samples were collected on gestation days 40, 90, 120, 150, 180 and 210 or until abortion. Ten pregnancies ended in abortion. One of the 11 cows producing IFN-gamma suffered abortion (9.1% of the cows producing IFN-gamma). Non-aborting cows producing IFN-gamma (n=10) showed a significantly higher IgG2/IgG1 antibody ratio throughout the gestation period than cows not producing IFN-gamma (n=11). A significant negative effect of IFN-gamma production on IgG1 antibodies was also observed, while IFN-gamma production did not affect IgG2 antibody levels. In contrast, higher levels of IgG2 antibodies compared to IgG1 antibodies were observed over the whole of gestation in aborting animals, both in those not producing IFN-gamma and in the single aborting cow that produced the cytokine. Our findings indicate that a Th1 immune response, in which IgG2 antibodies prevail, could be protective against N. caninum abortion, but only in the presence of IFN-gamma production. On their own, elevated IgG2 antibody titres appear to be insufficient to protect dams chronically infected with N. caninum against abortion.

Plasma concentrations of pregnancy-associated glycoprotein-1 (PAG-1) in high producing dairy cows suffering early fetal loss during the warm season

The present study was designed to establish whether plasma pregnancy-associated glycoprotein-1 (PAG-1) measurements during the early fetal period can be associated with early fetal loss. Blood samples were obtained and ultrasound controls performed on days 35, 42, 49, 56, and 63 of gestation or until pregnancy loss from 98 lactating dairy cows. Radioimmunoassay systems were used to determine PAG-1 and progesterone concentrations. Of the 98 pregnancies investigated 18 (18.4%) suffered early fetal loss: 15 (18.5%) in cows carrying singletons, and 3 (16.7%) in twin pregnancies. In cows suffering pregnancy loss, all living embryos registered on day 35 seemed normal in size and development in all weekly ultrasound controls before fetal expulsion. Using analysis of variance, plasma PAG-1 and progesterone values were not different between no loss and fetal loss groups for every gestation period. Based on the odds ratio, and considering only PAG-1 values obtained on day 35 of gestation, the risk of fetal loss was 10 and 6.8 times more likely in cows with low (<2.5 ng/ml) and high (>4 ng/ml) PAG-1 values, respectively, than in cows with medium PAG-1 values, used as reference. Of the 10 inseminating bulls included in the study, one was related to increased fetal loss by odds ratio of 21.7, whereas one bull was attributed fetal loss rate reduced by odds ratio of 12.5 (1/0.08) These findings can have a clear clinical application: PAG-1 measurements from one single sample taken on day 35 of gestation provided more useful information than a series of values obtained from day 35 to 63 of gestation, and can be indicators of subsequent fetal loss.

Milk production correlates negatively with plasma levels of pregnancy-associated glycoprotein (PAG) during the early fetal period in high producing dairy cows with live fetuses

This study was designed to establish possible factors affecting plasma pregnancy-associated glycoprotein (PAG) concentrations during early pregnancy in high producing dairy cows with live fetuses. Blood samples were obtained on days 35, 42, 49, 56 and 63 of gestation from 80 lactating cows in two herds carrying live fetuses. Radioimmunoassay systems were used to determine PAG (RIA-497 and RIA-706) and progesterone concentrations. We evaluated the effects on PAG concentrations of herd, lactation number, sire of fetus, day of gestation, fetus number, plasma progesterone and milk production at each time point established, along with possible paired interactions. Mean milk production per cow approached 41kg during the study period. PAG concentrations were not affected by herd, lactation number or plasma progesterone concentration. Significant positive effects on PAG concentrations were shown by the gestation day, and the interaction between day of gestation and twin pregnancy. Significant differences between bulls and a significant negative correlation between milk production and PAG values on day 63 of pregnancy were also detected. Proportions of blood samples showing undetectable PAG levels and false negative diagnoses throughout the study period were significantly higher (P<0.001) using the RIA-497 system (2.5% and 5.3%, respectively) compared to RIA-706 (0% and 0.8%, respectively). Our findings suggest that PAG concentrations during the early fetal period are related to the day of gestation, milk production, number of fetuses and sire of fetus in high producing dairy cows. Under our working conditions, the RIA-706 method was better at detecting plasma PAG molecules than the RIA-497 system.

Relationship between rainfall and Neospora caninum-associated abortion in two dairy herds in a dry environment

The possible direct relationship between climate variations and abortion in Neospora caninum-infected cows has not been studied. The objective of this study was to determine whether climate changes could be a risk factor for abortion in N. caninum-infected cows, and was based on yearly serological screening for neosporosis and on the confirmation of N. caninum infection on aborted fetuses in two high-producing dairy herds with a mean 27% seroprevalence of N. caninum antibodies. The final population study was comprised of 357 pregnancies in seropositive animals. Logistic regression analysis indicated no significant effects of herd, N. caninum antibody titre, climate variables during the first and third trimesters of gestation, mean and maximum temperature-humidity index values during the second trimester of gestation, and previous abortion on the abortion rate. Based on the odds ratio, a 1-unit increase in lactation number yielded a 0.85-fold decrease in the abortion rate. The likelihood of abortion was 1.9 times (1/0.54) lower for pregnant cows inseminated with beef bull semen compared with Holstein-Friesian bull semen. The likelihood of abortion decreased significant and progressively by factors of 0.5, 0.41 and 0.3 for the respective classes 40-49, 30-39 and <30 rainfall mm during the second trimester of gestation (using the class >or=60 rainfall mm as reference). As a general conclusion, it seems that increased rainfall in a dry environment can compromise the success of gestation in N. caninum-infected cows. Attempts should therefore be made to reduce environment effects during the second trimester of gestation, a period in which the immune response of cows is diminished.

The use of beef bull semen reduced the risk of abortion in Neospora-seropositive dairy cows

There is an evidence that the epidemiology of neosporosis differs in dairy and beef cattle, such that beef cattle carry a lower risk of abortion. The aim of the present study was to establish whether artificial insemination using semen from beef bulls could reduce the risk of abortion in dairy cows seropositive for the Neospora caninum parasite. Our study was based on yearly serological screening for neosporosis and on the confirmation of Neospora infection in aborted fetuses in two high-producing dairy herds with a mean 28% seroprevalence of N. caninum antibodies. The study population comprised of 273 pregnancies in seropositive animals: 156 pregnancies monitored after insemination using Holstein-Friesian semen and 117 after insemination using beef bull semen. Abortion rates for these animals were 28.2% (77 of 273), 34.6% (54 of 156) and 19.7% (23 of 117). Logistic regression analysis indicated no significant effects of lactation number and previous abortion on the abortion rate. Based on the odds ratio, a 1-unit increase in the Neospora antibody titre yielded a 1.01-fold increase in the abortion rate. The likelihood of abortion was two times higher for cows in one of the two herds and 2.8 times lower (one of 0.36) for pregnant cows inseminated with beef bull semen rather than Holstein-Friesian semen. Our results indicate that the use of beef bull semen can reduce the risk of abortion in dairy cows, and suggest that annual screening for neosporosis, specifically the antibody titre to the protozoan, could be an useful predictor of abortion risk in reproductive health programmes.

Effects of an experimental Trypanosoma congolense infection on the reproductive performance of West African Dwarf goats

Thirty-six West African Dwarf (WAD) goats were used to assess the effects of an experimental Trypanosoma congolense infection on their reproductive system. Estrous cycles were synchronised and when confirmed pregnant (n = 31), the does were randomly allocated into control and trypanosome-infected groups. After infection, the animals were carefully observed till parturition. Trypanosome infection caused an increase of rectal temperature, a significant drop in PCV (infected: 23.3 +/- 0.3%; control: 28.5 +/- 0.4%; P < 0.0001) and abortions in 27.8% of the infected does. Kids born from infected does had a lower birth weight than kids born from control goats (0.9 +/- 0.1 kg versus 1.6 +/- 0.1 kg; P < 0.0001). Eight out of 13 kids (61.5%) that were born alive from infected does died during their first week of life. Plasma pregnancy-associated glycoprotein (PAG) and progesterone concentrations were lower in the infected animals than in the controls. In general, PAG concentration in does which aborted dropped before abortion. Our results revealed that artificial T. congolense infection affected reproductive performance of WAD goats with abortions, premature births and perinatal losses being observed. Neither transplacental transmission of T. congolense nor histopathological lesions of the placenta could be demonstrated.

Aspartic proteinase members secreted by the ruminant placenta: specificity of three radioimmunoassay systems for the measurement of pregnancy-associated glycoproteins

Pregnancy-associated glycoproteins (PAGs) isolated from the placenta of various ruminant species are enzymatically inactive members of the aspartic proteinase family. The measurement of these proteins in the maternal blood can be a good indicator of the presence of a live embryo. As certain aspartic proteinases are present in biological fluids in physiological and pathological conditions at various concentrations, it was necessary to determine the specificity of three radioimmunoassay (RIA) systems currently used for the detection of PAG molecules. Commercially available members of the aspartic proteinase family like pepsinogen, pepsin, chymosin, rennet, cathepsin D and renin were tested in a wide concentration range (10 ng/ml - 1 mg/ml). Pepsinogen cross-reacted in RIA 1, RIA 2 and RIA 3 over 1 mg/ml, 50 microg/ml and 500 microg/ml concentrations, respectively. In the presence of pepsin, cross-reaction was observed in RIA 1, RIA 2 and RIA 3 over 1 mg/ml, 500 microg/ml and 1 mg/ml concentrations, respectively. Chymosin and rennet could cross-react in RIA 2 and RIA 3, while renin and cathepsin D did not decrease the binding of the tracer to antisera more, than that of the minimal detection limit. As the plasma/serum concentrations of the examined aspartic proteinases reported in the literature were outside the concentration range where cross-reaction was observed, it can be concluded that these RIA systems were specific for the detection of PAGs in biological fluids.

Comparison of the ability of three radioimmunoassay to detect pregnancy-associated glycoproteins in bovine plasma

CONTENTS

Pregnancy-associated glycoproteins (PAGs) constitute a large family of glycoproteins that are synthesized in the superficial layer of the ruminant placenta according to a spatial and temporal expression pattern. When PAGs are released in the maternal blood they can be used for pregnancy diagnosis, pregnancy follow-up and for the monitoring of the trophoblastic function. Three different radioimmunoassay systems (RIA 1, RIA 2 and RIA 3) using antisera produced against PAG I67 (RIA 1), PAG55+62 (RIA 2) and PAG55+59 (RIA 3) were used in this investigation in order to measure the PAG concentration in plasma samples withdrawn from pregnant cows and heifers during different periods following artificial insemination (AI). These systems were able to detect PAG molecules in the maternal blood as early as 21 days after AI in different concentrations (RIA 1: 0.43 +/- 0.24 ng/ml, mean +/- SD; RIA 2: 0.48 +/- 0.24 ng/ml; RIA 3: 0.64 +/- 0.37 ng/ml). On days 32 and 42 RIA 2 (4.30 +/- 1.32 ng/ml and 5.56 +/- 1.95 ng/ml) and RIA 3 (4.17 +/- 1.15 ng/ml and 5.60 +/- 1.89 ng/ml) presented significantly (p < 0.0001) higher PAG concentrations than those of RIA 1 (2.43 +/- 0.81 ng/ml and 4.01 +/- 1.48 ng/ml), respectively. After day 21, significant correlations (p < 0.0001; r >/= 0.929) were determined between the three systems. Additionally the three individual PAG profiles presented in this study showed that PAG molecules secreted in the maternal blood between 21 and 50 days after AI were better recognized by the RIA 2 and RIA 3 systems. This study clearly indicated that the ability of a RIA test to recognize PAG molecules in the maternal blood can be improved by carefully selecting the antiserum.