Shuni Virus Replicates at the Maternal-Fetal Interface of the Ovine and Human Placenta

Shuni virus (SHUV) is a neglected teratogenic and neurotropic orthobunyavirus that was discovered in the 1960s in Nigeria and was subsequently detected in South Africa, Zimbabwe, and Israel. The virus was isolated from field-collected biting midges and mosquitoes and shown to disseminate efficiently in laboratory-reared biting midges, suggesting that members of the families Culicidae and Ceratopogonidae may function as vectors. SHUV infections have been associated with severe neurological disease in horses, a variety of wildlife species, and domesticated ruminants. SHUV infection of ruminants is additionally associated with abortion, stillbirth, and congenital malformations. The detection of antibodies in human sera also suggests that the virus may have zoonotic potential. To understand how SHUV crosses the ruminant placenta, we here infected pregnant ewes and subsequently performed detailed clinical- and histopathological examination of placental tissue. We found that SHUV targets both maternal epithelial cells and fetal trophoblasts, that together form the maternal-fetal interface of the ovine placenta. Experiments with human placental explants, furthermore, revealed replication of SHUV in syncytiotrophoblasts, which are generally highly resistant to virus infections. Our findings provide novel insights into vertical transmission of SHUV in sheep and call for research on the potential risk of SHUV infection during human pregnancies.

Neonatal lamb mortality: major risk factors and the potential ameliorative role of melatonin

High incidences of pre-weaning mortality continue to limit global sheep production, constituting a major economic and welfare concern. Despite significant advances in genetics, nutrition, and management, the proportion of lamb deaths has remained stable at 15–20% over the past four decades. There is mounting evidence that melatonin can improve outcomes in compromised ovine pregnancies via enhanced uterine bloodflow and neonatal neuroprotection. This review provides an overview of the major risk factors and underlying mechanisms involved in perinatal lamb mortality and discusses the potential of melatonin treatment as a remedial strategy. Supplementing pregnant ewes with melatonin enhances uterine bloodflow and fetal oxygenation, and potentially birthweight and neonatal thermogenic capacity. Melatonin freely crosses the ovine placenta and blood-brain barrier and provides neuroprotection to the fetal lamb during periods of chronic and acute hypoxia throughout gestation, with improved behavioural outcomes in hypoxic neonates. The current literature provides strong evidence that maternal melatonin treatment improves outcomes for lambs which experience compromised in utero development or prolonged parturition, though to date this has not been investigated in livestock production systems. As such there is a clear basis for continued research into the effects of maternal melatonin supplementation during gestation on pre-weaning survival under extensive production conditions.

Macrophages and T Lymphocytes in the Ovine Placenta After Experimental Infection With Toxoplasma gondii

Early abortion in ovine toxoplasmosis has had limited investigation. This study evaluated the immune response in the placenta of sheep orally infected with Toxoplasma gondii and euthanized between 2 and 4 weeks postinfection. Toxoplasma infection of the placenta was only found at 4 weeks after infection. Parasitic debris in foci of necrosis were immunolabeled in the maternal caruncle, whereas well-preserved intracellular parasitic vacuole-like structures were found in trophoblasts of fetal cotyledon. Early abortions had increased macrophages in caruncular septa, whereas in later abortions the placentas containing the parasite had an increase of T lymphocytes and macrophages mainly in the fetal cotyledons. This study suggests that the immune response in both the fetal and maternal compartments of the placenta may contribute to the pathogenesis of ovine toxoplasmosis and that these responses differ between early and late presentations of the disease.

PSII-35 Melatonin supplementation and restricted nutrition do not affect chorionic somatomammotropin (CSH) concentration in ovine placenta from mid- to late- gestation

Melatonin plays a role as a vasodilator. Vasoactive and angiogenic factors are expressed by placental binucleate cells (BNC) and produce chorionic somatomammotropin (CSH), known to impact fetal and placental growth. We hypothesized that melatonin supplementation and restricted nutrition from mid- to late-gestation would alter CSH concentration and some characteristics of BNC in placenta. At day 50 of gestation, ewes carrying singletons were randomly assigned to a 2 × 2 factorial design and were fed either an adequate (ADQ; 100% NRC; n = 15) or restricted (RES; 60% NRC; n = 15) diet supplemented with 0 (CON, n = 14) or 5 mg of melatonin (MEL; n = 16). Placentomes were collected on day 130 of gestation and preserved in formalin for histological analysis. Cotyledon (COT) were snap frozen for western immunoblotting analyses. Tissue sections were stained using biotinylated Dolichos Biflurus (DBA; a marker of fetal membrane) lectin and fluorescein labeled Texas red-avidin and fluorescein labeled Griffonia Simplifolica (BS) lectin (a marker of BNC). The number, area, and diameter of BNC in COT were determined by image analysis. For immunoblotting, protein was extracted from COT in SDS phosphate buffer, loaded equally, and separated on 12.5% polyacrylamide gels. Protein was transferred to PVDF membranes and incubated with rabbit anti-CSH. Bands were visualized and imaged. Data were analyzed using Proc Mixed procedure of SAS. Melatonin supplementation and restricted nutrition did not affect BNC number, area, or diameter, or CSH protein expression. While we reject our hypothesis that melatonin supplementation and nutrient restriction would alter the CSH concentration and BNC characteristics in COT, we continue to evaluate if the BNC produce angiogenic or vasoactive factors that may influence placental and mammary gland functions in sheep.

PSI-19 Poor maternal nutrition during gestation alters placental IGF-I, IGF-II, and IGFBP-3 mRNA expression in sheep

Insulin-like growth factors (IGF) modulate placental and fetal growth and development through nutrient sensing and endocrine signaling. We hypothesized that poor maternal nutrition during gestation would alter IGF-I, IGF binding protein (IGFBP)-2, and IGFBP-3 mRNA expression in the ovine placenta, but would not affect IGF-II mRNA expression. Pregnant ewes (n = 57) were individually fed: 60% (RES), 100% (CON), or 140% (OVER) of National Research Council requirements for TDN starting at day 30±0.2 of gestation. Ewes were euthanized and cotyledon and caruncle samples were collected at days 45, 90, and 135 of gestation. Relative mRNA expression of IGF-I, IGF-II, IGFBP-2, and IGFBP-3 was quantified using real-time PCR. Data were analyzed using the MIXED procedure in SAS. Relative IGF-I mRNA expression increased during gestation in the caruncle (d45: 0.96±0.06; d90: 1.28±0.06; d135: 1.38±0.05; P < 0.001). In the caruncle, IGFBP-2 expression was greater at d90 and d135 than d45 (d45: 0.67±0.20; d90: 1.90±0.20; d135: 1.65±0.18; P < 0.001). There was no observed effect of diet or day of gestation on IGF-II or IGFBP-3 expression in the caruncle. In the cotyledon, IGF-I expression tended to be greater in RES than OVER, which was similar to CON (CON: 0.96±0.07; RES: 1.10±0.06; OVER: 0.89±0.07; P = 0.08). Relative IGF-II mRNA expression was greater in RES cotyledons than OVER (CON: 1.30±0.35; RES: 1.96±0.31; OVER: 0.54±0.32; P = 0.01). During gestation, IGFBP-2 expression decreased in the cotyledon (d45: 1.26±0.12; d90: 0.93±0.12; d135: 0.59±0.11; P < 0.001). Relative IGFBP-3 mRNA expression was less in RES cotyledons than in OVER or CON (CON: 1.84±0.64; RES: 0.03±0.57; OVER: 3.62±0.66;P < 0.001). The changes in IGF expression in the cotyledon to a greater extent than in the caruncle in response to poor maternal diet suggest a potential mechanism by which maternal-fetal exchange may be modified to restrict placental and fetal growth.