Deciphering decidual leukocyte traffic with serial intravascular staining

The decidual immunome is dynamic, dramatically changing its composition across gestation. Early pregnancy is dominated by decidual NK cells, with a shift towards T cells later in pregnancy. However, the degree, timing, and subset-specific nature of leukocyte traffic between the decidua and systemic circulation during gestation remains poorly understood. Herein, we employed intravascular staining in pregnant C57BL/6J mice and cynomolgus macaques (Macaca fascicularis) to examine leukocyte traffic into the decidual basalis during pregnancy. Timed-mated or virgin mice were tail-vein injected with labelled αCD45 antibodies 24 hours and 5 minutes before sacrifice. Pregnant cynomolgus macaques (GD155) were infused with labelled αCD45 at 2 hours or 5 mins before necropsy. Decidual cells were isolated and resulting suspensions analyzed by flow cytometry. We found that the proportion of intravascular (IVAs)-negative leukocytes (cells labeled by the 24h infusion of αCD45 or unlabeled) decreased across murine gestation while recent immigrants (24h label only) increased in mid- to late-gestation. In the cynomolgus model our data confirmed differential labeling of decidual leukocytes by the infused antibody, with the 5 min infused animal having a higher proportion of IVAs+ cells compared to the 2hr infused animal. Decidual tissue sections from both macaques showed the presence of intravascularly labeled cells, either in proximity to blood vessels (5min infused animal) or deeper into decidual stroma (2hr infused animal). These results demonstrate the value of serial intravascular staining as a sensitive tool for defining decidual leukocyte traffic during pregnancy.

Infection of the maternal-fetal interface and vertical transmission following low-dose inoculation of pregnant rhesus macaques (Macaca mulatta) with an African-lineage Zika virus

BACKGROUND

Congenital Zika virus (ZIKV) infection can result in birth defects, including malformations in the fetal brain and visual system. There are two distinct genetic lineages of ZIKV: African and Asian. Asian-lineage ZIKVs have been associated with adverse pregnancy outcomes in humans; however, recent evidence from experimental models suggests that African-lineage viruses can also be vertically transmitted and cause fetal harm.

METHODOLOGY/PRINCIPAL FINDINGS

To evaluate the pathway of vertical transmission of African-lineage ZIKV, we inoculated nine pregnant rhesus macaques (Macaca mulatta) subcutaneously with 44 plaque-forming units of a ZIKV strain from Senegal, (ZIKV-DAK). Dams were inoculated either at gestational day 30 or 45. Following maternal inoculation, pregnancies were surgically terminated seven or 14 days later and fetal and maternal-fetal interface tissues were collected and evaluated. Infection in the dams was evaluated via plasma viremia and neutralizing antibody titers pre- and post- ZIKV inoculation. All dams became productively infected and developed strong neutralizing antibody responses. ZIKV RNA was detected in maternal-fetal interface tissues (placenta, decidua, and fetal membranes) by RT-qPCR and in situ hybridization. In situ hybridization detected ZIKV predominantly in the decidua and revealed that the fetal membranes may play a role in ZIKV vertical transmission. Infectious ZIKV was detected in the amniotic fluid of three pregnancies and one fetus had ZIKV RNA detected in multiple tissues. No significant pathology was observed in any fetus; and ZIKV did not have a substantial effect on the placenta.

CONCLUSIONS/SIGNIFICANCE

This study demonstrates that a very low dose of African-lineage ZIKV can be vertically transmitted to the macaque fetus during pregnancy. The low inoculating dose used in this study suggests a low minimal infectious dose for rhesus macaques. Vertical transmission with a low dose in macaques further supports the high epidemic potential of African ZIKV strains.

Abstract 034: Leveraging Mouse Liver Co-expression Networks and Human Lipid Gwas Data to Identify Cholesterol Metabolism Genes

Genetic factors play an important role in contributing to variation in plasma lipid levels across the human population. Large genome-wide association studies (GWAS) in humans have identified more than 100 loci significantly associated with plasma levels of low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, total cholesterol (TC), and triglycerides. To prioritize genes that are involved in cholesterol metabolism, we developed a systematic approach to leverage genome-wide liver transcriptomic and proteomic data from multiple mouse reference populations along with human lipid GWAS data. We constructed global co-expression networks from twelve distinct mouse liver datasets, encompassing more than 800 unique mice and identified a conserved module of genes highly enriched for cholesterol biosynthesis. Based on replication across datasets and presence in transcript and protein, we prioritized 112 unique genes. Intersection of these 112 prioritized genes with human GWAS data for LDL, HDL, TC, and triglycerides identified 54 genes to be within 100 kilobases of a significant or suggestive significant single nucleotide polymorphism (SNP). Out of the 54 identified genes that overlap with human GWAS data, 29 have well documented biological roles in cholesterol metabolism, such as LDLR , PCSK9 , and INSIG1 . With the 25 identified genes with no described role in cholesterol metabolism, we tested for transcriptional regulation to cholesterol and performed a functional screen by siRNA knockdown. From this analysis, we identified twelve genes that show transcriptional regulation to cholesterol levels and nine genes that are able to modulate cholesterol metabolism when targeted in vitro with siRNA. Five genes out of the 25 prioritized genes show both transcriptional regulation to cholesterol and ability to modulate cholesterol metabolism in vitro. One of these genes, Sestrin1 , we validate in vivo and in vitro as a modulator of cholesterol metabolism. Collectively, through a systematic approach we have identified 25 highly prioritized genes that have no documented role in cholesterol metabolism, five genes are transcriptionally regulated by cholesterol and influence cholesterol metabolism.