Peta L. Grigsby

Congenital and opportunistic infections: Ureaplasma species and Mycoplasma hominis

There is strong evidence from clinical and experimental animal studies that ureaplasmas can invade the amnionic sac and induce an inflammatory response resulting in chorioamnionitis, preterm labor and neonatal lung injury. The ability of Ureaplasma spp. and Mycoplasma hominis to cause pneumonia, bacteremia, and meningitis in newborns can no longer be questioned. The association of Ureaplasma spp. with bronchopulmonary dysplasia has been supported by the majority of observational studies, but proof of causality is still lacking. The availability of molecular diagnostic technologies has enabled the designation of the two Ureaplasma biovars as individual species, but additional work must be done to establish whether there is differential pathogenicity between the Ureaplasma spp. or among their respective serovars. Future investigations to prevent prematurity should be directed toward identification and localization of specific micro-organisms combined with targeted antibiotic trials to determine whether such interventions can improve long-term infant outcomes.

Zika Virus infection of rhesus macaques leads to viral persistence in multiple tissues

Zika virus (ZIKV), an emerging flavivirus, has recently spread explosively through the Western hemisphere. In addition to symptoms including fever, rash, arthralgia, and conjunctivitis, ZIKV infection of pregnant women can cause microcephaly and other developmental abnormalities in the fetus. We report herein the results of ZIKV infection of adult rhesus macaques. Following subcutaneous infection, animals developed transient plasma viremia and viruria from 1–7 days post infection (dpi) that was accompanied by the development of a rash, fever and conjunctivitis. Animals produced a robust adaptive immune response to ZIKV, although systemic cytokine response was minimal. At 7 dpi, virus was detected in peripheral nervous tissue, multiple lymphoid tissues, joints, and the uterus of the necropsied animals. Notably, viral RNA persisted in neuronal, lymphoid and joint/muscle tissues and the male and female reproductive tissues through 28 to 35 dpi. The tropism and persistence of ZIKV in the peripheral nerves and reproductive tract may provide a mechanism of subsequent neuropathogenesis and sexual transmission.

Maternal azithromycin therapy for Ureaplasma intraamniotic infection delays preterm delivery and reduces fetal lung injury in a primate model

OBJECTIVE We assessed the efficacy of a maternal multidose azithromycin (AZI) regimen, with and without antiinflammatory agents to delay preterm birth and to mitigate fetal lung injury associated with Ureaplasma parvum intraamniotic infection. STUDY DESIGN Long-term catheterized rhesus monkeys (n = 16) received intraamniotic inoculation of U parvum (10(7) colony-forming U/mL, serovar 1). After contraction onset, rhesus monkeys received no treatment (n = 6); AZI (12.5 mg/kg, every 12 h, intravenous for 10 days; n = 5); or AZI plus dexamethasone and indomethacin (n = 5). Outcomes included amniotic fluid proinflammatory mediators, U parvum cultures and polymerase chain reaction, AZI pharmacokinetics, and the extent of fetal lung inflammation. RESULTS Maternal AZI therapy eradicated U parvum intraamniotic infection from the amniotic fluid within 4 days. Placenta and fetal tissues were 90% culture negative at delivery. AZI therapy significantly delayed preterm delivery and prevented advanced fetal lung injury, although residual acute chorioamnionitis persisted. CONCLUSION Specific maternal antibiotic therapy can eradicate U parvum from the amniotic fluid and key fetal organs, with subsequent prolongation of pregnancy, which provides a therapeutic window of opportunity to effectively reduce the severity of fetal lung injury.

Choriodecidual inflammation: a harbinger of the preterm labor syndrome.

Causal, cellular, and inflammatory links between choriodecidual infection with group B streptococcus (GBS) and preterm labor were assessed in a nonhuman primate model. Rhesus monkeys received varying doses of a clinical isolate of GBS, type III or saline, via an indwelling catheter placed between the chorion/decidua and myometrium in the lower pole of the uterus. Choriodecidual inoculation of GBS was followed by a graded response in amniotic fluid (AF) leukocytes, proinflammatory cytokines, prostaglandin E2 and F2α, and uterine activity (P < .05). The magnitude of the inflammatory response in AF was related, in part, to the initial inoculum size and whether AF cultures remained negative or became positive for GBS. Microbial invasion of AF was associated with advanced inflammation and preterm labor. We provide experimental evidence that choriodeciduitis is a transitional stage of intrauterine infection, which may be self-limited, remain dormant, or progress to intraamniotic infection. These data, coupled with clinical observations, suggest that choriodecidual inflammation is an antecedent event in the pathogenesis of premature cervical ripening (functional cervical insufficiency), premature rupture of the fetal membranes, or preterm labor.

Restriction of placental vasculature in a non-human primate: A unique model to study placental plasticity

The limits of placental plasticity, i.e., the ability of the placenta to adapt and alter its growth trajectory in response to altered fetal requirements, are not known. We report fetal and placental hemodynamic adaptations in a novel non-human primate model in which the fetal inter-placental bridging vessels were surgically ligated. Doppler ultrasound studies showed that the rhesus placenta compensates for an approximate 40% reduction in functional capacity by increased growth and maintenance of umbilical volume blood flow. This unique experimental animal model has applications for mechanistic studies of placental plasticity and the impact on fetal development.

Using dynamic contrast-enhanced MRI to quantitatively characterize maternal vascular organization in the primate placenta

The maternal microvasculature of the primate placenta is organized into 10–20 perfusion domains that are functionally optimized to facilitate nutrient exchange to support fetal growth. This study describes a dynamic contrast‐enhanced magnetic resonance imaging method for identifying vascular domains and quantifying maternal blood flow in them.

Transplacental Transfer of Azithromycin and Its Use for Eradicating Intra-amniotic Ureaplasma Infection in a Primate Model

BACKGROUND Our goals were to describe azithromycin (AZI) pharmacokinetics in maternal plasma (MP), fetal plasma (FP), and amniotic fluid (AF) following intra-amniotic infection (IAI) with Ureaplasma in pregnant rhesus monkeys and to explore concentration-response relationships. METHODS Following intra-amniotic inoculation of Ureaplasma parvum, rhesus monkeys received AZI (12.5 mg/kg every 12 hours intravenously for 10 days; n = 10). Intensive pharmacokinetic sampling of MP, FP, and AF was scheduled following the first (ie, single) dose and the last (ie, multiple) dose. Noncompartmental and pharmacokinetic modeling methods were used. RESULTS The AF area under the concentration-time curve at 12 hours was 0.22 µg×h/mL following a single dose and 6.3 µg×h/mL at day 10. MP and AF accumulation indices were 8.4 and 19, respectively. AZI AF half-life following the single dose and multiple dose were 156 and 129 hours, respectively. The median MP:FP ratio in concomitantly drawn samples was 3.2 (range, 1.3-9.6; n = 9). Eradication of U. parvum occurred at 6.6 days, with a 95% effective concentration (EC95) of 39 ng/mL for the maximum AZI AF concentration. CONCLUSIONS Our study demonstrates that a maternal multiple-dose AZI regimen is effective in eradicating U. parvum IAI by virtue of intra-amniotic accumulation and suggests that antenatal therapy has the potential to mitigate complications associated with U. parvum infection in pregnancy, such as preterm labor and fetal sequelae.

Zika virus infection in pregnant rhesus macaques causes placental dysfunction and immunopathology

Zika virus (ZIKV) infection during pregnancy leads to an increased risk of fetal growth restriction and fetal central nervous system malformations, which are outcomes broadly referred to as the Congenital Zika Syndrome (CZS). Here we infect pregnant rhesus macaques and investigate the impact of persistent ZIKV infection on uteroplacental pathology, blood flow, and fetal growth and development. Despite seemingly normal fetal growth and persistent fetal-placenta-maternal infection, advanced non-invasive in vivo imaging studies reveal dramatic effects on placental oxygen reserve accompanied by significantly decreased oxygen permeability of the placental villi. The observation of abnormal oxygen transport within the placenta appears to be a consequence of uterine vasculitis and placental villous damage in ZIKV cases. In addition, we demonstrate a robust maternal-placental-fetal inflammatory response following ZIKV infection. This animal model reveals a potential relationship between ZIKV infection and uteroplacental pathology that appears to affect oxygen delivery to the fetus during development.Zika virus infection during pregnancy can result in birth defects, but underlying pathogenesis at the maternal-fetal interface is unclear. Here, the authors use non-invasive in vivo imaging of Zika-infected rhesus macaques and show that infection results in abnormal oxygen transport across the placenta.

Folding, but not surface area expansion is associated with cellular morphological maturation in the fetal cerebral cortex.

Altered macroscopic anatomical characteristics of the cerebral cortex have been identified in individuals affected by various neurodevelopmental disorders. However, the cellular developmental mechanisms that give rise to these abnormalities are not understood. Previously, advances in image reconstruction of diffusion magnetic resonance imaging (MRI) have made possible high-resolution in utero measurements of water diffusion anisotropy in the fetal brain. Here, diffusion anisotropy within the developing fetal cerebral cortex is longitudinally characterized in the rhesus macaque, focusing on gestation day (G85) through G135 of the 165 d term. Additionally, for subsets of animals characterized at G90 and G135, immunohistochemical staining was performed, and 3D structure tensor analyses were used to identify the cellular processes that most closely parallel changes in water diffusion anisotropy with cerebral cortical maturation. Strong correlations were found between maturation of dendritic arbors on the cellular level and the loss of diffusion anisotropy with cortical development. In turn, diffusion anisotropy changes were strongly associated both regionally and temporally with cortical folding. Notably, the regional and temporal dependence of diffusion anisotropy and folding were distinct from the patterns observed for cerebral cortical surface area expansion. These findings strengthen the link proposed in previous studies between cellular-level changes in dendrite morphology and noninvasive diffusion MRI measurements of the developing cerebral cortex and support the possibility that, in gyroencephalic species, structural differentiation within the cortex is coupled to the formation of gyri and sulci. SIGNIFICANCE STATEMENT Abnormal brain morphology has been found in populations with neurodevelopmental disorders. However, the mechanisms linking cellular level and macroscopic maturation are poorly understood, even in normal brains. This study contributes new understanding to this subject using serial in utero MRI measurements of rhesus macaque fetuses, from which macroscopic and cellular information can be derived. We found that morphological differentiation of dendrites was strongly associated both regionally and temporally with folding of the cerebral cortex. Interestingly, parallel associations were not observed with cortical surface area expansion. These findings support the possibility that perturbed morphological differentiation of cells within the cortex may underlie abnormal macroscopic characteristics of individuals affected by neurodevelopmental disorders.

IFPA meeting 2016 workshop report II: Placental imaging, placenta and development of other organs, sexual dimorphism in placental function and trophoblast cell lines

Workshops are an important part of the IFPA annual meeting as they allow for discussion of specialized topics. At IFPA meeting 2016 there were twelve themed workshops, four of which are summarized in this report. These workshops addressed challenges, strengths and limitations of techniques and model systems for studying the placenta, as well as future directions for the following areas of placental research: 1) placental imaging; 2) sexual dimorphism; 3) placenta and development of other organs; 4) trophoblast cell lines.