Macrophage Exosomes Induce Placental Inflammatory Cytokines: A Novel Mode of Maternal-Placental Messaging.

During pregnancy, the placenta forms the interface between mother and fetus. Highly controlled regulation of trans-placental trafficking is therefore essential for the healthy development of the growing fetus. Extracellular vesicle-mediated transfer of protein and nucleic acids from the human placenta into the maternal circulation is well documented; the possibility that this trafficking is bi-directional has not yet been explored but could affect placental function and impact on the fetus.We hypothesized that the ability of the placenta to respond to maternal inflammatory signals is mediated by the interaction of maternal immune cell exosomes with placental trophoblast. Utilizing the BeWo cell line and whole placental explants, we demonstrated that the human placenta internalizes macrophage-derived exosomes in a time- and dose-dependent manner. This uptake was via clathrin-dependent endocytosis. Furthermore, macrophage exosomes induced release of proinflammatory cytokines by the placenta. Taken together, our data demonstrates that exosomes are actively transported into the human placenta and that exosomes from activated immune cells modulate placental cytokine production. This represents a novel mechanism by which immune cells can signal to the placental unit, potentially facilitating responses to maternal inflammation and infection, and thereby preventing harm to the fetus.

Antenatal vaccination against Group B streptococcus: attitudes of pregnant women and healthcare professionals in the UK towards participation in clinical trials and routine implementation.

INTRODUCTION: Maternal vaccination is increasingly part of antenatal care in the UK and worldwide. Trials of Group B streptococcus vaccines are ongoing. This study investigated the attitudes of pregnant women and healthcare professionals towards antenatal vaccination, both in routine care and a clinical trial setting. MATERIAL AND METHODS: Survey of 269 pregnant women, 273 midwives/obstetricians and 97 neonatal doctors across seven sites in the UK assessing attitudes towards antenatal vaccinations, knowledge of Group B streptococcus, a hypothetical Group B streptococcus vaccine, and participation in clinical vaccine trials. RESULTS: 68% of pregnant women intended to receive a vaccine during their current pregnancy (183/269) and 43% (of all respondents, 115/269) reported they would be very/fairly likely to accept a vaccine against Group B streptococcus despite only 29% (55/269) knowing what Group B streptococcus was. This increased to 69% after additional information about Group B streptococcus was provided. Twenty-four percent of pregnant women reported they would be likely to take part in a clinical trial of an unlicensed Group B streptococcus vaccine. Fifty-nine percent of maternity professionals and 74% of neonatologists would be likely to recommend participation in a Group B streptococcus vaccine trial to women, with the vast majority (>99%) willing to be involved in such a study. Incentives to take part cited by pregnant women included extra antenatal scans and the opportunity to be tested for Group B streptococcus. CONCLUSION: Pregnant women and healthcare professionals were open to the idea of an antenatal Group B streptococcus vaccine and involvement in clinical trials of such a vaccine. Education and support from midwives would be key to successful implementation.

Modification of innate immune responses to Bordetella pertussis in babies from pertussis vaccinated pregnancies.

BACKGROUND: Tetanus, diphtheria, acellular pertussis, inactivated polio (Tdap-IPV) vaccines administered during pregnancy protect young infants from Bordetella pertussis (B. pertussis) infection. Whilst the impact of maternal Tdap-IPV vaccination on infants' humoral response to subsequent pertussis immunisation has been investigated, little is known about any impact on innate responses. METHODS: We investigated the immune response to B. pertussis in mothers and infants from Tdap-IPV-vaccinated and unvaccinated pregnancies, utilising a whole blood assay and flow cytometric phenotyping of neonatal natural killer (NK) cells, monocytes and dendritic cells. Blood was collected from mother and umbilical cord at birth, and from infants at seven weeks (one week pre-primary pertussis immunisation) and five months of age (one month post-primary pertussis immunisation). 21 mothers and 67 infants were studied. FINDINGS: Vaccinated women had elevated pro-inflammatory cytokine responses to B. pertussis. At birth, babies of vaccinated women had elevated IL-2 and IL-12 responses, elevated classical monocyte proportions, and reduced monocyte and NK cell cytokine responses. The elevated IL-2 response persisted to seven weeks-of-age, when lower IL-10 and IL-13 responses were also seen. One-month post-primary pertussis vaccination, infants from vaccinated pregnancies still had lower IL-10 responses to B. pertussis, as well as lower IL-4. INTERPRETATION: This study suggests that pertussis vaccination during pregnancy impacts infant cellular immune responses, potentially contributing to the modification of antibody responses already reported following primary immunisation against B. pertussis. FUNDING: National Institute for Health Research Imperial Biomedical Research Centre and IMmunising PRegnant women and INfants neTwork (funded by the GCRF Networks in Vaccines R&D).

Evaluation of a midwife-led, hospital based vaccination service for pregnant women.

Background: Vaccines against whooping cough (pertussis) and seasonal-influenza are recommended for pregnant women in England. Uptake however varies regionally and by ethnicity. Pregnant women are traditionally vaccinated in primary care, though some hospitals now offer vaccines through antenatal clinics. This mixed-methods evaluation describes the demographic characteristics of women seen in a hospital midwife-led antenatal vaccine clinic and explores vaccine decision making. Methods: Descriptive statistics of women seen in a London hospital's midwife-led vaccine clinic were generated from electronic routine maternity records, including data on ethnicity, parity, age and deprivation indices. Reasons for vaccine decline given by women to midwives were categorized by themes. Qualitative interviews of women seen in the clinic were also undertaken. Results: Between 1st April 2017 and 31st March 2018 the vaccine clinic saw 1501 pregnant women. Of these, 83% received pertussis vaccine and (during flu season) 51% received influenza vaccine, from the clinic. Fewer Black Afro-Caribbean women seen by the clinic were vaccinated, compared to other ethnicities with only 68% receiving pertussis and 34% flu vaccines respectively (p < .05). Among all women delivering at the hospital over the year, 42%, (1334/3147) were vaccinated by the clinic. Qualitative interviews found that reassurance from healthcare professionals, particularly midwives, was the most important factor influencing maternal vaccine decisions. Conclusions: Midwife-led hospital clinics can offer an effective alternative to primary care provision for vaccines in pregnancy. Consistent with previous work, vaccine uptake varied by ethnicity. Midwives play a key role in the provision of vaccine services and influence women's vaccine decisions.

Update on Transplacental Transfer of IgG Subclasses: Impact of Maternal and Fetal Factors.

Transplacental antibody transfer from mother to fetus provides protection from infection in the first weeks of life, and the four different subclasses of IgG (IgG1, IgG2, IgG3, and IgG4) have diverse roles in protection against infection. In this study, we evaluated concentrations and transplacental transfer ratios of the IgG subclasses in a healthy UK-based cohort of mother-cord pairs, and investigated associations with maternal, obstetric, and fetal factors. In agreement with previous studies, we found a strong association between maternal and cord IgG for all subclasses. We report a transfer efficiency hierarchy of IgG1>IgG3>IgG4=IgG2 in our study population, and our review of the literature demonstrates that there is no consensus in the hierarchy of subclass transfer, despite the commonly made statement that the order is IgG1>IgG4>IgG3>IgG2. We report additional data regarding negative associations between elevated maternal IgG concentrations and maternal/cord transfer ratios, finding an effect on IgG1, IgG2, and IgG3 subclasses. Levels of IgG subclasses were the same between venous and arterial blood samples from the umbilical cord, but there was a significantly higher level of total IgG in arterial blood. We found no correlation between placental FcRn protein levels and IgG transfer in our cohort, suggesting that IgG is the main determinant of observed differences in transplacental transfer ratios at term. Neonatal IgG1 and IgG4 levels were increased with later gestation at delivery, independent of any increase in transplacental transfer, indicating that the benefit of later gestation is through accumulation of these subclasses in the fetus. Neonatal IgG2 levels and transfer ratios were reduced in rhesus-negative pregnancies, suggesting that administered anti-D antibodies may compete for transplacental transfer of this subclass. Maternal influenza vaccination resulted in elevated maternal and neonatal levels of IgG4, whereas maternal Tdap vaccination had no impact on neonatal levels of the subclasses, nor transfer. However, within Tdap vaccinated pregnancies, later gestation at Tdap vaccination was associated with higher transplacental transfer. Our study provides information regarding levels and transfer of IgG subclasses in healthy term pregnancies and demonstrates the importance of recording detailed clinical information in studies of antibody transfer, including parity, ethnicity, and timing of maternal vaccine delivery.

Macrophage- but not monocyte-derived extracellular vesicles induce placental pro-inflammatory responses.

The placenta sheds extracellular vesicles (EVs), including exosomes, into the maternal circulation. We recently demonstrated that this trafficking of EVs is bi-directional; with uptake of macrophage exosomes by the placenta inducing cytokine release. The specificity of this response is currently unknown. THP-1 cells were cultured as monocytes or differentiated to macrophages, and EVs isolated by ultra-centrifugation. The effect of EVs on human placental explants was measured by cytokine ELISA/luminex. Macrophage, but not monocyte, EVs induce the release of pro-inflammatory cytokines by the placenta. Thus, placental responses to immune cell EVs, including exosomes, reflects the phenotype of the source cell.

What determines uptake of pertussis vaccine in pregnancy? A cross sectional survey in an ethnically diverse population of pregnant women in London.

INTRODUCTION: Following the major outbreak of pertussis and 14 infant deaths across England in 2012, the Department of Health (DH) introduced the UK's first maternal pertussis vaccination programme. Data published by Public Health England (PHE) suggest uptake of the vaccine varies considerably across the country. The reasons for this heterogeneity need to be addressed to optimise the impact of the programme. OBJECTIVE: To assess uptake of antenatal pertussis and influenza vaccine in a leading NHS Trust in London and to explore awareness and attitudes of pregnant women towards the pertussis vaccination programme. DESIGN: A cross sectional survey was conducted in an ethnically diverse group of 200 pregnant women accessing antenatal care at Imperial Healthcare NHS Trust. Quantitative data was tabulated and content analysis was carried out on the free text. Qualitative data was divided into themes for accepting or declining the vaccine. RESULTS: Awareness of the programme was 63% (126/200) with actual uptake of the vaccine only 26.0% (52/200). Women had received information from multiple sources, primarily General Practitioners (GP) and midwives. 34.0% (68/200) of women were offered the vaccine at their GP practice, only 24% reported a meaningful discussion with their GP about it. Uptake differed by up to 15.0% between ethnicities. Qualitative data showed that uptake could be significantly enhanced if vaccination was recommended by a familiar healthcare professional. Feeling uninformed, lack of professional encouragement and uncertainties of risk and benefit of the vaccine were the greatest barriers to uptake. CONCLUSION: Vaccine uptake in this cohort of pregnant women was poor. Understanding the target audience and engaging with key groups who influence women's decision-making is essential. Knowledgeable health care professionals need to recommend the vaccine and provide accurate and timely information to increase success of this important programme.