Influenza, immune system, and pregnancy

Immune Response to Respiratory Viral Infections

The respiratory system is constantly exposed to viral infections that are responsible for mild to severe diseases. In this narrative review, we focalized the attention on respiratory syncytial virus (RSV), influenza virus, and severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infections, responsible for high morbidity and mortality in the last decades. We reviewed the human innate and adaptive immune responses in the airways following infection, focusing on a particular population: newborns and pregnant women. The recent Coronavirus disease-2019 (COVID-19) pandemic has highlighted how our interest in viral pathologies must not decrease. Furthermore, we must increase our knowledge of infection mechanisms to improve our future defense strategies.

Implication of viruses in the etiology of preeclampsia

Preeclampsia is one of the most common disorders that poses threat to both mothers and neonates and a major contributor to perinatal morbidity and mortality worldwide. Viral infection during pregnancy is not typically considered to cause preeclampsia; however, syndromic nature of preeclampsia etiology and the immunomodulatory effects of viral infections suggest that microbes could trigger a subset of preeclampsia. Notably, SARS-CoV-2 infection is associated with an increased risk of preeclampsia. Herein, we review the potential role of viral infections in this great obstetrical syndrome. According to in vitro and in vivo experimental studies, viral infections can cause preeclampsia by introducing poor placentation, syncytiotrophoblast stress, and/or maternal systemic inflammation, which are all known to play a critical role in the development of preeclampsia. Moreover, clinical and experimental investigations have suggested a link between several viruses and the onset of preeclampsia via multiple pathways. However, the results of experimental and clinical research are not always consistent. Therefore, future studies should investigate the causal link between viral infections and preeclampsia to elucidate the mechanism behind this relationship and the etiology of preeclampsia itself.

Maternal Influenza and Offspring Neurodevelopment

This review examines the complex interactions between maternal influenza infection, the immune system, and the neurodevelopment of the offspring. It highlights the importance of high-quality studies to clarify the association between maternal exposure to the virus and neuropsychiatric disorders in the offspring. Additionally, it emphasizes that the development of accurate animal models is vital for studying the impact of infectious diseases during pregnancy and identifying potential therapeutic targets. By drawing attention to the complex nature of these interactions, this review underscores the need for ongoing research to improve the understanding and outcomes for pregnant women and their offspring.

Maternal SARS-CoV-2 Infection at Delivery Increases IL-6 Concentration in Umbilical Cord Blood

BACKGROUND

SARS-CoV-2 infection in pregnant women may induce inflammation within the amniotic cavity and/or an increase in proinflammatory cytokines in fetal circulation. The aim was to investigate levels of IL-6 in maternal blood, umbilical cord blood, and amniotic fluid in pregnant women infected with SARS-CoV-2 at delivery.

METHODS

A single-center prospective observational case-control study of pregnant women diagnosed with SARS-CoV-2 infection at delivery was conducted. A total of 48 infected and 42 healthy women had IL-6 concentrations measured in their blood, amniotic fluid, and umbilical cord blood.

RESULTS

The concentrations of IL-6 in maternal blood and amniotic fluid were similar in the study and control groups, while umbilical cord blood concentrations were significantly higher in SARS-CoV-2-positive women. The umbilical cord blood IL-6 concentration was related to composite neonatal morbidity.

CONCLUSIONS

Maternal SARS-CoV-2 infection in pregnant women at delivery increases umbilical cord blood IL-6 concentration. The correlation between maternal and umbilical blood concentrations indicates a possibility of passage of IL-6 through the placenta. Perinatal alterations resulting from maternal SARS-CoV-2 infection at delivery carry a risk of impacting the health of infants even in asymptomatic course of infection.

Severe Acute Respiratory Distress Syndrome Secondary to Concomitant Influenza A and Rhinovirus Infection Complicated by Methicillin-resistant Staphylococcus aureus Pneumonia in an Early Pregnancy Patient With Vaping-induced Lung Injury

Acute respiratory distress syndrome (ARDS) is a life-threatening lung injury characterized by rapid onset of widespread inflammation in the lungs. Multiple risk factors, including pneumonia, non-pulmonary sepsis, aspiration of gastric contents or inhalation injury, have been reported, to cause ARDS. We present a case of a healthy young woman in her first trimester with vaping-induced lung injury who presented with spontaneous pneumothorax and acute respiratory distress syndrome with concomitant influenza A and rhinovirus infection followed by methicillin-resistant Staphylococcus aureus pneumonia.

Longitudinal antibody response kinetics following SARS-CoV-2 messenger RNA vaccination in pregnant and nonpregnant persons

BACKGROUND

For some vaccine-preventable diseases, the immunologic response to vaccination is altered by a pregnant state. The effect of pregnancy on SARS-CoV-2 vaccine response remains unclear.

OBJECTIVE

We sought to characterize the peak and longitudinal anti-S immunoglobulin G, immunoglobulin M, and immunoglobulin A responses to messenger RNA-based SARS-CoV-2 vaccination in pregnant persons and compare them with those in nonpregnant, reproductive-aged persons.

STUDY DESIGN

We conducted 2 parallel prospective cohort studies among pregnant and nonpregnant persons who received SARS-CoV-2 messenger RNA vaccinations. Blood was collected at the time of first and second vaccine doses, 2 weeks post second dosage, and with serial longitudinal follow-up up to 41.7 weeks post vaccination initiation. Anti-S immunoglobulin M, immunoglobulin G, and immunoglobulin A were analyzed by enzyme-linked immunosorbent assay. We excluded those with previous evidence of SARS-CoV-2 infection by history or presence of antinucleocapsid antibodies. In addition, for this study, we did not include individuals who received a third or booster vaccine dosage during the study period. We also excluded pregnant persons who were not fully vaccinated (14 days post receipt of the second vaccine dosage) by time of delivery and nonpregnant persons who became pregnant through the course of the study. We studied the effect of gestational age at vaccination on the anti-S response using Spearman correlation. We compared the peak anti-S antibody responses between pregnant and nonpregnant persons using a Mann-Whitney U test. We visualized and studied the longitudinal anti-S antibody response using locally weighted scatterplot smoothing, Mann-Whitney U test, and mixed analysis of variance test.

RESULTS

Data from 53 pregnant and 21 nonpregnant persons were included in this analysis. The median (interquartile range) age of the pregnant and nonpregnant participants was 35.0 (33.3-37.8) years and 36.0 (33.0-41.0) years, respectively. Six (11.3%) participants initiated vaccination in the first trimester, 23 (43.3%) in the second trimester, and 24 (45.3%) in the third trimester, with a median gestational age at delivery of 39.6 (39.0-40.0) weeks. The median (interquartile range) follow-up time from vaccine initiation to the last blood sample collected was 25.9 (11.9) weeks and 28.9 (12.9) weeks in the pregnant and nonpregnant cohort, respectively. Among pregnant persons, anti-S immunoglobulin G, immunoglobulin A, and immunoglobulin M responses were not associated with gestational age at vaccine initiation (all P>.05). The anti-S immunoglobulin G response at 2 weeks post second dosage was not statistically different between pregnant and nonpregnant persons (P>.05). However, the anti-S immunoglobulin M and immunoglobulin A responses at 2 weeks post second dosage were significantly higher in nonpregnant persons (P<.001 for both). The anti-S immunoglobulin G and immunoglobulin M levels 6 to 8 months after vaccine initiation fell to comparable proportions of the peak 2 weeks post second dosage antibody levels between pregnant and nonpregnant persons (immunoglobulin G P=.77; immunoglobulin M P=.51). In contrast, immunoglobulin A levels 6 to 8 months after vaccine initiation fell to statistically significantly higher proportions of peak 2 weeks post second dosage antibody levels in pregnant compared with nonpregnant persons (P=.002). Maternal anti-S immunoglobulin G levels were strongly correlated with umbilical cord anti-S immunoglobulin G levels (R=0.8, P<.001).

CONCLUSION

The anti-S immunoglobulin A, immunoglobulin M, and immunoglobulin G response to SARS-CoV-2 vaccination in pregnancy is independent of gestational age of vaccine initiation. Maintenance of the immunoglobulin G response is comparable between pregnant and nonpregnant persons. The differential peak response of immunoglobulin M and immunoglobulin A and the differential decline of anti-S immunoglobulin A between pregnant and nonpregnant persons requires further investigation.

Influenza Virus Infection during Pregnancy as a Trigger of Acute and Chronic Complications

Influenza A virus (IAV) infection during pregnancy disrupts maternal and fetal health through biological mechanisms, which are to date poorly characterised. During pregnancy, the viral clearance mechanisms from the lung are sub-optimal and involve hyperactive innate and adaptive immune responses that generate wide-spread inflammation. Pregnancy-related adaptations of the immune and the cardiovascular systems appear to result in delayed recovery post-viral infection, which in turn promotes a prolonged inflammatory phenotype, increasing disease severity, and causing maternal and fetal health problems. This has immediate and long-term consequences for the mother and fetus, with complications including acute cardiopulmonary distress syndrome in the mother that lead to perinatal complications such as intrauterine growth restriction (IUGR), and birth defects; cleft lip, cleft palate, neural tube defects and congenital heart defects. In addition, an increased risk of long-term neurological disorders including schizophrenia in the offspring is reported. In this review we discuss the pathophysiology of IAV infection during pregnancy and its striking similarity to other well-established complications of pregnancy such as preeclampsia. We discuss general features of vascular disease with a focus on vascular inflammation and define the "Vascular Storm" that is triggered by influenza infection during pregnancy, as a pivotal disease mechanism for short and long term cardiovascular complications.

COVID-19 in pregnancy: implications for fetal brain development

The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during pregnancy on the developing fetal brain is poorly understood. Other antenatal infections such as influenza have been associated with adverse neurodevelopmental outcomes in offspring. Although vertical transmission has been rarely observed in SARS-CoV-2 to date, given the potential for profound maternal immune activation (MIA), impact on the developing fetal brain is likely. Here we review evidence that SARS-CoV-2 and other viral infections during pregnancy can result in maternal, placental, and fetal immune activation, and ultimately in offspring neurodevelopmental morbidity. Finally, we highlight the need for cellular models of fetal brain development to better understand potential short- and long-term impacts of maternal SARS-CoV-2 infection on the next generation.

Pregnant Women Develop a Specific Immunological Long-Lived Memory Against SARS-COV-2

It is well established that pregnancy induces deep changes in the immune system. This is part of the physiological adaptation of the female organism to the pregnancy and the immunological tolerance toward the fetus. Indeed, over the three trimesters, the suppressive T regulatory lymphocytes are progressively more represented, while the expression of co-stimulatory molecules decreases overtime. Such adaptations relate to an increased risk of infections and progression to severe disease in pregnant women, potentially resulting in an altered generation of long-lived specific immunological memory of infection contracted during pregnancy. How potent is the immune response against SARS-CoV-2 in infected pregnant women and how long the specific SARS-CoV-2 immunity might last need to be urgently addressed, especially considering the current vaccinal campaign. To address these questions, we analyzed the long-term immunological response upon SARS-CoV-2 infection in pregnant women from delivery to a six-months follow-up. In particular, we investigated the specific antibody production, T cell memory subsets, and inflammation profile. Results show that 80% developed an anti-SARS-CoV-2-specific IgG response, comparable with the general population. While IgG were present only in 50% of the asymptomatic subjects, the antibody production was elicited by infection in all the mild-to-critical patients. The specific T-cell memory subsets rebalanced over-time, and the pro-inflammatory profile triggered by specific SARS-CoV-2 stimulation faded away. These results shed light on SARS-CoV-2-specific immunity in pregnant women; understanding the immunological dynamics of the immune system in response to SARS-CoV-2 is essential for defining proper obstetric management of pregnant women and fine tune gender-specific vaccinal plans.

Distinct trans-placental effects of maternal immune activation by TLR3 and TLR7 agonists: implications for schizophrenia risk

Exposure to infection in utero predisposes towards psychiatric diseases such as autism, depression and schizophrenia in later life. The mechanisms involved are typically studied by administering mimetics of double-stranded (ds) virus or bacterial infection to pregnant rats or mice. The effect of single-stranded (ss) virus mimetics has been largely ignored, despite evidence linking prenatal ss virus exposure with psychiatric disease. Understanding the effects of gestational ss virus exposure has become even more important with recent events. In this study, in pregnant mice, we compare directly the effects, on the maternal blood, placenta and the embryonic brain, of maternal administration of ds-virus mimetic poly I:C (to activate Toll-like receptor 3, TLR3) and ss-virus mimetic resiquimod (to activate TLR7/8). We find that, 4 h after the administration, both poly I:C and resiquimod elevated the levels of IL-6, TNFα, and chemokines including CCL2 and CCL5, in maternal plasma. Both agents also increased placental mRNA levels of IL-6 and IL-10, but only resiquimod increased placental TNFα mRNA. In foetal brain, poly I:C produced no detectable immune-response-related increases, whereas pronounced increases in cytokine (e.g. Il-6, Tnfα) and chemokine (e.g. Ccl2, Ccl5) expression were observed with maternal resiquimod administration. The data show substantial differences between the effect of maternal exposure to a TLR7/8 activator as compared to a TLR3 activator. There are significant implications for future modelling of diseases where maternal ss virus exposure contributes to environmental disease risk in offspring.

Pregnancy and pandemics: Interaction of viral surface proteins and placenta cells

Throughout history, pandemics of infectious diseases caused by emerging viruses have spread worldwide. Evidence from previous outbreaks demonstrated that pregnant women are at high risk of contracting the diseases and suffering from adverse outcomes. However, while some viruses can cause major health complications for the mother and her fetus, others do not appear to affect pregnancy. Viral surface proteins bind to specific receptors on the cellular membrane of host cells and begin therewith the infection process. During pregnancy, the molecular features of these proteins may determine specific target cells in the placenta, which may explain the different outcomes. In this review, we display information on Variola, Influenza, Zika and Corona viruses focused on their surface proteins, effects on pregnancy, and possible target placental cells. This will contribute to understanding viral entry during pregnancy, as well as to develop strategies to decrease the incidence of obstetrical problems in current and future infections.

[Vaccination during pregnancy]

Hintergrund

Schwangere, Feten und Säuglinge weisen aufgrund von Besonderheiten ihres Immunsystems eine erhöhte infektionsbedingte Morbidität und Mortalität auf, die durch den Einsatz von Impfungen während der Schwangerschaft reduziert werden kann.

Ziel

In diesem Beitrag werden die Wirkungsweise, die Evidenz der zu erwartenden Effekte, Kontraindikationen und mögliche Nebenwirkungen von Impfungen in der Schwangerschaft erläutert.

Methode

Es wurde eine selektive Literaturrecherche unter besonderer Berücksichtigung der Empfehlungen der Ständigen Impfkommission am Robert Koch-Institut (STIKO) und einschlägiger Leitlinien durchgeführt.

Ergebnisse

Impfungen in der Schwangerschaft schützen die werdende Mutter vor schweren Verläufen einzelner Infektionskrankheiten und damit verbundenen Schwangerschaftskomplikationen. Zudem vermitteln sie dem Neugeborenen durch die vertikale Übertragung mütterlicher Antikörper einen passiven Immunschutz vor lebensbedrohlichen Infektionen. Für die Impfung mit inaktivierten Impfstoffen gegen Tetanus, Influenza und Pertussis sind Wirksamkeit und Sicherheit gut belegt. Impfungen mit Lebendvakzinen sind wegen ihres theoretischen Risikos für den Fetus kontraindiziert. Die Datenlage zur Anwendung der Impfstoffe gegen die „coronavirus disease 2019“ (COVID 19) ist noch limitiert.

Diskussion

Impfungen in der Schwangerschaft zielen auf den direkten Schutz der Schwangeren durch aktive Immunisierung und/oder des Kindes durch natürliche passive Immunisierung. Schwangere sollten von einer indizierten Impfung zum eigenen Schutz und dem des Kindes nicht ausgeschlossen werden. Zusätzliche sinnvolle Maßnahmen zum Schutz der Gesundheit von Mutter und Kind sind die Impfung enger Kontaktpersonen sowie das Schließen relevanter Impflücken junger Erwachsener, insbesondere bei Frauen im gebärfähigen Alter.

COVID-19 Vaccination in Pregnancy and Lactation: Current Research and Gaps in Understanding

The COVID-19 pandemic has demonstrated the urgent need to develop vaccine strategies optimized for pregnant people and their newborns, as both populations are at risk of developing severe disease. Although not included in COVID-19 vaccine development trials, pregnant people have had access to these vaccines since their initial release in the US and abroad. The rapid development and distribution of novel COVID-19 vaccines to people at risk, including those who are pregnant and lactating, presents an unprecedented opportunity to further our understanding of vaccine-induced immunity in these populations. In this review, we aim to summarize the literature to date on COVID-19 vaccination in pregnancy and lactation and highlight opportunities for investigation that may inform future maternal vaccine development and implementation strategies.

A literature review on beneficial role of vitamins and trace elements: Evidence from published clinical studies

COVID-19 is a kind of SARS-CoV-2 viral infectious pneumonia. This research aims to perform a bibliometric analysis of the published studies of vitamins and trace elements in the Scopus database with a special focus on COVID-19 disease. To achieve the goal of the study, network and density visualizations were used to introduce an overall picture of the published literature. Following the bibliometric analysis, we discuss the potential benefits of vitamins and trace elements on immune system function and COVID-19, supporting the discussion with evidence from published clinical studies. The previous studies show that D and A vitamins demonstrated a higher potential benefit, while Selenium, Copper, and Zinc were found to have favorable effects on immune modulation in viral respiratory infections among trace elements. The principles of nutrition from the findings of this research could be useful in preventing and treating COVID-19.

Inflammasome signaling in human placental trophoblasts regulates immune defense against Listeria monocytogenes infection

The human placenta is a dynamic organ that modulates physiological adaptations to pregnancy. To define the immunological signature of the human placenta, we performed unbiased profiling of secreted immune factors from human chorionic villi isolated from placentas at mid and late stages of pregnancy. We show that placental trophoblasts constitutively secrete the inflammasome-associated cytokines IL-1β and IL-18, which is blocked by NLRP3 inflammasome inhibitors and occurs without detectable gasdermin D cleavage. We further show that placenta-derived IL-1β primes monocytes for inflammasome induction to protect against Listeria monocytogenes infection. Last, we show that the human placenta responds to L. monocytogenes infection through additional inflammasome activation and that inhibition of this pathway sensitizes villi to infection. Our results thus identify the inflammasome as an important mechanism by which the human placenta regulates systemic and local immunity during pregnancy to defend against L. monocytogenes infection.

Robust innate immune responses at the placenta during early gestation may limit in utero HIV transmission

In 2019, >90% of new HIV infections in infants globally occurred vertically. Studies suggest intrauterine transmission most often occurs in the third trimester; however, there are no mechanistic studies to support these observations. We therefore obtained early/mid-gestation and term placentae from 20 HIV/Hepatitis B/CMV negative women. Isolated primary placental macrophages (Hofbauer cells [HCs]) were exposed to HIV-1_BaL and/or interferon (IFN)-α, IFN-β, IFN-λ1, and RIG-I-like receptor (RLR) agonists. qRT-PCR, FACS, ELISA, Luminex, and Western blot analyses determined expression of activation markers, co-receptors, viral antigen, cytokines, antiviral genes, and host proteins. Early gestation HCs express higher levels of CCR5 and exhibit a more activated phenotype. Despite downregulation of CCR5, term HCs were more susceptible to HIV replication. Early gestation HCs displayed a more activated phenotype than term HCs and HIV exposure lead to the further up-regulation of T-cell co-stimulatory and MHC molecules. Limited HIV replication in early/mid gestation HCs was associated with increased secretion of anti-inflammatory cytokines, chemokines, and a more robust antiviral immune response. In contrast, term HCs were more susceptible to HIV replication, associated with dampening of IFN-induced STAT1 and STAT2 protein activation. Treatment of early/mid gestation and term HCs, with type I IFNs or RLR agonists reduced HIV replication, underscoring the importance of IFN and RLR signaling in inducing an antiviral state. Viral recognition and antiviral immunity in early gestation HCs may prevent in utero HIV infection, whereas diminished antiviral responses at term can facilitate transmission. Defining mechanisms and specific timing of vertical transmission are critical for the development of specific vaccines and antiviral therapeutics to prevent new HIV infections in children globally.

Mother-to-child transmission is the main source of HIV infection in children globally. Studies suggest vertical transmission most often occurs late in the third trimester; however, there are no studies to support these observations. Our study shows that gestational age plays a significant role in the ability of placental macrophages to generate robust antiviral responses, which are necessary to prevent or reduce viral burden. Specifically, we show that viral recognition by RIG-I-like receptors and robust antiviral immune responses in placental cells during early gestation may prevent in utero HIV infection. We also demonstrate that term placental macrophages are limited in their antiviral capacity due to restricted type I IFN signaling. Understanding the mechanisms and timing of vertical transmission are important to understand for the development of specific vaccines and antiviral therapeutics to prevent new HIV infections in children globally.

Influenza Complicating Delivery Hospitalization and Its Association With Severe Maternal Morbidity in the United States, 2000-2018

OBJECTIVE

To characterize trends of an influenza diagnosis at delivery hospitalization and its association with severe maternal morbidity.

METHODS

We conducted a repeated cross-sectional analysis of delivery hospitalizations using the Nationwide Inpatient Sample from 2000 to 2018. We assessed the association between an influenza diagnosis at delivery hospitalization and severe maternal morbidity excluding transfusion per Centers for Disease Control and Prevention criteria. Secondary outcomes included maternal death and morbidity measures associated with influenza (mechanical intubation and ventilation, sepsis and shock, and acute respiratory distress syndrome [ARDS]) and obstetric complications (preterm birth and hypertensive disorders of pregnancy). We assessed trends of severe maternal morbidity by annual influenza season and the association between influenza and severe maternal morbidity using multivariable log-linear regression, adjusting for demographic, clinical, and hospital characteristics.

RESULTS

Of 74.7 million delivery hospitalizations, 23 per 10,000 were complicated by an influenza diagnosis. The rate of severe maternal morbidity was higher with an influenza diagnosis compared with those without influenza (86-410 cases vs 53-70 cases/10,000 delivery hospitalizations). Women with an influenza diagnosis at delivery hospitalization were at an increased risk of severe maternal morbidity compared with those without influenza (2.3 vs 0.7%; adjusted risk ratio 2.24, 95% CI 2.17-2.31). This association held for maternal death, mechanical intubation, sepsis and shock, and ARDS-as well as obstetric complications, including preterm birth and hypertensive disorders of pregnancy.

CONCLUSION

Pregnant women with influenza are at increased risk of severe maternal morbidity, as well as influenza-related maternal and obstetric complications. These results emphasize the importance of primary prevention and recognition of influenza infection during pregnancy to reduce downstream maternal morbidity and mortality.

Non-human Primate Models to Investigate Mechanisms of Infection-Associated Fetal and Pediatric Injury, Teratogenesis and Stillbirth

A wide array of pathogens has the potential to injure the fetus and induce teratogenesis, the process by which mutations in fetal somatic cells lead to congenital malformations. Rubella virus was the first infectious disease to be linked to congenital malformations due to an infection in pregnancy, which can include congenital cataracts, microcephaly, hearing impairment and congenital heart disease. Currently, human cytomegalovirus (HCMV) is the leading infectious cause of congenital malformations globally, affecting 1 in every 200 infants. However, our knowledge of teratogenic viruses and pathogens is far from complete. New emerging infectious diseases may induce teratogenesis, similar to Zika virus (ZIKV) that caused a global pandemic in 2016-2017; thousands of neonates were born with congenital microcephaly due to ZIKV exposure in utero, which also included a spectrum of injuries to the brain, eyes and spinal cord. In addition to congenital anomalies, permanent injury to fetal and neonatal organs, preterm birth, stillbirth and spontaneous abortion are known consequences of a broader group of infectious diseases including group B streptococcus (GBS), Listeria monocytogenes, Influenza A virus (IAV), and Human Immunodeficiency Virus (HIV). Animal models are crucial for determining the mechanism of how these various infectious diseases induce teratogenesis or organ injury, as well as testing novel therapeutics for fetal or neonatal protection. Other mammalian models differ in many respects from human pregnancy including placentation, labor physiology, reproductive tract anatomy, timeline of fetal development and reproductive toxicology. In contrast, non-human primates (NHP) most closely resemble human pregnancy and exhibit key similarities that make them ideal for research to discover the mechanisms of injury and for testing vaccines and therapeutics to prevent teratogenesis, fetal and neonatal injury and adverse pregnancy outcomes (e.g., stillbirth or spontaneous abortion). In this review, we emphasize key contributions of the NHP model pre-clinical research for ZIKV, HCMV, HIV, IAV, L. monocytogenes, Ureaplasma species, and GBS. This work represents the foundation for development and testing of preventative and therapeutic strategies to inhibit infectious injury of human fetuses and neonates.

Severe Heart Failure in an Infant Born to a Mother Diagnosed With Influenza A Before Delivery

Neonatal myocarditis and heart failure secondary to maternal infection with a myocarditis-associated virus in the weeks preceding delivery is rare. To our knowledge, this is the first report of an infant with myocarditis and heart failure in the setting of a maternal diagnosis of influenza A. Influenza is, however, known to be a cause of myocarditis in children, and several studies have shown vertical transmission of antibodies to influenza. Here, we present a full-term infant who presented with central cyanosis and respiratory distress at 30 minutes of life. No prenatal concerns had been identified. The infant continued to have poor saturations and mixed respiratory and metabolic acidosis despite intubation and administration of 100% FiO2. He was found to have severe biventricular dysfunction on echocardiogram. In discussion with the parents, it was elucidated that the mother had tested positive for influenza A 3 weeks before delivery. The presumptive diagnosis for this infant is heart failure secondary to influenza myocarditis that he contracted in utero. He demonstrated full return of heart function and was discharged home from the Cardiac Intensive Care Unit by day of life 10. Neonates with central cyanosis must be evaluated and treated emergently as these infants are at risk for life-threatening disease and downstream morbidity secondary to tissue hypoxia. The purpose of this case report is to highlight a rare but devastating etiology of cyanosis in neonates and to discuss the recommended course of evaluation and treatment for health care providers.

Coronavirus Diseases in Pregnant Women, the Placenta, Fetus, and Neonate

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the etiological agent of coronavirus disease 2019 (COVID-19), is similar to two other coronaviruses, severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), in causing life-threatening respiratory infections and systemic complications in both children and adults. As the COVID-19 pandemic has continued to spread globally, increasing numbers of pregnant women have become infected, raising concern not only for their health but also for the health of their infants. This chapter discusses the effects of coronavirus infections, e.g., MERS, SARS, and COVID 19, on pregnancy and describes the evolving knowledge of COVID 19 among pregnant women. The physiological changes that occur in pregnancy, especially changes in the immune system, are reviewed in terms of their effect on susceptibility to infectious diseases. The effects of COVID-19 on the placenta, fetus, and neonate are also reviewed, including potential clinical outcomes and issues relating to testing and diagnosis. The potential mechanisms of vertical transmission of the virus between pregnant women and their infants are analyzed, including intrauterine, intrapartum, and postpartum infections. Several recent studies have reported the detection of SARS-CoV-2 in tissues from the fetal side of the placenta, permitting the diagnosis of transplacental infection of the fetus by SARS-CoV-2. Placentas from infected mothers in which intrauterine transplacental transmission of SARS-CoV-2 has occurred demonstrate an unusual combination of pathology findings which may represent risk factors for placental as well as fetal infection.

Adverse Outcomes in Pregnant Women Hospitalized With Respiratory Syncytial Virus Infection: A Case Series

We identified 10 women hospitalized with respiratory syncytial virus infection during pregnancy. Diagnoses included pneumonia/atelectasis (5), respiratory failure (2), and sepsis (2). Six had obstetrical complications during hospitalization, including 1 induced preterm birth. One required intensive care unit admission and mechanical ventilation. Four infants had complications at birth.

Purification of sialoglycoproteins from bovine milk using serotonin-functionalized magnetic particles and their application against influenza A virus

Sialylation is involved in receptor-ligand interactions, communication between cells, and host-pathogen interactions and it is involved in the ability of glycoproteins of bovine milk to inhibit the influenza A virus (IAV). The present paper describes a simple and efficient method to isolate sialoglycoproteins from bovine milk using serotonin-magnetic particle conjugates. Then, the isolated glycoproteins were analysed by lectin blotting and LC-MS/MS. The N-glycans on isolated glycoproteins were characterized by MALDI-TOF/TOF-MS. The role of the isolated sialoglycoproteins against IAV was validated in vitro. As a result, there were 91 proteins and 17 sialylated N-glycans to be identified. The isolated proteins have ability to inhibit attachment of IAV mimics to MDCK cells. However, the role of inhibition was abolished when the sialic acid moieties were destroyed. This method could provide useful information for the large-scale production of sialoglycoproteins from bovine milk against IAV.

Vaccination in Pregnancy

BACKGROUND

Vaccination during pregnancy can protect both the expecting mother and the unborn and newborn child from infectious diseases.

METHODS

This review is based on publications retrieved by a selective literature search on the immunological particularities of infectious diseases affecting pregnant women, unborn children, and neonates, with particular attention to the guidelines of the German Standing Committee on Vaccinations (Ständige Impfkommission, STIKO) and the pertinent guidelines.

RESULTS

Vaccination during pregnancy protects the expecting mother from a severe course of a number of different infectious diseases. Vaccination with inactivated vaccines against influenza, tetanus, and pertussis is effective, safe, and well tolerated. Women who are pregnant or of child-bearing age should be immunized against tetanus according to the STIKO recommendations. All pregnant women from the second trimester onward should receive an inactivated quadrivalent influenza vaccine. The immunity acquired after vaccination with an acellular pertussis vaccine is present only for a limited time. In a cohort study involving 72,781 pregnant women, pertussis vaccination during pregnancy was found to yield 91% protection against pertussis for their subsequently born children in the first three months of life. Further types of vaccine can also be given during pregnancy if indicated. Additional reasonable measures to protect the health of mother and child include the vaccination of other persons in close contact as well as the closure of relevant vaccination gaps among young adults, particularly women of child-bearing age. Treating physicians play a crucial role in encouraging vaccine acceptance by their patients.

CONCLUSION

Maternal immunization is a safe and effective strategy for giving neo - nates passive immune protection against life-threatening infections by the vertical transmission of maternal antibodies until they are able to build up their own adaptive immunity.

Association between Viral Infections and Risk of Autistic Disorder: An Overview

Autism spectrum disorder (ASD) is a neurodevelopmental condition of the central nervous system (CNS) that presents with severe communication problems, impairment of social interactions, and stereotypic behaviours. Emerging studies indicate possible associations between viral infections and neurodegenerative and neurobehavioural conditions including autism. Viral infection during critical periods of early in utero neurodevelopment may lead to increased risk of autism in the offspring. This review is aimed at highlighting the association between viral infections, including viruses similar to COVID-19, and the aetiology of autism. A literature search was conducted using Pubmed, Ovid/Medline, and Google Scholar database. Relevant search terms included "rubella and autism", "cytomegalovirus and autism", "influenza virus and autism", "Zika virus and autism", "COVID-19 and autism". Based on the search terms, a total of 141 articles were obtained and studies on infants or children with congenital or perinatal viral infection and autistic behaviour were evaluated. The possible mechanisms by which viral infections could lead to autism include direct teratogenic effects and indirect effects of inflammation or maternal immune activation on the developing brain. Brain imaging studies have shown that the ensuing immune response from these viral infections could lead to disruption of the development of brain regions and structures. Hence, long-term follow up is necessary for infants whose mothers report an inflammatory event due to viral infection at any time during pregnancy to monitor for signs of autism. Research into the role of viral infection in the development of ASD may be one avenue of improving ASD outcomes in the future. Early screening and diagnosis to detect, and maybe even prevent ASD are essential to reduce the burden of this condition.

Incidence of influenza during pregnancy and association with pregnancy and perinatal outcomes in three middle-income countries: a multisite prospective longitudinal cohort study

BACKGROUND

Influenza vaccination during pregnancy prevents influenza among women and their infants but remains underused among pregnant women. We aimed to quantify the risk of antenatal influenza and examine its association with perinatal outcomes.

METHODS

We did a prospective cohort study in pregnant women in India, Peru, and Thailand. Before the 2017 and 2018 influenza seasons, we enrolled pregnant women aged 18 years or older with expected delivery dates 8 weeks or more after the season started. We contacted women twice weekly until the end of pregnancy to identify illnesses with symptoms of myalgia, cough, runny nose or nasal congestion, sore throat, or difficulty breathing and collected mid-turbinate nasal swabs from symptomatic women for influenza real-time RT-PCR testing. We assessed the association of antenatal influenza with preterm birth, late pregnancy loss (≥13 weeks gestation), small for gestational age (SGA), and birthweight of term singleton infants using Cox proportional hazards models or generalised linear models to adjust for potential confounders.

FINDINGS

Between March 13, 2017, and Aug 3, 2018, we enrolled 11 277 women with a median age of 26 years (IQR 23-31) and gestational age of 19 weeks (14-24). 1474 (13%) received influenza vaccines. 310 participants (3%) had influenza (270 [87%] influenza A and 40 [13%] influenza B). Influenza incidences weighted by the population of women of childbearing age in each study country were 88·7 per 10 000 pregnant woman-months (95% CI 68·6 to 114·8) during the 2017 season and 69·6 per 10 000 pregnant woman-months (53·8 to 90·2) during the 2018 season. Antenatal influenza was not associated with preterm birth (adjusted hazard ratio [aHR] 1·4, 95% CI 0·9 to 2·0; p=0·096) or having an SGA infant (adjusted relative risk 1·0, 95% CI 0·8 to 1·3, p=0·97), but was associated with late pregnancy loss (aHR 10·7, 95% CI 4·3 to 27·0; p<0·0001) and reduction in mean birthweight of term, singleton infants (-55·3 g, 95% CI -109·3 to -1·4; p=0·0445).

INTERPRETATION

Women had a 0·7-0·9% risk of influenza per month of pregnancy during the influenza season, and antenatal influenza was associated with increased risk for some adverse pregnancy outcomes. These findings support the added value of antenatal influenza vaccination to improve perinatal outcomes.

FUNDING

US Centers for Disease Control and Prevention.

TRANSLATIONS

For the Thai, Hindi, Marathi and Spanish translations of the abstract see Supplementary Materials section.

Influenza in High-Risk Hosts-Lessons Learned from Animal Models

Factoring significantly into the global burden of influenza disease are high-risk populations that suffer the bulk of infections. Classically, the very young, very old, and pregnant women have been identified as high-risk populations; however, recent research has uncovered several other conditions that contribute to severe infection. By using varied animal models, researchers have identified molecular mechanisms underpinning the increased likelihood for infection due to obesity and malnourishment, as well as insight into the role sex hormones play in antiviral immunity in males, in females, and across the life span. Additionally, novel comorbidity models have helped elucidate the role of chronic infectious and genetic diseases in influenza virus pathogenesis. Animal models play a vital role in understanding the contribution of host factors to influenza severity and immunity. An in-depth understanding of these host factors represents an important step in reducing the burden of influenza among the growing number of people living with one or more chronic medical conditions.

Innate Immune Responses to Acute Viral Infection During Pregnancy

Immunological adaptations in pregnancy allow maternal tolerance of the semi-allogeneic fetus but also increase maternal susceptibility to infection. At implantation, the endometrial stroma, glands, arteries and immune cells undergo anatomical and functional transformation to create the decidua, the specialized secretory endometrium of pregnancy. The maternal decidua and the invading fetal trophoblast constitute a dynamic junction that facilitates a complex immunological dialogue between the two. The decidual and peripheral immune systems together assume a pivotal role in regulating the critical balance between tolerance and defense against infection. Throughout pregnancy, this equilibrium is repeatedly subjected to microbial challenge. Acute viral infection in pregnancy is associated with a wide spectrum of adverse consequences for both mother and fetus. Vertical transmission from mother to fetus can cause developmental anomalies, growth restriction, preterm birth and stillbirth, while the mother is predisposed to heightened morbidity and maternal death. A rapid, effective response to invasive pathogens is therefore essential in order to avoid overwhelming maternal infection and consequent fetal compromise. This sentinel response is mediated by the innate immune system: a heritable, highly evolutionarily conserved system comprising physical barriers, antimicrobial peptides (AMP) and a variety of immune cells—principally neutrophils, macrophages, dendritic cells, and natural killer cells—which express pattern-receptors that detect invariant molecular signatures unique to pathogenic micro-organisms. Recognition of these signatures during acute infection triggers signaling cascades that enhance antimicrobial properties such as phagocytosis, secretion of pro-inflammatory cytokines and activation of the complement system. As well as coordinating the initial immune response, macrophages and dendritic cells present microbial antigens to lymphocytes, initiating and influencing the development of specific, long-lasting adaptive immunity. Despite extensive progress in unraveling the immunological adaptations of pregnancy, pregnant women remain particularly susceptible to certain acute viral infections and continue to experience mortality rates equivalent to those observed in pandemics several decades ago. Here, we focus specifically on the pregnancy-induced vulnerabilities in innate immunity that contribute to the disproportionately high maternal mortality observed in the following acute viral infections: Lassa fever, Ebola virus disease (EVD), dengue fever, hepatitis E, influenza, and novel coronavirus infections.

Maternal Influenza A Virus Infection Restricts Fetal and Placental Growth and Adversely Affects the Fetal Thymic Transcriptome

Maternal influenza A viral infections in humans are associated with low birth weight, increased risk of pre-term birth, stillbirth and congenital defects. To examine the effect of maternal influenza virus infection on placental and fetal growth, pregnant C57BL/6 mice were inoculated intranasally with influenza A virus A/CA/07/2009 pandemic H1N1 or phosphate-buffered saline (PBS) at E3.5, E7.5 or E12.5, and the placentae and fetuses collected and weighed at E18.5. Fetal thymuses were pooled from each litter. Placentae were examined histologically, stained by immunohistochemistry (IHC) for CD34 (hematopoietic progenitor cell antigen) and vascular channels quantified. RNA from E7.5 and E12.5 placentae and E7.5 fetal thymuses was subjected to RNA sequencing and pathway analysis. Placental weights were decreased in litters inoculated with influenza at E3.5 and E7.5. Placentae from E7.5 and E12.5 inoculated litters exhibited decreased labyrinth development and the transmembrane protein 150A gene was upregulated in E7.5 placentae. Fetal weights were decreased in litters inoculated at E7.5 and E12.5 compared to controls. RNA sequencing of E7.5 thymuses indicated that 957 genes were downregulated ≥2-fold including Mal, which is associated with Toll-like receptor signaling and T cell differentiation. There were 28 upregulated genes. It is concluded that maternal influenza A virus infection impairs fetal thymic gene expression as well as restricting placental and fetal growth.

Obesity as a contributor to immunopathology in pregnant and non-pregnant adults with COVID-19

The ongoing coronavirus disease 2019 (COVID‐19) pandemic has led to a global public health emergency with the need to identify vulnerable populations who may benefit from increased screening and healthcare resources. Initial data suggest that overall, pregnancy is not a significant risk factor for severe coronavirus disease 2019 (COVID‐19). However, case series have suggested that maternal obesity is one of the most important comorbidities associated with more severe disease. In obese individuals, suppressors of cytokine signaling are upregulated and type I and III interferon responses are delayed and blunted leading to ineffective viral clearance. Obesity is also associated with changes in systemic immunity involving a wide range of immune cells and mechanisms that lead to low‐grade chronic inflammation, which can compromise antiviral immunity. Macrophage activation in adipose tissue can produce low levels of pro‐inflammatory cytokines (TNF‐α, IL‐1β, IL‐6). Further, adipocyte secretion of leptin is pro‐inflammatory and high circulating levels of leptin have been associated with mortality in patients with acute respiratory distress syndrome. The synergistic effects of obesity‐associated delays in immune control of COVID‐19 with mechanical stress of increased adipose tissue may contribute to a greater risk of pulmonary compromise in obese pregnant women. In this review, we bring together data regarding obesity as a key co‐morbidity for COVID‐19 in pregnancy with known changes in the antiviral immune response associated with obesity. We also describe how the global burden of obesity among reproductive age women has serious public health implications for COVID‐19.

Pregnancy Downregulates Plasmablast Metabolic Gene Expression Following Influenza Without Altering Long-Term Antibody Function

While the majority of influenza-infected individuals show no or mild symptomatology, pregnant women are at higher risk of complications and infection-associated mortality. Although enhanced lung pathology and dysregulated hormones are thought to underlie adverse pregnancy outcomes following influenza infection, how pregnancy confounds long-term maternal anti-influenza immunity remains to be elucidated. Previously, we linked seasonal influenza infection to clinical observations of adverse pregnancy outcomes, enhanced lung and placental histopathology, and reduced control of viral replication in lungs of infected pregnant mothers. Here, we expand on this work and demonstrate that lower infectious doses of the pandemic A/California/07/2009 influenza virus generated adverse gestational outcomes similar to higher doses of seasonal viruses. Mice infected during pregnancy demonstrated lower hemagglutination inhibition and neutralizing antibody titers than non-pregnant animals until 63 days post infection. These differences in humoral immunity suggest that pregnancy impacts antibody maturation mechanisms without alterations to B cell frequency or antibody secretion. This is further supported by transcriptional analysis of plasmablasts, which demonstrate downregulated B cell metabolism and post-translational modification systems only among pregnant animals. In sum, these findings corroborate a link between adverse pregnancy outcomes and severe pathology observed during pandemic influenza infection. Furthermore, our data propose that pregnancy directly confounds humoral responses following influenza infection which resolves post-partem. Additional studies are required to specify the involvement of plasmablast metabolism with early humoral immunity abnormalities to best guide vaccination strategies and improve our understanding of the immunological consequences of pregnancy.

Is the Host Viral Response and the Immunogenicity of Vaccines Altered in Pregnancy?

The intricacy of the maternal immune system arises from its ability to prevent a maternal immune response against a semi-allogenic fetus, while protecting the mother against harmful pathogens. However, these immunological adaptations may also make pregnant women vulnerable to developing adverse complications from respiratory viral infections. While the influenza and SARS pandemics support this theory, there is less certainty regarding the clinical impact of SARS-CoV-2 in pregnancy. In the current COVID-19 pandemic, vaccine development is key to public preventative strategies. Whilst most viral vaccines are able to induce a seroprotective antibody response, in some high-risk individuals this may not correlate with clinical protection. Some studies have shown that factors such as age, gender, and chronic illnesses can reduce their effectiveness and in this review, we discuss how pregnancy may affect the efficacy and immunogenicity of vaccines. We present literature to support the hypothesis that pregnant women are more susceptible to respiratory viral infections and may not respond to vaccines as effectively. In particular, we focus on the clinical implications of important respiratory viral infections such as influenza during pregnancy, and the pregnancy induced alterations in important leukocytes such as TFH, cTFH and B cells, which play an important role in generating long-lasting and high-affinity antibodies. Finally, we review how this may affect the efficacy of vaccines against influenza in pregnancy and highlight areas that require further research.

Does the human placenta express the canonical cell entry mediators for SARS-CoV-2?

The pandemic of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected more than 10 million people, including pregnant women. To date, no consistent evidence for the vertical transmission of SARS-CoV-2 exists. The novel coronavirus canonically utilizes the angiotensin-converting enzyme 2 (ACE2) receptor and the serine protease TMPRSS2 for cell entry. Herein, building upon our previous single-cell study (Pique-Regi et al., 2019), another study, and new single-cell/nuclei RNA-sequencing data, we investigated the expression of ACE2 and TMPRSS2 throughout pregnancy in the placenta as well as in third-trimester chorioamniotic membranes. We report that co-transcription of ACE2 and TMPRSS2 is negligible in the placenta, thus not a likely path of vertical transmission for SARS-CoV-2. By contrast, receptors for Zika virus and cytomegalovirus, which cause congenital infections, are highly expressed by placental cell types. These data show that the placenta minimally expresses the canonical cell-entry mediators for SARS-CoV-2.

Paradoxical long-term impact of maternal influenza infection on neonates and infants

Background

Pregnant women are at high risk of influenza-related morbidity and mortality. In addition, maternal influenza infection may lead to adverse birth outcomes. However, there is insufficient data on long-term impact of maternal influenza infection.

Methods

This study was conducted to assess the impact of maternal influenza infection on birth outcomes and long-term influence on infants by merging the Korea National Health Insurance (KNHI) claims database and National Health Screening Program for Infants and Children (NHSP-IC). Mother-offspring pairs were categorized by maternal influenza infection based on the ICD-10 code.

Results

Multivariate analysis revealed that maternal influenza infection significantly increased the risk of preterm birth (OR 1.408) and low birth weight (OR 1.198) irrespective of gestational age. The proportion of low birth weight neonates was significantly higher in influenza-infected women compared to those without influenza. However, since the fourth health screening (30–80 months after birth), the fraction of underweight was no longer different between children from influenza-infected and non-infected mothers, whereas the rates of overweight increased paradoxically in those born to mothers with influenza infection.

Conclusions

Maternal influenza infection might have long-term effects on the health of children and adolescents even after infancy.

Pregnancy Induces a Steady-State Shift in Alveolar Macrophage M1/M2 Phenotype That Is Associated With a Heightened Severity of Influenza Virus Infection: Mechanistic Insight Using Mouse Models

BACKGROUND

Influenza virus infection during pregnancy is associated with enhanced disease severity. However, the underlying mechanisms are still not fully understood. We hypothesized that normal alveolar macrophage (AM) functions, which are central to maintaining lung immune homeostasis, are altered during pregnancy and that this dysregulation contributes to the increased inflammatory response to influenza virus infection.

METHODS

Time-mated BALB/c mice were infected with a low dose of H1N1 influenza A virus at gestation day 9.5. Inflammatory cells in bronchoalveolar lavage (BAL) fluid were assessed by flow cytometry.

RESULTS

Our findings confirm previous reports of increased severity of influenza virus infection in pregnant mice. The heightened inflammatory response detected in BAL fluid from infected pregnant mice was characterized by neutrophil-rich inflammation with concomitantly reduced numbers of AM, which were slower to return to baseline counts, compared with nonpregnant infected mice. The increased infection severity and inflammatory responses to influenza during pregnancy were associated with a pregnancy-induced shift in AM phenotype at homeostatic baseline, from the M1 (ie, classical activation) state toward the M2 (ie, alternative activation) state, as evidence by increased expression of CD301 and reduced levels of CCR7.

CONCLUSION

These results show that pregnancy is associated with an alternatively activated phenotype of AM before infection, which may contribute to heightened disease severity.

Nucleic Acid-Based Screening of Maternal Serum to Detect Viruses in Women with Labor or PROM

The purpose of this study was to determine whether timing of the initiating event of spontaneous labor (either uterine contractions with intact fetal membranes or rupture of membranes prior to labor (PROM)) is associated with maternal viral infection. It was a prospective case control study of women with either spontaneous labor or PROM occurring < 37 weeks' gestation ("cases") or at term ("controls"). An initial unbiased screen for viruses was performed with next-generation sequencing (NGS) in serum pooled from eight cases delivered by C/S and represents a range of gestational ages, membrane rupture status, and presence or absence of chorioamnionitis. Custom PCR was used to query individual patient samples from the original cohort. The NGS screen generated 15 million reads. Seven unique viral sequences were detected in two cases, all identified as torque teno virus (TTV), an ubiquitous DNA anellovirus of no known pathogenicity. Using nested and semi-nested PCR, sera from 72 patients (47 cases and 25 matched controls, stratified by ROM status) were screened for the 3 subtypes of anelloviruses (TTV, TTMDV, or TTMV). These were found in 43/47 cases (91%) and 16/25 controls (64%) (p = 0.012, OR = 5.9 (95% CI = 1.4-29.9)). In logistic regression, pregnant women with at least one type of anellovirus were more likely to experience preterm labor than those with no anellovirus (p = 0.03, aOR = 4.6, CI = 1.2-18.7). Among women experiencing a spontaneous initiating event of labor, TTV virus was more likely to be present in the serum of preterm than term patients. TTV may have a role in determining the timing of parturition.

The brain-placental axis: Therapeutic and pharmacological relevancy to pregnancy

The placenta plays a critical role in mammalian reproduction. Although it is a transient organ, its function is indispensable to communication between the mother and fetus, and supply of nutrients and oxygen to the growing fetus. During pregnancy, the placenta is vulnerable to various intrinsic and extrinsic conditions which can result in increased risk of fetal neurodevelopmental disorders as well as fetal death. The placenta controls the neuroendocrine secretion in the brain as a means of adaptive processes to safeguard the fetus from adverse programs, to optimize fetal development and other physiological changes necessary for reproductive success. Although a wealth of information is available on neuroendocrine functions in pregnancy, they are largely limited to the regulation of hypothalamus-pituitary-adrenal/gonad (HPA/ HPG) axis, particularly the oxytocin and prolactin system. There is a major gap in knowledge on systems-level functional interaction between the brain and placenta. In this review, we aim to outline the current state of knowledge about the brain-placental axis with description of the functional interactions between the placenta and the maternal and fetal brain. While describing the brain-placental interactions, a special emphasis has been given on the therapeutics and pharmacology of the placental receptors to neuroligands expressed in the brain during gestation. As a key feature of this review, we outline the prospects of integrated pharmacogenomics, single-cell sequencing and organ-on-chip systems to foster priority areas in this field of research. Finally, we remark on the application of precision genomics approaches to study the brain-placental axis in order to accelerate personalized medicine and therapeutics to treat placental and fetal brain disorders.

Pregnancy-Induced Alterations in NK Cell Phenotype and Function

Pregnant women are particularly susceptible to complications of influenza A virus infection, which may result from pregnancy-induced changes in the function of immune cells, including natural killer (NK) cells. To better understand NK cell function during pregnancy, we assessed the ability of the two main subsets of NK cells, CD56^dim, and CD56^bright NK cells, to respond to influenza-virus infected cells and tumor cells. During pregnancy, CD56^dim and CD56^bright NK cells displayed enhanced functional responses to both infected and tumor cells, with increased expression of degranulation markers and elevated frequency of NK cells producing IFN-γ. To better understand the mechanisms driving this enhanced function, we profiled CD56^dim and CD56^bright NK cells from pregnant and non-pregnant women using mass cytometry. NK cells from pregnant women displayed significantly increased expression of several functional and activation markers such as CD38 on both subsets and NKp46 on CD56^dim NK cells. NK cells also displayed diminished expression of the chemokine receptor CXCR3 during pregnancy. Overall, these data demonstrate that functional and phenotypic shifts occur in NK cells during pregnancy that can influence the magnitude of the immune response to both infections and tumors.

Potential effect of germanium exposure on the risk of influenza-like illness in housewives in Shanxi Province, China

Few studies have examined the relationship between exposure to germanium (Ge) and the risk of influenza-like illness (ILI). Therefore, we investigated the association of Ge exposure and its interaction with single nucleotide polymorphisms (SNPs) related to Phase II metabolism on ILI risk among housewives in Shanxi Province, northern China. This cross-sectional study enrolled 373 housewives. Information on the housewives' characteristics and the frequency of ILI was collected by questionnaire. We analyzed the Ge concentrations in hair samples taken from near the scalp at the back of the head. Blood samples were used to identify SNPs related to Phase II metabolism. The results suggested that the hair Ge concentration was associated with ILI risk with an adjusted odds ratio and 95% confidence interval of 2.59 (1.61-4.19). A significant dose-response relationship was observed without or with adjusting for confounders. We did not observe any interaction effect between the hair Ge concentration and the SNPs on ILI risk. We found that high dietary consumption of meat and fried foods was positively correlated with the hair Ge concentration. Therefore, chronic Ge exposure may be a risk factor for an increased frequency of ILI in housewives.

Serum markers of B-cell activation in pregnancy during late gestation, delivery, and the postpartum period

PROBLEM

B cells are vital for the normal evolution of pregnancy due to their humoral and possible regulatory activities. Our group and others have documented that circulating B-cell subsets undergo changes from normal late pregnancy to the postpartum period. However, the underlying mechanisms are poorly understood. Therefore, this study examined the degree of B-cell activation in normal pregnancy by analyzing the levels of serum markers in healthy pregnant women during the third trimester of pregnancy, the day of delivery, and the postpartum period.

METHOD OF STUDY

A prospective study including pregnant and non-pregnant women attending routine care was undertaken at a hospital clinic. Sociodemographic and clinical data were collected, along with peripheral blood samples. The serum levels of soluble CD23 (sCD23), B-cell-activating factor (BAFF), kappa (κ) and lambda (λ) free light chains (FLC), IgA, IgG, and IgM were quantified.

RESULTS

Our study included 43 third trimester pregnant and 35 non-pregnant women. In the pregnant women, the median levels of sCD23, BAFF, IgG, and κ FLC were significantly higher during the postpartum period than during the third trimester of pregnancy. Compared to the non-pregnant women, the third trimester pregnant women had higher median BAFF levels and lower sCD23, IgA, IgG, and FLC levels.

CONCLUSION

Changes in serum markers of B-cell kinetics that occur during pregnancy often persist into the postpartum period and affect the secretion of immunoglobulins from different classes. Further studies are needed to clarify the biological significance of our observations.

Hormonal Regulation of Physiology, Innate Immunity and Antibody Response to H1N1 Influenza Virus Infection During Pregnancy

In 2009, the H1N1 swine flu pandemic highlighted the vulnerability of pregnant women to influenza viral infection. Pregnant women infected with influenza A virus were at increased risk of hospitalization and severe acute respiratory distress syndrome (ARDS), which is associated with high mortality, while their newborns had an increased risk of pre-term birth or low birth weight. Pregnant women have a unique immunological profile modulated by the sex hormones required to maintain pregnancy, namely progesterone and estrogens. The role of these hormones in coordinating maternal immunotolerance in uterine tissue and cellular subsets has been well researched; however, these hormones have wide-ranging effects outside the uterus in modulating the immune response to disease. In this review, we compile research findings in the clinic and in animal models that elaborate on the unique features of H1N1 influenza A viral pathogenesis during pregnancy, the crosstalk between innate immune signaling and hormonal regulation during pregnancy, and the role of pregnancy hormones in modulating cellular responses to influenza A viral infection at mid-gestation. We highlight the ways in which lung architecture and function is stressed by pregnancy, increasing baseline inflammation prior to infection. We demonstrate that infection disrupts progesterone production and upregulates inflammatory mediators, such as cyclooxygenase-2 (COX-2) and prostaglandins, resulting in pre-term labor and spontaneous abortions. Lastly, we profile the ways in which pregnancy alters innate and adaptive cellular immune responses to H1N1 influenza viral infection, and the ways in which these protect fetal development at the expense of effective long-term immune memory. Thus, we highlight advancements in the field of reproductive immunology in response to viral infection and illustrate how that knowledge might be used to develop more effective post-infection therapies and vaccination strategies.

A study on mother-to-fetus/infant transmission of influenza A(H7N9) virus: Two case reports and a review of literature

OBJECTIVES

The prevention strategies for mother-to-fetus/infant transmission of H7N9 virus have not been well understood, and the study on this subject will provide further insights.

METHODS

Reverse transcriptase polymerase chain reaction assay was undertaken to detect H7N9 virus in samples from a pregnant women, a postpartum woman, and their fetus/infant. Pathological features of tissues from the dead fetus were evaluated with hematoxylin and eosin staining. Hemagglutination inhibition assay was used to detect virus-specific antibodies. Furthermore, relevant literatures were reviewed and analyzed.

RESULTS

A 28-year-old pregnant woman was hospitalized for H7N9 infection and prescribed with oseltamivir and peramivir for 2 days before admission. The fetal heart beating stopped on day 4, the dead fetus was delivered on day 13, and the woman expired on day 26. All fetal tissues were H7N9 virus-negative. A 28-year-old woman delivered a newborn on December 20, 2016. Five days later, she developed influenza-like symptoms and was confirmed with H7N9 infection. She had close contact with her infant for 9 days. Oseltamivir and peramivir were prescribed within 2 days after illness onset. A throat swab and a pair of serum samples from the infant were all negative for H7N9 virus during 4-week follow-up. In total, ten studies referring to transplacental transmission and four reports on maternal infection of H7N9 virus were reviewed and analyzed.

CONCLUSION

No evidence showed H7N9 virus infection in both fetus and infant. The early administration of neuraminidase inhibitor seemed beneficial in preventing mother-to-fetus/infant transmission of H7N9 virus.

Australian caregivers' perceptions of influenza vaccination in pregnancy: A mixed methods exploration

BACKGROUND

Pregnant women and their unborn children are at high risk from both pandemic and seasonal influenza.

AIM

To explore views about influenza vaccination during pregnancy, in a pandemic and immediate post-pandemic context, among mothers and other carers of young children.

METHODS

In a mixed methods study, caregivers from 16 childcare centres in Sydney, Australia, were surveyed in November and December 2009, and interviews were conducted with caregivers from six childcare centres between June 2009 and May 2011.

FINDINGS

Emerging themes from 41 interviews conducted with mothers included: 'pregnancy as a protected state', 'risk negotiation' and 'centrality of healthcare worker interaction'. Of 972 surveys distributed, 431 were completed (a response rate of 44%). Respondents perceived pandemic influenza risks to be greater for pregnant women than for their unborn children. Only 2% (9/383) of women reported being vaccinated against swine flu during pregnancy and 45% (168/383) indicated intent to receive swine flu vaccination in a future pregnancy.

DISCUSSION

The low rates of maternal influenza vaccination revealed in this study contrast to recent gains in vaccine uptake. Vaccination decision-making in pregnancy can be complex and contextually driven for some women. Healthcare workers, including midwives, have a key role in addressing women's concerns about maternal influenza vaccination in both pandemic and interpandemic periods.

CONCLUSIONS

Policy makers need to be cognisant of women's concerns and develop resources for both pregnant women and healthcare workers as part of both future pandemic planning and seasonal vaccination efforts.

Immunological Tolerance, Pregnancy, and Preeclampsia: The Roles of Semen Microbes and the Father

Although it is widely considered, in many cases, to involve two separable stages (poor placentation followed by oxidative stress/inflammation), the precise originating causes of preeclampsia (PE) remain elusive. We have previously brought together some of the considerable evidence that a (dormant) microbial component is commonly a significant part of its etiology. However, apart from recognizing, consistent with this view, that the many inflammatory markers of PE are also increased in infection, we had little to say about immunity, whether innate or adaptive. In addition, we focused on the gut, oral and female urinary tract microbiomes as the main sources of the infection. We here marshall further evidence for an infectious component in PE, focusing on the immunological tolerance characteristic of pregnancy, and the well-established fact that increased exposure to the father's semen assists this immunological tolerance. As well as these benefits, however, semen is not sterile, microbial tolerance mechanisms may exist, and we also review the evidence that semen may be responsible for inoculating the developing conceptus (and maybe the placenta) with microbes, not all of which are benign. It is suggested that when they are not, this may be a significant cause of PE. A variety of epidemiological and other evidence is entirely consistent with this, not least correlations between semen infection, infertility and PE. Our view also leads to a series of other, testable predictions. Overall, we argue for a significant paternal role in the development of PE through microbial infection of the mother via insemination.

H1N1 influenza virus infection results in adverse pregnancy outcomes by disrupting tissue-specific hormonal regulation

Increased susceptibility to influenza virus infection during pregnancy has been attributed to immunological changes occurring before and during gestation in order to “tolerate” the developing fetus. These systemic changes are most often characterized by a suppression of cell-mediated immunity and elevation of humoral immune responses referred to as the Th1-Th2 shift. However, the underlying mechanisms which increase pregnant mothers’ risk following influenza virus infection have not been fully elucidated. We used pregnant BALB/c mice during mid- to late gestation to determine the impact of a sub-lethal infection with A/Brisbane/59/07 H1N1 seasonal influenza virus on completion of gestation. Maternal and fetal health status was closely monitored and compared to infected non-pregnant mice. Severity of infection during pregnancy was correlated with premature rupture of amniotic membranes (PROM), fetal survival and body weight at birth, lung viral load and degree of systemic and tissue inflammation mediated by innate and adaptive immune responses. Here we report that influenza virus infection resulted in dysregulation of inflammatory responses that led to pre-term labor, impairment of fetal growth, increased fetal mortality and maternal morbidity. We observed significant compartment-specific immune responses correlated with changes in hormonal synthesis and regulation. Dysregulation of progesterone, COX-2, PGE2 and PGF2α expression in infected pregnant mice was accompanied by significant remodeling of placental architecture and upregulation of MMP-9 early after infection. Collectively these findings demonstrate the potential of a seasonal influenza virus to initiate a powerful pro-abortive mechanism with adverse outcomes in fetal health.

Maternal immunology is finely balanced to maintain a tolerant and supportive molecular environment for the developing fetus while continuing surveillance against foreign microbial threats. Influenza viral infection during pregnancy is a significant clinical risk for mothers and their newborns, increasing hospitalization, preterm birth, low birth weight, and maternal and neonatal deaths worldwide. In a mouse pregnancy model, we show how influenza virus infection disrupts the delicate and interconnected cytokine and hormonal signaling pathways that respond to respiratory pathogens. The health of mothers and offspring was impacted in our study, after pregnant mothers’ lung and placental architecture was compromised by infection. Influenza virus infection increased the stress on the mother’s body already present due to pregnancy, or reversed the hormonal environment required to establish and maintain healthy pregnancy. By dissecting the effects of inflammation post-infection throughout the mother’s anatomy, we can tailor anti-inflammatory treatments for the pregnant population. Also, thorough knowledge of immune responses will assist in tailoring vaccine design and dosage for this delicate period of women’s immunological and reproductive health.

Effects of prior influenza virus vaccination on maternal antibody responses: Implications for achieving protection in the newborns

BACKGROUND

In the US, influenza vaccination is recommended annually to everyone ≥6months. Prior receipt of influenza vaccine can dampen antibody responses to subsequent vaccination. This may have implications for pregnant women and their newborns, groups at high risk for complications from influenza infection.

OBJECTIVE

This study examined effects of prior vaccination on maternal and cord blood antibody levels in a cohort of pregnant women in the US.

STUDY DESIGN

Influenza antibody titers were measured in 141 pregnant women via the hemagglutination inhibition (HAI) assay prior to receipt of quadrivalent influenza vaccine, 30days post-vaccination, and at delivery (maternal and cord blood). Logistic regression analyses adjusting for age, BMI, parity, gestational age at vaccination, and year of vaccination compared HAI titers, seroprotection, and seroconversion in women with versus without vaccination in the prior year.

RESULTS

Compared to those without vaccination in the previous year (n=50), women with prior vaccination (n=91) exhibited higher baseline antibody titers and/or seroprotection rates against all four strains after controlling for covariates. Prior vaccination also predicted lower antibody responses and seroconversion rates at one month post-vaccination. However, at delivery, there were no significant differences in antibody titers or seroprotection rates in women or newborns, and no meaningful differences in the efficiency of antibody transfer, as indicated by the ratio of cord blood to maternal antibody titers at the time of delivery.

CONCLUSION

In this cohort of pregnant women, receipt of influenza vaccine the previous year predicted higher baseline antibody titers and decreased antibody responses at one month post-vaccination against all influenza strains. However, prior maternal vaccination did not significantly affect either maternal antibody levels at delivery or antibody levels transferred to the neonate. This study is registered with the NIH as a clinical trial (NCT02148874).

Epidemiological and Serological Investigation into the Role of Gestational Maternal Influenza Virus Infection and Autism Spectrum Disorders

The causes of most cases of autism spectrum disorders (ASD) are unknown. Some epidemiological studies suggest that maternal gestational influenza virus infection may increase the risk of ASD in offspring. Here, we describe an analysis of a large birth cohort with results based on questionnaires that prospectively addressed subjective reports of influenza-like illness and serological assays for objective determination of influenza virus infection. Although serologic evidence of gestational influenza virus infection alone was not associated with risk, positive serology and symptoms of influenza-like illness cannot yet be definitely ruled out as a risk factor.

The literature concerning gestational maternal influenza virus infection and risk of autism spectrum disorders (ASD) is inconclusive. To address this uncertainty, we obtained information from questionnaires and samples from the Autism Birth Cohort, a prospective birth cohort comprising mothers, fathers, and offspring recruited in Norway in 1999 to 2008. Through questionnaires, referrals, and linkages to the Norwegian National Patient Registry, we identified 338 mothers of children with ASD and 348 frequency-matched controls for whom plasma samples that had been collected midpregnancy and after delivery were available for influenza virus serology via luciferase immunoprecipitation and hemagglutinin inhibition assays for influenza virus strains circulating during the study period. Assay data were combined to define serological status and integrated with self-reports of influenza-like illness to estimate ASD risk. Neither influenza A nor influenza B virus infection was associated with increased ASD risk. Integration of reports of symptoms of influenza-like illness with serology revealed an increase in risk for seropositive women with symptoms, but this increase did not achieve statistical significance (a level of P < 0.05) in the comparison with seronegative women without symptoms (adjusted odds ratio, 1.93; 95% confidence interval, 0.95 to 3.89; P = 0.068). Although chance may explain our findings, the magnitude of the potential association may be of biological importance, and dismissing our findings could result in failure to detect a bona fide association (type II error). If the association is true, we posit that the risk is due to activation of the maternal immune system following infection rather than direct fetal infection. Data on levels of cytokines or other mediators of inflammation would allow us to test the validity of this hypothesis.

IMPORTANCE The causes of most cases of autism spectrum disorders (ASD) are unknown. Some epidemiological studies suggest that maternal gestational influenza virus infection may increase the risk of ASD in offspring. Here, we describe an analysis of a large birth cohort with results based on questionnaires that prospectively addressed subjective reports of influenza-like illness and serological assays for objective determination of influenza virus infection. Although serologic evidence of gestational influenza virus infection alone was not associated with risk, positive serology and symptoms of influenza-like illness cannot yet be definitely ruled out as a risk factor.

Effect of Pregnancy on Interferon Gamma Release Assay and Tuberculin Skin Test Detection of Latent TB Infection Among HIV-Infected Women in a High Burden Setting

BACKGROUND

Peripartum immunologic changes may affect latent tuberculosis infection (LTBI) diagnostic performance among HIV-infected women.

METHODS

HIV-infected women were serially tested with tuberculin skin test (TST) and interferon gamma release assay [QuantiFERON TB Gold In-tube (QFT)] in pregnancy and 6 weeks postpartum in Kenya. Prevalence, sensitivity and agreement, and correlates of QFT/TST positivity were assessed. Quantitative QFT mitogen and Mycobacterium tuberculosis antigen (Mtb-Ag) responses were compared by peripartum stage. Incidence of test conversion at 6 weeks postpartum was evaluated in baseline TST-/QFT- women.

RESULTS

Among 100 HIV-infected women, median age was 26 years, median CD4 was 555 cells per cubic millimeter, and 88% were on antiretrovirals. More women were QFT+ than TST+ in both pregnancy (35.4% vs. 13.5%, P = 0.001) and postpartum (29.6% vs. 14.8%, P < 0.001). Among 18 consistently QFT+ women, 8 (44%) converted from TST- to TST+, with improved test agreement postpartum (56.9%, κ = 0.20 to 82.4%, κ = 0.60). Three initially QFT-/TST- women had test conversion (TST+ and/or QFT+), suggesting new infection (incidence 13.4/100 person-years). Mean QFT mitogen (4.46 vs. 7.64 IU/mL, P < 0.001) and Mtb-Ag (1.03 vs. 1.54 IU/mL, P = 0.03) responses were lower among all women retested in pregnancy vs. postpartum, and specifically among persistently QFT+ women (Mtb-Ag: 3.46 vs. 4.48 IU/mL, P = 0.007). QFT indeterminate rate was higher in pregnancy (16%) compared with postpartum (0%) because of lower mitogen response.

CONCLUSIONS

QFT identified >2-fold more women with LTBI compared with TST in pregnancy and postpartum. Lower QFT Mtb-Ag and mitogen responses in pregnancy compared with postpartum suggest that pregnancy-associated immunologic changes may influence LTBI test performance.