Pandemic influenza and pregnant women

Influenza pandemics

The recent H1N1 pandemic that emerged in 2009 has illustrated how swiftly a new influenza virus can circulate the globe. Here we explain the origins of the 2009 pandemic virus, and other twentieth century pandemics. We also consider the impact of the 2009 pandemic in the human population and the use of vaccines and antiviral drugs. Thankfully this outbreak was much less severe than that associated with Spanish flu in 1918. We describe the viral factors that affect virulence of influenza and speculate on the future course of this virus in humans and animals.

The impact of sex, gender and pregnancy on 2009 H1N1 disease

Children and young adults of reproductive age have emerged as groups that are highly vulnerable to the current 2009 H1N1 pandemic. The sex of an individual is a fundamental factor that can influence exposure, susceptibility and immune responses to influenza. Worldwide, the incidence, disease burden, morbidity and mortality rates following exposure to the 2009 H1N1 influenza virus differ between males and females and are often age-dependent. Pregnancy and differences in the presentation of various risk factors contribute to the worse outcome of infection in women. Vaccination and antiviral treatment efficacy also vary in a sex-dependent manner. Finally, sex-specific genetic and hormonal differences may contribute to the severity of influenza and the clearance of viral infection. The contribution of sex and gender to influenza can only be determined by a greater consideration of these factors in clinical and epidemiological studies and increased research into the biological basis underlying these differences.

Correlates of seasonal influenza vaccine coverage among pregnant women in Georgia and Rhode Island

OBJECTIVE

To identify facilitators of and barriers to pregnant women being vaccinated against seasonal influenza by identifying factors associated with influenza vaccination during pregnancy among women who had recently given birth to a live infant.

METHODS

We analyzed pooled data from Georgia (n=2,692) and Rhode Island (n=2,732) participants in the 2006 and 2007 surveys of the Pregnancy Risk Assessment and Monitoring System, which conducts cross-sectional surveys of women with live births. SUDAAN software was used for analysis to account for complex survey design. We estimated rates of seasonal influenza vaccination among pregnant women in Georgia and Rhode Island and identified factors associated with being vaccinated.

RESULTS

The prevalence of immunization for seasonal influenza in 2006 and 2007 combined was 18.4% (95% confidence interval [CI]: 15.9-21.1) in Georgia and 31.9% (95% CI 29.8-34.0) in Rhode Island. Multivariable analyses showed that in Georgia, multiparous women were significantly less likely to have been vaccinated than primiparous women (adjusted odds ratio [OR] 0.60; 95% CI 0.40-0.89). In Georgia, among those not vaccinated, 43% indicated that their health care providers did not mention anything about the seasonal influenza vaccination. In Rhode Island, women whose health care provider encouraged them to be vaccinated (adjusted OR 56.62; 95% CI 37.43-85.63) and those who did not smoke cigarettes (adjusted OR 1.92; 95% CI 1.25-2.94) were significantly more likely to be vaccinated.

CONCLUSION

Our findings indicate a need for strategies to promote seasonal influenza vaccine use among pregnant women. Health care providers can play a significant role in increasing influenza vaccination coverage rates among pregnant women by advising women to be vaccinated and by addressing their concerns about vaccine safety.

LEVEL OF EVIDENCE

III.

French experience of 2009 A/H1N1v influenza in pregnant women

BACKGROUND

The first reports on the pandemic influenza 2009 A/H1N1v from the USA, Mexico, and Australia indicated that this disease was associated with a high mortality in pregnant women. The aim of this study was to describe and compare the characteristics of severe critically ill and non-severe pregnant women with 2009 A/H1N1v-related illness in France.

METHODOLOGY/PRINCIPAL FINDINGS

A national registry was created to screen pregnant women with laboratory-confirmed 2009 A/H1N1v influenza. Three hundred and fifteen patients from 46 French hospitals were included: 40 patients were admitted to intensive care units (severe outcomes), 111 were hospitalized in obstetric or medical wards (moderate outcomes), and 164 were outpatients (mild outcomes). The 2009 A/H1N1v influenza illness occurred during all pregnancy trimesters, but most women (54%), notably the severe patients (70%), were in the third trimester. Among the severe patients, twenty (50%) underwent mechanical ventilation, and eleven (28%) were treated with extracorporeal membrane oxygenation. Three women died from A/H1N1v influenza. We found a strong association between the development of a severe outcome and both co-existing illnesses (adjusted odds ratio [OR], 5.1; 95% confidence interval [CI], 2.2-11.8) and a delay in oseltamivir treatment after the onset of symptoms (>3 or 5 days) (adjusted OR, 4.8; 95% CI, 1.9-12.1 and 61.2, 95% CI; 14.4-261.3, respectively). Among the 140 deliveries after 22 weeks of gestation known to date, 19 neonates (14%) were admitted to a neonatal intensive care unit, mainly for preterm delivery, and two neonates died. None of these neonates developed 2009 A/H1N1v infection.

CONCLUSIONS

This series confirms the high incidence of complications in pregnant women infected with pandemic A/H1N1v observed in other countries but depicts a lower overall maternal and neonatal mortality and morbidity than indicated in the USA or Australia. Moreover, our data demonstrate the benefit of early oseltamivir treatment in this specific population.

Testing the Fetal Origins Hypothesis in a developing country: evidence from the 1918 Influenza Pandemic

The 1918 Influenza Pandemic is used as a natural experiment to test the Fetal Origins Hypothesis. This hypothesis states that individual health as well as socioeconomic outcomes, such as educational attainment, employment status, and wages, are affected by the health of that individual while in utero. Repeated cross sections from the Pesquisa Mensal de Emprego (PME), a labor market survey from Brazil, are used to test this hypothesis. I find evidence to support the Fetal Origins Hypothesis. In particular, compared to individuals born in the few years surrounding the Influenza Pandemic, those who were in utero during the pandemic are less likely to be college educated, be employed, have formal employment, or know how to read and have fewer years of schooling and a lower hourly wage. These results underscore the importance of fetal health especially in developing countries.

Viral ssRNA induces first trimester trophoblast apoptosis through an inflammatory mechanism

PROBLEM

Infection during pregnancy represents a significant cause of mobility and mortality. While viruses pose a major threat, little is known about their effect on early pregnancy, or the mechanisms involved. The objective of this study was to characterize the trophoblast response following exposure to viral ssRNA.

METHOD OF STUDY

First trimester trophoblast cells were treated with or without viral ssRNA. Cytokine production was measured using multiplex analysis and ELISA. Apoptosis was determined using Hoechst staining, cell viability, and caspase activity assays.

RESULTS

Treatment of trophoblasts with viral ssRNA increased their secretion of IL-8, IL-6, and IFNbeta. However, the ssRNA also induced trophoblast apoptosis. To test whether the viral ssRNA-induced inflammatory response was responsible for this induction of apoptosis, conditioned media (CM) from trophoblasts were added to a fresh culture of cells. The CM from viral ssRNA-treated induced higher levels of trophoblast apoptosis than the control CM. Moreover, recombinant IFNbeta induced trophoblast apoptosis.

CONCLUSION

We demonstrate that viral ssRNA induces a pro-inflammatory and type I interferon response in the trophoblast and this inflammatory process may indirectly induce trophoblast apoptosis. These results provide a novel mechanism by which certain viral infections might compromise placental integrity and function, and therefore, pregnancy outcome.

[Pregnancy and pandemic influenza A(H1N1) 2009. Current concepts for anaesthesia and critical care medicine]

Pregnant women are particularly vulnerable to the pandemic influenza A(H1N1) 2009. Indeed, they are at high risk of developing a severe or fatal form of the disease. The physiological changes and the "immune deviation" from cellular to humoral immunity occurring during pregnancy are hypotheses to explain this vulnerability. Severe forms, mainly viral pneumonias, require an urgent prescription of an effective antiviral therapy. Preventive measures, mainly vaccination, are essential to avoid the appearance of these severe forms.

[Influenza A/H1N1v 2009 during pregnancy and breastfeeding: which antiviral to choose?]

SUMMARY

Pregnant women are at increased risk of severe complications associated with H1N1 pandemic influenza. Fever and inflammatory syndrome associated with the infection may also be deleterious for the developing fetus. Therefore, early antiviral treatment is recommended. Oseltamivir and zanamivir are the two therapeutic options available indicated in the treatment of H1N1 influenza; however, limited data is published on their use during pregnancy and lactation. In this review, we will focus on the effects of H1N1 during pregnancy and on data safety of antivirals during pregnancy and lactation. Main health authorities recommendations for H1N1 influenza treatment of pregnant women will also be presented.

Low clinical burden of 2009 pandemic influenza A (H1N1) infection during pregnancy on the island of La Réunion

Background

Pregnant women have been identified as a group at risk, both for respiratory complications than for the admissions to the Intensive Care Unit (ICU) during the 2009 H1N1 influenza pandemic (pdm). The purpose of this prospective register-based cohort-study was to characterize the clinical virulence of the pdm (H1N1/09)v during pregnancy in La Réunion.

Methods/Principal Findings

Over a twelve-week pdm wave (13 July to 3 October 2009), 294 pregnant women presented with an influenza-like illness (ILI) to one of the three maternity departments of the South Reunion area, Indian Ocean. Out of these, 278 were checked by RT-PCR for influenza viruses (157 positive and 121 negative, of whom, 141 with pdm flu and 132 with ILIs of non pdm origin, 5 untyped). The median body temperature was higher in women experiencing pdm flu than in those with non pdm ILI (38.9°C versus 38.3°C, P<0.0001), without evidence linked to circulating viremia. Oseltamivir was given for 86% of pdm flu cases in a median time inferior than 48 hrs (range 0–7 days). The hospitalization rate for pdm flu was of 60% and not associated with underlying conditions. Six viral pneumonia and fourteen asthma attacks were observed among 84 hospitalized pdm flu cases, of whom, only one led to the ICU for an acute lung injury. No maternal death occurred during the pdm wave. None adverse pregnancy outcome was associated with pdm flu. No congenital birth defect, nor early-onset neonatal influenza infection was attributable to pdm flu exposure.

Conclusions/Significance

This report mitigates substantially the presumed severity of pandemic H1N1/09 influenza infection during pregnancy. The reasons for which the clinical burden of H1N1/09 influenza virus may differ worldwide raise questions about a differential local viral-strain effect and public health preparedness, notably in timely access to special care and antiviral treatments.

Deaths from seasonal influenza among pregnant women in the United States, 1998-2005

OBJECTIVE

To estimate pregnancy-related mortality caused by seasonal influenza in the United States for comparison with the current 2009 influenza A H1N1 pandemic.

METHODS

Pregnancy-related deaths were identified in the U.S. Centers for Disease Control and Prevention's (CDC) Pregnancy Mortality Surveillance System (PMSS) database for the years 1998-2005. PMSS collects de-identified copies of vital records supplied by all 50 states, the District of Columbia, and New York City for women who died during or within 1 year after pregnancy. Records in the database broadly classified under deaths due to respiratory infections were identified, and the corresponding archived death certificates were individually reviewed to classify the cause of death as pneumonia or influenza.

RESULTS

Between 1998 and 2005, 4,693 pregnancy-related deaths were reported to CDC. Of these, 78 women died from influenza or pneumonia; 40 of these deaths occurred during an influenza season. Nearly 75% of deaths occurred during or within 2 weeks of the end of the pregnancy.

CONCLUSION

On average, five possible influenza-related deaths among pregnant women were reported per year before the emergence of pregnancy-related deaths due to the current H1N1 pandemic compared with the 28 laboratory-confirmed, pregnancy-related deaths reported for the first 4 months of the 2009 pandemic. This highlights the excess mortality among pregnant women resulting from this pandemic influenza virus.

Anti-tumor necrosis factor therapy and influenza: keeping it in perspective

The association of opportunistic infections in the context of anti-tumor necrosis factor (TNF) antibody therapies have attracted widespread attention. The recent H1N1 influenza pandemic brought this into sharp focus with numerous patient queries and physician anxieties. The following short review gives a scientific perspective to this issue including the role of vaccination.

A perspective on CDC's efforts in safe motherhood: 2001 to the present

This article reviews selected activities to promote Safe Motherhood through scientific and programmatic activities conducted by CDC's Division of Reproductive Health.

Critical illness due to 2009 A/H1N1 influenza in pregnant and postpartum women: population based cohort study

OBJECTIVE

To describe the epidemiology of 2009 A/H1N1 influenza in critically ill pregnant women.

DESIGN

Population based cohort study.

SETTING

All intensive care units in Australia and New Zealand.

PARTICIPANTS

All women with 2009 H1N1 influenza who were pregnant or recently post partum and admitted to an intensive care unit in Australia or New Zealand between 1 June and 31 August 2009.

MAIN OUTCOME MEASURES

Maternal and neonatal mortality and morbidity.

RESULTS

64 pregnant or postpartum women admitted to an intensive care unit had confirmed 2009 H1N1 influenza. Compared with non-pregnant women of childbearing age, pregnant or postpartum women with 2009 H1N1 influenza were at increased risk of admission to an intensive care unit (relative risk 7.4, 95% confidence interval 5.5 to 10.0). This risk was 13-fold greater (13.2, 9.6 to 18.3) for women at 20 or more weeks' gestation. At the time of admission to an intensive care unit, 22 women (34%) were post partum and two had miscarried. 14 women (22%) gave birth during their stay in intensive care and 26 (41%) were discharged from an intensive care unit with ongoing pregnancy. All subsequently delivered. 44 women (69%) were mechanically ventilated. Of these, nine (14%) were treated with extracorporeal membrane oxygenation. Seven women (11%) died. Of 60 births after 20 weeks' gestation, four were stillbirths and three were infant deaths. 22 (39%) of the liveborn babies were preterm and 32 (57%) were admitted to a neonatal intensive care unit. Of 20 babies tested, two were positive for the 2009 H1N1 virus.

CONCLUSIONS

Pregnancy is a risk factor for critical illness related to 2009 H1N1 influenza, which causes maternal and neonatal morbidity and mortality.

Two cases of abnormal liver function associated with H1N1 infection in pregnancy

Two patients with recent H1N1 virus infection in pregnancy were found to have raised transaminases. They have both had a mild illness and have recovered with no adverse effects, and one has delivered a healthy baby while the other is still pregnant. We suggest that the deranged transaminase concentrations were directly linked to the viral infection in the first patient as the abnormal blood results predated treatment. The second case is less clear.

[Pregnancy: a high risk factor in influenza infection]

During pregnancy both mother and foetus are at increased risk of being infected with either pandemic or seasonal influenza viruses, and it is thus legitimate to implement enhanced surveillance for infection particularly with the A/H1N1v and discuss priority vaccine administration. We will review the alterations in immunologic parameters which lead to some degree of cellular immunodeficiency, but also in anatomic changes and pulmonary restrictions which contribute to this suceptibility of pregnant women to severe complications of an influenza infection. We also provide an update on the epidemiological data available for the A/H1N1v infection in this population, and discuss the benefit/risk ratio of treatment with the antiviral medications.

Novel H1N1 virus infection and pregnancy

Human infection with the novel H1N1 influenza virus, initially popularly termed "swine flu," was first reported in April 2009 and has since prompted the World Health Organization (WHO) to raise its pandemic alert to the highest level. During pregnancy both mother and baby are at increased risk when infected with either pandemic or seasonal influenza. Because of concerns about the severity of the disease during pregnancy, the Centers for Disease Control and Prevention (CDC) has implemented enhanced surveillance for infection with this novel virus in pregnant women and has placed them in a group that merits priority vaccine administration. The benefit of treatment with the antiviral medication oseltamivir outweighs its theoretical risk, as pregnant women are at increased risk of severe complications from H1N1 virus infection. In addition to confirmed H1N1 cases, the associated symptoms, particularly fever, merit immediate attention. Moreover, precautions must be taken by both patients and health care professionals when confirmed or suspected H1N1-infected pregnant women present to labor and delivery, or the doctor's office. After delivery, pregnant women infected with H1N1 may breastfeed but must follow specific guidelines. Although the current strain of H1N1 virus has fairly mild sequelae, the virus may have mutated over the summer months and we must anticipate a possible second wave of more severe illness moving into fall 2009 and winter 2010.

Severe 2009 H1N1 influenza in pregnant and postpartum women in California

BACKGROUND

Like previous epidemic and pandemic diseases, 2009 pandemic influenza A (H1N1) may pose an increased risk of severe illness in pregnant women.

METHODS

Statewide surveillance for patients who were hospitalized with or died from 2009 H1N1 influenza was initiated by the California Department of Public Health. We reviewed demographic and clinical data reported from April 23 through August 11, 2009, for all H1N1-infected, reproductive-age women who were hospitalized or died--nonpregnant women, pregnant women, and postpartum women (those who had delivered < or = 2 weeks previously).

RESULTS

Data were reported for 94 pregnant women, 8 postpartum women, and 137 nonpregnant women of reproductive age who were hospitalized with 2009 H1N1 influenza. Rapid antigen tests were falsely negative in 38% of the patients tested (58 of 153). Most pregnant patients (89 of 94 [95%]) were in the second or third trimester, and approximately one third (32 of 93 [34%]) had established risk factors for complications from influenza other than pregnancy. As compared with early antiviral treatment (administered < or = 2 days after symptom onset) in pregnant women, later treatment was associated with admission to an intensive care unit (ICU) or death (relative risk, 4.3). In all, 18 pregnant women and 4 postpartum women (total, 22 of 102 [22%]) required intensive care, and 8 (8%) died. Six deliveries occurred in the ICU, including four emergency cesarean deliveries. The 2009 H1N1 influenza-specific maternal mortality ratio (the number of maternal deaths per 100,000 live births) was 4.3.

CONCLUSIONS

2009 H1N1 influenza can cause severe illness and death in pregnant and postpartum women; regardless of the results of rapid antigen testing, prompt evaluation and antiviral treatment of influenza-like illness should be considered in such women. The high cause-specific maternal mortality rate suggests that 2009 H1N1 influenza may increase the 2009 maternal mortality ratio in the United States.

2009 H1N1 influenza

Within 2 months of its discovery last spring, a novel influenza A (H1N1) virus, currently referred to as 2009 H1N1, caused the first influenza pandemic in decades. The virus has caused disproportionate disease among young people with early reports of virulence similar to that of seasonal influenza. This clinical review provides an update encompassing the virology, epidemiology, clinical manifestations, diagnosis, treatment, and prevention of the 2009 H1N1 virus. Because information about this virus, its prevention, and treatment are rapidly evolving, readers are advised to seek additional information. We performed a literature search of PubMed using the following keywords: H1N1, influenza, vaccine, pregnancy, children, treatment, epidemiology, and review. Studies were selected for inclusion in this review on the basis of their relevance. Recent studies and articles were preferred.

Novel Influenza A (H1N1) Viral Infection in Late Pregnancy: Report of a Case

Health care workers, including anesthesia providers, are often exposed to different infectious disease processes. In the operating room, anesthesia providers, nurses, and surgical staff use universal precautions as a standard of practice. The novel influenza A (H1N1) epidemic has heightened concerns because diagnosis is often delayed and transmission can affect those in a close radius to the infected host. The objectives of this report are to describe the intensive care management and outcomes of severe H1N1 viral infection in a patient in the last trimester of pregnancy and to review the epidemiology, management, and outcomes of similar US cases.

Antiviral medications for pregnant women for pandemic and seasonal influenza: an economic computer model

OBJECTIVE

To estimate the economic value of administering antiviral medications to pregnant women who have come in contact with an infectious individual with influenza.

METHODS

A computer-simulation model was developed to predict the potential economic effect of antiviral use for postexposure prophylaxis among pregnant women in both seasonal influenza and pandemic influenza scenarios. The model allowed us to examine the effects of varying influenza exposure risk, antiviral efficacy, antiviral cost, and the probability of different influenza outcomes such as hospitalization, preterm delivery, and mortality.

RESULTS

For a variety of pandemic influenza scenarios (attack rate 20% or more, probability of preterm birth for women with influenza 12% or more, mortality for a preterm neonate 2% or more, and probability of influenza-attributable hospitalization 4.8% or more), the postexposure prophylactic use of antiviral medications was strongly cost-effective, with incremental cost-effectiveness ratio values below $50,000 per quality-adjusted life-year. Antiviral prophylaxis became an economically dominant strategy (that is, less costly and more effective) when the influenza attack rate is 20% or more and preterm birth rate is 36% or more, and when attack rate is 30% or more and preterm birth rate is 24% or more. Antiviral prophylaxis was not cost-effective under seasonal influenza conditions.

CONCLUSION

These findings support the use of antiviral medications for postexposure prophylaxis among pregnant women in a pandemic influenza scenario but not in a seasonal influenza setting.

Effective health risk communication about pandemic influenza for vulnerable populations

The consequences of pandemic influenza for vulnerable populations will depend partly on the effectiveness of health risk communications. Strategic planning should fully consider how life circumstances, cultural values, and perspectives on risk influence behavior during a pandemic. We summarize recent scientific evidence on communication challenges and examine how sociocultural, economic, psychological, and health factors can jeopardize or facilitate public health interventions that require a cooperative public. If ignored, current communication gaps for vulnerable populations could result in unequal protection across society during an influenza pandemic. We offer insights on communication preparedness gleaned from scientific studies and the deliberations of public health experts at a meeting convened by the Centers for Disease Control and Prevention, May 1 and 2, 2008.

Pandemic influenza and pregnant women: summary of a meeting of experts

Pandemic Influenza: Special Considerations for Pregnant Women was a meeting convened by the Centers for Disease Control and Prevention in 2008 to obtain input from experts and key partners regarding clinical management of pregnant women and related public health actions to be taken during a pandemic. Meeting goals were to discuss issues specific to pregnant women, identify gaps in knowledge, and develop a public health approach for pregnant women in the event of a pandemic. The meeting focused on 4 main topics: prophylaxis and treatment with influenza antiviral and other medications, vaccine use, nonpharmaceutical interventions and health care planning, and communications. Participants reviewed the available evidence to guide action in each of these areas and identified areas of critical needs for future research.

H3N2 influenza A virus replicates in immortalized human first trimester trophoblast cell lines and induces their rapid apoptosis

PROBLEM

Epidemiological data suggested that pandemic influenza increased the risks of spontaneous abortion and premature labor, while seasonal influenza also increased the risk of schizophrenia in adolescence. However, their pathogenesis is so far unknown.

METHOD OF STUDY

The first trimester trophoblast cell lines, namely, Swan71 and HTR8 cells were challenged with A/Udorn/72 influenza virus (H3N2). At indicated time points, cells were examined for expression of influenza proteins. Viral replication in culture media, apoptosis and the expression of human leukocyte antigen (HLA)-G were also examined.

RESULTS

Intracellular localization of viral proteins was observed. Twenty-four hours after inoculation, virus was detected in culture media while most cells fell into apoptosis. During apoptosis, expression of HLA-G was unchanged.

CONCLUSION

We revealed replication of low pathogenic influenza virus in the first trimester trophoblast cell lines. Placental damages are likely to be induced by direct cytopathic effects of influenza virus and subsequent apoptosis rather than down regulation of HLA-G expression and subsequent rejection by maternal immune system.

H1N1 2009 influenza virus infection during pregnancy in the USA

BACKGROUND

Pandemic H1N1 2009 influenza virus has been identified as the cause of a widespread outbreak of febrile respiratory infection in the USA and worldwide. We summarised cases of infection with pandemic H1N1 virus in pregnant women identified in the USA during the first month of the present outbreak, and deaths associated with this virus during the first 2 months of the outbreak.

METHODS

After initial reports of infection in pregnant women, the US Centers for Disease Control and Prevention (CDC) began systematically collecting additional information about cases and deaths in pregnant women in the USA with pandemic H1N1 virus infection as part of enhanced surveillance. A confirmed case was defined as an acute respiratory illness with laboratory-confirmed pandemic H1N1 virus infection by real-time reverse-transcriptase PCR or viral culture; a probable case was defined as a person with an acute febrile respiratory illness who was positive for influenza A, but negative for H1 and H3. We used population estimates derived from the 2007 census data to calculate rates of admission to hospital and illness.

FINDINGS

From April 15 to May 18, 2009, 34 confirmed or probable cases of pandemic H1N1 in pregnant women were reported to CDC from 13 states. 11 (32%) women were admitted to hospital. The estimated rate of admission for pandemic H1N1 influenza virus infection in pregnant women during the first month of the outbreak was higher than it was in the general population (0.32 per 100 000 pregnant women, 95% CI 0.13-0.52 vs 0.076 per 100 000 population at risk, 95% CI 0.07-0.09). Between April 15 and June 16, 2009, six deaths in pregnant women were reported to the CDC; all were in women who had developed pneumonia and subsequent acute respiratory distress syndrome requiring mechanical ventilation.

INTERPRETATION

Pregnant women might be at increased risk for complications from pandemic H1N1 virus infection. These data lend support to the present recommendation to promptly treat pregnant women with H1N1 influenza virus infection with anti-influenza drugs.

FUNDING

US CDC.

Estrogen inhibits dendritic cell maturation to RNA viruses

Dendritic cells (DCs) play a central role in initiating and polarizing the immune response. Therefore, DC maturation represents a key control point in the shift from innate to adaptive immunity. It is suspected that during pregnancy, hormones are critical factors that modulate changes reported to occur in maternal immunity. Here we examined the effect of 17-beta-estradiol (E2) on the maturational response triggered by virus in human DCs and its influence on their ability to activate naive T cells. We developed an in vitro system to measure the response of DCs to virus infection with Newcastle disease virus (NDV) after a 24-hour E2 treatment. Using this system, we demonstrated that E2 pretreatment down-regulated the antiviral response to RNA viruses in DCs by profoundly suppressing type I interferon (IFN) synthesis and other important inflammatory products. In addition, the DCs capacity to stimulate naive CD4 T cells was also reduced. These results suggest an important role for E2 in suppressing the antiviral response and provide a mechanism for the reduced immunity to virus infection observed during pregnancy.