Infective respiratory syncytial virus is present in human cord blood samples and most prevalent during winter months

Prenatal Infection by Respiratory Viruses Is Associated with Immunoinflammatory Responses in the Fetus

Rationale: Respiratory viral infections can be transmitted from pregnant women to their offspring, but frequency, mechanisms, and postnatal outcomes remain unclear. Objectives: The aims of this prospective cohort study were to compare the frequencies of transplacental transmission of respiratory syncytial virus (RSV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), analyze the concentrations of inflammatory mediators in maternal and fetal blood, and assess clinical consequences. Methods: We recruited pregnant women who developed upper respiratory infections or tested positive for SARS-CoV-2. Maternal and cord blood samples were collected at delivery. Study questionnaires and electronic medical records were used to document demographic and medical information. Measurements and Main Results: From October 2020 to June 2022, droplet digital PCR was used to test blood mononuclear cells from 103 mother-baby dyads. Twice more newborns in our sample were vertically infected with RSV compared with SARS-CoV-2 (25.2% [26 of 103] vs. 11.9% [12 of 101]; P = 0.019). Multiplex ELISA measured significantly increased concentrations of several inflammatory cytokines and chemokines in maternal and cord blood from newborns, with evidence of viral exposure in utero compared with control dyads. Prenatal infection was associated with significantly lower birth weight and postnatal weight growth. Conclusions: Data suggest a higher frequency of vertical transmission for RSV than SARS-CoV-2. Intrauterine exposure is associated with fetal inflammation driven by soluble inflammatory mediators, with expression profiles dependent on the virus type and affecting the rate of viral transmission. Virus-induced inflammation may have pathological consequences already in the first days of life, as shown by its effects on birth weight and postnatal weight growth.

Prenatal exposure to RSV season influences first-year risk of RSV lower respiratory illness and RSV-specific immune responses assessed at birth

Maternal-to-fetal transmission of respiratory syncytial virus (RSV) has been shown to occur but whether late prenatal exposure to RSV season influences offspring postnatal RSV-lower respiratory illness (LRI) risk in early life or RSV immune status at birth is unclear. In this study, the duration of third trimester RSV season exposure was determined for 1,094 newborns of the Tucson Children's Respiratory Study (TCRS) and found to show an inverse relation to risk for first RSV-LRI in the first year. Cord blood anti-RSV antibody is related to third trimester RSV season exposure but not to first year RSV-LRI risk. In a separate birth cohort (the Infant Immune Study), supernatants from cord blood mononuclear cells stimulated with the recall antigen, UV-inactivated RSV, were assayed for IFN-γ and IL-4. The frequency of detectable IFN-γ (but not IL-4) was increased for those with at least 2 mo of third trimester RSV season exposure, suggestive of a fetal immune response to RSV. IMPORTANCE Our study found that duration of third trimester exposure to RSV season related inversely to subsequent risk of postnatal RSV-LRI in the first year, thus implicating this exposure as an important factor in reducing risk of postnatal RSV-LRIs, a risk reduction that appears to be independent of maternally transferred anti-RSV antibody level. The increase in frequency of detectable IFN-γ and not IL-4 in response to UV-inactivated RSV in cord blood immune cells for infants with greater third trimester exposure to RSV season is suggestive of a Type-1 immune response to RSV occurring in utero.

Effects of Vertical Transmission of Respiratory Viruses to the Offspring

Overt and subclinical maternal infections in pregnancy can have multiple and significant pathological consequences for the developing fetus, leading to acute perinatal complications and/or chronic disease throughout postnatal life. In this context, the current concept of pregnancy as a state of systemic immunosuppression seems oversimplified and outdated. Undoubtedly, in pregnancy the maternal immune system undergoes complex changes to establish and maintain tolerance to the fetus while still protecting from pathogens. In addition to downregulated maternal immunity, hormonal changes, and mechanical adaptation (e.g., restricted lung expansion) make the pregnant woman more susceptible to respiratory pathogens, such as influenza virus, respiratory syncytial virus (RSV), and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Depending on the infectious agent and timing of the infection during gestation, fetal pathology can range from mild to severe, and even fatal. Influenza is associated with a higher risk of morbidity and mortality in pregnant women than in the general population, and, especially during the third trimester of pregnancy, mothers are at increased risk of hospitalization for acute cardiopulmonary illness, while their babies show higher risk of complications such as prematurity, respiratory and neurological illness, congenital anomalies, and admission to neonatal intensive care. RSV exposure in utero is associated with selective immune deficit, remodeling of cholinergic innervation in the developing respiratory tract, and abnormal airway smooth muscle contractility, which may predispose to postnatal airway inflammation and hyperreactivity, as well as development of chronic airway dysfunction in childhood. Although there is still limited evidence supporting the occurrence of vertical transmission of SARS-CoV-2, the high prevalence of prematurity among pregnant women infected by SARS-CoV-2 suggests this virus may alter immune responses at the maternal-fetal interface, affecting both the mother and her fetus. This review aims at summarizing the current evidence about the short- and long-term consequences of intrauterine exposure to influenza, RSV, and SARS-CoV-2 in terms of neonatal and pediatric outcomes.

RSV-induced changes in a 3-dimensional organoid model of human fetal lungs

We have shown that respiratory syncytial virus (RSV) can spread hematogenously from infected airways of a pregnant woman to the developing fetal lungs in utero. This study sought to measure RSV replication, cytopathic effects, and protein expression in human lung organoids (HLOs) reproducing architecture and transcriptional profiles of human fetal lungs during the 1st trimester of gestation. HLOs derived from human pluripotent stem cells were microinjected after 50 or 100 days in culture with medium or recombinant RSV-A2 expressing the red fluorescent protein gene (rrRSV). Infection was monitored by fluorescent microscopy and PCR. Immunohistochemistry and proteomic analysis were performed. RSV infected HLOs in a dose- and time-dependent manner. RSV-infected HLOs increased expression of CC10 (Club cells), but had sparse FOXJ1 (ciliated cells). Disruption of F-actin cytoskeleton was consistent with proteomic data showing a significant increase in Rho GTPases proteins. RSV upregulated the transient receptor potential vanilloid 1 (TRPV1) channel and, while β2 adrenergic receptor (β2AR) expression was decreased overall, its phosphorylated form increased. Our data suggest that prenatal RSV infection produces profound changes in fetal lungs' architecture and expression profiles and maybe an essential precursor of chronic airway dysfunction. expression profiles, and possibly be an important precursor of chronic airway dysfunction.

Digital PCR for accurate quantification of pathogens: Principles, applications, challenges and future prospects

Pathogens pose a severe threat to food safety and human health. The traditional methods for pathogen detection can't meet the growing diagnosis and control need. Digital PCR (dPCR) attracts a considerable attention for its ability to absolutely quantify pathogens with features of high selectivity, simplicity, accuracy and rapidity. The dPCR technique that achieves absolute quantification based on end-point measurement without standard curve offers a guideline for further genetic analysis and molecular diagnosis. It could contribute to the quantification of low level of nucleic acid, early detection and timely prevention of pathogenic diseases. In this review, 1442 publications about dPCR were selected and the detections of various pathogens by dPCR were reviewed comprehensively, including viruses, bacteria, parasites and fungi. A number of examples are cited to illustrate that dPCR is a new powerful tool with desired accuracy, sensitivity, and reproducibility for quantification of different types of pathogens. Moreover, the benefits, challenges and future prospects of the dPCR were also highlighted in this review.

Respiratory viral infections during pregnancy: effects of SARS-CoV-2 and other related viruses over the offspring

Little is known about the consequences of viral infection for pregnant woman or for the fetus. This issue became important with the appearance of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). The infection with SARS-CoV-2 causes a respiratory syndrome known as COVID-19. The fast spreading around the world and the fact that without a treatment or vaccine humans are completely exposed, converts emerging viral diseases in a significant risk for pregnant women and their infants. At this time, during SARS-CoV-2 pandemics pregnant women are not considered as a risk population and little is known about the effects of viral infections over the offspring although the amount of emerging evidence showing detrimental effects for the mother and the fetus. This issue highlights the importance to understand the effects of viral infections during pregnancy. In this work, we analyze the effects of viral infections, like SARS-CoV-2 and other related viruses during pregnancy over the mother and the consequences for the offspring.

Respiratory syncytial virus seropositivity at birth is associated with adverse neonatal respiratory outcomes

BACKGROUND

More than 60 years since the discovery of the respiratory syncytial virus (RSV), the effects of prenatal exposure to this virus remain largely unknown. In this investigation, we sought to find evidence of RSV seroconversion in cord blood and explore its clinical implications for the newborn.

METHODS

Offspring from 22 pregnant women with a history of viral respiratory infection during the third trimester of pregnancy (respiratory viral illness [RVI] group) and 40 controls were enrolled in this study between 1 September 2016 and 31 March 2019. Cord blood sera were tested for anti-RSV antibodies by indirect fluorescent antibody assay. RSV seropositivity was defined as the presence of anti-RSV immunoglobulin M (IgM) or immunoglobulin A (IgA), in addition to IgG in cord blood serum at ≥1:20 dilution.

RESULTS

Anti-RSV IgG was present in all cord blood serum samples from infants born to RVI mothers (95% confidence interval [CI] = 82%-100%), with 16 samples also having elevated titers for either anti-RSV IgA or IgM (73%; 95% CI = 52%-87%). No controls had evidence of anti-RSV antibodies. Eight (50%) seropositive newborns developed at least one respiratory tract finding, including respiratory distress syndrome (N = 8), respiratory failure (N = 3), and pneumonia (N = 1). RSV seropositive newborns also required more days on oxygen, had leukocytosis and elevated C-reactive protein (P = .025, P = .047, and P < .001, respectively).

CONCLUSION

This study provides evidence of acute seropositivity against RSV in cord blood of newborns delivered from mothers with a history of upper respiratory tract illness in the third trimester. Cord blood seropositivity for anti-RSV IgA or IgM was associated with adverse clinical and laboratory outcomes in newborns.

INFECTIONS IN PREGNANCY WITH COVID-19 AND OTHER RESPIRATORY RNA VIRUS DISEASES ARE RARELY, IF EVER, TRANSMITTED TO THE FETUS: EXPERIENCES WITH CORONAVIRUSES, HPIV, hMPV RSV, AND INFLUENZA

SARS-CoV-2, the agent of COVID-19, is similar to two other coronaviruses, SARS-CoV and MERS-CoV, in causing life-threatening maternal respiratory infections and systemic complications. Because of global concern for potential intrauterine transmission of SARS-CoV-2 from pregnant women to their infants, this report analyzes the effects on pregnancy of infections caused by SARS-CoV-2 and other respiratory RNA viruses, and examines the frequency of maternal-fetal transmission with SARS-CoV-2, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), influenza, respiratory syncytial virus (RSV), parainfluenza (HPIV) and metapneumovirus (hMPV). There have been no confirmed cases of intrauterine transmission reported with COVID-19 or any other coronavirus infections. Influenza virus, despite causing approximately one billion annual infections globally, has only a few cases of confirmed or suspected intrauterine fetal infections reported. RSV is in an unusual cause of illness among pregnant women, and with the exception of one premature infant with congenital pneumonia, no other cases of maternal-fetal infection are described. Parainfluenza virus and human metapneumovirus can produce symptomatic maternal infections but do not cause intrauterine fetal infection. In summary, it appears that the absence thus far of maternal-fetal transmission of the SARS-CoV-2 virus during the COVID-19 pandemic is similar to other coronaviruses, and is also consistent with the extreme rarity of suggested or confirmed cases of intrauterine transmission of other respiratory RNA viruses. This observation has important consequences for pregnant women as it appears that if intrauterine transmission of SARSCoV-2 does eventually occur, it will be a rare event. Potential mechanisms of fetal protection from maternal viral infections are also discussed.

Evaluation of Droplet Digital Polymerase Chain Reaction (ddPCR) for the Absolute Quantification of Aspergillus species in the Human Airway

BACKGROUND

Prior studies illustrate the presence and clinical importance of detecting Aspergillus species in the airways of patients with chronic respiratory disease. Despite this, a low fungal biomass and the presence of PCR inhibitors limits the usefulness of quantitative PCR (qPCR) for accurate absolute quantification of Aspergillus in specimens from the human airway. Droplet digital PCR (ddPCR) however, presents an alternative methodology allowing higher sensitivity and accuracy of such quantification but remains to be evaluated in head-to-head fashion using specimens from the human airway. Here, we implement a standard duplex TaqMan PCR protocol, and assess if ddPCR is superior in quantifying airway Aspergillus when compared to standard qPCR.

METHODS

The molecular approaches of qPCR and ddPCR were applied to DNA fungal extracts in n = 20 sputum specimens obtained from non-diseased (n = 4), chronic obstructive pulmonary disease (COPD; n = 8) and non-cystic fibrosis bronchiectasis (n = 8) patients where Aspergillus status was known. DNA was extracted and qPCR and ddPCR performed on all specimens with appropriate controls and head-to-head comparisons performed.

RESULTS

Standard qPCR and ddPCR were both able to detect, even at low abundance, Aspergillus species (Aspergillus fumigatus - A. fumigatus and Aspergillus terreus - A. terreus) from specimens known to contain the respective fungi. Importantly, however, ddPCR was superior for the detection of A. terreus particularly when present at very low abundance and demonstrates greater resistance to PCR inhibition compared to qPCR.

CONCLUSION

ddPCR has greater sensitivity for A. terreus detection from respiratory specimens, and is more resistant to PCR inhibition, important attributes considering the importance of A. terreus species in chronic respiratory disease states such as bronchiectasis.

Effects of maternal-fetal transmission of viruses and other environmental agents on lung development

New information is emerging concerning the influence of environmental factors (e.g., viruses, pollutants, nutrients) on fetal lung development and the prenatal modulation of cellular and molecular effectors essential to the control of airway function, which may shed new light into the pathogenesis of chronic obstructive pulmonary disease in childhood. In particular, recent studies have shown that nanosize biological and inorganic particles (e.g., respiratory viruses and pollutants) are able to spread hematogenously across the placenta from mother to offspring and interfere with lung development during critical "windows of opportunity". Furthermore, the nutritional balance of maternal diet during pregnancy can affect postnatal lung structure and function. Adverse prenatal environmental conditions can predispose to increased airway reactivity by inducing aberrant cholinergic innervation of the respiratory tract, enhanced contractility of the airway smooth muscle, and impaired innate immunity. Such changes can persist long after birth and might provide a plausible explanation to the development of chronic airway dysfunction in children, even in the absence of atopic predisposition. Insight into maternal-fetal interactions will contribute to a better understanding of the pathogenesis of highly prevalent diseases like bronchiolitis and asthma, and may lead to more precise preventative and therapeutic strategies, or new indications for existing ones.

The Burden of Respiratory Syncytial Virus Infection in Adults and Reproductive-Aged Women

Currently available data on respiratory syncytial virus (RSV) disease burden in adults and reproductive-aged women are limited. These data are critically needed to assist in the advancement of strategies related to maternal RSV vaccination for the passive protection of their newborn children.

Respiratory syncytial virus exhibits differential tropism for distinct human placental cell types with Hofbauer cells acting as a permissive reservoir for infection

BACKGROUND

Respiratory syncytial virus (RSV) is capable of transient viremia and extrapulmonary dissemination. Recently, this virus has been identified in fetal cord blood, suggesting the possibility of in utero acquisition in humans. Here, we assess permissivity and kinetics of RSV replication in primary human placental cells, examine their potential to transfer this infection to neighboring cells, and measure the inflammatory response evoked by the virus.

METHODS AND FINDINGS

Human placental villus tissue was collected immediately upon delivery and processed for isolation of placental cytotrophoblast, fibroblast, and macrophage (Hofbauer) cells. Isolated cells were infected with a recombinant RSV-A2 strain (rrRSV) expressing red fluorescent protein (RFP) and analyzed by fluorescence microscopy, Western blot, and quantitative PCR (qPCR). Based on RFP expression, rrRSV exhibited differential tropism for the three major placental cell types. Placental fibroblasts and Hofbauer cells were permissive and supported productive rrRSV replication. While infected cytotrophoblast cells expressed viral glycoprotein (G protein), only limited RSV replication was detected. Importantly, qPCR and fluorescence-focused unit assay revealed that the viral progeny remains trapped within infected Hofbauer cells for up to 30 days, with no release into surrounding media. Yet, Hofbauer cells passed the infection onto overlaid naïve 16HBE cells, suggesting contact-dependent trans-infection. Lastly, a significant increase in proinflammatory cytokines, particularly IL-6, TNF-alpha, and IFN-gamma was measured in the supernatant of infected Hofbauer cells by multiplex cytokine assay and conventional ELISA.

CONCLUSIONS

This study demonstrates that RSV can replicate in human placenta, exhibits differential tropism for distinct placental cell types, can be stored and transferred to neighboring cells by Hofbauer cells, and elicits an inflammatory response. It also supports the hypothesis that this respiratory virus can be vertically transferred to the fetus and potentially affect its development and the outcome of pregnancies.

The BeWo cell line derived from a human placental choriocarcinoma is permissive for respiratory syncytial virus infection

The respiratory syncytial virus (RSV) is the main pathogen associated with upper respiratory tract infections during early childhood. Vertical transmission of this virus has been suggested in humans, based on observations recorded during animal studies that revealed an association of RSV with persistent structural and functional changes in the developing lungs of the offspring. However, human placentas have not yet been evaluated for susceptibility to RSV infection. In this study, we examined the capacity of RSV to infect a human trophoblast model, the BeWo cell line. Our results suggest that BeWo cells are susceptible to RSV infection since they allow RNA viral replication, viral protein translation, leading to the production of infectious RSV particles. In this report, we demonstrate that a human placenta model system, consisting of BeWo cells, is permissive to RSV infection. Thus, the BeWo cell line may represent a useful model for studies that aim to characterize the events of a possible RSV infection at the human maternal-fetal interface.