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

Abstract

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.

Keywords: coronavirus disease; developmental origins of health and disease; fetal inflammation; maternal immune activation; vertical transmission.

Figure 1.

Overview of blood sample collection and analysis for maternal–baby dyads included in the TTRSV (Transplacental Transmission of RSV) study. Of the 108 dyads with complete blood collections, 5 dyads were excluded from the ddPCR analysis because the samples did not yield enough cells or RNA, and for an additional 2 dyads, the sample volume was sufficient only for RSV but not SARS-CoV-2 amplification. ddPCR = droplet digital PCR; L&D = labor and delivery; RSV = respiratory syncytial virus; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2.

Figure 2.

Maternal–fetal transfer of respiratory syncytial virus (RSV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) copies. (A) RSV copy numbers measured using droplet digital PCR (ddPCR) in peripheral blood mononuclear cell (PBMCs) separated from maternal blood drawn in prenatal clinic or labor and delivery (L/D) versus cord blood. Data from the 103 dyads with complete RSV ddPCR data are shown. Dotted lines represent 15 cord blood samples with virus-positive ddPCR born to virus-negative mothers. (B) SARS-CoV-2 copy numbers measured using ddPCR in PBMCs separated from maternal blood drawn in prenatal clinic or L/D versus cord blood. Data from the 101 dyads with complete SARS-CoV-2 ddPCR data are shown. Dotted lines represent four cord blood samples with virus-positive ddPCR born to virus-negative mothers. (C) RSV or SARS-CoV-2 copy numbers measured using ddPCR in maternal and cord blood from the 11 dyads with at least one sample with dual-positive viral detection. Blue symbols represent samples testing positive for both RSV and SARS-CoV-2.

Figure 3.

Comparison of soluble mediators’ concentrations in maternal blood (MB) from dyads with vertical transmission of virus versus dyads without vertical transmission. (A) Volcano plot showing a comparison of soluble mediators’ concentrations between MB samples from dyads with vertical transmission of virus (i.e., cord blood [CB] positive for any virus [n = 36], respiratory syncytial virus [RSV] [n = 27], or severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] [n = 13]) versus MB samples from dyads without vertical transmission of virus (i.e., only maternal sample positive for any virus [n = 35], RSV [n = 31], and SARS-CoV-2 [n = 18]). For this analysis, we excluded any dyad that had no detectable viremia. Statistical analysis was performed using Mann-Whitney comparison of individual cytokines, with the significance threshold of P < 0.05 indicated by dotted lines. Adjusted comparisons were not significant. (B) Expression of soluble mediators with the highest expression in maternal samples from dyads with (MB^+/−CB⁺) versus without (MB⁺CB⁻) vertical transmission for any virus, by box-and-whisker plots (minimum to maximum) showing all subjects (each comparison was significant at P < 0.05 using Mann-Whitney tests). *P < 0.05, **P < 0.01. (C) Expression of soluble mediators with the highest expression in maternal samples from dyads with (MB^+/−CB⁺) versus without (MB⁺CB⁻) vertical transmission for RSV, by box-and-whisker plots (minimum to maximum) showing all subjects (each comparison was significant at P < 0.05 using Mann-Whitney tests). *P < 0.05, **P < 0.01. (D) Expression of soluble mediators with the highest expression in maternal samples from dyads with (MB^+/−CB⁺) versus without (MB⁺CB⁻) vertical transmission for SARS-CoV-2, by box-and-whisker plots (minimum to maximum) showing all subjects (each comparison was significant at P < 0.05 using Mann-Whitney tests). *P < 0.05, **P < 0.01. CD = cluster of differentiation; diff. = difference; DKK-3 = Dickkopf-related protein 3; SCF-R = stem cell factor receptor; SARS = severe acute respiratory syndrome coronavirus 2; Siglec-5 = sialic acid–binding immunoglobulin-type lectin 5; TNFα = tumor necrosis factor-α; TSLP = thymic stromal lymphopoietin; VEGF = vascular endothelial growth factor.

Figure 4.

Relationship between cord blood inflammatory mediators and birth weight. (A) Overview of feature selection model used to identify viral or cytokine changes that predict neonatal birth weight or change in weight at hospital discharge using the least absolute shrinkage and selection operator and probabilistic latent semantic analysis (PLSA). (B) PLSA for birth weight, including variable importance (VIP) score, model coefficient (for VIP score > 0.8), and predicted versus actual model fit. (C) Feature-selected soluble mediators (CXCL5, MIP-1β, leptin, preadipocyte factor 1) that were individually significant by the line of fit for weight at birth, with R² and P values indicated. CXCL5 = C-X-C motif chemokine ligand 5; MB = maternal blood; MIP-1β = macrophage inflammatory protein; RSV = respiratory syncytial virus; SARS = severe acute respiratory syndrome coronavirus 2.

Figure 5.

Relationship between cord blood inflammatory mediators and viral copy numbers versus weight change from birth to hospital discharge. (A) Results of probabilistic latent semantic analysis for change in weight, including variable importance (VIP) score, model coefficient (for VIP score > 0.8), and predicted versus actual model fit. (B) Feature-selected soluble mediators (VEGF, SCF-R, IL-1 RII, and CRP) that were individually significant by the line of fit for neonatal weight change from birth to hospital discharge, with R² and P values indicated. (C) Correlation between RSV and SARS-CoV-2 cord and maternal blood viral copy numbers versus neonatal weight change from birth to hospital discharge, with the line of fit R² and P values indicated. CB = cord blood; CRP = C-reactive protein; IL-1 RII = IL-1 receptor II; RSV = respiratory syncytial virus; SARS = severe acute respiratory syndrome coronavirus 2; SCF-R = stem cell factor receptor; VEGF = vascular endothelial growth factor.