Biomarkers detected in cord blood predict vaccine responses in young infants

Abstract

Introduction: Factors influencing vaccine immune priming in the first year of life involve both innate and adaptive immunity but there are gaps in understanding how these factors sustain vaccine antibody levels in healthy infants. The hypothesis was that bioprofiles associated with B cell survival best predict sustained vaccine IgG levels at one year.

Methods: Longitudinal study of plasma bioprofiles in 82 term, healthy infants, who received standard recommended immunizations in the United States, with changes in 15 plasma biomarker concentrations and B cell subsets associated with germinal center development monitored at birth, soon after completion of the initial vaccine series at 6 months, and prior to the 12-month vaccinations. Post vaccination antibody IgG levels to Bordetella pertussis, tetanus toxoid, and conjugated Haemophilus influenzae type B (HiB) were outcome measures.

Results: Using a least absolute shrinkage and selection operator (lasso) regression model, cord blood (CB) plasma IL-2, IL-17A, IL-31, and soluble CD14 (sCD14) were positively associated with pertussis IgG levels at 12 months, while CB plasma concentrations of APRIL and IL-33 were negatively associated. In contrast, CB concentrations of sCD14 and APRIL were positively associated with sustained tetanus IgG levels. A separate cross-sectional analysis of 18 mother/newborn pairs indicated that CB biomarkers were not due to transplacental transfer, but rather due to immune activation at the fetal/maternal interface. Elevated percentages of cord blood switched memory B cells were positively associated with 12-month HiB IgG levels. BAFF concentrations at 6 and 12 months were positively associated with pertussis and HiB IgG levels respectively.

Discussion: Sustained B cell immunity is highly influenced by early life immune dynamics beginning prior to birth. The findings provide important insights into how germinal center development shapes vaccine responses in healthy infants and provide a foundation for studies of conditions that impair infant immune development.

Keywords: A proliferation-inducing ligand (APRIL); B cell; human infants; immune development; lymphoid germinal centers; macrophage; tetanus vaccine.

Figure 1

Study design. Longitudinal blood samples, symbolized by blood tubes, were obtained from newborn cord blood, at 7 to 14 days after the 6-month immunization series and at 12 months prior to the immunizations. Blue syringes symbolize the vaccines administered at 2, 4, 6, and 12 months [Diphtheria, tetanus, acellular Pertussis, Haemophilus influenzae type b (HiB), Hepatitis B, Rotavirus, and pneumococcal conjugate], as recommended by the United States AAP/ACIP guidelines. The 6-month blood sample represents the immediate post-vaccine immune response, and the 12-month sample, drawn prior to the 12-month vaccinations, represents sustained “memory”, IgG antibody concentrations to Bordetella pertussis toxin, HiB, and tetanus toxoid at 12 months.

Figure 2

Vaccine IgG levels during the first year of life and relationship to vaccine-specific antibody levels in infants at 12 months. Vaccine IgG levels are shown from cord blood (CB), 6-month, and 12-month samples from each infant for Bordetella pertussis toxin (A, U/ml), Haemophilus influenzae type B (HiB) (B, mg/ml), and tetanus toxoid (C, IU/ml). A one-way ANOVA (Kruskal–Wallis) with Dunn’s post hoc test determined significant differences between CB, 6-month, and 12-month IgG levels. Significance is indicated by ***p ≤ 0.001, and ****p ≤ 0.0001. Gray dots represent CB infant samples. Shape colors represent feeding method during the first 6 months of life. Dark blue triangles designate breast-fed infants, red circles designate mixed-fed infants, and yellow diamonds designate formula-fed infants. Lines represent median values. Abbreviation CB is cord blood, m designates 6- and 12-month blood draws. (D–F) show Spearman correlations between cord blood (reflecting maternal IgG levels) and infant plasma IgG levels at 12 months for Bordetella pertussis toxin (D), HiB (E), and tetanus toxoid (F). Each panel shows the r and p-values from the Spearman test. Solid line shows the best fit with dashed lines representing 95% confidence intervals.

Figure 3

Changes in immune biomarkers and B-cell subsets across the first year of life. Plasma biomarker concentrations are shown in (A–O) with all values in pg/ml. Gray dots represent cord blood (CB) infant samples. Shape colors represent feeding method during the first 6 months of life. Dark blue triangles designate breast-fed infants, red circles designate mixed-fed infants, and yellow diamonds designate formula-fed infants. Lines represent median values. Abbreviation CB is cord blood, m designates 6- and 12-month blood draws. A one-way ANOVA (Kruskal–Wallis) with Dunn’s post-hoc test determined significant changes between CB, 6-month, and 12-month plasma soluble biomarkers or for B-cell subsets. (P, Q) show percentages of total CD19⁺ B cells for CD19⁺CD27⁺IgD^- switched memory B cells (P) and CD19⁺CD24^-CD38^hi plasmablasts (Q), in CB, 6-month, and 12-month blood samples from each infant. Significance is indicated by *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, and ****p ≤ 0.0001. Lines represent median values.

Figure 4

Correlations between mother and infant biomarkers to assess transplacental transfer. (A–F) show selected correlations between cord blood biomarker concentrations in the factors associated with vaccine IgG levels at 12 months ( Table 2 ). Maternal plasma concentrations are on the y axis, and infant CB concentrations are on the x axis for APRIL (A), IL-2 (B), IL-31 (C), IL-17A (D), sCD14 (E), and IL-33 (F). Spearman correlations with respective r and p-values are shown in each panel. Solid lines show the best fit with dashed lines representing 95% confidence intervals. IFN-γ results are not shown since both mothers and infants had >40% of the results below the lower limit of detection (LLOD).

Figure 5

Immune biomarkers associated with sustained post-immunization IgG antibody levels at 12 months in healthy infants. Top figure: The biomarkers and cellular interactions between T follicular helper cells (Tfh), B cells, macrophages, dendritic cells, and endothelial cells within the lymphoid germinal centers are shown to represent the cytokines and soluble factors that influence vaccine responses as measured by vaccine IgG levels. Following vaccine antigen activation, B cells undergo class switch and clonal expansion and develop into post-germinal center plasmablasts and switched and non-switched memory B cells. The lower table lists the soluble and cellular biomarkers associated with vaccine-specific 12 months IgG levels with biomarkers at each blood sample time point associated with vaccine response (birth cord blood, 6 months post-vaccination, and 12 months pre-vaccination). Positive associations with vaccine IgG levels are highlighted in red, and negative associations are in blue. All correlations are based on LASSO analysis results shown in Table 2 . Upper diagram created with BioRender.com.