Functional Immune Cell Differences Associated With Low Vaccine Responses in Infants

Abstract

Background: We sought to understand why some children respond poorly to vaccinations in the first year of life.

Methods: A total of 499 children (6-36 months old) provided serum and peripheral blood mononuclear cell samples after their primary and booster vaccination. Vaccine antigen-specific antibody levels were analyzed with enzyme-linked immunosorbent assay, and frequency of memory B cells, functional T-cell responses, and antigen-presenting cell responses were assessed in peripheral blood mononuclear cell samples with flow cytometric analysis.

Results: Eleven percent of children were low vaccine responders, defined a priori as those with subprotective immunoglobulin G antibody levels to ≥66% of vaccines tested. Low vaccine responders generated fewer memory B cells, had reduced activation by CD4(+) and CD8(+) T cells on polyclonal stimulation, and displayed lower major histocompatibility complex II expression by antigen-presenting cells.

Conclusions: We conclude that subprotective vaccine responses in infants are associated with a distinct immunologic profile.

Keywords: B cells; T cells; antigen presenting cells; infants; vaccines.

Figure 1.

Serum antibody titers against vaccine antigens. A, Immunoglobulin (Ig) G titers from 107 children against 13 vaccine antigens. Low vaccine responders (LVRs) were defined as those with subprotective responses against ≥50% of tested antigens. Six of these vaccine antigens can be used to define LVR equally well. B, IgG titers from 499 children (56 LVRs and 443 normal vaccine responders [NVRs]) against vaccine antigens. LVR children are defined as those with subprotective antibody responses against ≥4 of the 6 tested vaccine antigens (DT, TT, PRP, PT, PRN, and FHA). Each row represents a single child. Green indicates above protection; red, below protection; white, not tested. Abbreviations: DT, diphtheria toxoid; FHA, filamentous hemagglutinin; HepB, hepatitis B; PRN, pertactin; PRP, polyribosylribitol phosphate; PT, pertussis toxoid; Spn, Streptococcus pneumoniae; TT, tetanus toxoid.

Figure 2.

Reduced T-cell function in children who were low vaccine responders (LVRs). A, Diminished CD69 expression by bulk CD4⁺ and CD8⁺ T cells from LVR children in response to polyclonal anti-CD3/CD28 stimulation. B, Diminished CD69 expression by both memory and naive CD4⁺ T-cell subsets from LVR children after polyclonal stimulation. C, Reduced expression of interleukin 1 (IL-2) and tumor necrosis factor (TNF) α by activated CD4⁺ T cells from LVR children. D, Computational SWIFT (scalable weighted iterative flow-clustering technique) analysis reveals reduced TNF-α expression by activated CD4⁺ and CD8⁺ T cells from LVR children. Bars depict medians and interquartile ranges for 10 LVRs and 10 NVRs. Abbreviations: IFN, interferon; NS, not significant; NVRs, normal vaccine responders.

Figure 3.

Total B-cell counts in peripheral blood mononuclear cells from low vaccine responders (LVRs) and normal vaccine responders (NVRs) are comparable, but memory B-cell frequency is significantly lower in LVRs (n = 10; bars represent medians and interquartile ranges).

Figure 4.

Diminished antigen-presenting cell (APC) responses in low vaccine responder (LVRs). A, Baseline major histocompatibility complex II mean fluorescence intensity (MFI) of HLA-DR in peripheral blood unstimulated APC subsets from LVRs (n = 9) and normal vaccine responder (NVRs; n = 17) assessed with flow cytometry. B, Fold change of Toll-like receptor (TLR) signaling pathway genes in response to 24-hour stimulation with 1 µg/mL R848 (n = 14; bars represent medians and interquartile ranges). Abbreviations: cDCs, conventional dendritic cells; IL-10, interleukin 10; IL-12p35, interleukin 12p35; IRF7, interferon regulatory factor 7; MyD88, myeloid differentiation primary response gene 88; NS, not significant; pDCs, plasmacytoid dendritic cells.