Differences in antibody responses between trivalent inactivated influenza vaccine and live attenuated influenza vaccine correlate with the kinetics and magnitude of interferon signaling in children

Abstract

Background: Live attenuated influenza vaccine (LAIV) and trivalent inactivated influenza vaccine (TIV) are effective for prevention of influenza virus infection in children, but the mechanisms associated with protection are not well defined.

Methods: We analyzed the differences in B-cell responses and transcriptional profiles in children aged 6 months to 14 years immunized with these 2 vaccines.

Results: LAIV elicited a significant increase in naive, memory, and transitional B cells on day 30 after vaccination, whereas TIV elicited an increased number of plasmablasts on day 7. Antibody titers against the 3 vaccine strains (H1N1, H3N2, and B) were significantly higher in the TIV group and correlated with number of antibody-secreting cells. Both vaccines induced overexpression of interferon (IFN)-signaling genes but with different kinetics. TIV induced expression of IFN genes on day 1 after vaccination in all age groups, and LAIV induced expression of IFN genes on day 7 after vaccination but only in children <5 years old. IFN-related genes overexpressed in both vaccinated groups correlated with H3N2 antibody titers.

Conclusions: These results suggest that LAIV and TIV induced significantly different B-cell responses in vaccinated children. Early induction of IFN appears to be important for development of antibody responses.

Keywords: HI antibodies; Influenza vaccine; LAIV; TIV; children; interferon; neutralizing antibodies.

Figure 1.

A–I, B-cell immune responses after immunization with live attenuated influenza vaccine (LAIV) or trivalent inactivated influenza vaccine (TIV). Whole-blood samples obtained from healthy children were stained for naive B cells (CD19⁺IgD⁺CD27⁻), memory B cells (CD19⁺IgD⁻CD27⁺), transitional B cells (CD19⁺CD24⁺CD38⁺), plasmablasts (CD19⁺CD27⁺CD38⁺), and plasma B cells (CD19⁺CD27⁺CD38⁺CD138) and analyzed by flow cytometry on day 0 (ie, baseline) and days 1, 7, and 30 after vaccination. Data are 16 LAIV vaccinees and 13 TIV vaccinees. The graphs consist of column scatter plots representing absolute numbers of B-cell populations over the different 4 time points. A, Naive B cells in LAIV vaccinees. B, Memory B cells in LAIV vaccinees. C, Transitional B cells in LAIV vaccinees. D, Plasmablasts in LAIV vaccinees. E, Plasma B cells in LAIV vaccinees. F, Naive B cells in TIV vaccinees. G, Memory B cells in TIV vaccinees. H, Transitional B cells in TIV vaccinees. I, Plasmablasts in TIV vaccinees. J, Plasma B cells in TIV vaccinees. Linear mixed model with Bonferroni correction (*P < .05 and **P < .01; NS, no statistical significance). Bars represent median values. K and L, Fold-increase of hemagglutination inhibition (HI) and viral neutralization (VN) titers before and after vaccination in LAIV and TIV recipients. Serum samples obtained on day 0 and 30 days after vaccination from each subject were assayed for HI and VN titers. Data are for 18 LAIV vaccinees and 16 TIV vaccinees. K, Column scatter plot representing fold-increase of HI titers among TIV and LAIV vaccinees for H1N1, H3N2, and B vaccine strains. L, Column scatter plot representing fold-increase of VN titers among TIV and LAIV vaccinees for H1N1, H3N2, and B vaccine strains. *P < .05, by the Mann–Whitney test. Bars represent median values.

Figure 2.

Correlations between hemagglutination inhibition (HI) and viral neutralization (VN) titers and plasmablast and plasma B cells among trivalent inactivated influenza vaccine (TIV) vaccinees. A, Each plot represents the correlation between absolute numbers of plasmablasts and plasma B cells 7 days after vaccination with TIV and fold-increases of H1N1, H3N2, and B HI titers from day 0 (ie, baseline) to day 30 after vaccination. B, Each plot represents the correlation between absolute numbers of plasmablasts and plasma B cells 7 days after vaccination with TIV and fold-increases of H1N1, H3N2, and B VN titers from day 0 to day 30 after vaccination.

Figure 3.

Transcriptional profiles of children immunized with trivalent inactivated influenza vaccine (TIV) and live attenuated influenza vaccine (LAIV) are characterized by activation of interferon (IFN). A, Statistical group comparison (P < .05, by the Mann Whitney test) between the TIV group (n = 14) on day 1 after vaccination versus baseline (ie, day 0) yielded 777 differentially expressed genes. Transcripts were organized by hierarchical clustering, where each row represents a single transcript and each column represents an individual subject. Normalized expression levels are indicated by red (overexpressed) or blue (underexpressed), compared with the median expression at baseline (yellow). B, Modular analysis 1 day after TIV receipt showed significant overexpression of IFN-related modules (M1.2, M3.4, and M5.12). The color intensity of the spots represents the percentage of significantly overexpressed genes (red), the percentage of significantly underexpressed genes (blue), or no differences (blank), compared with healthy controls (P < .05, by the Mann–Whitney test). C and D, Heat maps and modular maps from TIV vaccinees stratified by age. Both groups displayed overexpression of the IFN-related modules, with overexpression more pronounced in the younger group (n = 4). E, Modular map legend. F, Statistical group comparison (P < .05, by the Mann–Whitney test) between the LAIV group (n = 18) on day 7 after vaccination versus day 0 yielded 453 differentially expressed genes. G, Modular analysis 7 days after LAIV receipt. No modules were found to be significantly overexpressed or underexpressed. H and I, Heat maps and modular maps from LAIV vaccinees stratified by age. Only younger children (n = 4) displayed significant overexpression of the IFN-related modules (M1.2, M3.4, and M5.12). Abbreviation: NK, natural killer.

Figure 4.

Interferon (IFN)–related gene expression after vaccination with trivalent inactivated influenza vaccine (TIV) and live attenuated influenza vaccine (LAIV). Significantly expressed genes derived from linear mixed-model analyses (P < .01) are displayed in a heat-map format. A, IFN-related genes were significantly overexpressed and different on day 7 after LAIV receipt, compared with other time points (day 0 [ie, baseline] and days 1 and 30 after vaccination). B, IFN genes were overexpressed and significantly different on day 1 after TIV vaccination, compared with all other time points.