Recombinant quadrivalent influenza vaccine (RIV) induces robust cell-mediated and HA-specific B cell humoral immune responses among healthcare personnel

Abstract

Egg-free influenza vaccines, specifically cell culture-based inactivated influenza vaccine (ccIIV) and recombinant influenza vaccine (RIV), represent a significant advancement over traditional egg-based inactivated influenza vaccines (IIV), particularly for populations with extensive vaccination histories. This comprehensive immunological study investigated the comparative efficacy of ccIIV, IIV, and RIV in healthcare personnel (HCP) with repeated vaccination histories, examining both cellular and humoral immune responses through multiple analytical approaches. Our investigation employed a multi-faceted analytical framework, combining serological assessments via hemagglutination inhibition (HI) and microneutralization (MN) assays with detailed cellular immune response analysis. We utilized advanced flow cytometry techniques with recombinant hemagglutinin (HA) probes to evaluate both circulating T follicular helper cells (cTfh) and HA-specific B cells, providing a comprehensive view of vaccine-induced immune responses. The results revealed RIV's superior immunogenicity profile, demonstrating significantly elevated levels of both cTfh and HA-specific B cells compared to ccIIV and IIV. RIV's enhanced performance was particularly evident in its response to influenza A components, with notably higher immunogenicity against both A(H3N2) and A(H1N1) strains. This superiority was reflected in elevated HI titers and markedly increased HA-specific B cell induction. While RIV also demonstrated enhanced HA-specific B cell responses against influenza B components compared to ccIIV, interestingly, HI titers remained comparable across all vaccine groups for these strains. These findings underscore the critical importance of comprehensive immune response evaluation in vaccine assessment. The disparity between cellular and serological responses, particularly for influenza HA-specific B cells, highlights that traditional serological measures alone may not fully capture the breadth and depth of vaccine-induced immunity. This study provides compelling evidence for the inclusion of cellular immunity assessments in vaccine evaluation protocols, offering crucial insights into vaccine immunogenicity that may be missed by conventional serological analysis alone.

Keywords: Cell culture derived inactivated influenza vaccine (ccIIV); Circulating follicular T helper cells (cTfh); Egg-derived inactivated influenza vaccine (IIV); HA-tags; Healthcare personnel; Influenza; Quadrivalent influenza vaccine (QIV); Recombinant influenza vaccine (RIV); Vaccine.

Fig. 1.. Antibody response to vaccination by hemagglutination inhibition (HI) or microneutralization (MN) assays.

A. Geometric mean titers (GMTs) and 95 % confidence intervals prior to vaccination, at 1 month and 6 months post vaccination by hemagglutination inhibition (HI) and microneutralization (MN) against the cell-grown vaccine reference virus A/Michigan/45/2015, A/Singapore/INFIMH-16–0019/2016, B/Colorado/06/2017(Victoria), B/Phuket/3073/13(Yamagata). Vaccine types included ccIIV (quadrivalent cell culture-based influenza vaccine, 37 subjects), IIV (egg-based quadrivalent inactivated influenza vaccine, 41 subjects), and RIV (quadrivalent recombinant influenza vaccine, 23 subjects). B. The fold rise (FR) in HI GMT and MN GMT means and 95 % confidence intervals at 1 month and 6 months compared to baseline. Statistical analyses were performed using one-way ANOVA with Tukey’s multiple comparison test. Statistically significant differences are indicated as P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001. The limit of detections for HI and MN assays were 1:10.

Fig. 2.. Influenza virus hemagglutinin (HA)-specific B cell response.

A. HA-specific IgG+ B cell FR means, and 95 % confidence intervals measured by flow cytometry with HA probes at days 7, 1 month and 6 months compared to baseline. B. HA stem-specific IgG + B cell FR means, and 95 % confidence intervals measured by flow cytometry with HA stem probes at days 7, 1 month and 6 months compared to baseline. A single IBV HA stem probe was used because of the similarity between the HA stems of Victoria and Yamagata lineages. Statistical analyses were conducted with one-way ANOVA and Tukey’s multiple comparison test. Statistically significant differences are indicated as *P < 0.05, **P < 0.01, ***P < 0.001. Minimum detection limit is set at 5 HA-specific B cells.

Fig. 3.. cTfh response to vaccination.

The fold rise (FR) of circulating T follicular helper cells (cTfh, CXCR5 + PD1+ CD4+) and 95 % confidence intervals at days 7, m1, and m6 compared to pre-vaccination levels are presented. Statistical significance was determined using one-way ANOVA with Tukey’s multiple comparison test, with significant differences indicated as *P < 0.05.

Fig. 4.. Correlation between serological and B cell responses.

A. Correlation between hemagglutination inhibition (HI) or microneutralization (MN) geometric mean titers (GMTs) against the cell-grown vaccine reference viruses [A/Michigan/45/2015, B/Colorado/06/2017(Victoria), B/Phuket/3073/13(Yamagata) were used for HI assay and A/Singapore/INFIMH-16–0019/2016 was used for MN assay] at 1 month post vaccination (m1) and the fold rise in the corresponding strain HA-specific B cell at day 7 compared with baseline (d7/d0). B. Correlation between MN GMTs against the cell-grown vaccine reference virus A/Singapore/INFIMH-16–0019/2016 at 1 month(m1) or 6 months (m6) post vaccination and the induction of the corresponding strain HA-specific B cell at day 7 or day 28 compared with baseline (fold rise d7/d0 or d28/d0). Correlations are for ccIIV, IIV and RIV vaccine groups. Statistical analyses were conducted using simple linear regression. Pearson correlation coefficient, r is indicated for the statistically significant correlations.