Both IIV and LAIV induced a significant increase of anti-Cal/09 H1N1 IgG, IgA, and HAI titers at 1month after vaccination (GMFC= 3.0, 1.48, and 2.0, respectively, p< 0.001 for all those) (Figures 4A4C,Table S3). (LAIV) vaccinees and declines with age. These data provide insights into vaccine-elicited bNAb induction in children, which have important implications for the design of universal influenza vaccine modalities BOP sodium salt in this crucial population. Rabbit Polyclonal to ARRB1 Keywords:influenza computer virus, vaccines, broadly neutralizing antibodies, children, universal vaccine == Graphical abstract == == Highlights == Repeated inactivated influenza vaccination boosts bNAbs Inactivated and live attenuated vaccines are similarly efficient at boosting bNAbs The magnitude of IIV and LAIV vaccine-elicited bNAb boosting declines with age Yegorov et al. evaluate vaccine-elicited broadly neutralizing antibody (bNAb) responses against group 1 influenza A viruses in children. Repeated seasonal immunization of children against influenza boosts bNAb titers. Inactivated and live attenuated vaccine formulations are similarly effective at boosting bNAbs, with the magnitude of boosting inversely correlated with age. == Introduction == Despite decades of study and the accessibility of seasonal vaccination, influenza remains an important public health concern, largely owing to its ability to escape immunity and cause seasonal epidemics and pandemics.1,2,3Seasonal vaccines, the mainstay of influenza prevention, have often shown modest real-world effectiveness due to suboptimal immunogenicity, alongside rapid and unpredictable changes in circulating virus strains.1,2,3Globally, several different seasonal influenza vaccine formulations are approved, including intramuscular injection of inactivated virus (IIV) or mucosal administration of replication-competent live attenuated influenza vaccine (LAIV).1Although influenza vaccines BOP sodium salt are often considered equally efficacious, there are insufficient data around the impact of repeated vaccination and vaccine type around the breadth of influenza-virus-directed immunity in specific demographic groups, especially children, who are a major source of influenza transmission and, alongside the elderly, are at heightened risk for influenza-related hospitalizations and death.4,5 The bulk of influenza-vaccine-elicited antibodies (Abs) target the viral membrane surface proteins hemagglutinin (HA) and, to a lesser extent, neuraminidase (NA). Of the HA-reactive Abs, most bind the immunodominant globular HA head domain in a strain-specific manner, blocking the conversation between the computer virus and cell surface sialic acid, while a minority of HA-reactive Abs bind the sub-dominant, but highly BOP sodium salt conserved HA stalk domain name; a subset of these Abs is considered broadly neutralizing (bNAbs). HA stalk-reactive bNAbs have emerged as a promising strategy for the development of a universal influenza vaccine.6,7 In adults, we as well as others have shown that bNAbs are selectively boosted by exposure to pandemic/heterosubtypic HA subtypes (via either infection or vaccination).8,9,10bNAb titers also increase over time owing to an accumulation of lifetime exposures to influenza computer virus selecting for cross-reactive B cell clone maintenance and growth.11,12A recent clinical trial demonstrated that chimeric hemagglutinin vaccines delivered in live attenuated and inactivated formulations could successfully boost bNAb titers in adults.6,7However, little is known about how bNAbs develop in children and how vaccination impacts bNAb developmentknowledge that will have important implications for understanding the nature of vaccine-mediated immunity against influenza, especially in the context of exposure to novel strains.1,13,14 Therefore, we explored the effects of seasonal influenza vaccination and vaccine formulation on bNAb induction in participants of a cluster randomized controlled trial (cRCT) designed to compare the community-level protection mediated by IIV and LAIV vaccination of children. We found that titers of neutralizing bNAbs were enhanced by repeated seasonal vaccination and that bNAb levels were boosted similarly by LAIV and IIV. As expected, LAIV and IIV effects on bNAb titers were more pronounced in the mucosa and blood, respectively, and the magnitude of vaccine-induced bNAb responses in the serum declined with age. == Results == == Study participants == The effects of repeated seasonal IIV vaccination around the induction of bNAbs were studied using serum samples from 68 RCT participants (median age 9.0 years) (Table S1), who either received IIV (37 vaccinees) or served as controls (31 controls) for each of the three seasons (2008/09 to 2010/11) captured by the cRCT (Figure 1A andTable 1) and for whom paired samples were available. The effects of vaccine type on bNAb elicitation were subsequently studied using serum and mucosal samples from 72 RCT participants (median age 11.0 years) (Table S1), who received either the inactivated vaccine (IIV, n = 35) or the live attenuated vaccine (LAIV, n = 37) (Figure 1B andTable 1) and for whom paired samples were available. == Physique 1. == Study flowchart (A) BOP sodium salt Description of participants in analysis I: effects of repeated seasonal influenza vaccination on bNAb titers in children. (B) Description of participants in analysis II: effect of vaccine type (IIV versus LAIV) on induction of bNAbs in children. cRCT, cluster randomized controlled trial; bNAb, broadly neutralizing antibody; IIV, inactivated influenza vaccine; LAIV, live attenuated influenza vaccine. == Table.