The poor performance of 2014–15 Northern Hemisphere (NH) influenza vaccines was attributed to mismatched H3N2 component with circulating epidemic strains. Using human serum samples collected from 2009–10, 2010–11 and 2014–15 NH influenza vaccine trials, we assessed their cross-reactive hemagglutination inhibition (HAI) antibody responses against recent H3 epidemic isolates. All three populations (children, adults, and older adults) vaccinated with the 2014–15 NH egg- or cell-based vaccine, showed >50% reduction in HAI post-vaccination geometric mean titers against epidemic H3 isolates from those against egg-grown H3 vaccine strain A/Texas/50/2012 (TX/12e). The 2014–15 NH vaccines, regardless of production type, failed to further extend HAI cross-reactivity against H3 epidemic strains from previous seasonal vaccines. Head-to-head comparison between ferret and human antisera derived antigenic maps revealed different antigenic patterns among representative egg- and cell-grown H3 viruses characterized. Molecular modeling indicated that the mutations of epidemic H3 strains were mainly located in antibody-binding sites A and B as compared with TX/12e. To improve vaccine strain selection, human serologic testing on vaccination-induced cross-reactivity need be emphasized along with virus antigenic characterization by ferret model.

Our results suggest an age-specific difference in human postvaccination responses. Our findings also suggest that prior exposure to H1 or type B influenza may differentially affect cross-reactivity of vaccination-induced H3-specific hemagglutination inhibition antibody responses, and consequently might affect vaccine effectiveness. Our study highlights the need to study the impact of prior exposure on influenza vaccine performance.

Nontypeable Haemophilus influenzae (NTHi) is associated with chronic otitis media (COM). In this study, we generated a murine model of COM by using eustachian tube (ET) obstruction and NTHi (10 7 CFU) inoculation into the tympanic bulla, and we investigated the relationship between regulatory T cells (Treg) and chronic inflammation in the middle ear. Middle ear effusions (MEEs) and middle ear mucosae (MEM) were collected at days 3 and 14 and at 1 and 2 months after inoculation. Untreated mice served as controls. MEEs were used for bacterial counts and to measure the concentrations of cytokines. MEM were collected for histological evaluation and flow cytometric analysis. Inflammation of the MEM was prolonged throughout this study, and the incidence of NTHi culture-positive MEE was 38% at 2 months after inoculation. The levels of interleukin-1␤ (IL-␤), tumor necrosis factor alpha, IL-10, and transforming growth factor ␤ were increased in the middle ear for up to 2 months after inoculation. CD4؉ CD25 ؉ FoxP3 ؉ Treg accumulated in the middle ear, and the percentage of Treg in the MEM increased for up to 2 months after inoculation. Treg depletion induced a 99.9% reduction of bacterial counts in MEEs and also significantly reduced the ratio of NTHi culture-positive MEE. The levels of these cytokines were also reduced in MEEs. In summary, we developed a murine model of COM, and our findings indicate that Treg confer infectious tolerance to NTHi in the middle ear. Chronic otitis media (COM), including OM with effusion (OME) and recurrent OM, is characterized by clinical evidence of OM and resolution of middle ear effusion (MEE) between episodes. OME represents a spectrum of chronic disease states, ranging from serous to mucoid OM, and is associated with hearing loss, delayed speech development, permanent middle ear damage, and mucosal changes (1). Although COM remains a common problem in pediatric populations, its etiology and pathogenesis are not fully understood. Eustachian tube (ET) dysfunction is considered to be the underlying pathophysiologic event leading to most cases of OME in children. The most frequent causes of ET dysfunction include upper respiratory infections, adenoid tissue hypertrophy, and cleft palate (2, 3). In bacterial infection of COM, the majority of cases are caused by Gram-negative bacteria, whereas in acute OM, Gram-positive bacteria are also frequently isolated (4). Lipopolysaccharides are a component of Gram-negative bacteria that have been detected in human MEEs (5), and their levels are significantly higher in children with chronic OME than in children with acute OME (6). Lipopolysaccharides alone have also been shown to induce mucosal inflammation with the accumulation of effusion in the middle ears of animal models (7,8). Only 30% of MEEs from COM children yielded an unequivocally positive culture for aerobic bacteria (9). According to previous reports, components from Gram-negative bacteria are thought to induce COM in humans. However, recently, COM was reportedly associated with a persi...