Divergent mucosal and systemic responses in children in response to acute otitis media

Respiratory infection- and asthma-prone, low vaccine responder children demonstrate distinct mononuclear cell DNA methylation pathways

BACKGROUND

Infants with frequent viral and bacterial respiratory infections exhibit compromised immunity to routine immunizations. They are also more likely to develop chronic respiratory diseases in later childhood. This study investigated the feasibility of epigenetic profiling to reveal endotype-specific molecular pathways with potential for early identification and immuno-modulation. Peripheral blood mononuclear cells from respiratory infection allergy/asthma-prone (IAP) infants and non-infection allergy/asthma prone (NIAP) were retrospectively selected for genome-wide DNA methylation and single nucleotide polymorphism analysis. The IAP infants were enriched for the low vaccine responsiveness (LVR) phenotype (Fisher's exact p-value = 0.02).

RESULTS

An endotype signature of 813 differentially methylated regions (DMRs) comprising 238 lead CpG associations (FDR < 0.05) emerged, implicating pathways related to asthma, mucin production, antigen presentation and inflammasome activation. Allelic variation explained only a minor portion of this signature. Stimulation of mononuclear cells with monophosphoryl lipid A (MPL), a TLR agonist, partially reversed this signature at a subset of CpGs, suggesting the potential for epigenetic remodeling.

CONCLUSIONS

This proof-of-concept study establishes a foundation for precision endotyping of IAP children and highlights the potential for immune modulation strategies using adjuvants for future investigation.

Respiratory Infection- and Asthma-prone, Low Vaccine Responder Children Demonstrate Distinct Mononuclear Cell DNA Methylation Pathways

Background

Infants with frequent viral and bacterial respiratory infections exhibit compromised immunity to routine immunisations. They are also more likely to develop chronic respiratory diseases in later childhood. This study investigated the feasibility of epigenetic profiling to reveal endotype-specific molecular pathways with potential for early identification and immuno-modulation. Peripharal immune cells from respiratory infection allergy/asthma prone (IAP) infants were retrospectively selected for genome-wide DNA methylation and single nucleotide polymorphism analysis. The IAP infants were enriched for the low vaccine responsiveness (LVR) phenotype (Fishers Exact p-value = 0.01).

Results

An endotype signature of 813 differentially methylated regions (DMRs) comprising 238 lead CpG associations (FDR < 0.05) emerged, implicating pathways related to asthma, mucin production, antigen presentation and inflammasome activation. Allelic variation explained only a minor portion of this signature. Stimulation of mononuclear cells with monophosphoryl lipid A (MPLA), a TLR agonist, partially reversing this signature at a subset of CpGs, suggesting the potential for epigenetic remodelling.

Conclusions

This proof-of-concept study establishes a foundation for precision endotyping of IAP children and highlights the potential for immune modulation strategies using adjuvants for furture investigation.

Variability of vaccine responsiveness in early life

Vaccinations in early life elicit variable antibody and cellular immune responses, sometimes leaving fully vaccinated children unprotected against life-threatening infectious diseases. Specific immune cell populations and immune networks may have a critical period of development and calibration in a window of opportunity occurring during the first 100 days of early life. Among the early life determinants of vaccine responses, this review will focus on modifiable factors involving development of the infant microbiota and metabolome: antibiotic exposure, breast versus formula feeding, and Caesarian section versus vaginal delivery of newborns. How microbiota may serve as natural adjuvants for vaccine responses and how microbiota-derived metabolites influence vaccine responses are also reviewed. Early life poor vaccine responsiveness can be linked to increased infection susceptibility because both phenotypes share similar immunity dysregulation profiles. An early life pre-vaccination endotype, when interventions have the highest potential for success, should be sought that predicts vaccine response trajectories.

Resolution of otitis media in a humanized mouse model

Otitis media (OM) is one of the largest public health problems of children and has devastating impacts in developing countries. The substantial medical and human costs involved have led to research to understand the disease and improve treatment. Animal models of OM have yielded critical information about the immune, inflammatory and genetic mechanisms of OM. However, it is important to link animal studies to human immune and inflammatory responses. In recent years, "humanized" mice have become a valuable tool to study the human immune system in an animal model. Here we describe the first use of humanized mice to study OM. We demonstrate that humanized mice with a sufficient degree of engraftment recapitulate a normal middle ear (ME) inflammatory response to bacterial infection, including the recruitment of human immune cells, and exhibit normal recovery. Moreover, these animals exhibit regulated expression of human-specific immune and inflammatory genes in the ME. In contrast, mice with insufficient engraftment fail to resolve OM. This model has many potential uses in OM research, including using hematopoietic stem cells from patients with differing degrees of OM susceptibility, to understand the role of human immune responses in proneness to this common childhood disease.

Early life bacterial airway colonization, local immune mediator response and risk of otitis media

Introduction. Acute otitis media (AOM) is the most common bacterial infection in early childhood, but the underlying mechanisms making some children more susceptible are poorly understood.Aim. To examine the associations between bacterial airway colonization in early life and the risk of AOM and tympanostomy tube insertion (TTI), and whether such associations are modulated by an insufficient local immune mediator response to bacterial colonization.Methodology. Bacterial cultures from hypopharyngeal samples were obtained at 1 week, 1 month and 3 months of age in the Copenhagen Prospective Studies on Asthma in Childhood 2010 (COPSAC₂₀₁₀) cohort comprising 700 children. Twenty immune mediators were quantified from airway mucosal lining fluid sampled at 1 month. AOM symptoms were registered in a daily diary until 3 years. Information on TTI in the first 3 years was obtained from national registers.Results. Children colonized with Streptococcus pneumoniae at 1 month of age had increased incidence of AOM [aIRR 2.43 (1.14-5.21)] and children colonized with Moraxella catarrhalis at 1 month or Haemophilus influenzae at 3 months had an increased risk of TTI [aHR 1.45 (1.00-2.10) and 1.73 (1.10-2.71)]. There were no associations between the local immune mediator response to colonization and risk of AOM or TTI.Conclusion. Pathogenic bacterial airway colonization in early life was found to be associated with an increased risk of otitis media, albeit not consistently. These associations were independent of the local immune response to colonization.

Immunologic dysfunction contributes to the otitis prone condition

Acute Otitis Media (AOM) is a multifactorial disease occurring mostly in young children who are immunologically naïve to AOM pathogens. This review focuses on work from Rochester NY, USA over the past 12 years among young children who had AOM infections microbiologically-confirmed by tympanocentesis, so called "stringently-defined". Among stringently-defined otitis prone children deficiencies in fundamental immune defense mechanisms have been identified that contribute to the propensity of young children to experience recurrent AOM. Dysfunction in innate immune responses that cause an immunopathological impact in the nasopharynx have been discovered including inadequate proinflammatory cytokine response and poor epithelial cell repair. Adaptive immunity defects in B cell function and immunologic memory resulting in low levels of antibody to otopathogen-specific antigens allows repeated infections. CD4+ and CD8+ T cell function and memory defects significantly contribute. The immune profile of an otitis prone child resembles that of a neonate through the first year of life. Immunologic deficits in otitis prone children cause them to be unusually vulnerable to viral upper respiratory infections and respond inadequately to routine pediatric vaccines.

Serum antibody response to Moraxella catarrhalis proteins in stringently defined otitis prone children

BACKGROUND

Moraxella catarrhalis (Mcat) is a frequent pathogen of acute otitis media (AOM) in young children. Here we prospectively assessed naturally-induced serum antibodies to four Mcat vaccine candidate proteins in stringently defined otitis prone (sOP) and non-otitis prone (NOP) children age 6-36months old following nasopharyngeal (NP) colonization, at onset of AOM and convalescence from AOM.

METHODS

Serum IgG and IgM antibody against recombinant Mcat proteins, oligopeptide permease A (OppA), outer membrane protein (OMP) CD, hemagglutinin (Hag), and PilA clade 2 (PilA2), were quantitated by ELISA.

RESULTS

During NP colonization by Mcat all four antigens were immunogenic in both sOP and NOP children. However, sOP children had lower antibody responses than NOP children across age 6-36months, similar to our findings for protein vaccine candidates of Streptococcus pneumoniae (Spn) and Nontypeable Haemophilus influenzae (NTHi). sOP children displayed a later and lower peak of antibody rise than NOP children for all four antigens during NP colonization of Mcat. The age-dependent increase of antibody ranked as OppA>Hag5-9>OMP CD>PilA2 in both sOP and NOP children. Lower serum antibody levels to the Mcat antigens were measured in sOP compared to NOP children at the onset of AOM. We did not find a consistent significant increase of antibody at the convalescence phase after an AOM event.

CONCLUSIONS

sOP children is a highly vulnerable population that mount lower serum antibody responses to Mcat candidate vaccine proteins compared to NOP children during asymptomatic NP carriage and at onset of AOM.

Differences in innate immune response gene regulation in the middle ear of children who are otitis prone and in those not otitis prone

OBJECTIVE

Acute otitis media (AOM) causes an inflammatory response in the middle ear. We assessed differences in innate immune responses involved in bacterial defense at onset of AOM in children who were stringently defined as otitis prone (sOP) and children not otitis prone (NOP).

STUDY DESIGN

Innate immune genes analysis from middle ear fluid (MEF) samples of children.

METHODS

Genes of toll-like receptors (TLR), nod-like and retinoic acid-inducible gene-I-like receptors, downstream effectors important for inflammation and apoptosis, including cytokines and chemokines, were studied from MEF samples by using a real-time polymerase chain reaction array. Protein levels of differentially regulated genes were measured by Luminex.

RESULTS

Gene expression in MEF among children who were sOP was significantly different in upregulation of interleukin 8, secretory leukocyte peptidase inhibitor, and chemokine (C-C motif) ligand 3, and in downregulation of interferon regulatory factor 7 and its related signaling molecules interferon alpha, Toll-like receptor adaptor molecule 2, chemokine (C-C motif) ligand 5, and mitogen-activated protein kinase 8 compared with children who were NOP. Differences in innate gene regulation were similar when AOM was caused by Streptococcus pneumoniae or nontypeable Haemophilus influenzae.

CONCLUSION

Innate-immune response genes are differentially regulated in children who were sOP compared with children with NOP.

Panel 8: Report on Recent Advances in Molecular and Cellular Biochemistry

Objectives To update the medical literature on recent cellular and molecular advances in otitis media disease models with a principal focus on developments in the past 5 years. We also aim to explain recent translational advances in cellular and molecular biology that have influenced our understanding and management of otitis media. Data Sources PubMed-indexed peer-reviewed articles. Review Methods A comprehensive review of the literature was conducted with the term otitis media and the following search terms: molecular biology, cell biology, innate immunity, oxidative stress, mucins, molecular diagnostics. Included articles were published in the English language from January 1, 2010, to July 31, 2015. Implications for Practice The molecular understanding of otitis media disease progression has rapidly advanced over the last 5 years. The roles of inflammation, mucins, and cell signaling mechanisms have been elucidated and defined. Advances in the field provide a plethora of opportunities for innovative molecular targeting in the development of novel therapeutic strategies for otitis media.

Panel 5: Immunology

Objective

To perform a state-of-the-art review of the literature from January 2012 through May 2015 on studies that advanced our knowledge of the innate and adaptive immunology related to otitis media. This review also proposes future directions for research in this area.

Data Sources

PubMed database of the National Library of Medicine.

Review Methods

Three subpanels comprising experts in the field focused on sections relevant to cytokines, innate immunity, and adaptive immunity. The review focused on animal, cell line, and human studies and was critical in relation to the recommendations from the previous publication and for determination of the proposed goals and priorities. The panel met at the 18th International Symposium on Recent Advances in Otitis Media in June 2015 to consolidate its prior search results and discuss, plan, and refine the review. The panel approved the final draft.

Conclusion

From 2012 to 2014, tremendous progresses in immunology of otitis media were established—especially in the areas of innate immunity associated with the pathogenesis of otitis media.

Implications for Practice

The advances of the past 4 years formed the basis for a series of short- and long-term research goals in an effort to guide the field. Accomplishing these goals will provide opportunities for the development of novel interventions, including new ways to better treat and prevent otitis media, especially for recurrent otitis media.

No evidence for impaired humoral immunity to pneumococcal proteins in Australian Aboriginal children with otitis media

BACKGROUND

The Australian Aboriginal population experiences disproportionately high rates of otitis media (OM). Streptococcus pneumoniae is one of the main pathogens responsible for OM and currently no vaccine offering cross strain protection exists. Vaccines consisting of conserved antigens to S. pneumoniae may reduce the burden of OM in high-risk populations; however no data exists examining naturally acquired antibody in Aboriginal children with OM.

METHODS

Serum and salivary IgA and IgG were measured against the S. pneumoniae antigens PspA1 and 2, CbpA and Ply in a cross sectional study of 183 children, including 36 non-Aboriginal healthy control children and 70 Aboriginal children and 77 non-Aboriginal children undergoing surgery for OM using a multiplex bead assay.

RESULTS

Significant differences were observed between the 3 groups for serum anti-PspA1 IgA, anti-CbpA and anti-Ply IgG and for all salivary antibodies assessed. Aboriginal children with a history of OM had significantly higher antibody titres than non-Aboriginal healthy children with no history of OM and non-Aboriginal children with a history of OM for several proteins in serum and saliva. Non-Aboriginal children with a history of OM had significantly higher salivary anti-PspA1 IgG than healthy children, while all other titres were comparable between the groups.

CONCLUSIONS

Conserved vaccine candidate proteins from S. pneumoniae induce serum and salivary antibody responses in Aboriginal and non-Aboriginal children with a history of OM. Aboriginal children do not have an impaired antibody response to the antigens measured from S. pneumoniae and they may represent vaccine candidates in Indigenous populations.

Ten-Year Study of the Stringently Defined Otitis-prone Child in Rochester, NY

This review summarizes a prospective, longitudinal 10-year study in Rochester, NY, with virtually every clinically diagnosed acute otitis media (AOM) confirmed by bacterial culture of middle ear fluid. Children experiencing 3 episodes within 6 months or 4 episodes in 12 months were considered stringently defined otitis prone (sOP). We found stringent diagnosis compared with clinical diagnosis reduced the frequency of children meeting the OP definition from 27% to 6% resulting in 14.8% and 2.4% receiving tympanostomy tubes, respectively. Significantly more often respiratory syncytial virus infection led to AOM in sOP than non-otitis-prone children that correlated with diminished total respiratory syncytial virus-specific serum IgG. sOP children produced low levels of antibody to Streptococcus pneumoniae and Haemophilus influenzae candidate vaccine protein antigens and to routine pediatric vaccines. sOP children generated significantly fewer memory B cells, functional and memory T cells to otopathogens following nasopharyngeal colonization and AOM than non-otitis-prone children and they had defects in antigen-presenting cells.

Management of acute otitis media in children six months of age and older

Acute otitis media (AOM) continues to be a common infection in young children. Milder disease, usually due to viruses or less virulent bacteria, resolves equally quickly with or without antibiotics. A bulging tympanic membrane, especially if yellow or hemorrhagic, has a high sensitivity for AOM that is likely to be bacterial in origin and is a major diagnostic criterion for AOM. Perforation of the tympanic membrane with purulent discharge similarly indicates a bacterial cause. Immediate antibiotic treatment is recommended for children who are highly febrile (≥39°C), moderately to severely systemically ill or who have very severe otalgia, or have already been significantly ill for 48 h. For all other cases, parents can be provided with a prescription for antibiotics to fill if the child does not improve in 48 h or the child can be reassessed if this occurs. Amoxicillin remains the clear drug of choice. Ten days of therapy is appropriate for children <2 years of age, whereas older children can be treated for five days.

Peripheral blood antigen presenting cell responses in otitis-prone and non-otitis-prone infants

Stringently defined otitis-prone (sOP) children represent a new classification of the otitis-prone condition. Previous studies showed dysfunction in Ab, B-cell memory and T-cell memory responses. We sought to determine whether there are defects in numbers, phenotype and/or function of professional APC in the peripheral blood of sOP infants. APC phenotypic counts, MHC II expression and intracellular cytokine levels were determined in response to TLR7/8 (R848) stimulation by flow cytometry. Innate immune mRNA expression was measured using RT-PCR and cytokines were measured using Luminex technology. Significant (P < 0.05) increases in the phenotypic counts of monocytes and conventional dendritic cells but not plasmacytoid DCs were observed in sOP compared with non-otitis-prone (NOP) age-matched infants. No significant differences in APC activation or function were observed. Expression of various TLRs, intracellular signaling molecules and downstream cytokines was also not found to be significantly different between sOP and NOP infants. Higher numbers of APCs in sOP infants suggest the possibility of a persistent mucosal inflammatory status. Transcriptional and cytokine profiles of PBMCs among sOP infants suggest their systemic innate responses are not different compared to NOP infants.