Matthew Morris

Epidemiology of Acute Otitis Media in the Postpneumococcal Conjugate Vaccine Era

In this 10-year prospective study, we capture the epidemiology and risk factors of AOM and the otitis-prone condition in the PCV era. OBJECTIVES: To study the epidemiology of acute otitis media (AOM), especially the otitis-prone condition, during the pneumococcal conjugate vaccines 7 and 13 era. METHODS: Six hundred and fifteen children were prospectively managed from 6 to 36 months of life during a 10-year time frame (June 2006–June 2016). All clinical diagnoses of AOM were confirmed by tympanocentesis and bacterial culture of middle ear fluid. RESULTS: By 1 year of age, 23% of the children experienced ≥1 episode of AOM; by 3 years of age, 60% had ≥1 episodes of AOM, and 24% had ≥3 episodes. The peak incidence occurred at 6 to 12 months of life. Multivariable analysis of demographic and environmental data revealed a significantly increased risk of AOM associated with male sex, non-Hispanic white race, family history of recurrent AOM, day care attendance, and early occurrence of AOM. Risk factors for stringently defined (tympanocentesis-confirmed) otitis proneness, in which children suffered at least 3 episodes of AOM in a 6-month period or at least 4 within a year, were male sex, day care attendance, and family history of AOM, whereas breastfeeding in the first 6 months of life was protective. Stringently defined otitis prone children were also likely to experience their first AOM episode at a younger age. The proportion of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis causing AOM had dynamic changes during the past decade. CONCLUSIONS: We conclude that the epidemiology but not the risk factors for AOM have undergone substantial changes since the introduction of pneumococcal conjugate vaccines.

Neonatal Vaccination: Challenges and Intervention Strategies

Background: While vaccines have been tremendously successful in reducing the incidence of serious infectious diseases, newborns remain particularly vulnerable in the first few months of their life to life-threatening infections. A number of challenges exist to neonatal vaccination. However, recent advances in the understanding of neonatal immunology offer insights to overcome many of those challenges. Objective: This review will present an overview of the features of neonatal immunity which make vaccination difficult, survey the mechanisms of action of available vaccine adjuvants with respect to the unique features of neonatal immunity, and propose a possible mechanism contributing to the inability of neonates to generate protective immune responses to vaccines. Methods: We surveyed recent published findings on the challenges to neonatal vaccination and possible intervention strategies including the use of novel vaccine adjuvants to develop efficacious neonatal vaccines. Results: Challenges in the vaccination of neonates include interference from maternal antibody and excessive skewing towards Th2 immunity, which can be counteracted by the use of proper adjuvants. Conclusion: Synergistic stimulation of multiple Toll-like receptors by incorporating well-defined agonist-adjuvant combinations to vaccines is a promising strategy to ensure a protective vaccine response in neonates.

Familial and microbiological contribution to the otitis–prone condition

OBJECTIVE Our group has an ongoing clinical research project investigating the immunology of the otitis-prone (OP) phenotype. In light of evidence that this condition arises from underlying immunological defects, we examined our sample population of stringently defined OP (sOP) children suffering 3 episodes of acute otitis media within 6 months or 4 within a year for a familial association with the sOP phenotype. METHODS We analyzed the frequency of sOP within and between families and the nasopharyngeal (NP) otopathogen colonization patterns within and between families. RESULTS The presence of sOP siblings significantly predicted that additional children in the same family would likewise become sOP, with an odds ratio of 3.7 (95% CI 0.77-15.2, 95% lower bound 0.95). We further present evidence for an environmental contribution to this effect by means of prolonged exposure to otopathogens within family units. CONCLUSION sOP children have a significant familial association. The tendency of siblings to share similar patterns of microbial NP colonization contributes to this association. Further research is necessary to determine whether and to what extent genetics are involved.

Functional Immune Cell Differences Associated With Low Vaccine Responses in Infants

BACKGROUND We sought to understand why some children respond poorly to vaccinations in the first year of life. METHODS A total of 499 children (6-36 months old) provided serum and peripheral blood mononuclear cell samples after their primary and booster vaccination. Vaccine antigen-specific antibody levels were analyzed with enzyme-linked immunosorbent assay, and frequency of memory B cells, functional T-cell responses, and antigen-presenting cell responses were assessed in peripheral blood mononuclear cell samples with flow cytometric analysis. RESULTS Eleven percent of children were low vaccine responders, defined a priori as those with subprotective immunoglobulin G antibody levels to ≥66% of vaccines tested. Low vaccine responders generated fewer memory B cells, had reduced activation by CD4(+) and CD8(+) T cells on polyclonal stimulation, and displayed lower major histocompatibility complex II expression by antigen-presenting cells. CONCLUSIONS We conclude that subprotective vaccine responses in infants are associated with a distinct immunologic profile.

Adenoidal follicular T helper cells provide stronger B-cell help than those from tonsils.

The tonsils and adenoids are secondary lymphoid organs, where antigen processing and immune cell development occur to control bacterial colonization and infection in the upper respiratory tract. Both organs are abundant in follicular T helper cells (TFH), a subset of T cells specialized for promoting B‐cell development. There are no prior studies on differences between the immune cells of the tonsils and adenoids and whether the cells function differently.

A PCR-based method for quantifying neutrophils in human nasal secretions

Neutrophil recruitment to the nasopharynx (NP) is a central event in resolution of NP-initiated microbial infections. A vigorous neutrophil response in infected tissues is also associated with the outcome of adverse tissue pathology. Therefore, differences in infection-induced tissue neutrophil numbers may correlate with pathogenesis events. Existing methods of quantifying neutrophils require evaluation of NP samples within hours of procurement as flow cytometry based cell quantification methods require live neutrophil cells. Therefore, we developed a novel RT-PCR method that could reliably quantify neutrophil counts in frozen NP wash samples. mRNA transcripts of the genes encoding CD16, CD18, and CD62L were identified as neutrophil-specific in NP samples and not significantly variable in response to stimulation by heat killed bacteria, and can be used to derive an accurate assessment of neutrophil content in a sample even in the presence of epithelial cells. Using flow cytometry as a comparator, the method was validated in human NP wash samples. We conclude that this PCR-based method should prove useful for providing a quantitative estimate of neutrophil recruitment to the NP during infection and pathogenesis.

High-fidelity discrete modeling of the HPA axis: a study of regulatory plasticity in biology

BackgroundThe hypothalamic-pituitary-adrenal (HPA) axis is a central regulator of stress response and its dysfunction has been associated with a broad range of complex illnesses including Gulf War Illness (GWI) and Chronic Fatigue Syndrome (CFS). Though classical mathematical approaches have been used to model HPA function in isolation, its broad regulatory interactions with immune and central nervous function are such that the biological fidelity of simulations is undermined by the limited availability of reliable parameter estimates.MethodHere we introduce and apply a generalized discrete formalism to recover multiple stable regulatory programs of the HPA axis using little more than connectivity between physiological components. This simple discrete model captures cyclic attractors such as the circadian rhythm by applying generic constraints to a minimal parameter set; this is distinct from Ordinary Differential Equation (ODE) models, which require broad and precise parameter sets. Parameter tuning is accomplished by decomposition of the overall regulatory network into isolated sub-networks that support cyclic attractors. Network behavior is simulated using a novel asynchronous updating scheme that enforces priority with memory within and between physiological compartments.ResultsConsistent with much more complex conventional models of the HPA axis, this parsimonious framework supports two cyclic attractors, governed by higher and lower levels of cortisol respectively. Importantly, results suggest that stress may remodel the stability landscape of this system, favoring migration from one stable circadian cycle to the other. Access to each regime is dependent on HPA axis tone, captured here by the tunable parameters of the multi-valued logic. Likewise, an idealized glucocorticoid receptor blocker alters the regulatory topology such that maintenance of persistently low cortisol levels is rendered unstable, favoring a return to normal circadian oscillation in both cortisol and glucocorticoid receptor expression.ConclusionThese results emphasize the significance of regulatory connectivity alone and how regulatory plasticity may be explored using simple discrete logic and minimal data compared to conventional methods.

Comparison of direct-plating and broth-enrichment culture methods for detection of potential bacterial pathogens in respiratory secretions

Objective. We compared the recovery of potential respiratory bacterial pathogens and normal flora from nasopharyngeal specimens collected from children during health and at the onset of acute otitis media (AOM) by selective direct‐plating and overnight broth‐enrichment. Methods. Overall, 3442 nasal wash (NW) samples collected from young children were analysed from a 10‐year prospective study. NWs were cultured by (1) direct‐plating to TSAII/5% sheep blood agar and chocolate agar plates and (2) overnight broth‐enrichment in BacT/ALERT SA‐broth followed by plating. Standard microbiology techniques were applied to identify three dominant respiratory bacterial pathogens: Streptococcus pneumoniae (Spn), Haemophilus influenzae (Hflu) and Moraxella catarrhalis (Mcat) as well as two common nasal flora, Staphylococcus aureus (SA) and alpha‐haemolytic Streptococci (AHS). Results/Key findings. Direct‐plating of NW resulted in isolation of Spn from 37.8%, Hflu from 13.6% and Mcat from 33.2% of samples. In comparison, overnight broth‐enrichment isolated fewer Spn (30.1%), Hflu (6.2%) and Mcat (16.2%) (P<0.001‐0.0001). Broth‐enrichment resulted in significant increased isolation of SA (6.0%) and AHS (30.1%) (P<0.0001). Competition between bacterial species in broth when both species were detected by direct‐plating was assessed, and it was found that SA and AHS out‐competed other species during broth‐enrichment when samples were collected from healthy children but not during AOM. In middle ear fluids (MEF) at the onset of AOM, broth‐enrichment resulted in higher recovery of Spn (+10.4%, P<0.001), Hflu (+4.4%, P=0.39) and Mcat (+13.5%, <0.001). Conclusion. Broth‐enrichment significantly reduces the accurate detection of bacterial respiratory pathogens and increases identification of SA and AHS in NW. Broth‐enrichment improves detection of bacterial respiratory pathogens in MEF samples.

Prospective study of the innate cellular immune response in low vaccine responder children

We recently reported our findings from a longitudinal, prospective study where we identified 10% infants who were low vaccine responders (LVR) at age 9–12 mo following routine primary series vaccine schedule. We found multiple cellular deficiencies in LVR children, including low number of memory B cells, reduced polyclonal stimulation of naïve/memory T cell response and suboptimal APC response. These children outgrew their poor vaccine response by the time they received booster doses of vaccine. Studies in human infant innate immunity are rare because of the unique challenges in specimen collection. As innate immunity instructs adaptive immunity, we hypothesized that the primary immune defect lies with innate immunity and in this study we sought to determine the ontogeny of innate immune response in LVR children between 6 and 36 mo of age. Interestingly, suboptimal APC response observed in LVR children at 6–9 mo of age characterized by significantly (P < 0.05) low basal MHC II expression, low R848 induced IRF7 fold change, as well as low IFN-α, IL-12p70 and IL-1β levels, came to parity with normal vaccine responders by 12–15 mo of age, suggesting that the observed immune deficiency in LVR children may be the result of delayed maturation of immune system.

Streptococcus pneumoniae burden and nasopharyngeal inflammation during acute otitis media

Streptococcus pneumoniae (Spn) is a common respiratory pathogen and a frequent cause of acute otitis media (AOM) in children. The first step in bacterial pathogenesis of AOM is the establishment of asymptomatic colonization in the nasopharynx. We studied Spn bacterial burden in conjunction with neutrophil recruitment and inflammatory gene transcription and cytokine secretion in samples of nasal wash collected from normal and otitis-prone children during health, viral upper respiratory infection without middle ear involvement (URI) and AOM. We found no significant associations between otitis-prone status and any of the measured parameters. However, Spn bacterial burden was significantly correlated with neutrophil recruitment, transcription of IL-8, TNF-α and SOD2, and secretion of TNF-α. We also found that transcription of IL-8 and TNF-α mRNA by neutrophils was significantly correlated with the secretion of these cytokines into the nasopharynx. We conclude that Spn bacterial burden in the NP is a major determinant of neutrophil recruitment to the NP and activity during URI and AOM, and that neutrophils are contributors to the secretion of IL-8 and TNF-α in the NP when the Spn burden is high.