Differences in Pneumococcal and Haemophilus influenzae Natural Antibody Development in Papua New Guinean Children in the First Year of Life

Inflammatory Responses to Non-Typeable Haemophilus influenzae Clinical Isolates from Invasive and Non-Invasive Infections

Non-typeable Haemophilus influenzae (NTHi) is often asymptomatically carried in the upper airways but can cause a wide spectrum of disease conditions, from local respiratory tract infections to invasive disease such as sepsis or meningitis. The factors driving NTHi's transition from benign carriage to severe systemic disease remain poorly understood. It is unknown whether NTHi strains associated with invasive or non-invasive disease differ in their capacity to trigger inflammatory responses in innate immune cells. To address this question, we have used an in vitro infection model of human THP-1 cells differentiated to macrophages. To evaluate inflammatory responses, we studied the expression of 3 prototypic pro-inflammatory molecules, ICAM-1, TNF-α, and IL-1β. The role of lipooligosaccharide in triggering inflammatory responses was assessed using inhibition of Toll-like receptor 4 signaling. Our experiments demonstrated that NTHi strains isolated from cases of invasive and non-invasive infections were similarly able to induce strong activations of macrophage pro-inflammatory responses. Our findings support the hypothesis that the development of invasive versus non-invasive NTHi disease may be more significantly influenced by the adaptive immune response than the innate immune response.

Haemophilus influenzae and pneumococci: Co-colonization, interactions, cooperation and competition

Nontypeable Haemophilus influenzae (NTHi) and Streptococcus pneumoniae (pneumococcus) are pathobionts that share common environmental niches within the upper respiratory tract. They can form part of the resident upper airway microbiota, but under certain environmental circumstances become pathogenic and induce disease. In children, both organisms have a considerable impact on the healthcare system, commonly causing acute otitis media and pneumonia. They are also associated with chronic biofilm-mediated respiratory infections, such as persistent middle ear effusions and chronic suppurative otitis media, and in the lower airways with protracted bacterial bronchitis and bronchiectasis. Consequently, both organisms are responsible for large numbers of antibiotic prescriptions and substantial healthcare costs. The complex relationship between NTHi and pneumococcal co-interaction during colonization, infection and biofilm formation is poorly understood and a greater understanding is needed to facilitate development of future therapies, and novel interventions and prevention strategies. Co-infections with both bacteria can result in more severe disease, with disease severity likely mediated by their ability to cooperate in some in vivo niches. However, this relationship is not always straightforward, as under certain conditions, these two bacteria compete rather than cooperate. Current opinion supports developing a vaccine targeting NTHi strains, as well as a combined vaccine targeting both NTHi and pneumococci to decrease the respiratory disease burden in young children. This review summarizes our current knowledge of the interactions between NTHi and pneumococci and speculates on the future directions of research to understand how these bacteria co-exist and how to better prevent and treat NTHi and pneumococcal infection.

Protective Characteristics of Human Breast Milk on Early Childhood Otitis Media: A Narrative Review

Introduction: Human breast milk (HBM) contains a complex and dynamically changing variety of factors that contribute to the infant's developing immune system's ability to fight upper respiratory tract infections, including otitis media (OM). We sought to summarize the current evidence on the protective characteristics of HBM, through direct or donated feeding, toward early childhood OM. Methods: For this narrative review, we performed a literature search on OM in the context of HBM feeding in the PubMed, Embase, and Google Scholar databases, between January 1, 2008, and July 1, 2023. Results: Immunoglobulin A (IgA) provides a short-term immunity of 2-3 days against otopathogens causing OM. IgA-mediated immunity is effective against OM up to 7 months of age if breastfeeding continues. The role of transferred IgM and IgG in HBM is unclear. Although there is a potential protective value of microRNA, hormones, oligosaccharides, stem cells, and interleukins present in HBM, their role is unclear. Any duration of breastfeeding is superior to no breastfeeding in OM risk reduction, with a big variability among studies (odds ratio 0.23-0.81, depending on the duration). Duration of breastfeeding ≥6 months was found to be the most effective in OM risk reduction, but there was no evidence of continued benefits after 2 years of age. Expressed breastfeeding was not shown to be more beneficial. The protective values of donor HBM against OM are still undetermined. Conclusion: HBM has numerous components that contribute to protection against early childhood OM.

Overcoming barriers: a review on innovations in drug delivery to the middle and inner ear

Despite significant advances in the development of therapeutics for hearing loss, drug delivery to the middle and inner ear remains a challenge. As conventional oral or intravascular administration are ineffective due to poor bioavailability and impermeability of the blood-labyrinth-barrier, localized delivery is becoming a preferable approach for certain drugs. Even then, localized delivery to the ear precludes continual drug delivery due to the invasive and potentially traumatic procedures required to access the middle and inner ear. To address this, the preclinical development of controlled release therapeutics and drug delivery devices have greatly advanced, with some now showing promise clinically. This review will discuss the existing challenges in drug development for treating the most prevalent and damaging hearing disorders, in particular otitis media, perforation of the tympanic membrane, cholesteatoma and sensorineural hearing loss. We will then address novel developments in drug delivery that address these including novel controlled release therapeutics such as hydrogel and nanotechnology and finally, novel device delivery approaches such as microfluidic systems and cochlear prosthesis-mediated delivery. The aim of this review is to investigate how drugs can reach the middle and inner ear more efficiently and how recent innovations could be applied in aiding drug delivery in certain pathologic contexts.

Evidence of maternal transfer of antigen-specific antibodies in serum and breast milk to infants at high-risk of S. pneumoniae and H. influenzae disease

Introduction

Children in low-mid income countries, and First Nations children in high-income countries, experience disproportionately high rates of Streptococcus pneumoniae and Haemophilus influenzae infections and diseases including pneumonia and otitis media. We previously observed that infants from Papua New Guinea had no evidence of waning maternal immunity for H. influenzae-specific antibodies. In this study, we assessed S. pneumoniae and H. influenzae antibody titres in Australian First Nation mothers and infants to determine antigen-specific antibody ontogenies and whether H. influenzae antibody titres in infants were due to low maternal antibody titres or lack of placental transfer.

Methods

Breast milk, infant nasopharyngeal swabs and ear assessment data were collected 1-, 2-, 7-months post-birth as well as maternal, cord and 7-month-old infant sera, from 85 Australian Aboriginal and Torres Strait Islander mother-infant pairs. Serum IgG and breast milk IgG and IgA antibody titres to S. pneumoniae antigens (PspA1, PspA2, CbpA, Ply) and H. influenzae antigens (PD, ChimV4, OMP26, rsPilA) were measured.

Results

IgG titres in maternal and cord sera were similar for all antigens, except Ply (higher in cord; p=0.004). Sera IgG titres at 7-months of age were lower than cord sera IgG titres for all S. pneumoniae antigens (p<0.001). Infant sera IgG titres were higher than cord sera for H. influenzae PD (p=0.029), similar for OMP26 (p=0.817) and rsPilA (p=0.290), and lower for ChimV4 (p=0.004). Breast milk titres were similar for all antigens at 1, 2 and 7-months except OMP26 IgA (lower at 7-months than 1-month; p=0.035), PspA2 IgG (p=0.012) and Ply IgG that increased by 7-months (p=0.032). One third of infants carried nontypeable Haemophilus influenzae (NTHi), 45% carried S. pneumoniae and 52% had otitis media (OM) observed at least once over the 7-months. 73% of infants who carried either S. pneumoniae or NTHi, also had otitis media observed.

Conclusions

Similarities between maternal and cord IgG titres, and absence of waning, support a lack of maternal H. influenzae IgG antibodies available for cross-placental transfer. Increased maternal anti-PD IgG could offer some protection from early carriage with NTHi, and maternal immunisation strategies should be considered for passive-active immunisation of infants to protect against S. pneumoniae and H. influenzae diseases.

Trial registration

ClinicalTrials.gov NCT00714064 and NCT00310349.

Australian Aboriginal Otitis-Prone Children Produce High-Quality Serum IgG to Putative Nontypeable Haemophilus influenzae Vaccine Antigens at Lower Titres Compared to Non-Aboriginal Children

Background

Nontypeable Haemophilus influenzae (NTHi) is the most common bacterial otopathogen associated with otitis media (OM). NTHi persists in biofilms within the middle ears of children with chronic and recurrent OM. Australian Aboriginal children suffer exceptionally high rates of chronic and recurrent OM compared to non-Aboriginal children. NTHi protein vaccines comprised of antigens associated with both adhesion and persistence in a biofilm are under development and could be beneficial for children with chronic and recurrent OM. Understanding the ontogeny of natural antibody development to these antigens provides insight into the value of vaccinating with particular antigens.

Methods

An in-house multiplex fluorescent bead immunoassay was used to measure serum IgG titres and avidity for three putative vaccine antigens: recombinant soluble PilA (rsPilA), ChimV4, and outer membrane protein 26 (OMP26) in sera from Australian Aboriginal otitis-prone children (n=77), non-Aboriginal otitis-prone children (n=70) and non-otitis-prone children (n=36). Serum IgG titres were adjusted for age, and geometric mean concentrations (GMCs) were compared between groups using a univariate analysis model. Antibody avidity was calculated as a relative avidity index and compared between groups using ANOVA.

Results

Australian Aboriginal otitis-prone children had lower serum IgG titres to rsPilA and ChimV4 than non-Aboriginal otitis-prone children (p<0.001), and non-otitis-prone children (p<0.020). No differences were observed between serum IgG titres from non-Aboriginal otitis-prone children and non-otitis-prone children. There were also no differences in the proportion of high avidity IgG specific for these antigens between these groups. Serum IgG titres to OMP26 were similar between all groups (p>0.670) although otitis-prone children had a higher proportion of high avidity antibodies to this antigen.

Conclusions

Australian Aboriginal otitis-prone children had lower serum IgG titres to 2/3 major NTHi vaccine candidate antigens, suggesting these children are unable to develop persistent IgG responses due to repeated NTHi exposure. These reduced IgG titres may relate to earlier and more frequent exposure to diverse NTHi strains in Aboriginal children through carriage or infection. These data suggest that Aboriginal children may benefit from immunisation with vaccines containing these antigens to increase titres of protective antibodies.

Study Protocol for Preventing Early-Onset Pneumonia in Young Children Through Maternal Immunisation: A Multi-Centre Randomised Controlled Trial (PneuMatters)

Background: Preventing and/or reducing acute lower respiratory infections (ALRIs) in young children will lead to substantial short and long-term clinical benefits. While immunisation with pneumococcal conjugate vaccines (PCV) reduces paediatric ALRIs, its efficacy for reducing infant ALRIs following maternal immunisation has not been studied. Compared to other PCVs, the 10-valent pneumococcal-Haemophilus influenzae Protein D conjugate vaccine (PHiD-CV) is unique as it includes target antigens from two common lower airway pathogens, pneumococcal capsular polysaccharides and protein D, which is a conserved H. influenzae outer membrane lipoprotein. Aims: The primary aim of this randomised controlled trial (RCT) is to determine whether vaccinating pregnant women with PHiD-CV (compared to controls) reduces ALRIs in their infants' first year of life. Our secondary aims are to evaluate the impact of maternal PHiD-CV vaccination on different ALRI definitions and, in a subgroup, the infants' nasopharyngeal carriage of pneumococci and H. influenzae, and their immune responses to pneumococcal vaccine type serotypes and protein D. Methods: We are undertaking a parallel, multicentre, superiority RCT (1:1 allocation) at four sites across two countries (Australia, Malaysia). Healthy pregnant Australian First Nation or Malaysian women aged 17-40 years with singleton pregnancies between 27⁺⁶ and 34⁺⁶ weeks gestation are randomly assigned to receive either a single dose of PHiD-CV or usual care. Treatment allocation is concealed. Study outcome assessors are blinded to treatment arms. Our primary outcome is the rate of medically attended ALRIs by 12-months of age. Blood and nasopharyngeal swabs are collected from infants at birth, and at ages 6- and 12-months (in a subset). Our planned sample size (n = 292) provides 88% power (includes 10% anticipated loss to follow-up). Discussion: Results from this RCT potentially leads to prevention of early and recurrent ALRIs and thus preservation of lung health during the infant's vulnerable period when lung growth is maximum. The multicentre nature of our study increases the generalisability of its future findings and is complemented by assessing the microbiological and immunological outcomes in a subset of infants. Clinical Trial Registration: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374381, identifier: ACTRN12618000150246.