Lack of the hyaluronan receptor CD44 affects the course of bacterial otitis media and reduces leukocyte recruitment to the middle ear

An infant mouse model of influenza-driven nontypeable Haemophilus influenzae colonization and acute otitis media suitable for preclinical testing of novel therapies

Nontypeable Haemophilus influenzae (NTHi) is a major otitis media (OM) pathogen, with colonization a prerequisite for disease development. Most acute OM is in children <5 years old, with recurrent and chronic OM impacting hearing and learning. Therapies to prevent NTHi colonization and/or disease are needed, especially for young children. Respiratory viruses are implicated in driving the development of bacterial OM in children. We have developed an infant mouse model of influenza-driven NTHi OM, as a preclinical tool for the evaluation of safety and efficacy of clinical therapies to prevent NTHi colonization and the development of OM. In this model, 100% of infant BALB/cARC mice were colonized with NTHi, and all developed NTHi OM. Influenza A virus (IAV) facilitated the establishment of dense (1 × 105 CFU/mL) and long-lasting (6 days) NTHi colonization. IAV was essential for the development of NTHi OM, with 100% of mice in the IAV/NTHi group developing NTHi OM compared with 8% of mice in the NTHi only group. Histological analysis and cytokine measurements revealed that the inflammation observed in the middle ear of the infant mice with OM reflected inflammation observed in children with OM. We have developed the first infant mouse model of NTHi colonization and OM. This ascension model uses influenza-driven establishment of OM and reflects the clinical pathology of bacterial OM developing after a respiratory virus infection. This model provides a valuable tool for testing therapies to prevent or treat NTHi colonization and disease in young children.

PANEL 3: Otitis media animal models, cell culture, tissue regeneration & pathophysiology

OBJECTIVE

To review and summarize recently published key articles on the topics of animal models, cell culture studies, tissue biomedical engineering and regeneration, and new models in relation to otitis media (OM).

DATA SOURCE

Electronic databases: PubMed, National Library of Medicine, Ovid Medline.

REVIEW METHODS

Key topics were assigned to the panel participants for identification and detailed evaluation. The PubMed reviews were focused on the period from June 2019 to June 2023, in any of the objective subject(s) or keywords listed above, noting the relevant references relating to these advances with a global overview and noting areas of recommendation(s). The final manuscript was prepared with input from all panel members.

CONCLUSIONS

In conclusion, ex vivo and in vivo OM research models have seen great advancements in the past 4 years. From the usage of novel genetic and molecular tools to the refinement of in vivo inducible and spontaneous mouse models, to the introduction of a wide array of reliable middle ear epithelium (MEE) cell culture systems, the next five years are likely to experience exponential growth in OM pathophysiology discoveries. Moreover, advances in these systems will predictably facilitate rapid means for novel molecular therapeutic studies.

Otitis media: Interactions between host and environment, immune and inflammatory responses

OBJECTIVE

To review and highlight progress in otitis media (OM) research in the areas of immunology, inflammation, environmental influences and host-pathogen responses from 2019 to 2023. Opportunities for innovative future research were also identified.

DATA SOURCES

PubMed database of the National Library of Medicine.

REVIEW METHODS

Key topics were assigned to each panel member for detailed review. Search of the literature was from June 2019 until February 2023. Draft reviews were collated, circulated, and discussed among panel members at the 22nd International Symposium on Recent Advances in Otitis Media in June 2023. The final manuscript was prepared and approved by all the panel members.

CONCLUSIONS

Important advances were identified in: environmental influences that enhance OM susceptibility; polymicrobial middle ear (ME) infections; the role of adaptive immunity defects in otitis-proneness; additional genes linked to OM; leukocyte contributions to OM pathogenesis and recovery; and novel interventions in OM based on host responses to infection. Innovative areas of research included: identification of novel bacterial genes and pathways important for OM persistence, bacterial adaptations and evolution that enhance chronicity; animal and human ME gene expression, including at the single-cell level; and Sars-CoV-2 infection of the ME and Eustachian tube.

Culture of leukocyte-derived cells from human peripheral blood: Increased expression of pluripotent genes OCT4, NANOG, SOX2, self-renewal gene TERT and plasticity

There are few stem cells in human peripheral blood (PB). Increasing the population and plasticity of stem cells in PB and applying it to regenerative medicine require suitable culture methods. In this study, leukocyte populations 250 mL of PB were collected using a blood separator before that were cultured in optimal cell culture medium for 4 to 7 days. After culturing, stemness characteristics were analyzed, and red blood cells were removed from the cultured cells. In our results, stemness markers of the leukocyte populations Sca-1+ CD45+, CD117+ CD45+, and very small embryonic-like stem cells CD34+ Lin- CD45- and CXCR4+ Lin- CD45- were significantly increased. Furthermore, the expression of stem cell genes OCT4 (POU5F1), NANOG, SOX2, and the self-renewal gene TERT was analyzed by quantitative real-time polymerase chain reaction in these cells, and it showed a significant increase. These cells could be candidates for multi-potential cells and were further induced using trans-differentiation culture methods. These cells showed multiple differentiation potentials for osteocytes, nerve cells, cardiomyocytes, and hepatocytes. These results indicate that appropriate culture methods can be applied to increase expression of pluripotent genes and plasticity. Leukocytes of human PB can be induced to trans-differentiate into pluripotent potential cells, which will be an important breakthrough in regenerative medicine.

The Impact of the Animal Housing System on Immune Cell Composition and Function in the Blood of Dromedary Camels

Simple Summary

The present study investigated the impacts of a change in animal housing system on selected parameters of the camel immune system. Samples collected from camels during a free-ranging time were compared with samples collected from the same camels during movement-restricted housing. Movement-restricted camels showed elevated myeloperoxidase activity in their serum, a significant shape-change of their neutrophils, and higher reactive oxygen species content in their monocytes and neutrophils. The leukogram pattern of the camels under restricted housing was characterized by increased numbers of neutrophils, eosinophils, lymphocytes, and monocytes. Within the lymphocyte population, only the helper T cells and B cells were expanded in animals under restricted housing. In addition, restricted housing modulated the expression of several cell surface antigens, including monocyte-polarization markers and cell adhesion molecules. Functional analysis of bacterial phagocytosis indicated impaired antibacterial function of phagocytes in camels under restricted housing. In summary, the present study identified significant changes in blood immune cell composition, phenotype, and function in dromedary camels under restricted-housing conditions, and suggests the development of an excitement leukogram in those animals.

Abstract

Background: The dromedary camel (Camelus dromedarius) is an important livestock animal of desert and semi-desert ecosystems. In recent years, several elements of the camel immune system have been characterized. Stress and excitement induced by animal housing represent the most important environmental factors with potential modulatory effects on the immune system. The present study evaluated the impacts of a restricted-housing system on some phenotypic and functional properties of blood leukocytes in dromedary camels. Methods: Immunofluorescence and flow cytometry were used to comparatively analyze samples collected from camels during a free-ranging time and samples collected from the same camels during movement-restricted housing. Results: In comparison to blood samples collected from the camels during the free-ranging time, samples from movement-restricted camels showed elevated serum myeloperoxidase activity, a significant shape-change in their neutrophils, and higher reactive oxygen species content in their monocytes and neutrophils, indicating increased cellular oxidative stress under movement-restricted housing. The leukogram pattern of the camels under restricted housing was characterized by leukocytosis with increased numbers of neutrophils, eosinophils, lymphocytes, and monocytes, resembling an excitement leukogram pattern. Within the lymphocyte population, only the helper T cells and B cells were expanded in animals under restricted housing. The upregulation of CD163 together with the downregulation of MHC-II on monocytes from excited camels indicate a modulatory potential of animal excitement to polarize monocytes toward an anti-inflammatory phenotype. Functional analysis of bacterial phagocytosis indicates an impaired antibacterial function of phagocytes in excited camels. The downregulation of several cell adhesion molecules on leukocytes from excited camels suggests a role for impaired cell adhesion and tissue migration and leukocyte retention in blood in the observed leukocytosis in animals under excitement. Conclusions: The present study identified significant changes in blood immune cell composition, phenotype, and function in dromedary camels under restricted-housing conditions. The observed changes in leukocyte composition suggest the development of an excitement leukogram pattern in camels under movement-restricted housing. To evaluate the clinical relevance of the observed changes in immune cell phenotype and function for the immune competence of camels under restricted housing, further studies are required.

Potential Role of CD47-Directed Bispecific Antibodies in Cancer Immunotherapy

The prosperity of immunological therapy for cancer has aroused enormous passion for exploiting the novel targets of cancer immunotherapy. After the approval of blinatumomab, a bispecific antibody (bsAb) targeting on CD19 for acute lymphoblastic leukemia, a few of CD47-targeted bsAbs for cancer immunotherapy, are currently in clinical research. In our review of CD47-targeted bsAbs, we described the fundamental of bsAbs. Then, we summarized the information of four undergoing phase I researches, reviewed the main toxicities relevant to CD47-targeted bsAb immunological therapy of on-target cytotoxicity to healthy cells and a remarkable antigen-sink. Finally, we described possible mechanisms of resistance to CD47-targeted bsAb therapy. More clinical researches are supposed to adequately confirm its security and efficacy in clinical practice.

Stabilization of Endothelial Receptor Arrays by a Polarized Spectrin Cytoskeleton Facilitates Rolling and Adhesion of Leukocytes

Multivalent complexes of endothelial adhesion receptors (e.g., selectins) engage leukocytes to orchestrate their migration to inflamed tissues. Proper anchorage and sufficient density (clustering) of endothelial receptors are required for efficient leukocyte capture and rolling. We demonstrate that a polarized spectrin network dictates the stability of the endothelial cytoskeleton, which is attached to the apical membrane, at least in part, by the abundant transmembrane protein CD44. Single-particle tracking revealed that CD44 undergoes prolonged periods of immobilization as it tethers to the cytoskeleton. The CD44-spectrin "picket fence" alters the behavior of bystander molecules-notably, selectins-curtailing their mobility, inducing their apical accumulation, and favoring their clustering within caveolae. Accordingly, depletion of either spectrin or CD44 virtually eliminated leukocyte rolling and adhesion to the endothelium. Our results indicate that a unique spectrin-based apical cytoskeleton tethered to transmembrane pickets-notably, CD44-is essential for proper extravasation of leukocytes in response to inflammation.

Hyaluronan-Metal Gold Nanoparticle Hybrids for Targeted Tumor Cell Therapy

In this study, a novel multifunctional nanoplatform based on core-shell nanoparticles of spherical gold nanoparticles (AuNPs) capped with low and high molecular weight (200 and 700 kDa) hyaluronic acid (HA), was assembled via a green, one-pot redox synthesis method at room temperature. A multitechnique characterization approach by UV-visible spectroscopy, dynamic light scattering and atomic force microscopy pointed to the effective 'surface decoration' of the gold nanoparticles by HA, resulting in different grafting densities of the biopolymer chains at the surface of the metal nanoparticle, which in turn affected the physicochemical properties of the nanoparticles. Specifically, the spectral features of the gold plasmonic peak (and the related calculated optical size), the hydrodynamic diameter and the nanoparticle stability were found to depend on the molecular weight of the HA. The CD44-targeting capability of HA-functionalized gold nanoparticles was tested in terms of antibacterial activity and cytotoxicity. An enhanced inhibitory activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus was found, with a HA molecular weight (MW)-dependent trend for the HA-capped AuNPs compared to the bare, glucose-capped AuNPs. Cell viability assays performed on two CD44-positive cell models, namely normal human umbilical vein endothelial (HUVEC) and prostate tumor (PC-3) cells, in comparison with neuroblastoma cells (SH-SY5Y), which do not express the CD44 receptor, demonstrated an increased cytotoxicity in neuroblastoma compared to prostate cancer cells upon the cellular treatments by HA-AuNP compared to the bare AuNP, but a receptor-dependent perturbation effect on cytoskeleton actin and lysosomal organelles, as detected by confocal microscopy. These results highlighted the promising potentialities of the HA-decorated gold nanoparticles for selective cytotoxicity in cancer therapy. Confocal microscopy imaging of the two human tumor cell models demonstrated a membrane-confined uptake of HA-capped AuNP in the cancer cells that express CD44 receptors and the different perturbation effects related to molecular weight of HA wrapping the metallic core of the plasmonic nanoparticles on cellular organelles and membrane mobility.

Urban Particles Elevated Streptococcus pneumoniae Biofilms, Colonization of the Human Middle Ear Epithelial Cells, Mouse Nasopharynx and Transit to the Middle Ear and Lungs

Air-pollutants containing toxic particulate matters (PM) deposit in the respiratory tract and increases microbial infections. However, the mechanism by which this occurs is not well understood. This study evaluated the effect of urban particles (UP) on Streptococcus pneumoniae (pneumococcus) in vitro biofilm formation, colonization of human middle ear epithelium cells (HMEECs) as well as mouse nasal cavity and its transition to the middle ear and lungs. The in vitro biofilms and planktonic growth of S. pneumoniae were evaluated in metal ion free medium in the presence of UP. Biofilms were quantified by crystal violet (CV) microplate assay, colony forming unit (cfu) counts and resazurin staining. Biofilm structures were analyzed using a scanning electron microscope (SEM) and confocal microscopy (CM). Gene expressions of biofilms were evaluated using real time RT-PCR. Effects of UP exposure on S. pneumoniae colonization to HMEECs were evaluated using fluorescent in-situ hybridization (FISH), cell viability was detected using the Ezcyto kit, apoptosis in HMEECs were evaluated using Annexin-V/PI based cytometry analysis and reactive oxygen species (ROS) production were evaluated using the Oxiselect kit. Alteration of HMEECs gene expressions on UP exposure or pneumococci colonization was evaluated using microarray. In vivo colonization of pneumococci in the presence of UP and transition to middle ear and lungs were evaluated using an intranasal mice colonization model. The UP exposure significantly increased (*p < 0.05) pneumococcal in vitro biofilms and planktonic growth. In the presence of UP, pneumococci formed organized biofilms with a matrix, while in absence of UP bacteria were unable to form biofilms. The luxS, ply, lytA, comA, comB and ciaR genes involved in bacterial pathogenesis, biofilm formation and quorum sensing were up-regulated in pneumococci biofilms grown in the presence of UP. The HMEECs viability was significantly decreased (p < 0.05) and bacteria colonization was significantly elevated (p < 0.05) in co-treatment (UP + S. pneumoniae) when compared to single treatment. Similarly, increased apoptosis and ROS production were detected in HMEECs treated with UP + pneumococci. The microarray analysis of HMEECs revealed that the genes involve in apoptosis and cell death, inflammation, and immune response, were up-regulated in co-treatment and were unchanged or expressed in less fold in single treatments of UP or S. pneumoniae. The in vivo study showed an increased pneumococcal colonization of the nasopharynx in the presence of UP and a higher transition of bacteria to the middle ear and lungs in the presence of UP. The UP exposure elevated S. pneumoniae in vitro biofilm and colonization of HMEECs, and in vivo mouse nasopharyngeal colonization, and increased dissemination to mouse middle ear and lungs.

Panel 3: Genomics, precision medicine and targeted therapies

OBJECTIVE

To review the most recent advances in human and bacterial genomics as applied to pathogenesis and clinical management of otitis media.

DATA SOURCES

PubMed articles published since the last meeting in June 2015 up to June 2019.

REVIEW METHODS

A panel of experts in human and bacterial genomics of otitis media was formed. Each panel member reviewed the literature in their respective fields and wrote draft reviews. The reviews were shared with all panel members, and a merged draft was created. The panel met at the 20th International Symposium on Recent Advances in Otitis Media in June 2019, discussed the review and refined the content. A final draft was made, circulated, and approved by the panel members.

CONCLUSION

Trans-disciplinary approaches applying pan-omic technologies to identify human susceptibility to otitis media and to understand microbial population dynamics, patho-adaptation and virulence mechanisms are crucial to the development of novel, personalized therapeutics and prevention strategies for otitis media.

IMPLICATIONS FOR PRACTICE

In the future otitis media prevention strategies may be augmented by mucosal immunization, combination vaccines targeting multiple pathogens, and modulation of the middle ear microbiome. Both treatment and vaccination may be tailored to an individual's otitis media phenotype as defined by molecular profiles obtained by using rapidly developing techniques in microbial and host genomics.

Current Understanding of Host Genetics of Otitis Media

The pathogenesis of otitis media (OM), an inflammatory disease of the middle ear (ME), involves interplay between many different factors, including the pathogenicity of infectious pathogens, host immunological status, environmental factors, and genetic predisposition, which is known to be a key determinant of OM susceptibility. Animal models and human genetics studies have identified many genes and gene variants associated with OM susceptibility: genes that encode components of multiple signaling pathways involved in host immunity and inflammatory responses of the ME mucosa; genes involved in cellular function, such as mucociliary transport, mucin production, and mucous cell metaplasia; and genes that are essential for Eustachian tube (ET) development, ME cavitation, and homeostasis. Since our last review, several new mouse models with mutations in genes such as CCL3, IL-17A, and Nisch have been reported. Moreover, genetic variants and polymorphisms in several genes, including FNDC1, FUT2, A2ML1, TGIF1, CD44, and IL1-RA variable number tandem repeat (VNTR) allele 2, have been identified as being significantly associated with OM. In this review, we focus on the current understanding of the role of host genetics in OM, including recent discoveries and future research prospects. Further studies on the genes identified thus far and the discovery of new genes using advanced technologies such as gene editing, next generation sequencing, and genome-wide association studies, will advance our understanding of the molecular mechanism underlying the pathogenesis of OM and provide new avenues for early screening and developing effective preventative and therapeutic strategies to treat OM.