Mucosal Vaccine Delivery Systems: The Future of Immunization (Part 1) E-Book
Editors: Shaweta Sharma
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- Herausgeber: Bentham Science Publishers
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- Sprache: Englisch
Mucosal Vaccine Delivery Systems: The Future of Immunization – Part I presents a pioneering exploration into the realm of mucosal vaccination, covering innovative delivery platforms, immunological mechanisms, and their diverse applications in human and veterinary medicine. This comprehensive volume examines the regulatory, economic, and technological landscapes shaping mucosal vaccine development, highlighting their pivotal role in combating infectious diseases, chronic ailments, and advancing cancer immunotherapy. Key Features: - Detailed insights into nasal, oral, pulmonary, gastrointestinal, and urogenital vaccination. - Analysis of mucosal vaccines in pediatric and elderly healthcare. - Exploration of adjuvants, bioprocessing challenges, and commercialization trends. - Contributions from leading researchers in the field.
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Veröffentlichungsjahr: 2025
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FOREWORD
The field of immunization is undergoing a transformative shift with the advent of mucosal vaccine delivery systems. Mucosal Vaccine Delivery Systems: The Future of Immunization – Part I provides a comprehensive exploration of the latest advancements in this field, highlighting its potential to revolutionize disease prevention. This volume delves into various mucosal delivery platforms, offering insights into nasal, oral, pulmonary, gastrointestinal, and urogenital vaccinations. Special emphasis is placed on their role in pediatric immunization and addressing immunosenescence in elderly patients. By targeting mucosal surfaces, the body’s first line of defense these innovative approaches enhance immune response and improve patient compliance. As global health challenges evolve, mucosal vaccines promise to bridge existing gaps in disease prevention. This book serves as a crucial resource for researchers, clinicians, and healthcare professionals dedicated to advancing immunization strategies for a healthier future.
Preface
Mucosal vaccine delivery systems have emerged as a groundbreaking approach in immunization, offering a non-invasive and effective alternative to traditional methods. By targeting mucosal surfaces, the primary entry points for many pathogens these vaccines harness the body’s natural immune defenses to provide enhanced protection. This book, Mucosal Vaccine Delivery Systems: The Future of Immunization – Part I, explores the latest advancements, challenges, and opportunities in this rapidly evolving field.
The book covers various mucosal delivery platforms, including nasal, oral, pulmonary, and urogenital vaccines. Nasal vaccination enhances both local and systemic immunity, while oral vaccines provide a needle-free, patient-friendly alternative. Pulmonary vaccines offer inhalable solutions for respiratory diseases, and urogenital vaccination addresses sexually transmitted infections. Additionally, mucosal vaccines for gastrointestinal infections are explored, highlighting their role in combating enteric pathogens.
Special focus is given to pediatric and elderly populations. Mucosal vaccines reduce distress in children while ensuring effective immune responses. In elderly patients, they help counter immunosenescence, enhancing vaccine efficacy. As global health challenges persist, mucosal vaccination represents the future of immunization. We hope this book serves as a valuable resource, inspiring innovation and collaboration toward more accessible and efficient vaccines worldwide.
List of Contributors
Mucosal Delivery Platforms: A Comprehensive Overview
Sudhir Kumar1,*,Shekhar Sharma2,Rupali Sharma3,Alok Bhardwaj2,Koushal Dhamija2Abstract
Drug administration using mucosal delivery platforms holds great promise because of several advantages, including quick response, bypassing first-pass metabolism, and increased patient adherence. However, the effective exploitation and shaping of these avenues depend on deep knowledge of immunology principles at the mucosa. The oral, nasal, pulmonary, vaginal, rectal, and ocular mucosae are equipped with intricate defense systems executed by innate as well as adaptive immunity. This chapter explores the intersection of mucosal delivery platforms and mucosal immunity. Beginning with an introduction to mucosal delivery and its importance in drug delivery, we delve into the challenges of mucosal barriers, clearance mechanisms, and immunogenicity. It is very important to comprehend how mucosal immunity works, which includes the function of epithelial cells, dendritic cells, T cells, and innate lymphoid cells in defending the body. Furthermore, we examine common mucosal delivery platforms such as lipid-based formulations, nanoparticles, hydrogels, and microneedle patches, highlighting their applications in vaccine delivery, protein therapeutics, small molecule drugs, and gene therapy. Nanotechnology, targeted delivery systems, and immunomodulatory strategies are also being discussed. Regarding safety profiles and commercialization aspects, this chapter attempts to understand the current market scenario and prospects for mucosal delivery platforms. This overview aims to promote advances in drug delivery technologies and improve healthcare outcomes by connecting the gap between mucosal delivery and mucosal immunity.
INTRODUCTION
Drug delivery is a field that has witnessed numerous advancements in recent years. Mucosal drug delivery systems, which include different types of formulations and technologies, have emerged as one of the most promising approaches to drug administration. Such platforms are designed specifically for easier and more effective ways of getting drugs delivered through mucosal surfaces such as oral, nasal, pulmonary, vaginal, rectal, and ocular mucosa. The development of these systems came about due to growing awareness of some benefits of the mucosal route, such as enhancement in drug absorption rates, fast onset of effect, and improved patient compliance. By exploiting the porous properties of mucosae and circumventing challenges like first-pass metabolism or systemic toxicities witnessed by conventional routes of administration, new paradigms in drug delivery can be actualized through this method [1, 2].
The significance of mucosal delivery in drug administration must be emphasized. It is different from traditional methods such as oral ingestion or intravenous injection since it provides access to systemic circulation through highly vascularized and large mucosal surfaces. By so doing, absorption becomes more effective because drugs can move directly into the blood system. Besides this, there are times when a conventional route might not work at all, like in cases where drugs should be delivered to inaccessible parts of the body or on the other side of barriers such as the blood-brain barrier [3].
Mucosal delivery platforms’ efficacy depends on understanding mucosal immunity and its complicated mechanisms. Mucosal surfaces are passive pathways through which drugs are absorbed and are a dynamic territory with a complex immune system. The mucosal immune system is the first line of defense against pathogens, toxins, and any other foreign invaders and thus helps to maintain tissue homeostasis and prevent infection. Immune responses in mucosal tissues are coordinated by specialized immune cells (epithelial cells, dendritic cells, T cells, innate lymphoid cells) adapted to their unique microenvironments [4].
Besides local defense mechanisms, mucosal immunity exhibits generalized systemic effects that affect immune responses. Applying these principles of mucosal immunity can help researchers develop ways to enhance the effectiveness and safety of such delivery platforms. Incorporating mucosal immunology into drug delivery design offers enormous opportunities to develop therapeutic interventions in different medical areas, from vaccination and immunotherapy to inflammatory conditions, infectious diseases, or cancer treatment [5, 6].
CONVENTIONAL vs. NOVEL APPROACHES FOR MUCOSAL DELIVERY
Common practices involved in mucosal drug delivery are usually based on standardized procedures like oral tablets, nasal sprays, suppositories, or vaginal creams. Although well-known and considered standard practices, they come with challenges such as poor drug bioavailability, enzyme degradation, and differing absorption rates over different membranes. More so, it may not cater to specific administration and controlled release of drugs [7].
In contrast, novel mucosal delivery techniques use advanced technologies and creative formulations to overcome these shortcomings. One such approach is nanotechnology, where nanoparticles and nanocarriers are engineered to encapsulate drugs, shield them from degradation, and enhance their transport across mucosal barriers. Particular characteristics like mucoadhesion, controlled release, and targeted delivery can be designed to improve drug delivery efficiency and accuracy to mucosal tissues [8].
In addition, innovative techniques might include mucoadhesive plus permeation-enhancing formulations that enhance drug retention and absorption at mucosal surfaces. For example, mucoadhesive hydrogels stick to mucosal tissues after they are used, elongating the drug duration in the body and enhancing their absorption. Conversely, these enhancers open temporary channels that let drugs cross the mucous membrane barriers and through epithelial membranes.
In addition, novel approaches have come up via the conjugation of drugs and prodrugs that will aid in mucosal drug delivery. By developing prodrug formulations or conjugating drugs with targeting ligands, researchers can develop better drug stability, tissue specificity, and less off-target effects. This will improve therapeutic outcomes [9].
Although traditional methods of delivering drugs to mucosal membranes are restricted in their scope, novel methodologies provide a promising solution that likely includes enhanced drug bioavailability, target-specific tissues, and better patient outcomes. This innovative approach has the potential to revolutionize drug delivery paradigms and meet unaddressed health gaps across various therapeutic areas through continuous research and innovation [10].
TYPES OF MUCOSAL SURFACES
Mucosal surfaces are the moist linings that cover different cavities and organs of the body, acting as boundaries between the external environment and internal tissues. Special features that make up these regions define their anatomical and physiological nature, enabling them to perform specific roles like secretion, absorption, protection, etc. [8, 11]. The types of mucosal surfaces are summarized in Fig. (1).
Fig. (1)) Types of mucosal surfaces.Oral Mucosa
The oral mucosa, lining the mouth’s interior, is a dynamic complex interface between the body’s internal tissues and the outside environment. It consists of stratified squamous epithelium constantly subjected to different mechanical forces and temperature changes and being exposed to many substances during mastication and oral hygiene practices. This mucosal lining is important in speech, taste sensation, and initial digestive processes. The structure of the oral mucosa consists of three layers: the outermost epithelium, underlying connective tissue (lamina propria), and basement membrane, which holds the epithelium to the underlying tissues. The epithelial layer is highly specialized, with variations in thickness and cell morphology in different regions of the oral cavity, allowing for specific functions [12-14].
For example, when comparing it to the gum, the cheek’s buccal mucosa has a thicker layer of skin, making it more resistant to friction caused by chewing. Moreover, this layer is characterized by several small salivary glands that help in saliva production, which is also important for oral hygiene and digestion. Besides its structural and physiological roles, oral mucosa is also an important drug delivery site as it has abundant blood vessels and is relatively permeable than other parts of the body, making it a convenient route for drug administration such as sublingual or buccal tablets, oral films, and mucoadhesive patches. Understanding the details of oral mucosa is necessary to create effective drug delivery approaches and diagnostic facilities for treating oral diseases, targeting both local mouth afflictions and whole-body maladies [15-17].
Nasal Mucosa
The nasal mucosa is crucial for the respiratory system as it abuts with the external environment. The lining of this specialized mucus-secreting ciliated epithelium comprises alternating goblet cells, which produce mucins, and ciliated cells, which move secretions and particles to the throat for swallowing. Nasal mucosa plays various roles in respiration, such as air conditioning and filtration, humidification, and olfaction. Such uniqueness in structure and activity helps it intercept many airborne particles, allergens, and pathogens, protecting the respiratory system against invasion by them. For instance, many blood capillaries in the nasal mucosa enhance faster drug absorption when given through the nose [18, 19].
As a result, various nasal drug delivery systems have been developed, including nasal sprays, drops, and powders that exhibit advantages like immediate action onsets, avoidance of first-pass metabolism, and better patient compliance. In addition, the olfactory mucosa is richly supplied with sensory nerve endings, thus explaining its role in smell detection and elicitation of reflexes such as sneezing and congestion. Moreover, many other illnesses are associated with nasal mucosa dysfunction, including allergic rhinitis, among others; hence, one needs to understand its structure and function well for effective therapies for respiratory system illnesses and drug targeting strategies. It is essential to comprehend the nasal mucosa's anatomy, physiology, and immunology to develop efficacious treatments for respiratory diseases and optimize drug delivery to the respiratory system [20, 21].
Pulmonary Mucosa
Pulmonary mucosa is a special lining that extends from the larynx to the alveoli in the lungs. It enhances gaseous exchange and provides a barrier from air-borne microorganisms, toxins, and other debris that could be inhaled. It has a pseudostratified columnar epithelium structure with diverse cells, such as ciliated cells, goblet cells, Clara cells, and type II pneumocytes scattered about it [22, 23].
Pulmonary mucosa is primarily responsible for maintaining homeostasis in the respiratory system by humidifying, warming, and filtering air breathed in to protect delicate lung tissues from injury. Ciliated cells have several motile cilia, which always beat continuously in a coordinated manner; hence, this assists in moving mucus and particles caught within towards the upper airways for clearance, preempting them from settling into the lower respiratory tract. Goblet cells produce mucus, which entraps or carries off particulate matter pathogens and allergens on the surface of airway walls [24].
Aside from participating in mucociliary clearance, specialized cell populations contribute to lung function and immunity within the pulmonary mucosa. The bronchioles have Clara cells that make surfactant proteins and detoxify inhaled substances, which help keep the airway open and intact. Alveoli have type II pneumocytes that secrete pulmonary surfactant, which decreases surface tension and averts alveolar collapse during exhalation, thus enhancing gas exchange efficiency [25, 26].
Additionally, the pulmonary mucosa has numerous immune cells and lymphoid tissue, including macrophages, dendritic cells, and lymphocytes, which regulate immune responses against inhaled pathogens and foreign antigens. This immune system of the mucus lining is vital for protecting our respiratory system from infection, allergens, and toxins in the environment, but it also contributes to immune surveillance and tolerance [27, 28].
Pulmonary mucosa malfunction may cause different respiratory conditions, such as asthma, chronic obstructive pulmonary disease (COPD), and respiratory infections. The structure, function, and immunology of pulmonary mucosa must be understood to develop strategies for preventing and treating respiratory diseases and optimizing drug delivery for therapeutic purposes [29].
Vaginal Mucosa
A female’s vaginal canal is lined with a dynamic and complex epithelial barrier called the vaginal mucosa that plays an important role in reproductive health and immunity. The multilayered squamous epithelium of the vaginal mucosa goes through changes periodically as a result of hormonal variations within the menstrual cycle, especially estrogen and progesterone. These hormonal changes affect thickness, hydration, and composition, which are crucial to maintaining structure and function [30].
Providing lubrication and protecting the vagina canal, vaginal mucosa helps in making sexual intercourse comfortable and reduces friction-related injuries. The barrier created by the mucosa also acts against toxins, microbial pathogens, and foreign substances, stopping them from entering the female reproductive system. Furthermore, through favoring sperm transport, fertilization, and implantation of the embryo, vaginal mucosa is a key player in reproductive physiology [31, 32].
The exceptional configuration of the vaginal mucosa, which compromises glycogen-laden epithelial cells and a combination of lactobacilli-dominated microbiota, helps in the defense mechanisms and natural maintenance of acidic pH inside. Vaginal health is maintained through lactobacilli that produce lactic acids to create an acidic environment preventing the growth of pathogens. Glycogen within the vaginal epithelial cells serves as a fuel for lactobacilli, thereby allowing them to grow or colonize more on the surface, hence improving immunity within it at large scale [33, 34].
Apart from protecting and facilitating reproduction, vaginal mucosa is also referred to as a medicinal drug transfer and absorption center. Vaginal gels, creams, suppositories, and rings come in various forms to enable local or systemic administration of drugs such as contraceptives, hormone replacement therapy, etc. High vascularization, coupled with the permeability of vaginal mucosa, allows for efficient drug absorption. As such, targeted delivery and sustained release are facilitated via this route [35].
When the mucous membrane of the vagina is not functioning properly, it can lead to several gynecological disorders such as vaginal infection, inflammation and atrophy, sexual dysfunction, and infertility. Knowledge of the anatomy, physiology, and immunology of vaginal mucosa is important in promoting reproductive health among women, preventing gynecological disorders, and developing viable strategies for drug delivery and therapeutics [36].
Rectal Mucosa
The specialized epithelial barrier that lines the inner surface of the rectum is called rectal mucosa, and it plays a significant role in gastrointestinal physiology and immunity. The absorption of water, electrolytes, and nutrients and the elimination of waste products during defecation are some of the functions performed by rectal mucosa with a columnar epithelium containing numerous microvilli. Structurally, rectal mucosa is highly vascularized and contains abundant lymphoid tissue, such as Peyer’s patches and solitary lymphoid follicles; these elements contribute to immune surveillance and pathogen killing [37, 38].
A continuous layer of rectal mucosa is created to avoid stool leakage from the back passage. For these functions, the anal canal contains structures called anal sphincters that are made up of smooth and striped muscle fibers which coordinate relaxation and contraction to help in defecation and maintain continence at rest. Moreover, many goblet cells in the rectal mucosa produce mucus to lubricate the rectum's surface and facilitate fecal movement [39, 40].
Another role of rectal mucosa is a drug absorption and administration site, especially for medicines with either local or systemic effects. By bypassing first-pass metabolism, rectal drug delivery has several benefits, such as faster action and better patient adherence. Other formulations like rectal suppositories, enemas, and foams may be used to manage gastrointestinal diseases such as inflammatory bowel disease, hemorrhoids, and anal infections [41].
The rectal mucosae’s immune system is crucial for infection prevention and intestinal homeostasis. For example, lymphoid aggregates and follicles are distributed across the rectal mucosa as part of Mucosal-associated lymphoid tissue (MALT), which acts as a major site for sampling antigens, activating immune cells, and producing antibodies. Still, local immunocompetent cells like macrophages, dendritic cells, and T-lymphocytes participate in immune surveillance of the rectal lumen against pathogens, toxins, or foreign antigens [42, 43].
Rectal mucosa is prone to dysfunction, leading to various gastrointestinal conditions like inflammatory bowel disease, infectious colitis, and rectal prolapse. Understanding the anatomy, physiology, and immunology of the rectal mucosa is crucial for diagnosing and treating gastrointestinal diseases, optimizing drug delivery, and maintaining intestinal health and function [44].
Ocular Mucosa
In the eye, the ocular mucosa consists of the cornea and conjunctiva, essential for their protective mechanism and overall well-being. The conjunctiva is a very thin sheet covering the eyelids from the inside and the sclera on the outer side. It is rich in blood supply and has secretory cells producing mucus and tears. The hydrated tear fluid, which lubricates the eye, prevents it from drying out, and cleanses dirt, comprises two layers. This mucous layer is secreted by epithelial cells in the conjunctiva in addition to an aqueous section produced by lacrimal glands [45, 46].
The eye is the front of an eyeball and globe, transparent, and described as domelike. It consists of layers of flat epithelial cells arranged stratified, as well as the stroma and endothelium. This part helps bend light rays onto the retina during the vision process. Stem cells located at the limbus constantly replace the surface layer of corneal epithelium with new ones to maintain transparency and ocular integrity. Also, this component contains specialized cells, such as goblet cells, that synthesize mucins responsible for coherence and wetting function on a certain membrane’s cover called tear film [47, 48].
Airborne particles, microbial pathogens, and allergens are among the environmental dangers ocular mucosa guards against as a barrier. The tear film is composed of multiple antimicrobial molecules, such as lysozyme, lactoferrin, and immunoglobulins, that can help kill off or otherwise dispose of the organisms found on the surface of the eye. Besides, there is an accumulation of immune cells within the conjunctiva, including lymphocytes, dendritic cells, and macrophages, which play a role in immune surveillance and response to infections [49, 50].
Disorders of the eye, for example, dry eye symptoms, conjunctivitis, and corneal infections, may be caused by the malfunctioning of the ocular mucosa. Knowledge about the ocular surface's structure, function, and defense mechanisms is important to recognize these diseases, their treatment, and strategies aimed at preserving ocular integrity and visual functions. Moreover, it can take part in the delivery of drugs to the eye with different preparations such as eye drops, ointments, or inserts used to treat various eye disorders. This knowledge of the mucous layer covering the eyes' outer part could help us develop new ways to deliver drugs more effectively, thus improving therapeutic outcomes among patients with different conditions affecting the eyes [51-53].
ADVANTAGES OF MUCOSAL DELIVERY
Mucosal drug delivery has many advantages over traditional routes of drug administration, making it an appealing option for pharmaceuticals, vaccines, and other therapeutic agents. The advantages of mucosal delivery are shown in Fig. (2) and described below.
It is attractive to administer drugs via the mucosa in several therapeutic fields due to its numerous advantages. Its most important benefit is that the nature of mucosal surfaces is highly vascularized, which means that drugs can be absorbed into the blood rapidly. This detail makes mucosal administration appropriate for medications needing immediate effects as it causes a faster onset than oral or transdermal methods. Additionally, there is no “first-pass effect” and liver bypassing about drug delivery through this route, thus enhancing the bioavailability and efficiency of drugs [54].
Besides, this makes it more pleasant and easy for patients than injections or surgical interventions because it uses the non-invasive method. Patients who are required to go through long-term treatment can be encouraged through the lack of invasive procedures such as needles. The ease of use and less pain associated with some mucosal delivery modes like oral films, nasal sprays, or vaginal gels usually lead to increased compliance that, in turn, improves overall satisfaction among patients [55, 56].
Fig. (2)) Advantages of mucosal delivery.In addition, mucosal delivery facilitates the targeting of drugs to particular mucosal surfaces like the respiratory canal, gastrointestinal tract, and genitalia mucosa so that they can be effective locally. The method reduces general side effects related to systemic circulation and enhances drug effectiveness, which is especially important for treating diseases involving the mucus membranes. Mucosal surfaces are also rich in immune cells and associated lymphoid tissue, making them ideal sites for vaccine delivery. They can produce a strong immune response both at the mucosal layer and systemically, thus protecting against mucous pathogens and enhancing immunity in general [57].
Another advantage of mucosal delivery is its flexibility in accommodating a broad spectrum of drugs, encompassing small molecules, peptides, proteins, vaccines, and nucleic acids. It permits the customization of formulations and delivery devices for particular therapeutic purposes, thereby enabling drug delivery to be individualized. Furthermore, this versatility includes various routes of administration, which can be chosen based on factors such as patient preference, pharmacokinetics, and disease characteristics [58].
There are various benefits of mucosal delivery, which include rapidity of action, convenience, targeted therapy, immunoregulatory effects, and flexibility in drug administration systems. Because of this, the process has gained a lot of interest as it can be applied in several medical situations to improve patient outcomes. As research continues to evolve, enhanced innovation and optimization for drugs delivered via mucus will provide more benefits for patients and healthcare providers [59].
MECHANISMS OF MUCOSAL IMMUNITY
Innate Immune Responses at Mucosal Surfaces
Mucosal surfaces are constantly exposed to a variety of microorganisms, antigens, and environmental factors that require strong immune systems that help sustain homeostasis and guard against pathogens. Innate immune responses at the mucosal surfaces are important in starting the host defense mechanisms when they come across invading pathogens. These responses are known for their fast, non-specific response to microbial components, which elicit activation of different immune cells and signaling pathways for an immediate defense [60].
The mucosal epithelial barrier is one of the main constituents of innate immunity at mucosal surfaces. This acts as a first line of defense against pathogens. This happens to be the mucosal epithelial cells, which are one or more layers thick, that defend the underlying tissues from being invaded by organisms and toxins. In addition to these barriers, secretions such as antimicrobial peptides, mucus, and other substances with antimicrobial properties are produced by cells lining the mucosa, all intended to hinder microbial growth while deactivating disease-causing agents.
An additional important component of the innate immune response at mucosal layers is the mucosal-associated lymphoid tissue (MALT) that consists of structured lymphoid organs like tonsils in the respiratory system and Peyer’s patches in the intestines. MALT has specialized immune cells, including macrophages, dendritic cells, and innate lymphoid cells for recognizing and reacting against pathogens invasion. At mucosal surfaces, especially, antigens are captured by dendritic cells to induce adaptive immunity through subsequent presentation to immune cells [61].
Mucous membrane protection may also involve natural defenders such as macrophages and neutrophils, which prey on pathogens via phagocytosis. These cells release cytokines and other inflammatory mediators that initiate inflammation to attract more immune cells to the infection site. Furthermore, innate lymphoid cells (ILCs) secrete cytokines that control mucosal swelling and tissue rehabilitation to keep up normalcy.
The first defense against pathogens at mucosal surfaces is usually innate immune responses that provide rapid and non-specific protection while boosting adaptive immunity. Innate immunity has a pivotal role in determining the overall immune response of mucosal surfaces and maintaining host-microbe interactions through the activation of immune cells, secretion of antimicrobial factors, and promotion of inflammation. In order to develop strategies for modulating mucosal infections and inflammatory diseases, it is important to understand the mechanisms underlying innate immunity at these surfaces [62].
Adaptive Immune Responses in Mucosal Tissues
Adaptive immune responses in mucosal tissues are critical for maintaining long-term immunity and tolerance to diverse antigens encountered on mucosal surfaces. These MALT-driven immunoresponses entail a coordinated interaction among immune cells and signaling pathways that effectively counter pathogenic agents while tolerating commensal microbes or harmless antigens [63].
