The Path to New Pediatric Vaccines against Pertussis

Leading Paediatric Infectious Diseases-Current Trends, Gaps, and Future Prospects in Oral Pharmacotherapeutic Interventions

Paediatric infectious diseases contribute significantly to global health challenges. Conventional therapeutic interventions are not always suitable for children, as they are regularly accompanied with long-standing disadvantages that negatively impact efficacy, thus necessitating the need for effective and child-friendly pharmacotherapeutic interventions. Recent advancements in drug delivery technologies, particularly oral formulations, have shown tremendous progress in enhancing the effectiveness of paediatric medicines. Generally, these delivery methods target, and address challenges associated with palatability, dosing accuracy, stability, bioavailability, patient compliance, and caregiver convenience, which are important factors that can influence successful treatment outcomes in children. Some of the emerging trends include moving away from creating liquid delivery systems to developing oral solid formulations, with the most explored being orodispersible tablets, multiparticulate dosage forms using film-coating technologies, and chewable drug products. Other ongoing innovations include gastro-retentive, 3D-printed, nipple-shield, milk-based, and nanoparticulate (e.g., lipid-, polymeric-based templates) drug delivery systems, possessing the potential to improve therapeutic effectiveness, age appropriateness, pharmacokinetics, and safety profiles as they relate to the paediatric population. This manuscript therefore highlights the evolving landscape of oral pharmacotherapeutic interventions for leading paediatric infectious diseases, crediting the role of innovative drug delivery technologies. By focusing on the current trends, pointing out gaps, and identifying future possibilities, this review aims to contribute towards ongoing efforts directed at improving paediatric health outcomes associated with the management of these infectious ailments through accessible and efficacious drug treatments.

The effectiveness of PCR-RT method for etiological diagnosis of atypical forms of whooping cough

The aim of the study was to evaluate the effectiveness of the PCR-RТ method using the PCR-RТ-IS test system for the etiological diagnosis of whooping cough in the examination of patients with infectious respiratory pathology with prolonged cough and in contact persons. 113 children aged from 1 month to 17 years, 11 months and 29 days, and 146 contact family members were examined. Regardless of the initial diagnosis, all children were examined for whooping cough by bacteriological, molecular genetic and serological methods. For molecular genetic diagnostics a commercial kit and PCR-RT-IS test-system developed at the Gamaleya Research Center were used. The contact persons were examined by the bacteriological method and using the PCR-RT-IS test-system. During the initial examination the diagnoses «Acute respiratory viral infectious», «Acute rhinopharyngitis», «Acute laryngotracheitis», «Acute bronchitis», «Pneumonia» were established. The severity of cough in contact persons was different – from a typical spastic «whooping cough» to complete absence of cough. By using the PCR-RT-IS test-system we developed, the DNA of pertussis pathogen was detected in groups of patients with «Acute rhinopharyngitis» in 34.4% of cases, «Acute laryngotracheitis» – in 64.3%, «Acute bronchitis» – in 69%, with a diagnosis of «Pneumonia» – in 33.3% of cases. In a number of cases combined course of whooping cough with respiratory infections (respiratory syncytial virus, rhinovirus and others) was detected. In the examined contact persons the causative agent of pertussis was detected using the PCR-RT-IS test-system in 51,4% of cases.

Protecting the Offspring, the Gift of Maternal Immunization: Current Status and Future Perspectives

Pregnancy is characterized by immunological alterations in pregnant women that permit the growth of a semi-allogenic fetus, resulting in greater susceptibility of childbearing women to infections. Furthermore, due to the immaturity of the immune system of neonates, a protection gap is present in early life, leaving neonates and infants vulnerable to infectious diseases with increased morbidity and mortality. Maternal immunization against influenza, pertussis, and, in the context of the COVID-19 pandemic, SARS-CoV-2 has been implemented in several countries, with beneficial effects on both the mother and the offspring. The main protective mechanism of vaccination during pregnancy is transplacental transfer of maternal antibodies. However, recent evidence has implied that the fetal immune system may be influenced beyond passive immunity. This review sheds light on the current status of the routinely administered vaccinations during pregnancy, focusing on the impact of maternal immunization on the priming of the fetal immune system and suggesting future perspectives for the optimization of vaccination strategies.

Novel Strategies to Inhibit Pertussis Toxin

Pertussis, also known as whooping cough, is a respiratory disease caused by infection with Bordetella pertussis, which releases several virulence factors, including the AB-type pertussis toxin (PT). The characteristic symptom is severe, long-lasting paroxysmal coughing. Especially in newborns and infants, pertussis symptoms, such as leukocytosis, can become life-threatening. Despite an available vaccination, increasing case numbers have been reported worldwide, including Western countries such as Germany and the USA. Antibiotic treatment is available and important to prevent further transmission. However, antibiotics only reduce symptoms if administered in early stages, which rarely occurs due to a late diagnosis. Thus, no causative treatments against symptoms of whooping cough are currently available. The AB-type protein toxin PT is a main virulence factor and consists of a binding subunit that facilitates transport of an enzyme subunit into the cytosol of target cells. There, the enzyme subunit ADP-ribosylates inhibitory α-subunits of G-protein coupled receptors resulting in disturbed cAMP signaling. As an important virulence factor associated with severe symptoms, such as leukocytosis, and poor outcomes, PT represents an attractive drug target to develop novel therapeutic strategies. In this review, chaperone inhibitors, human peptides, small molecule inhibitors, and humanized antibodies are discussed as novel strategies to inhibit PT.

Bbvac: A Live Vaccine Candidate That Provides Long-Lasting Anamnestic and Th17-Mediated Immunity against the Three Classical Bordetella spp

Acute pathogens such as Bordetella pertussis can cause severe disease but are ultimately cleared by the immune response. This has led to the accepted paradigm that convalescent immunity is optimal and therefore broadly accepted as the “gold standard” against which vaccine candidates should be compared. However, successful pathogens like B. pertussis have evolved multiple mechanisms for suppressing and evading host immunity, raising the possibility that disruption of these mechanisms could result in substantially stronger or better immunity. Current acellular B. pertussis vaccines, delivered in a 5-dose regimen, induce only short-term immunity against disease and even less against colonization and transmission. Importantly, they provide modest protection against other Bordetella species that cause substantial human disease. A universal vaccine that protects against the three classical Bordetella spp. could decrease the burden of whooping cough-like disease in humans and other animals. Our recent work demonstrated that Bordetella spp. suppress host inflammatory responses and that disrupting the regulation of immunosuppressive mechanisms can allow the host to generate substantially stronger sterilizing immunity against the three classical Bordetella spp. Here, we identify immune parameters impacted by Bordetella species immunomodulation, including the generation of robust Th17 and B cell memory responses. Disrupting immunomodulation augmented the immune response, providing strong protection against the prototypes of all three classical Bordetella spp. as well as recent clinical isolates. Importantly, the protection in mice lasted for at least 15 months and was associated with recruitment of high numbers of B and T cells in the lungs as well as enhanced Th17 mucosal responses and persistently high titers of antibodies. These findings demonstrate that disrupting bacterial immunomodulatory pathways can generate much stronger and more protective immune responses to infection, with important implications for the development of better vaccines.

IMPORTANCE Infectious diseases are a major cause of morbidity and mortality in the United States, accounting for over 40 million hospitalizations since 1998. Therefore, novel vaccine strategies are imperative, which can be improved with a better understanding of the mechanisms that bacteria utilize to suppress host immunity, a key mechanism for establishing colonization. Bordetella spp., the causative agents of whooping cough, suppress host immunity, which allows for persistent colonization. We discovered a regulator of a bacterial immunosuppressive pathway, which, when mutated in Bordetella spp., allows for rapid clearance of infection and subsequent generation of protective immunity for at least 15 months. After infection with the mutant strain, mice exhibited sterilizing immunity against the three classical Bordetella spp., suggesting that the immune response can be both stronger and cross-protective. This work presents a strategy for vaccine development that can be applied to other immunomodulatory pathogens.

Non-primate animal models for pertussis: back to the drawing board?

Abstract

Despite considerable progress in the understanding of clinical pertussis, the contemporary emergence of antimicrobial resistance for Bordetella pertussis and an evolution of concerns with acellular component vaccination have both sparked a renewed interest. Although simian models of infection best correlate with the observed attributes of human infection, several animal models have been used for decades and have positively contributed in many ways to the related science. Nevertheless, there is yet the lack of a reliable small animal model system that mimics the combination of infection genesis, variable upper and lower respiratory infection, systemic effects, infection resolution, and vaccine responses. This narrative review examines the history and attributes of non-primate animal models for pertussis and places context with the current use and needs. Emerging from the latter is the necessity for further such study to better create the optimal model of infection and vaccination with use of current molecular tools and a broader range of animal systems.

Key points

• Currently used and past non-primate animal models of B. pertussis infection often have unique and focused applications.

• A non-primate animal model that consistently mimics human pertussis for the majority of key infection characteristics is lacking.

• There remains ample opportunity for an improved non-primate animal model of pertussis with the use of current molecular biology tools and with further exploration of species not previously considered.

Graphical abstract

Pertussis in Poland in 2020

INTRODUCTION

The epidemiological situation of infectious diseases in Poland in 2020, including pertussis cases, was significantly influenced by the limitation of interpersonal contacts introduced to reduce the transmission of SARS-CoV-2 virus. There was a reduction by more than half in the number of recorded pertussis cases, from 1,629 in 2019 to 753 in 2020. Pertussis is most dangerous for young children, however, it can get sick at any age, and the disease does not leave permanent immunity. Severe pertussis can also develop in the elderly, which may increase the risk of mortality. Adults usually have pertussis is mildly symptomatic and constitute an important reservoir of B. pertussis. The most effective strategy for the prevention of pertussis is still immunization of children in accordance with the Protective Vaccination Program, and in the case of adults, vaccination with the pertussis component in acellular form, repeated regularly every 10 years.

OBJECTIVES

The aim of the study was to assess the epidemiological situation of pertussis in Poland in 2020 compared to the situation in previous years, with particular emphasis on the assessment of the vaccination status of children against pertussis.

MATERIAL AND METHODS

The assessment of the epidemiological situation of pertussis in Poland was performed on the basis of the results of the analysis of unit reports of pertussis registered in the NIPH NIH - NRI in the EpiBaza system and data from the annual bulletin "Infectious diseases and poisonings in Poland in 2020" and the bulletin "Vaccinations in Poland in 2020".

RESULTS

In 2020, 753 cases of pertussis were registered. The incidence was 1.96 per 100,000 population and was lower compared to the incidence in 2019 (4.24). The highest incidence of pertussis occurred in the age group 0-4 years (9.9), and high in children and adolescents aged 5-9 years (5.1) and 10-14 years (6.0 per 100,000 population). About half of the cases concerned people over 15 years of age. In general, a higher incidence of women was observed than that of men, as well as a greater number of cases in cities than in rural areas. In 2020, among people suffering from pertussis, 206 people (i.e. 27%) required hospitalization. In 2020, one fatal case of the disease was reported to the epidemiological surveillance system.

SUMMARY AND CONCLUSIONS

In Poland, in 2020, there was a decrease in the number of pertussis cases by more than a half compared to the previous year. Despite the decline in disease rates, pertussis remains a public health problem as immunization-induced immunity is not sustained throughout life. Increasing the number of people susceptible to pertussis may lead to compensatory epidemics in the future, therefore the highest possible level of vaccination of the population, >92-94%, should be maintained to prevent new cases of pertussis.

Special Issue "Immune Ontogeny and Vaccination in Early Life: How the Non-Human Primate Model Can Help Expand the Current Knowledge in Pediatric Immunology and Infectious Diseases Research"

The development of the immune system requires a number of changes that occur during the first months of life [...].

Vaccine-Induced Cellular Immunity against Bordetella pertussis: Harnessing Lessons from Animal and Human Studies to Improve Design and Testing of Novel Pertussis Vaccines

Pertussis ('whooping cough') is a severe respiratory tract infection that primarily affects young children and unimmunised infants. Despite widespread vaccine coverage, it remains one of the least well-controlled vaccine-preventable diseases, with a recent resurgence even in highly vaccinated populations. Although the exact underlying reasons are still not clear, emerging evidence suggests that a key factor is the replacement of the whole-cell (wP) by the acellular pertussis (aP) vaccine, which is less reactogenic but may induce suboptimal and waning immunity. Differences between vaccines are hypothesised to be cell-mediated, with polarisation of Th1/Th2/Th17 responses determined by the composition of the pertussis vaccine given in infancy. Moreover, aP vaccines elicit strong antibody responses but fail to protect against nasal colonisation and/or transmission, in animal models, thereby potentially leading to inadequate herd immunity. Our review summarises current knowledge on vaccine-induced cellular immune responses, based on mucosal and systemic data collected within experimental animal and human vaccine studies. In addition, we describe key factors that may influence cell-mediated immunity and how antigen-specific responses are measured quantitatively and qualitatively, at both cellular and molecular levels. Finally, we discuss how we can harness this emerging knowledge and novel tools to inform the design and testing of the next generation of improved infant pertussis vaccines.