Immune responses to pertussis antigens in infants and toddlers after immunization with multicomponent acellular pertussis vaccine

Novel adjuvants in allergen-specific immunotherapy: where do we stand?

Type I hypersensitivity, or so-called type I allergy, is caused by Th2-mediated immune responses directed against otherwise harmless environmental antigens. Currently, allergen-specific immunotherapy (AIT) is the only disease-modifying treatment with the potential to re-establish clinical tolerance towards the corresponding allergen(s). However, conventional AIT has certain drawbacks, including long treatment durations, the risk of inducing allergic side effects, and the fact that allergens by themselves have a rather low immunogenicity. To improve AIT, adjuvants can be a powerful tool not only to increase the immunogenicity of co-applied allergens but also to induce the desired immune activation, such as promoting allergen-specific Th1- or regulatory responses. This review summarizes the knowledge on adjuvants currently approved for use in human AIT: aluminum hydroxide, calcium phosphate, microcrystalline tyrosine, and MPLA, as well as novel adjuvants that have been studied in recent years: oil-in-water emulsions, virus-like particles, viral components, carbohydrate-based adjuvants (QS-21, glucans, and mannan) and TLR-ligands (flagellin and CpG-ODN). The investigated adjuvants show distinct properties, such as prolonging allergen release at the injection site, inducing allergen-specific IgG production while also reducing IgE levels, as well as promoting differentiation and activation of different immune cells. In the future, better understanding of the immunological mechanisms underlying the effects of these adjuvants in clinical settings may help us to improve AIT.

Aluminum Adjuvants-'Back to the Future'

Aluminum-based adjuvants will continue to be a key component of currently approved and next generation vaccines, including important combination vaccines. The widespread use of aluminum adjuvants is due to their excellent safety profile, which has been established through the use of hundreds of millions of doses in humans over many years. In addition, they are inexpensive, readily available, and are well known and generally accepted by regulatory agencies. Moreover, they offer a very flexible platform, to which many vaccine components can be adsorbed, enabling the preparation of liquid formulations, which typically have a long shelf life under refrigerated conditions. Nevertheless, despite their extensive use, they are perceived as relatively 'weak' vaccine adjuvants. Hence, there have been many attempts to improve their performance, which typically involves co-delivery of immune potentiators, including Toll-like receptor (TLR) agonists. This approach has allowed for the development of improved aluminum adjuvants for inclusion in licensed vaccines against HPV, HBV, and COVID-19, with others likely to follow. This review summarizes the various aluminum salts that are used in vaccines and highlights how they are prepared. We focus on the analytical challenges that remain to allowing the creation of well-characterized formulations, particularly those involving multiple antigens. In addition, we highlight how aluminum is being used to create the next generation of improved adjuvants through the adsorption and delivery of various TLR agonists.

Nanoalum adjuvanted vaccines: small details make a big difference

Purified vaccine antigens offer important safety and reactogenicity advantages compared with live attenuated or whole killed virus and bacterial vaccines. However, they require the addition of adjuvants to induce the magnitude, duration and quality of immune response required to achieve protective immunity. Aluminium salts have been used as adjuvants in vaccines for almost a century. In the literature, they are often referred to as aluminium-based adjuvants (ABAs), or aluminium salt-containing adjuvants or more simply "alum". All these terms are used to group aluminium suspensions that are very different in terms of atomic composition, size, and shape. They differ also in stability, antigen-adsorption, and antigen-release kinetics. Critically, these parameters also have a profound effect on the character and magnitude of the immune response elicited. Recent findings suggest that, by reducing the size of aluminium from micro to nanometers, a more effective adjuvant is obtained, together with the ability to sterile filter the vaccine product. However, the behaviour of aluminium nanoparticles in vaccine formulations is different from microparticles, requiring specific formulation strategies, as well as a more detailed understanding of how formulation influences the immune response generated. Here we review the current state of art of aluminium nanoparticles as adjuvants, with a focus on their immunobiology, preparation methods, formulation optimisation and stabilisation.

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.

Increasing FIM2/3 antigen-content improves efficacy of Bordetella pertussis vaccines in mice in vivo without altering vaccine-induced human reactogenicity biomarkers in vitro

Current acellular-pertussis (aP) vaccines appear inadequate for long-term pertussis control because of short-lived efficacy and the increasing prevalence of pertactin-negative isolates which may negatively impact vaccine efficacy. In this study, we added fimbriae (FIM)2 and FIM3 protein to licensed 2-, 3- or 5-component aP vaccines (Pentavac®, Boostrix®, Adacel®, respectively) to assess whether an aP vaccine with enhanced FIM content demonstrates enhanced efficacy. Vaccine-induced protection was assessed in an intranasal mouse challenge model. In addition, potential reactogenicity was measured by biomarkers in a human whole blood assay (WBA) in vitro and benchmarked the responses against licensed whole cell pertussis (wP) and aP vaccines including Easyfive®, Pentavac® and Pentacel®. The results show that commercial vaccines demonstrated reduced efficacy against pertactin-negative versus pertactin-positive strains. However, addition of higher amounts of FIM2/3 to aP vaccines reduced lung colonization and increased vaccine efficacy against a pertactin-negative strain in a dose-dependent manner. Improvements in efficacy were similar for FIM2 and FIM3-expressing strains. Increasing the amount of FIM2/3 proteins in aP formulations did not alter vaccine-induced biomarkers of potential reactogenicity including prostaglandin E₂, cytokines and chemokines in human newborn cord and adult peripheral blood tested in vitro. These results suggest that increasing the quantity of FIM proteins in current pertussis vaccine formulations may further enhance vaccine efficacy against B. pertussis infection without increasing the reactogenicity of the vaccine.

Development and validation of a robust multiplex serological assay to quantify antibodies specific to pertussis antigens

Despite wide spread vaccination, the public health burden of pertussis remains substantial. Current acellular pertussis vaccines comprise upto five Bordetella pertussis (Bp) antigens. Performing an ELISA to quantify antibody for each antigen is laborious and challenging to apply to pediatric samples where serum volume may be limited. We developed a microsphere based multiplex antibody capture assay (MMACA) to quantify antibodies to five pertussis antigens; pertussis toxin, pertactin, filamentous hemagglutinin and fimbrial antigens 2/3, and adenylate cyclase toxin in a single reaction (5-plex) with a calibrated reference standard, QC reagents and SAS^® based data analysis program. The goodness of fit (R²) of the standard curves for five analytes was ≥0.99, LLOQ 0.04-0.15 IU or AU/mL, accuracy 1.9%-23.8% (%E), dilutional linearity slopes 0.93-1.02 and regression coefficients r² = 0.91-0.99. MMACA had acceptable precision within a median CV of 16.0%-22.8%. Critical reagents, antigen conjugated microsphere and reporter antibody exhibited acceptable (<12.3%) lot-lot variation. MMACA can be completed in <3 h, requires low serum volume (5μL/multiplex assay) and has fast data turnaround time (<1 min). MMACA has been successfully developed and validated as a sensitive, specific, robust and rugged method suitable for simultaneous quantification of anti-Bp antibodies in serum, plasma and DBS.

Emerging Topics in Vaccine Therapeutics for Adolescents and Adults: An Update for Immunizing Pharmacists

Vaccine therapeutics and the practice of immunization provision are ever-changing. As pharmacy-based immunization services continue to flourish in the United States, more and more patients are requesting both routine and travel vaccines in community pharmacies. However, vaccine recommendations from the Centers for Disease Control and Prevention/Advisory Committee on Immunization Practices (CDC/ACIP) can sometimes differ from product-specific US Food and Drug Administration (FDA)-indicated uses. In addition, changes in vaccine schedules, product availability, and disease outbreaks can present immunizing pharmacists with scenarios requiring a high level of clinical judgment. Thus, it is of paramount importance that all immunizing pharmacists maintain competency in the most recent evidence in vaccine therapeutics, as well as practice standards for vaccine provision and administration. This review provides an update of the most recent literature surrounding emerging topics in adolescent and adult immunizations—highlighting influential studies and recent developments in the prevention of herpes zoster, human papillomavirus (HPV), measles, mumps, rubella (MMR), meningococcal disease, tetanus, diphtheria, and pertussis. Key concepts discussed include the emergence of the new recombinant zoster vaccine (RZV), meningococcal vaccine product selection, MMR revaccination during disease outbreaks, tetanus vaccine product selection, and duration of pertussis immunity with vaccination.

Immunological considerations regarding parental concerns on pediatric immunizations

Despite the fundamental role of vaccines in the decline of infant mortality, parents may decide to decline vaccination for their own children. Many factors may influence this decision, such as the belief that the infant immune system is weakened by vaccines, and concerns have been raised about the number of vaccines and the early age at which they are administered. Studies focused on the infant immune system and its reaction to immunizations, summarized in this review, show that vaccines can overcome those suboptimal features of infant immune system that render them more at risk of infections and of their severe manifestations. In addition, many vaccines have been shown to improve heterologous innate and adaptive immunity resulting in lower mortality rates for fully vaccinated children. Thus, multiple vaccinations are necessary and not dangerous, as infants can respond to several antigens as well as when responding to single stimuli. Current immunization schedules have been developed and tested to avoid vaccine interference, improve benefits and reduce side effects compared to single administrations. The infant immune system is therefore capable, early after birth, of managing several antigenic challenges and exploits them to prompt its development.

Biofilm forming potential and antimicrobial susceptibility of newly emerged Western Australian Bordetella pertussis clinical isolates

Whooping cough caused by Bordetella pertussis is increasing in several countries despite high vaccine coverage. One potential reason for the resurgence is the emergence of genetic variants of the bacterium. Biofilm formation has recently been associated with the pathogenesis of B. pertussis. Biofilm formation of 21 Western Australian B. pertussis clinical isolates was investigated. All isolates formed thicker biofilms than the reference vaccine strain Tohama I while retaining susceptibility to ampicillin, erythromycin, azithromycin and streptomycin. When two biofilm-forming clinical isolates were compared with Tohama I, minimum bactericidal concentrations of antimicrobial agents increased. Isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic analysis revealed significant differences in protein expression in B. pertussis biofilms, providing an opportunity for identification of novel biofilm-associated antigens for incorporation in current pertussis vaccines to improve their protective efficacy. The study also highlights the importance of determining antibiograms for biofilms to formulate improved antimicrobial therapeutic regimens.