Immunization with PCEP microparticles containing pertussis toxoid, CpG ODN and a synthetic innate defense regulator peptide induces protective immunity against pertussis

Novel approaches to reactivate pertussis immunity

INTRODUCTION

Whole cell and acellular pertussis vaccines have been very effective in decreasing the deaths of neonates and infants from Bordetella pertussis. Despite high vaccine coverage worldwide, pertussis remains one of the most common vaccine-preventable diseases, thus suggesting that new pertussis vaccination strategies are needed. Several candidates are currently under development, such as acellular pertussis vaccines that use genetically detoxified pertussis toxin, acellular pertussis vaccines delivered with new adjuvants or new delivery systems, or an intranasally delivered, live attenuated vaccine.

AREAS COVERED

This review discusses the different possibilities for improving current pertussis vaccines and the present state of knowledge on the pertussis vaccine candidates under development.

EXPERT OPINION

Until there is a safe, effective, and affordable alternative to the two types of existing vaccines, we should maintain sufficient childhood coverage and increase the vaccination of pregnant women, adolescents, and young adults.

Controlled Human Infection Models To Accelerate Vaccine Development

The timelines for developing vaccines against infectious diseases are lengthy, and often vaccines that reach the stage of large phase 3 field trials fail to provide the desired level of protective efficacy. The application of controlled human challenge models of infection and disease at the appropriate stages of development could accelerate development of candidate vaccines and, in fact, has done so successfully in some limited cases. Human challenge models could potentially be used to gather critical information on pathogenesis, inform strain selection for vaccines, explore cross-protective immunity, identify immune correlates of protection and mechanisms of protection induced by infection or evoked by candidate vaccines, guide decisions on appropriate trial endpoints, and evaluate vaccine efficacy. We prepared this report to motivate fellow scientists to exploit the potential capacity of controlled human challenge experiments to advance vaccine development. In this review, we considered available challenge models for 17 infectious diseases in the context of the public health importance of each disease, the diversity and pathogenesis of the causative organisms, the vaccine candidates under development, and each model's capacity to evaluate them and identify correlates of protective immunity. Our broad assessment indicated that human challenge models have not yet reached their full potential to support the development of vaccines against infectious diseases. On the basis of our review, however, we believe that describing an ideal challenge model is possible, as is further developing existing and future challenge models.

Assessing the In Vivo Effectiveness of Cationic Lipid Nanoparticles with a Triple Adjuvant for Intranasal Vaccination against the Respiratory Pathogen Bordetella pertussis

Continuous outbreaks of pertussis around the world suggest inadequate immune protection in infants and weakened immune responses induced over time by the acellular pertussis vaccine. Vaccine adjuvants provide a means to improve vaccine immunogenicity and support long-term adaptive immunity against pertussis. An acellular pertussis vaccine was prepared with pertactin, pertussis toxin, and fimbriae 2/3 antigens combined with a triple-adjuvant system consisting of innate defense regulator peptide IDR 1002, a Toll-like receptor-3 agonist poly(I:C), and a polyphosphazene in a fixed combination. The vaccine was delivered intranasally in a cationic lipid nanoparticle formulation fabricated by simple admixture and two schema for addition of antigens (LT-A, antigens associated outside of L-TriAdj, and LAT, antigens associated inside of L-TriAdj) to optimize particle size and cationic surface charge. In the former, antigens were associated with the lipidic formulation of the triple adjuvant by electrostatic attraction. In the latter, the antigens resided in the interior of the lipid nanoparticle. Two dose levels of antigens were used with adjuvant comprised of the triple adjuvant with or without the lipid nanoparticle carrier. Formulation of vaccines with the triple adjuvant stimulated systemic and mucosal immune responses. The lipid nanoparticle vaccines favored a Th1 type of response with higher IgG2a and IgA serum antibody titers particularly for pertussis toxin and pertactin formulated at the 5 μg dose level in the admixed formulation. Additionally, the lipid nanoparticle vaccines resulted in high nasal SIgA antibodies and an early (4 weeks post vaccination) response after a single vaccination dose. The LT-A nanoparticles trended toward higher titers of serum antibodies compared to LAT. The cationic lipid-based vaccine nanoparticles formulated with a triple adjuvant showed encouraging results as a potential formulation for intranasally administered pertussis vaccines.

The cathelicidin CATH-2 efficiently neutralizes LPS- and E. coli-induced activation of porcine bone marrow derived macrophages

Infectious diseases in pigs cause monetary loss to farmers and pose a zoonotic risk. Therefore, it is important to obtain more porcine specific immunological knowledge as a measure to protect against infectious diseases, for example by exploring immunomodulators that are usable as vaccine adjuvants. Cathelicidins are a class of host defence peptides (HDPs) able to directly kill microbes as well as exert a diverse range of effects on the immune system. The peptides have shown promise as immunomodulatory peptides in many applications, including vaccines. However, it is currently unknown what the precise effect of these peptides is on porcine immune cells and whether peptides of other species might also have a strong immunomodulatory effect on porcine macrophages. Mononuclear bone marrow cells of pigs, aged 5-6 months, were cultured into M1 or M2 macrophages and stimulated with LPS or whole bacteria in the presence of host defence peptides (HDPs). CATH-2 and LL-37 strongly inhibited LPS-induced activation of M1 macrophages, the inhibition of LPS-induced activation of M2 macrophages by HDPs was milder, showing that the peptides have selective effects on different cell types. Upon stimulation with whole bacteria, only CATH-2 could effectively inhibit macrophage activation, showing the potent anti-inflammatory potential of this peptide. These results show that porcine peptides are not necessarily the most active in a porcine system, and that CATH-2 is effective in a porcine system as an anti-inflammatory immune modulator, which can be used, for example, in inactivated pathogen vaccines.

Improvement of RG1-VLP vaccine performance in BALB/c mice by substitution of alhydrogel with the next generation polyphosphazene adjuvant PCEP

Current human papillomavirus (HPV) vaccines provide substantial protection against the most common HPV types responsible for oral and anogenital cancers, but many circulating cancer-causing types remain for which vaccine coverage is lacking. In addition, all current HPV vaccines rely on aluminum salt-based adjuvant formulations that function through unclear mechanisms with few substitutes available. In an effort to expand the toolbox of available adjuvants suitable for HPV vaccines, we compared the immunogenicity of the RG1-VLP (virus-like particle) vaccine in BALB/c mice when formulated with either the aluminum hydroxide adjuvant Alhydrogel or the novel polyphosphazene macromolecular adjuvant poly[di (carboxylatoethylphenoxy) phosphazene] (PCEP). PCEP-formulated RG1-VLPs routinely outperformed VLP/Alhydrogel in several measurements of VLP-specific humoral immunity, including consistent improvements in the magnitude of antibody (Ab) responses to both HPV16-L1 and the L2 RG1 epitope as well as neutralizing titers to HPV16 and cross-neutralization of pseudovirion (PsV) types HPV18 and HPV39. Dose-sparing studies indicated that RG1-VLPs could be reduced in dose by 75% and the presence of PCEP ensured activity comparable to a full VLP dose adjuvanted by Alhydrogel. In addition, levels of HPV16-L1 and -L2-specific Abs were achieved after two vaccinations with PCEP as adjuvant that were equivalent to or greater than levels achieved with three vaccinations with Alhydrogel alone, indicating that the presence of PCEP resulted in accelerated immune responses that could allow for a decreased dose schedule. Given the extensive clinical track record of polyphosphazenes, these data suggest that substitution of alum-based adjuvants with PCEP for the RG1-VLP vaccine could lead to rapid seropositivity requiring fewer boosts, the dose-sparing of commercial VLP-based vaccines, and the establishment of longer-lasting humoral responses to HPV.

Rational design of innate defense regulator peptides as tumor vaccine adjuvants

The development of adjuvants has been an empirical process. Efforts to develop a new design and evaluation system for novel adjuvants are not only desirable but also necessary. Moreover, composite adjuvants that contain two or more types of adjuvants to synergistically enhance the immune response are important for adjuvant and vaccine design. Innate defense regulator peptides (IDRs) are promising adjuvants for clinical immunotherapy because they exhibit multifaceted immunomodulatory capabilities. However, the rational design and discovery of IDRs that have improved immunomodulatory activities have been hampered by the lack of screening techniques and the great challenges in the identification of their interaction partners. Here, we describe a screening and evaluation system for IDR design. On the basis of in vitro screening, the optimized IDR DP7 recruited neutrophils, monocytes and macrophages to the site of infection. The adjuvant, comprising the DP7 and CpG oligonucleotide (CpG), induced chemokine/cytokine expression, enhanced the antigen uptake by dendritic cells and upregulated surface marker expression in dendritic cells. Vaccination with the NY-ESO-1 or OVA antigens combined with the adjuvant alum/CpG/DP7 strongly suppressed tumor growth in mice which was due to the improvement of antigen-specific humoral and cellular immunity. Regarding the mechanism of action, GPR35 may be the potential interaction partner of DP7. Our study revealed the potential application of the screening and evaluation system as a strategy for rationally designing effective IDRs or composite adjuvants and identifying their mechanism of action.

Swine as biomedical animal model for T-cell research-Success and potential for transmittable and non-transmittable human diseases

Swine is biologically one of the most relevant large animal models for biomedical research. With its use as food animal that can be exploited as a free cell and tissue source for research and its high susceptibility to human diseases, swine additionally represent an excellent option for both the 3R principle and One Health research. One of the previously most limiting factors of the pig model was its arguably limited immunological toolbox. Yet, in the last decade, this toolbox has vastly improved including the ability to study porcine T-cells. This review summarizes the swine model for biomedical research with focus on T cells. It first contrasts the swine model to the more commonly used mouse and non-human primate model before describing the current capabilities to characterize and extend our knowledge on porcine T cells. Thereafter, it not only reflects on previous biomedical T-cell research but also extends into areas in which more in-depth T-cell analyses could strongly benefit biomedical research. While the former should inform on the successes of biomedical T-cell research in swine, the latter shall inspire swine T-cell researchers to find collaborations with researchers working in other areas - such as nutrition, allergy, cancer, transplantation, infectious diseases, or vaccine development.

Polyphosphazenes as Adjuvants for Animal Vaccines and Other Medical Applications

Polyphosphazenes are a class of experimental adjuvants that have shown great versatility as vaccine adjuvants in many animal species ranging from laboratory rodents to large animal species. Their adjuvant activity has shown promising results with numerous viral and bacterial antigens, as well as with crude and purified antigens. Vaccines adjuvanted with polyphosphazenes can be delivered via systemic and mucosal administration including respiratory, oral, rectal, and intravaginal routes. Polyphosphazenes can be used in combination with other adjuvants, further enhancing immune responses to antigens. The mechanisms of action of polyphosphazenes have not fully been defined, but several systematic studies have suggested that they act primarily by activating innate immunity. In the present review, we will highlight progress in the development of polyphosphazenes as adjuvants in animals and their other medical applications.

Polyphosphazene immunoadjuvants: Historical perspective and recent advances

The development of successful vaccines has been increasingly reliant on the use of immunoadjuvants - additives, which can enhance and modulate immune responses to vaccine antigens. Immunoadjuvants of the polyphosphazene family encompass synthetic biodegradable macromolecules, which attain in vivo activity via antigen delivery and immunostimulation mechanisms. Over the last decades, the technology has witnessed evolvement of next generation members, expansion to include various antigens and routes of administration, and progression to clinical phase. This was accompanied by gaining important insights into the mechanism of action and the development of a novel class of virus-mimicking nano-assemblies for antigen delivery. The present review evaluates in vitro and in vivo data generated to date in the context of latest advances in understanding the primary function and biophysical behavior of these macromolecules. It also provides an overview of relevant synthetic and characterization methods, macromolecular biodegradation pathways, and polyphosphazene-based multi-component, nanoparticulate, and microfabricated formulations.

The Long Road Toward COVID-19 Herd Immunity: Vaccine Platform Technologies and Mass Immunization Strategies

There is an urgent need for effective countermeasures against the current emergence and accelerating expansion of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Induction of herd immunity by mass vaccination has been a very successful strategy for preventing the spread of many infectious diseases, hence protecting the most vulnerable population groups unable to develop immunity, for example individuals with immunodeficiencies or a weakened immune system due to underlying medical or debilitating conditions. Therefore, vaccination represents one of the most promising counter-pandemic measures to COVID-19. However, to date, no licensed vaccine exists, neither for SARS-CoV-2 nor for the closely related SARS-CoV or Middle East respiratory syndrome-CoV. In addition, a few vaccine candidates have only recently entered human clinical trials, which hampers the progress in tackling COVID-19 infection. Here, we discuss potential prophylactic interventions for SARS-CoV-2 with a focus on the challenges existing for vaccine development, and we review pre-clinical progress and ongoing human clinical trials of COVID-19 vaccine candidates. Although COVID-19 vaccine development is currently accelerated via so-called fast-track programs, vaccines may not be timely available to have an impact on the first wave of the ongoing COVID-19 pandemic. Nevertheless, COVID-19 vaccines will be essential in the future for reducing morbidity and mortality and inducing herd immunity, if SARS-CoV-2 becomes established in the population like for example influenza virus.

Cathelicidins Modulate TLR-Activation and Inflammation

Cathelicidins are short cationic peptides that are part of the innate immune system. At first, these peptides were studied mostly for their direct antimicrobial killing capacity, but nowadays they are more and more appreciated for their immunomodulatory functions. In this review, we will provide a comprehensive overview of the various effects cathelicidins have on the detection of damage- and microbe-associated molecular patterns, with a special focus on their effects on Toll-like receptor (TLR) activation. We review the available literature based on TLR ligand types, which can roughly be divided into lipidic ligands, such as LPS and lipoproteins, and nucleic-acid ligands, such as RNA and DNA. For both ligand types, we describe how direct cathelicidin-ligand interactions influence TLR activation, by for instance altering ligand stability, cellular uptake and receptor interaction. In addition, we will review the more indirect mechanisms by which cathelicidins affect downstream TLR-signaling. To place all this information in a broader context, we discuss how these cathelicidin-mediated effects can have an impact on how the host responds to infectious organisms as well as how these effects play a role in the exacerbation of inflammation in auto-immune diseases. Finally, we discuss how these immunomodulatory activities can be exploited in vaccine development and cancer therapies.

Synthetic Cationic Peptide IDR-1002 and Human Cathelicidin LL37 Modulate the Cell Innate Response but Differentially Impact PRRSV Replication in vitro

Host defense peptides (HDPs) show both antimicrobial and immunomodulatory properties making them important mediators of the host immune system. In humans but also in pigs many HDPs have been identified and important families such as cathelicidins and defensins have been established. In our study, we assessed: (i) the potential interactions that could occur between three peptides (LL37, PR39, and synthetic innate defense regulator (IDR)-1002) and a common TLR ligand called poly(I:C); (ii) the impact of selected peptides on the response of alveolar macrophage (AM) to poly(I:C) stimulation; (iii) the anti-porcine respiratory and reproductive syndrome virus (PRRSV) properties of the peptides; and (iv) their adjuvant potential in a PRRSV challenge experiment after immunization with different vaccine formulations. The results are as following: LL37, PR39, and IDR-1002 were able to interact with poly(I:C) using an agarose gel migration assay. Then, an alteration of AM's response to poly(I:C) stimulation was observed when the cells were co-stimulated with LL37 and IDR-1002. Regarding the anti-PRRSV potential of the peptides only LL37 showed a PRRSV inhibition in infected AM as well as precision cut lung slices (PCLS). However, in our conditions and despite their immunomodulatory properties, neither LL37 nor IDR-1002 showed any convincing potential as an adjuvant when associated to killed PRRSV in a challenge experiment. In conclusion, both antiviral and immunomodulatory properties could be identified for LL37, only immunomodulatory properties for IDR-1002, and both peptides failed to improve the immune response consecutive to an immunization with a killed vaccine in a PPRSV challenge experiment. However, further studies are needed to fully decipher and explain differences between peptide properties.

A lipidic delivery system of a triple vaccine adjuvant enhances mucosal immunity following nasal administration in mice

We previously developed an highly efficacious combination adjuvant comprised of innate defense regulator (IDR)-1002 peptide, poly(I:C) and polyphosphazene (TriAdj). Here we aimed to design and test the in vivo efficacy of a mucoadhesive nasal formulation of this adjuvant. To determine the physical properties of the formulation, the effect of addition of each individual component was characterised by gel electrophoresis and fluorescence quenching using rhodamine-poly(I:C). Cationic liposomes comprised of didodecyl dimethylammonium bromide (DDAB), dioleoyl phosphatidylethanolamine (DOPE) (50:50 or 75:25 mol:mol) and DDAB, L-α-phosphatidylcholine (egg PC) and DOPE (40:50:10 mol:mol:mol) were prepared by the thin-film extrusion method. The liposomes and TriAdj were combined by simple mixing. The formed complex (L-TriAdj) was characterized by dynamic light scattering, zeta potential, and mucin interactions. We found that IDR-1002 peptide, polyphosphazene and poly(I:C) self-assembled in solution forming an anionic complex. Exposure of RAW267.4 mouse macrophage cells to TriAdj alone vs. L-TriAdj indicated that DDAB/DOPE (50:50) and DDAB/EPC/cholesterol (40:50:10) complexation reduced TriAdj toxicity. Next, TriAdj-containing cationic liposomes were prepared at several molar ratios to determine optimal size, stability and desired positive charge. Transmission electron microscopy showed rearrangement of lipid structures on binding of liposomes to TriAdj and to mucin. Stable particles (<200 nm over 24 h) showed mucin binding of DDAB/DOPE + TriAdj was greater than DDAB/EPC/DOPE + TriAdj. To verify in vivo efficacy, mice were administered the DDAB/DOPE + TriAdj complex intranasally with ovalbumin as the antigen, and the immunogenic response was measured by ELISA (serum IgG1, IgG2a, IgA) and ELISpot assays (splenocyte IL-5, IFN-γ). Mice administered adjuvant showed a significantly greater immune response with L-TriAdj than TriAdj alone, with a dose-response proportionate to the triple adjuvant content, and an overall balanced Th1/Th2 immune response representing both systemic and mucosal immunity.

Innate immune response profiles in pigs injected with vaccine adjuvants polydi(sodium carboxylatoethylphenoxy)phosphazene (PCEP) and Emulsigen

Vaccines are formulated with adjuvants to enhance or direct antigen-specific immune responses against pathogens. However, the mechanisms of action (MOA) of adjuvants are not well understood and are under-investigated in large animal species. We have previously reported that injection of mice induced innate immune responses as indicated by increased cell recruitment and cytokine production at the site of injection with polyphosphazene (PCEP) adjuvant. In the present study, we evaluated whether PCEP induced similar innate immune responses in pigs. Piglets were injected with either PCEP or Emulsigen intradermally (I.D.) and the local cellular infiltration and cytokine production were evaluated at the site of injection and the draining lymph nodes. PCEP induced infiltration of macrophages, T and B cells, leucocytes and necrotic debris at the site of injection as well as PCEP-induced leucocyte infiltration in the draining lymph nodes. Emulsigen induced diffuse infiltration of leucocytes, macrophages, and lymphocytes at the site of injection as well as at the draining lymph nodes. PCEP induced significant production of interleukin IL-1β, and IL-13 at the site of injection and IL-1β, and IL-6 at the draining lymph nodes. Emulsigen promoted the production of IL-1β, IL-6, and IL-12 at the site of injection but not in the draining lymph nodes. No cytokines were detected in blood after injection of either adjuvant. Together, our data indicate that in pigs, the adjuvants PCEP and Emulsigen stimulate early innate immune responses at the injection site by creating an immunocompetent environment that may contribute to increased immunogenicity of the co-administered antigens.

Recent advances in experimental polyphosphazene adjuvants and their mechanisms of action

Vaccination continues to be a very important public health intervention to control infectious diseases in the world. Subunit vaccines are generally poorly immunogenic and require the addition of adjuvants to induce protective immune responses. Despite their critical role in vaccines, adjuvant mechanism of action remains poorly understood, which is a barrier to the development of new, safe and effective vaccines. In the present review, we focus on recent progress in understanding the mechanisms of action of the experimental adjuvants poly[di(carboxylatophenoxy)phosphazene] (PCPP) and poly[di(sodiumcarboxylatoethyl-phenoxy)phosphazene] (PCEP) (in this review, adjuvants PCPP and PCEP are collectively referred to as PZ denoting polyphosphazenes). PZs are high molecular weight, water-soluble, synthetic polymers that have been shown to regulate innate immune response genes, induce cytokines and chemokines secretion at the site of injection and, also, induce immune cell recruitment to the site of injection to create a local immune-competent environment. There is an evidence that as well as its role as an immunoadjuvant (that activate innate immune responses), PZ can also act as a vaccine carrier. The mechanism of action that explains how PZ leads to these effects is not known and is a barrier to the development of designer vaccines.

What Is Wrong with Pertussis Vaccine Immunity? The Problem of Waning Effectiveness of Pertussis Vaccines

Pertussis is resurgent in some countries, particularly those in which children receive acellular pertussis (aP) vaccines in early infancy and boosters later in life. Immunologic studies show that, whereas whole-cell pertussis (wP) vaccines orient the immune system toward Th1/Th17 responses, acellular pertussis vaccines orient toward Th1/Th2 responses. Although aP vaccines do provide protection during the first years of life, the change in T-cell priming results in waning effectiveness of aP as early as 2-3 years post-boosters. Although other factors, such as increased virulence of pertussis strains, better diagnosis, and better surveillance may play a role, the increase in pertussis appears to be the result of waning immunity. In addition, studies in baboon models, requiring confirmation in humans, show that aP is less able to prevent nasopharyngeal colonization of Bordetella pertussis than wP or natural infection.

Induction of a balanced IgG1/IgG2 immune response to an experimental challenge with Mycoplasma bovis antigens following a vaccine composed of Emulsigen™, IDR peptide1002, and poly I:C

Prevention and or control of Mycoplasma bovis infections in cattle have relied on the treatment of animals with antibiotics; herd management including separation and or culling infected animals; and the use of vaccines with limited protection. Due to the negative reactions and incomplete protection observed after vaccination with some bacterin-based vaccines, there is a need to put more efforts in the development of recombinant-based vaccines. However, the arsenal of antigens that may be suitable for a fully protective vaccine is rather limited at this point. We have tested a vaccine formulation containing M. bovis proteins formulated with adjuvants that have been shown to aid in the protection against other pathogens. After vaccinations, the animals were challenged using a BHV-1/M. bovis co-infection model. While the PBMC proliferation and cytokine responses to the antigens in the vaccine were negligible, humoral responses reveal that eight antigens elicit a balanced IgG1/IgG2 response although this was not enough to confer protection against M. bovis.

CD71+ erythroid suppressor cells impair adaptive immunity against Bordetella pertussis

Infant’s immune system cannot control infection or respond to vaccination as efficiently as older individuals, a phenomenon that has been attributed to immunological immaturity. Recently, we challenged this notion and proposed the presence of actively immunosuppressive and physiologically enriched CD71⁺ erythroid cells in neonates. Here we utilized Bordetella pertussis, a common neonatal respiratory tract pathogen, as a proof of concept to investigate the role of these cells in adaptive immunity. We observed that CD71⁺ cells have distinctive immunosuppressive properties and prevent recruitment of immune cells to the mucosal site of infection. CD71⁺ cells ablation unleashed induction of B. pertussis-specific protective cytokines (IL-17 and IFN-γ) in the lungs and spleen upon re-infection or vaccination. We also found that CD71⁺ cells suppress systemic and mucosal B. pertussis-specific antibody responses. Enhanced antigen-specific adaptive immunity following CD71⁺ cells depletion increased resistance of mice to B. pertussis infection. Furthermore, we found that human cord blood CD71⁺ cells also suppress T and B cell functions in vitro. Collectively, these data provide important insight into the role of CD71⁺ erythroid cells in adaptive immunity. We anticipate our results will spark renewed investigation in modulating the function of these cells to enhance host defense to infections in newborns.

Multistage vaccines containing outer membrane, type III secretion system and inclusion membrane proteins protects against a Chlamydia genital tract infection and pathology

Pathogens with a complex lifecycles can effectively evade host immunity in part due to each developmental stage expressing unique sets of antigens. Multisubunit vaccines incorporating signature antigens reflecting distinct developmental stages (multistage vaccines) have proven effective against viral, bacterial and parasitic infection at preventing pathogen evasion of host immunity. Chlamydia trachomatis is characterized by a biphasic extra/intracellular developmental cycle and an acute/persistent (latent) metabolic state; hence a multistage vaccine may prevent immune evasion and enhance clearance. Here we tested the efficacy of a multistage vaccine containing outer membrane (MOMP and PmpG), type three secretion system (T3SS) (CdsF and TC0873) and inclusion membrane proteins (IncA and TC0500) in mice against an intravaginal challenge with Chlamydia muridarum. Comparison of single (eg. MOMP) and double antigen vaccines (eg. MOMP and PmpG), largely targeting the extracellular stage, elicited significant yet comparable protection against vaginal shedding when compared to unimmunized control mice. Utilization of different adjuvants (ISCOMATRIX - IMX, PCEP/polyI:C/IDR1002 - VIDO, CTA1-DD and ADVAX) and numerous immunization routes (subcutaneous - SQ and intranasal - IN) further enhanced protection against infection. However, a multistage vaccine elicited significantly greater protection against vaginal shedding and upper genital tract pathology than vaccines targeting only extra- or intracellular stages. This indicates that protection elicited by a vaccine targeting extracellular chlamydial antigens could be improved by including chlamydial antigen expressed during intracellular phase.

Intranasal vaccination with an adjuvanted polyphosphazenes nanoparticle-based vaccine formulation stimulates protective immune responses in mice

The most promising strategy to sustainably prevent infectious diseases is vaccination. However, emerging as well as re-emerging diseases still constitute a considerable threat. Furthermore, lack of compliance and logistic constrains often result in the failure of vaccination campaigns. To overcome these hurdles, novel vaccination strategies need to be developed, which fulfill maximal safety requirements, show maximal efficiency and are easy to administer. Mucosal vaccines constitute promising non-invasive approaches able to match these demands. Here we demonstrate that nanoparticle (polyphosphazenes)-based vaccine formulations including c-di-AMP as adjuvant, cationic innate defense regulator peptides (IDR) and ovalbumin (OVA) as model antigen were able to stimulate strong humoral and cellular immune responses, which conferred protection against the OVA expressing influenza strain A/WSN/OVA_I (H1N1). The presented results confirm the potency of nanoparticle-based vaccine formulations to deliver antigens across the mucosal barrier, but also demonstrate the necessity to include adjuvants to stimulate efficient antigen-specific immune responses.

Immune responses to in ovo vaccine formulations containing inactivated fowl adenovirus 8b with poly[di(sodium carboxylatoethylphenoxy)]phosphazene (PCEP) and avian beta defensin as adjuvants in chickens

Inclusion body hepatitis (IBH) is one of the major viral infections causing substantial economic loss to the global poultry industry. The disease is characterized by a sudden onset of mortality (2-30%) and high morbidity (60-70%). IBH is caused by a number of serotypes of fowl adenovirus with substantially low levels of serotype cross protection. Thus far, there is no effective and safe vaccine commercially available in the North America for the control of IBH in chickens. Poly[di(sodium carboxylatoethylphenoxy)]phosphazene (PCEP) is a high molecular weight, biodegradable water soluble polymer that has been well characterized as a safe and effective adjuvant for a number of experimental veterinary vaccines. Similarly, host defence peptides, including β-defensins, have also been shown to exhibit strong adjuvant potential. In this study, we evaluated the adjuvant activity of PCEP and avian beta defensin (ABD) in a vaccine formulation containing inactivated fowl adenovirus (FAdV) serotype 8b administered in ovo. Our data showed that a combination of PCEP and inactivated virus is capable of inducing a robust and long lasting antibody response. Moreover, significant enhancement of IFN-γ, IFN-α, IL-12(p40) and IL-6 gene expression under the influence of PCEP suggests that as an in ovo adjuvant PCEP has the ability to activate a substantial balanced immune response in chickens. To our knowledge, these are the first studies in which PCEP and ABD have been characterized as adjuvants for the development of an in ovo poultry vaccine. It is expected that these preliminary studies will be helpful in the development of safer and more effective in ovo vaccine against IBH and other infectious diseases affecting chickens.

Response of immune response genes to adjuvants poly [di(sodium carboxylatoethylphenoxy)phosphazene] (PCEP), CpG oligodeoxynucleotide and emulsigen at intradermal injection site in pigs

Understanding the mechanisms by which adjuvants mediate their effects provide critical information on how innate immunity influences the development of adaptive immunity. Despite being a critical vaccine component, the mechanisms by which adjuvants mediate their effects are not fully understood and this is especially true when they are used in large animals. This lack of understanding limits our ability to design effective vaccines. In the present study, we administered polyphosphazene (PCEP), CpG oligodeoxynucleotides (CpG), emulsigen or saline via an intradermal injection into pigs and assessed the impact on the expression of reported 'adjuvant response genes' over time. CpG induced a strong upregulation of the chemokine CXL10 several 'Interferon Response Genes', as well as TNFα, and IL-10, and a down-regulation of IL-17 genes. Emulsigen upregulated expression of chemokines CCL2 and CCL5, proinflammatory cytokines IL-6 and TNFα, as well as TLR9, and several IFN response genes. PCEP induced the expression of chemokine CCL2 and proinflammatory cytokine IL-6. These results suggest that emulsigen and CpG may promote recruitment of innate immune cells and Th1 type cytokine production but that PCEP may promote a Th-2 type immune response through the induction of IL-6, an inducer of B cell activity and differentiation.

Administration of Poly[di(sodium carboxylatoethylphenoxy)phosphazene] (PCEP) and Avian Beta Defensin as Adjuvants in Inactivated Inclusion Body Hepatitis Virus and its Hexon Protein-Based Experimental Vaccine Formulations in Chickens

Inclusion body hepatitis (IBH) is one of the major infectious diseases adversely affecting the poultry industry of the United States and Canada. Currently, no effective and safe vaccine is available for the control of IBH virus (IBHV) infection in chickens. However, based on the excellent safety and immunogenic profiles of experimental veterinary vaccines developed with the use of new generation adjuvants, we hypothesized that characterization of vaccine formulations containing inactivated IBHV or its capsid protein hexon as antigens, along with poly[di(sodium carboxylatoethylphenoxy)phosphazene] (PCEP) and avian beta defensin 2 (ABD2) as vaccine adjuvants, will be helpful in development of an effective and safe vaccine formulation for IBH. Our data demonstrated that experimental administration of vaccine formulations containing inactivated IBHV and a mixture of PCEP with or without ABD2 as an adjuvant induced significantly higher antibody responses compared with other vaccine formulations, while hexon protein-based vaccine formulations showed relatively lower levels of antibody responses. Thus, a vaccine formulation containing inactivated IBHV with PCEP or a mixture of PCEP and ABD2 (with a reduced dosage of PCEP) as an adjuvant may serve as a potential vaccine candidate. However, in order to overcome the risks associated with whole virus inactivated vaccines, characterization of additional viral capsid proteins, including fiber protein and penton of IBHV along with hexon protein in combination with more new generation adjuvants, will be helpful in further improvements of vaccines against IBHV infection.

Immune responses to Mycoplasma bovis proteins formulated with different adjuvants

Most vaccines for protection against Mycoplasma bovis disease are made of bacterins, and they offer varying degrees of protection. Our focus is on the development of a subunit-based protective vaccine, and to that end, we have identified 10 novel vaccine candidates. After formulation of these candidates with TriAdj, an experimental tri-component novel vaccine adjuvant developed at VIDO-InterVac, we measured humoral and cell-mediated immune responses in vaccinated animals. In addition, we compared the immune responses after formulation with TriAdj with the responses measured in animals vaccinated with a mix of a commercial adjuvant (Emulsigen™) and 2 of the components of the TriAdj, namely polyinosinic:polycytidylic acid (poly I:C) and the cationic innate defense regulator (IDR) peptide 1002 (VQRWLIVWRIRK). In this latter trial, we detected significant IgG1 humoral immune responses to 8 out of 10 M. bovis proteins, and IgG2 responses to 7 out of 10 proteins. Thus, we concluded that the commercial adjuvant formulated with poly I:C and the IDR peptide 1002 is the best formulation for the experimental vaccine.

Protecting Newborns Against Pertussis: Treatment and Prevention Strategies

Pertussis is a potentially severe respiratory disease, which affects all age groups from young infants to older adults and is responsible for an estimated 195,000 deaths occurred globally in 2008. Active research is ongoing to better understand the pathogenesis, immunology, and diagnosis of pertussis. For diagnosis, molecular assays (e.g., polymerase chain reaction) for detection of Bordetella pertussis have become more widely available and support improved outbreak detection. In children, pertussis vaccines have been incorporated into routine immunization schedules and deployed for pertussis outbreak control. Lower levels of vaccine coverage are now being observed in communities where vaccine hesitancy is rising. Additionally, recognition that newborn babies are at risk of pertussis in the USA and UK has led to recommendations to immunize pregnant women. Among adolescents and older adults in the USA, Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular pertussis (Tdap) Vaccines are recommended, but substantial individual- and system-level barriers exist that will make achieving national Healthy People 2020 targets for immunization challenging. Current antimicrobial regimens for pertussis are focused on reducing the severity of disease, reducing rates of sequelae, and minimizing transmission of infection to susceptible individuals. Continued surveillance for pertussis will be important to identify opportunities for reducing young infants' exposure and reducing the impact of outbreaks among school-aged children. Laboratory-based surveillance for newly emerging strains of B. pertussis will be important to identify strains that may evade protection elicited by currently available vaccines. Efforts to develop new-generation pertussis vaccines should be considered now in anticipation of vaccine development programs, which may require ten or more years to deliver a licensed vaccine.

Importance of Endosomal Cathelicidin Degradation To Enhance DNA-Induced Chicken Macrophage Activation

Cathelicidins are essential in the protection against invading pathogens through both their direct antimicrobial activity and their immunomodulatory functions. Although cathelicidins are known to modulate activation by several TLR ligands, little is known about their influence on DNA-induced macrophage activation. In this study, we explored the effects of cathelicidins on DNA-induced activation of chicken macrophages and elucidated the intracellular processes underlying these effects. Our results show that chicken cathelicidin (CATH)-2 strongly enhances DNA-induced activation of both chicken and mammalian macrophages because of enhanced endocytosis of DNA-CATH-2 complexes. After endocytosis, DNA is liberated from the complex because of proteolytic breakdown of CATH-2, after which TLR21 is activated. This leads to increased cytokine expression and NO production. Through the interaction with DNA, CATH-2 can play an important role in modulating the immune response at sites of infection. These observations underline the importance of cathelicidins in sensing bacterial products and regulating immune responses.

Plant-based solutions for veterinary immunotherapeutics and prophylactics

An alarming increase in emergence of antibiotic resistance among pathogens worldwide has become a serious threat to our ability to treat infectious diseases according to the World Health Organization. Extensive use of antibiotics by livestock producers promotes the spread of new resistant strains, some of zoonotic concern, which increases food-borne illness in humans and causes significant economic burden on healthcare systems. Furthermore, consumer preferences for meat/poultry/fish produced without the use of antibiotics shape today's market demand. So, it is viewed as inevitable by the One Health Initiative that humans need to reduce the use of antibiotics and turn to alternative, improved means to control disease: vaccination and prophylactics. Besides the intense research focused on novel therapeutic molecules, both these strategies rely heavily on the availability of cost-effective, efficient and scalable production platforms which will allow large-volume manufacturing for vaccines, antibodies and other biopharmaceuticals. Within this context, plant-based platforms for production of recombinant therapeutic proteins offer significant advantages over conventional expression systems, including lack of animal pathogens, low production costs, fast turnaround and response times and rapid, nearly-unlimited scalability. Also, because dried leaves and seeds can be stored at room temperature for lengthy periods without loss of recombinant proteins, plant expression systems have the potential to offer lucrative benefits from the development of edible vaccines and prophylactics, as these would not require "cold chain" storage and transportation, and could be administered in mass volumes with minimal processing. Several biotechnology companies currently have developed and adopted plant-based platforms for commercial production of recombinant protein therapeutics. In this manuscript, we outline the challenges in the process of livestock immunization as well as the current plant biotechnology developments aimed to address these challenges.

Improved pertussis vaccines based on adjuvants that induce cell-mediated immunity

Bordetella pertussis is a Gram-negative bacterium that causes the severe and sometimes lethal respiratory disease whooping cough in infants and children. There has been a recent resurgence in the number of cases of pertussis in several countries with high vaccine coverage. This has been linked with waning or ineffective immunity induced by current acellular pertussis vaccines. These acellular pertussis vaccines are formulated with alum as the adjuvant, which promotes strong antibody responses but is less effective at inducing Th1-type responses crucial for effective bacterial clearance. Studies in animal models have demonstrated that replacing alum with alternative adjuvants, such as toll-like receptor agonists, can promote more robust cell-mediated immunity and confer a high level of protection against infection following respiratory challenge.

Mouse and pig models for studies of natural and vaccine-induced immunity to Bordetella pertussis

The increasing incidence of whooping cough in many developed countries has been linked with waning immunity induced after immunization with acellular pertussis (aP) vaccines. The rational design of an improved aP vaccine requires a full understanding of the mechanism of protective immunity and preclinical studies in animal models. Infection of mice and pigs with Bordetella pertussis has many features of the infection seen in humans and has already provided valuable information on the roles of innate and adaptive immune responses in protection. Recent findings in these models have already indicated that it may be possible to develop an improved aP vaccine based on a formulation that includes a Toll-like receptor agonist as an adjuvant.

The pertussis problem

Pertussis is resurgent, and many cases are occurring in vaccinated children and adolescents. In countries using acellular vaccines, waning immunity is at least part of the problem. This article discusses possible improvements in those vaccines.

Peptide design for antimicrobial and immunomodulatory applications

The increasing threat of antibiotic resistance in pathogenic bacteria and the dwindling supply of antibiotics available to combat these infections poses a significant threat to human health throughout the world. Antimicrobial peptides (AMPs) have long been touted as the next generation of antibiotics capable of filling the anti-infective void. Unfortunately, peptide-based antibiotics have yet to realize their potential as novel pharmaceuticals, in spite of the immense number of known AMP sequences and our improved understanding of their antibacterial mechanism of action. Recently, the immunomodulatory properties of certain AMPs have become appreciated. The ability of small synthetic peptides to protect against infection in vivo has demonstrated that modulation of the innate immune response is an effective strategy to further develop peptides as novel anti-infectives. This review focuses on the screening methods that have been used to assess novel peptide sequences for their antibacterial and immunomodulatory properties. It will also examine how we have progressed in our ability to identify and optimize peptides with desired biological characteristics and enhanced therapeutic potential. In addition, the current challenges to the development of peptides as anti-infectives are examined and the strategies being used to overcome these issues are discussed.

Protein coated microcrystals formulated with model antigens and modified with calcium phosphate exhibit enhanced phagocytosis and immunogenicity

Protein-coated microcrystals (PCMCs) were investigated as potential vaccine formulations for a range of model antigens. Presentation of antigens as PCMCs increased the antigen-specific IgG responses for all antigens tested, compared to soluble antigens. When compared to conventional aluminium-adjuvanted formulations, PCMCs modified with calcium phosphate (CaP) showed enhanced antigen-specific IgG responses and a decreased antigen-specific IgG1:IgG2a ratio, indicating the induction of a more balanced Th1/Th2 response. The rate of antigen release from CaP PCMCs, in vitro, decreased strongly with increasing CaP loading but their immunogenicity in vivo was not significantly different, suggesting the adjuvanticity was not due to a depot effect. Notably, it was found that CaP modification enhanced the phagocytosis of fluorescent antigen-PCMC particles by J774.2 murine monocyte/macrophage cells compared to soluble antigen or soluble PCMCs. Thus, CaP PCMCs may provide an alternative to conventional aluminium-based acellular vaccines to provide a more balanced Th1/Th2 immune response.

Efficient delivery of the toll-like receptor agonists polyinosinic:polycytidylic acid and CpG to macrophages by acetalated dextran microparticles

To enhance the immune activity of vaccine adjuvants polyinosinic:polycytidylic acid (poly I:C) and CpG acetalated dextran (Ac-DEX) microparticles can be used. Ac-DEX is a biodegradable and water-insoluble polymer that degrades significantly faster at pH 5.0 (phagosomal pH) than at pH 7.4 and has tunable degradation rates that can range from hours to months. This is an ideal characteristic for delivery of an antigen and adjuvant within the lysosomal compartment of a phagocytic cell. We evaluated poly I:C and CpG encapsulated in Ac-DEX microparticles using RAW macrophages as a model antigen-presenting cell. These cells were cultured with poly I:C or CpG in their free form, encapsulated in a fast degrading Ac-DEX, in slow degrading Ac-DEX, or in the Food and Drug Administration-approved polymer poly(lactic-co-glycolic acid) (PLGA). Ac-DEX had higher encapsulation efficiencies for both poly I:C and CpG than PLGA. Furthermore, poly I:C or CpG encapsulated in Ac-DEX also showed, in general, a significantly stronger immunostimulatory response than PLGA and unencapsulated CpG or poly I:C, which was indicated by a higher rate of nitric oxide release and increased levels of cytokines such as TNF-α, IL-6, IL-10, and IFN-γ. Overall, we have illustrated a method for enhancing the delivery of these vaccine adjuvants to further enhance the development of Ac-DEX vaccine formulations.

The role of dendritic cells in innate and adaptive immunity to respiratory syncytial virus, and implications for vaccine development

Respiratory syncytial virus (RSV) is a common human pathogen that causes cold-like symptoms in most healthy adults and children. However, RSV often moves into the lower respiratory tract in infants and young children predisposed to respiratory illness, making it the most common cause of pediatric broncheolitis and pneumonia. The development of an appropriate balanced immune response is critical for recovery from RSV, while an unbalanced and/or excessively vigorous response may lead to immunopathogenesis. Different dendritic cell (DC) subsets influence the magnitude and quality of the host response to RSV infection, with myeloid DCs mediating and plasmacytoid DCs modulating immunopathology. Furthermore, stimulation of DCs through Toll-like receptors is essential for induction of protective immunity to RSV. These characteristics have implications for the rational design of a RSV vaccine.

Do we know the Th1/Th2/Th17 determinants of vaccine response?

EVALUATION OF: Kamath AT, Mastelic B, Christensen D et al. Synchronization of dendritic cell activation and antigen exposure is required for the induction of Th1/Th17 responses. J. Immunol. 188(10), 4828–4837 (2012).The determinants of Th1/Th2/Th17 responses elicited by vaccine formulations are largely undefined and are an intense area of research. Most of the present licensed alum-adjuvanted subunit vaccines fail to elicit Th1/Th17 immune responses, and Th2 antibody responses are weak and often require repeated immunizations. Moreover, such responses are not sufficient for eliminating intracellular pathogens. Th1 responses have been traditionally elicited by live-attenuated, vector-based or Toll-like receptor ligand-adjuvanted formulations for optimal stimulation of the innate immune system and immunomodulation. The linkage of adjuvant and antigen (Ag) physically, and/or in a formulation, is essential to overcome systemic effects of the adjuvant and elicit Th1/Th17 responses. The role of delivery systems for codelivery of adjuvant and Ag to the same dendritic cell has gained acceptance. The milieu in which dendritic cells process and present Ag to naive CD4+ T cells determines their polarization into different subsets.

Re-emergence of pertussis: what are the solutions?

Whooping cough, due to Bordetella pertussis and Bordetella parapertussis, is an important cause of childhood morbidity and mortality. Despite widespread pertussis immunization in childhood, there are an estimated 50 million cases and 300,000 deaths due to pertussis globally each year. Infants who are too young to be vaccinated, children who are partially vaccinated and fully-vaccinated persons with waning immunity are especially vulnerable to disease. Since pertussis is one of the vaccine-preventable diseases on the rise, additional vaccine approaches are needed. These approaches include vaccination of newborns, additional booster doses for older adolescents and adults, and immunization of pregnant women with existing vaccines. Innovative new vaccines are also being studied. Each of these options will be discussed and their potential impact on pertussis control assessed.

Pertussis re-emergence in the post-vaccination era

BACKGROUND

Resurgence of pertussis in the post-vaccination era has been reported in Western countries. A shift of cases from school-age children to adolescents, adults and children under 1 year of age has been described in the last decade, and mortality rates in infants are still sustained. We aimed to review and discuss the possible vaccination strategies which can be adopted in order to improve the pertussis control, by searches of Pubmed, and websites of US and European Centers for Disease Control and Prevention, between 1st January 2002, and 1st March 2013.

DISCUSSION

The following vaccination strategies have been retrieved and analysed: the cocooning strategy, the immunization of pregnant women and newborns, vaccination programs for preschool children, adolescents, adults and health-care workers. Cost-effectiveness studies provide some contrasting data, mainly supporting both maternal vaccination and cocooning. Adolescent and/or adult vaccination seems to be cost-effective, however data from observational studies suggest that this vaccination strategy, used alone, leads to a reduced pertussis burden globally, but does not affect the disease incidence in infants. Moreover, substantial logistical and economic difficulties have to be overcome to vaccinate the largest number of individuals.

SUMMARY

The simultaneous use of more than one strategy, including cocooning strategy plus vaccination of adolescents and adults, seems to be the most reasonable preventive measure. The development of new highly immunogenic and efficacious pertussis vaccines continues to be a primary objective for the control of pertussis.

A CpG-containing oligodeoxynucleotide adjuvant for acellular pertussis vaccine improves the protective response against Bordetella pertussis

We investigated the adjuvant effect of CpG ODN alone or in combination with aluminum hydroxide on the immune response to the three main antigens presented in current acellular pertussis vaccines: pertussis toxoid, filamentous haemagglutinin and pertactin. The development of protection in mice was investigated for the intra-peritoneal and intra-nasal immunisation routes. The results showed that CpG ODN alone, or in combination with aluminum hydroxide, gave enhancement in anti-pertussis toxin, anti- filamentous haemagglutinin and especially anti-pertactin titers after mucosal immunisation. Higher macrophage NO levels indicating activation were found when the antigens were co-formulated with CpG ODN. Vaccines containing CpG ODN gave enhanced humoral and CMI responses with a shift toward Th-1 and increased protection against challenge infection with B.pertussis in mice.

Synthetic immunomodulatory peptide IDR-1002 enhances monocyte migration and adhesion on fibronectin

Regulation of the immune system by immunomodulatory agents, such as the synthetic innate defense regulator (IDR) peptides, has been proposed as a potential strategy to strengthen host immune responses against infection. IDR peptides confer protection in vivo against a range of bacterial infections and have been developed as components of single-dose vaccine adjuvants due to their ability to modulate innate immunity, correlating with an increased recruitment of monocytes to sites of infection or immunization. However, the mechanisms by which IDR peptides augment monocyte recruitment remain poorly defined. Anti-infective peptide IDR-1002 was demonstrated here to lack direct monocyte chemoattractive activity yet enhance, by up to 5-fold, the ability of human monocytes to migrate on fibronectin towards chemokines. This effect correlated with an increased adhesion of monocytes and THP-1 cells to fibronectin by IDR-1002 and other IDR peptides and the adhesion of THP-1 cells to fibronectin occurred in a β(1)-integrin-dependent manner, corresponding with an increased activation of β(1)-integrins and the phosphoinositide 3-kinase (PI3K)-Akt pathway. PI3K- and Akt-specific inhibitors abrogated IDR-1002-induced adhesion and activation of β(1)-integrins, whereas p38 and MEK1 inhibitors did not affect, or moderately inhibited, adhesion, respectively. Furthermore, IDR-1002 enhancement of monocyte migration towards chemokines and activation of β(1)-integrins was abrogated in the presence of PI3K- and Akt-specific inhibitors. In summary, IDR-1002 enhanced monocyte migration on fibronectin through promotion of β(1)-integrin-mediated interactions regulated by the PI3K-Akt pathway, revealing a mechanism by which IDR-1002 promotes monocyte recruitment.

New pertussis vaccination approaches: en route to protect newborns?

Pertussis or whooping cough is a life-threatening childhood disease, particularly severe during the first months of life, although adolescent and adult pertussis is increasingly more noted. General vaccination has tremendously reduced its incidence but has failed to bring it completely under control. In fact, it remains one of the most poorly controlled vaccine-preventable diseases in the world. New vaccination strategies are thus being explored. These include vaccination of pregnant mothers to transmit protective antibodies to the offspring, a cocooning strategy to prevent the transmission of the disease from family members to the newborn and neonatal vaccination. All have their inherent limitations, and improved vaccines are urgently needed. Two types of pertussis vaccines are currently available, whole-cell, first-generation and second-generation, acellular vaccines, with an improved safety profile. Attempts have been made to discover additional protective antigens to the 1-5 currently included in the acellular vaccines or to include new adjuvants. Recently, a live attenuated nasal Bordetella pertussis vaccine has been developed and undergone first-in-man clinical trials. However, as promising as it may be, in order to protect infants against severe disease, a single approach may not be sufficient, and multiple strategies applied in a concerted fashion may ultimately be required.

Therapeutic strategies based on polymeric microparticles

The development of the field of materials science, the ability to perform multidisciplinary scientific work, and the need for novel administration technologies that maximize therapeutic effects and minimize adverse reactions to readily available drugs have led to the development of delivery systems based on microencapsulation, which has taken one step closer to the target of personalized medicine. Drug delivery systems based on polymeric microparticles are generating a strong impact on preclinical and clinical drug development and have reached a broad development in different fields supporting a critical role in the near future of medical practice. This paper presents the foundations of polymeric microparticles based on their formulation, mechanisms of drug release and some of their innovative therapeutic strategies to board multiple diseases.