Adjuvants in cutaneous vaccination: A comprehensive analysis

Skin is the body's largest organ and serves as a protective barrier from physical, thermal, and mechanical environmental challenges. Alongside, the skin hosts key immune system players, such as the professional antigen-presenting cells (APCs) like the Langerhans cells in the epidermis and circulating macrophages in the blood. Further, the literature supports that the APCs can be activated by antigen or vaccine delivery via multiple routes of administration through the skin. Once activated, the stimulated APCs drain to the associated lymph nodes and gain access to the lymphatic system. This further allows the APCs to engage with the adaptive immune system and activate cellular and humoral immune responses. Thus, vaccine delivery via skin offers advantages such as reliable antigen delivery, superior immunogenicity, and convenient delivery. Several preclinical and clinical studies have demonstrated the significance of vaccine delivery using various routes of administration via skin. However, such vaccines often employ adjuvant/(s), along with the antigen of interest. Adjuvants augment the immune response to a vaccine antigen and improve the therapeutic efficacy. Due to these reasons, adjuvants have been successfully used with infectious disease vaccines, cancer immunotherapy, and immune-mediated diseases. To capture these developments, this review will summarize preclinical and clinical study results of vaccine delivery via skin in the presence of adjuvants. A focused discussion regarding the FDA-approved adjuvants will address the experiences of using such adjuvant-containing vaccines. In addition, the challenges and regulatory concerns with these adjuvants will be discussed. Finally, the review will share the prospects of adjuvant-containing vaccines delivered via skin.

Secreted Aspartic Proteinases: Key Factors in Candida Infections and Host-Pathogen Interactions

Extracellular proteases are key factors contributing to the virulence of pathogenic fungi from the genus Candida. Their proteolytic activities are crucial for extracting nutrients from the external environment, degrading host defenses, and destabilizing the internal balance of the human organism. Currently, the enzymes most frequently described in this context are secreted aspartic proteases (Saps). This review comprehensively explores the multifaceted roles of Saps, highlighting their importance in biofilm formation, tissue invasion through the degradation of extracellular matrix proteins and components of the coagulation cascade, modulation of host immune responses via impairment of neutrophil and monocyte/macrophage functions, and their contribution to antifungal resistance. Additionally, the diagnostic challenges associated with Candida infections and the potential of Saps as biomarkers were discussed. Furthermore, we examined the prospects of developing vaccines based on Saps and the use of protease inhibitors as adjunctive therapies for candidiasis. Given the complex biology of Saps and their central role in Candida pathogenicity, a multidisciplinary approach may pave the way for innovative diagnostic strategies and open new opportunities for innovative clinical interventions against candidiasis.

Immunogenicity of Recombinant Lipid-Based Nanoparticle Vaccines: Danger Signal vs. Helping Hand

Infectious diseases are a predominant problem in human health. While the incidence of many pathogenic infections is controlled by vaccines, some pathogens still pose a challenging task for vaccine researchers. In order to face these challenges, the field of vaccine development has changed tremendously over the last few years. For non-replicating recombinant antigens, novel vaccine delivery systems that attempt to increase the immunogenicity by mimicking structural properties of pathogens are already approved for clinical applications. Lipid-based nanoparticles (LbNPs) of different natures are vesicles made of lipid layers with aqueous cavities, which may carry antigens and other biomolecules either displayed on the surface or encapsulated in the cavity. However, the efficacy profile of recombinant LbNP vaccines is not as high as that of live-attenuated ones. This review gives a compendious picture of two approaches that affect the immunogenicity of recombinant LbNP vaccines: (i) the incorporation of immunostimulatory agents and (ii) the utilization of pre-existing or promiscuous cellular immunity, which might be beneficial for the development of tailored prophylactic and therapeutic LbNP vaccine candidates.

Immunological profile of mice immunized with a polyvalent virosome-based influenza vaccine

BACKGROUND

Influenza A virus (IAV) causes respiratory disease in pigs and is a major concern for public health. Vaccination of pigs is the most successful measure to mitigate the impact of the disease in the herds. Influenza-based virosome is an effective immunomodulating carrier that replicates the natural antigen presentation pathway and has tolerability profile due to their purity and biocompatibility.

METHODS

This study aimed to develop a polyvalent virosome influenza vaccine containing the hemagglutinin and neuraminidase proteins derived from the swine IAVs (swIAVs) H1N1, H1N2 and H3N2 subtypes, and to investigate its effectiveness in mice as a potential vaccine for swine. Mice were immunized with two vaccine doses (1 and 15 days), intramuscularly and intranasally. At 21 days and eight months later after the second vaccine dose, mice were euthanized. The humoral and cellular immune responses in mice vaccinated intranasally or intramuscularly with a polyvalent influenza virosomal vaccine were investigated.

RESULTS

Only intramuscular vaccination induced high hemagglutination inhibition (HI) titers. Seroconversion and seroprotection (> 4-fold rise in HI antibody titers, reaching a titer of ≥ 1:40) were achieved in 80% of mice (intramuscularly vaccinated group) at 21 days after booster immunization. Virus-neutralizing antibody titers against IAV were detected at 8 months after vaccination, indicating long-lasting immunity. Overall, mice immunized with the virosome displayed greater ability for B, effector-T and memory-T cells from the spleen to respond to H1N1, H1N2 and H3N2 antigens.

CONCLUSIONS

All findings showed an efficient immune response against IAVs in mice vaccinated with a polyvalent virosome-based influenza vaccine.

A low dose of RBD and TLR7/8 agonist displayed on influenza virosome particles protects rhesus macaque against SARS-CoV-2 challenge

Influenza virosomes serve as antigen delivery vehicles and pre-existing immunity toward influenza improves the immune responses toward antigens. Here, vaccine efficacy was evaluated in non-human primates with a COVID-19 virosome-based vaccine containing a low dose of RBD protein (15 µg) and the adjuvant 3M-052 (1 µg), displayed together on virosomes. Vaccinated animals (n = 6) received two intramuscular administrations at week 0 and 4 and challenged with SARS-CoV-2 at week 8, together with unvaccinated control animals (n = 4). The vaccine was safe and well tolerated and serum RBD IgG antibodies were induced in all animals and in the nasal washes and bronchoalveolar lavages in the three youngest animals. All control animals became strongly sgRNA positive in BAL, while all vaccinated animals were protected, although the oldest vaccinated animal (V1) was transiently weakly positive. The three youngest animals had also no detectable sgRNA in nasal wash and throat. Cross-strain serum neutralizing antibodies toward Wuhan-like, Alpha, Beta, and Delta viruses were observed in animals with the highest serum titers. Pro-inflammatory cytokines IL-8, CXCL-10 and IL-6 were increased in BALs of infected control animals but not in vaccinated animals. Virosomes-RBD/3M-052 prevented severe SARS-CoV-2, as shown by a lower total lung inflammatory pathology score than control animals.

Nanomaterials to combat SARS-CoV-2: Strategies to prevent, diagnose and treat COVID-19

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the associated coronavirus disease 2019 (COVID-19), which severely affect the respiratory system and several organs and tissues, and may lead to death, have shown how science can respond when challenged by a global emergency, offering as a response a myriad of rapid technological developments. Development of vaccines at lightning speed is one of them. SARS-CoV-2 outbreaks have stressed healthcare systems, questioning patients care by using standard non-adapted therapies and diagnostic tools. In this scenario, nanotechnology has offered new tools, techniques and opportunities for prevention, for rapid, accurate and sensitive diagnosis and treatment of COVID-19. In this review, we focus on the nanotechnological applications and nano-based materials (i.e., personal protective equipment) to combat SARS-CoV-2 transmission, infection, organ damage and for the development of new tools for virosurveillance, diagnose and immune protection by mRNA and other nano-based vaccines. All the nano-based developed tools have allowed a historical, unprecedented, real time epidemiological surveillance and diagnosis of SARS-CoV-2 infection, at community and international levels. The nano-based technology has help to predict and detect how this Sarbecovirus is mutating and the severity of the associated COVID-19 disease, thereby assisting the administration and public health services to make decisions and measures for preparedness against the emerging variants of SARS-CoV-2 and severe or lethal COVID-19.

Erythrocyte Ghost Based Fusogenic Glycoprotein Vesicular Stomatitis Virus Glycoprotein Complexes as an Efficient Deoxyribonucleic Acid Delivery System

This study aimed to construct a new type of fused erythrocyte vector for gene delivery system. The conditioned medium of AD293 cells expressing vesicular stomatitis virus glycoprotein gene was collected, and erythrocyte ghost was prepared by hypotonic lysis. Using cationic polymer to condense deoxyribonucleic acid to form a complex, fusogenic erythrocyte ghost was incubated with this complex to obtain virion. Flow cytometry and luciferase activity analysis were used to detect the delivery of fusogenic erythrocyte ghost to deoxyribonucleic acid in AD293 cells and refractory cells, respectively. Transfection efficiency of fusogenic erythrocyte ghost in vivo was detected by confocal microscope. Vesicular stomatitis virus glycoprotein and erythrocyte ghost were effectively integrated, and fusogenic erythrocyte ghost was successfully prepared. deoxyribonucleic acid/polyethylenimine complexes form 100–300 nm particles. Fusogenic erythrocyte ghost can effectively incorporation deoxyribonucleic acid complexes. Confocal microscope observed red fluorescence close to blue fluorescence, indicating that labeled fusogenic erythrocyte ghost may trigger liver and spleen tissue endocytosis or fusion. A new delivery vector of fusogenic erythrocyte ghost was constructed. This system could enhance the delivery efficiency even in cells which refractory to conventional transfections in vitro.

Comparative efficacy and safety of vaccines to prevent seasonal influenza: A systematic review and network meta-analysis

Background

Influenza is one of the most common respiratory viral infections worldwide. Numerous vaccines are used to prevent influenza. Their selection should be informed by the best available evidence. We aimed to estimate the comparative efficacy and safety of seasonal influenza vaccines in children, adults and the elderly.

Methods

We conducted a systematic review and network meta-analysis (NMA). We searched the Cochrane Library Central Register of Controlled Trials, MEDLINE and EMBASE databases, and websites of regulatory agencies, through December 15th, 2020. We included placebo- or no vaccination-controlled, and head-to-head randomized clinical trials (RCTs). Pairs of reviewers independently screened the studies, abstracted the data, and appraised the risk of bias in accordance to the Cochrane Handbook for Systematic Reviews of Interventions. The primary outcome was laboratory-confirmed influenza. We also synthesized data for hospitalization, mortality, influenza-like illness (ILI), pneumonia or lower respiratory-tract disease, systemic and local adverse events (AEs). We estimated summary risk ratios (RR) using pairwise and NMA with random effects. This study is registered with PROSPERO, number CRD42018091895.

Findings

We identified 13,439 citations. A total of 231 RCTs were included after screening: 11 studies did not provide useful data for the analysis; 220 RCTs [100,677 children (< 18 years) and 329,127 adults (18-60 years) and elderly (≥ 61 years)] were included in the NMA. In adults and the elderly, all vaccines, except the trivalent inactivated intradermal vaccine (3-IIV ID), were more effective than placebo in reducing the risk of laboratory-confirmed influenza, with a RR between 0.33 (95% credible interval [CrI] 0.21-0.55) for trivalent inactivated high-dose (3-IIV HD) and 0.56 (95% CrI 0.41-0.74) for trivalent live-attenuated vaccine (3-LAIV). In adults and the elderly, compared with trivalent inactivated vaccine (3-IIV), no significant differences were found for any, except 3-LAIV, which was less efficacious [RR 1.41 (95% CrI 1.04-1.88)]. In children, compared with placebo, RR ranged between 0.13 (95% CrI 0.03-0.51) for trivalent inactivated vaccine adjuvanted with MF59/AS03 and 0.55 (95% CrI 0.36-0.83) for trivalent inactivated vaccine. Compared with 3-IIV, 3-LAIV and trivalent inactivated adjuvanted with MF59/AS03 were more efficacious [RR 0.52 (95% CrI 0.32-0.82) and RR 0.23 (95% CrI 0.06-0.87)] in reducing laboratory-confirmed influenza. With regard to safety, higher systemic AEs rates after vaccination with 3-IIV, 3-IIV HD, 3-IIV ID, 3-IIV MF59/AS03-adj, quadrivalent inactivated (4-IIV), quadrivalent adjuvanted (4-IIV MF59/AS03-adj), quadrivalent recombinant (4-RIV), 3-LAIV or quadrivalent live attenuated (4-LAIV) vaccines were noted in adults and the elderly [RR 1.5 (95% CrI 1.18-1.89) to 1.15 (95% CrI 1.06-1.23)] compared with placebo. In children, the systemic AEs rate after vaccination was not significantly higher than placebo.

Interpretation

All vaccines cumulatively achieved major reductions in the incidence of laboratory-confirmed influenza in children, adults, and the elderly. While the live-attenuated was more efficacious than the inactivated vaccine in children, many vaccine types can be used in adults and the elderly.

Funding

The directorate general of welfare, Lombardy region.

Developments in Vaccine Adjuvants

Vaccines, including subunit, recombinant, and conjugate vaccines, require the use of an immunostimulator/adjuvant for maximum efficacy. Adjuvants not only enhance the strength and longevity of immune responses but may also influence the type of response. In this chapter, we review the adjuvants that are available for use in human vaccines, such as alum, MF59, AS03, and AS01. We extensively discuss their composition, characteristics, mechanism of action, and effects on the immune system. Additionally, we summarize recent trends in adjuvant discovery, providing a brief overview of saponins, TLRs agonists, polysaccharides, nanoparticles, cytokines, and mucosal adjuvants.

Nanocarriers for Skin Applications: Where Do We Stand?

Skin penetration of active molecules for treatment of diverse diseases is a major field of research owing to the advantages associated with the skin like easy accessibility, reduced systemic-derived side effects, and increased therapeutic efficacy. Despite these advantages, dermal drug delivery is generally challenging due to the low skin permeability of therapeutics. Although various methods have been developed to improve skin penetration and permeation of therapeutics, they are usually aggressive and could lead to irreversible damage to the stratum corneum. Nanosized carrier systems represent an alternative approach for current technologies, with minimal damage to the natural barrier function of skin. In this Review, the use of nanoparticles to deliver drug molecules, genetic material, and vaccines into the skin is discussed. In addition, nanotoxicology studies and the recent clinical development of nanoparticles are highlighted to shed light on their potential to undergo market translation.

Intranasal vaccine: Factors to consider in research and development

Most existing vaccines for human use are administered by needle-based injection. Administering vaccines needle-free intranasally has numerous advantages over by needle-based injection, but there are only a few intranasal vaccines that are currently approved for human use, and all of them are live attenuated influenza virus vaccines. Clearly, there are immunological as well as non-immunological challenges that prevent vaccine developers from choosing the intranasal route of administration. We reviewed current approved intranasal vaccines and pipelines and described the target of intranasal vaccines, i.e. nose and lymphoid tissues in the nasal cavity. We then analyzed factors unique to intranasal vaccines that need to be considered when researching and developing new intranasal vaccines. We concluded that while the choice of vaccine formulations, mucoadhesives, mucosal and epithelial permeation enhancers, and ligands that target M-cells are important, safe and effective intranasal mucosal vaccine adjuvants are needed to successfully develop an intranasal vaccine that is not based on live-attenuated viruses or bacteria. Moreover, more effective intranasal vaccine application devices that can efficiently target a vaccine to lymphoid tissues in the nasal cavity as well as preclinical animal models that can better predict intranasal vaccine performance in clinical trials are needed to increase the success rate of intranasal vaccines in clinical trials.

Protective Efficacy in a Hamster Model of a Multivalent Vaccine for Human Visceral Leishmaniasis (MuLeVaClin) Consisting of the KMP11, LEISH-F3+, and LJL143 Antigens in Virosomes, Plus GLA-SE Adjuvant

Visceral leishmaniasis (VL) is the most severe clinical form of leishmaniasis, fatal if untreated. Vaccination is the most cost-effective approach to disease control; however, to date, no vaccines against human VL have been made available. This work examines the efficacy of a novel vaccine consisting of the Leishmania membrane protein KMP11, LEISH-F3+ (a recombinant fusion protein, composed of epitopes of the parasite proteins nucleoside hydrolase, sterol-24-c-methyltransferase, and cysteine protease B), and the sand fly salivary protein LJL143, in two dose ratios. The inclusion of the TLR4 agonist GLA-SE as an adjuvant, and the use of virosomes (VS) as a delivery system, are also examined. In a hamster model of VL, the vaccine elicited antigen-specific immune responses prior to infection with Leishmania infantum. Of note, the responses were greater when higher doses of KMP11 and LEISH-F3+ proteins were administered along with the GLA-SE adjuvant and/or when delivered within VS. Remarkably, hamsters immunized with the complete combination (i.e., all antigens in VS + GLA-SE) showed significantly lower parasite burdens in the spleen compared to those in control animals. This protection was underpinned by a more intense, specific humoral response against the KMP11, LEISH-F3+, and LJL143 antigens in vaccinated animals, but a significantly less intense antibody response to the pool of soluble Leishmania antigens (SLA). Overall, these results indicate that this innovative vaccine formulation confers protection against L. infantum infection, supporting the advancement of the vaccine formulation into process development and manufacturing and the conduction of toxicity studies towards future phase I human clinical trials.

Tapping the immunological imprints to design chimeric SARS-CoV-2 vaccine for elderly population

The impact of SARS-CoV-2 and COVID-19 disease susceptibility varies depending on the age and health status of an individual. Currently, there are more than 140 COVID-19 vaccines under development. However, the challenge will be to induce an effective immune response in the elderly population. Analysis of B cell epitopes indicates the minor role of the stalk domain of spike protein in viral neutralization due to low surface accessibility. Nevertheless, the accumulation of mutations in the receptor-binding domain (RBD) might reduce the vaccine efficacy in all age groups. We also propose the concept of chimeric vaccines based on the co-expression of SARS-CoV-2 spike and influenza hemagglutinin (HA) and matrix protein 1 (M1) proteins to generate chimeric virus-like particles (VLP). This review discusses the possible approaches by which influenza-specific memory repertoire developed during the lifetime of the elderly populations can converge to mount an effective immune response against the SARS-CoV-2 spike protein with the possibilities of designing single vaccines for COVID-19 and influenza. HighlightsImmunosenescence aggravates COVID-19 symptoms in elderly individuals.Low immunogenicity of SARS-CoV-2 vaccines in elderly population.Tapping the memory T and B cell repertoire in elderly can enhance vaccine efficiency.Chimeric vaccines can mount effective immune response against COVID-19 in elderly.Chimeric vaccines co-express SARS-CoV-2 spike and influenza HA and M1 proteins.

An Overview of Nanocarrier-Based Adjuvants for Vaccine Delivery

The development of vaccines is one of the most significant medical accomplishments which has helped to eradicate a large number of diseases. It has undergone an evolutionary process from live attenuated pathogen vaccine to killed whole organisms or inactivated toxins (toxoids), each of them having its own advantages and disadvantages. The crucial parameters in vaccination are the generation of memory response and protection against infection, while an important aspect is the effective delivery of antigen in an intelligent manner to evoke a robust immune response. In this regard, nanotechnology is greatly contributing to developing efficient vaccine adjuvants and delivery systems. These can protect the encapsulated antigen from the host’s in-vivo environment and releasing it in a sustained manner to induce a long-lasting immunostimulatory effect. In view of this, the present review article summarizes nanoscale-based adjuvants and delivery vehicles such as viral vectors, virus-like particles and virosomes; non-viral vectors namely nanoemulsions, lipid nanocarriers, biodegradable and non-degradable nanoparticles, calcium phosphate nanoparticles, colloidally stable nanoparticles, proteosomes; and pattern recognition receptors covering c-type lectin receptors and toll-like receptors.

New GMP manufacturing processes to obtain thermostable HIV-1 gp41 virosomes under solid forms for various mucosal vaccination routes

The main objective of the MACIVIVA European consortium was to develop new Good Manufacturing Practice pilot lines for manufacturing thermostable vaccines with stabilized antigens on influenza virosomes as enveloped virus-like particles. The HIV-1 gp41-derived antigens anchored in the virosome membrane, along with the adjuvant 3M-052 (TLR7/8 agonist) on the same particle, served as a candidate vaccine for the proof of concept for establishing manufacturing processes, which can be directly applied or adapted to other virosomal vaccines or lipid-based particles. Heat spray-dried powders suitable for nasal or oral delivery, and freeze-dried sublingual tablets were successfully developed as solid dosage forms for mucosal vaccination. The antigenic properties of vaccinal antigens with key gp41 epitopes were maintained, preserving the original immunogenicity of the starting liquid form, and also when solid forms were exposed to high temperature (40 °C) for up to 3 months, with minimal antigen and adjuvant content variation. Virosomes reconstituted from the powder forms remained as free particles with similar size, virosome uptake by antigen-presenting cells in vitro was comparable to virosomes from the liquid form, and the presence of excipients specific to each solid form did not prevent virosome transport to the draining lymph nodes of immunized mice. Virosome integrity was also preserved during exposure to <−15 °C, mimicking accidental freezing conditions. These “ready to use and all-in-one” thermostable needle-free virosomal HIV-1 mucosal vaccines offer the advantage of simplified logistics with a lower dependence on the cold chain during shipments and distribution.

Toward precision adjuvants: optimizing science and safety

PURPOSE OF REVIEW

The gradual replacement of inactivated whole cell and live attenuated vaccines with subunit vaccines has generally reduced reactogenicity but in many cases also immunogenicity. Although only used when necessary, adjuvants can be key to vaccine dose/antigen-sparing, broadening immune responses to variable antigens, and enhancing immunogenicity in vulnerable populations with distinct immunity. Licensed vaccines contain an increasing variety of adjuvants, with a growing pipeline of adjuvanted vaccines under development.

RECENT FINDINGS

Most adjuvants, including Alum, Toll-like receptor agonists and oil-in-water emulsions, activate innate immunity thereby altering the quantity and quality of an adaptive immune response. Adjuvants activate leukocytes, and induce mediators (e.g., cytokines, chemokines, and prostaglandin-E2) some of which are biomarkers for reactogenicity, that is, induction of local/systemic side effects. Although there have been safety concerns regarding a hypothetical risk of adjuvants inducing auto-immunity, such associations have not been established. As immune responses vary by population (e.g., age and sex), adjuvant research now incorporates principles of precision medicine. Innovations in adjuvant research include use of human in vitro models, immuno-engineering, novel delivery systems, and systems biology to identify biomarkers of safety and adjuvanticity.

SUMMARY

Adjuvants enhance vaccine immunogenicity and can be associated with reactogenicity. Novel multidisciplinary approaches hold promise to accelerate and de-risk targeted adjuvant discovery and development. VIDEO ABSTRACT: http://links.lww.com/MOP/A53.

Recent Advances in Nanovaccines Using Biomimetic Immunomodulatory Materials

The development of vaccines plays a vital role in the effective control of several fatal diseases. However, effective prophylactic and therapeutic vaccines have yet to be developed for completely curing deadly diseases, such as cancer, malaria, HIV, and serious microbial infections. Thus, suitable vaccine candidates need to be designed to elicit appropriate immune responses. Nanotechnology has been found to play a unique role in the design of vaccines, providing them with enhanced specificity and potency. Nano-scaled materials, such as virus-like particles, liposomes, polymeric nanoparticles (NPs), and protein NPs, have received considerable attention over the past decade as potential carriers for the delivery of vaccine antigens and adjuvants, due to their beneficial advantages, like improved antigen stability, targeted delivery, and long-time release, for which antigens/adjuvants are either encapsulated within, or decorated on, the NP surface. Flexibility in the design of nanomedicine allows for the programming of immune responses, thereby addressing the many challenges encountered in vaccine development. Biomimetic NPs have emerged as innovative natural mimicking biosystems that can be used for a wide range of biomedical applications. In this review, we discuss the recent advances in biomimetic nanovaccines, and their use in anti-bacterial therapy, anti-HIV therapy, anti-malarial therapy, anti-melittin therapy, and anti-tumor immunity.

Vaccine adjuvants: Understanding the structure and mechanism of adjuvanticity

In conjugate, inactivated, recombinant, and toxoid vaccines, adjuvants are extensively and essentially used for enhanced and long-lasting protective immune responses. Depending on the type of diseases and immune responses required, adjuvants with different design strategies are developed. With aluminum salt-based adjuvants as the most used ones in commercial vaccines, other limited adjuvants, e.g., AS01, AS03, AS04, CpG ODN, and MF59, are used in FDA-approved vaccines for human use. In this paper, we review the uses of different adjuvants in vaccines including the ones used in FDA-approved vaccines and vaccines under clinical investigations. We discuss how adjuvants with different formulations could affect the magnitude and quality of adaptive immune response for optimized protection against specific pathogens. We emphasize the molecular mechanisms of various adjuvants, with the aim to establish structure-activity relationships (SARs) for designing more effective and safer adjuvants for both preventative and therapeutic vaccines.

Subunit-based mucosal vaccine delivery systems for pulmonary delivery - Are they feasible?

Pulmonary infections are the most common cause of death globally. However, the development of mucosal vaccines that provide protective immunity against respiratory pathogens are limited. In contrast to needle-based vaccines, efficient vaccines that are delivered via noninvasive mucosal routes (such as via the lungs and nasal passage) produce both antigen-specific local mucosal IgA and systemic IgG protective antibodies. One major challenge in the development of pulmonary vaccines using subunit antigens however, is the production of optimal immune responses. Subunit vaccines therefore rely upon use of adjuvants to potentiate immune responses. While the lack of suitable mucosal adjuvants has hindered progress in the development of efficient pulmonary vaccines, particle-based systems can provide an alternative approach for the safe and efficient delivery of subunit vaccines. In particular, the rational engineering of particulate vaccines with optimal physicochemical characteristics can produce long-term protective immunity. These protect antigens against enzymatic degradation, target antigen presenting cells and initiate optimal humoral and cellular immunity. This review will discuss our current understanding of pulmonary immunology and developments in fabricating particle characteristics that may evoke potent and durable pulmonary immunity.

Novel application of trimethyl chitosan as an adjuvant in vaccine delivery

The application of natural carbohydrate polysaccharides for antigen delivery and its adjuvanation potential has garnered interest in the scientific community in the recent years. These biomaterials are considered favorable candidates for adjuvant development due to their desirable properties like enormous bioavailability, non-toxicity, biodegradability, stability, affordability, and immunostimulating ability. Chitosan is the one such extensively studied natural polymer which has been appreciated for its excellent applications in pharmaceuticals. Trimethyl chitosan (TMC), a derivative of chitosan, possesses these properties. In addition it has the properties of high aqueous solubility, high charge density, mucoadhesive, permeation enhancing (ability to cross tight junction), and stability over a range of ionic conditions which makes the spectrum of its applicability much broader. It has also been seen to perform analogously to alum, complete Freund’s adjuvant, incomplete Freund’s adjuvant, and cyclic guanosine monophosphate adjuvanation, which justifies its role as a potent adjuvant. Although many review articles detailing the applications of chitosan in vaccine delivery are available, a comprehensive review of the applications of TMC as an adjuvant is not available to date. This article provides a comprehensive overview of structural and chemical properties of TMC which affect its adjuvant characteristics; the efficacy of various delivery routes for TMC antigen combination; and the recent advances in the elucidation of its mechanism of action.

Pre-clinical antigenicity studies of an innovative multivalent vaccine for human visceral leishmaniasis

The notion that previous infection by Leishmania spp. in endemic areas leads to robust anti-Leishmania immunity, supports vaccination as a potentially effective approach to prevent disease development. Nevertheless, to date there is no vaccine available for human leishmaniasis. We optimized and assessed in vivo the safety and immunogenicity of an innovative vaccine candidate against human visceral leishmaniasis (VL), consisting of Virus-Like Particles (VLP) loaded with three different recombinant proteins (LJL143 from Lutzomyia longipalpis saliva as the vector-derived (VD) component, and KMP11 and LeishF3+, as parasite-derived (PD) antigens) and adjuvanted with GLA-SE, a TLR4 agonist. No apparent adverse reactions were observed during the experimental time-frame, which together with the normal hematological parameters detected seems to point to the safety of the formulation. Furthermore, measurements of antigen-specific cellular and humoral responses, generally higher in immunized versus control groups, confirmed the immunogenicity of the vaccine formulation. Interestingly, the immune responses against the VD protein were reproducibly more robust than those elicited against leishmanial antigens, and were apparently not caused by immunodominance of the VD antigen. Remarkably, priming with the VD protein alone and boosting with the complete vaccine candidate contributed towards an increase of the immune responses to the PD antigens, assessed in the form of increased ex vivo CD4+ and CD8+ T cell proliferation against both the PD antigens and total Leishmania antigen (TLA). Overall, our immunogenicity data indicate that this innovative vaccine formulation represents a promising anti-Leishmania vaccine whose efficacy deserves to be tested in the context of the "natural infection".

Nanoparticle Vaccines Adopting Virus-like Features for Enhanced Immune Potentiation

Synthetic nanoparticles play an increasingly significant role in vaccine design and development as many nanoparticle vaccines show improved safety and efficacy over conventional formulations. These nanoformulations are structurally similar to viruses, which are nanoscale pathogenic organisms that have served as a key selective pressure driving the evolution of our immune system. As a result, mechanisms behind the benefits of nanoparticle vaccines can often find analogue to the interaction dynamics between the immune system and viruses. This review covers the advances in vaccine nanotechnology with a perspective on the advantages of virus mimicry towards immune potentiation. It provides an overview to the different types of nanomaterials utilized for nanoparticle vaccine development, including functionalization strategies that bestow nanoparticles with virus-like features. As understanding of human immunity and vaccine mechanisms continue to evolve, recognizing the fundamental semblance between synthetic nanoparticles and viruses may offer an explanation for the superiority of nanoparticle vaccines over conventional vaccines and may spur new design rationales for future vaccine research. These nanoformulations are poised to provide solutions towards pressing and emerging human diseases.

Pulmonary Delivery of Virosome-Bound Antigen Enhances Antigen-Specific CD4+ T Cell Proliferation Compared to Liposome-Bound or Soluble Antigen

Pulmonary administration of biomimetic nanoparticles loaded with antigen may represent an effective strategy to directly modulate adaptive immune responses in the respiratory tract. Depending on the design, virosomes may not only serve as biomimetic antigen carriers but are also endowed with intrinsic immune-stimulatory properties. We designed fluorescently labeled influenza-derived virosomes and liposome controls coupled to the model antigen ovalbumin to investigate uptake, phenotype changes, and antigen processing by antigen-presenting cells exposed to such particles in different respiratory tract compartments. Both virosomes and liposomes were captured by pulmonary macrophages and dendritic cells alike and induced activation in particle-bearing cells by upregulation of costimulatory markers such as CD40, CD80, CD86, PD-L1, PD-L2, and ICOS-L. Though antigen processing and accumulation of both coupled and soluble antigen was similar between virosomes and liposomes, only ovalbumin-coupled virosomes generated a strong antigen-specific CD4⁺ T cell proliferation. Pulmonary administrated antigen-coupled virosomes therefore effectively induced adaptive immune responses and may be utilized in novel preventive or therapeutic approaches in the respiratory tract.

Virosome-bound antigen enhances DC-dependent specific CD4+ T cell stimulation, inducing a Th1 and Treg profile in vitro

There is considerable interest to develop antigen-carriers for immune-modulatory clinical applications, but insufficient information is available on their effects on antigen-presenting cells. We employed virosomes coupled to ovalbumin (OVA) to study their interaction with murine bone marrow-derived dendritic cells (BMDCs) and modulation of downstream T cell responses. BMDCs were treated in vitro with virosomes or liposomes prior to determining BMDC phenotype, viability, and intracellular trafficking. Antigen-specific CD4⁺ T cell activation was measured by co-culture of BMDCs with DO11.10 CD4⁺ T cells. Compared to liposomes, virosomes were rapidly taken up. Neither nanocarrier type affected BMDC viability, nor did a moderate degree of activation differ for markers such as CD40, CD80, CD86. Virosome uptake occurred via clathrin-mediated endocytosis and phagocytosis, with co-localization in late endosomes. Only BMDCs treated with OVA-coupled virosomes induced enhanced OVA-specific CD4⁺ T cell proliferation. Antigen-coupled virosomes are endowed with an intrinsic ability to modulate DC-dependent adaptive immune responses.

Vaccine technologies: From whole organisms to rationally designed protein assemblies

Vaccines have been the single most significant advancement in public health, preventing morbidity and mortality in millions of people annually. Vaccine development has traditionally focused on whole organism vaccines, either live attenuated or inactivated vaccines. While successful for many different infectious diseases whole organisms are expensive to produce, require culture of the infectious agent, and have the potential to cause vaccine associated disease in hosts. With advancing technology and a desire to develop safe, cost effective vaccine candidates, the field began to focus on the development of recombinantly expressed antigens known as subunit vaccines. While more tolerable, subunit vaccines tend to be less immunogenic. Attempts have been made to increase immunogenicity with the addition of adjuvants, either immunostimulatory molecules or an antigen delivery system that increases immune responses to vaccines. An area of extreme interest has been the application of nanotechnology to vaccine development, which allows for antigens to be expressed on a particulate delivery system. One of the most exciting examples of nanovaccines are rationally designed protein nanoparticles. These nanoparticles use some of the basic tenants of structural biology, biophysical chemistry, and vaccinology to develop protective, safe, and easily manufactured vaccines. Rationally developed nanoparticle vaccines are one of the most promising candidates for the future of vaccine development.

Biomaterials-Based Vaccination Strategies for the Induction of CD8+T Cell Responses

Natural and synthetic biomaterials are increasingly being used for the development of vaccines and immunotherapies as alternatives to traditional live-attenuated formulations due to their improved safety profiles and no risk of reversion to virulence. Polymeric materials in particular enjoy attention due to the ease of fabrication, control over physicochemical properties, and their wide range of immunogenicity. While the majority of studies focus on inducing protective antibody responses, in recent years, materials-based strategies for the delivery of antigens and immunomodulators to improve CD8⁺T cell immunity against infectious and non-infectious diseases have gained momentum. Notably, platforms based on polymeric nanoparticles, liposomes, micelles, virus-like particles, self-assembling peptides and peptidomimetics, and multilayer thin films show considerable promise in preclinical studies. In this Review, we first introduce the concepts of CD8⁺T cell activation, effector and memory functions, and cytotoxic activity, followed by vaccine design for eliciting robust and protective long-lived CD8⁺T cell immunity. We then discuss different materials-based vaccines developed in the past decade to elicit CD8⁺T cell responses based on molecular composition or fabrication methods and conclude with a summary and glimpse at the future trends in this area.

A Triple Co-Culture Model of the Human Respiratory Tract to Study Immune-Modulatory Effects of Liposomes and Virosomes

The respiratory tract with its ease of access, vast surface area and dense network of antigen-presenting cells (APCs) represents an ideal target for immune-modulation. Bio-mimetic nanocarriers such as virosomes may provide immunomodulatory properties to treat diseases such as allergic asthma. In our study we employed a triple co-culture model of epithelial cells, macrophages and dendritic cells to simulate the human airway barrier. The epithelial cell line 16HBE was grown on inserts and supplemented with human blood monocyte-derived macrophages (MDMs) and dendritic cells (MDDCs) for exposure to influenza virosomes and liposomes. Additionally, primary human nasal epithelial cells (PHNEC) and EpCAM⁺ epithelial progenitor cell mono-cultures were utilized to simulate epithelium from large and smaller airways, respectively. To assess particle uptake and phenotype change, cell cultures were analyzed by flow cytometry and pro-inflammatory cytokine concentrations were measured by ELISA. All cell types internalized virosomes more efficiently than liposomes in both mono- and co-cultures. APCs like MDMs and MDDCs showed the highest uptake capacity. Virosome and liposome treatment caused a moderate degree of activation in MDDCs from mono-cultures and induced an increased cytokine production in co-cultures. In epithelial cells, virosome uptake was increased compared to liposomes in both mono- and co-cultures with EpCAM⁺ epithelial progenitor cells showing highest uptake capacity. In conclusion, all cell types successfully internalized both nanocarriers with virosomes being taken up by a higher proportion of cells and at a higher rate inducing limited activation of MDDCs. Thus virosomes may represent ideal carrier antigen systems to modulate mucosal immune responses in the respiratory tract without causing excessive inflammatory changes.

Glycolysis inhibition as a cancer treatment and its role in an anti-tumour immune response

Increased glycolysis is the main source of energy supply in cancer cells that use this metabolic pathway for ATP generation. Altered energy metabolism is a biochemical fingerprint of cancer cells that represents one of the "hallmarks of cancer". The immune system can prevent tumour growth by eliminating cancer cells but this editing process ultimately results in poorly immunogenic cells remaining allowing for unchallenged tumour growth. In this review we look at the glycolysis pathway as a target for cancer treatments. We also examine the interplay between the glycolysis modulation and the immune response as an anti-cancer therapy.

Innate signaling by mycobacterial cell wall components and relevance for development of adjuvants for subunit vaccines

INTRODUCTION

Pathogen recognition receptors (PRRs) recognize pathogen-associated molecular patterns, triggering the induction of inflammatory innate responses and contributing to the development of specific adaptive immune responses. Novel adjuvants have been developed based on agonists of PRRs. Areas covered: Lipid pathogen-associated molecular patterns (PAMPs) present in the cell wall of mycobacteria are revised, with emphasis on agonists of C-type lectin receptors, signaling pathways, and preclinical data supporting their use as novel adjuvants inducing cell-mediated immune responses. Their potential use as lipid antigens in novel tuberculosis subunit vaccines is also discussed. Expert commentary: Few adjuvants are licensed for human use and mainly favour antibody-mediated protective immunity. Use of lipid PAMPs that trigger cell-mediated immune responses could lead to the development of adjuvants for vaccines against intracellular pathogens and cancer.

Highly sensitive ligand-binding assays in pre-clinical and clinical applications: immuno-PCR and other emerging techniques

Recombinant DNA technology and corresponding innovations in molecular biology, chemistry and medicine have led to novel therapeutic biomacromolecules as lead candidates in the pharmaceutical drug development pipelines. While monoclonal antibodies and other proteins provide therapeutic potential beyond the possibilities of small molecule drugs, the concomitant demand for supportive bioanalytical sample testing creates multiple novel challenges. For example, intact macromolecules can usually not be quantified by mass-spectrometry without enzymatic digestion and isotopically labeled internal standards are costly and/or difficult to prepare. Classical ELISA-type immunoassays, on the other hand, often lack the sensitivity required to obtain pharmacokinetics of low dosed drugs or pharmacodynamics of suitable biomarkers. Here we summarize emerging state-of-the-art ligand-binding assay technologies for pharmaceutical sample testing, which reveal enhanced analytical sensitivity over classical ELISA formats. We focus on immuno-PCR, which combines antibody specificity with the extremely sensitive detection of a tethered DNA marker by quantitative PCR, and alternative nucleic acid-based technologies as well as methods based on electrochemiluminescence or single-molecule counting. Using case studies, we discuss advantages and drawbacks of these methods for preclinical and clinical sample testing.

Virosome engineering of colloidal particles and surfaces: bioinspired fusion to supported lipid layers

Immunostimulating reconstituted influenza virosomes (IRIVs) are liposomes with functional viral envelope glycoproteins: influenza virus hemagglutinin (HA) and neuraminidase intercalated in the phospholipid bilayer. Here we address the fusion of IRIVs to artificial supported lipid membranes assembled on polyelectrolyte multilayers on both colloidal particles and planar substrates. The R18 assay is used to prove the IRIV fusion in dependence of pH, temperature and HA concentration. IRIVs display a pH-dependent fusion mechanism, fusing at low pH in analogy to the influenza virus. The pH dependence is confirmed by the Quartz Crystal Microbalance technique. Atomic Force Microscopy imaging shows that at low pH virosomes are integrated in the supported membrane displaying flattened features and a reduced vertical thickness. Virosome fusion offers a new strategy for transferring biological functions on artificial supported membranes with potential applications in targeted delivery and sensing.

Recent advances in vaccine delivery

The field of vaccination is moving from the use of attenuated or inactivated pathogens to safer but less immunogenic protein and peptide antigens, which require stronger adjuvant compositions. Antigen delivery carriers appear to play an important role in vaccine development, providing not only antigen protection and controlled release but also an intrinsic adjuvant potential. Among them, carriers based on polymers and lipids are the most representative ones. Patent applications in this area have disclosed, either the design and preparation methods for new biocompatible antigen delivery systems or the application of the previously developed systems for the delivery of novel antigens. Some of them have also reported the use of these technologies for modern therapeutic vaccination approaches.

Generation and characterization of a trackable plant-made influenza H5 virus-like particle (VLP) containing enhanced green fluorescent protein (eGFP)

Medicago, Inc. has developed an efficient virus-like particle (VLP) vaccine production platform using the Nicotiana benthamiana expression system, and currently has influenza-based products targeting seasonal/pandemic hemagglutinin (HA) proteins in advanced clinical trials. We wished to generate a trackable HA-based VLP that would allow us to study both particle assembly in plants and VLP interactions within the mammalian immune system. To this end, a fusion protein was designed, composed of H5 (from influenza A/Indonesia/05/2005 [H5N1]) with enhanced green fluorescent protein (eGFP). Expression of H5-eGFP in N. benthamiana produced brightly fluorescent ∼160 nm particles resembling H5-VLPs. H5-eGFP-VLPs elicited anti-H5 serologic responses in mice comparable to those elicited by H5-VLPs in almost all assays tested (hemagglutination inhibition/IgG(total)/IgG1/IgG2b/IgG2a:IgG1 ratio), as well as a superior anti-GFP IgG response (mean optical density = 2.52 ± 0.16 sem) to that elicited by soluble GFP (mean optical density = 0.12 ± 0.06 sem). Confocal imaging of N. benthamiana cells expressing H5-eGFP displayed large fluorescent accumulations at the cell periphery, and draining lymph nodes from mice given H5-eGFP-VLPs via footpad injection demonstrated bright fluorescence shortly after administration (10 min), providing proof of concept that the H5-eGFP-protein/VLPs could be used to monitor both VLP assembly and immune trafficking. Given these findings, this novel fluorescent reagent will be a powerful tool to gain further fundamental insight into the biology of influenza VLP vaccines.

Establishment and first characterization of a sublingual epithelial and immune cell co-culture model

We describe here the establishment and first characterization of a co-culture model of human epithelial sublingual cells (HO-1-u-1 cell line) and human dendritic cells derived from human peripheral blood monocytes (PBMC). Cell culture conditions for HO-1-u-1 cells were optimized. First characterization of phenotypic features by electron microscopy and fluorescence imaging revealed resemblance to sublingual tissue specimen from healthy donors. Successful co-culturing of epithelial and dendritic cells (DCs) was confirmed by confocal laser scanning microscopy. Stimulation of HO-1-u1 cells alone and the epithelial/DC co-culture by incubation with liposomes, virosomes and influenza virus lead reproducibly to the release of inflammatory cytokine GM-CSF. This co-culture model may be suitable for elucidation of mechanisms involved in the immune response at the sublingual epithelium as well as for the evaluation of novel topical vaccines, potentially replacing cumbersome ex vivo and in vivo methods currently in place.

An H1-H3 chimeric influenza virosome confers complete protection against lethal challenge with PR8 (H1N1) and X47 (H3N2) viruses in mice

Annual health threats and economic damages caused by influenza virus are still a main concern of the World Health Organization and other health departments all over the world. An influenza virosome is a highly efficient immunomodulating carrier mimicking the natural antigen presentation pathway and has shown an excellent tolerability profile due to its biocompatibility and purity. The major purpose of this study was to construct a new chimeric virosome influenza vaccine containing hemagglutinin (HA) and neuraminidase (NA) proteins derived from the A/PR/8/1934 (H1N1) (PR8) and A/X/47 (H3N2) (X47) viruses, and to evaluate its efficacy as a vaccine candidate in mice. A single intramuscular vaccination with the chimeric virosomes provided complete protection against lethal challenge with the PR8 and X47 viruses. The chimeric virosomes induced high IgG antibody responses as well as hemagglutination inhibition (HAI) titers. HAI titers following the chimeric virosome vaccination were at the same level as the whole inactivated influenza vaccine. Mice immunized with the chimeric virosomes displayed considerably less weight loss and exhibited significantly reduced viral load in their lungs compared with the controls. The chimeric virosomes can be used as an innovative vaccine formulation to confer protection against a broad range of influenza viruses.

Vaccine instability in the cold chain: mechanisms, analysis and formulation strategies

Instability of vaccines often emerges as a key challenge during clinical development (lab to clinic) as well as commercial distribution (factory to patient). To yield stable, efficacious vaccine dosage forms for human use, successful formulation strategies must address a combination of interrelated topics including stabilization of antigens, selection of appropriate adjuvants, and development of stability-indicating analytical methods. This review covers key concepts in understanding the causes and mechanisms of vaccine instability including (1) the complex and delicate nature of antigen structures (e.g., viruses, proteins, carbohydrates, protein-carbohydrate conjugates, etc.), (2) use of adjuvants to further enhance immune responses, (3) development of physicochemical and biological assays to assess vaccine integrity and potency, and (4) stabilization strategies to protect vaccine antigens and adjuvants (and their interactions) during storage. Despite these challenges, vaccines can usually be sufficiently stabilized for use as medicines through a combination of formulation approaches combined with maintenance of an efficient cold chain (manufacturing, distribution, storage and administration). Several illustrative case studies are described regarding mechanisms of vaccine instability along with formulation approaches for stabilization within the vaccine cold chain. These include live, attenuated (measles, polio) and inactivated (influenza, polio) viral vaccines as well as recombinant protein (hepatitis B) vaccines.

Influenza virosomes as vaccine adjuvant and carrier system

The basic concept of virosomes is the controlled in vitro assembly of virus-like particles from purified components. The first generation of influenza virosomes developed two decades ago is successfully applied in licensed vaccines, providing a solid clinical safety and efficacy track record for the technology. In the meantime, a second generation of influenza virosomes has evolved as a carrier and adjuvant system, which is currently applied in preclinical and clinical stage vaccine candidates targeting various prophylactic and therapeutic indications. The inclusion of additional components to optimize particle assembly, to stabilize the formulations, or to enhance the immunostimulatory properties have further improved and broadened the applicability of the platform.

Inactivated and adjuvanted influenza vaccines

Inactivated influenza vaccines are produced every year to fight against the seasonal epidemics of influenza. Despite the nonoptimal coverage, even in subjects at risk like the elderly, pregnant women, etc., these vaccines significantly reduce the burden of mortality and morbidity linked to the influenza infection. Importantly, these vaccines have also contributed to reduce the impact of the last pandemics. Nevertheless, the performance of these vaccines can be improved mainly in those age groups, like children and the elderly, in which their efficacy is suboptimal. The use of adjuvants has proven effective to this scope. Oil-in-water adjuvants like MF59 and AS03 have been licensed and widely used, and shown efficacious in preventing influenza infection in the last pandemic. MF59-adjuvanted inactivated vaccine was more efficacious than non-adjuvanted vaccine in preventing influenza infection in young children and in reducing hospitalization due to the influenza infection in the elderly. Other adjuvants are now at different stages of development and some are being tested in clinical trials. The perspective remains to improve the way inactivated vaccines are prepared and to accelerate their availability, mainly in the case of influenza pandemics, and to enhance their efficacy/effectiveness for a more successful impact at the public health level.

Key roles of adjuvants in modern vaccines

Vaccines containing novel adjuvant formulations are increasingly reaching advanced development and licensing stages, providing new tools to fill previously unmet clinical needs. However, many adjuvants fail during product development owing to factors such as manufacturability, stability, lack of effectiveness, unacceptable levels of tolerability or safety concerns. This Review outlines the potential benefits of adjuvants in current and future vaccines and describes the importance of formulation and mechanisms of action of adjuvants. Moreover, we emphasize safety considerations and other crucial aspects in the clinical development of effective adjuvants that will help facilitate effective next-generation vaccines against devastating infectious diseases.

Proteomic analyses of different human tumour-derived chaperone-rich cell lysate (CRCL) anti-cancer vaccines reveal antigen content and strong similarities amongst the vaccines along with a basis for CRCL's unique structure: CRCL vaccine proteome leads to unique structure

PURPOSE

The aim of this paper was to compare protein content of chaperone-rich cell lysate (CRCL) anti-cancer vaccines prepared from human tumours of different histological origins to evaluate the uniformity of their protein content.

MATERIALS AND METHODS

Clinical grade CRCL was prepared under Good Manufacturing Practice (GMP) conditions from surgically resected human tumours (colorectal cancer, glioblastoma, non-small cell lung cancer, ovarian cancer). Protein samples were separated by SDS-PAGE and slices cut from gels for protease digestion followed by mass spectrometry analysis. Proteins were identified, and the content assessed by gene ontogeny/networking programmatic computation. CRCL preparations were also analysed by nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM).

RESULTS

We identified between 200 and 550 proteins in the various CRCL preparations. Gene ontogeny analysis indicated that the vaccines showed clear relationships, despite different tumour origins. A total of 95 proteins were common to all the CRCLs. Networking analyses implicated heat shock proteins in antigen processing pathways, and showed connections to the cytoskeletal network. We found that CRCL vaccines showed a particulate structure by NTA, and TEM revealed an extended fence-like structural network in CRCL, with regions that were microns in size.

CONCLUSIONS

We conclude that it is feasible to prepare and characterise CRCL from a variety of different tissue sources; a substantial portion of the protein content is identical among the different CRCLs, while the overall compositions also suggest high overlaps in functional categories. The protein content indicates the presence of antigens and implies a potential structure, which we believe may play a role in CRCL's ability to stimulate innate antigen presenting cell activation.

Randomized Phase I: Safety, Immunogenicity and Mucosal Antiviral Activity in Young Healthy Women Vaccinated with HIV-1 Gp41 P1 Peptide on Virosomes

Mucosal antibodies harboring various antiviral activities may best protect mucosal surfaces against early HIV-1 entry at mucosal sites and they should be ideally induced by prophylactic HIV-1 vaccines for optimal prevention of sexually transmitted HIV-1. A phase I, double-blind, randomized, placebo-controlled trial was conducted in twenty-four healthy HIV-uninfected young women. The study objectives were to assess the safety, tolerability and immunogenicity of virosomes harboring surface HIV-1 gp41-derived P1 lipidated peptides (MYM-V101). Participants received placebo or MYM-V101 vaccine at 10 μg/dose or 50 μg/dose intramuscularly at week 0 and 8, and intranasally at week 16 and 24. MYM-V101 was safe and well-tolerated at both doses administered by the intramuscular and intranasal routes, with the majority of subjects remaining free of local and general symptoms. P1-specific serum IgGs and IgAs were induced in all high dose recipients after the first injection. After the last vaccination, vaginal and rectal P1-specific IgGs could be detected in all high dose recipients. Approximately 63% and 43% of the low and high dose recipients were respectively tested positive for vaginal P1-IgAs, while 29% of the subjects from the high dose group tested positive for rectal IgAs. Serum samples had total specific IgG and IgA antibody concentrations ≥ 0.4 μg/mL, while mucosal samples were usually below 0.01 μg/mL. Vaginal secretions from MYM-V101 vaccinated subjects were inhibiting HIV-1 transcytosis but had no detectable neutralizing activity. P1-specific Th1 responses could not be detected on PBMC. This study demonstrates the excellent safety and tolerability of MYM-V101, eliciting systemic and mucosal antibodies in the majority of subjects. Vaccine-induced mucosal anti-gp41 antibodies toward conserved gp41 motifs were harboring HIV-1 transcytosis inhibition activity and may contribute to reduce sexually-transmitted HIV-1.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01084343.

Vaccination for the prevention and treatment of breast cancer with special focus on Her-2/neu peptide vaccines

Immunologic interventions in a subset of breast cancer patients represent a well-established therapeutic approach reflecting individualized treatment modalities. Thus, the therapeutic administration of monoclonal antibodies targeting tumor-associated antigens (TAA), such as Her-2/neu, represents a milestone in cancer treatment. However, passive antibody administration suffers from several drawbacks, including frequency and long duration of treatment. These undesirables may be avoidable in an approach based on generating active immune responses against these same targets. Only recently has the significance of tumors in relation to their microenvironments been understood as essential for creating an effective cancer vaccine. In particular, the immune system plays an important role in suppressing or promoting tumor formation and growth. Therefore, activation of appropriate triggers (such as induction of Th1 cells, CD8+ T cells, and suppression of regulatory cells in combination with generation of antibodies with anti-tumor activity) is a desirable goal. Current vaccination approaches have concentrated on therapeutic vaccines using certain TAA. Many cancer antigens, including breast cancer antigens, have been described and also given priority ranking for use as vaccine antigens by the US National Cancer Institute. One of the TAA antigens which has been thoroughly examined in numerous trials is Her-2/neu. This review will discuss delivery systems for this antigen with special focus on T and B cell peptide vaccines. Attention will be given to their advantages and limitations, as well as the use of certain adjuvants to improve anti-cancer responses.

Design of novel vaccines based on virus-like particles or chimeric virions

Virus-like particles (VLPs) are formed by viral structural proteins that, when overexpressed, spontaneously self-assemble into particles that are antigenically indistinguishable from infectious virus or subviral particles. VLPs are appealing as vaccine candidates because their inherent properties (i.e., virus-sized, multimeric antigens, highly organised and repetitive structure, not infectious) are suitable for the induction of safe and efficient humoral and cellular immune responses. VLP-based vaccines have already been licensed for human and veterinary use, and many more vaccine candidates are currently in late stages of evaluation. Moreover, the development of VLPs as platforms for foreign antigen display has further broadened their potential applicability both as prophylactic and therapeutic vaccines. This chapter provides an overview on the design and use of VLPs for the development of new generation vaccines.

Virus-like particles as a highly efficient vaccine platform: diversity of targets and production systems and advances in clinical development

Virus-like particles (VLPs) are a class of subunit vaccines that differentiate themselves from soluble recombinant antigens by stronger protective immunogenicity associated with the VLP structure. Like parental viruses, VLPs can be either non-enveloped or enveloped, and they can form following expression of one or several viral structural proteins in a recombinant heterologous system. Depending on the complexity of the VLP, it can be produced in either a prokaryotic or eukaryotic expression system using target-encoding recombinant vectors, or in some cases can be assembled in cell-free conditions. To date, a wide variety of VLP-based candidate vaccines targeting various viral, bacterial, parasitic and fungal pathogens, as well as non-infectious diseases, have been produced in different expression systems. Some VLPs have entered clinical development and a few have been licensed and commercialized. This article reviews VLP-based vaccines produced in different systems, their immunogenicity in animal models and their status in clinical development.