Mucosal Vaccine Development Based on Liposome Technology

Mucosal Vaccine Approaches for Prevention of HIV and SIV Transmission

Optimal protective immunity to HIV will likely require that plasma cells, memory B cells and memory T cells be stationed in mucosal tissues at portals of viral entry. Mucosal vaccine administration is more effective than parenteral vaccine delivery for this purpose. The challenge has been to achieve efficient vaccine uptake at mucosal surfaces, and to identify safe and effective adjuvants, especially for mucosally administered HIV envelope protein immunogens. Here, we discuss strategies used to deliver potential HIV vaccine candidates in the intestine, respiratory tract, and male and female genital tract of humans and nonhuman primates. We also review mucosal adjuvants, including Toll-like receptor agonists, which may adjuvant both mucosal humoral and cellular immune responses to HIV protein immunogens.

Liposomal nanoparticle-based conserved peptide influenza vaccine and monosodium urate crystal adjuvant elicit protective immune response in pigs

Background

Influenza (flu) is a constant threat to humans and animals, and vaccination is one of the most effective ways to mitigate the disease. Due to incomplete protection induced by current flu vaccines, development of novel flu vaccine candidates is warranted to achieve greater efficacy against constantly evolving flu viruses.

Methods

In the present study, we used liposome nanoparticle (<200 nm diameter)-based subunit flu vaccine containing ten encapsulated highly conserved B and T cell epitope peptides to induce protective immune response against a zoonotic swine influenza A virus (SwIAV) H1N1 challenge infection in a pig model. Furthermore, we used monosodium urate (MSU) crystals as an adjuvant and co-administered the vaccine formulation as an intranasal mist to flu-free nursery pigs, twice at 3-week intervals.

Results

Liposome peptides flu vaccine delivered with MSU adjuvant improved the hemagglutination inhibition antibody titer and mucosal IgA response against the SwIAV challenge and also against two other highly genetically variant IAVs. Liposomal vaccines also enhanced the frequency of peptides and virus-specific T-helper/memory cells and IFN-γ response. The improved specific cellular and mucosal humoral immune responses in adjuvanted liposomal peptides flu vaccine partially protected pigs from flu-induced fever and pneumonic lesions, and reduced the nasal virus shedding and viral load in the lungs.

Conclusion

Overall, our study shows great promise for using liposome and MSU adjuvant- based subunit flu vaccine through the intranasal route, and provides scope for future, pre-clinical investigations in a pig model for developing potent human intranasal subunit flu vaccines.

Porous Nanoparticles With Self-Adjuvanting M2e-Fusion Protein and Recombinant Hemagglutinin Provide Strong and Broadly Protective Immunity Against Influenza Virus Infections

Due to the high risk of an outbreak of pandemic influenza, the development of a broadly protective universal influenza vaccine is highly warranted. The design of such a vaccine has attracted attention and much focus has been given to nanoparticle-based influenza vaccines which can be administered intranasally. This is particularly interesting since, contrary to injectable vaccines, mucosal vaccines elicit local IgA and lung resident T cell immunity, which have been found to correlate with stronger protection in experimental models of influenza virus infections. Also, studies in human volunteers have indicated that pre-existing CD4⁺ T cells correlate well to increased resistance against infection. We have previously developed a fusion protein with 3 copies of the ectodomain of matrix protein 2 (M2e), which is one of the most explored conserved influenza A virus antigens for a broadly protective vaccine known today. To improve the protective ability of the self-adjuvanting fusion protein, CTA1-3M2e-DD, we incorporated it into porous maltodextrin nanoparticles (NPLs). This proof-of-principle study demonstrates that the combined vaccine vector given intranasally enhanced immune protection against a live challenge infection and reduced the risk of virus transmission between immunized and unimmunized individuals. Most importantly, immune responses to NPLs that also contained recombinant hemagglutinin (HA) were strongly enhanced in a CTA1-enzyme dependent manner and we achieved broadly protective immunity against a lethal infection with heterosubtypic influenza virus. Immune protection was mediated by enhanced levels of lung resident CD4⁺ T cells as well as anti-HA and -M2e serum IgG and local IgA antibodies.

The Well-Developed Mucosal Immune Systems of Birds and Mammals Allow for Similar Approaches of Mucosal Vaccination in Both Types of Animals

The mucosal immune system is a compartmentalized part of the immune system that provides local immunity in the mucosa of the respiratory, gastrointestinal, and digestive tracts. It possesses secondary lymphoid tissues, which contain immune cells, such as T, B, and dendritic cells. Once the cells of the mucosal immune system are stimulated by luminal antigens, including microorganisms, they infiltrate into diffuse areas of mucosal tissues (e.g., respiratory mucosa and lamina propria of intestinal villi) and exhibit immune effector functions. Inducing the antigen-specific immune responses in mucosal tissues by mucosal vaccination would be an ideal strategy for not only humans, but also mammals and birds, to protect against infectious diseases occurring in mucosal tissues (e.g., pneumonia and diarrhea). Infectious diseases cause huge economic losses in agriculture, such as livestock and poultry industries. Since most infectious diseases occur in mucosal tissues, vaccines that are capable of inducing immune responses in mucosal tissues are in high need. In this review, we discuss the current understanding of mucosal immunity in mammals and birds, and recent progress in the development of mucosal vaccines.

Loss of integrity of doxorubicin liposomes during transcellular transportation evidenced by fluorescence resonance energy transfer effect

The aim of this work was to elucidate the influence of liposome characteristics on the transcellular process by in vitro studies that would enable designing more efficient oral formulations. Various liposomes with different properties were prepared, including 100-500 nm, anionic, cationic and PEGylated liposomes. All liposomes were labeled by fluorescence resonance energy transfer (FRET) probes to evaluate their integrity in cellular uptake and transport. The FRET fluorescent intensity is proportional to the amount of intact liposomes, which was used to calculate the amount of intact liposomes in cellular uptake and transport. The liposomal structures were found to lose their integrity during or after uptake and only about 20% intact liposomes were detected in cells. However, more cationic liposomes were transported integrally across cell monolayer and accounted for 40.49% of total transport by triple culture models of Caco-2/HT29-MTX/Raji B. These results suggest that liposomes could improve cellular uptake and transport of the payloads significantly, but only a small fraction of liposomes are transported integrally across epithelial monolayer. The study is therefore helpful to rationally fabricate more efficient oral liposomes for poorly water-soluble drugs or biomacromolecules.

Vaccine development for human mastadenovirus

Human mastadenovirus (HAdVs) can cause a broad spectrum of diseases in both children and adults, including acute respiratory infection, gastroenteritis, epidemic keratoconjunctivitis. Populations susceptible to adenovirus infection include children, immunocompromised patients and military recruits. To date, seven species (A-G) including more than 79 genotypes have been characterized, of which HAdV-B3, B4, B7 and the recently reemerged types 14 and 55 often lead to severe pneumonia. The live oral enteric-coated adenovirus type 4 and 7 vaccine, which was approved for use in US military personnel of 17 through 50 years of age, had been shown to be safe and highly effective in numerous clinical trials and by ongoing surveillance of febrile respiratory illness. However, there is currently no vaccine approved for general use in children and adults in any part of the world. This review article will summarize the epidemiological data available for adenovirus and the effectiveness of the adenovirus vaccine in the US military. It will also provide a brief overview of innovative vaccine strategies, animal models for vaccine evaluation, and issues regarding vaccine production.

The role of MPL and imiquimod adjuvants in enhancement of immune response and protection in BALB/c mice immunized with soluble Leishmania antigen (SLA) encapsulated in nanoliposome

Adjuvants play an essential role in the induction of immunity against leishmaniasis. In this study, monophosphoryl lipid A (MPL) and imiquimod (IMQ) were used as TLR ligands adjuvants to enhance immunogenicity and rate of protection against leishmaniasis. Nanoliposomes containing soluble Leishmania antigens (SLA) and adjuvants were consisted of DSPC, DSPG and Chol prepared by using lipid film method followed by bath sonication. The size of nanoliposomes was around 95 nm and their zeta potential was negative. BALB/c mice were immunized by liposomal formulations of lip/SLA, lip/MPL/SLA, lip/IMQ/SLA, lip/MPL/IMQ/SLA, lip/SLA + lip/IMQ, lip/SLA + lip/MPL, lip/SLA + lip/MPL/IMQ and five controls of SLA, lip/MPL, lip/IMQ, lip/MPL/IMQ and buffer by subcutaneously (SC) injections, three times in 2 weeks intervals. The synergic effect of two adjuvants when they are used in one formulation showed significantly (p < .001) smaller footpad swelling and the lowest parasite burden in lymph node and foot after the challenge. IgG2a in these groups showed the higher titre compared to control groups, which is compatible with the high IFN-γ production and lowest IL-4. Taken together the results indicated that co-delivery of MPL and IMQ adjuvants and antigen in nanoliposome carrier could be an appropriate delivery system to induce cellular immunity pathway against leishmaniasis.

Lipid-Based Particles: Versatile Delivery Systems for Mucosal Vaccination against Infection

Vaccination is the process of administering immunogenic formulations in order to induce or harness antigen (Ag)-specific antibody and T cell responses in order to protect against infections. Important successes have been obtained in protecting individuals against many deleterious pathological situations after parenteral vaccination. However, one of the major limitations of the current vaccination strategies is the administration route that may not be optimal for the induction of immunity at the site of pathogen entry, i.e., mucosal surfaces. It is now well documented that immune responses along the genital, respiratory, or gastrointestinal tracts have to be elicited locally to ensure efficient trafficking of effector and memory B and T cells to mucosal tissues. Moreover, needle-free mucosal delivery of vaccines is advantageous in terms of safety, compliance, and ease of administration. However, the quest for mucosal vaccines is challenging due to (1) the fact that Ag sampling has to be performed across the epithelium through a relatively limited number of portals of entry; (2) the deleterious acidic and proteolytic environment of the mucosae that affect the stability, integrity, and retention time of the applied Ags; and (3) the tolerogenic environment of mucosae, which requires the addition of adjuvants to elicit efficient effector immune responses. Until now, only few mucosally applicable vaccine formulations have been developed and successfully tested. In animal models and clinical trials, the use of lipidic structures such as liposomes, virosomes, immune stimulating complexes, gas-filled microbubbles and emulsions has proven efficient for the mucosal delivery of associated Ags and the induction of local and systemic immune reponses. Such particles are suitable for mucosal delivery because they protect the associated payload from degradation and deliver concentrated amounts of Ags via specialized sampling cells (microfold cells) within the mucosal epithelium to underlying antigen-presenting cells. The review aims at summarizing recent development in the field of mucosal vaccination using lipid-based particles. The modularity ensured by tailoring the lipidic design and content of particles, and their known safety as already established in humans, make the continuing appraisal of these vaccine candidates a promising development in the field of targeted mucosal vaccination.

The Multirole of Liposomes in Therapy and Prevention of Infectious Diseases

Liposomes are closed bilayer structures spontaneously formed by hydrated phospholipids that are widely used as efficient delivery systems for drugs or antigens, due to their capability to encapsulate bioactive hydrophilic, amphipathic, and lipophilic molecules into inner water phase or within lipid leaflets. The efficacy of liposomes as drug or antigen carriers has been improved in the last years to ameliorate pharmacokinetics and capacity to release their cargo in selected target organs or cells. Moreover, different formulations and variations in liposome composition have been often proposed to include immunostimulatory molecules, ligands for specific receptors, or stimuli responsive compounds. Intriguingly, independent research has unveiled the capacity of several phospholipids to play critical roles as intracellular messengers in modulating both innate and adaptive immune responses through various mechanisms, including (i) activation of different antimicrobial enzymatic pathways, (ii) driving the fusion–fission events between endosomes with direct consequences to phagosome maturation and/or to antigen presentation pathway, and (iii) modulation of the inflammatory response. These features can be exploited by including selected bioactive phospholipids in the bilayer scaffold of liposomes. This would represent an important step forward since drug or antigen carrying liposomes could be engineered to simultaneously activate different signal transduction pathways and target specific cells or tissues to induce antigen-specific T and/or B cell response. This lipid-based host-directed strategy can provide a focused antimicrobial innate and adaptive immune response against specific pathogens and offer a novel prophylactic or therapeutic option against chronic, recurrent, or drug-resistant infections.

A growing world of small things: a brief review on the nanostructured vaccines

Vaccines are the most cost-effective intervention in the management of infectious disease. Much of what we perceive as quality of life is related to a good health status and disease absence, for which vaccines are substantially responsible. Nonetheless, there are many infectious diseases for which no vaccine solution is available. That could be due to limitations of the classic approaches to vaccine development, including inactivated, subunit and attenuated vaccines. Nanostructured immunogens belong to a class of nonclassic vaccines in which nanostructures are loaded with antigen-related molecules. Here, we briefly review important features of the nanostructured vaccines – mainly those based in carbon nanotubes and gold nanorods – and discuss their use to prevent infectious diseases, especially those caused by viruses.

Modulating the immune system through nanotechnology

Nowadays, nanotechnology-based modulation of the immune system is presented as a cutting-edge strategy, which may lead to significant improvements in the treatment of severe diseases. In particular, efforts have been focused on the development of nanotechnology-based vaccines, which could be used for immunization or generation of tolerance. In this review, we highlight how different immune responses can be elicited by tuning nanosystems properties. In addition, we discuss specific formulation approaches designed for the development of anti-infectious and anti-autoimmune vaccines, as well as those intended to prevent the formation of antibodies against biologicals.

Dual-linker gold nanoparticles as adjuvanting carriers for multivalent display of recombinant influenza hemagglutinin trimers and flagellin improve the immunological responses in vivo and in vitro

Vaccination is the most cost-effective means of infectious disease control. Although current influenza vaccines are effective in battling closely matched strains, such vaccines have major limitations such as the requirement to produce new vaccines every season, an egg-dependent production system, long production periods, uncertainty in matching the vaccine to circulating strains, and the inability to react to new influenza pandemics resulting from genetic drift or shift. To overcome the intrinsic limitations of the conventional influenza vaccine, we have designed dual-linker gold nanoparticles (AuNPs) conjugated with both recombinant trimetric A/Aichi/2/68 (H3N2), hemagglutinin (HA) and TLR5 agonist flagellin (FliC) as a novel vaccine approach. Click chemistry and metal-chelating reactions were used to couple the two proteins. The conjugated proteins were found to possess high coupling specificity, high stability in harsh environments, high conjugation efficiency, and the ability to keep the appropriate protein conformations for immunogenicity and immunostimulation. Both AuNPs-HA/FliC and AuNPs-HA formulations induced higher levels of antibody responses than a mixture of soluble HA and FliC proteins when administered via a single intranasal immunization in mice. To further investigate the adjuvancy of these nanoparticles, in vitro experiments were conducted in both the JAWS II dendritic cell (DC) line and bone marrow-derived DC (BMDC) models. The results showed that dual-conjugated AuNPs were rapidly targeted and taken up by DCs. Consequently, DCs were induced toward maturation, as demonstrated by high levels of cytokine secretions and membrane costimulatory molecule expression. T cell proliferation was observed when splenic T cells were cocultured with AuNPs-HA/FliC-primed BMDCs. These results suggest that dual-conjugated AuNPs are effective at simultaneously displaying antigens and adjuvants in an oriented, multivalent format and can promote a strong immune response by activating DCs and T cells.

Nanoparticle-allergen complexes for allergen immunotherapy

Allergen-specific immunotherapy was introduced in clinical settings more than 100 years ago. It remains the only curative approach to treating allergic disorders that ameliorates symptoms, reduces medication costs, and blocks the onset of new sensitizations. Despite this clinical evidence and knowledge of some immunological mechanisms, there remain some open questions regarding the safety and efficacy of this treatment. This suggests the need for novel therapeutic approaches that attempt to reduce the dose and frequency of treatment administration, improving patient compliance, and reducing costs. In this context, the use of novel adjuvants has been proposed and, in recent years, biomedical applications using nanoparticles have been exploited in the attempt to find formulations with improved stability, bioavailability, favorable biodistribution profiles, and the capability of targeting specific cell populations. In this article, we review some of the most relevant regulatory aspects and challenges concerning nanoparticle-based formulations with immunomodulatory potential, their related immunosafety issues, and the nature of the nanoparticles most widely employed in the allergy field. Furthermore, we report in vitro and in vivo data published using allergen/nanoparticle systems, discuss their impact on the immune system in terms of immunomodulatory activity and the reduction of side effects, and show that this strategy is a novel and promising tool for the development of allergy vaccines.