Fourth International Conference: Modern Vaccines/Adjuvants Formulation—Impact On Future Development

Abstract

On the 15–17th of May 2013, about 120 scientists, postdoctoral fellows and professors representing renowned academic institutes and senior scientists and executives from small biotechs, contract research organizations (CROs) and Big Pharma companies, gathered at the Centre Hospitalier Universitaire Vaudois (CHUV) in Lausanne, Switzerland for the 4th international conference on Modern Vaccines and Adjuvants Formulation. Despite this relative small number, the speakers and attendees covered together a very broad field of expertise. Indeed, experts in microbiology, immunology, biochemistry, formulation, virus and nanoparticle characterization, vaccine production, quality control as well as regulatory professionals attended the conference and were able to present their works and discuss new developments within the field of vaccine and adjuvant development, characterization and approval process. This broad diversity was a highpoint of the conference and allowed for a stimulating environment and underlined the complexity of the challenges that the field currently faces in order to develop better or completely new vaccines and adjuvants.

Keywords: :

• adjuvant
• vaccine
• Nanoparticle (NP)
• Nanoemulsion (nanoE)
• Immunostimulatory complexe (ISCOM)

Introduction

Vaccines have already, in a very cost-efficient way, saved millions of lives around the world. From the eradication of smallpox, the almost complete elimination of poliomyelitis, the dramatic decrease in the incidence of diseases such as measles, mumps and rubella¹ to the more recent success in decreasing the prevalence of Human Papillomavirus (HPV) infections in vaccinated girls and women,² vaccines have demonstrated their great potential for treating life threatening diseases.

However the fight against infectious diseases and against some cancers is far from being won. Indeed, many infectious diseases are still killing millions of people every year (e.g., HIV, dengue virus, Respiratory Syncytial Virus (RSV), malaria)³ and despite tremendous amount of money and time spent on research and development, no commercial vaccines are on the market yet. Perhaps of even greater concern is that diseases that we thought were under control are re-emerging, as some of the early success stories show some worrying sign of loss or absence of protection (e.g., the Bacille Calmette-Guérin (BCG) vaccine against Mycobacteria tuberculosis (Mtb)⁴). There is therefore still, or maybe even more than ever, a great need for new or improved vaccines targeting new pathological pathways, exploiting new immunological discoveries or taking the full advantages of new adjuvants using recent developments within material science, formulation and nanotechnology. During the 4th international conference of modern vaccines/adjuvants formulation several of such new developments were presented, ranging from presentation of new therapeutic targets/strategies (e.g., against HIV, RSV, nicotine), new adjuvants/formulations (nanoparticles, virosomes/liposomes, nanoemulsions, ISCOMs), to new techniques and services for their characterization (automated electron microscopy images analysis, nanopore-based detection and in vivo and in vitro model) as well as the highly important regulatory and safety issues questions.

More particularly, within the session 3 entitled « nanoparticles vaccine adjuvants I » moderated by Dr. Guro Gafvelin from the biotech company Viscogel AB, Solna, Sweden, three different examples of adjuvants (and examples on their applications) were presented. These examples highlighted quite well some of the approaches that could be used to improve existing or new vaccine therapies.

Polymeric Nanoparticles

Professor Jeffrey A. Hubbell, from the “Ecole Polytechnique Fédérale de Lausanne,” Lausanne, Switzerland presented the work of his group on the development and characterization of novel polymeric nanoparticles. More precisely, they have developed fully synthetic nanoparticles that combine the potential safety, cost and manufacturing advantages of synthetic compounds with efficient and precise drug/gene delivery to specific immune cells and cell compartments in order to induce specific immuno-modulatory responses.

In the present case, Prof. Hubbell presented data on their effort to induce a potent CD8⁺ Cytotoxic T Lymphocytes (CTL) response which, while being critical for protection against several infectious pathogens and tumor cells, is difficult to induce with “classical” sub-unit vaccines that usually follow the extra-cellular/MHC-II antigens presentation’s pathway. In this regard they have engineered oxidation-sensitive polymer nanoparticles (NPs) (hydrophobic-core materials bearing antigen on their surface) and polymersomes (vesicular materials bearing antigen in their watery-core) -based carriers. They showed that due to their very small size (30–40nm), these nanoparticles were able to exploit the interstitial spaces and migrate to the draining lymph nodes (dLNs) when injected intradermally or to the lung when administered by intranasal instillation and to efficiently target dendritic cells (DCs), especially after conjugation of the antigen of interest to the NPs with a reducible bond (disulfide). They were also able to show that, while vaccination with antigens conjugated to the nanoparticles (Ag-NPs) alone didn’t induce any immune response, vaccination with Ag-NPs + CpG, induced an increased, compared with Ag + CpG alone, antigens uptake by DCs and transport to the dLNs resulting in a local and systemic CD4⁺ (Th1) and CD8⁺ T-cell immune response through cross-presentation.^5-7 Very interestingly, this increased T cell response was associated with increased protection in a transgenic OVA-influenza model (after vaccination with OVA-NPs conjugates + CpG) and a Tuberculosis (TB) mouse model (vaccination with Ag85B-NPs conjugates + CpG).^7,8

This work demonstrated how well- and finely-designed nanoparticles could allow for fine-tuned and specific immune-activations. One could envision slightly different nanoparticles/nanoparticles-coupled Ag for targeting different immunological pathways for different vaccines; of course such immune-protection correlates would have to be discovered first since they are still often missing for many diseases. Nevertheless, it will be very interesting to see future human clinical trials testing these nanoparticles and new applications for these nanoparticles

Nanoemulsions

Nanoemulsions (nanoE) are oil-in-water (o/w) or water-in-oil (w/o) emulsions with droplet diameters ranging from 50 to 1000 nm. Their small size, stability at room temperature, relatively low cost and efficacy for transdermal and intra-nasal delivery has already made NanoE very attractive within several fields such as cosmetics and drug delivery.⁹

Another very interesting property of the NanoEs, especially for vaccine and adjuvant development, is their ability to kill pathogens by physical disruption of the cell wall and subsequent lysis of the organism. This characteristic has already been exploited and tested, in particular by the biotech company NanoBio Corporation, Ann Arbor, Michigan, USA. For instance, they have already demonstrated in several infection models that NanoE-formulated vaccines induced good humoral responses with neutralizing serum antibodies against anthrax, whole vaccinia virus, influenza virus, HIV-gp120 and hepatitis B surface antigen.^10-14 During the conference, Dr. Ali Fattom presented a new Respiratory Syncytial Virus (RSV) vaccine developed using Nanobio’s nanoemulsion-based vaccine platform (NanoE-RSV). Dr. Fattom started by demonstrating, in a standard in vitro plaque assay, that formulation of live RSV with their nanoemulsion (NanoBio Corporation’s nanoE consisting on O/W emulsions with average droplet size < 400 nm) resulted in a rapid and complete eradication of the live virus particles and “encapsulation” of the splited viruses. This is an exciting property since it has the potential to provide the same benefit of the early/empirical (and mostly successful) killed or live-attenuated vaccines, i.e., providing the immune system with most, if not all, of the epitopes and therefore ensure and optimal and broad polyclonal response. While it could potentially also lead to additional regulatory questions for, for example batch to batch characterization, it also allows for a potential faster vaccine preparation by combining the virus inactivation with the formulation, removing several steps in the vaccine production process.

Experiments aiming at exploring the mode of action of NanoBio’s NanoE platform in general and their NanoE-RSV vaccine showed that after both intra-nasal (IN) or intramuscular (IM) vaccinations, NanoE-RSV induce a Th1/Th17-biased (at least partially in a TLR2 and 4 dependent pathway) local and systemic response as well as antibody productions. Interestingly, these responses were correlated with an increased virus clearance and decrease in pathology in a mouse and cotton rat models of RSV infections.^15,16 Additionally, when compared with formaldehyde-inactived RSV and alum formulated (FI-RSV-Alum) in an IM immunization model, while the total IgG titer were similar between NanoE-RSV and FI-RSV-Alum, NanoE-RSV induced higher neutralizing activity and the vaccinated animal cleared the infection .

This technology shows great potential and it will be interesting to see future applications as well as safety and immunological data in human clinical trials.

Immunostimulatory Complexe (ISCOM)

Adjuvants can often be divided into three main groups depending on their mechanisms of action. They can serve as delivery systems for the actual active substance (API, genetic material) like the NPs/polymersome of the Hubbell’s group, they can augment/modulate the immune response toward antigens of interest or be able to do both. Immunostimulatory complexes or ISCOMs are particulate antigen delivery systems composed of antigen, cholesterol, phospholipid and saponin which has been shown to be part of the third category by combining delivery system with immunomodulatory capacities. This property has already been exploited and tested for immunogenicity and protection in animal models and human with antigens from a great variety of pathogens,¹⁷ despite lack of a complete understanding of their mode of action (MoA).

Dr. Sofia Magnusson from the biotech company Isconova AB, Uppsala, Sweden, presented some of their most recent pre-clinical data on their ISCOM, Matrix MTM as well as some updates on their different clinical trials. Isconova’s ISCOM, Matrix M™, is composed of two separately made nanoparticles formulated from of two different purified fractions of Quillaja saponin, yielding Matrix-A™ and Matrix-C™, which are subsequently mixed at defined ratios (85–92% Matrix-A™ and 8–15% Matrix-C™) to obtain Matrix M™ of a size of 40nm. This reduced use of fraction C having the benefit to decrease the known toxicity of saponin while retaining their adjuvant property.

In their latest pre-clinical data, Dr. Magnusson showed that Matrix M™ displayed immunomodulation properties even without being combined with antigens. More specifically, sub cutaneous (s.c.) injection of high dose of Matrix M™ induced immune cell recruitment, mostly granulocytes, to the draining lymph nodes and spleens and activation the immune system as measured by CD69 upregulation on several type of leukocytes.¹⁸ It therefore appears, as Isconova suggests, that Matrix M™ induces some sort of pre-activated state for the encounter with the antigens, maybe by providing the signals 3 « danger signals » and 4 (homing/targeting to lymphoid organs) necessary for an optimal immune response. When combined with influenza Ags (from the commercially available split vaccine Vaxigrip®, Sanofi Pasteur), Matrix M™ induced a balanced Th1/Th2 (IFNγ, IL-2, -4, -5, and -10) cellular as well as a good humoral (IgG1 and IgG2a) responses, at least as good or sometime stronger than the other adjuvants tested in their model (Alum and AS03).¹⁹

Very interestingly, Matrix-M™ has already been included and evaluated in several phase I clinical trials; study on vaccination against pandemic influenza in adult (PanFluVac virosomal HA adjuvanted in Matrix-M™)²⁰ and study on vaccination against seasonal influenza in elderly (Vaxigrip® adjuvanted in Matrix-M™).²¹ Both studies show good safety profile for Matrix-M™ (only mild and transient Adverse Events [AE] were reported), good immunogenicity and dose-sparing effects.²² These data are very promising and seems to confirm the potential of Matrix-M™ and it will be very interesting to see future efficacy data in phase II studies. Isconova is now planning to start a 3rd phase I clinical trials evaluating the potential dose-sparing effect and decrease in number of vaccinations induced by a Rabies vaccines- Matrix-M™.

Summary

Now that the “low hanging fruits” vaccines using empirical approaches have been done,¹ in order to develop new vaccines there are increasing evidences for the need for very tight and broad collaborations between different fields of research but also with quality and regulatory experts and agencies.

Indeed, one of the major problems faced when developing new vaccines is that in many cases, we still don’t have very good correlate between specific immune response(s) and protection. Therefore, we need to increase our knowledge of the pathogenesis of our pathogen/disease of interest as well as our understanding on why our immune system failed to protect us form it. The next step is the need to discover new drugs/epitopes to activate, amplify or “repair” this specific defective protective immune response and then a way to deliver this cargo (API, genes, etc) to the right place at the right time. Finally, good, precise and accepted quality controls and regulatory guidelines as well as manufacturing capacities are needed to actually be able to test these new vaccines/adjuvants in clinical trials and bring them to the markets.

This may be achieved only by the combined efforts of specialists from many different fields; microbiologists and immunologists to discover new pathological targets and exploit new immunoprotective pathways; biochemists, formulation and nanotechnology experts to develop new delivery/immunomodulators (adjuvants); regulatory and quality control experts to define precise guidelines for the characterization of such new therapies and technologies/CROs allowing for such characterization. The 4th international conference of modern vaccines/adjuvants formulation did regroup such a variety of scientists and experts and it is why, I believe this conference was a success.

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.