Human Vaccines & Immunotherapeutics
ISSN: 2164-5515 (Print) 2164-554X (Online) Journal homepage: http://www.tandfonline.com/loi/khvi20
Meeting Report VLPNPV: Sessions 1 and 2: Plenary Frank Sainsbury To cite this article: Frank Sainsbury (2014) Meeting Report VLPNPV: Sessions 1 and 2: Plenary, Human Vaccines & Immunotherapeutics, 10:10, 3060-3063, DOI: 10.4161/21645515.2014.988552 To link to this article: http://dx.doi.org/10.4161/21645515.2014.988552
Accepted author version posted online: 08 Dec 2014.
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Date: 12 November 2015, At: 12:24
MEETING REPORT Human Vaccines & Immunotherapeutics 10:10, 3060--3063; October 2014; © 2014 Taylor & Francis Group, LLC
Meeting Report VLPNPV: Sessions 1 and 2: Plenary Frank Sainsbury* The University of Queensland; Australian Institute for Bioengineering and Nanotechnology; St Lucia, QLD, Australia
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Keywords: cellular immunity, humoral immunity, immunotherapy, nano-particles, vaccine delivery, vaccine manufacture, vaccines, virus-like particles
Following the highly successful inaugural meeting in 2012, the second instalment of Virus-Like Particles and NanoParticle Vaccines (VLPNPV), proved to be a worthy follow-up in an outstanding conference series. VLPNPV is a forum for academics and industry to address one of the major areas of need in biomedical sciences, the development of novel prophylactic and therapeutic vaccines. The conference was opened by Professor Marianne Manchester of the University of California, San Diego who pointed to the significance of the site chosen for the conference, the Salk Institute. Founded by Jonas Salk, the Salk Institute for Biological Studies is a nonprofit, independent research institute with focuses in molecular biology and genetics, neurosciences, and plant biology. This diversity in research themes reflects the wishes of the institute’s founder who saw value in using interdisciplinary approaches to understanding the basic principles in life, aimed at generating new therapies and treatments for human disease. Likewise, interdisciplinarity was reflected in the main themes of the meeting, which also highlight some of the potential advantages of virus-like particle (VLP) and nanoparticle vaccines, including novel formulations/adjuvanting effects, structurally accurate/ designed antigens, production systems and capacity, and tailoring the immune response. These themes were covered by the 2 plenary sessions that opened the conference and are described in this report.
Plenary Session I The opening plenary session, chaired by Professor Richard Compans from Emory University, comprised 2 notable presentations that together demonstrated both the pressing need for alternatives to traditional vaccine technologies as well as the considerable advantages offered by VLP vaccines as potent stimulators of B-cell immune responses. The first presentation, entitled “The background and development of rotavirus and norovirus VLP vaccines for prevention of gastroenteritis in children,” was given by Professor Timo Vesikari from the Univeristy of Helsinki’s Vaccine Research Center. *Correspondence to: Frank Sainsbury; Email: [email protected] Submitted: 09/18/2014; Accepted: 09/28/2014 http://dx.doi.org/10.4161/21645515.2014.988552
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Acute gastroenteritis is a leading cause of morbidity and mortality in children globally and the 2 leading causative agents for viral gastroenteritis are Rotavirus (RV) and Norovirus (NoV). Since the introduction of RV vaccines, NoV has become the number one cause of acute gastroenteritis in children of the developed world and the development of a combined vaccine was very much the focus of the work presented. Live vaccines have shown that the gastroenteritis caused by RV infection is a preventable disease. However, while the 2 licensed vaccines, Rotarix and Rotateq, are highly efficacious in Europe and the US, they show significantly reduced efficacy in the developing world.1 While there have been concerns surrounding the manufacture of these vaccines as occurrences of Porcine circovirus DNA contamination has beset the production of them both, the main concern of live RV vaccines, as cited by Prof Vesikari, is the risk of intussusception. Although it is reported at low frequency, it is still not clear what role age plays in this risk and is, therefore, problematic. VLPs present the opportunity to develop vaccines against enteric viruses that do not contain the infectious genetic material and do not require live virus culturing. VP6 is the most abundant and most conserved structural protein of RV and when expressed alone it self-assembles into immunogenic rod-shaped particles. Although VP6 is not thought of as the classical antibody-inducing antigen of RV, it induces a high titer of antibodies upon live virus vaccination and is now a target for vaccine development. The icosahedral NoV VLP is readily producible via the self-assembly of the single capsid protein. It stimulates strong cellular and humoral immune responses, however, there are a number of distinct genogroups of NoV and vaccine candidates generally do not give a high degree of cross-protection. Prof. Vesikari’s work has shown an interesting cross-adjuvanting effect of the 2 particles, first demonstrated using RV VP6 VLPs in combination with NoV subgroup II VLPs.2 They have recently demonstrated that a trivalent combination vaccine that included VLPs from 2 NoV genogroups elicits a broader crossreactive immune response than either of the VLPs alone.3 In addition, using this approach they have reported the generation of non-serotype-specific mucosal antibodies able to inhibit RV infection in vitro and in vivo.4 The second presentation of the opening plenary was given by Professor Martin Bachmann, of the University of Zurich and the Jenner Institute at the University of Oxford. Prof Bachmann is well known for his pioneering work demonstrating the
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excellent ability of VLPs to stimulate strong B-cell immune responses and he gave a detailed overview of the molecular processes involved in his presentation, “Primary and secondary B cell responses induced by VLPs.” Prof Bachmann opened with the observation that for today’s vaccines, B-cell responses are more important than T-cell immune responses. The question is how do they achieve such a robust humoral response and what are the properties of VLPs that contribute to these processes? To initiate a durable antibody response, antigens need to reach follicular dendritic cells in the lymph nodes and VLPs are particularly adept at doing this. Generally below 200 nm in size, VLPs can drain directly to lymph nodes or be transported by peripheral dendritic cells. Here VLPs have an innate ability to escape degradation in the marginal zone and migrate to follicular dendritic cells. Prof Bachmann’s group has recently shown that both natural IgM antibodies and complement were required for this process, which is dependent on the size and multivalency of VLPs. In contrast, specifically induced IgG or IgM antibodies are required for the transport of a soluble protein with the same antigenic determinant.5 Fascinating work from Prof Bachmann and colleagues has shown that another mechanism is involved following intranasal vaccination. They have elucidated an important pathway from the lung to the spleen whereby VLPs are transported directly to follicular dendritic cells in the spleen by B cells.6 Operating via the B-cell receptor, the mechanism contrasts with transport of blood borne particles and, once more, this is likely enabled by the repetitive structure of VLPs. In more recent work the group continues to contribute to our understanding of how VLPs can elicit such a robust humoral immune response. Upon restimulation with a VLP antigen, memory B cells differentiate into secondary plasma cells, which then produce large amounts of antibodies independent of T-cell acitivation.7 This work also lends support to the theory that Bcell responses are dynamic, allowing adaptation to evolution of circulating strains.
Plenary Session II The three presentations of the second plenary session were chaired by Professor George Lomonossoff of the John Innes Center, UK and served to highlight the continuing need for further development of novel vaccine technologies in response to emerging infectious diseases, the ability of nanoparticle vaccines to present authentic antigens—allowing structure guided vaccine design, and the maturation of alternative production systems that take advantage of the fact that VLP and nanoparticle vaccines obviate the need for culturing live pathogens. The first of these, given by Professor Richard Compans, covered research on a highly topical subject, the development of an effective Ebolavirus (EBOV) vaccine. At the time of the presentation, the 2014 EBOV outbreak had already claimed 234 lives and it has since been declared an international public health emergency by the World Health Organization, stretching the ability of global authorities to prevent its further spread.
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Prof Compans’ talk “Designing Ebola VLP vaccines to avoid immune subversion” presented some of the challenges associated with the development of an effective vaccine against this formidable pathogen. One of the deadliest pathogens known to man in terms of mortality rates, the first outbreak was recorded in 1976. Since then, there have been intermittent outbreaks, mostly in subSaharan Africa and a number of attempts at making a vaccine have been made. As an enveloped virus, immunogenic filamentous VLPs can be efficiently produced by co-expression of the matrix protein and the surface glycoprotein (GP). EBOV VLPs have been shown to induce protective immunity in mice, guinea pigs and non-human primates, which is attributed to high titres of antibodies against GP.8 However, EBOV has evolved a unique mechanism to evade the immune response. A non-structural version of the glycoprotein (sGP) is expressed and secreted in high amounts by EBOVinfected cells. The protein is critical for maintaining infectivity in whole organisms, though not growth in cell culture, and research by Prof Compans and his colleagues has unravelled why. Their work shows that sGP can undermine the immune response to GP.9 The phenomenon that they term antigenic subversion describes the way sGP redirects the antibody response toward itself. Moreover, sGP competes for existing GP antibodies, implying that sGP produced during EBOV infection subsequent to vaccination could act as a decoy for GP, which mediates host cell attachment and fusion. This emphasizes the need for a vaccine that elicits sufficiently robust immunity to rapidly clear EBOV before antigenic subversion occurs. Prof Compans is also hoping VLP vaccines can be designed to overcome this tactic by removing the cross-reactive epitopes from GP that are shared with sGP. The second talk of the session, entitled “RSV fusion (F) nanoparticle immunogenicity in man: a new approach to vaccines?” was given by Dr Gale Smith (on behalf of Greg Glenn) of Novavax Inc. and covered the development of Respiratory syncytial virus (RSV) vaccines. This work demonstrated the flexibility of nanoparticle engineering and production, enabling the design of vaccines that elicit potent neutralising antibodies using protein structure principles. As described by Dr Smith, the challenge associated with designing an RSV vaccine is to do something that nature cannot. RSV is the most common cause of infant lower respiratory tract infections and is a major cause of infant mortality. The threat is greatest in the first few months of life and by the age of 2, almost all infants will have encountered RSV at least once. Recurrent RSV infection is common as natural immunity is largely ineffective. Therefore, although antibodies are actively transported from pregnant mothers to the developing fetus, protection against RSV is limited. The surface glycoprotein of RSV is highly variable between strains and the metastability of the fusion (F) protein means that it is also a moving target during infection. Thus, RSV immunisation remains a significant challenge and Dr Smith’s presentation outlined how this challenge is being met through the use of structure-guided vaccine design. The Novavax candidate nanoparticle vaccine consists of a stable oligomer of the postfusion
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confirmation of RSV F protein and the key to its development has been screening for the induction of Palivizumab-competing antibodies. The potent monoclonal antibody, Palivizumab (brand name Synagis), is prescribed to prevent severe RSV infection and recognizes a highly conserved antigenic site on F protein that is preserved and accessible in the postfusion state. Capitalising on work that showed that the stable postfusion RSV F protein is a potent elicitor of neutralising antibodies,10 the Novavax team produced 40 nm rosette-shaped protein nanoparticles from modified RSV F oligomers.11 Screening for Palivizumab-competing antibodies, they identified a candidate vaccine that induced protective immunity in rats. In a Phase I clinical trial it was shown to induce a titer of Palivizumab-competing antibodies many-fold higher than what is considered effective for Palivizumab.12 Therefore, through engineering a nanoparticle vaccine via the stable presentation of an epitope recognized by a potent clinically approved therapeutic antibody, Novavax has arrived at a very promising candidate vaccine for a historically difficult target. The immune response to this recombinant protein nanoparticle is robust in the elderly, another target population, and in women of child-bearing age. The latter is of considerable interest as future trials will be designed to demonstrate maternal immunisation. The final presentation of the plenary sessions was given by Dr Marc-Andre D’Aoust from Medicago Inc. who gave an overview of their capability and facilities for plant-based VLP vaccine production. Dr D’Aoust’s talk “Plant-produced influenza VLP vaccines and beyond” provided an impressive example of the role to be played by emerging production systems and technologies in bringing efficacious vaccines to populations faster and cheaper. Aquired in 2013 by Mitsubishi Tanabe Pharma, a top 50 pharmaceutical company, Medicago have developed a transient expression system using whole plant hosts, aimed at filling vaccine supply gaps. In the context of Influenza pandemics, for example, this refers to the current wait of approximately 6 months following strain indentification for vaccine to become available. During the 2009 swine flu pandemic Medicago demonstrated their ability to go from sequence identification to ready vials of VLP vaccine in just 3 weeks.13 The approach presents advantages in process development; as the plant leaf acts as the bioreactor, scaling from bench to industrial scale is seamless. In addition, capital costs are very low; a facility capable of producing References 1. Vesikari T. Rotavirus vaccination: a concise review. Clin Microbiol Infect 2012; 18 Suppl 5:57-63; PMID:22882248; http://dx.doi.org/10.1111/j.14690691.2012.03981.x 2. Blazevic V, Lappalainen S, Nurminen K, Huhti L, Vesikari T. Norovirus VLPs and rotavirus VP6 protein as combined vaccine for childhood gastroenteritis. Vaccine 2011; 29:8126-33; PMID:21854823; http://dx. doi.org/10.1016/j.vaccine.2011.08.026 3. Tamminen K, Lappalainen S, Huhti L, Vesikari T, Blazevic V. Trivalent combination vaccine induces broad heterologous immune responses to norovirus and rotavirus in mice. PloS One 2013; 8:e70409; PMID:23922988; http://dx.doi.org/10.1371/journal. pone.0070409
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10 M doses of pandemic influenza vaccine/month was built in just 14 months at less than one tenth of the cost of a comparable mammalian cell culture facility. Since demonstrating the safety and immunogenicity of an H5 hemagglutinin (HA) VLP vaccine in a 2009 phase I clinical trial,14 Medicago have gone on to demonstrate the exceptional effectiveness and safety of their plant-made influenza vaccines in a number of further trials. They have seen impressive crossprotection from their HA VLPs as well as evidence for a strong T-cell response in humans, which is particularly important for immunisation of the elderly. Accepted correlates of protection prescribed by regulatory bodies have been met by Medicago’s pandemic influenza vaccines and they are now turning their attention to a quadrivalent seasonal vaccine phase I/II trial. Medicago’s expression platform has been successfully used to produce a wide variety of VLPs. Over 30 influenza HA VLPs from A and B strains have been produced with none so far proving refractory to expression. Other enveloped VLPs such as for Rabies virus (RABV), Human immunodeficiency virus (HIV) and Severe acute respiratory syndrome coronavirus (SARS-CoV) have all been produced, as well as a number of non-enveloped VLPs such as Enterovirus 71 (EV71), Human paillomavirus (HPV) and RV. The latter is of particular interest as is consists of the entire complement of 4 RV structural proteins, underlining the capability of the plant-based expression system to produce even the most complex VLPs.
Summary VLPNPV 2014 brought together researchers interested in developing novel approaches to designing, manufacturing and delivering the next generations of vaccines. As was seen during the plenary sessions, VLP and nanoparticle vaccines have tremendous potential to further contribute to the future of preventative medicine. The conference highlighted the many ways in which such vaccines can overcome the limitations of traditional vaccines, from immune responses to manufacture, and the flexibility they afford in novel approaches to design and formulation. In addition, the mix of academic and industry-based attendees increases the appeal of this meeting, expanding the scope of the type of research covered from fundamental, through strategic and translational research, to commercial products.
4. Lappalainen S, Pastor AR, Tamminen K, LopezGuerrero V, Esquivel-Guadarrama F, Palomares LA, Vesikari T, Blazevic V. Immune responses elicited against rotavirus middle layer protein VP6 inhibit viral replication in vitro and in vivo. Hum Vaccines Immunother 2014; 10:2039-47; PMID:25424814; http://dx. doi.org/10.4161/hv.28858 5. Link A, Zabel F, Schnetzler Y, Titz A, Brombacher F, Bachmann MF. Innate immunity mediates follicular transport of particulate but not soluble protein antigen. J Immunol 2012; 188:3724-33; http://dx.doi.org/ 10.4049/jimmunol.1103312 6. Bessa J, Zabel F, Link A, Jegerlehner A, Hinton HJ, Schmitz N, Bauer M, Kundig TM, Saudan P, Bachmann MF. Low-affinity B cells transport viral particles from the lung to the spleen to initiate antibody
Human Vaccines & Immunotherapeutics
responses. Proc Natl Acad Sci U S A 2012; 109:2056671; PMID:23169669; http://dx.doi.org/10.1073/ pnas.1206970109 7. Zabel F, Mohanan D, Bessa J, Link A, Fettelschoss A, Saudan P, Kundig TM, Bachmann MF. Viral particles drive rapid differentiation of memory B cells into secondary plasma cells producing increased levels of antibodies. J Immunol 2014; 192:5499-508; http://dx.doi. org/10.4049/jimmunol.1400065 8. Falzarano D, Geisbert TW, Feldmann H. Progress in filovirus vaccine development: evaluating the potential for clinical use. Expert Rev Vaccines 2011; 10:63-77; PMID:21162622; http://dx.doi.org/10.1586/erv.10. 152 9. Mohan GS, Li W, Ye L, Compans RW, Yang C. Antigenic subversion: a novel mechanism of host immune
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Respiratory syncytial virus fusion glycoprotein expressed in insect cells form protein nanoparticles that induce protective immunity in cotton rats. PloS One 2012; 7:e50852; PMID:23226404; http://dx.doi.org/ 10.1371/journal.pone.0050852 12. Glenn GM, Smith G, Fries L, Raghunandan R, Lu H, Zhou B, Thomas DN, Hickman SP, Kpamegan E, Boddapati S, et al. Safety and immunogenicity of a Sf9 insect cell-derived respiratory syncytial virus fusion protein nanoparticle vaccine. Vaccine 2013; 31:524-32; PMID:23153449; http://dx.doi.org/10.1016/j.vaccine. 2012.11.009
13. D’Aoust MA, Couture MM, Charland N, Trepanier S, Landry N, Ors F, Vezina LP. The production of hemagglutinin-based virus-like particles in plants: a rapid, efficient and safe response to pandemic influenza. Plant Biotechnol J 2010; 8:607-19; PMID:20199612; http:// dx.doi.org/10.1111/j.1467-7652.2009.00496.x 14. Landry N, Ward BJ, Trepanier S, Montomoli E, Dargis M, Lapini G, Vezina LP. Preclinical and clinical development of plant-made virus-like particle vaccine against avian H5N1 influenza. PloS One 2010; 5: e15559; PMID:21203523; http://dx.doi.org/10.1371/ journal.pone.0015559
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evasion by Ebola virus. PLoS Pathog 2012; 8: e1003065; PMID:23271969; http://dx.doi.org/ 10.1371/journal.ppat.1003065 10. Swanson KA, Settembre EC, Shaw CA, Dey AK, Rappuoli R, Mandl CW, Dormitzer PR, Carfi A. Structural basis for immunization with postfusion respiratory syncytial virus fusion F glycoprotein (RSV F) to elicit high neutralizing antibody titers. Proc Nat Acad Sci U S A 2011; 108:9619-24; PMID:21586636; http://dx.doi. org/10.1073/pnas.1106536108 11. Smith G, Raghunandan R, Wu Y, Liu Y, Massare M, Nathan M, Zhou B, Lu H, Boddapati S, Li J, et al.
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ISSN: 2164-5515 (Print) 2164-554X (Online) Journal homepage: http://www.tandfonline.com/loi/khvi20
Meeting Report VLPNPV: Sessions 1 and 2: Plenary Frank Sainsbury To cite this article: Frank Sainsbury (2014) Meeting Report VLPNPV: Sessions 1 and 2: Plenary, Human Vaccines & Immunotherapeutics, 10:10, 3060-3063, DOI: 10.4161/21645515.2014.988552 To link to this article: http://dx.doi.org/10.4161/21645515.2014.988552
Accepted author version posted online: 08 Dec 2014.
Submit your article to this journal
Article views: 49
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=khvi20 Download by: [Penn State University]
Date: 12 November 2015, At: 12:24
MEETING REPORT Human Vaccines & Immunotherapeutics 10:10, 3060--3063; October 2014; © 2014 Taylor & Francis Group, LLC
Meeting Report VLPNPV: Sessions 1 and 2: Plenary Frank Sainsbury* The University of Queensland; Australian Institute for Bioengineering and Nanotechnology; St Lucia, QLD, Australia
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Keywords: cellular immunity, humoral immunity, immunotherapy, nano-particles, vaccine delivery, vaccine manufacture, vaccines, virus-like particles
Following the highly successful inaugural meeting in 2012, the second instalment of Virus-Like Particles and NanoParticle Vaccines (VLPNPV), proved to be a worthy follow-up in an outstanding conference series. VLPNPV is a forum for academics and industry to address one of the major areas of need in biomedical sciences, the development of novel prophylactic and therapeutic vaccines. The conference was opened by Professor Marianne Manchester of the University of California, San Diego who pointed to the significance of the site chosen for the conference, the Salk Institute. Founded by Jonas Salk, the Salk Institute for Biological Studies is a nonprofit, independent research institute with focuses in molecular biology and genetics, neurosciences, and plant biology. This diversity in research themes reflects the wishes of the institute’s founder who saw value in using interdisciplinary approaches to understanding the basic principles in life, aimed at generating new therapies and treatments for human disease. Likewise, interdisciplinarity was reflected in the main themes of the meeting, which also highlight some of the potential advantages of virus-like particle (VLP) and nanoparticle vaccines, including novel formulations/adjuvanting effects, structurally accurate/ designed antigens, production systems and capacity, and tailoring the immune response. These themes were covered by the 2 plenary sessions that opened the conference and are described in this report.
Plenary Session I The opening plenary session, chaired by Professor Richard Compans from Emory University, comprised 2 notable presentations that together demonstrated both the pressing need for alternatives to traditional vaccine technologies as well as the considerable advantages offered by VLP vaccines as potent stimulators of B-cell immune responses. The first presentation, entitled “The background and development of rotavirus and norovirus VLP vaccines for prevention of gastroenteritis in children,” was given by Professor Timo Vesikari from the Univeristy of Helsinki’s Vaccine Research Center. *Correspondence to: Frank Sainsbury; Email: [email protected] Submitted: 09/18/2014; Accepted: 09/28/2014 http://dx.doi.org/10.4161/21645515.2014.988552
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Acute gastroenteritis is a leading cause of morbidity and mortality in children globally and the 2 leading causative agents for viral gastroenteritis are Rotavirus (RV) and Norovirus (NoV). Since the introduction of RV vaccines, NoV has become the number one cause of acute gastroenteritis in children of the developed world and the development of a combined vaccine was very much the focus of the work presented. Live vaccines have shown that the gastroenteritis caused by RV infection is a preventable disease. However, while the 2 licensed vaccines, Rotarix and Rotateq, are highly efficacious in Europe and the US, they show significantly reduced efficacy in the developing world.1 While there have been concerns surrounding the manufacture of these vaccines as occurrences of Porcine circovirus DNA contamination has beset the production of them both, the main concern of live RV vaccines, as cited by Prof Vesikari, is the risk of intussusception. Although it is reported at low frequency, it is still not clear what role age plays in this risk and is, therefore, problematic. VLPs present the opportunity to develop vaccines against enteric viruses that do not contain the infectious genetic material and do not require live virus culturing. VP6 is the most abundant and most conserved structural protein of RV and when expressed alone it self-assembles into immunogenic rod-shaped particles. Although VP6 is not thought of as the classical antibody-inducing antigen of RV, it induces a high titer of antibodies upon live virus vaccination and is now a target for vaccine development. The icosahedral NoV VLP is readily producible via the self-assembly of the single capsid protein. It stimulates strong cellular and humoral immune responses, however, there are a number of distinct genogroups of NoV and vaccine candidates generally do not give a high degree of cross-protection. Prof. Vesikari’s work has shown an interesting cross-adjuvanting effect of the 2 particles, first demonstrated using RV VP6 VLPs in combination with NoV subgroup II VLPs.2 They have recently demonstrated that a trivalent combination vaccine that included VLPs from 2 NoV genogroups elicits a broader crossreactive immune response than either of the VLPs alone.3 In addition, using this approach they have reported the generation of non-serotype-specific mucosal antibodies able to inhibit RV infection in vitro and in vivo.4 The second presentation of the opening plenary was given by Professor Martin Bachmann, of the University of Zurich and the Jenner Institute at the University of Oxford. Prof Bachmann is well known for his pioneering work demonstrating the
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excellent ability of VLPs to stimulate strong B-cell immune responses and he gave a detailed overview of the molecular processes involved in his presentation, “Primary and secondary B cell responses induced by VLPs.” Prof Bachmann opened with the observation that for today’s vaccines, B-cell responses are more important than T-cell immune responses. The question is how do they achieve such a robust humoral response and what are the properties of VLPs that contribute to these processes? To initiate a durable antibody response, antigens need to reach follicular dendritic cells in the lymph nodes and VLPs are particularly adept at doing this. Generally below 200 nm in size, VLPs can drain directly to lymph nodes or be transported by peripheral dendritic cells. Here VLPs have an innate ability to escape degradation in the marginal zone and migrate to follicular dendritic cells. Prof Bachmann’s group has recently shown that both natural IgM antibodies and complement were required for this process, which is dependent on the size and multivalency of VLPs. In contrast, specifically induced IgG or IgM antibodies are required for the transport of a soluble protein with the same antigenic determinant.5 Fascinating work from Prof Bachmann and colleagues has shown that another mechanism is involved following intranasal vaccination. They have elucidated an important pathway from the lung to the spleen whereby VLPs are transported directly to follicular dendritic cells in the spleen by B cells.6 Operating via the B-cell receptor, the mechanism contrasts with transport of blood borne particles and, once more, this is likely enabled by the repetitive structure of VLPs. In more recent work the group continues to contribute to our understanding of how VLPs can elicit such a robust humoral immune response. Upon restimulation with a VLP antigen, memory B cells differentiate into secondary plasma cells, which then produce large amounts of antibodies independent of T-cell acitivation.7 This work also lends support to the theory that Bcell responses are dynamic, allowing adaptation to evolution of circulating strains.
Plenary Session II The three presentations of the second plenary session were chaired by Professor George Lomonossoff of the John Innes Center, UK and served to highlight the continuing need for further development of novel vaccine technologies in response to emerging infectious diseases, the ability of nanoparticle vaccines to present authentic antigens—allowing structure guided vaccine design, and the maturation of alternative production systems that take advantage of the fact that VLP and nanoparticle vaccines obviate the need for culturing live pathogens. The first of these, given by Professor Richard Compans, covered research on a highly topical subject, the development of an effective Ebolavirus (EBOV) vaccine. At the time of the presentation, the 2014 EBOV outbreak had already claimed 234 lives and it has since been declared an international public health emergency by the World Health Organization, stretching the ability of global authorities to prevent its further spread.
www.landesbioscience.com
Prof Compans’ talk “Designing Ebola VLP vaccines to avoid immune subversion” presented some of the challenges associated with the development of an effective vaccine against this formidable pathogen. One of the deadliest pathogens known to man in terms of mortality rates, the first outbreak was recorded in 1976. Since then, there have been intermittent outbreaks, mostly in subSaharan Africa and a number of attempts at making a vaccine have been made. As an enveloped virus, immunogenic filamentous VLPs can be efficiently produced by co-expression of the matrix protein and the surface glycoprotein (GP). EBOV VLPs have been shown to induce protective immunity in mice, guinea pigs and non-human primates, which is attributed to high titres of antibodies against GP.8 However, EBOV has evolved a unique mechanism to evade the immune response. A non-structural version of the glycoprotein (sGP) is expressed and secreted in high amounts by EBOVinfected cells. The protein is critical for maintaining infectivity in whole organisms, though not growth in cell culture, and research by Prof Compans and his colleagues has unravelled why. Their work shows that sGP can undermine the immune response to GP.9 The phenomenon that they term antigenic subversion describes the way sGP redirects the antibody response toward itself. Moreover, sGP competes for existing GP antibodies, implying that sGP produced during EBOV infection subsequent to vaccination could act as a decoy for GP, which mediates host cell attachment and fusion. This emphasizes the need for a vaccine that elicits sufficiently robust immunity to rapidly clear EBOV before antigenic subversion occurs. Prof Compans is also hoping VLP vaccines can be designed to overcome this tactic by removing the cross-reactive epitopes from GP that are shared with sGP. The second talk of the session, entitled “RSV fusion (F) nanoparticle immunogenicity in man: a new approach to vaccines?” was given by Dr Gale Smith (on behalf of Greg Glenn) of Novavax Inc. and covered the development of Respiratory syncytial virus (RSV) vaccines. This work demonstrated the flexibility of nanoparticle engineering and production, enabling the design of vaccines that elicit potent neutralising antibodies using protein structure principles. As described by Dr Smith, the challenge associated with designing an RSV vaccine is to do something that nature cannot. RSV is the most common cause of infant lower respiratory tract infections and is a major cause of infant mortality. The threat is greatest in the first few months of life and by the age of 2, almost all infants will have encountered RSV at least once. Recurrent RSV infection is common as natural immunity is largely ineffective. Therefore, although antibodies are actively transported from pregnant mothers to the developing fetus, protection against RSV is limited. The surface glycoprotein of RSV is highly variable between strains and the metastability of the fusion (F) protein means that it is also a moving target during infection. Thus, RSV immunisation remains a significant challenge and Dr Smith’s presentation outlined how this challenge is being met through the use of structure-guided vaccine design. The Novavax candidate nanoparticle vaccine consists of a stable oligomer of the postfusion
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confirmation of RSV F protein and the key to its development has been screening for the induction of Palivizumab-competing antibodies. The potent monoclonal antibody, Palivizumab (brand name Synagis), is prescribed to prevent severe RSV infection and recognizes a highly conserved antigenic site on F protein that is preserved and accessible in the postfusion state. Capitalising on work that showed that the stable postfusion RSV F protein is a potent elicitor of neutralising antibodies,10 the Novavax team produced 40 nm rosette-shaped protein nanoparticles from modified RSV F oligomers.11 Screening for Palivizumab-competing antibodies, they identified a candidate vaccine that induced protective immunity in rats. In a Phase I clinical trial it was shown to induce a titer of Palivizumab-competing antibodies many-fold higher than what is considered effective for Palivizumab.12 Therefore, through engineering a nanoparticle vaccine via the stable presentation of an epitope recognized by a potent clinically approved therapeutic antibody, Novavax has arrived at a very promising candidate vaccine for a historically difficult target. The immune response to this recombinant protein nanoparticle is robust in the elderly, another target population, and in women of child-bearing age. The latter is of considerable interest as future trials will be designed to demonstrate maternal immunisation. The final presentation of the plenary sessions was given by Dr Marc-Andre D’Aoust from Medicago Inc. who gave an overview of their capability and facilities for plant-based VLP vaccine production. Dr D’Aoust’s talk “Plant-produced influenza VLP vaccines and beyond” provided an impressive example of the role to be played by emerging production systems and technologies in bringing efficacious vaccines to populations faster and cheaper. Aquired in 2013 by Mitsubishi Tanabe Pharma, a top 50 pharmaceutical company, Medicago have developed a transient expression system using whole plant hosts, aimed at filling vaccine supply gaps. In the context of Influenza pandemics, for example, this refers to the current wait of approximately 6 months following strain indentification for vaccine to become available. During the 2009 swine flu pandemic Medicago demonstrated their ability to go from sequence identification to ready vials of VLP vaccine in just 3 weeks.13 The approach presents advantages in process development; as the plant leaf acts as the bioreactor, scaling from bench to industrial scale is seamless. In addition, capital costs are very low; a facility capable of producing References 1. Vesikari T. Rotavirus vaccination: a concise review. Clin Microbiol Infect 2012; 18 Suppl 5:57-63; PMID:22882248; http://dx.doi.org/10.1111/j.14690691.2012.03981.x 2. Blazevic V, Lappalainen S, Nurminen K, Huhti L, Vesikari T. Norovirus VLPs and rotavirus VP6 protein as combined vaccine for childhood gastroenteritis. Vaccine 2011; 29:8126-33; PMID:21854823; http://dx. doi.org/10.1016/j.vaccine.2011.08.026 3. Tamminen K, Lappalainen S, Huhti L, Vesikari T, Blazevic V. Trivalent combination vaccine induces broad heterologous immune responses to norovirus and rotavirus in mice. PloS One 2013; 8:e70409; PMID:23922988; http://dx.doi.org/10.1371/journal. pone.0070409
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10 M doses of pandemic influenza vaccine/month was built in just 14 months at less than one tenth of the cost of a comparable mammalian cell culture facility. Since demonstrating the safety and immunogenicity of an H5 hemagglutinin (HA) VLP vaccine in a 2009 phase I clinical trial,14 Medicago have gone on to demonstrate the exceptional effectiveness and safety of their plant-made influenza vaccines in a number of further trials. They have seen impressive crossprotection from their HA VLPs as well as evidence for a strong T-cell response in humans, which is particularly important for immunisation of the elderly. Accepted correlates of protection prescribed by regulatory bodies have been met by Medicago’s pandemic influenza vaccines and they are now turning their attention to a quadrivalent seasonal vaccine phase I/II trial. Medicago’s expression platform has been successfully used to produce a wide variety of VLPs. Over 30 influenza HA VLPs from A and B strains have been produced with none so far proving refractory to expression. Other enveloped VLPs such as for Rabies virus (RABV), Human immunodeficiency virus (HIV) and Severe acute respiratory syndrome coronavirus (SARS-CoV) have all been produced, as well as a number of non-enveloped VLPs such as Enterovirus 71 (EV71), Human paillomavirus (HPV) and RV. The latter is of particular interest as is consists of the entire complement of 4 RV structural proteins, underlining the capability of the plant-based expression system to produce even the most complex VLPs.
Summary VLPNPV 2014 brought together researchers interested in developing novel approaches to designing, manufacturing and delivering the next generations of vaccines. As was seen during the plenary sessions, VLP and nanoparticle vaccines have tremendous potential to further contribute to the future of preventative medicine. The conference highlighted the many ways in which such vaccines can overcome the limitations of traditional vaccines, from immune responses to manufacture, and the flexibility they afford in novel approaches to design and formulation. In addition, the mix of academic and industry-based attendees increases the appeal of this meeting, expanding the scope of the type of research covered from fundamental, through strategic and translational research, to commercial products.
4. Lappalainen S, Pastor AR, Tamminen K, LopezGuerrero V, Esquivel-Guadarrama F, Palomares LA, Vesikari T, Blazevic V. Immune responses elicited against rotavirus middle layer protein VP6 inhibit viral replication in vitro and in vivo. Hum Vaccines Immunother 2014; 10:2039-47; PMID:25424814; http://dx. doi.org/10.4161/hv.28858 5. Link A, Zabel F, Schnetzler Y, Titz A, Brombacher F, Bachmann MF. Innate immunity mediates follicular transport of particulate but not soluble protein antigen. J Immunol 2012; 188:3724-33; http://dx.doi.org/ 10.4049/jimmunol.1103312 6. Bessa J, Zabel F, Link A, Jegerlehner A, Hinton HJ, Schmitz N, Bauer M, Kundig TM, Saudan P, Bachmann MF. Low-affinity B cells transport viral particles from the lung to the spleen to initiate antibody
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responses. Proc Natl Acad Sci U S A 2012; 109:2056671; PMID:23169669; http://dx.doi.org/10.1073/ pnas.1206970109 7. Zabel F, Mohanan D, Bessa J, Link A, Fettelschoss A, Saudan P, Kundig TM, Bachmann MF. Viral particles drive rapid differentiation of memory B cells into secondary plasma cells producing increased levels of antibodies. J Immunol 2014; 192:5499-508; http://dx.doi. org/10.4049/jimmunol.1400065 8. Falzarano D, Geisbert TW, Feldmann H. Progress in filovirus vaccine development: evaluating the potential for clinical use. Expert Rev Vaccines 2011; 10:63-77; PMID:21162622; http://dx.doi.org/10.1586/erv.10. 152 9. Mohan GS, Li W, Ye L, Compans RW, Yang C. Antigenic subversion: a novel mechanism of host immune
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Respiratory syncytial virus fusion glycoprotein expressed in insect cells form protein nanoparticles that induce protective immunity in cotton rats. PloS One 2012; 7:e50852; PMID:23226404; http://dx.doi.org/ 10.1371/journal.pone.0050852 12. Glenn GM, Smith G, Fries L, Raghunandan R, Lu H, Zhou B, Thomas DN, Hickman SP, Kpamegan E, Boddapati S, et al. Safety and immunogenicity of a Sf9 insect cell-derived respiratory syncytial virus fusion protein nanoparticle vaccine. Vaccine 2013; 31:524-32; PMID:23153449; http://dx.doi.org/10.1016/j.vaccine. 2012.11.009
13. D’Aoust MA, Couture MM, Charland N, Trepanier S, Landry N, Ors F, Vezina LP. The production of hemagglutinin-based virus-like particles in plants: a rapid, efficient and safe response to pandemic influenza. Plant Biotechnol J 2010; 8:607-19; PMID:20199612; http:// dx.doi.org/10.1111/j.1467-7652.2009.00496.x 14. Landry N, Ward BJ, Trepanier S, Montomoli E, Dargis M, Lapini G, Vezina LP. Preclinical and clinical development of plant-made virus-like particle vaccine against avian H5N1 influenza. PloS One 2010; 5: e15559; PMID:21203523; http://dx.doi.org/10.1371/ journal.pone.0015559
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evasion by Ebola virus. PLoS Pathog 2012; 8: e1003065; PMID:23271969; http://dx.doi.org/ 10.1371/journal.ppat.1003065 10. Swanson KA, Settembre EC, Shaw CA, Dey AK, Rappuoli R, Mandl CW, Dormitzer PR, Carfi A. Structural basis for immunization with postfusion respiratory syncytial virus fusion F glycoprotein (RSV F) to elicit high neutralizing antibody titers. Proc Nat Acad Sci U S A 2011; 108:9619-24; PMID:21586636; http://dx.doi. org/10.1073/pnas.1106536108 11. Smith G, Raghunandan R, Wu Y, Liu Y, Massare M, Nathan M, Zhou B, Lu H, Boddapati S, Li J, et al.
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