Prof Sarah C Gilbert
| Research Area: | Immunology |
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| Technology Exchange: | Cellular immunology and Vaccine production and evaluation |
| Keywords: | vaccine, T cell, immunology, malaria, tuberculosis and influenza |
| Web Links: |
How the 'flu vaccine works - as shown on the BBC news website.
The Clinical Biomanufacturing Facility, University of Oxford
For more than ten years we have been making and testing vaccines designed to induce T cell responses to the antigens we encode, chiefly using antigens from malaria and tuberculosis. We have had most success with heterologous prime-boost regimes using either a DNA vaccine or recombinant fowlpox or adenovirus to prime a response and recombinant MVA to boost it. Several of the vaccines we have developed have progressed into clinical trials. We continue to work on finding the most efficient way to induce a protective T cell response by vaccination and are exploring a number of novel ways to do this.
Recombinant adenoviruses for clinical trials can now be produced to GMP by the University's Clinical Biomanufacturing Facility. Staff at the CNF work closely with academics to prepare batches of new vaccines for clinical trials.
In 2008 clinical trials of a new 'flu vaccine began in Oxford. Most adults already have memory T cell responses to 'flu antigens, but over time these fall below protective levels. The new vaccine, MVA-NP+M1 boosts these low level responses to very high levels. The next stage will be to test if these t cell responses can prvent people from being infected with 'flu.
| Name | Department | Institution | Country |
|---|---|---|---|
| Prof Adrian VS Hill | Jenner Institute | Oxford University | UK |
| Prof Alfredo Nicosia | Okairos | Italy | |
| Glyn Hewinson | VLA, Weybridge | UK |
2012. T-Cell Responses in Children to Internal Influenza Antigens, 1 Year after Immunization with Pandemic H1N1 Influenza Vaccine, and Response to Revaccination with Seasonal Trivalent Inactivated Influenza Vaccine. Pediatr Infect Dis J, Read abstract | Read more
BACKGROUND.: During seasonal influenza epidemics, 5-15% of the population are affected with an illness having a non-trivial mortality, morbidity and economic burden. Inactivated influenza vaccines are routinely used to prevent influenza infection, primarily by inducing humoral immunity. In addition, trivalent inactivated influenza vaccines have previously been shown to boost influenza-specific T-cell responses in a small percentage of adults. We investigate here the influenza-specific T-cell response, in children, one year after pandemic H1N1 vaccination and the ability to boost the T-cell response with trivalent inactivated influenza immunization. METHODS.: TPeripheral blood mononuclear cells (PBMCs) were isolated from children previously vaccinated with pandemic H1N1 vaccine, pre & post seasonal 2010-2011 TIV vaccination. Samples were analyzed by IFN-γ ELISpot for reactogencity toward internal influenza antigens (Nucleprotein (NP), Matrix protein 1 (M1), Nonstructural Protein 1 (NS1)). RESULTS.: Basal ex vivo T-cell responses to NP, M1 & NS1 measured by IFN-γ ELISpot assay were significantly higher in those children who had previously received an AS03B-adjuvanted split virion pandemic vaccine 12 months earlier rather than a non-adjuvanted whole virion vaccine. Boosting of these responses, 21 days after 2010/2011 seasonal TIV vaccination was observed regardless of age or prior pandemic vaccination regime, although boosting was greater in those groups with the lowest initial response. CONCLUSIONS.: We show here that children previously vaccinated with the 2009 pandemic H1N1 vaccine have measurable T-cell responses 1 year post vaccination. The magnitudes of these responses are dependent on both age of vaccinee and type of pandemic H1N1 vaccine used. Following 2010/2011 seasonal TIV vaccination these T-cell responses undergo a small but significant boost. Hide abstract
2012. Preliminary Assessment of the Efficacy of a T-Cell-Based Influenza Vaccine, MVA-NP+M1, in Humans. Clin Infect Dis, Read abstract | Read more
Background.The novel influenza vaccine MVA-NP+M1 is designed to boost cross-reactive T-cell responses to internal antigens of the influenza A virus that are conserved across all subtypes, providing protection against both influenza disease and virus shedding against all influenza A viruses. Following a phase 1 clinical study that demonstrated vaccine safety and immunogenicity, a phase 2a vaccination and influenza challenge study has been conducted in healthy adult volunteers.Methods.Volunteers with no measurable serum antibodies to influenza A/Wisconsin/67/2005 received either a single vaccination with MVA-NP+M1 or no vaccination. T-cell responses to the vaccine antigens were measured at enrollment and again prior to virus challenge. All volunteers underwent intranasal administration of influenza A/Wisconsin/67/2005 while in a quarantine unit and were monitored for symptoms of influenza disease and virus shedding.Results.Volunteers had a significantly increased T-cell response to the vaccine antigens following a single dose of the vaccine, with an increase in cytolytic effector molecules. Intranasal influenza challenge was undertaken without safety issues. Two of 11 vaccinees and 5 of 11 control subjects developed laboratory-confirmed influenza (symptoms plus virus shedding). Symptoms of influenza were less pronounced in the vaccinees and there was a significant reduction in the number of days of virus shedding in those vaccinees who developed influenza (mean, 1.09 days in controls, 0.45 days in vaccinees, P = .036).Conclusions.This study provides the first demonstration of clinical efficacy of a T-cell-based influenza vaccine and indicates that further clinical development should be undertaken.Clinical Trials Registration.NCT00993083. Hide abstract
2011. The requirement for potent adjuvants to enhance the immunogenicity and protective efficacy of protein vaccines can be overcome by prior immunization with a recombinant adenovirus. J Immunol, 187 (5), pp. 2602-2616. Read abstract | Read more
A central goal in vaccinology is the induction of high and sustained Ab responses. Protein-in-adjuvant formulations are commonly used to achieve such responses. However, their clinical development can be limited by the reactogenicity of some of the most potent preclinical adjuvants and the cost and complexity of licensing new adjuvants for human use. Also, few adjuvants induce strong cellular immunity, which is important for protection against many diseases, such as malaria. We compared classical adjuvants such as aluminum hydroxide to new preclinical adjuvants and adjuvants in clinical development, such as Abisco 100, CoVaccine HT, Montanide ISA720, and stable emulsion-glucopyranosyl lipid A, for their ability to induce high and sustained Ab responses and T cell responses. These adjuvants induced a broad range of Ab responses when used in a three-shot protein-in-adjuvant regimen using the model Ag OVA and leading blood-stage malaria vaccine candidate Ags. Surprisingly, this range of Ab immunogenicity was greatly reduced when a protein-in-adjuvant vaccine was used to boost Ab responses primed by a human adenovirus serotype 5 vaccine recombinant for the same Ag. This human adenovirus serotype 5-protein regimen also induced a more cytophilic Ab response and demonstrated improved efficacy of merozoite surface protein-1 protein vaccines against a Plasmodium yoelii blood-stage challenge. This indicates that the differential immunogenicity of protein vaccine adjuvants may be largely overcome by prior immunization with recombinant adenovirus, especially for adjuvants that are traditionally considered poorly immunogenic in the context of subunit vaccination and may circumvent the need for more potent chemical adjuvants. Hide abstract
2011. Potent CD8+ T-cell immunogenicity in humans of a novel heterosubtypic influenza A vaccine, MVA-NP+M1. Clin Infect Dis, 52 (1), pp. 1-7. Read abstract | Read more
Influenza A viruses cause occasional pandemics and frequent epidemics. Licensed influenza vaccines that induce high antibody titers to the highly polymorphic viral surface antigen hemagglutinin must be re-formulated and readministered annually. A vaccine providing protective immunity to the highly conserved internal antigens could provide longer-lasting protection against multiple influenza subtypes. Hide abstract
2010. Enhancing blood-stage malaria subunit vaccine immunogenicity in rhesus macaques by combining adenovirus, poxvirus, and protein-in-adjuvant vaccines. J Immunol, 185 (12), pp. 7583-7595. Read abstract | Read more
Protein-in-adjuvant formulations and viral-vectored vaccines encoding blood-stage malaria Ags have shown efficacy in rodent malaria models and in vitro assays against Plasmodium falciparum. Abs and CD4(+) T cell responses are associated with protective efficacy against blood-stage malaria, whereas CD8(+) T cells against some classical blood-stage Ags can also have a protective effect against liver-stage parasites. No subunit vaccine strategy alone has generated demonstrable high-level efficacy against blood-stage infection in clinical trials. The induction of high-level Ab responses, as well as potent T and B cell effector and memory populations, is likely to be essential to achieve immediate and sustained protective efficacy in humans. This study describes in detail the immunogenicity of vaccines against P. falciparum apical membrane Ag 1 in rhesus macaques (Macaca mulatta), including the chimpanzee adenovirus 63 (AdCh63), the poxvirus modified vaccinia virus Ankara (MVA), and protein vaccines formulated in Alhydrogel or CoVaccine HT adjuvants. AdCh63-MVA heterologous prime-boost immunization induces strong and long-lasting multifunctional CD8(+) and CD4(+) T cell responses that exhibit a central memory-like phenotype. Three-shot (AdCh63-MVA-protein) or two-shot (AdCh63-protein) regimens induce memory B cells and high-titer functional IgG responses that inhibit the growth of two divergent strains of P. falciparum in vitro. Prior immunization with adenoviral vectors of alternative human or simian serotype does not affect the immunogenicity of the AdCh63 apical membrane Ag 1 vaccine. These data encourage the further clinical development and coadministration of protein and viral vector vaccine platforms in an attempt to induce broad cellular and humoral immune responses against blood-stage malaria Ags in humans. Hide abstract
2010. Rapid generation of markerless recombinant MVA vaccines by en passant recombineering of a self-excising bacterial artificial chromosome. J Virol Methods, 168 (1-2), pp. 233-236. Read abstract | Read more
The non-replicating poxviral vector modified vaccinia virus Ankara (MVA) is currently a leading candidate for development of novel recombinant vaccines against globally important diseases. The 1980s technology for making recombinant MVA (and other poxviruses) is powerful and robust, but relies on rare recombination events in poxviral-infected cells. In the 21st century, it has become possible to apply bacterial artificial chromosome (BAC) technology to poxviruses, as first demonstrated by B. Moss' lab in 2002 for vaccinia virus. A similar BAC clone of MVA was subsequently derived, but while recombination-mediated genetic engineering for rapid production was used of deletion mutants, an alternative method was required for efficient insertion of transgenes. Furthermore "markerless" viruses, which carry no trace of the selectable marker used for their isolation, are increasingly required for clinical trials, and the viruses derived via the new method contained the BAC sequence in their genomic DNA. Two methods are adapted to MVA-BAC to provide more rapid generation of markerless recombinants in weeks rather than months. "En passant" recombineering is applied to the insertion of a transgene expression cassette and the removal of the selectable marker in bacteria; and a self-excising variant of MVA-BAC is constructed, in which the BAC cassette region is rapidly and efficiently lost from the viral genome following rescue of the BAC into infectious virus. These methods greatly facilitate and accelerate production of recombinant MVA, including markerless constructs. Hide abstract
2010. Long-term thermostabilization of live poxviral and adenoviral vaccine vectors at supraphysiological temperatures in carbohydrate glass. Sci Transl Med, 2 (19), pp. 19ra12. Read abstract | Read more
Live recombinant viral vectors based on adenoviruses and poxviruses are among the most promising platforms for development of new vaccines against diseases such as malaria, tuberculosis, and HIV-AIDS. Vaccines based on live viruses must remain infectious to be effective, so therefore need continuous refrigeration to maintain stability and viability, a requirement that can be costly and difficult, especially in developing countries. The sugars sucrose and trehalose are commonly used as stabilizing agents and cryoprotectants for biological products. Here, we have exploited the ability of these sugars to vitrify on desiccation to develop a thermostabilization technique for live viral vaccine vectors. By slowly drying vaccines suspended in solutions of these disaccharide stabilizers onto a filter-like support membrane at ambient temperature, an ultrathin glass is deposited on the fibers of the inert matrix. Immobilization of two recombinant vaccine vectors-E1/E3-deleted human adenovirus type 5 and modified vaccinia virus Ankara-in this glass on the membranes enabled complete recovery of viral titer and immunogenicity after storage at up to 45 degrees C for 6 months and even longer with minimal losses. Furthermore, the membrane carrying the stabilized vaccine can be incorporated into a holder attached to a syringe for almost simultaneous reconstitution and injection at point of use. The technology may potentially be developed for the deployment of viral vector-based biopharmaceuticals in resource-poor settings. Hide abstract
2010. Prime-boost vectored malaria vaccines: progress and prospects. Hum Vaccin, 6 (1), pp. 78-83. Read abstract
The difficulty of inducing protective immunity through antibodies against sporozoites led to efforts to assess vectored vaccines as a means of inducing protective T-cell immunity against the malaria liver-stage parasite. Although DNA vectored vaccines used alone were poorly immunogenic and not protective, high levels of parasite clearance in the liver has been achieved with viral vectored vaccines used in heterologous prime-boost regimes. Such vectored vaccination regimes represent one of only two approaches that have induced repeatable partial efficacy in human P. falciparum subunit vaccine trials. Interestingly, vectors expressing the TRAP antigen have been consistently been more immunogenic and protective than vectors expressing the circumsporozoite protein in human trials. However, sterile protection requires induction of very potent T-cell responses that are currently only achievable with heterologous prime-boost regimes. Recently, simian adenoviruses have been assessed as priming agents in Adenovirus-MVA regimes in both phase I and phase IIa trials in the UK, based on very promising pre-clinical results showing better immunogenicity and efficacy than previous prime-boost regimes. The same vectors are also being assessed clinically expressing blood-stage antigens, attempting to induce both protective antibodies and T cells as recently demonstrated in murine efficacy studies. These viral vectors now provide a major option for inclusion in a high efficacy multi-stage malaria vaccine that should achieve deployable levels of efficacy in endemic settings. Hide abstract
2009. Viral booster vaccines improve Mycobacterium bovis BCG-induced protection against bovine tuberculosis. Infect Immun, 77 (8), pp. 3364-3373. Read abstract | Read more
Previous work with small-animal laboratory models of tuberculosis has shown that vaccination strategies based on heterologous prime-boost protocols using Mycobacterium bovis bacillus Calmette-Guérin (BCG) to prime and modified vaccinia virus Ankara strain (MVA85A) or recombinant attenuated adenoviruses (Ad85A) expressing the mycobacterial antigen Ag85A to boost may increase the protective efficacy of BCG. Here we report the first efficacy data on using these vaccines in cattle, a natural target species of tuberculous infection. Protection was determined by measuring development of disease as an end point after M. bovis challenge. Either Ad85A or MVA85A boosting resulted in protection superior to that given by BCG alone: boosting BCG with MVA85A or Ad85A induced significant reduction in pathology in four/eight parameters assessed, while BCG vaccination alone did so in only one parameter studied. Protection was particularly evident in the lungs of vaccinated animals (median lung scores for naïve and BCG-, BCG/MVA85A-, and BCG/Ad85A-vaccinated animals were 10.5, 5, 2.5, and 0, respectively). The bacterial loads in lymph node tissues were also reduced after viral boosting of BCG-vaccinated calves compared to those in BCG-only-vaccinated animals. Analysis of vaccine-induced immunity identified memory responses measured by cultured enzyme-linked immunospot assay as well as in vitro interleukin-17 production as predictors of vaccination success, as both responses, measured before challenge, correlated positively with the degree of protection. Therefore, this study provides evidence of improved protection against tuberculosis by viral booster vaccination in a natural target species and has prioritized potential correlates of vaccine efficacy for further evaluation. These findings also have implications for human tuberculosis vaccine development. Hide abstract
2008. Recombination-mediated genetic engineering of a bacterial artificial chromosome clone of modified vaccinia virus Ankara (MVA). PLoS One, 3 (2), pp. e1638. Read abstract | Read more
The production, manipulation and rescue of a bacterial artificial chromosome clone of Vaccinia virus (VAC-BAC) in order to expedite construction of expression vectors and mutagenesis of the genome has been described (Domi & Moss, 2002, PNAS99 12415-20). The genomic BAC clone was 'rescued' back to infectious virus using a Fowlpox virus helper to supply transcriptional machinery. We apply here a similar approach to the attenuated strain Modified Vaccinia virus Ankara (MVA), now widely used as a safe non-replicating recombinant vaccine vector in mammals, including humans. Four apparently full-length, rescuable clones were obtained, which had indistinguishable immunogenicity in mice. One clone was shotgun sequenced and found to be identical to the parent. We employed GalK recombination-mediated genetic engineering (recombineering) of MVA-BAC to delete five selected viral genes. Deletion of C12L, A44L, A46R or B7R did not significantly affect CD8(+) T cell immunogenicity in BALB/c mice, but deletion of B15R enhanced specific CD8(+) T cell responses to one of two endogenous viral epitopes (from the E2 and F2 proteins), in accordance with published work (Staib et al., 2005, J. Gen. Virol.86, 1997-2006). In addition, we found a higher frequency of triple-positive IFN-gamma, TNF-alpha and IL-2 secreting E3-specific CD8+ T-cells 8 weeks after vaccination with MVA lacking B15R. Furthermore, a recombinant vaccine capable of inducing CD8(+) T cells against an epitope from Plasmodium berghei was created using GalK counterselection to insert an antigen expression cassette lacking a tandem marker gene into the traditional thymidine kinase locus of MVA-BAC. MVA continues to feature prominently in clinical trials of recombinant vaccines against diseases such as HIV-AIDS, malaria and tuberculosis. Here we demonstrate in proof-of-concept experiments that MVA-BAC recombineering is a viable route to more rapid and efficient generation of new candidate mutant and recombinant vaccines based on a clinically deployable viral vector. Hide abstract
2006. A DNA prime-modified vaccinia virus ankara boost vaccine encoding thrombospondin-related adhesion protein but not circumsporozoite protein partially protects healthy malaria-naive adults against Plasmodium falciparum sporozoite challenge. Infect Immun, 74 (10), pp. 5933-5942. Read abstract | Read more
The safety, immunogenicity, and efficacy of DNA and modified vaccinia virus Ankara (MVA) prime-boost regimes were assessed by using either thrombospondin-related adhesion protein (TRAP) with a multiple-epitope string ME (ME-TRAP) or the circumsporozoite protein (CS) of Plasmodium falciparum. Sixteen healthy subjects who never had malaria (malaria-naive subjects) received two priming vaccinations with DNA, followed by one boosting immunization with MVA, with either ME-TRAP or CS as the antigen. Immunogenicity was assessed by ex vivo gamma interferon (IFN-gamma) enzyme-linked immunospot assay (ELISPOT) and antibody assay. Two weeks after the final vaccination, the subjects underwent P. falciparum sporozoite challenge, with six unvaccinated controls. The vaccines were well tolerated and immunogenic, with the DDM-ME TRAP regimen producing stronger ex vivo IFN-gamma ELISPOT responses than DDM-CS. One of eight subjects receiving the DDM-ME TRAP regimen was completely protected against malaria challenge, with this group as a whole showing significant delay to parasitemia compared to controls (P = 0.045). The peak ex vivo IFN-gamma ELISPOT response in this group correlated strongly with the number of days to parasitemia (P = 0.033). No protection was observed in the DDM-CS group. Prime-boost vaccination with DNA and MVA encoding ME-TRAP but not CS resulted in partial protection against P. falciparum sporozoite challenge in the present study. Hide abstract
2006. Synergistic DNA-MVA prime-boost vaccination regimes for malaria and tuberculosis. Vaccine, 24 (21), pp. 4554-4561. Read abstract | Read more
T-cell-mediated responses against the liver-stage of Plasmodium falciparum are critical for protection in the human irradiated sporozoite model and several animal models. Heterologous prime-boost approaches, employing plasmid DNA and viral vector delivery of malarial DNA sequences, have proved particularly promising for maximising T-cell-mediated protection in animal models. The T-cell responses induced by this prime-boost regime, in animals and humans, are substantially greater than the sum of the responses induced by DNA or MVA vaccines used alone, leading to the term introduced here of "synergistic" prime-boost immunisation. The insert in our first generation clinical constructs is known as multiple epitope-thrombospondin-related adhesion protein (ME-TRAP). We have performed an extensive series of phase I/II trials evaluating various prime-boost combination regimens for delivery of ME-TRAP in over 500 malaria-naïve and malaria-exposed individuals. The three delivery vectors are DNA, modified vaccinia virus Ankara (MVA) and, more recently, fowlpox strain 9 (FP9). Administration was intra-epidermal and intramuscular for DNA and intradermal for MVA and FP9. Doses of DNA ranged from 4 microg to 2mg. Doses of MVA were up to 1.5 x 10(8) plaque forming units (pfu) and of FP9, up to 1.0 x 10(8)pfu. Further trials employing bacille Calmette-Guérin (BCG) as the priming agent and MVA expressing antigen 85A of Mycobacterium tuberculosis as the boosting agent has extended the scope of synergistic prime-boost vaccination. In this review we summarise the safety, immunogenicity and efficacy results from these malaria and tuberculosis vaccine clinical trials. Hide abstract
2005. Novel protein and poxvirus-based vaccine combinations for simultaneous induction of humoral and cell-mediated immunity. J Immunol, 175 (1), pp. 599-606. Read abstract
The presence of both cell-mediated and humoral immunity is important in protection from and clearance of a number of infectious pathogens. We describe novel vaccine regimens using combinations of plasmid DNA, poxvirus and protein to induce strong Ag-specific T cell and Ab responses simultaneously in a murine model. Intramuscular (i.m.) immunization with plasmid DNA encoding the middle Ag of hepatitis B (DNA) concurrently with a commercial hepatitis B virus (HBV) vaccine (Engerix-B) followed by boosting immunizations with both modified vaccinia virus Ankara (MVA) encoding the middle Ag of HBV and Engerix-B induced high levels of CD4(+) and CD8(+) T cells and high titer Ab responses to hepatitis B surface Ag (HbsAg). Substitution of Engerix-B with adjuvant-free rHBsAg induced similar T cell responses and greatly enhanced Ab levels. Repeated immunizations with recombinant or nonrecombinant MVA mixed with Ag induced higher titers of Abs compared with immunization with either Ag or Engerix-B further demonstrating this novel adjuvant effect of MVA. The poxviruses NYVAC, fowlpox (FP9) and ALVAC, and to a lesser extent, adenovirus, also displayed similar adjuvant properties when used in combination with rHBsAg. The use of poxviruses as an adjuvant for protein to concurrently induce Ag-specific T cells and Abs could be applied to the development of vaccines for many diseases, including HIV and malaria, where both cell mediated and humoral immunity may be important for protection. Hide abstract
Immunodominance of CD8+ T cell responses in poxviruses: application to multi-valent vaccines.
MVA (modified vaccinia virus Ankara) is an attenuated version of vaccinia virus, the smallpox vaccine, and has improved safety because it is unable to replicate in mammalian hosts. Together with its ability to stimulate CD8 + T cell responses to transgenic antigens from target pathogens, this improved safety profile makes MVA one of the most important tools for development of desperately needed new vaccines against globally important diseases such as malaria, TB, and HIV/AIDS. One of the ...
Influenza Vaccine Development
The 2009 influenza pandemic demonstrated the serious impact the ‘flu virus can have on human health. The unprecedented ease with which the swine origin H1N1 virus spread has caught many Healthcare systems ill-prepared. Although this new virus is not particularly virulent, the threat of a more deadly influenza pandemic is very real, and the possibility remains that a lack of natural immunity and time constraints for the development of classical flu vaccines will result in unprecedented ...
Mechanism of immunogenicity of vaccine vectors based on chimpanzee adenoviruses.
The Jenner Institute recently conducted a first-time-in-man clinical trial of a simian adenoviral vaccine vector, based on a virus isolated from chimpanzees. Replication-incompetent adenoviruses lacking the E1 and other genomic loci (adenovectors) not only have a continued leading role in gene therapy, but are also some of the most potent vectors for induction of cellular and humoral immune responses against transgenic antigens in humans and animals. They elicit long-lasting, multifunctional ...
