Patent Application
20060188991
The invention relates to a novel vaccine platform that includes a reassembled virus constructed from one or more subunits, each subunit containing a different peptide or nucleic acid moiety added by genetic fusion or in vitro conjugation such that each subunit incorporates a target therapeutic agent. The invention further relates to a method for assembling RNA molecules in vitro for delivery and expression in eukaryotic cells. In particular, the invention provides for proteins, molecules and nucleic acid sequences necessary for the packaging of RNA molecules for delivery and expression in a eukaryotic cell. The packaged RNA molecules of the invention are capable of delivery to a wide range of eukaryotic cells. The packaged RNA molecules may also be targeted to specific eukaryotic cells. The invention further includes a delivery platform where the above described reassembled viruses or virus-like particles (VLPs), RNA vaccines are used to induce either cellular or humoral immunity, or both simultaneously, by the synergistic action of peptide fusions to the virus or VLP structure and the encoded proteins of the RNA.
To date, most traditional vaccines have been composed of live-attenuated or inactivated whole pathogen preparations. Generation of these sorts of vaccines is limited by the requirement for long and intensive basic research and development. Reliable production and scale-up technologies for live-attenuated or inactivated vaccines would be almost impossible to develop at short notice. There is, therefore, a need for the development of a safe, robust and broadly-useful technology that is suitable for the production of vaccines against unanticipated infectious disease threats. Vaccines developed from plant-virus-pathogen chimera's may provide a method to rapidly produce vaccines that can be used to prevent or treat a number of known or emerging disease threats.
Controlling immune responses to pathogens and tumor cells has been the focus of immunology, cell biology and pharmaceutical development for several decades. Much has been learned about the complexity of immune cells and the patterns and effect of cytokine expression in response to pathogen challenge, and vaccine administration. One key aspect of this work has been the identification of two major arms of the immune response, the Th1 response, which is largely cellular, and the Th2 response, which is predominantly humoral. The two types of immune responses are mounted in response to how foreign antigens are presented to the immune system, what cytokines are expressed by presenting cells and what types of immune cells are activated. Th1 responses result in cytotoxic immune cell function and production of neutralizing antibodies of a different subtype than observed with Th2 responses. While some pathogens can be susceptible to Th2 responses, the Th1 response is key to mounting an effective response to both pathogen and tumor cells. However, both pathogens and tumor cells have developed strategies to avoid immune surveillance, bypassing mechanisms that are essential to Th1 immunity.
A key goal in vaccine development is to direct Th1 type immunity, in addition to Th2 humoral responses, upon vaccine administration to the host. By using an attenuated cowpox virus, Jenner unknowingly took advantage of the powerful activation of Th1 pathway to prevent smallpox infections. Since his time, most pathogen vaccines have been killed or attenuated, which have generally shown good success in controlling pathogen morbidity and viral spread. However, two aspects of recent vaccine development have led to growing concerns for live or attenuated viral vaccines. The use of an attenuated or killed virus to treat human immunodeficiency virus (HIV) is impractical for several reasons. Occupational safety concerns, low yield of attenuated virus, and the threat of viral mutation or escape are serious drawback to both vaccine development and public acceptance. In other cases, as observed with measles virus and respiratory syncytial virus (RSV), unpredictable and severe adverse events are associated with whole virus immunization. Therefore, much research has focused on “subunit” vaccines, which are composed of pathogen protein(s) or peptides that are generally targeted by the host immune response for protective immunity (Vaccines, 3rd ed 1999, Plotkin and Orenstein, Philadelphia Pa., Saunders Co). Unfortunately, protein subunit vaccines don't often elicit strong Th1 responses by themselves, and DNA subunit vaccines often fail to elicit antibodies. In most cases both antibodies and CTL responses are necessary in controlling pathogenesis or disease progression.
Two new types of vaccines have been created to overcome the deficiencies of current subunit vaccines. Non-pathogenic viruses have been genetically modified to encode immunogenic subunit proteins of a pathogen, thus taking advantage of the Th1 immune response to viral antigen presentation. Strong Th1 type immune responses have been demonstrated for many pathogen and self-antigens using adenovirus, vaccinia, fowlpox and alphavirus delivery systems (Walther and Stein. 2000 Drugs 60, 249). However, these “first generation” viral delivery systems encountered problems due to the vector immunogenicity, which precluded their subsequent use in booster immunizations. Viral priming followed by either protein or DNA boosting has been successful, but this approach requires the manufacture of at least two agents for a single vaccine. The large-scale manufacture of DNA and/or protein for these vaccines has encountered both technical and financial challenges.
A second strategy takes advantage of the self-assembly of viral coat proteins into virus like particles (VLPs), which by themselves stimulate strong Th1 antigen responses (Schiller and Lowy. 2001 Expert Opin Biol Ther. 1, 571). VLPs constructed from arrayed viral coat have been shown to be effective in stimulating both neutralizing antibody and cytotoxic T lymphocyte (CTL) responses. Viral coat proteins are also effective carriers of antigens through fusion to the external solvent-exposed residues, usually by genetic fusion (Pogue et al. 2002 Ann Rev Phyto Path 40, 3; Da Silva.1999 Curr Opin Mol Ther 1, 82). Though promising, VLP technology also has drawbacks. Production is again limiting, and often fusion of a heterologous antigen to the coat reduces VLP yield, solubility, or prevents self-assembly. In addition, immune clearance, the same mechanism that limits whole virus boosting, also limits the use of VLPs. Clearly, there is a need for a cost effective viral coat antigen delivery system that overcomes the limitations of both whole virus and VLP technology for vaccine delivery. The properties of this system would include all the benefits of boosting Th1 responses via a virus-like antigen presentation to the immune system without pathogenicity, flexibility to rotate the VLP backbone to which the antigen is fused, generation of and control of immunogenicity, high yield and low cost.
Applicant and others have shown that coat proteins from plant viruses have all the immunologic presentation properties of mammalian virus coat, but without pathogenicity. A large number of positive (+) strand RNA plant viruses, including Tobacco Mosaic Virus (TMV), type member of the tobamovirus family, have been cloned and manipulated in vitro to express heterologous gene products in plants as well as to display biologically relevant peptides on its virion surface. A unique property of TMV virions is their ability to be disassociated to form monomers and self assemble into VLPs using a RNA scaffold. Plant coat proteins, including TMV, engineered to display foreign epitopes have been shown to promote functional immunity to both self-antigens (Savelyeva N 2001 Nat Biotechnol 19 760) and various pathogens (Pogue et al. 2002 Ann Rev Phyto Path 40, 3).
Essential for the encapsidation of the viral genomic RNA molecule into an infectious particle is the presence of a sequence element referred to as the origin of assembly (OAS). The TMV OAS is located approximately 1 Kb from the 3′ end of the viral genome and consists of a 440 nucleotide sequence that is predicted to form three hairpin stem-loop structures (Turner and Butler, 1986). The viral coat protein disks initially bind to loop 1 during viral assembly. In vitro packaging assays using mutual assembly origin transcripts have defined the 75 nucleotides comprising loop 1 as necessary and sufficient for encapsidation of foreign or viral RNA sequences (Turner et al., 1988). In vitro reconstitution studies have shown that preparations of purified coat protein, derived from virions from infected plant cells, are able to assemble into helical structures with TMV RNA at pH 7.0, resulting in assembly of TMV-like viral particles containing RNA (Fraenkel-Conrat and Williams, 1955). Furthermore, it has been shown that foreign chimeric RNA molecules containing OAS sequences, transcribed in vitro using SP6 or T7 RNA polymerase, may be assembled in vitro into pseudovirus particles (Sleat et al., 1986).
The cloning and sequencing of the viral coat proteins responsible for encapsidation has led to the insertion of these genes into bacterial expression vectors in, for example, E. coli (Shire et al., 1990). However, in vitro assembly with recombinant E. coli viral coat proteins results in a decreased reconstitution rate relative to native coat protein produced in plants (Shire et al., 1990). U.S. Pat. No. 5,443,969 attempts to overcome this deficiency in E. coli by packaging RNA sequences containing a TMV-OAS in vivo in E. coli, instead of in vitro. However, introduction of the encapsidated viral vectors into hosts outside of plants is problematic. The lack of acetylation of the TMV coat protein in E. coli results in poorly efficient encapsidation of non-capped RNAs. These RNAs are poorly translated in eukaryotic cells due to the lack of the cap structure. Further, the yields of recombinant TMV products in E. coli are very poor and not commercially feasible.
The process of intracellular delivery of genetic material for therapeutic purposes by either correcting an existing abnormality or providing cells with a new function is the basis behind gene therapy (Drew and Martin, 1999), and for DNA immunizations. Practically speaking, nucleic acid immunization technologies present an attractive front-line defense against new pathogens: there is probably no other system that can compete as the first line in a rapid-response subunit vaccine strategy. However, conventional DNA vaccines suffer from a number of significant drawbacks that makes reliance on this technology alone unwise. Most significantly, the dose of DNA required to stimulate an effective immune responses is very high, with the implication that production of significant quantities for large scale immunization will be challenging. DNA and RNA vaccines are generally capable of promoting good Th1 type cytotoxic T cell responses, which are essential for elimination of non-cytopathic pathogens. However, with few exceptions, the antibody response induced by DNA vaccines is poor. Hence, although nucleic acid vaccines are attractive from the prospective that production can be very rapid, ideally an initial DNA or RNA vaccination should be followed by a booster vaccination, preferably with protein, to induce efficient antibody production and more complete protection against pathogen challenge. The current invention addresses the issues raised above by introducing a novel and flexible vaccine delivery platform
The present invention includes several unique solutions that address current limitations of VLP technology, while retaining all the positive characteristics of a successful VLP antigen scaffold. Applicant presents a method for generating VLP vaccines in adaptable, predictable, stable and scaleable manners. This work is highly innovative, and there is continuing development. The method includes generating muli-valent vaccines where different vaccine protein moieties are fused to the surface of a single VLP structure conferring a multi-functional effect—the availability of immune peptides (protein elements stimulating protective immunity) and peptides that either modulate the host immune response or facilitate efficient immune cell recognition or processing. The proposed vaccines will be also bi-functional, where the protein elements of the VLP, with or without a peptide fusion or series of fusions, encapsidate a modified RNA moiety. The modified RNA can carry an mRNA of interest and that protected RNA can then be used to carry nucleic acid content, along with protein, into an immune cell that takes up the vaccine. The RNA constituents works synergistically to generate strong, lasting immunological responses by encoding either an intact pathogen or oncology antigen, proteins that stimulate host immune responses or proteins that modulate either a type Th1 or Th2 immune response to the vaccine. The method alleviates problems associated with other VLP systems by having robust production potential, improved cellular uptake, and multi-epitope valency. A selection of structurally similar, yet immunologically distinct VLP carriers allows rotation of the coat backbone for prime-boost strategies that have proven unworkable in other VLP systems.
Vaccination with bi-functional RNAs presents an alternative to DNA vaccination, with some distinct advantages. In the first instance, there is little concern that an RNA-based vaccine could cause oncogenesis because it cannot incorporate into or transform the genome. Secondly, there is good evidence that one could deliver an RNA vaccine derived from an RNA virus (such as an alphavirus) as a safe self-amplifying vaccine vector. Alphavirus replicons are cytolytic for cells, and thus the replicating RNA vaccine is intrinsically transient and self-eliminating. Alphavirus “replicon” vaccines cause powerful immune responses—both antibody and cell-mediated—associated with both increases in the amount of antigen produced as well as the production of inflammatory cytokines induced by intracellular accumulation of the viral dsRNA replicative intermediate. These features indicate that the dosage of replicative RNA required for induction of effective immune responses would be orders of magnitude lower than that required by DNA immunization. However, the major drawback associated with naked RNA vaccines is the notoriously labile nature of the nucleic acid: this severely limits the application of RNA vaccines for mass immunizations.
Alphavirus replicon vaccines are currently delivered either as naked RNA transcribed in vitro, packaged in alphavirus-like particles (replicon particles), or as plasmids containing infectious cDNAs, driven by the cytomegalovirus immediate early promoter (CMV promoter). Replicon particles are very efficient as vehicles for carrying the replicon RNAs into cells, but production is complicated, inefficient and unreliable. An efficient packaging and RNA stabilization technology is therefore required to protect alphavirus-based RNA vaccines from degradation. Two viable options present themselves: (1) to deliver recombinant alphavirus constructs as infectious cDNA plasmids; (2) to package alphavirus RNA transcribed in vitro such that it is protected from nucleases and has good stability and storage properties. An approach for the latter option is presented below.
The inventors employ as a VLP carrier the well-characterized plant virus, tobacco mosaic virus (TMV), and exploit its unique abilities to reconstitute VLP structures in vitro onto various heterologous RNA sequences.
By introducing a cysteine in the solvent exposed sequences of TMV coat, we can introduce and fuse foreign antigen epitopes ex-vivo. Epitope sequences that are not amenable to in vitro synthesis will be fused in-frame genetically to the TMV coat protein. TMV VLPs will be reassembled in vitro decorated with a single epitope (monovalent), or with a collection of different epitopes (multivalent), derived from in vitro conjugation or expressed from a genetic fusion.
As a scaffold for reassembly, the present invention includes using an RNA that encodes a protein that will enhance vaccine potency, thereby creating a bi-functional antigen delivery system that derives its activity from both protein and nucleic acid. The RNA can also incorporate an alphavirus replicon to augment translation. Essential for the encapsidation of the RNA molecule by the TMV coat protein, to generate an RNA-containing VLP, is the presence of the 75 nucleotide sequence comprising loop 1 of the origin of assembly (OAS). By combining this 75 nucleotide sequence with foreign sequences encoding protein(s) or peptide(s) of therapeutic interest, the RNA molecule can function as an effective scaffold for the generation of a TMV-like VLP. The RNA can encode any number of immunomodulating factors (e.g. IL4, IL1β or IFNγ) that ensure a highly successful immune response to the vaccine, and help generate either protective or therapeutic immunity to the pathogen, or deliver inhibitory RNA signal (RNAi) for targeted gene inhibition. This VLP strategy can be applied to effectively target immune cells and stimulate Th1 type responses.
An important requirement to inducing a Th1 type immune response is getting VLPs into cells for processing and antigen presentation. Peptides with known cell targeting have been identified (Samuel 0., Shai, Y., 2001 Bichem. 40, 1340; Magnusson et al. 2001 J. Virol. 75 7280; Bushkin-Harav et al. 1998 FEBS L. 424 243) and can be tested in vitro by direct examination of cell entry, and in vivo for augmented antigen presentation by examining the type and speed of immune response to target antigens. Targeting and fusion peptides will be tested for their ability to augment cellular uptake of TMV, as well as their ability to deliver encapsidated RNA in vitro and in vivo.
A common method to improving vaccination is to co-administer an adjuvant or a specific T-helper peptide to stimulate T-cell help. CpG DNA has been shown to be an easily administered adjuvant that improves Th1 type immune responses when co-administered with an appropriate vaccine (Krieg. 2000 Vaccine 19, 618). Most CpG DNA adjuvants have been given mixed with the vaccine and administered subcutaneously (s.c.), although the single strand thiolated DNA can also be fused to a protein carrier through SPDP conjugation chemistry. Also, several universal T-helper peptides have been identified (Kulkarni, A. B., et al., 1995 J. Virol.69,1261; Panina-Bordignon, 1989 Eu. J. Imm. 19, 2237; Boraschi, 1988 J Exp Med. 168,675; Weiner, G. et al., 1997 Proc. Nat. Acad. Sci 94 10833). Immunostimulatory peptides, usually fragments of cytokines, have also been identified that direct Th1 type immunity after vaccination in combination with pathogen or self-antigen peptides or subunit vaccines (IL1β, Boraschi, 1988 J Exp Med. 168,675). Coat fusions containing T-helper or adjuvant peptides or CpG DNA oligo will be used to augment the immunogenicity of co-expressed peptides, or encapsidated RNA.
Lastly, it is well established that cytokines play an important role in determining which arm of the immune system is activated after vaccine delivery. Interleukin 4 (IL4) has been implicated in directing Th2 type immune responses and interferon gamma (IFNγ) is an important contributor to Th1 responses (Spellberg and Edwards.2001 Clin Infect Dis 32, 76). By introducing IL4 and IFNγ RNA into cells by encapsidation into a TMV VLP, we may be able to influence the type of immune response that is generated. Applicant can test both antibody isotype responses to antigen, which are a reflection of Th1 or Th2 antigen presentation, as well as assess CTL responses that are primarily a consequence of Th1 immunity.
Cell fusion peptides, T-help, adjuvants, pathogen antigens, tumor antigens and encapsidated cytokine RNA will be tested systematically in combination with antigens from Papillomavirus and melanoma murine disease models. Immunogencity and challenge models will establish incremental improvements over vaccination with single peptides, and define the best peptide/RNA combinations for generating Th1 or Th2 immune responses.
The availability of such a flexible and effective vaccine platform provides opportunities to apply non-live vaccines for humans and livestock thus reducing side effects and increasing effectiveness. New vistas of medical practice, including applications for breaking self-tolerance and driving immune responses against weak antigens, may be opened by the synergistic and high specific-activity of the disclosed vaccine platform.
The invention relates to a method where a specified virus, such as a tobacco mosaic virus (TMV), is disrupted into a plurality of subunits. Each subunit contains a genetically fused peptide or is subjected to a conjugation reaction in order to attach a predetermined epitope, peptide or nucleotide thereto. A plurality of subunits are processed in this manner to produce a plurality of subunit groups, where one subunit group has attached thereto a predetermined peptide; another subunit group has a second peptide; another subunit has a predetermined epitope attached there to; and another subunit group has a nucleotide attached thereto, and so on, for as many subunit groups necessary to provide the building blocks for a plurality of virus vaccines.
An alternative strategy is to employ TMV RNA modified to initiate internal ribosomal entry by introducing specific sequences known to cause such an effect. These internal ribosomal entry sites (IRES) are effective in causing internal translation products from a polycystronic RNA in mammalian cells (Yang et al., J Virol 1989 63(4):1651-60). Introduction of an IRES into a TMV genome in frame with an RNA encoding either a full length gene product or immunostimulatory cytokine or other kind of immunomodulatory protein allows for translation of that protein. Because these IRES are introduced into non-replicating RNA, the amount of TMV and proportional transcript taken up by a cell after vaccination is conceivably lower than with a self replicating RNA such as encoded by an alphavirus replicon, but the level of translation product should be sufficient to induce the-correct response.
The present invention includes research and development of technological solutions to help the USA to produce and supply effective vaccine reagents in response to unanticipated pathogen threats. Applicant specifically addresses issues that limit bio-defense application of nucleic acid vaccines: poor environmental stability and high dosage requirements. In addressing these issues, we will draw upon the core of knowledge that the inventors possesses in the field of positive stranded RNA viruses and their applications in biotechnology to develop a set of molecular tools to improve nucleic acid vaccines. Applicant will also demonstrate our capacity to produce protein subunit vaccines that will-provide effective antibody responses. Production of protein subunit vaccines is inherently slower than nucleic acid vaccines and so, practically, will only be available within a delayed period following encounter with a new pathogen threat. However, the inventor's non-transgenic plant-based vaccine expression platform (GENEWARE®) has the capability to express a variety of proteins, including virus-like particles (VLP)—known to be potent inducers of antibodies in vaccinated individuals—rapidly. Applicant has recently used a modified TMV expression vector to produce 16 different human therapeutic vaccines in tobacco plants, and have shown excellent safety in a Phase I clinical trial (BB-IND #9283). Unlike other competing technologies, GENEWARE® does not require specialized fermentation facilities, and uses the efficient, rapid protein production strategy of the plant virus TMV to harness plant protein production machinery to produce vaccine proteins. A typical harvest time, post inoculation is less than 21 days. Since the same virus is used from pilot testing to large-scale manufacturing, there is little or no transition time between validation and manufacturing scale up. Most of the delay in delivery of vaccines via GENEWARE® technology would be in the growth of plants, and establishment of antigen-specific purification protocols. These aspects of the technology result in a low cost of production for plant-derived VLP vaccines.
g/ml. Samples were then negatively stained with 1% phosphotungstic acid, dried and stored at RT until visualized using a Philips CM120 TEM, at 37,000× magnification. The bar represents 130 nm.
g/ml ova peptide for 5 hours in the presence of Brefeldin A. Cells were then fixed, incubated with anti-CD4-FITC or anti-CD8-FITC antibodies, and then refixed and permeabilized. Cells were then incubated with anti-IFN-PE or anti-TNF-PE, and then visualized for PE and FITC staining by flow cytometry.
In order to facilitate understanding of the invention, certain terms used throughout are herein defined:
“GM-CSF” means Granulocyte-Macrophage Colony Stimulating Factor. GM-CSF may increase the immunogenicity of antigens by stimulating antibody production mechanisms.
“Non-native” means not derived or obtained from the same species.
“Native” means derived or obtained from the same species.
“IgG” means immunoglobulin-G.
“Intergenic sequences” means the non-coding DNA sequences, wherein the viral origin of replication is situated, that are located between open reading frames of viruses.
“OAS” means origin of assembly sequence. The origin of assembly sequence is necessary for assembling the RNA molecule with viral coat proteins into a viral particle.
“Reconstituted protein” means the isolated and hydrated form of protein from a complex protein mixture
“IL4” means interleukin 4, a cytokine that activates immune cells, especially B cells
“IL1b” means Interleukin 1, beta subtype, a cytokine that activates immune cells
“IL1b peptide” means a 9 amino acid section of IL1b that can stimulate T cells
“IFNγ” means interferon, gamma subtype, a cytokine that activates immune cells, especially T cells
“TMV” means tobacco mosaic virus
“VLP” means virus like particle
“Th1” means T-helper type one immune response, which is characterized by both antibody and cellular immunity
“Th2” means T-helper type two immune response, which is characterized by primarily an antibody response
“IVE” means in vitro encapsidation
“RNA” means ribonucleic acid
“DNA” means deoxyribonucleic acid
“HA” means a peptide sequence derived from influenza hemaglutinin
“V5” means a peptide sequence derived from simian virus 5
“myc or Myc” means the peptide derived from the myc oncogene
“N” position means the position the peptide or modification is inserted, at the N terminal location of coat protein
“L” position means the position the peptide or modification is inserted, at the extracellular loop location of coat protein
“G or GPAT” means the position the peptide or modification is inserted, at four amino acids from the C terminal location of coat protein
“C” position means the position the peptide or modification is inserted, at the C terminal location of coat protein
“Cys” means the amino acid Cysteine
“20S” subunit describes the sedimentation profile of the 34 subunit coat protein disk in a density gradient
“4S” subunit describes the sedimentation profile of the 4 subunit coat in a density gradient, which is an intermediate to the formation of a 20S disk
“kDa” means kiloDalton, which refers to the molecular weight or mass of the protein
“TEM” means transmission electron microscopy
“RT” means room temperature
“4C” means 4 degrees Celsius, or near zero Fahrenheit
“PAGE” means polyacrylamide agarose gel electrophoresis
“SDS” means sodium dodecyl sulfate, a detergent
“PEG” means poly ethylene glycol (molecular weight 6000-8000) “NaCl” means sodium chloride, or salt
“DEAE” mean diethyl aminoethyl, a molecule used on anion exchange resins
“PO4” means phosphate
“pyro PO4” means pyrophosphate
“SU” mean subunits
“CRPV” means cottontail rabbit papillomavirus
“ROPV” means rabbit oral papillomavirus
“HPV” means human papillomavirus
“OVA” means ovalbumin
“GJ” means green juice, or total plant homogenate
“S1” means clarified plant extract supernatant
“S2” means supernatant derived from the S1 insoluble material by resuspension at pH 7
“BSA” means bovine serum albumin
“MW MALDI” means molecular weight mass determination by Matrix Assisted Laser Desorption Ionisation mass spectrometry
“w/v” means weight per volume
“OD” means optical density
“DDT” means Dithiothreitol
“RNAse” is an ubiquitous cellular enzyme that degrades RNA
“RNAsin” is a commercially available RNase inhibitor
“DEPC” is diethyl pyro carbonate, a chemical inhibitor of RNAse activity
“Nab” means neutralizing antibody
“L1” means papillomavirus capsid protein L1
“L2” means papillomavirus capsid protein L2
“E1,2,4,6,7,and E8” are papillomavirus early gene products
“CTL” means cytotoxic T lymphocyte
“SFV” means semliki forest virus
“IRES” means internal ribosomal entry site, which allows for the initiation of translation in the middle (or anywhere that is not at the first ATG) of the RNA
“ORF” means open reading frame, the functional unit of RNA, which when translated encodes a protein
“B16” means the mouse melanoma tumor cell line named B16
“SPDP” N-succinimidyl-3-(2-pyridyldithio)propionate
“BCA assay” Protein assay based on bicinchoninic acid
The present invention relates to a novel method for for the colorimetric detection and quantitation of total protein.
The present invention relates to a novel method for construction of a plurality of vaccines and pharmaceuticals using viruses, such as the tobacco mosaic virus (TMV). In broad terms, the invention is practiced in a manner depicted generically in
The description of the present invention is first provided in general terms, followed by a more detailed description that includes many biochemical procedures.
Standard methodologies can produce a pseudo-multivalent vaccine product by a chemical conjugation process outlined in
The described invention exploits the unique properties of the tobacco mosaic virus (TMV) that is amenable to the procedures outlined in
Further basic steps in the method of the present invention are depicted in
It should be noted that RNA is inherently unstable as a ‘naked’ element, or one not coated with a protective protein coating. However, it has an advantage over DNA in nucleic acid vaccines since it promotes translation of the desired product within immune cells, but is degraded and does not risk the immunized host with DNA recombination and the associated oncologic events. ‘Naked’ or uncoated nucleic acid vaccines of RNA or DNA types are very inefficient, where milligram (mg) quantities of DNA are required for any immune response in humans. Out of the mg of vaccine administered, picograms or less are taken up by immune cells. This results in expensive manufacturing and formulation costs, and very inefficient unpredictable immune responses. This invention allows the ‘naked’ RNA encoding important antigens or immune enhancing proteins to be coated and protected within the VLP structure of TMV. Such coating enhances the stability of the RNA and improves the delivery efficiency.
VLP vaccines are not dependent only on chemical conjugation to add immune peptides to their surface. The art describes methods for generating VLP vaccine through the genetic fusion of immunologically relevant peptides to the surface of VLPs. This process is described in
This invention overcomes these difficulties by allowing truly multi-valent and multi-functional vaccines to be derived. TMV is amenable to the same procedures described in
It should be understood that the above description is only a basic framework of steps upon which the present invention functions, and a basic understanding of the platform for constructing vaccines and pharmaceutical products in accordance with the present invention. The steps outlined in the flow diagrams in
Following are a series of detailed examples, which illustrate the general flow diagrams described on the preceding pages.
The current industry standard for success with peptide fusions is 40-50%. To improve on this a series of fusions were tested at multiple insertion locations on the TMV U1 coat protein and each fusion was extracted under multiple conditions, to determine the influence of fusion position on virus solubility. This example describes the influence of genetic fusion position on the isolation of recombinant TMV viruses (step S15,
Table 1 summarizes the influence of epitope location on the solubility and relative recoveries for HA and two additional model epitope fusions, V5 and Myc. The V5, HA and myc epitope TMV fusion proteins were tested for reactivity to peptide specific antibodies by Western analysis, to confirm the identity and integrity of each fusion peptide (data not shown).
Following the confirmation of expression with the three model fusions the list of fusions was expanded to include clinically relevant epitopes of papillomavirus and melanoma as well as immuostimulatory and cell fusion epitopes aimed at incorporating biological functionality to reassembled fusion products. Table 2 summarizes the solubility results for all the epitope fusions. Of the 18 target epitopes attempted 15 were successfully expressed as soluble products, an 83% success rate. This represented a doubling of the previous industry standard of 40% expression/solubility. This improvement is due to the rotation of the insert position, performed in parallel with the extraction with two different pH buffers.
Table 2. 15 of 18 peptides have been expressed in frame with TMV U1 coat at either the N-terminus (N) the GPAT position (G) or at the C terminal location (C). Those fusions that were soluble in either pH 5 or 7 extraction buffer from leaf punch grinds (˜200 μg leaf tissue) are indicated in the Solubility column. Those fusions that were also successfully scaled up (>500 grams leaf tissue) are also indicated.
Molecular fusion of epitopes to TMV sometimes fail to accumulate when aromatic (for example W) or hydrophobic amino acids are present in the peptide. For example, p15e, a mouse melanoma antigen, contains the aromatic amino acid tryptophan (W). This peptide, when introduced onto the N or C-terminal positions on U1 coat, caused virus instability and no TMV systemic infection was observed. Applicant reasoned that to create a more favorable environment for peptide solubility, flanking amino acids could be added to increase hydrophilic interactions, counteracting the negative effects on virus assembly or stability when amino acids like W are introduced onto the solvent exposed surface of coat protein. Aspartic Acid (D) and Glutamic Acid (E) are amino acids that are charged, and were used to show that such a method will rescue the insoluble fusion of p15e to TMV coat (
Only a percentage (70-80%; see Example 1) of genetic fusions are capable of functional VLP formation for many plant viruses. Many fusions fail to accumulate while others are simply insoluble. The present invention includes construction of coat protein fusions containing cysteine (Cys) residues as either N-terminal or surface loop fusions. The initial fusions to TMV U1, and to other tobamovirus coat proteins showing good expression in the U1 vector, are composed of glycine-cysteine-glycine (GCG) or GGCGG as N- and surface loop fusions (
Initially, SPDP conjugations are tested for reactivity to cysteine containing TMV that is not disassembled. Cross-linking reactions are carried out using short chain, long chain and sulfo-NHS forms of SPDP as described (Hermanson, G. Bioconjugate Techniques 1996 Rockford Ill., Academic Press, and references therein). Peptide-SPDP adducts are mixed with cysteine TMV U1 virus and then analyzed 16 hours later for a size shift that represents physical association of the peptide with the virus. The procedure is then extended to 20S disks. An alternative approach was to use a less specific chemical conjugation strategy employing glutaraldehyde. The HA peptide was mixed with either TMV or N terminal cysteine TMV in the presence of glutaraldehyde. After a four hour incubation with glutaraldehyde, a HA peptide-TMV cysteine conjugate was formed and was visible as an increase in mass by Coomassie, as well as by an increase in apparent molecular weight by Western analysis (
An alternative strategy is to assemble N cysteine coat into 20S discs, reassemble these discs with other discs that carry functional epitopes (ie, by molecular fusion) onto an RNA, and incubate the fully reassembled mixture with SPDP-associated peptide or moiety in order to add a new functionality. This is especially useful if the SPDP conjugation renders 20S discs chemically inert and unable to reassemble with other discs, or if the peptide that is carried interferes sterically with reassembly. As well, the ability to add a variety of agents after reassembling a monomer or a multimer has great utility. For example, SPDP conjugation of ssDNA such as CpG oligonucleotides may allow for the augmentation of immune modulation, which is greater than simply mixing the CpG with the vaccine. This could lead to better efficacy and or the potential to reduce the dose. This example illustrates the steps S3 (
To determine the influence of the fusions on virus structure, transmission electron microscopy (TEM) was performed (
The extraction and processing of TMV U1 has been extensively discussed in the above mention commonly assigned U.S. Pat. Nos. 6,303,779, 6,033,895 and 6,037,456, which are incorporated herein by reference in their entirety. The processing is summarized in
The process outlined in Example 5 was employed for a selection of the coat protein fusions listed in Table 2. Material balances were performed to determine the partitioning of the virus between the S1 and S2 process streams, in addition to the total process recovery. The identity of each fusion was confirmed by MW MALDI. The results for these purifications are summarized in Table 4. From the table it is clear that the processing characteristics are epitope fusion and location dependent. A material balance on the extraction gave initial recoveries (S1+S2 process streams) from 90-100% (e.g. HPV ep2 N) to lower than 10% (e.g. V5 N). Partitioning between the S1 and S2 streams also varied substantially. Overall recoveries also ranged from 0.5% to 79%. Based on this data the cysteine N, Myc N and V5N coat protein fusions were carried forward to optimization studies to determine conditions which would improve overall process recoveries. This optimization is detailed in Examples 7 and 8 and illustrates process modifications that can be employed in order to isolate TMV virus displaying genetic fusions (step S15,
Fusion location designation; N, N terminus; C, C terminus; GPAT, N terminal to GPAT sequence. # indicates the purification run number for fusions isolated more than once.
The incorporation of sodium chloride into the extraction buffer was tested as a means to improve virus recovery and alter virus partitioning. GENEWARE-infected N benthamiana plants were harvested and the biomass split, to perform a head to head comparison of extraction in the presence and absence of salt. One half of the plant material was extracted in chilled water containing 0.04% sodium metabisulfite and the remaining biomass was extracted in a 50 mM-acetate buffer, pH 5.0, containing 4% w/v NaCl and 0.04% sodium metabisulfite. Processing was performed following the procedure outlined in Example 5. A comparison of the S1 and S2 fractions by SDS-PAGE, for the Cysteine N TMV fusions (
A material balance for extractions in the presence and absence of salt is given in Table 5. From the data for Cysteine N, it is clear that the overall process recovery was improved substantially with the addition of salt; although the total virus extracted in both cases was identical, the virus loss in the absence of salt was 44% (remained associated with the P2 pellet) compared to only 7% with 4% w/v sodium chloride. Table 5 also has data for recovery and virus partitioning of the Myc N and V5N coat protein fusions during extraction. The benefits of sodium chloride are again evident, indicating that this process modification has general applicability.
As illustrated in
Table 6 compares the recoveries obtained from the two-step PEG precipitation for wild-type TMV U1 and two coat protein fusions, Myc N and V5N. The standard procedure outlined in
This example illustrates in greater detail steps S7 and S8 (
This process was employed to generate a number of free coat protein fusions from purified virus. Table 7 summarizes the process recoveries for a selection of the epitope fusions for which coat protein was generated.
Fusion location designation; N, N terminus; C, C terminus.
The quality of the coat protein was assessed by its ultraviolet absorption spectrum (Durham, J Mol Biol, 1972, 67: 289). The spectrum should have an absorbance maximum at 282 nm, an absorbance minimum at 251 nm and a maximum to minimum ratio between 2.0 and 2.5. A lower ratio indicates residual RNA contamination of the coat protein preparation.
Fusion location designation; N, N terminus; C, C terminus.
Prior to use in reassembly reactions, the coat protein preparation is converted from 4 S subunits, consisting of 3 to 4 coat proteins, to 20 S disks (see
This Example, together with Examples 11-13, illustrate the methods for the generation of multivalent and bifunctional vaccines i.e. step S18 (
TMV U1 coat protein was generated from wild type virus isolated from N. tabacum var. MD609 plants, as described in Example 9. Wild type RNA was isolated from the same virus with the RNeasy Plant Mini Kit (Qiagen, Valencia, Calif.). Reassembly reactions were performed in 200 μl volumes, at a coat protein concentration of 1100 μg/ml and a RNA concentration of 50 μg/ml, in a 96 well plate format. The reactions were buffered with 0.1 M phosphate or pyrophosphate, pH 7.2 and the coat protein preincubated for two days at room temperature prior to use. This preincubation results in the formation of 20S disks from the 4 S subunits (
To determine the functional significance of the different buffer combinations, aliquots of the reassembly reactions were analyzed by the local lesion host assay (Table 9). The reassembly reactions, naked RNA and virus controls were serially diluted and applied to the leaves of N tobacum ‘Xanthi’ NN plants, with carborundum employed as an abrasive. Five days post inoculation the lesion numbers were counted and provided a semi-quantitative measure of the titer of functional virus in the reassembly reactions.
PO4, 0.1 M phosphate buffered; pyro PO4, 0.1 M pyrophosphate buffered; PO4 RNasin, 0.1 M phosphate buffered with 0.4 U/μl RNasin ribonuclease inhibitor.
Comparing the infectivity of free RNA to the reassembly reactions, which contained an equivalent molar concentration of RNA, clearly illustrates the improvement in infectivity with RNA encapsidation. Within the reassembly reactions, a marked improvement in infectivity was evident for the phosphate buffer when RNasin was present, which correlated with the improvement in RNA integrity and A310 nm OD maximum. The observed infectivity with RNasin was comparable to that of the virus control. The pyrophosphate buffer also improved infectivity due to the accelerated reassembly, which aided in the protection of the RNA.
A central aim of this work is the generation of a multifunctional TMV-based reassembly product, which displays epitopes with different functionalities e.g. a cell targeting or immunomodulation sequence together with an antibody or CTL target. As a first step, the ability of various coat protein fusions to reassemble onto TMV RNA was examined. The fusions chosen were ELDKWAS and HPV ep2 at the N terminus and Myc at the C terminus. The reassembly reactions were performed in 200 μl volumes, at a coat protein concentration of 1100 μg/ml and a RNA concentration of 50 μg/ml, in a 96 well plate format. The reactions were buffered with 0.1 M phosphate, pH 7.0 and the coat protein preincubated for two days at room temperature prior to use. In a subset of the reactions the ribonuclease inhibitor RNasin was incorporated. The reassembly reactions were followed by measuring the change in absorbance at 310 nm over time, which corresponds to the increase in the average length of the reassembly products.
The A310 nm kinetics together with the RNA profile suggest that RNasin increases the proportion of full-length rods formed during reassembly. To confirm this, samples were analyzed by electron microscopy (
The reduction in full-length rods presumably results from the reduced pool of full length RNA. This would be expected to reduce the number of functional i.e. infectious reassembly products. Analysis of the reassembly products by the local lesion host assay confirmed this reduction; omission of RNasin reduced the average number of lesions observed by a factor of 9 (Table 10).
PO4, 0.1 M phosphate buffered; PO4 RNasin, 0.1 M phosphate buffered with 0.4 U/μl RNasin ribonuclease inhibitor. All dilutions were at 10−3. At this dilution no lesions were detected for free wild type RNA. N, N terminal fusion; C, C terminal fusion.
Reassembly reactions were also performed with the HPV ep2 and the Myc coat protein fusions, in the presence or absence of RNasin. Similar to the ELDKWAS coat protein fusion, the presence of RNasin during the reassembly resulted in A310 nm profiles with a higher final OD and improved RNA integrity. From a functional standpoint the reassembly products generated in the presence of RNasin showed greater activity by the local lesion host assay (Table 10). For Myc and HPV ep2 the average number of lesions were 15 and 6 fold higher respectively when RNasin was present. These infectivity studies clearly illustrate the ability of a TMV coat protein carrying a solvent exposed epitope to reassemble and encapsidate a functional RNA.
The coat protein preparations do have a plant-derived ribonuclease activity associated with them, which can be partially mitigated by the inclusion of RNasin in the reassembly reaction. Alternative approaches can also be used to reduce the ribonuclease activity associated with the starting virion preparations, from which the coat protein preparations are generated. The virus preparation can be treated with bentonite, which inhibits ribonuclease activity (Jacoli, G., Ronald, W., and Lavkulich, L.: Inhibition of Ribonuclease Activity by Bentonite, Can J Biochem 51, 1558, 1973). Alternatively the virus preparation can be treated with diethylpyrocarbonate (DEPC) at 0.05%-0.1% v/v, which inactivates RNases by reacting specifically with the histidine residues in the enzymatic site. Residual DEPC is removed by dialyzing the treated virus extensively against any buffer containing a primary amine group, e.g. Tris(2-amino-2-hydroxymethyl-1,3-propanediol), with which DEPC reacts.
Reassembly reactions to generate a multivalent TMV-based vaccine were performed using a TMV RNA scaffold. The ELDKWAS, Myc and HPV ep2 coat protein fusions were combined pair wise at a 1 to 1 ratio.
Animals may be protected against infection with papillomaviruses by vaccination with either or both papillomavirus structural proteins, L1 and L2 (Da Silva D M et al., 2001, Journal of Cellular Physiology 186:169-182; Koutsky L A et al., 2002, New England Journal of Medicine 347:1645-51). Protection against papillomavirus infection primarily requires a specific humoral response, which results in production of virus neutralizing antibodies (Nab) directed at epitopes in the structural proteins. A cellular immune response directed against the structural proteins may also contribute to vaccine-induced immunity. Live recombinant virus and DNA vaccine vectors carrying L1, or one or more of the non-structural genes E1, E2, E4, E6, E7 and E8, can induce protective immunity in vaccinated animals; in these cases both cellular and humoral immune responses are detected (Sundaram P et al., 1997, Vaccine 15:664-71; Moore R A et al. J Gen Virol 20:2299-301). It is well established that a humoral response directed against papillomavirus structural proteins is both necessary and sufficient for protective immunity against papillomavirus infection (Embers et al., 2002 Journal of Virology 76:9798-9805). A cellular immune response against virus-encoded proteins will enhance the level and robustness of the protective immune response, but will not prevent initial infection (Tobery T W et al., 2003, Vaccine 21: 1539-47).
Bivalent or Multivalent Reassembled Vaccines
The most important papillomavirus Nabs bind conformational epitopes in L1, and recognize only intact virus, or correctly assembled virus-like particles (VLP). These Nabs recognize epitopes in hypervariable loops on the capsid surface, and generally will only neutralize closely related papillomavirus types. Antibodies that bind linear epitopes in the N-terminal region of L2 may also neutralize virus infectivity. Most importantly, Nabs directed against L2 epitopes show the ability to cross-neutralize distinct viral strains (Embers M E et al., 2002; Journal of Virology 76:9798-9805; Kawana Y et al., 2001, Journal of Virology 75: 2331-2336; Kawana K et al., 1999, Journal of Virology 73:6188-6190; Kawana K et al. 2001, 1496-1502; Roden R B S et al., Virology 270:254-257). Embers et al. (2002; Journal of Virology 76:9798-9805) demonstrated that peptides that represent linear epitopes in the L2 proteins of the rabbit papillomaviruses rabbit oral papillomavirus (ROPV) and cottontail rabbit papillomavirus (CRPV) could induce good protective immunity against challenge with the homologous virus, but not against the heterologous virus.
Recombinant TMV U1 that display the linear, neutralizing rabbit papillomavirus epitopes CRPV L2.1; CRPV L2.2; ROPV L2.1 and ROPV L2.2 (Embers M E et al., 2002 Journal of Virology were constructed (Table 2). Each recombinant virus will induce neutralizing antibodies that will protect animals against challenge with high titer of homologous virus. However, each vaccine may not induce sufficient titer of Nabs to neutralize the heterologous virus.
Assembling at least two different coat proteins, each of which displays a different peptide, on a structural RNA that contains the TMV OAS, can make a multivalent recombinant vaccine that will induce protective immunity against both CRPV and ROPV. For example, the methods described in Example 9 may be used to isolate free coat protein from recombinant TMV virions that display the CRPV L2.1 peptide at the “GPAT” position proximal to the C terminus of TMV U1. Likewise, free coat protein may be isolated from recombinant TMV virions that display the ROPV L2.1 peptide at the “GPAT” position proximal to the C terminus of TMV U1. Wild type TMV RNA, or a recombinant RNA that contains that TMV U1 origin of assembly sequence (OAS) may be used as the scaffold on which the reassembled bivalent vaccine is built, according to methods described in Example 10 and 11. Similarly, additional recombinant U1 coat proteins that display peptides with the ability to induce Nabs in vaccinated animals may be incorporated into the reassembly reaction to generate a multivalent vaccine virus or virus-like particle. Animals that are vaccinated with bivalent or multivalent vaccines will produce antibodies that recognize the various peptide antigens fused to the recombinant vaccine molecule; these antibodies are capable of neutralizing both CRPV and ROPV. New Zealand white rabbits will thus be protected against infection against two distinct virus species after vaccination with a single vaccine moiety.
Multifunctional Vaccine: Induction of Humoral and Cellular Immunity
The sequences of human papillomavirus type 16 L2 that are homologous with the CRPV L2.1, ROPV L2.1; CRPV L2.2 and CRPV L2.2 peptides are capable of binding to specific receptors, and on binding to the cell surface are able to mediate cellular entry of proteins fused to these sequences by receptor-mediated mechanisms (Kawana Y et al., 2001 Journal of Virology 75: 2331-2336; Yang et al. 2003, Journal of Virology 77:3531-3541). It is thus expected that virions and reassembled virus-like structures that display these sequences will be able to bind to the surface of rabbit cells, and mediate entry of the reassembled virus structure into the cell. The additional cell fusion function of reassembled particles with one or more of the CRPV L2.1, ROPV L2.1; CRPV L2.2 and CRPV L2.2 peptides displayed by the assembled virus or virus-like particles allows delivery of a functional RNA payload to the cytoplasm of transduced cells.
To augment the protective antibody mediated immunity induced by the L2 peptides displayed on the surface of the reassembled viral structure, the RNA scaffold will have additional biological activity. For example, the scaffold RNA is a recombinant RNA molecule that encodes the Semliki forest alphavirus (SFV) RNA sequences that are required for autonomous replication, with the CRPV L1 gene that may be expressed under the control of the 26S RNA promoter from SFV, and the TMV U1 OAS inserted downstream of the CRPV L1 gene. This construct is shown in
Once the particles are in the cytoplasm, the recombinant RNA molecule is translated, and the RNA undergoes one or more cycles of replication mediated by the SFV non-structural proteins (NSP) replicase activity. The subgenomic RNA encoding the CRPV L1 RNA and TMV OAS is transcribed and the CRPV L1 RNA translated. The intracellularly expressed L1 protein is then available for processing and presentation via MHC Class I to T-cells, thereby priming a cellular immune response against the L1 protein. Replication of the recombinant SFV RNA delivered to the cytoplasm of transduced cells induces the innate immune response, via pathogen surveillance signaling molecules such as the dsRNA-induced protein kinase (PKR), resulting in secretion of inflammatory cytokines such as interferon gamma. This augments the specific cellular immune response induced against the L1 ORF. Thus, a broad, robust immune response against both structural proteins (L1 and L2) is induced. Rabbits vaccinated with these multifunctional vaccines are protected against challenge with both CRPV and ROPV viruses.
An alternative method to generate a functional RNA is to insert an IRES and coding sequence for L1 into TMV RNA, which also expresses a molecular fusion of L2 peptide epitope onto coat protein. This method has the advantage of encapsidating the RNA in vivo, and does not rely on reencapsidation to protect the RNA from degradation until after cellular uptake mechanisms allow for transcription of the gene. In a third strategy, the coat protein also carries an N terminal cysteine for conjugation of a T-helper epitope, a cell fusion epitope, an adjuvant, or the full-length gene product of a non-structural protein such as E7.
Papillomavirus nonstructural proteins, including E1, E2, E4, E6, E7 and E8 are known to mediate protective immunity, or lesion regression and clearance in vaccinated animals (Han R et al., 2002, Cancer Detect Prev 26:458-67; Han R et al., 2000. Journal of Virology 74: 9712-6). In the same manner as described above, mRNAs or autonomously replicating RNAs encoding other papillomavirus proteins which are known to mediate protective immunity, and which can induce regression or cure of virus infection, may be encapsidated within virus structures (
Melanoma antigens that stimulate good protection against tumor growth are typically characterized as CTL epitopes. CTL responses are highly dependant upon the context for antigen presentation, including immunostimulation during vaccine presentation to the immune system. This is characterized by a need for either immunostimulatory cytokines, such as GM-CSF or IFNγ, adjuvants that specifically activate T cells, such as CpG oligo, or immunomodulatory peptides or proteins, such as I11B or MIP1a or IP10, to be delivered along with the vaccine, or fused directly to the vaccine product. Melanoma CTL epitope fusions, either molecular or chemical conjugates, are reassembled onto wild type TMV RNA and tested for appropriate stimulation of peptide specific CTL responses. The same melanoma CTL epitope fusions are then reassembled onto an RNA that contains both a TMV origin of assembly, and a mammalian translatable codon for IFNg, GM-CSF, MIP1a, or IP 10. After vaccination with epitope TMV or epitope TMV/IFNγ (for example), the level of CTL response is measured and compared. Translation of the functional RNA produces a protein that results in immune activation, thereby increasing the CTL response.
Alternatively, the RNA encodes a second full-length antigen that primes the cellular or humoral immune response for broader immune coverage. For example, melanoma tumors express several specific antigens that generate both CTL and antibody responses in challenged individuals. In murine tumors, such antigens include p15e, tryrosinase and GP100. Several CTL epitopes, as well as antibody stimulating domains, exist for each tumor specific antigen. Defined CTL epitopes, e.g. the p15e CTL epitope, are fused to the surface of TMV, and the encapsidated RNA encodes the entirety of gp100, or tyrosinase coding sequences. CTL reactivity to the p15e epitopes is measured, and further cellular or humoral reactivity to the gp100 or tyrosinase epitopes encoded by the RNA demonstrate RNA expression and activity of the resulting gene product.
Cellular or humoral assays indicate the level at which the vaccine is stimulating an immune response. Another way to show immune reactivity is by challenging animals with the tumor encoding those antigens and monitoring the rate of tumor growth, or the morbidity that that tumor causes. Such models exist for melanoma, and are widely used to prototype the effectiveness of melanoma vaccines. The B16 melanoma model expresses p15e, tryosinase, and gp100, and requires an effective CTL response after vaccination to reduce or eliminate the rate of tumor growth. Animals vaccinated with CTL epitope fusion vaccines are challenged with tumor, and an effective immune response will decrease the rate of tumor growth or morbidity compared to controls. If either an immunostimulatory RNA or full-length gene product encapsidated by a TMV coat or a TMV coat fusion is effective, then the rate of tumor growth should decrease compared to a protein vaccine alone, or the overall morbidity should decrease. These finding will corroborate the cellular and humoral response data, considering that these responses are essential to reducing or eliminating tumor.
As described above for papillomavirus applications, the functional encapsidated RNA can be self-replicating, such as an engineered alphavirus containing a TMV origin of assembly, or can contain an IRES, to stimulate translation from an internal site in TMV RNA (see
Immunogenicity to V5 and Myc U1 Coat Fusions: Responses to Antibody Epitopes
To verify that coat fusion peptides can stimulate appropriate immunity, we tested myc and V5 U1 peptide fusions, with known antibody binding properties, as vaccines in mice, and then looked for anti-myc and anti-V5 antibody responses. V5 and myc TMV U1 coat fusions were prepared by extraction methods, optimized for the recovery of the fusion of interest. Material was quantitated by the BCA protein assay, evaluated for peptide integrity by MALDI-TOF and for purity by SDS-PAGE. 10 g of TMV protein was then injected into Balb-C mice three times, every two weeks. After the second and third vaccines, animals were bled and sera was collected and analyzed for peptide specific reactivity by ELISA. The results of serum titers after the third vaccination are show in
Results from this study indicate that at all three positions, V5 and myc peptide fusions to TMV U1 coat can elicit the appropriate anti-peptide antibody response even when given without adjuvant. Varied response levels in individual mice are typical of subunit vaccines, and have been observed for other antigen vaccines. Overall, the average response in each vaccine group tested was not significantly different by position of the peptide fusion, even though the maximum response levels differed significantly in each group. Interestingly, responses to the TMV carrier were generally lower in magnitude than the anti-peptide response (data not shown). Of note, these vaccines were administered without adjuvant, and the high levels of responses in each group show that the viral carrier can provide humoral immune stimulation that is antigen specific.
CTL Response Assay Development for Ova Peptide U1 Coat Fusions
In addition to testing the ability of antibody-target peptides to stimulate appropriate humoral responses in vaccinated mice, we also tested the ability of a CTL epitope, derived from the chicken ovalbumin protein, to stimulate appropriate cellular immunity in appropriately MHC restricted mice. 20 g Ova-N or Ova-G TMV fusions were administered 4 times every two weeks without adjuvant to mice, and then spleens were harvested from vaccinated animals five days after the final vaccine. Cells were isolated, cultured with either media or media plus ova peptide for 5 hours in the presence of the Golgi transport inhibitor Brefeldin A, and then cells were fluorescently stained with FITC conjugated antibodies against surface expression of CD4 and CD8 T cell receptors, in conjunction with PE staining of the intracellular cytokines IFN gamma or TNF alpha. Stimulation with ova peptide should upregulate these cytokines in T cells that are specific for the peptide, and be measured by an increase in cell number by Fluorescence Activated Cell Sorting (FACS). 5×105 events were collected, about 20% of which are T cells.
Both CD4 and CD8 cells were monitored for increased intracellular expression of IFN γ (gamma) and TNF α (alpha). As shown in
Considering that no adjuvant was administered with the vaccine, these modest increases in cytokine levels suggest that the vaccine is stimulating an appropriate cellular response. Administration of an adjuvant with the vaccine, or the fusion of immunostimulatory peptides to the TMV vaccine, is expected to increase the percentage of activated T cells. For example, the T cell activating adjuvant, single stranded CpG DNA oligo 1758, specifically augments cellular responses in ova and other CTL systems. For our system the nucleotides are either mixed with the vaccine, or fused directly to TMV U1. In other systems, the IL1b peptide has been shown to augment both antibody and CTL responses but only if the IL1b peptide is physically linked to the ova peptide vaccine, such as in a multivalent vaccine.
This application claims priority to U.S. Provisional Application No. 60/386,921, filed Jun. 7, 2002, which is incorporated herein by reference in its entirety.
This invention was made with United States Government Support under cooperative agreement number 70NANB2H3048 awarded by the National Institute of Standards and Technology.
| Number | Date | Country | |
|---|---|---|---|
| 60386921 | Jun 2002 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10457082 | Jun 2003 | US |
| Child | 11410572 | Apr 2006 | US |
