[Virus-like particles--a new strategy for production of vaccines against influenza virus]

Numerous studies demonstrated that simultaneous expression of some viral proteins in the cell with the aid of a process of self-assembly might lead to the formation of the virus-like particles (VLP) even in the absence of the viral genome. The morphological and antigenic similarity between VLP and native virions represents a promising approach to the new type of vaccines. In the last decade, the threat of the influenza strains with pandemic potential becomes more important. Therefore, the technology for obtaining a new generation of safe and effective non-embryo culture vaccines was developed on the basis of the influenza VLP produced in various expression systems. This provides great advantages in comparison with existing methods of vaccine production. Such vaccines induced full humoral and cellular immune response in animals and humans. This review is focused on the literature concerning the influenza VLPs obtained in various expression systems including insect, mammalian and plant cells.

[New cold-adapted donor strains for live influenza vaccine]

Cold-adapted (CA) strains A/Krasnodar/35 and B/Victoria/63 were isolated using passages of A/Krasnodar/101/59 and B/Victoria/2/87 wild type strains at low temperatures. The resulting CA strains possessed TS and CA phenotypes and had a reduced ability to reproduce in mouse lungs and nasal turbinates. They displayed a high protective efficacy in experiments on mice. The two CA strains reproduced well in chick embryos and MDCK cell line without change of TS and CA markers. The CA A/Krasnodar/35 strain during passages at low temperature acquired 13 mutations in the 6 internal genes, 8 of those mutations led to amino acid changes. The CA B/Victoria/63 strain acquired 8 mutations in the internal genes, 6 of which led to amino acid changes. The intranasal vaccination of mice with the CA A/Krasnodar/35 strain led to a transitory suppression of various lymphocyte subpopulations, as well as to an increase in the number of some other cell types. The CA strains in question may be used in the future as attenuation donors for live influenza vaccines.

Immunity against heterosubtypic influenza virus induced by adenovirus and MVA expressing nucleoprotein and matrix protein-1

Alternate prime/boost vaccination regimens employing recombinant replication-deficient adenovirus or MVA, expressing Influenza A virus nucleoprotein and matrix protein 1, induced antigen-specific T cell responses in intradermally (ID) vaccinated mice; with the strongest responses resulting from Ad/MVA immunization. In BALB/C mice the immunodominant response was shifted from the previously identified immunodominant epitope to a novel epitope when the antigen was derived from A/Panama/2007/1999 rather than A/PR/8. Alternate immunization routes did not affect the magnitude of antigen-specific systemic IFN-γ response, but higher CD8(+) T-cell IFN-γ immune responses were seen in the bronchoalveolar lavage following intransal (IN) boosting after intramuscular (IM) priming, whilst higher splenic antigen-specific CD8(+) T cell IFN-γ was seen following IM boosting. Partial protection against heterologous influenza virus challenge was achieved following either IM/IM or IM/IN but not ID/ID immunization. These data may be of relevance for the design of optimal immunization regimens for human influenza vaccines, especially for influenza-naïve infants.

[Technological approaches to development of whole-virion inactivated vaccine from recombinant strain against A/H5N1 influenza in the Republic of Kazakhstan]

AIM

Development of technological stages of preparation of experimental influenza whole-virion inactivated adsorbed vaccine based on recombinant influenza virus strains NIBRG-14 and A/Astana/RG/6:2/2009.

MATERIALS AND METHODS

2 recombinant vaccines influenza strains were used in the study--NIBRG-14 and A/Astana/RG/6:2/2009. Purification of native virus-containing allantoic fluid was performed by ion-exchange chromatography. The virus was inactivated by formaldehyde. Merthiolate at concentration of 0.1 mg/ml was added to the vaccine as a preserving substance. Aluminium hydroxide was used as an adjuvant. Harmlessness and immunogenicity (HI) of the constructed preparation are determining.

RESULTS

Virus-containing materials from recombinant strains with biological activity of 8.5 - 9.0 lg EID50/cm3 and hemagglutination activity of 1:256 - 1:1024 in chicken embryos were obtained. Optimal inactivation regimen of non-purified suspensions by formaldehyde was established and combined scheme of purification and concentration of influenza virus was selected that provide harmlessness and immunogenicity of experimental samples of inactivated vaccines against highly pathogenic influenza A/H5N1 in experiments in mice.

CONCLUSION

The data obtained on quality parameters of intermediate products and final vaccine give evidence on their compliance with normative parameters for whole-virion influenza purified vaccine.

A prospective observational safety study on MF59(®) adjuvanted cell culture-derived vaccine, Celtura(®) during the A/H1N1 (2009) influenza pandemic

BACKGROUND

The present study was a prospective observational study to evaluate the safety profile of Celtura(®), a monovalent, cell culture-derived, inactivated subunit influenza vaccine prepared from A/California/07/2009(H1N1) with the adjuvant MF59(®). Subjects were enrolled prospectively during the H1N1 2009 influenza pandemic at medical centres in Colombia, Chile, Switzerland, and Germany during the period December 2009 to June 2010.

METHODS

Subjects ages 18 and older were followed for the occurrence of adverse events (AEs) for six months after vaccination. Adverse events of special interest (AESIs) were neuritis, convulsion (seizure), anaphylaxis, encephalitis, vasculitis, Guillain-Barre syndrome, demyelinating conditions, Bell's palsy, and laboratory-confirmed vaccination failure.

RESULTS

Overall, 7348 AEs were reported in 2296 of 3989 enrolled subjects (57.6%). Only two AEs were considered related to injection site reactions. No laboratory-confirmed cases of influenza were reported. There were 108 medically confirmed serious adverse events (SAEs) reported among 73 subjects with 6 such SAEs described as possibly or probably related to vaccination. Three fatal cases were reported and assessed as not related to vaccination. Two AESIs classified as convulsion were reported and assessed as not related to vaccination. Both AESIs occurred well outside the pre-specified 7 day risk window representing the likely timeframe of the occurrence of seizure following vaccination.

CONCLUSIONS

The results of this study support the overall good safety profile of MF59 adjuvanted cell culture-derived influenza vaccine as administered in adults during the 2009-2010 H1N1 influenza pandemic. No concern is raised regarding the occurrence of AESIs.

A randomised, single-blind, dose-range study to assess the immunogenicity and safety of a cell-culture-derived A/H1N1 influenza vaccine in adult and elderly populations

BACKGROUND

Modern cell-culture production techniques and the use of adjuvants helps to ensure that the global demand for pandemic influenza vaccine can be met. This study aimed to assess the immunogenicty and safety profiles of various cell-culture-derived A/H1N1 pandemic vaccine formulations in healthy adult and elderly subjects.

METHODS

Adult (18-60 years) subjects (n=544) received vaccine either containing 3.75 μg of antigen with half the standard dose of MF59 (Novartis Vaccines and Diagnostics) adjuvant, 7.5 μg antigen with a full dose of MF59, or a non-adjuvanted vaccine containing 15 μg of antigen. Elderly (≥ 61 years) subjects (n=268) received either the 3.75 μg or 7.5 μg adjuvanted formulations. Two priming vaccine doses were administered 3 weeks apart, followed by a single booster dose of seasonal influenza vaccine 1 year later. Immunogenicity was assessed 3 weeks after each vaccination. The safety profile of each formulation was evaluated throughout the study.

RESULTS

A single primary dose of each A/H1N1 vaccine formulation was sufficient to meet all three European (CHMP) licensure criteria for pandemic influenza vaccines in adult subjects. Two licensure criteria were met after one vaccine dose in elderly subjects; two primary doses were required to meet all three criteria in this age group. The highest antibody titres were observed in response to the 7.5 μg vaccine containing a full dose of MF59 adjuvant. All subjects rapidly generated seroprotective antibody titres in response to booster vaccination.

CONCLUSION

This study identified one 3.75 μg vaccine dose containing half the standard dose of MF59 adjuvant as optimal for adults, two doses were optimal for elderly subjects. The antigen-sparing properties of MF59, and rapid, modern, cell-culture production techniques represent significant steps towards meeting the global demand for influenza vaccine.

[Progress in new vaccine strategies against influenza: a review]

Influenza, caused by influenza virus, is a serious respiratory illness which poses a global public health threat. Vaccination is the primary strategy for the prevention and control of influenza. Although both inactivated vaccines and the live attenuated vaccines are effective in preventing influenza, the current vaccines have poor efficacy in the elderly and fail to provide protection against heterosubtype viruses. Development of a safer and more effective influenza vaccine that provides broad cross protection, overcoming the intrinsic limitation of the current vaccines, has been a scientific challenge. During the past decades, structural biology, reverse genetic and other virological technologies developed quickly and sped the progress of influenza vaccinology. Some new strategies for developing influenza vaccine have been generated, produced encouraging results, which showed great prospect as next-generation of influenza vaccines.

Clinical development of a Vero cell culture-derived seasonal influenza vaccine

BACKGROUND

Cell culture technologies have the potential to improve the robustness and flexibility of influenza vaccine supply and to substantially shorten manufacturing timelines. We investigated the safety, immunogenicity and efficacy of a Vero cell culture-derived seasonal influenza vaccine and utilized these studies to establish a serological correlate of vaccine protection.

METHODS

Two multicenter, randomized, double-blind phase III trials were undertaken in the US during the 2008-2009 Northern hemisphere influenza season, in young (18-49 years) and older (50-64 years and ≥ 65 years) adult subjects. 7250 young adults were randomized 1:1 to receive either Vero-derived vaccine or placebo. 3210 older adult subjects were randomized 8:1 to receive either Vero-derived vaccine or a licensed egg-derived vaccine. Serum hemagglutination inhibition antibody titers were assessed 21 days post-vaccination. Vaccine efficacy in preventing cell culture-confirmed influenza infection was determined for the young adult population. Local and systemic adverse events were recorded in both studies.

RESULTS

The Vero-derived vaccine was safe and well tolerated in both young and older adults. All US and European immunological licensing thresholds were comfortably met in both populations. Vaccine efficacy in young adults was 79% against A/H1N1 viruses antigenically matching the corresponding vaccine strain and 78.5% for all antigenically matched influenza viruses. A hemagglutination inhibition antibody titer of ≥ 1:15 provided a reliable correlate of protection for the Vero-derived influenza vaccine, with no additional benefit at titers >1:30. Bridging of the correlate of protection established in the young adult population to the older adult immunogenicity data demonstrated the likely effectiveness of the Vero-derived vaccine in the older adult population.

CONCLUSIONS

A Vero cell culture-derived seasonal influenza vaccine is safe, immunogenic and protects against infection with influenza virus. The novel vaccine technology has the potential to make a substantial contribution to improving influenza vaccine supply.

CLINICAL TRIAL REGISTRATION

The studies are registered with ClinicalTrials.gov, numbers NCT00566345 and NCT00782431.

Adaptation of high-growth influenza H5N1 vaccine virus in Vero cells: implications for pandemic preparedness

Current egg-based influenza vaccine production technology can't promptly meet the global demand during an influenza pandemic as shown in the 2009 H1N1 pandemic. Moreover, its manufacturing capacity would be vulnerable during pandemics caused by highly pathogenic avian influenza viruses. Therefore, vaccine production using mammalian cell technology is becoming attractive. Current influenza H5N1 vaccine strain (NIBRG-14), a reassortant virus between A/Vietnam/1194/2004 (H5N1) virus and egg-adapted high-growth A/PR/8/1934 virus, could grow efficiently in eggs and MDCK cells but not Vero cells which is the most popular cell line for manufacturing human vaccines. After serial passages and plaque purifications of the NIBRG-14 vaccine virus in Vero cells, one high-growth virus strain (Vero-15) was generated and can grow over 10⁸ TCID₅₀/ml. In conclusion, one high-growth H5N1 vaccine virus was generated in Vero cells, which can be used to manufacture influenza H5N1 vaccines and prepare reassortant vaccine viruses for other influenza A subtypes.

Characterization of a fully human monoclonal antibody against extracellular domain of matrix protein 2 of influenza A virus

The extra-cellular domain of the influenza virus matrix protein 2 (M2e) is highly conserved between influenza A virus strains compared to hemagglutinin and neuraminidase, and has long been viewed as a potential and universal vaccine target. M2e induces no or only weak and transient immune responses following infection, making it difficult to detect M2e-specific antibodies producing B-cells in human peripheral blood lymphocytes. Recently, using a single-cell manipulation method, immunospot array assay on a chip (ISAAC), we obtained an M2e-specific human antibody (Ab1-10) from the peripheral blood of a healthy volunteer. In this report, we have demonstrate that Ab1-10 reacted not only to seasonal influenza A viruses, but also to pandemic (H1N1) 2009 virus (2009 H1N1) and highly pathogenic avian influenza A virus, and that the antibody-bound M2e of 2009 H1N1 inactivated the virus with high affinity (∼10(-10)M). More importantly, it inhibited 2009 H1N1 viral propagation in vitro. These results suggest that Ab1-10 might be a potential candidate for antibody therapeutics for a wide range of influenza A viruses.

Gene constellation of influenza A virus reassortants with high growth phenotype prepared as seed candidates for vaccine production

Background

Influenza A virus vaccines undergo yearly reformulations due to the antigenic variability of the virus caused by antigenic drift and shift. It is critical to the vaccine manufacturing process to obtain influenza A seed virus that is antigenically identical to circulating wild type (wt) virus and grows to high titers in embryonated chicken eggs. Inactivated influenza A seasonal vaccines are generated by classical reassortment. The classical method takes advantage of the ability of the influenza virus to reassort based on the segmented nature of its genome. In ovo co-inoculation of a high growth or yield (hy) donor virus and a low yield wt virus with antibody selection against the donor surface antigens results in progeny viruses that grow to high titers in ovo with wt origin hemagglutinin (HA) and neuraminidase (NA) glycoproteins. In this report we determined the parental origin of the remaining six genes encoding the internal proteins that contribute to the hy phenotype in ovo.

Methodology

The genetic analysis was conducted using reverse transcription-polymerase chain reaction (RT-PCR) and restriction fragment length polymorphism (RFLP). The characterization was conducted to determine the parental origin of the gene segments (hy donor virus or wt virus), gene segment ratios and constellations. Fold increase in growth of reassortant viruses compared to respective parent wt viruses was determined by hemagglutination assay titers.

Significance

In this study fifty-seven influenza A vaccine candidate reassortants were analyzed for the presence or absence of correlations between specific gene segment ratios, gene constellations and hy reassortant phenotype. We found two gene ratios, 6∶2 and 5∶3, to be the most prevalent among the hy reassortants analyzed, although other gene ratios also conferred hy in certain reassortants.

[Adherent and single-cell suspension culture of Madin-Darby canine kidney cells in serum-free medium]

In recent years, there are tremendous economic and social losses across the world because of virus-related diseases. It is well known that Madin-Darby canine kidney (MDCK) cells are easily handled, quickly amplified and efficiently infected with influenza virus. Therefore, they are considered as one of the most important cell lines for the production of influenza vaccine. In this work, we first developed a serum-free adherent culture process for MDCK cells with an in-house prepared serum-free medium MDCK-SFM. Next, we derived a cell line named ssf-MDCK, which was amenable for single-cell suspension culture in the serum-free medium. We found that during serum-free batch culture of MDCK cells, the peak viable cell density and maximum specific growth rate were 3.81 x 10(6) cells/mL and 0.056 h(-1), respectively; 3.6- and 1.6-fold increase compared with those in serum-containing adherent batch culture. In addition, we compared growth and metabolic characteristics of MDCK cells in serum-containing adherent culture, serum-free adherent culture and serum-free single-cell suspension culture. We found that less metabolic by-products were produced in both serum-free cultures. In serum-free single-cell suspension batch culture, the viable cell density was highest. These results are critical for establishing large-scale suspension culture of MDCK cells as subsequent well as large-scale influenza vaccine production.

Validation of the safety of MDCK cells as a substrate for the production of a cell-derived influenza vaccine

Cell culture-based production methods may assist in meeting increasing demand for seasonal influenza vaccines and developing production flexibility required for addressing influenza pandemics. MDCK-33016PF cells are used in propagation of a cell-based seasonal influenza vaccine (Optaflu^®); but, like most continuous cell lines, can grow in immunocompromised mice to produce tumors. It is, therefore, essential that no residual cells remain within the vaccine, that cell lysates or DNA are not oncogenic, and that the cell substrate does not contain oncogenic viruses or oncogenic DNA. Multiple, redundant processes ensure the safety of influenza vaccines produced in MDCK-33016PF cells. The probability of a residual cell being present in a dose of vaccine is approximately 1 in 10³⁴. Residual MDCK-DNA is ≤10 ng per dose and the ß-propiolactone used to inactivate influenza virus results in reduction of detectable DNA to less than 200 base pairs (bp). Degenerate PCR and specific PCR confirm exclusion of oncogenic viruses. The manufacturing process has been validated for its capacity to remove and inactivate viruses. We conclude that the theoretical risks arising from manufacturing seasonal influenza vaccine using MDCK-33016PF cells are reduced to levels that are effectively zero by the multiple, orthogonal processes used during production.

[Development of new nutrient medium for MDCK and Vero cells based on soy hydrolysate obtained using bromeline and assessment of growth characteristics of influenza virus vaccine strains cultivated on them]

AIM

To develop nutrient medium for MDCK and Vero cells based on soy hydrolysate obtained using bromeline and to assess of growth characteristics of influenza virus vaccine strains cultivated on them.

MATERIALS AND METHODS

Physico-chemical characteristics of hydrolysate were assessed according to FS 42-3874-99. Growth characteristics of nutrient medium based on soy hydrolysate and vaccine strains of influenza virus A/Solomon Islands/03/06 (H1N1), A/Wisconsin/67/2005 (H3N2) and B/Malaysia/2506/2004 were studied on MDCK and Vero cells.

RESULTS

MDCK and Vero cells grew well on medium based on soy hydrolysate obtained using bromeline with decreased (to 2% and 3% respectively) content of fetal calf serum and allowed effective production of vaccine strains of influenza virus.

CONCLUSION

Technology for producing of nutrient medium based on hydrolysate of soy flour obtained using bromeline was developed. This medium could successively used for cultivation of continued cell cultures MDCK and Vero used as substrate for tissue culture-based vaccines against influenza.

The Avian EB66(R) Cell Line, Application to Vaccines, and Therapeutic Protein Production

Embryonated chicken eggs and primary chicken embryo fibroblasts (CEFs) have been used for decades as a means of manufacturing human and veterinary vaccines. However, these egg and CEF-based production systems are associated with many serious limitations in terms of their regulatory acceptability, production capacity, and supply chain risks. The development of a safer, cheaper, and more efficient cell substrate for vaccine production would represent a significant business advantage for vaccine manufacturers. Building on the exceptional properties of avian embryonic stem cells, Vivalis has created a new cell substrate, the Duck EB66® cell line. This article describes how this cell substrate was derived, the manufacture and qualification of a master cell bank, and the evaluation of the cell substrate for the manufacture of vaccines and human therapeutic proteins.

MDCK and Vero cells for influenza virus vaccine production: a one-to-one comparison up to lab-scale bioreactor cultivation

Over the last decade, adherent MDCK (Madin Darby canine kidney) and Vero cells have attracted considerable attention for production of cell culture-derived influenza vaccines. While numerous publications deal with the design and the optimization of corresponding upstream processes, one-to-one comparisons of these cell lines under comparable cultivation conditions have largely been neglected. Therefore, a direct comparison of influenza virus production with adherent MDCK and Vero cells in T-flasks, roller bottles, and lab-scale bioreactors was performed in this study. First, virus seeds had to be adapted to Vero cells by multiple passages. Glycan analysis of the hemagglutinin (HA) protein showed that for influenza A/PR/8/34 H1N1, three passages were sufficient to achieve a stable new N-glycan fingerprint, higher yields, and a faster increase to maximum HA titers. Compared to MDCK cells, virus production in serum-free medium with Vero cells was highly sensitive to trypsin concentration. Virus stability at 37 degrees C for different virus strains showed differences depending on medium, virus strain, and cell line. After careful adjustment of corresponding parameters, comparable productivity was obtained with both host cell lines in small-scale cultivation systems. However, using these cultivation conditions in lab-scale bioreactors (stirred tank, wave bioreactor) resulted in lower productivities for Vero cells.

Vaccine Manufacturing--Second Annual visiongain Conference

The Vaccine Manufacturing--Second Annual visiongain Conference, held in London, included topics covering new technological developments in the field of influenza vaccine research. This conference report highlights selected presentations on influenza vaccine development in mammalian, insect and avian embryonic cells, regulatory considerations for cell culture-based influenza vaccine production, an improved animal model for influenza infection, and considerations for designing vaccine manufacturing facilities. Investigational drugs discussed include FluBiovax (Immunobiology Ltd) and FluBlok (Protein Sciences Corp/UMN Pharma Inc).

Comparison of egg and high yielding MDCK cell-derived live attenuated influenza virus for commercial production of trivalent influenza vaccine: in vitro cell susceptibility and influenza virus replication kinetics in permissive and semi-permissive cells

Currently MedImmune manufactures cold-adapted (ca) live, attenuated influenza vaccine (LAIV) from specific-pathogen free (SPF) chicken eggs. Difficulties in production scale-up and potential exposure of chicken flocks to avian influenza viruses especially in the event of a pandemic influenza outbreak have prompted evaluation and development of alternative non-egg based influenza vaccine manufacturing technologies. As part of MedImmune's effort to develop the live attenuated influenza vaccine (LAIV) using cell culture production technologies we have investigated the use of high yielding, cloned MDCK cells as a substrate for vaccine production by assessing host range and virus replication of influenza virus produced from both SPF egg and MDCK cell production technologies. In addition to cloned MDCK cells the indicator cell lines used to evaluate the impact of producing LAIV in cells on host range and replication included two human cell lines: human lung carcinoma (A549) cells and human muco-epidermoid bronchiolar carcinoma (NCI H292) cells. The influenza viruses used to infect the indicators cell lines represented both the egg and cell culture manufacturing processes and included virus strains that composed the 2006–2007 influenza seasonal trivalent vaccine (A/New Caledonia/20/99 (H1N1), A/Wisconsin/67/05 (H3N2) and B/Malaysia/2506/04). Results from this study demonstrate remarkable similarity between influenza viruses representing the current commercial egg produced and developmental MDCK cell produced vaccine production platforms. MedImmune's high yielding cloned MDCK cells used for the cell culture based vaccine production were highly permissive to both egg and cell produced ca attenuated influenza viruses. Both the A549 and NCI H292 cells regardless of production system were less permissive to influenza A and B viruses than the MDCK cells. Irrespective of the indicator cell line used the replication properties were similar between egg and the cell produced influenza viruses. Based on these study results we conclude that the MDCK cell produced and egg produced vaccine strains are highly comparable.

[Safety of cell culture-based influenza vaccines]

After more than 60 years, the conventional production of influenza vaccines employing fertilized chicken eggs has reached its limits - both in terms of temporal flexibility and vaccine production volume. This situation is compounded by the fact that the present pandemic-driven situation has roughly doubled the overall vaccine demand virtually "overnight". Modem cell culture technology has significant advantages over the conventional method of manufacturing influenza vaccines employing embryonated chicken eggs, and enables manufacturers to respond rapidly to the exploding worldwide seasonal and pandemic-driven need for influenza vaccines. Recent articles in the popular press claiming that cell culture-based influenza vaccines can cause tumours raised uncertainty among physicians and the general population, and also discredit officially accepted assessments and product licensing by the relevant authorities. The present article provides an overview on the cell culture technology and on the safety profile of the cells and of the vaccine product.

[Selected problems of manufacturing influenza vaccines]

In the study chosen issues of manufacturing influenza vaccines running to increase effectiveness were performed. New concepts into development of process of safety and efficacy influenza vaccines are connected with use a new adjuvants, use of alternative routes of administration of vaccine, new structural virus subunits including DNA, new way of virus culture and use of live, attenuated vaccines.

[Cowpea mosaic virus chimeric particles bearing ectodomain of matrix protein 2 (M2E) of influenza A virus: production and characteristics]

The epitope presentation system for ectodomain of M2-protein of influenza A virus (M2e) based on Cowpea Mosaic Virus (CPMV) was constructed for expression in plants Vigna unguiculata. CPMV is widely used as a vector for production of immunogenic chimeric virus particles (CVPs) bearing epitopes of different infectious human and animal pathogens. To produce chimeric CPMV virus particles in plants, two binary vectors were constructed bearing modified gene coding for S-coat protein of CPMV with insertions of M2e epitopes of human influenza and bird influenza viruses. Antigenic and immunogenic properties of CVPs obtained were investigated in mice immunization experiments and it was shown that they can induce anti-M2e IgG production and partial protection mice against challenge with low doses of flu virus. However, low infectivity and immunogenicity of CPMV chimeric particles indicate the need for further optimization of plant virus-based systems for M2e-epitopes presentation to use plants as a possible source of flu vaccines.

Plant-expressed HA as a seasonal influenza vaccine candidate

Influenza is a globally important respiratory pathogen that causes a high degree of morbidity and mortality annually. Although current vaccines are effective against virus infection, new strategies need to be developed to satisfy the global demand for an influenza vaccine. To address this point, we have engineered and produced the full-length hemagglutinin (HA) protein from the A/Wyoming/03/03 (H3N2) strain of influenza in plants. The antigenicity of this plant-produced HA was confirmed by ELISA and single-radial immunodiffusion (SRID) assays. Immunization of mice with plant-produced HA resulted in HA-specific humoral (IgG1, IgG2a and IgG2b) and cellular (IFNgamma and IL-5) immune responses. In addition, significant serum hemagglutination inhibition (HI) and virus neutralizing (VN) antibody titers were obtained with an antigen dose as low as 5mug. These results demonstrate that plant-produced HA protein is antigenic and can induce immune responses in mice that correlate with protection.