article

Flu research includes molecular virology, pathogenesis, host immune responses, and epidemiology. These help in developing influenza countermeasures such as vaccines, therapies and diagnostic tools.

The potential H5N1 pandemic has motivated a huge increase in flu research. At least 12 companies and 17 governments are developing pre-pandemic influenza vaccines in 28 different clinical trials that, if successful, could turn a deadly pandemic infection into a nondeadly pandemic infection. A vaccine that could prevent any illness at all from the not-yet-existing pandemic influenza strain will take at least three months from the virus's emergence until full-scale vaccine production could begin; with vaccine production hoped to increase until one billion doses are produced by one year after the virus is first identified. Science and Development Network article Pandemic flu: fighting an enemy that is yet to exist published May 3, 2006.

The US federal government on May 4, 2006 awarded five-year contracts for "more than $1 billion to five drug manufacturers developing technology for speedier mass production of vaccines in the event of a pandemic" from the $3.8 billion pandemic preparedness bill passed in 2005. "The federal government says its goal is to be able to distribute a vaccine to every American within six months of a pandemic. Currently, flu vaccines are produced in specialized chicken eggs, but that technique does not allow for speedy mass vaccinations." The companies receiving the contracts were:

Improved influenza countermeasures require basic research on how viruses enter cells, replicate, mutate, evolve into new strains and induce an immune response.

The Influenza Genome Sequencing Project is creating a library of influenza sequences that will help us understand what makes one strain more lethal than another, what genetic determinants most affect immunogenicity, and how the virus evolves over time.

Solutions to limitations in current vaccine methods are being researched. The US government has purchased from Sanofi Pasteur and Chiron Corporation several million doses of vaccine meant to be use in case of an influenza pandemic from H5N1 and is conducting clinical trials on them. New York Times article ""Doubt Cast on Stockpile of a Vaccine for Bird Flu"" ABC News reported on April 1, 2006 that "Beginning in late 1997, the human trials have tested 30 different vaccines, all pegged to the H5N1 virus." ABC News

A technique called reverse genetics allows scientists to manipulate the genomes of influenza viruses and to transfer genes between viral strains. The technique allows the rapid generation of seed viruses for vaccine candidates that exactly match the anticipated epidemic strain. By removing or modifying certain virulence genes, reverse genetics also can be used to convert highly pathogenic influenza viruses into vaccine candidates that are safer for vaccine manufacturers to handle.

Another technique is use of cell cultures to grow vaccine strains; such as genetically engineering baculovirus to express a gene that encodes an influenza coat protein such as hemagglutinin or neuraminidase. "A recent NIAID-supported Phase II clinical trial of a vaccine produced by Protein Sciences Corporation using this strategy showed that it is well tolerated and immunogenic; the company is conducting further clinical evaluation of this product. Other new pathways for producing influenza vaccines include DNA-based approaches and the development of broadly protective vaccines based on influenza virus proteins that are shared by multiple strains." The NIH Biomedical Research Response to Influenza

"To address the H9N2 threat, NIAID contracted with Chiron Corporation to produce investigational batches of an inactivated vaccine, which will be evaluated clinically by NIAID early next year. For H5N1, Aventis-Pasteur, Inc. and Chiron are both producing investigational lots of inactivated H5N1 vaccine preparations; additionally, DHHS has contracted with Aventis to produce up to 2 million doses to be stockpiled for emergency use, if needed, to vaccinate health workers, researchers, and, if indicated, the public in affected areas. Development and evaluation of a combination antiviral regimen against these potential pandemic influenza strains are also now under way."

AVI Bio Pharma Inc. has evidence of inhibition of multiple subtypes of influenza A virus in cell culture with Morpholino oligomers from the results of their labs and four independent research laboratories. "The key finding here is that our NEUGENE(R) therapeutics continue to show efficacy against all strains of influenza A, including H5N1." AVI BioPharma Reports Successful Inhibition of Multiple Subtypes of Influenza A Using NEUGENE Antisense Therapeutic

"Several companies are focusing on new vehicles for growing antigens, which are the bits of a virus or bacterium needed to spur a person's immune system to fight an infection. VaxInnate, a New Jersey-based biotechnology company, has reported success using E. coli bacteria, which can cause a sometimes-fatal infection but also can be used to grow vaccine ingredients when the harmful part of the bacterium is removed. Dowpharma, a unit of Dow Chemical Co, has been using different bacteria found in soil and water, P. fluorescens, which may make a higher volume of antigens more quickly than E. coli." ABC News article Scientists mull faster vaccine production published on April 12, 2006

Vaccines

A vaccine probably would not be available in the initial stages of population infection CDC. Once a potential virus is identified, it normally takes at least several months before a vaccine becomes widely available, as it must be developed, tested and authorized. The capability to produce vaccines varies widely from country to country; in fact, only 15 countries are listed as "Influenza vaccine manufacturers" according to the World Health Organization WHO. It is estimated that, in a best scenario situation, 750 million doses could be produced each year, whereas it is likely that each individual would need two doses of the vaccine in order to become inmuno-competent. Distribution to and inside countries would probably be problematic phacilitate.co.uk. Several countries, however, have well-developed plans for producing large quantities of vaccine. For example, Canadian health authorities say that they are developing the capacity to produce 32 million doses within four months, enough vaccine to inoculate every person in the country. Canada TV News

There are two serious technical problems associated with the development of a vaccine against H5N1. The first problem is this: seasonal influenza vaccines require a single injection of 15 μg haemagluttinin in order to give protection; H5 seems to evoke only a weak immune response and a large multicentre trial found that two injections of 90 µg H5 given 28 days apart provided protection in only 54% of people . Even if it is considered that 54% is an acceptable level of protection, the world is currently capable of producing only 900 million doses at a strength of 15 μg (assuming that all production were immediately converted to manufacturing H5 vaccine); if two injections of 90 μg are needed then this capacity drops to only 70 million . Trials using adjuvants such as alum or MF59 to try and lower the dose of vaccine are urgently needed. The second problem is this: there are two circulating clades of virus, clade 1 is the virus originally isolated in Vietnam, clade 2 is the virus isolated in Indonesia. Current vaccine research is focussed on clade 1 viruses, but the clade 2 virus is antigenically distinct and a clade 1 vaccine will probably not protect against a pandemic caused by clade 2 virus.

United States

According to the US HHS (United States Department of Health & Human Services) Pandemic Influenza Plan Appendix F: Current HHS Activities last revised on November 8, 2005 US HHS (United States Department of Health & Human Services) Pandemic Influenza Plan Appendix F: Current HHS Activities last revised on November 8, 2005:

Currently, influenza vaccine for the annual, seasonal influenza program comes from four manufacturers. However, only a single manufacturer produces the annual vaccine entirely within the U.S. Thus, if a pandemic occurred and existing U.S.-based influenza vaccine manufacturing capacity was completely diverted to producing a pandemic vaccine, supply would be severely limited. Moreover, because the annual influenza manufacturing process takes place during most of the year, the time and capacity to produce vaccine against potential pandemic viruses for a stockpile, while continuing annual influenza vaccine production, is limited. Since supply will be limited, it is critical for HHS to be able to direct vaccine distribution in accordance with predefined groups (see Appendix D); HHS will ensure the building of capacity and will engage states in a discussion about the purchase and distribution of pandemic influenza vaccine.

Vaccine production capacity: The protective immune response generated by current influenza vaccines is largely based on viral hemagglutinin (HA) and neuraminidase (NA) antigens in the vaccine. As a consequence, the basis of influenza vaccine manufacturing is growing massive quantities of virus in order to have sufficient amounts of these protein antigens to stimulate immune responses. Influenza vaccines used in the United States and around world are manufactured by growing virus in fertilized hens’ eggs, a commercial process that has been in place for decades. To achieve current vaccine production targets millions of 11-day old fertilized eggs must be available every day of production.

In the near term, further expansion of these systems will provide additional capacity for the U.S.-based production of both seasonal and pandemic vaccines, however, the surge capacity that will be needed for a pandemic response cannot be met by egg-based vaccine production alone, as it is impractical to develop a system that depends on hundreds of millions of 11-day old specialized eggs on a standby basis. In addition, because a pandemic could result from an avian influenza strain that is lethal to chickens, it is impossible to ensure that eggs will be available to produce vaccine when needed.

In contrast, cell culture manufacturing technology can be applied to influenza vaccines as they are with most viral vaccines (e.g., polio vaccine, measles-mumps-rubella vaccine, chickenpox vaccine). In this system, viruses are grown in closed systems such as bioreactors containing large numbers of cells in growth media rather than eggs. The surge capacity afforded by cell-based technology is insensitive to seasons and can be adjusted to vaccine demand, as capacity can be increased or decreased by the number of bioreactors or the volume used within a bioreactor. In addition to supporting basic research on cell-based influenza vaccine development, HHS is currently supporting a number of vaccine manufacturers in the advanced development of cell-based influenza vaccines with the goal of developing U.S.-licensed cell-based influenza vaccines produced in the United States.

Dose-sparing technologies. Current U.S.-licensed vaccines stimulate an immune response based on the quantity of HA (hemagglutinin) antigen included in the dose. Methods to stimulate a strong immune response using less HA antigen are being studied in H5N1 and H9N2 vaccine trials. These include changing the mode of delivery from intramuscular to intradermal and the addition of immune-enhancing adjuvant to the vaccine formulation. Additionally, HHS is soliciting contract proposals from manufacturers of vaccines, adjuvants, and medical devices for the development and licensure of influenza vaccines that will provide dose-sparing alternative strategies.

Anti-viral drugs

Many nations, as well as the World Health Organization, are working to stockpile anti-viral drugs in preparation for a possible pandemic. Oseltamivir (trade name Tamiflu) is the most commonly sought drug, since it is available in pill form. Zanamivir (trade name Relenza) is also considered for use, but it must be inhaled. Other anti-viral drugs are less likely to be effective against pandemic influenza.

Both Tamiflu and Relenza are in short supply, and production capabilities are limited in the medium term. Some doctors say that co-administration of Tamiflu with probenecid could double supplies Nature.

There also is the potential of viruses to evolve drug resistance. Some H5N1-infected persons treated with oseltamivir have developed resistant strains of that virus.

H5N1 vaccine

There are several H5N1 vaccines for several of the avian H5N1 varieties. H5N1 continually mutates rendering them, so far for humans, of little use. While there can be some cross-protection against related flu strains, the best protection would be from a vaccine specifically produced for any future pandemic flu virus strain. Dr. Daniel Lucey, co-director of the Biohazardous Threats and Emerging Diseases graduate program at Georgetown University has made this point, "There is no H5N1 pandemic so there can be no pandemic vaccine." However, "pre-pandemic vaccines" have been created; are being refined and tested; and do have some promise both in furthering research and preparedness for the next pandemic. Vaccine manufacturing companies are being encouraged to increase capacity so that if a pandemic vaccine is needed, facilities will be available for rapid production of large amounts of a vaccine specific to a new pandemic strain.

Problems with H5N1 vaccine production include:

  • lack of overall production capacity
  • lack of surge production capacity (it is impractical to develop a system that depends on hundreds of millions of 11-day old specialized eggs on a standby basis)
  • the pandemic H5N1 might be lethal to chickens

Cell culture (cell-based) manufacturing technology can be applied to influenza vaccines as they are with most viral vaccines and thereby solve the problems associated with creating flu vaccines using chicken eggs as is currently done. Researchers at the University of Pittsburgh have had success with a genetically engineered vaccine that took only a month to make and completely protected chickens from the highly pathogenic H5N1 virus. Wired News JVI

According to the United States Department of Health & Human Services:

In addition to supporting basic research on cell-based influenza vaccine development, HHS is currently supporting a number of vaccine manufacturers in the advanced development of cell-based influenza vaccines with the goal of developing U.S.-licensed cell-based influenza vaccines produced in the United States. Dose-sparing technologies. Current U.S.-licensed vaccines stimulate an immune response based on the quantity of HA (hemagglutinin) antigen included in the dose. Methods to stimulate a strong immune response using less HA antigen are being studied in H5N1 and H9N2 vaccine trials. These include changing the mode of delivery from intramuscular to intradermal and the addition of immune-enhancing adjuvant to the vaccine formulation. Additionally, HHS is soliciting contract proposals from manufacturers of vaccines, adjuvants, and medical devices for the development and licensure of influenza vaccines that will provide dose-sparing alternative strategies. Department of Health & Human Services

Chiron Corporation is now recertified and under contract with the National Institutes of Health to produce 8,000-10,000 investigational doses of Avian Flu (H5N1) vaccine. Aventis Pasteur is under similar contract. The United States government hopes to obtain enough vaccine in 2006 to treat 4 million people. However, it is unclear whether this vaccine would be effective against a hypothetical mutated strain that would be easily transmitted through human populations, and the shelflife of stockpiled doses has yet to be determined. [http://www.npr.org/templates/story/story.php?storyId=5133306 NPR

The New England Journal of Medicine reported on March 30, 2006 on one of dozens of vaccine studies currently being conducted. The Treanor et al. study was on vaccine produced from the human isolate (A/Vietnam/1203/2004 H5N1) of a virulent clade 1 influenza A (H5N1) virus with the use of a plasmid rescue system, with only the hemagglutinin and neuraminidase genes expressed and administered without adjuvant. "The rest of the genes were derived from an avirulent egg-adapted influenza A/PR/8/34 strain. The hemagglutinin gene was further modified to replace six basic amino acids associated with high pathogenicity in birds at the cleavage site between hemagglutinin 1 and hemagglutinin 2. Immunogenicity was assessed by microneutralization and hemagglutination-inhibition assays with the use of the vaccine virus, although a subgroup of samples were tested with the use of the wild-type influenza A/Vietnam/1203/2004 (H5N1) virus." The results of this study combined with others scheduled to be completed by Spring 2007 is hoped will provide a highly immunogenic vaccine that is cross-protective against heterologous influenza strains. New England Journal of MedicineVolume 354:1411-1413 - March 30, 2006 - Number 13 - Vaccines against Avian Influenza — A Race against Time

See also

Influenza | Research

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Flu research".

Home Page • arts • business • computers • games • health • hospitals • home • kids & teens • news • physicians • recreation• reference • regional • science • shopping • society • sports • world