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How to Make a Swine Flu Vaccine
As of May 7, 22 countries had reported 1516 cases of swine flu, according to the World Health Organization, and multiple companies and governments are working to make vaccines available to the population. Pharmaceutical Technology spoke with Rangappa Ramachandra, program director and lead scientist of immunology services at Covance, about what’s involved in developing and manufacturing a vaccine as the pandemic progresses. A comprehensive drug-development services company, Covance has been providing immunology services such as R&D and preclinical vaccine testing to pharmaceutical and biopharmaceutical companies since 2005.
PharmTech: What is known right now about the prevalent strain of virus? Have many different strains emerged yet, or are vaccine makers working to combat one strain?
Ramachandra: The current flu outbreak in humans is caused by a novel H1N1 flu, commonly known as swine flu. There is one strain and no antigen drift [has been] reported in this virus until now. The US Centers for Disease Control and Prevention (CDC) are currently working to create the reference virus strain and it is [to be made] available to vaccine companies by the end of May for vaccine manufacturing. The new strain is a ressortment of four strains of influenza A virus (a new strain of H1N1). CDC reported that the four components include one strain from humans, one strain from birds, and two strains from swine.
PharmTech: What key risks and challenges are involved?
Ramachandra: After getting the reference virus strain from CDC, vaccine manufacturers [will] follow the technology that is very similar to seasonal and universal flu vaccine development. The pathology of this novel H1N1 virus is unusual in that it targets young individuals and causes severe lung pathology due to over-activation of the immune system and induction of cytokine storm. Key risks and challenges involve demonstrating the safety and efficacy of the vaccine without any pathology in the vaccine recipients.
Other challenges include… making [the vaccines] available to control the pandemic. We will not have enough vaccines to protect the population. In addition, we do not have sufficient vaccine production capacity to make required vaccines to protect everybody. Although antivirals can meet the immediate needs, immunity is the best long-term solution. Currently, vaccines and their manufacturing are attracting increasing investment.
PharmTech: Can you walk us briefly through the types of tests required to develop a pandemic flu vaccine and how the time crunch may affect those tests and their results?
Ramachandra: The complete licensing application or dossier submission should contain administrative data, quality data, preclinical testing and clinical-trial data in accordance with FDA-CBER regulations and the European Directive. The first and foremost step in vaccine development is availability of the reference seed virus to manufacturers. Using current and novel technologies, manufacturers start growing the virus in bulk…. Once the bulk virus is available, the following steps occur:
Quality control: The final drug substance and drug product should be sterile and [include] bulk-containing purified virus surface antigens. The final product should contain only haemaglutinin (HA) and neuraminidase (NA) antigens. A detailed manufacturing process and process control should contain: virus propagation, virus purification and antigen preparation, specification and characterization, batch analysis, bulk- and storage-vessel conditions. Once the drug product preparation is completed, both drug product and finished fill product should be tested for stability.
Preclinical testing: The inactivated (killed) purified product, with or without adjuvant, should undergo preclinical testing designed to demonstrate the immunogenicity in mice, rabbits, and ferrets. The efficacy of the vaccine should be demonstrated in a ferret model by challenge exposure. In addition, the vaccine will need to be tested for lack of abnormal immunotoxicity in mouse and guinea pig models. For all adjuvanted or nonadjuvanted vaccines, lack of local or systemic toxicity should be demonstrated in rabbits. Because this virus is known to cause severe lung pathology due to stimulation of robust immune response and cytokine storm, it therefore may be required to show a lack of systemic toxicity in vaccinated animals.
These are the minimum preclinical vaccine testing requirements for initiating a Phase I clinical trial. They should be thoroughly planned and executed timely to complete all the preclinical studies. There is no fast track during the preclinical vaccine testing stage (particularly for safety and immunogenicity). Instead, to save time, the above studies need to start simultaneously. This takes proper planning of resources, facilities, technical personal, and contingency planning. And finally, FDA’s CBER will then need to review any IND application under its fast-track guidelines to avoid delay in licensing or releasing the vaccine for public use.
PharmTech: In the case of this flu, what type of immune response is optimal?
Ramachandra: In general in viral infections, to induce complete protection, we need both humoral (HI) and cell-mediated immune (CMI) responses. A majority of the nonadjuvanted vaccines have a suboptimal efficacy profile, and tend to induce only humoral antibody response against influenza strain, with very low or no cytotoxic T-cell response. Therefore, use of novel adjuvants that induce both B-cell and T-cell in the vaccine formulation is critical to HI and CMI responses for complete protection. The efficacious vaccine should induce sterilization and long-lasting immunity.
PharmTech: Are there any particular technologies or techniques that enable the rapid development of a vaccine? Is the vaccine developed in eggs, or cells? Is it a live attenuated vaccine or a killed vaccine? A recombinant vaccine?
Ramachandra: Creation of a live attenuated virus is a time-consuming and laborious procedure. Qualification of such live vaccine reference strains per regulatory guidelines takes a long time (1 to 2 years). Therefore, the vaccine should contain a killed (inactivated) virus (either propagated in eggs or cells) or a recombinant vaccine…. [Because] there are several biotechnology companies actively involved in the development of universal vaccines using recombinant technology, [that] technology may play a major role in the development of efficacious vaccine for this new flu virus H1N1.
PharmTech: Some reports say we may have a swine flu vaccine in six weeks. What is your best estimate regarding the timetable for a vaccine?
Ramachandra: Here we are not talking about a small batch of vaccine; we need millions of doses for the national stockpile to protect the human population. Six weeks is an unrealistic number. In my best estimate, it takes about 8 to 10 months, if vaccine R&D, manufacturing, and final batch release is done as planned.
PharmTech: Once a vaccine is produced, how can we be sure of its safety and effectiveness? Looking ahead, how do you create (or attempt to create) a vaccine that covers most of the current strains as well as those likely to arise?
Ramachandra: That is a real risk in the flu vaccine business…. During passage from human to human, this virus may lose virulence, adapt to humans and not cause any disease. On the other hand, during serial passages in humans, the virus may gain more virulence and become highly pathogenic. In either instance, the virus retains its original anatomy; therefore, vaccines produced against the original wild type, novel H1N1, will still work against high and low virulent viruses.
The development of traditional vaccines against flu viruses is always risky due to constant antigen drift and ressortment of the virus in nature. Vaccine candidate antigens, namely haemaglutinin (HA) protein, are highly unstable and prone for drift. The only solution to create a stable universal vaccine is to use highly conserved proteins of the virus such as M2e protein or internal proteins. These proteins are present in low numbers and do not play a major role in viral replication and pathogenesis. One of the weaknesses of the M2e protein is that it is a poor immunogen and does not induce a robust immune response. But its immunogenicity and antigenicity can be increased with novel adjuvants.
Such universal vaccines will be highly effective against most seasonal strains as well as new strains. The beauty of such vaccines is that they can be manufactured any time of the year and vaccine companies need not wait for CDC to release reference vaccine flu strains each year.
PharmTech: What has Covance learned through its experiences thus far when it comes to developing complex vaccines?
Ramachandra: Vaccine development is a complex process and heavily regulated by several agencies because of the nature of its use in healthy populations…. The most important [deliverable] is timely execution of studies…. Vaccine developers are [also] demanding:
PharmTech: In what ways is Covance helping to develop a swine flu vaccine at this time?
Ramachandra: Covance Immunology and Preclinical and Clinical Vaccine testing services are uniquely qualified to design and integrate complex projects with cutting-edge technology, helping to make a quick decision on the success of the project…. Our vaccine testing methodology is based on sound scientific expertise, rapid study start, multispecies experience, state-of-the art facilities, study design development, testing, execution, and reporting, all of which are unique for the success of the project. The Covance niche is its scientists—they have extensive experience in veterinary medicine, vaccinology, immunology, infectious diseases, and immunopathology, in order to deal with complex projects. Our solutions help move one phase of vaccine development to the next to save money and allow instantaneous use of information and technology.
Covance provides operational service and scientific excellence for the execution of studies required for flu vaccine testing, including:
Several vaccine pharmaceutical and biotech companies have approached Covance Immunology Services for vaccine preclinical testing in animal models (mice, rabbits, and ferrets) to evaluate immunogenicity, dose response, safety/immunotoxicity, and potency of the novel H1N1 vaccines.