Overview

Cell culture-derived influenza vaccine technology (“flu cell culture”) is an innovative production process for the manufacturing of flu vaccine on the basis of cell cultures. Cell culture–derived influenza vaccines (commonly referred to as "flu cell culture" vaccines) use cell cultures rather than chicken eggs for antigen production. Current egg-derived vaccines production requires up to nine months, and this lead time can hinder the response to unanticipated demands such as the discovery of pandemic strains, production failures and seasonal influenza virus strain changes. In contrast, flu cell culture production enables flexible, faster start-up of vaccine manufacturing, providing a particularly important advantage in the event of an influenza pandemic.

Potential Advantages

This next-generation technology offers a number of potential advantages over traditional, egg-based vaccine manufacturing. The most important of these are:

• It is faster. Long lead times of traditional egg-based flu vaccine production are eliminated. Under egg-based manufacturing, the specially certified eggs for the annual flu vaccine have to be ordered with a lead time of up to one year. In contrast, the cells for flu vaccine production based on cell culture are always available.
• It is more flexible. The required amount of cells is determined at the start of production. In a few days to weeks, the required cell amount can be bred from a small quantity of deep frozen MDCK-cells (the seed cells) for flu vaccine production. This could offer a distinct advantage, particularly in the event of a pandemic, when large quantities of vaccine need to be produced quickly.
• It is independent of eggs. No chicken = no egg = no vaccine; this is the simple equation for the traditional egg-based production. Highly poultry-pathogenic (i.e. dangerous to poultry) viral strains can cause delays in the start of production of a vaccine in the event of a pandemic. In addition, the MDCK-cell is specifically characterized for each phase of its utilization. Therefore, the same proliferation system is always available for the viruses. In contrast, chicken eggs are “individualists“– their properties vary within natural limits. This also has an impact on the manufacturing process. In addition, production based on cell cultures is performed in a contained system, in contrast to egg-based manufacturing.

Five Steps Production Process:

1. Cell Proliferation
   The basis for the new cell culture technology is the so-called MDCK-cell line, which originated in 1958 from the kidney of a healthy dog. This MDCK-cell line was optimized for the production of flu vaccine and tested with numerous virus variants. It has proven to be particularly suitable for the production of flu vaccines. And it grows in suspension, and thus requires no surface to proliferate; this factor considerably simplifies industrial production.

   The cells are stored in liquid nitrogen at –196 °C. For the production, minimum amounts – a so-called cryo-tube contains 1 ml with approximately 10 million cells – are thawed and proliferated in three steps from a 10-liter-volume to 100 liters and then to 1,000 liters: At each stage the cells receive the optimal environment for their growth, with respect to temperature, the pH value and the nutrient solution. The proliferation of the cells in fermenters (stainless steel tanks) is constantly monitored with the aid of a computer system that automatically checks all data and accurately records each step. Cell proliferation takes place in a contained fermenter system in so-called clean rooms, resulting in maximum safety and purity for employees, environment and product. Approximately three weeks after the removal of the cells from the nitrogen refrigeration, sufficient cells have grown in the 1,000-liter fermenter. Now virus proliferation can begin.

2. Virus Proliferation
   The cells are then transferred to a 2,500-liter fermenter via a closed pipe system. Again the production employees add new nutrients. In the next step, the Influenza virus is placed in the tank. It takes several days to multiply in the cells. During the course of this process, the cells die off and viruses are released in the medium.

3. Purification
   The first step of a long series of purification procedures is so-called separation, by which the virus solution is separated from the cell residue. In a powerful chromatography column, the virus is then separated from the medium solution, and the volume is reduced ten times. Chromatography is a chemical process to separate a mixture of materials into individual parts. The next step, ultra-filtration, concentrates the now 250 liters further – by a factor 10 to approximately 25 liters.

4. Inactivation and Splitting
   The virus is inactivated via a chemical process. Virus splitting follows, because only fractions of specific surface proteins are required for the subsequent flu vaccine. After further purification and concentration steps, approximately 10 liters of antigen concentrate of a virus strain are left of the original 2,500 liters. Since the seasonal flu vaccines contain three viral strains, the production process must be performed three times - once for every strain. Thus, from the 3 x 2,500 liters, approx. 450,000 vaccine doses of a seasonal flu vaccine are generated).

5. Mixing, Filling and Release
   The production of a virus strain takes approximately six weeks from the thawing of the cells to the finished antigen concentrate. Another ten weeks are needed before the vaccine is ready for mixing, filling, packaging and regulatory approval. All in all, it takes about 16 weeks from the extraction of the cell until a finished seasonal flu vaccine is packaged and ready for delivery. In addition, external factors such as availability of strain-specific reagents can influence the timeline.

Importance of Flu Cell in Pandemic Response

The new production process gains special significance in view of an increasing risk of a pandemic. Flu experts from all over the world predict that a pandemic - a wave of influenza, spreading worldwide - will come, but they don’t know when. A suitable vaccine against a pandemic virus must be manufactured in the largest possible quantities as quickly as possible. The production facilities as well as the new flu cell culture facility of Novartis Vaccines could play an important role in this race against the pandemic virus, due to the potentially shorter lead time for production and greater safety in the process. This production is not dependent on chicken eggs, which in the event of a pandemic may not be available in sufficient quantity due to a virus deadly to birds.