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Universal Flu Vaccine Successful in Protecting Mice Models from Multiple Viral Strains

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More than 35 million cases, 710,000 hospitalizations, and 50,000 deaths have been caused by the influenza virus in the United States since 2010, according to the Centers for Disease Control and Prevention. In the 2015-2016 flu season, the agency estimated 2.5 million influenza-associated medical visits and 71,000 influenza-associated hospitalizations, but they managed to prevent about 5.1 million of influenza illnesses. Researchers at the George State University are now developing a universal vaccine to solve the growing flu crisis.

Each year, a flu vaccine is made to combat the upcoming wave of cases. The information required to develop the next flu shot comes from the data gathered by 142 national influenza centers in 113 countries, all year round. The data include the efficiency of spreading strains and efficacy of previous vaccines against these to help scientists predict the next strain of influenza. According to the CDC, there are three different production methods of the influenza vaccine:

1. Egg-based vaccine: This is the most common method used to produce flu vaccines used for more than 70 years. The method is cost-effective but, slowly yields supplies. It has been found cause further mutations in the virus.

“Producing flu vaccines in eggs can be a problem because flu viruses often acquire adaptive mutations when grown in eggs,” said Dr. Scott Hensley, an associate professor of microbiology at the University of Pennsylvania.

2. Cell-based vaccines: This method uses cell culture techniques to produce flu vaccines, which is an alternative to the egg-based method. The primary advantage of cell-based vaccines is rapid vaccine production, particularly useful during a pandemic. It is also an advantage for those who have egg allergies.

3. Recombinant vaccines: This method has been approved by the US Food and Drug Administration in 2013, and it uses the recombinant technology. The technology does not use eggs or mammalian cells; instead, it uses insect cells to develop the vaccine.

The vaccines produced by these methods were not effective to protect people from the current influenza outbreak. According to a commentary published in The New England Journal of Medicine, the current flu vaccine is only 10 percent effective against the H3N2 influenza of the season. The authors theorized that the severely low efficacy of the vaccine was connected to the viral mutation.

This problem is what the research team at Georgia State plans to fix by creating a universal vaccine. Typically, the seasonal flu vaccines people receive work by targeting the external head of the virus’s surface protein called hemagglutinin or HA. Influenza virus triggers the immune system to produce antibodies to terminate inactivated virus particles that contain the headpiece of the protein HA. The response prevents the head from attaching to cell receptors and stops the infection. However, the viral head is highly variable and differs for each virus.

In the new study, the researchers used a new approach that targets the inner portion or stalk of the protein HA, instead of the external head. They administered the experimental vaccine via injection into the mice models, and exposed them to different influenza strains, such as H1N1, H3N2, H5N1, and 7N9. They found that all mice were protected against the virus and the number of viral particles in the lungs have been reduced.

“Vaccination is the most effective way to prevent deaths from influenza virus, but the virus changes very fast and you have to receive a new vaccination each year. We’re trying to develop a new vaccine approach that eliminates the need for vaccination every year. We’re developing a universal influenza vaccine. You wouldn’t need to change the vaccine type every year because it’s universal and can protect against any influenza virus,” said Dr. Bao-Zhong Wang, an associated professor in the Institute for Biomedical Sciences at the George State.

Their experiment was focused on inducing responses to the stalk part of the influenza virus called glycoprotein, a simple protein with a sugar used in many biological processes, such as immunity, digestion, and reproduction. Compared to the current vaccine development, the experimental vaccine targets something that all influenza strain share, which could lead to universal protection against the disease.

During the development of the experimental vaccine, the researchers faced an issue with the stalk of the virus. It was unstable and was likely to affect the efficacy of the vaccine in the long run. So, they assembled the stalk domain into a protein nanoparticle to create the vaccine. The nanoparticle protected the antigenic protein from instability and prevented degradation. Their findings also found that the immune system can detect the protein inside the nanoparticle, triggering an immune response.

“This vaccine is composed of very conserved domains. That’s the reason why the induced immunity can offer universal protection,” said Dr. Lei Deng, the first author of the study and a postdoctoral researcher in the Institute for Biomedical Sciences at Georgia State.

The research team is planning to test the experimental vaccine in ferrets to replicate the respiratory system of humans. The vaccine will only become available to the public once it has passed clinical trials and has obtained approval from the FDA.

[메디컬리포트=Ralph Chen 기자]

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