August 14, 2024
Two-step flu vaccination strategy shows promise in swine
Researchers at the Institute of Virology and Immunology (IVI) in Mittelhausern, Switzerland, have developed a novel two-step flu vaccination strategy that has shown promising results in swine, Genetic Engineering & Biotechnology News reported.
The approach combines an intramuscular injection of a viral-vectored flu vaccine with a nasal spray administration of a novel attenuated live flu virus. This strategy was found to be both safe and effective in animal studies, according to the scientists led by Dr Robin Avanthay and Dr Gert Zimmer.
The study, conducted in collaboration with researchers from the University of Bern, Switzerland, and the University of Murcia, Spain, was published in PLOS Pathogens under the title "Evaluation of a novel intramuscular prime/intranasal boost vaccination strategy against influenza in the swine model." The researchers suggest that with further testing, this novel vaccination method could represent a next-generation strategy for more effective flu prevention, with potential adaptability to emerging influenza A virus (IAV) subtypes, which could help in managing future IAV pandemics.
Influenza A virus is known to cause acute respiratory infections, typically leading to symptoms such as high fever, muscle pain, headache, coughing, and fatigue in humans. In severe cases, it can lead to viral pneumonia and acute respiratory distress syndrome (ARDS), particularly in vulnerable populations like the elderly and those with underlying health conditions.
Traditional seasonal flu vaccines usually consist of inactivated flu virus components that are injected into the muscle, aiding the immune system in recognising and combating the disease. However, these vaccines have limited efficacy in preventing infection in the upper respiratory tract, where flu infection initially takes hold. The team noted that such vaccines might inadvertently encourage the evolution of flu strains that can evade immune detection.
An alternative method, known as live-attenuated influenza vaccines (LAIV), utilises a weakened form of the flu virus that is administered through the nose, directly targeting the upper respiratory tract. This method triggers a more comprehensive immune response against the infection. However, the researchers found that although their novel LAIV candidate, NS1(1–126)-ΔPAX, induced strong immune responses in swine, it was also shed from the upper respiratory tract for an extended period, raising concerns about the potential transmission of the virus to individuals with compromised immune systems.
To address these concerns, the IVI team developed a two-step immunisation strategy. The first step involves an intramuscular injection using a vesicular stomatitis virus (VSV) as a vaccine delivery vehicle. This VSV-based vaccine is engineered to perform only a single round of infection, enhancing safety. The second step involves administering the live-attenuated flu vaccine candidate NS1(1–126)-ΔPAX via the nasal route.
In the study, this two-step vaccination approach resulted in a robust immune response, both systemically and in the upper respiratory tract. The vaccinated swine showed no signs of infection after being exposed to a virulent flu virus, and the live vaccine boosted the systemic flu-specific antibody response. Additionally, the two-step strategy significantly reduced the shedding of the vaccine candidate from the upper respiratory tract, addressing one of the key safety concerns associated with live vaccines.
Dr Zimmer summarised the findings, stating, "The combination of the intramuscular immunisation with VSV-H1 and the intranasal boost using the NS1(1–126)-ΔPAX LAIV enhanced safety by strongly reducing LAIV shedding and completely preventing shedding of the challenge virus."
The research team believes that this novel two-step vaccination strategy may offer extended protection and improved immunity against flu virus variants. They plan to conduct further experiments to determine whether this approach could also provide protection against antigen-drifted IAV strains.
The study concludes that the two-step vaccination protocol could serve as a foundation for developing alternative, next-generation flu vaccines. By inducing strong mucosal immunity, this strategy has the potential to reduce the spread of influenza A virus and enhance herd immunity, particularly in livestock. Furthermore, its adaptability to emerging IAV subtypes could prove useful in controlling future IAV pandemics.
- Genetic Engineering & Biotechnology News