While many over-60s have already started getting their flu jabs in anticipation of the upcoming winter season, new data has revealed that a common food preservative could influence how well a flu vaccine works.
The study, conducted by Michigan State University in the United States and presented at the 2019 Experimental Biology meeting in Orlando, says an additive known as tert-Butylhydroquinone (tBHQ) could be linked to an altered immune response and may hinder flu vaccinations.
Worryingly, tBHQ is found in a number of food products including cooking oils, frozen meats and fish and processed snacks such as chips and crackers. Some products don’t always include the additive as an ingredient on the label.
“If you get a vaccine, but part of the immune system doesn’t learn to recognise and fight off virus-infected cells, then this can cause the vaccine to be less effective,” lead author Robert Freeborn said in a statement. “We determined that when tBHQ was introduced through the diet, it affected certain cells that are important in carrying out an appropriate immune response to the flu.”
Researchers conducted tests on mice as part of the study, using various strains of flu including H1N1 and H3N2 and focused on particular t cells called CD4 and CD8s. They then incorporated tBHQ into the food of mice at levels comparable to human consumption.
“CD4 T cells are like movie directors that tell everyone else what to do,” Freeborn explained. “The CD8 T cells are the actors that do what the director wants.”
Researchers analysed several response factors to determine whether T cells showed up, if they were able to do the right job and if they could recognise and remember the invading virus. They saw a reduced number of CD8 T cells in the lung and a decrease in the number of CD4 and CD8 T cells that could identify the flu virus in the mice that were exposed to tBHQ. These Mice also developed widespread inflammation and mucus production in their lungs.
The tBHQ additive also slowed down the initial activation of T cells, which reduced the ability to fight off an infection sooner and enabled the virus to run rampant until the cells activated.
Another aspect of the study showed tBHQ could impact the immune system’s ability to remember how to respond to the flu virus. It was a particular problem when another strain was introduced at another time and lead to longer recovery and additional weight loss in mice.
“It’s important for the body to be able to recognise a virus and remember how to effectively fight it off,” Freeborn said. “That’s the whole point of vaccines, to spur this memory and produce immunity. TBHQ seems to impair this process.”
Australia’s 2017 flu season was one of the worst on record, killing more than 1,200 people. People over 65 are at particular risk when it comes to influenza and are the most likely to die from complications caused by the virus, mainly due to the immune system weakening in older age. Initial symptoms of the flu include fever, muscle aches and cough, but these can quickly develop into something more serious, such as pneumonia.
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