A new antibody discovered in a patient that protects against multiple strains of flu could be adapted into a universal flu vaccine.

Winter flu pandemics are a serious public health concern and pose a particular risk to more vulnerable people in society; including the elderly, young children, or people with compromised immune systems. Every year in the UK a flu vaccine is created to provide immunity for the predicted most common flu strains, but this approach is limited in that even people who have the vaccine can still be infected by other flu strains.

A universal vaccine that could give immunity for all flu strains could therefore reduce the public health impact of flu dramatically.

In 2017, a blood sample was recovered from a hospitalised flu patient at Barnes-Jewish Hospital in St. Louis. Researchers quickly realised that the blood displayed unusual behaviour; containing antibodies that were both targeting hemagglutinin on the surface of the virus and something else that could not be determined. It was identified that the antibodies were targeting neuraminidase, a protein essential to virus reproduction.

Neuraminidase is located on the virus surface and stimulates infected host cells to release the replicated viruses into the body.  It was identified that one of the antibodies from the patient’s blood could target all known types of neuraminidase in both human and non-human flu strains. This is unusual, as antibodies as usually specific to one strain.

Mice were given a usually lethal dose of influenza virus were treated with the antibodies sampled from the patient’s blood. One antibody, IG01, protected the mice against all 12 strains.

To find out exactly how IG01 was able to have a strong inhibitory effect on multiple different strains, the binding interaction between IG01 and neuraminidase was modelled computationally. It was found that IG01 has loops that the neuraminidase protein could slip between. The loops targeted the residual amino acids of neuraminidase, not the active site. This explains IG02’s broad effect, as the residual amino acids to do differ significantly between strains.

The researchers now intend to develop a useable vaccine based on the IG01 antibody.

 

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