HEPATITIS B virus (HBV) vaccinations protect through immunological memory, i.e. the vaccine ‘trains’ the immune system to recognise a specific antigen that the body has previously encountered, and eliminate it. In a recent study by Dr Ratna Wijaya, Westmead Institute for Medical Research (WIMR), Westmead, Australia, memory natural killer (NK) cells have been described for the first time.
Immunological memory was thought to be specifically driven by B and T immune cell responses; however, recent mice studies suggested that NK cells also have the ability to ‘remember’ viral infections. It remained unknown whether this applied to human infections and therefore, Dr Wijaya and her team studied NK cells in humans who had been vaccinated against, or infected with, HBV and compared them to those that had no previous exposure to the virus.
HBV is a viral infection that attacks the liver and can cause both acute and chronic disease. Some individuals infected with HBV can eliminate the virus; however, others, particularly those exposed in childhood, may develop chronic infections. Without appropriate treatment, HBV can lead to liver cancer, and liver cirrhosis; therefore, it is pivotal to prevent such infections where possible.
The study results revealed that NK cells from those vaccinated against or infected with HBV demonstrated higher cytotoxic and proliferative responses compared to those with no previous exposure. Prof Golo Ahlenstiel, WIMR, stated: “This finding is quite significant, as it helps our understanding of how the body fights against HBV following vaccination.” He further noted: “Previously, we thought that the NK immune response was part of our innate immune system. The innate immune system fights against all antigens (foreign bodies, such as viruses), rather than specifically targeting certain antigens. We have now confirmed that NK cells in humans can acquire an immunological memory, and specifically target HBV-infected cells in subsequent infections.”
The researchers hope that through their findings, the antiviral properties of memory NK cells can be utilised to develop treatments and improve vaccines.