T Cells Found to Independently Prevent Acute Viral Infections

A team from Duke-NUS Medical School and Singapore General Hospital has found that T cells can provide sterilizing immunity against viral infections, a capability previously attributed solely to neutralizing antibodies. This discovery challenges long-held beliefs about immune system function and opens new avenues for vaccine development.

The research, published in Nature Microbiology, involved 33 healthy adults aged 21 to 45. Participants received either a yellow fever or Japanese encephalitis vaccine, followed by a challenge with the other virus 28 days later. This cross-vaccination approach allowed scientists to isolate and study T cell responses independent of neutralizing antibodies.

Results showed that T cells from yellow fever vaccination effectively controlled Japanese encephalitis virus challenge, reducing viral loads and antibody production. In 15% of participants, T cells present at high levels post-vaccination controlled the challenge infection to undetectable levels, preventing new antibody formation.

Professor Ooi Eng Eong, lead author, stated, "We found that T cells can serve as the first line of defence, not just a supportive element in protecting us from acute viral diseases." This finding suggests that current methods of measuring herd immunity by antibodies alone may be underestimating population protection.

The study's implications extend to vaccine design. According to first author Shirin Kalimuddin, “We need to rethink how we design and develop vaccines. Vaccines that generate high levels of antibodies do not necessarily generate high levels of T cells. Development of vaccines must incorporate the viral components that T cells recognise and react against. Indeed, our findings may explain why some vaccines offer better protection against viruses when they are able to trigger a broader T cell response.”