More than five years after radical treatment, both Timothy Ray Brown and his German doctor are convinced he no longer has HIV.

Mr Brown and Dr Gero Hutter made their first-ever joint appearance together in the US on Wednesday, when Dr Hutter spoke at a symposium on gene therapy at Washington University in St Louis.

Mr Brown, a US citizen who previously lived in Berlin, was diagnosed with HIV in 1995.

In 2007, he also developed leukaemia while living in Germany. Dr Hutter performed a blood stem cell transplant using a donor with a rare gene mutation that provides natural resistance to HIV.

Dr Hutter claims the HIV resistant nature of the stem cells also transferred to Mr Brown.

Some doctors remain sceptical that the 46-year-old is cured. His case was first reported in the media in 2008 and described in the New England Journal of Medicine in 2009.

However, Dr Hutter said enough time has now passed to say without hesitation that Mr Brown is “cured”, citing the same five-year standard after which some cancer patients are said to be cured.

Jason Warriner, clinical director at the Terrence Higgins Trust, said the experience of Mr Brown is significant:

“Since the start of the epidemic 30 years ago, our understanding of how the virus works has increased dramatically, and has allowed us to develop drugs to manage the condition. However, this was the first time we’ve seen a medical process eliminate HIV from the body completely.

Mr Warriner added: “The transplant procedure that Timothy Ray Brown went through was complicated and life-threatening, and would only be used in extreme circumstances. It’s not the ‘cure’ we’re looking for.

He concluded: “However, it does tell us that eradication of HIV cells is possible, and the importance of that cannot be under-estimated. Until a functional cure is found, consistent condom use remains the best way to protect yourself and your partners from HIV.”