Superinfection with HIV may occur despite a strong and effective HIV-specific immune response to an existing virus, Dr Bruce Walker of Massachusetts General Hospital and Harvard Medical School told the Fourtheenth International AIDS Conference in Barcelona today.
Dr Walker reported that a man involved in a treatment interruption study had achieved virological control after three cycles of treatment and interruption. When viral breakthrough appeared to occur, Dr Walker and his team investigated the case in detail.
Dr Walker found that the man had been infected with a new B clade virus following an unprotected sexual encounter. The new virus was only 12% different to the man´s original virus, nevertheless he was unable to control the second infection. The existing HIV-specific CD8 immune response was less able to recognise the new virus, leading to uncontrolled viral replication.
The study has implications for safer sex education targeting HIV-infected people and for vaccine development.
“I think the public health message is that it is possible to become re-infected with a second version of HIV,” Dr Walker told the meeting. "I don´t want to draw too many conclusions from a single case, but he was definitely controlling one of the viruses and not the other.”
The case casts doubt on a key approach to vaccine development which assumes that a strong HIV-specific CD8 response can prevent infection with a wide range of HIV variants.
“It is terrible news,” leading researcher Dr Brigitte Autran said in response to Dr Walker´s presentation.
Walker B. Harnessing the immune system to fight HIV infection. Fourteenth International AIDS Conference, Barcelona, abstract WeOrA197, 2002.