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BMJ 2002;325:564 ( 14 September )
 

News roundup

Patient is reinfected with a different HIV strain

Scott Gottlieb New York

Doctors have reported a rare case of HIV "superinfection," in which a person already infected with HIV became reinfected with a different strain of the virus.

The finding proves the importance of consistently practising safer sex, even between two HIV positive people, they say. But they warn that HIV superinfection could be another obstacle to developing an effective AIDS vaccine.

The patient, a 38 year old man whose blood counts of HIV had fallen sharply after drug treatment, had a resurgent viral load after stopping his medication during an AIDS vaccine trial. Tests showed that the cause was a new strain of HIV that had replaced the one he had had contracted two years earlier (New England Journal of Medicine 2002;347:731-6).

Weeks earlier the man had had unprotected sex several times while in Brazil. The new strain in his blood, known as subtype B, is endemic in Brazil. The patient’s initial strain, called AE, is prevalent in South East Asia.

"If you aren’t careful you [might] catch it twice," said Dr Bernard Hirschel, of the University of Geneva, one of the case report’s authors. Superinfection still seems to be rare, he said, but he added that the new finding had important implications for AIDS vaccine research.

The fact that natural infection does not necessarily protect against a range of HIV strains challenges the hope that one vaccine might do so, suggests an accompanying editorial by Dr Philip Goulder and Dr Bruce Walker of Massachusetts General Hospital, Boston. But "there are aspects of this case that need not leave us in despair," they write.

Dr Walker reported a similar case of superinfection, in a Boston man, at the recent AIDS conference held in Barcelona. Until now vaccine researchers have assumed that an effective vaccine would have to be made up of samples of each of the seven or eight major classes of HIV now circulating around the world.

But Dr Walker’s patient was infected with two viruses from the same class that were genetically very similar. It is probably far more common for people to be exposed to the same subtype of HIV over time, whereas this man was exposed to a new strain when he went abroad, write Dr Walker and Dr Goulder in the editorial.

Vaccine researchers are already working on the premise that it will be difficult to develop a single vaccine that fights several strains of HIV. But it is becoming clearer that a fully protective vaccine will potentially have to contain hundreds or thousands of viral samples. Such a vaccine is very hard to manufacture and might not be well tolerated.
 
 

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