Superinfection

Superinfection – infection with a second strain of HIV in someone who is already HIV positive – has always been the focus of detailed research. There are only 50 known cases in the world, with each case being examined closely in a journal article or conference presentation.

A Seattle study has found that women who had been infected by two different strains of HIV had a big boost in their ability to fight off the virus, compared to women with one strain.

A team at the Fred Hutchinson Cancer Research Center spent five years monitoring the immune response of 12 women with superinfections in Kenya. They were compared to three women who were also HIV positive but had only been infected once. The researchers assessed how the women's antibodies were able to neutralise the other strains of HIV that they were exposed to.

They found that the women with the superinfections had 70 per cent more antibodies and their ability to fight off HIV was 50 per cent stronger. Senior author Dr Julie Overbaugh concluded that some of the superinfected women had a unique ability to neutralise, or fight back, many strains of HIV over time.

It is not known how the double infection works to boost immune response but the researchers hope that this finding will help the search for an effective HIV vaccine.

Meanwhile two separate studies conducted in Kenya and Uganda have indicated that HIV superinfection is more common than previously thought.

Researchers used sensitive tests to monitor the genetic structure of HIV. They found that the incidence of superinfection was similar to the incidence of initial infection with HIV.

However, these investigators admitted that they don’t yet know whether their findings have any clinical significance.