by Mike Andrew - SGN Staff Writer

HIV can form essentially invulnerable 'viral reservoirs' even before it is detectable in a patient's blood, a new study shows. If true, the findings mean that early treatment of HIV, once thought to offer hope for a cure, may not be as effective as once thought.

The study, published in the journal Nature, used rhesus monkeys infected with SIV (simian immunodeficiency virus). The monkeys were then given antiretroviral drugs as early as three days or as late as two weeks after infection.

Treatment was stopped after six months, but the virus re-emerged regardless of how quickly antiretroviral treatment started. From that result, researchers concluded that viral reservoirs formed incredibly early in the course of the infection.

'Our data show that in this animal model, the viral reservoir was seeded substantially earlier after infection than was previously recognized,' Dan Barouch, professor of medicine at Harvard Medical School, said.

'We found that the reservoir was established in tissues during the first few days of infection, before the virus was even detected in the blood.'

The new findings would explain the case of the so-called 'Mississippi Baby,' the young girl who was believed to have been cured of HIV after massive doses of antiretrovirals were administered to her very soon after birth.

She was given HIV drugs for the first 18 months of life, but then they were stopped. Initially no HIV was detected in her blood, and there was hope she had been effectively cured.

However, the girl, now four years old, now tests HIV-positive after nearly two years off the drugs.

'The unfortunate news of the virus rebounding in this child further emphasizes the need to understand the early and refractory viral reservoir that is established very quickly following HIV infection in humans,' Barouch said.

Kai Deng and Robert Siliciano, of the School of Medicine at Johns Hopkins University, in Baltimore, Maryland, said that the new study may make efforts to cure HIV more complicated, but does not necessarily rule out benefits from early treatment.

'These data indicate that the viral reservoir could be seeded substantially earlier than previously assumed, a sobering finding that poses additional hurdles to HIV eradication efforts,' they said.

'Although early treatment may not prevent reservoir seeding, it has been consistently shown to reduce the size of the reservoir.'

They also cautioned that there may be significant differences between experiments conducted on monkeys and the human HIV infection, but concluded that the findings 'suggest new approaches in addition to early treatment will be necessary to eradicate HIV infection.'

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