'Profound effects'
People naturally mount a defence against the virus by producing an army of protein based weapons - antibodies. But in most cases these are not powerful enough to defeat it.
The international research team harvested copies of unusually potent ones, capable of neutralising many different strains of HIV.
Patients given the highest concentrations were able to fight the virus for some time, dampening the replication of HIV in their blood.
The strength of this protection varied - in some it lasted more than four weeks.