Experts hopeful for HIV vaccine

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iol scitech jan 6 monkey lab AP File photo: In science it is generally accepted that HIV is a descendant of SIV, which originated in monkeys, but became HIV in humans.

Barcelona - A prophylactic vaccine, which cured monkeys of an HIV and Aids-like illness – simian immunodeficiency virus (SIV) – has given a ray of hope in finding an HIV vaccine.

In a study, which was conducted by US scientists, early results have shown that inoculating monkeys with a vaccine that contained traces of the virus not only gave them 50 percent protection, the vaccine also had the potential of protecting them against TB.

In science it is generally accepted that HIV is a descendant of SIV, which originated in monkeys, but became HIV in humans.

Presenting the results of the five-year study at the annual Aids Vaccine Conference in Barcelona, lead researcher Louis Picker from Oregon Health and Science University, said while the study still needed to be proven on humans, the fact it completely cleared the virus from 50 percent of the monkeys was “promising”.

The study was the first proof that the Aids-causing virus could be eliminated. After they were inoculated with SIV-protein-expressing rhesus cytomegalovirus (RhCMV/SIV) vectors, monkeys were later exposed to SIV. Researchers later discovered that half of those that were inoculated were cleared of detectable infection within the first two or three years after infection.

Preliminary results also showed that the vaccine had a protective factor against TB, eliciting much stronger immune response compared with the standard TB vaccine – BCG, which is used worldwide.

Although researchers could not rule out residual virus below level of detectability, the latest data suggested strong evidence that the immune system was capable of clearing the virus, which so far could not be cleared by antiretrovirals (ARVs) in humans.

While ARVs could bring down viral load to zero, it couldn’t get rid of HIV. Picker said the latest study demonstrated that memory T-cells, which fought infection before it got to human cells, could shut down the production of SIV infection, which had the same replication pattern as the HI virus.

“Our results also suggest that an effector memory T-cell-targeted vaccine might contribute to HIV cure strategies. Although the SIV reservoirs that initially develop in RhCMV/SIV vector-vaccinated controllers are smaller in size and possibly different in character from HIV/SIV reservoirs in the setting of ART administration – it is conceivable that the viral-specific T-cells elicited and maintained by these vectors might exert potent immune pressure on cells with any HIV protein,” he said.

It was also possible that these responses created by the vaccine might stringently control the “rebound” infection after ART withdrawal. The long-term and potent immune surveillance produced by the vaccine made it a promising candidate for vaccine strategies intended to prevent and cure HIV and Aids.

The conference started on Monday and is due to end on Thursday. - Cape Argus

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