Successful tests: new vaccines against AIDS

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London (dapd). For the first time, researchers have tested several combination vaccines against AIDS, which also protect against an aggressive, resistant mixture of viruses. In tests on rhesus monkeys, the genetically engineered vaccines reduced the animals' risk of infection after single contact with simian immunodeficiency virus (SIV) by 80 percent. It took at least four doses of virus solutions to infect half of the vaccinated monkeys with the HIV-like disease. The animals infected despite the vaccination also had significantly fewer viruses in their blood than those not vaccinated, the researchers report in the journal Nature. (doi: 10.1038 / nature10766)

"No vaccine candidate against HIV-1 has so far managed to effectively prevent infection with various types of viruses that are difficult to neutralize," write Dan Barouch of Harvard Medical School in Boston and his colleagues. The RV 144 vaccine prototype, which was last tested on 16,000 people in Thailand in 2009, only reduced the infection rate by around a third. The new vaccine candidates consist of genetically modified adenoviruses, a type of virus that includes cold viruses. Genes for three proteins of the AIDS virus, Gag, Pol and Env, have been added to their genome. As a result, the vaccine viruses stimulate the recipient's immune system to produce specific antibodies against these three HIV proteins and to fight an infection.

"Our results have shown that this combination also offered vaccination protection against repeated administration of monkey eenids," the researchers report. The surface protein Env has proven to be decisive. Only when this was included in the combination vaccines did the vaccination prevent infection. Since the surface proteins of SIV (monkey AIDS virus) and HIV (human AIDS virus) are similar, this also applies to vaccines against AIDS in humans.

The combination vaccine that has been the most successful in the tests is soon to be tested in a first human clinical trial. Plans are already underway for test series in the USA, Thailand and Africa.

For their study, the researchers vaccinated 40 rhesus monkeys with one of four vaccine combinations or with a placebo. After six months, all monkeys were injected a total of six times with solutions with monkey Aids virus in the anus. During the entire duration of the study, the scientists monitored the virus infestation and the immune reaction of the animals with regular blood samples. "After the first virus transmission, 75 percent of the control monkeys were infected with SIV, but only 12-25 percent of the vaccinated animals," report Barouch and his colleagues. Half of the vaccinated monkeys were only infected after the virus had been transmitted three to four times.

According to the researchers, the result raises high hopes because the substances were also effective against mixtures of viruses from virus variants that are normally very difficult to control. The AIDS virus is genetically very changeable, so there are numerous different pathogen variants in circulation. To be effective, a vaccine must protect against as many of these types of viruses as possible. The scientists believe that this is the case with the substances being tested.

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