Gene-editing offers HIV breakthrough

SCIENTISTS have identified a promising gene therapy that they hope could become the first major anti-HIV treatment since antiretrovirals were introduced in the1990s.

Using the novel geneediting software CRISPR, scientists at Temple University in the US, were able to almost entirely eliminate HIV from the cells of three different sets of laboratory mice – becoming the first team to show CRISPR can be used to remove the virus from an animal. They published their results in the journal Molecular Therapy.

CRISPR, or its technical name CRISPR-CAS9, acts as a type of molecular scissors. The CAS9 proteins do the cutting, guided by a DNAlike structure called guide RNA.

In this study, researchers designed guide RNA to match the sequence of genetic bases that make up HIV and inserted CRISPR into the cells of three HIVinfected mice: genetically modified mice with HIV-1 DNA in their genome, mice infected with the mice version of HIV, and mice embedded with HIV-infected human cells.

Guided, by the specially programmed RNA, the CAS9 proteins should cut up any HIV sequences encountered. The first and second groups saw 95 and 96% of their HIV disappear. The last group, the one with HIV-infected human cells, were entirely free of HIV cells.

“As long as both CAS9 andRNA are inside the cells, they can keep doing their duty... cutting HIV DNA out as soon as HIV DNA is inserted into the cellular genome,” Won-Bin Young, one of the study’s authors, said.

This method is particularly promising because of its ability to handle what researchers call “HIV escape”. HIV is difficult to treat and impossible so far to cure because the virus can mutate quickly and adapt to any particular anti-virals. That’s why HIV patients take a complex combination of antiretrovirals.

TheCRISPR method solves this problem by encoding several guide RNAs to attack several different HIV strains.

Success in mice, however, does not mean a cure for humans. But it is an encouraging development and researchers say their next step is a study in primates, followed, they hope, with human clinical trials.

The human brain is a major obstacle becauase the HIV in delicate brain cells are particularly hard to reach and in a past gene therapy trial there has been a strong immune response where a patient died. “To reach 100% efficiency of excising HIV from a human body is still a long way to go”, Young said.

Between 6.7 million and 7.4 million people are living with HIV in South Africa, according to a 2015 UN Aids report.

In the more than thirtyfive years since the disease first reached epidemic scales, only one person has been cured of HIV. Timothy Ray Brown was cured as a freak accident after undergoing radiation therapy and a bone marrow transplant for leukemia in 2007. Scientists are not sure how this happened.