Experimental drug shown to block all HIV strains: study

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WASHINGTON. KAZINFORM - U.S. researchers on Wednesday announced "a remarkable new advance" in the development of a potent drug to protect against infection of HIV, the virus that causes AIDS, the deadly disease currently without cure, Kazinform refers to Xinhuanet.com.

They reported in the British journal Nature that an experimental protein-based drug they developed blocks every strain of HIV-1, HIV-2 and the simian version of the virus, SIV, that has been isolated from humans or rhesus macaques, including the hardest-to-stop variants.

The drug, named eCD4-Ig, also protects against much-higher doses of virus than occur in most human transmission and does so for at least eight months after injection.

"Our compound is the broadest and most potent entry inhibitor described so far," lead author Michael Farzan, professor of the Scripps Research Institute, said in a statement.

Conventional vaccines for HIV trigger the release of antibodies to neutralize the virus, but even the best broadly neutralizing antibodies struggle to protect against all strains of HIV.

In fact, the past 30 years have been marked by a discouraging search for an effective HIV vaccine.

"Unlike antibodies, which fail to neutralize a large fraction of HIV-1 strains, our protein has been effective against all strains tested, raising the possibility it could offer an effective HIV vaccine alternative," Farzan said.

HIV normally invades the body through two receptors on the surface of the immune cells: one is called CD4, and the other is called CCR5.

The new strategy presented by Farzan and his team produces mimics of the two receptors, which bind to the virus and block it from infecting cells.

"When antibodies try to mimic the receptor, they touch a lot of other parts of the viral envelope that HIV can change with ease," said first author Matthew Gardner of the Scripps Research Institute. "We've developed a direct mimic of the receptors without providing many avenues that the virus can use to escape, so we catch every virus thus far."

In test-tube experiments, they demonstrated that eCD4-Ig binds strongly to HIV-1 and irreversibly inactivates it, and can inhibit a range of HIV-1 viruses, including those resistant to the best broadly neutralizing antibodies.

Delivery of this drug to four rhesus macaques is also shown to protect these animals from multiple infectious challenges with SIV for at least 34 weeks after inoculation.

In an accompanying opinion article, Nancy Haigwood of the Oregon Health & Science University, who was not involved in the study, noted that the sample size of the monkey experiments was quite small and that larger experiments in non-human primates are warranted.

Further research is needed to investigate the effectiveness and safety of the drug in humans, she said.

"However, in the absence of a vaccine ... and given the lack of major breakthroughs on the horizon to provide one, the idea of conferring potent, sustained vaccine-like protection against HIV infection ... is certainly worth strong consideration," Haigwood wrote.

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