Nature-like eCD4-Ig protein binds to and inactivates HIV, Nature says.
The search for a method that would immunize humans against HIV infection has been going on for 30 years. A new achievement is an antibody-like protein developed by Prof. Michael Farzan from the Scripps Research Institute in Jupiter, Florida, working with scientists from several other institutions. The protein sticks to the surface of HIV and neutralizes it, preventing it from infecting blood cells.
The HIV virus binds to two receptors on the surface of the lymphocyte. First, the gp120 protein present on the surface of the virus binds to the CD4 receptor of the lymphocyte. This connection reveals another lymphocyte receptor – CCR5. The new protein, which was designed based on the available knowledge about HIV, is a combination of a CD4 fragment with a small fragment of CCR5 and a piece of an antibody – that is why it can inactivate the virus. They were called eCD4-Ig.
Under laboratory conditions, eCD4-Ig is more effective than any known natural antibody in stopping HIV from infecting cells. It blocks all known HIV variants and the simian SIV virus.
To test how it works in a living organism, Farzan’s team inserted the gene for eCD4-Ig into the harmless AAV virus and infected four monkeys with it (via an intramuscular injection). The virus forced the animals to mass-produce proteins.
The researchers then administered gradually increasing doses of HIV to the four protein-producing monkeys and a control group of four. During 34 weeks, none of the animals treated with eCD4-Ig became infected, while the entire control group was infected. For the duration of the experiment (40 weeks), the monkeys produced eCD4-Ig, so the researchers speculate that this could continue for a lifetime.
Studies have shown no evidence of an immune response against an artificial antibody – presumably because it is very similar to the body’s own antibodies.
There will be many more monkeys to be tested before any clinical trials can begin, Farzan said. (PAP)