Proteins called broadly neutralizing antibodies (bNAbs) are
thought to be the future of treating and preventing HIV infections. A bNAbs
recently characterized by researchers can neutralize the virus in many
ways---increasing the antibody’s promise as a therapeutic.
bNAbs have been found in blood samples from some HIV
patients whose immune can naturally control the infection. These antibodies may
protect a patient’s healthy cells by recognizing a protein called the envelope
spike, present on the surface of the HIV virus. And inhibiting, or
neutralizing, the effect of the virus. Caltech researchers have found that one
particular bNAb may be able to recognize this signature protein, even as it
takes on different conformation during infection---making it easier to detect
and neutralize the viruses in an infected patient.
The process of HIV infection begins when the virus come in
contact with human immune cells called T cells
that carry particular protein, CD4, on their surface. Three part protein
called envelope spike on the surface of the virus recognize and bind to the CD4
proteins. The spike can either be closed or open conformation, going from
closed to open when the spikes bind with CD4. The open conformation then
triggers fusion of the virus with the target cell, allowing the HIV virus to deposit
its genetic material inside the host cell, forcing it to become a factory for
making new viruses that can go and infect other cells.
The bNAbs recognize the envelope spike on the surface of the
HIV, and most known bNAbs only recognize the spike in the closed conformation. Although
the only target of neutralizing antibodies is the envelope spike, each bNAbs
actually function by recognizing one specific target, or epitope, on this
protein.
Some target allow more effective neutralizing of the virus,
and therefore bNAbs are more effective against HIV that others.
In 2014, Bjorkamn and her collaborator at Rockefeller
University reported initial characterization of a potent bNAb called 8ANC195 in
the blood of HIV patient whose immune systems could naturally control their
infection.
They also discovered that this antibody could neutralize the
HIV virus by targeting a different epitope than any other identified bNAb.
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