Potent antibody neutralises nearly all HIV strains

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Scientists have identified an antibody that potently neutralises nearly all HIV strains and may potentially help treat or prevent the deadly infection. The antibody was identified from an HIV-infected person that neutralised 98 per cent of HIV isolates tested, including 16 of 20 strains resistant to other antibodies of the same class.The remarkable breadth and potency of this antibody, named N6, make it an attractive candidate for further development to potentially treat or prevent HIV infection, researchers said. The scientists, led by Mark Connors from National Institutes of Health (NIH) in the US, also tracked the evolution of N6 over time to understand how it developed the ability to potently neutralise nearly all HIV strains. This information will help inform the design of vaccines to elicit such broadly neutralising antibodies. Identifying broadly neutralising antibodies against HIV has been difficult because the virus rapidly changes its surface proteins to evade recognition by the immune system. In 2010, scientists at National Institute of Allergy and Infectious Diseases (NIAID)'s Vaccine Research Center (VRC) discovered an antibody called VRC01 that can stop up to 90 per cent of HIV strains from infecting human cells. Like VRC01, N6 blocks infection by binding to a part of the HIV envelope called the CD4 binding site, preventing the virus from attaching itself to immune cells. Findings from the study showed that N6 evolved a unique mode of binding that depends less on a variable area of the HIV envelope known as the V5 region and focuses more on conserved regions, which change relatively little among HIV strains. This allows N6 to tolerate changes in the HIV envelope, including the attachment of sugars in the V5 region, a major mechanism by which HIV develops resistance to other VRC01-class antibodies. The new findings suggest that N6 could pose advantages over VRC01, which currently is being assessed as intravenous infusions in clinical trials to see if it can safely prevent HIV infection in humans, researchers said. Due to its potency, N6 may offer stronger and more durable prevention and treatment benefits, and researchers may be able to administer it subcutaneously (into the fat under the skin) rather than intravenously. In addition, its ability to neutralise nearly all HIV strains would be advantageous for both prevention and treatment strategies.

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