Researchers seek fresh approach to HIV vaccine
Last month's cancellation of the largest ongoing HIV vaccine trial stopped yet another promising candidate. The growing pool of clinical failures--which includes a Merck ($MRK) vaccine--shows that a new approach is needed. This past week, academia offered up two new angles of attack.
Two papers take contrasting approaches to one of the big questions of HIV research: how to target a virus that mutates rapidly. In Nature Structural & Molecular Biology, scientists from The Scripps Research Institute and other academic centers report that the weak spot on the HIV virus--where mutation is limited--is larger than previously thought. Researchers have targeted the region because it is a constant on the fast-changing HIV virus. Evidence now suggests that antibodies can bind to the region in multiple locations and at varied angles.
Earlier efforts to target the region had limited success, with researchers reporting previously that the weak spot is concealed from the immune system. This contributed to vaccine discovery and development teams looking for different ways to generate immunity against HIV. An expansion of the range of viral peptides the immune system can target is one alternative. Cytotoxic T cells can only target a limited number of viral peptides, meaning HIV can easily evade the immune system. If researchers could tweak T cells to recognize a wide range of peptides, immune defenses would be effective against more HIV variants.
An advance in efforts to expand the effectiveness of T cells was published in Science. A team from Oregon Health & Science University (OHSU) found that cytomegalovirus (CMV) could improve T cells. The CMV was modified to express proteins from the nonhuman primate version of HIV, SIV. This process created T cells that recognized three times more SIV peptides than when a conventional vaccine is used. Several of the researchers have a stake in a vaccine company, TomegaVax, that may have a commercial interest in the technology.