The implementation of scientifically proven HIV prevention strategies is helping to reduce the number of new infections — the annual HIV infection rate globally fell by 22 percent from 2001 to 2011 — but a great deal more must be done. Significant scale-up of proven HIV prevention strategies coupled with the discovery of new HIV treatment and prevention interventions are needed to achieve an end to the global HIV/AIDS pandemic. A safe, effective and durable HIV vaccine is an essential cornerstone to the long-term strategy to achieve this goal.
Developing a safe and effective HIV vaccine has been a long and difficult process largely because HIV has proven to be an especially tough target. Recent developments with the HVTN 505 clinical trial and analyses from the HVTN 503 “Phambili” vaccine study have been disappointing, but they also provided clear answers about investigational vaccine strategies that, ultimately, were not effective. Still, the new directions for HIV vaccines that have been recently initiated define our future path and will be pursued.
Among many projects, scientists continue to explore findings from the RV 144 HIV vaccine study in Thailand, which, in 2009, provided proof-of-concept that an HIV vaccine can afford a modest level of protection. Ongoing research related to the Thai trial is providing important information about human immune responses and other factors that may explain why the investigational vaccine protected some trial volunteers from HIV infection but not others. Such data will help advance researchers’ understanding of HIV’s structure and vulnerabilities and help guide the development of future HIV vaccine candidates. Large-scale investigational vaccine clinical trials designed to build on the RV 144 results and create a more robust and durable level of protection are expected to begin in two-to-three years in South Africa.
In basic research, scientists are making important discoveries about broadly neutralizing antibodies capable of disabling a wide range of HIV strains when tested in the laboratory setting. For example, NIAID scientists recently charted the co-evolution of HIV and a strong antibody response in an HIV-infected study participant, who is one of the 20 percent of HIV-infected individuals who naturally develops broadly neutralizing antibodies to the virus after several years of infection. Their findings could help identify which proteins to use in an investigational vaccine to induce broadly neutralizing antibodies more quickly. In another advance, a team of NIH scientists recently developed a new tool to identify broadly neutralizing antibodies from blood samples, which could help speed HIV vaccine research.
Other interesting basic research findings have included the identification of a new HIV-suppressing protein, called CXCL4, in the blood of HIV-infected individuals. NIAID scientists found that CXCL4 binds to HIV in such a way that the virus cannot attach or enter a human cell, leading to the conclusion that it may serve to regulate viral replication in an infected individual and, therefore, control the pace at which HIV disease progresses. Additionally, NIAID researchers found that even though HIV diversifies widely in infected individuals over time, the virus strains that are passed on through heterosexual transmission often resemble the strain that originally infected the transmitting partner. Learning more about the characteristics of these dominant strains could help inform HIV vaccine design.
Recent NIAID investments in basic research toward innovative HIV vaccine discovery researchand vaccine immunology and immunogen discovery should also prove fruitful in the coming years for HIV vaccine research.
On this HIV Vaccine Awareness Day, NIAID thanks the thousands of men and women who have selflessly volunteered for clinical studies and the scientists and clinicians working to find an effective HIV vaccine. NIAID shares your commitment and will continue the important research needed to make a protective HIV vaccine a reality.
Editor’s note: Please see our National HIV Vaccine Awareness Day video with Dr. Carl Dieffenbach from NIAID, NIH.