On May 18th, we celebrated HIV Vaccine Awareness Day. The goal of developing a safe and effective vaccine remains to be an overarching research priority and HIV Vaccine Awareness Day is meant to recognize and thank the thousands of volunteers, community members, health professionals, and scientists who are working together to make an HIV vaccine a reality.
In the early days of the epidemic, many experts thought that we would have an effective vaccine within two or three years of the start of the epidemic. An effective vaccine teaches the immune system to recognize and respond to a specific harmful organism, and despite substantial advances in our understanding of HIV and the immune system, a successful HIV vaccine continues to present a number of scientific challenges.
In March 2016, Carl Dieffenbach, Director of the Division of AIDS at the National Institutes of Health, delivered a presentation on the current research and development of an HIV vaccine. There are currently two primary approaches being used to develop such a vaccine: an inductive (or empirical) approach and a deductive (or theoretical) approach.
The Inductive Approach
In 2009, a Thai clinical trial known as RV144 found 31% efficacy for a new HIV vaccine. RV144 tested a vaccine strategy that used a poxvirus-vectored vaccine called ALVAC-HIV to "prime" the immune system and a different protein vaccine called AIDSVAX to "boost" it. While the overall protection bestowed by the vaccine was modest, the implications were promising because the RV144 was the proof-of-concept that an AIDS vaccine could reduce risk of HIV acquisition in humans. The promising results of the study led to the formation of the Pox-Protein Public-Private Partnership (P5), a diverse group of organizations, including NIAID, committed to building on the success of RV144.
One of the partnership's early undertakings was starting the development to identify a vaccine candidate for eventual licensure. This included HVTN 100, a phase I/II clinical trial in South Africa. HVTN 100's early data demonstrated the safety and ability of the vaccine candidate to produce a robust immune response. Building on the the success of HVTN 100, on HIV Vaccine Awareness Day, NIAID announced a decision to move forward with HVTN 702, a new Phase 2b/3 HIV vaccine efficacy clinical trial in South Africa beginning this year. Anthony S. Fauci, MD, Director of NIAID and co-founder of the trial has stated, "For the first time in seven years, the scientific community is embarking on a large-scale clinical trial of an HIV vaccine, the product of years of study and experimentation. A safe and effective HIV vaccine could help bring about a durable end to the HIV/AIDS pandemic and is particularly needed in southern Africa, where HIV is more pervasive than anywhere else in the world."
The Deductive Approach
Broadly neutralizing antibodies (bNAbs) are potent antibodies that have the ability to block a high percentage of global HIV strains from infecting human cells. These antibodies are detected in the plasma of only about 20% of people living with HIV, and normally only occur after two or more years after contracting the virus, which is too late to rid the individual of HIV infection. However, scientists believe that if a vaccine can somehow stimulate immune system to make bNAbs before they are exposed to HIV, the antibodies might protect those people from contracting HIV. Currently, researchers are identifying, creating, and testing numerous bNAbs in clinical trials.
"An HIV vaccine is within our reach" Dieffenbach concluded optimistically in his presentation as he outlined his vision for the future. Vaccines have been historically the most effective means to prevent and eradicate diseases and thus, developing a safe, affordable, and effective vaccine could prevent HIV infection from uninfected people and ultimately end the HIV pandemic.
While the scientific community is optimistic about the possibility of a vaccine, it's important to be thoughtful about the scientific breakthroughs that continue to increase the health outcomes of people living with HIV as well as prevent people at-risk from HIV from being infected. Antiretroviral drugs for treatment and prevention as well as PrEP for prevention have decreased the chance of transmitting HIV infection.
AIDS United is excited by the possibility of getting closer to the development of an effective HIV vaccine and supports ongoing scientific research that will help treat people living with HIV as well as prevent HIV acquisition in people at-risk for HIV acquisition.