Despite those advances, many experts agree that there is still significant leeway to be made up if a cure for HIV is to be developed. Efforts to develop an HIV vaccine started in earnest in the 1980’s but up to now there is no vaccine.
The question many people in the world still ask however is, what is it going to take to progress and stride beyond the status quo, where people will not only rely on antiretroviral medications, but will get curative vaccines that can completely eradicate the HIV virus from their bodies.
“The challenge in developing a vaccine against HIV is that the body's immune system is frail when it comes to eliminating the HIV virus. HIV establishes infection rapidly, mutates at a furious rate and attacks the very cells of the immune system that the body uses to defend against viruses. The virus also takes over the genetic material of normal immune system cells, often lying inactive for months or even years. When it is activated, it is too late for an immune response to be of use because the virus has co-opted cells to churn out millions of HIV copies,” explains Dr Samuel Biraro of the Uganda Virus Research Institute.
What has been at issue as well for many scientists embedded in HIV vaccine research is the immune evasion mechanisms of the HIV virus.
“The HIV virus transforms with ease. Even when the immune system recognizes antigens on the virus and produces antibodies against it, the virus changes before those antibodies can do much. That is why existing vaccines against the infection eventually fail; the virus changes and becomes resistant to them. A vaccine will however be needed to fully and sustainably stop HIV from spreading and from killing people,” Biraro adds.
According to the International AIDS Vaccine Initiative, two thirds of all HIV related deaths in 2014 were in sub Saharan Africa.
Doctor Henry Mugerwa, Head of Research at the Joint Clinical Research Center in Sseguku notes that whilst there has been slow progress in developing a workable HIV vaccine, more has been learnt about the virus that can be incorporated into new attempts to eliminate it.
“The science of HIV-vaccine development is challenging, but scientific understanding continues to improve all the time. A number of HIV vaccine trials have had mixed results. In April 2013, one of the latest HIV vaccine studies, known as the HVTN-505 study, which used a weakened cold virus called Ad5 to trigger the immune system to recognize HIV proteins was stopped. It was determined that the vaccine did not prevent HIV infection or reduce the viral load. One of the most successful HIV clinical trials to date has been a US Military HIV Research trial in Thailand in 2009. Known as the RV144 trial, two vaccines were used together: a “prime” (the ALVAC vaccine) and a “boost” (the AIDSVAX B/E vaccine). This combination vaccine was found to be safe and somewhat effective. The combination vaccine lowered the rate of HIV infection by 31 percent compared to a placebo shot,” he says.
Mugerwa adds that whilst a 31 percent reduction is not sufficient for wide use of the vaccine combination, the success allows researchers to study why there was any protective effect at all.
“The study showed that a preventive HIV vaccine is possible. The latest major vaccine trial involves the International AIDS Vaccine Initiative. Patients are being recruited in London, England and Kigali, Rwanda. This trial uses multiple strategies, and carries the hope of many. It will take 2 years to complete,” Mugerwa reveals.
Scientists at present are studying and researching further on the protective immune responses that were stimulated by the Thailand HIV vaccine trial. Trials are now planned to see if an RV144-like regimen will protect against a strain of HIV infection found in South Africa and against HIV acquisition by people at higher risk of exposure.
UNAIDS, which is a United Nations body advocating for the acceleration and comprehensive coordination of global efforts against the HIV/AIDS pandemic, is also working closely with other global stakeholders to gauge the impact of the RV144 regimen in different countries and on different populations. According to UNAIDS, 10% of HIV infections could be averted if the same 31% efficacy was found in people who receive the vaccine. This shows that a modestly effective HIV vaccine could add to the prevention toolbox of partially effective methods, speeding up the decline of the HIV epidemic.
To build further on the success of the RV144 vaccine trails in Thailand, organisations such as the National Institute of Allergy and Infectious Diseases in the United States and the United States Military formed the Pox-Protein Public-Private Private Partnership in 2014. The partnership aims at producing a safe and effective HIV vaccine and furthering the scientific understanding of the immune responses associated with protection against HIV infection. Today, the partnership scientists are working to both improve and prolong the protective effect as seen in the RV144 study by using an extra vaccine boost and alternative adjuvants to increase antibody durability.
Of recent, American scientists have made strides in characterizing and developing powerful neutralizing antibodies that target different HIV strains. The scientists are hoping to design vaccine regimens that stimulate the immune systems of uninfected people to produce body neutralizing anti bodies capable of preventing infection by the majority of HIV strains. That the scientists say could help speed HIV vaccine research.
Scientists have also been trying out different strategies and vaccines such as the Peptide vaccines. These vaccines use small proteins from HIV to trigger an immune response. Other vaccine combinations refered to as prime-boost” combinations have been used one after the other to create stronger immune responses against the HIV virus.