HIV Vaccine development is closer than ever before

By Hilary Bainemigisha

Today, we recognize and thank the many volunteers, community members, health professionals, donors, researchers, policymakers, regulators and advocates, who are working together to find a safe and effective preventive HIV vaccine.

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Today, May 18, is World HIV Vaccine Awareness Day. It is a special day because it forms the 30th anniversary since the first HIV vaccine clinical trial opened in Bethesda, Maryland, US in 1987. It has been 30 years of hard dedicated work as researchers sniff around for an HIV vaccine.

Today, we recognize and thank the many volunteers, community members, health professionals, donors, researchers, policymakers, regulators and advocates, who are working together to find a safe and effective preventive HIV vaccine.

This is the day to celebrate their efforts and also to educate communities across the nation about the importance of preventive HIV vaccine research.

Imagine a world where you take a vaccine shot and get protected against HIV infection for ever! Or, for those who already have the virus, you take the vaccine and it stops the virus from breaking you down into the AIDS stage.

That is the target of all this HIV vaccine research effort, a beckon that keeps researchers going. The good news today is that we are more hopeful than ever because, in 2009, researchers achieved a proof-of-concept that a preventive HIV vaccine is possible.

Before 2009, five HIV vaccine trials had failed to show any impact. But in 2009, a trial in Thailand posted a 31% success. It was a major milestone!

Now we know that an HIV vaccine is both possible and essential. Treating people who are infected has done a lot to bend the curve of the epidemic, but a vaccine, when got, will be the final nail in the HIV coffin because vaccines are taken once for long term protection.

Status of HIV vaccine research?

2017 will mark the first year in over a decade that two HIV vaccine efficacy trials are running at the same time. An HIV vaccine efficacy trial is where a vaccine candidate is being tested on thousands of people to see if it works in preventing HIV infection.

In 2009, the Thailand trial called RV144, showed that those who got the trial vaccine were 31% less likely overall to acquire HIV. This was the first time that a vaccine trial in humans showed success.

After that trial, scientists started studying how to improve on the vaccine candidate and to adapt it for use in other parts of the world. This work has led to a new trial, known as HVTN 702, which started at the end of 2016 in South Africa, to test a modified Thai vaccine candidate to work on the HIV subtype (clade) C which is the most common in Southern Africa.

Later in 2017, another efficacy trial, HPX2008/HVTN 705, will start in various countries throughout Sub-Saharan Africa to test a candidate that can work on multiple HIV clades (mosaic immunogen).

Key challenges to an HIV vaccine

The biggest challenge is that the virus mutates rapidly, allowing it to evade the body’s defences. Mutation refers to the way a virus changes its structure of gene to evade attack.

Furthermore, HIV primarily attacks the very cells needed to mount an effective immune response. Most vaccines were developed by learning from the immune response of a person who has successfully eliminated an invading pathogen.

Since no human has ever eliminated HIV with their own immune system, scientists cannot apply that important strategy.

Antibody research

One of the exciting developments in research is the discovery of the body’s Y-shaped proteins produced by B cells (immune cells) which can bind to a specific part of HIV’s surface and block its activity. They are referred to as broadly neutralizing antibodies (bNAbs).

The exciting development may help them understand how to develop a preventive vaccine that would produce such protective bNAbs. And because many bNAbs attach to a relatively small, conserved portion of the virus, known as the envelope trimer, it narrows the target area for vaccine development.

Scientists have also isolated numerous bNAbs from a subset of people living with HIV who have been found to neutralize (render harmless) many different strains of HIV. Because most vaccines induce the production of antibodies against various pathogens, studying the action of bNAbs can inform an HIV vaccine design.

Passive immunisation

Passive immunization refers to the transfer of pre-made antibodies into an individual unlike active immunization where a vaccine is given to teach the body to make its own antibodies by itself. This concept is being studied for bNAbs in two large clinical trials in the Americas and across sub-Saharan Africa, known collectively as the Antibody-Mediated Prevention (AMP) Study.

Researchers are testing the safety and effectiveness of giving a person intravenous drips of a bNAb known as VRC01 for HIV prevention. Results are expected over the next five years.

A growing number of trials are also moving through such stages as lab, animal model and human trials.

Way forward

We now need to work together to ensure as HIV vaccine trials move forward, stakeholders are well-conducted and that research reacts quickly and appropriately to the changing realities of the HIV response. To declare success, a vaccine must be effective, easily available, accessible, affordable and acceptable. To achieve that, we may need over 10 years ahead.

Researchers, advocates, donors, policymakers, regulators, funders and communities must keep up the pressure to ensure an eventual rollout of a safe, effective, licensed and widely accessible HIV vaccine.

The writer is a member of the Vaccine Advocacy Resource Group (VARG)