The long journey researchers face in finding a cure for HIV/Aids

Saturday December 1 2018

HIV vaccine

Since 2009, it has taken us almost another decade to fully understand barriers to realising an HIV vaccine. FOTOSEARCH 

By ELIZABETH MERAB
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When the then US health secretary Margaret Heckler made a forecast in 1984 that a vaccine would soon be developed for HIV, several scientists seated in the packed auditorium “blanched visibly,” according to Randy Shilts’s And the Band Played On.

And they were right: It had taken 105 years after the discovery of the typhoid bacterium to develop a vaccine for typhoid.

For whooping cough (pertussis) it had taken 89 years; for polio and measles 47 and 42 years respectively.

When it comes to HIV, it took scientists 22 years to realise the modest results from the Thailand trial (RV144) in 2009.

“Since 2009 it has taken us almost another decade to fully understand barriers to realising an HIV vaccine,” said Dr Dismas Oketch, a principal investigator and associate director at Kenya Medical Research Institute (Kemri) HIV Prevention Trials and Linkage to Care Unit.

As the world marks yet another World Aids Day (under the theme, “Know your status” scientists worry that flawed public health strategy, rapidly shifting demography, drug resistance and diminished resources could contribute to HIV’s runaway resurgence.

Dependency on external donors is acute, with the United States responsible for the lion’s share of financing.

Drug resistance

The UNAids-Lancet Commission report estimates that a minimum of $36 billion a year will be required to win the race against rising drug resistance and surging youth populations.

Yet, eight out of 14 donor countries have reduced their support over the past few years, in some cases drastically.

And US funding through the President’s Emergency Plan for Aids Relief (Pepfar) is expected to decline amid cutbacks in foreign aid and global health by the Trump administration.

“Without a doubt, funding remains the stickiest challenge. HIV prevention and treatment guidelines, however, good, cannot progress without a corresponding budget to enable their implementation,” Dr Oketch says.

Moreover, there is a huge number of HIV positive patients — about 15 million — currently not on treatment.

Most are not aware of their status and are unlikely to take precautions such as using condoms during sex to protect others.

Stigma and discrimination still deters people from taking an HIV test, with many people still only get tested after becoming ill and symptomatic.

“The region doesn’t focus on key populations like sex workers, men who have sex with men and young people, who collectively contribute to high numbers of HIV,” said Dr Matilu Mwau, an infectious diseases specialist at Kemri.

New infections are also increasingly showing up in forms that are difficult to treat because the strains of HIV spreading today are more likely to be resistant to available drugs, making it more expensive to manage the disease using second- and third-line treatments.

“Medication is widely available but adherence is a major problem. Some people also do not respond well to some of the treatment,” he further explained.

Proper response

According to Dr Mwau, lack of proper response to the ARVs arises from the fact that every patient is put on one treatment, which at times may lead to drug resistance.

Despite advances in treatment, both a cure and a vaccine for HIV remain elusive.

“There are many great ideas on how to expand the pipeline for HIV treatment and prevention. However, without adequate funding, it becomes difficult to generate new ideas, products and interventions and to deliver proven interventions to those who need them most,” added Dr Oketch.

Dr Oketch said though the question why researchers have not yet found a vaccine remains uppermost on everyone’s mind, he is optimistic that one is around the corner.

Over the nearly four decades since HIV was discovered, a lot has happened in basic biology. Yet, only one vaccine has ever shown evidence of protecting against HIV.

Seven years ago, a vaccine known as RV144 tested in Thailand was found to be about 31 per cent effective, but the effect was considered too low to advance it to common use.

So, is the world inching closer to getting an HIV vaccine?

“We will have a safe and effective HIV vaccine within the next 10 short years,” said Dr Oketch.

But he was quick to temper his optimism by adding: “The biggest scientific barrier has been how to overcome the diversity of HIV-1 with its several strains and new forms that emerge daily.”

HIV-1 is one of the two types of HIV, transmitted through direct contact with HIV-infected body fluids.

“Through research and trials, we have been able to eliminate the items that do not work in vaccine experiments that will soon bear fruitful results,” added Dr Mwau.

Challenges

Inventing a vaccine has proved a challenge for scientists, in part because there are so many strains of the virus and HIV mutates to elude attack from the human immune system.

“An HIV vaccine should stimulate the immune system to deal with ‘free’ virus, the virus that integrates into our genetic make-up and the virus that hides in difficult to reach places like the tested, lymph nodes and the brain,” notes Dr Mwau.

In East Africa, Dr Oketch says, there is an “overwhelming” amount of HIV prevention and treatment research taking place at the moment.

“At any given time, all the major health research organisations in the region are each running more than five HIV research studies. For example, at the Kemri Centre for Global Health Research, we have more than seven major studies with potential global health impact.”

Whereas Dr Mwau said that research, and development of anti-HIV drugs, including pre-exposure prophylaxes seemed provide most people in more optimism towards the fight against HIV, a vaccine may take a little while longer to develop.

“If anything, drugs are proving to be more effective in elimination of HIV they have has helped reduce transmission of new infection,” he says.

Using a new method called the "mosaic" vaccine, the vaccine known as HVTN 702, is undergoing the largest and most advanced clinical trial.

It is a modified version of the only one to have shown a positive effect of many that have gone on trial so far.

So far, there are two key HIV vaccine trials ongoing in South Africa — HVTN 702 and HVTN 705.

“With these two trials, the gaps that were identified in the Thailand trial and previous failed vaccine studies have been specifically and competently addressed,” said Dr Mwau.

Combination treatment with at least three different antiretroviral medicines has led to effective management for many people living with the disease, seeing its overall incidence decline.