Christopher Kelly
Search for the Holy Grail
Despite billions of dollars spent and some of the world’s best brains on the case, there is still no vaccine to protect against HIV. But, as Christopher Kelly reports, recent discoveries have recharged researchers’ efforts.
HIV was isolated and identified in 1985. At the time, US health officials voiced confidence that a vaccine would be developed within 24 months. Three decades on and an effective vaccine remains as elusive as the Tasmanian tiger.
In the intervening years, HIV/AIDS has claimed 39 million lives worldwide. Today, around 35 million people are living with HIV and two million are infected every year. Despite advancements in the treatment of HIV and a plethora of prevention tools, an effective vaccine remains the best hope of ending the global epidemic for good.
During the past 30 years, much has been learned about HIV, the immune system and how to design better vaccines. However, to date, there has only been one that has shown to have any promising effect at all.
Known in the trade as RV144, it was found to reduce the risk of acquiring HIV by 31 percent (when creating vaccines, the desired level of protection is between 80-90 percent). Although a modest result, RV144 is nevertheless hailed as a breakthrough and referred to as “a pivotal moment” in vaccine research.
Researchers have adopted a two-pronged approach to developing a vaccine for HIV. They’ve been looking for a protective vaccine that could be administered to the general population, much like the polio inoculation; and a therapeutic vaccine that could suppress the virus to such an extent that someone living with HIV would no longer require treatment.
So why has HIV been giving vaccine researchers such a hard time? Well, because the human immunodeficiency virus is — to use scientific lingo — a cunning bugger. For starters, there are nine subtypes of HIV circulating globally in different populations, and within an individual, there are millions of variants.
As if that wasn’t enough for the white coats to deal with, the virus targets the very cells the immune system triggers to mount a defence. The trick, say scientists, is to destroy the virus before that happens; to kill it while it’s exposed. Sounds good in theory, but HIV rapidly mutates, it constantly shapeshifts to evade detection.
Despite the obstacles, recent scientific discoveries have re-energised the quest for a vaccine. Described as “a vital step” forward, researchers in South Africa have uncovered a weak spot on the outer skin of the HIV cell potentially rendering it vulnerable to attack.
Researchers are also excited by the discovery that some people naturally produce antibodies that control HIV. Called bNAbs, they are currently being studied in clinical trials in the hope that one day they could be used in a vaccine.
In other promising news, two revolutionary vaccines are to be trialled on humans this year. The first — the CMV vaccine — has been shown to create a unique type of immune response in rhesus monkeys. Another, headed by Robert Gallo — the person who co-discovered HIV as the cause of AIDS —is designed to eradicate HIV at the point of infection. It will be some time, however, before we know whether these are viable contenders for an effective vaccine.
As for Australia, researchers from the Kirby and Doherty institutes are joining a worldwide $30-million initiative to accelerate the search for an effective vaccine. “This collaboration will allow us to work with the best people, using the best technologies to build on the enormous scientific progress that has been gleaned over the last few years,” said Professor Sharon Lewin, Director of the Doherty Institute in Melbourne.
Although the search for an HIV vaccine has been ongoing for 30 years, in the scheme of things, it still remains early days. After all, it took scientists more than 100 years to protect people against typhoid. It’s all about baby steps and learning from setbacks. Should scientists ever become disheartened, however, they would do well to remember the words of Thomas Edison: “I have not failed,” he said, “I’ve just found 10,000 ways that won’t work.”
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