ENDNG THE EPIDEMIC
World AIDS Day events focus on 'getting to zerp.'
World AIDS Day, Dec. 1, features the slogan “Getting to zero: zero new HIV infections, zero discrimination, zero AIDS related deaths” for the years 2011 through 2015.
While it is unlikely the “zero” goal will be reached by 2015, three decades of HIV analysis has sparked a “renaissance” of medical research that is leading scientists in new directions in their search for an effective vaccine.
Dr. Wayne Koff, the chief scientific officer for the International AIDS Vaccine Initiative, started researching HIV shortly after the first cases began appearing some 30 years ago.
“We’ve seen in the last three or four years a plethora of data that we in the AIDS vaccine development field are calling a renaissance, and as someone who has been in the field since the beginning I don’t use that term lightly,” Koff said.
It took almost 20 years of research to get AIDSVAX, the first potential vaccine, into human testing in 2003. While that vaccine didn’t reduce viral load, Koff said it was important because “it proved that we could safely conduct an HIV human efficacy trial.”
That trial eventually paved the way for the 2009 Merck RV144 trial in Thailand. That study included more than 16,000 participants studied over a course of six years.
“In a surprise to many of us in the field, this showed a modest efficacy of 31 percent when compared to control group,” Koff said. “While that wouldn’t result in a workable vaccine because the efficacy was only 31 percent, it did show that a vaccine was possible, and there have been several studies examining why that vaccine was effective.”
According to the International AIDS Vaccine Initiative there are at least 37 different vaccine trails currently underway across the globe, each exploring different potential cures, and each providing key information in the search for an effective vaccine.
Koff said that in order to make a product that could be given to the public, a vaccine would have to be at least 50 percent effective in testing. For example, the Centers for Disease Control & Prevention estimates that the yearly flu vaccines have efficacy rates of around 50 to 70 percent.
‘Different virus in each person’
Finding a vaccine for HIV has proven so difficult in part because of the nature of the virus. Because of its ability to change, HIV has required a new approach.
“Because this virus mutates so much we can’t just use the old form of using a weakened form of the virus,” Koff said. “The measles vaccine that’s licensed is just a weakened form of measles. The licensed polio vaccine is a weakened version of polio, but HIV is a crafty virus… and we learned a long time ago that you can’t just take a weakened version of HIV.”
Viruses are non-living pieces of proteins wrapped around either DNA or RNA. Viruses cannot reproduce on their own, and so they invade cells and take over the cell’s machinery to make copies of themselves, which often destroys the cell in the process. Because HIV is an RNA virus it has been especially difficult to treat.
“It is an RNA virus which is prone to making mistakes, unlike DNA. If it makes too many mistakes then it stops being HIV, but if it makes a standard amount of mistakes that RNA replication typically makes, it changes the amino acids, and makes a different virus,” Koff said. “HIV is different across the world, and the isolates are very different in each individual. It’s essentially a different virus in each person.”
Because of that, researchers have different ways to stop the virus, and many of the vaccine candidates target the protein capsule that carries the DNA. Koff said researchers are finding more sites on HIV that are unique to that virus and can be blocked by broadly neutralizing antibodies.
Think of a lock and a key, Koff said. If you have a molecule of a T-Cell, that part is only going to go into a receptor on HIV. If researches can bind that site and keep that virus from infecting the cell, the spread of HIV in the body can effectively be stopped, Koff explained.
Human trials under way
Another factor that makes the virus more deadly is that it infects T-Cells, a type of white blood cell that is a critical link in the body’s immune system. Attacking the T-Cells and using them as a host helps allow the virus to spread, and leaves the body open to secondary infections.
A former Emory University researcher, Dr. Hariett Robinson has been exploring a multistage attack that she thinks could result in a vaccine that could not only keep people from being infected, but reduce the viral load in people who are already HIV positive.
Robinson has worked on the vaccine for over a decade and has moved to GeoVax, a private company dedicated to making a vaccine, where she serves as chief scientific officer.
Her vaccine consists of DNA modified to prime an immune response and an inert virus that could boost an immune response.
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