In the fight against HIV, knowing what to target in the first place is harder than it seems.
In the early 90s, at the height of the HIV/AIDS epidemic, scientists fervently believed that a type of immune system cell, called T-cells, were our first line of defense against the virus. This belief formed the basis of HIV research for years to come.
Now, thanks to advances in technology and newfound knowledge, we know our immune response to disease is far more complex than once thought.
Dr. James Crowe MD, Director of the Vanderbilt Vaccine Center, has spent years looking at a special group of people who seem more resistant to the HIV than others. These ‘controllers’, or ‘non-progressors’ as they are sometimes called, are helping scientists more than ever before to discover how the body reacts to HIV.
“We are trying to use studies of the human immune response to HIV in order to understand the principles of immunity,” said Dr. Crowe. “If we could understand the rules of how to neutralize or clear HIV, then we could better design vaccines or new therapies.”
By picking apart their immune responses with the latest research techniques, he is getting closer than ever to finding out what makes them special, and how we can use their unique immune response to reach the holy grail of HIV research: a vaccine.
Much of what Dr. Crowe and his team aim to do is chart the body’s response to HIV, right from the very first point of infection. This is a huge challenge, considering the technology to look at humans’ immune response in detail has not been around for very long.
“We take blood cells from HIV infected people, particularly those who are able to control their infections,” he added. “These individuals have been infected for a long time but are able to control the virus at low levels, so there may be clues in their immune response as to how to resist HIV. We’re studying antibodies made by these individuals.”
Antibodies, the protective molecules made by the immune system to mark foreign bodies for destruction, normally do a stellar job of eliminating viruses from the body. But HIV’s trick is to target and destroy the body’s immune cells, lowering its hosts’ immunity to such a degree that they develop AIDS (Acquired Immune Deficiency Syndrome). This leaves them susceptible to a whole host of potentially lethal infections that are normally fought off with ease.
There are cohorts of HIV controllers who have been followed for around twenty years now. There are various reasons that have been discovered for why some of them are relatively resistant. “It’s actually not clear that their immune response is always the principal driving force,” said Dr. Crowe. “Sometimes there are genetic factors involved. But these individuals have been infected for quite a long time, so their immune systems have had the opportunity to ‘see’ HIV for a long time and therefore make very interesting antibodies.”
The way Dr. Crowe separates antibodies for examination is a complex process involving several cutting-edge technologies designed to isolate, purify, and grow batches of individual types of cell. “A subset of our immune cells, called B cells, are the ones that make antibodies,” he said. “So we are able to capture and immortalize individual B cells that secrete antibodies. And then we find the ones, sort of the needles in a haystack, in the mixture of cells, that are specific to HIV.”
The purification technologies that Dr. Crowe’s lab uses are the result of decades of evolution. They use purification columns, chromatography media and buffer kits developed by GE Healthcare’s Life Sciences division to pick apart the components of our immune response to HIV and help create antibodies that could one day lead to new therapies.
Dr. Crowe’s lab has been collecting hundreds of these special B cells over time, and they can now make entire batches of cells that produce a single type of antibody.
“That’s where the more specific work really starts,” said Dr. Crowe. “Then we can figure out how each antibody recognizes an HIV molecule, how many HIV strains it can recognize, and whether or not it kills the virus.”
In decades past, this kind of work was done using mouse antibodies, as the technology to make human ones was not yet so refined. “I think over the last twenty years or so, various academic or industrial groups have evolved methods for making human antibodies… and we have one of the most efficient ones. It’s been working for five or ten years at this level,” added Dr. Crowe.
“We take those purified monoclonal antibodies into a biosafety level 3 laboratory where we can work with live HIV. We mix the antibodies with the HIV, and let them incubate for an hour or so. Then we see if the virus can still replicate in cells, and if the antibodies inhibit the replication of the virus… that’s a process called neutralization, and that’s the function we’re looking for.”
“That’s the moment of truth: when we know if these antibodies are really potentially useful.”
Leading up to World AIDS Day on December 1, The Pulse is taking a close look at the pioneering work of three leading scientists, pushing the boundaries of science to find a cure. Stay tuned to learn about how Dr. Hope is shedding light on HIV from every angle, and how Dr. Spearman is working to find the weak spot that will stop HIV dead in its tracks.