DEAR DOCTOR K:
I heard on television about a possible new vaccine against HIV, Ebola and other terrible viruses. That sounds like very good news, or is it just hype?
You may well have heard about a new approach to creating vaccines. The approach is called “passive immunization with neutralizing antibodies.” It could revolutionize immunization against Ebola and other viruses, including HIV (the virus that causes AIDS) and influenza (flu) viruses.
To tell you what it is, and why this new approach is exciting, I need to explain some basics first. In tomorrow’s column, I’ll explain neutralizing antibodies.
When we are infected by viruses (and other microbes), certain cells of our immune system catch a few of the viruses. These cells chop the microbes they’ve caught into little pieces. Then those cells display the pieces, called antigens, like little flags waving from their cell surface.
Some other types of immune system cells see those antigens and begin making antibodies against them. The antibodies attach to those antigens — and to any virus that contains those flags. When that happens, the antibodies disable the virus.
Traditional vaccines contain large amounts of antigens of a virus. When those antigens enter your body, the immune system dedicates certain immune cells to make antibodies against those antigens. The antibodies are made whenever a virus with those antigens infects your body, because those immune cells have a “memory” of the antigens that recognizes them immediately.
So far, so good. But here’s the problem. Some viruses frequently change the shape of certain antigens. The flu virus is a prime example. Often new strains of the flu virus, with new and different antigens, suddenly emerge. No immune cells immediately recognize the new antigens, because the immune system has no memory of them.
This can lead to pandemics — when new flu viruses develop and suddenly sweep across the globe. For example, the pandemic of the H1N1 “swine” flu virus in 2009-2010 swept over the entire world within a few months. That’s too fast for a conventional vaccine to be made in large quantities. I know from personal experience: I caught the H1N1 virus and became quite sick before a vaccine against it could be developed.
With Ebola, there’s a slightly different problem. There are several very different strains of the Ebola virus. Every now and then, for reasons we don’t understand, one of the strains of the virus starts an epidemic. Each of them is different enough from the others that it hasn’t seemed possible to make a traditional vaccine that would cover all three.
So, scientists have long dreamed of a vaccine that: (1) would be effective against many different strains of a virus; and (2) could be made in large amounts and stored to be ready for when an epidemic suddenly explodes on the scene, hopefully nipping the epidemic in the bud. Passive immunization with neutralizing antibodies may prove to fulfill that dream, as I’ll describe tomorrow.