T-cell vaccines are a comparatively new approach to steering the immune system to perform tasks normally left undone, such as clearing out persistent herpesviruses. It is a reminder that the heading of immune therapy covers a very wide range of possible technologies, not all of which are even on the drawing board yet, and it will be an important part of the longevity science toolkit in the years to come.
An introduction to T-cell vaccine research can be found at the Technology Review:
All existing vaccines rouse the body into creating antibodies that attach to the surface of infecting microbes and flag them for destruction. But pathogens that live inside our cells, such as the viruses, bacteria, and other microbes that cause AIDS, malaria, herpes, and chlamydia, can evade this surveillance. ... In order to deal with those types of pathogens, oftentimes we have to stimulate what we call cellular immunity. Unlike antibody immunity, which recognizes pathogens directly, cellular immunity has to recognize the infected cell and get rid of your own infected cells.
But activating cellular immunity - and the family of infection-fighting cells known as T cells that drive it - is challenging. The trial-and-error method used to develop antibody-based vaccines has not worked for T-cell vaccines. Despite years of academic and industry work, and even clinical trials, there are no T-cell vaccines for infectious disease on the market.
A Cambridge, Massachusetts, biotech company called Genocea thinks its high-throughput method could change that. The company will begin its first clinical trial later this year, when its experimental herpes vaccine will be the first test of its claims.
The first and most straightforward way in which a working T-cell vaccine platform might be used to extend life expectancy is as a therapy to clear out the common herpesvirus known as cytomegalovirus (CMV). Most of the population carries strains of CMV by the time they reach old age, and it is thought that CMV plays a role in progressive immune system disarray:
Most people are exposed to this mild persistent herpesvirus over the course of their life; it causes few obvious symptoms, but over time more and more of your immune system resources become uselessly specialized to fight it. An immune cell dedicated to remembering the signature of CMV is unavailable for other uses - and eventually you run out of cells to protect you from new threats, destroy cancers, and clear out senescent cells. This process is one part of the frailty and increased risk of death and disease that comes with old age.
But there are other many other potential uses as well. A more mature T-cell vaccine platform could lead to an array of targeted cell destruction therapies. Destroying cells is, after all, one of the tasks that immune cells have evolved to carry out. A way of rapidly generating new, reliable, and selective methods to destroy very specific cell populations will be helpful in a very wide range of therapies designed to hold back the depredations of aging. For example, such a therapy might be used to cull the unwanted cells that clog up the immune system and degrade its effectiveness - including the memory cells uselessly devoted to persistent CMV strains.
Equally there are cancer cells, senescent cells (if researchers can figure out a better way of reliably identifying them from their surface chemistry), and all sorts of other cells we'd be better off without. Destroying them will repair some of the harms of aging caused by their presence. The most cost-effective way to get rid of them all is via some form of versatile technology that can be quickly adapted to new targets - and it's a fair bet that the first forms of that technology will involve learning how to manipulate the immune system to get the job done. Why reinvent the wheel when you can use what already exists?