A Conservative View of Cytomegalovirus and Immune System Aging

Cytomegalovirus (CMV) is a herpesvirus that infects most of the population by the time they are old. Like all similar species of virus, it can remain latent in the body for long periods of time, and the immune system struggles to clear it. CMV infection appears to be an important factor in the age-related failure of the adaptive immune system: more and more naive T cells become uselessly specialized memory cells to fight CMV, leaving ever fewer T cells able to perform other vital tasks - such as destroying senescent cells, invading pathogens, and cancerous cells.

I noticed an open access paper that provides a cautious, conservative overview of where researchers stand in their investigations of CMV and immune system dysfunction in the aged. In short, these researchers believe that the damaging consequences of CMV infection are a theory in need of further proof. Additionally, there may be other significant sources of immune cell depletion that operate in the same way, and which may ultimately be shown to be more important:

Despite the widespread belief that decreased numbers of naive cells in the elderly must be a bad thing, and the certainty that CMV infection drives down the numbers of such cells even further, whether this parameter is actually associated with a measured clinical outcome has not been properly tested in humans.

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If CMV has such an over-riding effect on immune signatures, are there likely to be any additive effects of other viruses, pathogens or different sources of "chronic antigenic stress". There is some evidence that [Epstein-Barr virus] has a minimal effect in addition to CMV, but that [other herpesvirus strains] do not. In other conditions such as rheumatoid arthritis, Alzheimer's Disease, and prostate cancer, there is some evidence consistent with CMV exacerbation; the same may be true of serious psychological stress. Evidence is sparse, but what is there suggests that there may indeed be additive immune "exhausting" effects of polypathologies.

Finding ways to clear CMV from the body doesn't solve the problem of a damaged immune system - removing CMV just stops further damage from occurring. In fact, if researchers focused on finding a way to repair and reverse this sort of immune system misconfiguration, CMV could be largely ignored in the general populace. Aside from its effects over the very long term, it is mostly harmless for anyone with a functional immune system.

In recent years, researchers have demonstrated the ability to remove autoimmune disorders - another form of immune system misconfiguration - by destroying a patient's immune system and then recreating it using stem cell technologies. As a process, this is presently crude and traumatic, as it involves the use of chemotherapy or similar approaches. It is not a therapy anyone would wish to undertake, given an alternative. The precisely targeted cell killing technologies under development in the cancer research community may soon offer that alternative, however. If the problems in a malfunctioning immune system involve too many T cells of a distinct type - e.g. specialized to cytomegalovirus - then a targeted therapy could be used to safely destroy those cells.

Comments

I recently had CMV and had bone marrow suppression, swelling, coughing, and exhaustion. I was 67 and went through a very traumatic time and I believe the stress brought it on. Before I had CMV I had amnesia, but am generally very healthy and active and take good care of myself. Does this event of cmv lower my life span or make it more likely I will get cancer or another disease? I would really appreciate more information.

Posted by: Judy Duke at September 8th, 2013 4:24 PM
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