One Virus, More Than One Disease: It's All In Your Genes

"Cartoons and Poems following each article are created and copyrighted by Dr. Ackerman and cannot be copied or reproduced without his permission."

What will all those researchers do when we've found out everything there is to know about everything? Don't concern yourself. It's not about to happen very soon. One thing that any good researcher learns pretty soon is that each time a problem appears to be solved, the answers lead to numerous new problems for solving. The same thing seems to happen with bacteria, viruses, and fungi. No sooner do we find a way to kill them then they just change their structure and become resistant. Now we may have a new variation on this theme. It seems that a group led by Michael J. Walter at Washington University School of Medicine has reported that a single virus is capable of producing both the acute form of asthma and the chronic form, but whether the acute form shows up, or not, depends on whether a certain gene is active or not. The virus group is called paramyxovirus. It apparently can cause acute airway inflammation/hyperreactivity. Infection with these viruses causes most of the acute lower respiratory tract illness that we see in young children and infants. This often results in chronic wheezing, but the exact relationship between the long-term effect and the acute illness has not been too clear. In an article that the Washington University group published for the July 2002 issue of the Journal of Clinical Investigation they claimed that paramyxovirus can also be responsible for the chronic airway remodeling/hyperreactivity that may eventually lead to lifelong airway disease such as asthma.

Working with mice they were able to demonstrate that the ICAM-1 gene must be present for the virus to have its full effect. When mice, whose ICAM-1 gene exon 4 has been interrupted (ICAM-null mice), were inoculated with virus the blocking of the gene protected them against airway inflammation after the initial bronchiolitis. Interestingly, however, these mice were not protected against chronic airway hyperreactivity. Just like wild type mice, about 21 days later there was full manifestation of prominent airway epithelial remodeling, which was still present at 77 days. One year after the virus is gone there is still found airway hyperreactivity and goblet cell hyperplasia. On the other hand, mice with fully expressive ICAM-1 gene will experience both the initial acute phase and then the chronic phase. The conclusion is that the virus is capable of inducing a new chronic asthma phenotype. The new type is segregated from the original by the dependence of both on the ICAM-1 gene. If the gene is not active, an acute phase will fail to occur.

One other important finding was discovered when allergic pathways were compared during the testing. There appears to be no direct relationship of this virus induced response and allergy. Allergists have been divided for many years over whether treating asthmatics with allergy injections is of any value. Studies, such as this one, tend to favor the concept that we are dealing with two different etiologies and pathways. Nevertheless, those allergists who favor the use of injection therapy have never really relied on the concept that certain forms of asthma are basically of allergic origin. Rather, the feeling of some has been that those asthmatic patients who test positive for definite allergies will be inclined to superimpose their allergic manifestations upon the underlying chronic airway disease. By reducing this manifestation with appropriate therapy, one layer of irritation is alleviated. Experience over the years has never fully justified one position or the other, at least in the clinical environment.

In the end, it seems that the decision rests with the afflicted individual. A patient who has both asthma, and well demonstrated allergic test reactions must weigh the consequences, and decide whether getting regular allergy injections for years is worth doing from both a time consuming and a financial point of view.

So, what has all this got to do with, "the more you learn, the more there is to learn?" To put it succinctly, now that we know that one virus can cause different manifestations of the same disease in mice who have different variations of a gene, a whole new world of investigation exists, starting with finding out if the same thing applies to humans, looking for other organisms that do similar things, and on and on.

Cartoons and Poems following each article are created and copyrighted by Dr. Ackerman and cannot be copied or reproduced without his permission. Copyright © 2007 by Marvin Ackerman, M.D.

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