Re: Does the 'Hayflick limit' apply to viruses as well as cells?

Before I answer your question, I would like to give you a little more information about the Hayflick limit:

Leonard Hayflick discovered that normal cells could grow indefinitely outside the organism when supplied with necessary nutrients. In a classic 1961 paper (Experimental Cell Research, 25:585-621), Hayflick and Paul Moorhead discovered that cultured human cells die after undergoing about 50 divisions.

Even though Hayflick’s discovery hit the press in 1961, almost 40 years ago, we still don’t fully understand cellular aging, or why cells die after a certain amount of time in culture (possibly because of accumulating mutations). In addition, it is not clear that cells in culture are a good model for aging of the organism.

For some information on the Hayflick limit and aging, and cell growth see: http://www.idahonews.com/071298/DISCOVER/22195.htm
http://ntri.tamuk.edu/class/ksign00/celcntr.html

An especially useful site: http://unisci.com/stories/19992/0514991.htm
describes how mammalian cells, including human cells, can escape the "Hayflick limit" and continue to divide. Many cancer cells do not die in culture after the 50 divisions. These cells can (theoretically) be propagated indefinitely.

VIRUSES are not subject to the Hayflick limit. In order to be subject to the Hayflick limit, the entity must be alive.

A virus requires a living cell for reproduction, and cannot reproduce by itself. The DNA or RNA from the virus is used by the infected cell, and makes new virus proteins. A virus is basically a program for making more viruses. It is just software. It doesn’t contain any of the machinery or hardware, if you will, to replicate itself.

Viruses are also unable to respond to their environment in any way. For example, they can not respond to a temperature change by warming themselves. They do not get hungry, and can not metabolize foods.

For a great resource on viruses and life see: http://www.biology.arizona.edu/cell_bio/tutorials/pev/main.html

The cells viruses infect may be subject to a Hayflick limit, or they may not be. Some viruses, such as the tumor virus SV-40 are often used to prolong, or immortalize the lives of cells in culture. These immortalized cells can be propagated for many years.