Having read Dr. Pappas's contribution regarding fitness, I realized that
Eric's original question is rapidly being degraded. I too, learned that
virulence is synonamous with poor adaptation. But the redirection of the
thought process that was presented at the meetings in Ft. Collins, dealt
specifically with virulence. This, to my mind indicated that the
question now was can increased virulence be considered a trait upon which
natural selection can operate. I preface my subsequent remarks by saying
that I accept virtually all of Darwinian evolution. However, we choose
to use our logical minds to decide what the traits are that lead to
survival, frame our experiments, and go on with life. Virulence seems to
be reasonable trait given the way it was presented at ASP. That said,
part of Peter Pappas's arguments are quite valid. What is the effect of
increased (a relative term) virulence on reproductive outcome. If
predators of a host are given more opportunities because of a highly
virulent infection, then surely, a highly virulent organism could be said
to be successful. Each host parasite relationship should be considered
in its entirity.
When I worked with Dr. Paul Beaver, he believed that a parasite
could almost will a given histopathological response or put another way,
the parasite is happier in a mononuclear cell-rich granulomatous response
than say surrounded by fibroblasts. At the time I tolerated his beliefs
out of admiration. Now as work with Th1 and Th2 T cell subsets expands,
it is beginning to look like there was more than a grain of truth to what
Dr. Beaver believed. One subset (Th1) seems to favor resistance and all
of the associated cellular responses necessary to go with it. The other
subset (Th2) favors susceptibility. The big question today is, what
property of the host-parasite interaction determines whether the
resulting encounter goes to Th1 or to Th2. It could well be argued that
the parasite which is more virulent can manipulate the outcome or
alternatively, live with the outcome.
Others thoughts?
Steve
================================= :<) ===============================
/\ /\/ /######\ /#######\ Stephen G. Kayes, Ph.D.
/\/ /\/ / / / Structural & Cellular Biology
/\/ /\/ / / / University of South Alabama
/\/ /\/ /######/ /########/ Mobile AL 36688
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The fact that an ostrich has wings, has nothing to do with its
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