In article <Bk28wW7.ksturts at delphi.com> Keith Sturts <ksturts at delphi.com> writes:
>Can anyone explain to a layman what the pathology mechanism is that
>creates 'symptoms' of virus invasion?
It sort of depends on how much molecular detail you're after.
Rarely is it known in great detail exactly why a cell is killed. At the
level of the host, there are many, many overlapping causes for the
symptoms one sees. Here are a few:
(1) Cell death. In general, cells infected with a virus ultimately
die. There are exceptions, but they are the minority. The cause of the
cell death can range from direct lysis by the virus during the egress
process; inhibition of vital cell processes - eg a recent paper shows
that polioviruses block glycosylation; diversion of normal cell
processes to the process of viral replication and translation; apoptosis;
and so on.
(2) Immune response to the virus. Very often the first symptoms of a
viral infection are not due to the virus, per se, but to the host
response to the virus. If, for example, you give a person a small dose
of interferon - or many other cytokines - you get a syndrome that looks a
lot like "the flu". The symptoms of a cold are primarily those of the
body's response to the virus. This also includes misdirected immune
responses, as for instance the non-neutralizing antibody response which
causes many problems in feline infectious peritonitis.
(3) A combination of 1 and 2. Specific cytotoxic lymphocytes often
destroy virus-infected cells.
(4) A more general perturbation of homeostasis. A broad category that
could include things like the warts induced by papillomaviruses, the
downregulation of the epidermal growth factor receptor caused by
adenoviruses, the various soluble receptor analogues expressed by
poxviruses, tumours, the cytokine homologues expressed by a number of
herpesviruses, etc etc.
The question is a good one, but it's almost impossible to answer in any
detail for viruses in general. There are too many possibilities. E mail
me if you have more specific questions.
Ian York (york at mbcrr.harvard.edu)
Dana-Farber Cancer Institute, 44 Binney St., Boston MA 02115
Phone (617)-632-3921 Fax (617)-632-2627