Chronic infections

Miguel Zamora mzamora at
Thu Feb 20 03:52:03 EST 1997

I agree. Excellent topic.

Regarding to human RNA virus infection, there are a number of virus
that can cause persistent infection.  One of them is Poliovirus.  Very
little is known about how the persistant infection originates.  In
some cases poliovirus can follow a different route of infection and
develop a different disease (the well known neurological disease
caused by polio versus the gastrointestinal infection).  However,
there is no data on how this happens and why.  Also, no every person
infected with polio develops a persistant infection.  Is the route
followed by the virus important?  Also, why is virus dormant for many
years and then gets activated? By what?

In the lab, we can get persistant infections with poliovirus but only
with some cell types.  There is some data suggesting some correlations
between specific mutations and the ability to cause persistant
infection, however this is still an open question.  What happens
inside the cell is still a mystery.  In the lab, the infections seems
to procede in the initial stages of the infection as usual, but then
the translation and replication rates drop.  In a normal infection,
the virus causes translation shut off within the first 2-3 hours.  At
least in part, this shut off is due to cleavage of one of the
translation initiation factors (eIF4G) by one of the viral proteases. 
In the case of persistant infections, there is a partial shut off with
cleavage of eIF4G, and then recovery to normal translation rates and
levels of eIF4G.

As I said, nothing is known about the mechanism of persistant
infection at any level, molecular or   clinical.

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