Ebola, _POSSIBLE_ international outbreak

[David P. Frazier]

In article <mckinley.185.0017A0FF at msupa.pa.msu.edu>,
mckinley at msupa.pa.msu.edu (James T. McKinley) wrote:

> Given that Ebola Reston is so close to Ebola Zaire that they are difficult to 
> tell apart, and that Ebola Reston is apparently harmless in humans, would it 
> be possible to use Ebola Reston as a vaccine for Ebola Zaire?  I know it
would 
> be hard to test since Ebola Reston kills monkeys just like Ebola Zaire,
but if 
> it really came down to it, might it work?  Has nature provided us with a
ready 
> defense against this nasty thing?  I believe 4 humans tested positive for 
> Ebola Reston with no ill effects; one even cut his thumb with a scalpel 
> covered with monkey blood infected with Ebola Reston and never even got a 
> sniffle.
> 
>                                                                     Jim

The short answer to your question is yes, the Ebola Reston strain would be
a good place to start looking for an attenuated vaccine.  Unfortunately, the
reality of making this strain into a safe and effective vaccine is
currently nearly impossible.  The first problem is a lack of a suitable
animal model to test for efficacy of this strain as a vaccine.  We don't
know that a robust 
immune response to Reston would necessarily protect against Zaire.  I'm not
even sure whether anyone knows if a robust response against Zaire is protective
against future infection.  Since Reston kills monkeys it clearly can't be tested
in these animals.  Infecting humans with Reston for research purposes is out
of the question since we have no idea whether the four who were infected were
simply lucky that they didn't become ill or if the virus is truely
harmless (not to mention the potential for mutation of the vaccine strain
back to virulence).
So the best bet for developing a vaccine against Ebola is to study
individual viral proteins which could elicit a protective immune response
and be used in
a recombinant vaccine.  Scientific issues aside, considering the number of
actual cases of Ebola in the world, devolpment of a vaccine for this agent 
is not really a priority.

David P. Frazier
Department of Microbiology and Molecular Genetics
Harvard Medical School