Well, an interesting and perhaps educational question for our
viewers at home ;-). You're right in the basic premise, Ron: a vaccine
is usually (without getting too technical) either a killed but
immunologically active viral preparation, or a severely weakened
'crippled' form of the virus in question. Expose to this nonpathogenic
species allows for the clonal selection and proliferation of
epitope-specific B cells, production of memory B cells, and clonal
expansion of epitope specific T cells. All of this basically boils down
to letting the immune system 'see' the pathogen and allowing it to
customize its defensive repertoire against future infections with the
same agent (or at least ones with the same epitopes). {Note: my
apologies to the immunologists on here for the gross oversimplification!}
Anyhow...the theory at this point goes (1) Ebola is a pretty
nasty virus; (2) A few people were exposed to Ebola Reston strain and did
not die a gruesome haemorhagic-fever death; (3) Why not go innoculate
people with Ebola Reston as a vaccine? Problem solved.....
Hmmmmm. Well, let's take a few basic facts in mind. Ebola has a
small RNA genome, coding for a handful of proteins of which (in my non-Ebola
specialist understanding) we can only assign definite functions to a
few. Due to the difficulties in dealing with a Level 4 pathogen, the
virus and its 'lifecycle' are really not very well understood. Sound
like a bunch of technical mumbo-jumbo? Well, the translation of the
preceeding sentances would be "Ebola is poorly understood. We don't know
what is responsible for the virulence or cytotoxicity. We are not really
sure what the important differences between the Reston and other strains
are. Worst of all, the virus is prone to a rapid mutation rate (a
conseqence of having an RNA genome)."
So......now who's up for injection with Ebola Reston? We think
(but aren't sure because we have really no data) that it may have a
preventative effect. We think it won't kill you (but we're not sure of
that, either...we really would need to see hundreds of cases of people
infected harmlessly with it to have any confidence in THAT statement!).
Oh yeah, and it's about 98% identical with the strains that kill you in
one of the quickest and most gruesome ways imaginable...and mutates
quickly. Well, MAYBE it won't mutate to a super-virulent strain in
you...hey, stop squirming, how am I supposed to innoculate you with your
arm flailing about like that? Nurse! Stop that guy who just ran out of
here..he didn't get his vaccination! <sound of smashing glass as
patient/victim hurls himself through the 4th story window to escape the
mad doctor with a syringe full of Reston....patient/victim rightly
assumes this mode of exit is safer than the injection...>.
Make a little more sense now? I'm sure that if anyone wanted to
volunteer for innoculation with Reston followed by exposure to one of the
other strains, we'd be happy to gather some real data...strange, but I
don't hear any volunteers... :-)
Now, this isn't to say it's all a bad idea. The basic premise
DOES have a lot of promise, and I'm sure the lurking Filoviridae people
on here are doing research on exactly that sort of thing. If we knew
what made Reston nonpathogenic, and how to KEEP it that way, it might
make sense to try as a vaccine. It would probably just be simpler,
though, to clone and express a noncytotoxic epitope from the virus and
use that as a vaccine...again, though, we have the problem of who's going
to volunteer to have the vaccine tested on them.
Well, I hope this answers your question. Remeber, folks, don't
try this at home. We now return to our normally scheduled program (adds
for pyramid schemes, conspiracy theories, and flaming...)
Resuming LURK mode <shimmer......blink!>
John Brunstein
Dept. of Biochemistry and Molecular Biology
University of British Columbia
On Mon, 1 Jan
1996 RGALLA41 at MAINE.MAINE.EDU wrote:
> I am sure someone has thought of this before... but why couldn't Ebola Reston
> be used as a vaccine for Ebola Zaire and Sudan?
>> -Ron
>>>
