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Author Topic: Can we convert H. pylori into a tool to help with vaccines?  (Read 3940 times)

Offline thedoc

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Australian researchers - Rob Warren and Barry Marshall - won the Nobel Prize for their discovery in the 1980s of the bacterium Helicobacter pylori, which causes ulcers and stomach cancer in some of the people who carry it...
Read a transcript of the interview by clicking here

or Listen to it now or [download as MP3]
« Last Edit: 15/06/2011 11:13:03 by _system »


 

Offline CliffordK

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Can we convert H. pylori into a tool to help with vaccines?
« Reply #1 on: 15/06/2011 21:48:55 »
Interesting idea.

I'm not sure I like the idea of using live bacteria as vectors to deliver viral antigens. 

H Pylori is a very difficult to treat infection, and can have very debilitating, if not lethal consequences. 

Bacteria not only can mutate through replication errors, but they can both pick up environmental genes, as well as sharing genes via plasmids, and thus they can change.

Sometime, someone will make a mistake, and will inadvertently release the next epidemic.

I was thinking about the use of less harmful natural "flora" as a delivery vehicle such as Bacteroides or Lactobacillus, but that would likely mean a higher likelihood that the therapeutic bacteria would escape into the wild.

Perhaps giving an oral dose of staph epidermis, or some other bacteria that doesn't colonize the gut at all, but again one should choose a bacteria vector that would be unlikely to escape into the wild.  Perhaps choose something that colonizes some animals but not humans, but also that humans are frequently exposed to so that they would likely carry a resistance.

In fact, that may be a problem with H Pylori.  The minority of the population would carry a resistance to the bacteria prior to exposure, so those with having prior exposure might have little reaction, and those with prior exposure might have worse reactions, if not risking long-term colonization. 

No matter what, I would encourage designing the bacteria with extreme susceptibility to at least 2 or 3 independent medications.  Perhaps even a custom medication bomb that would be specific to these designer bacteria.  And, it would have to be redundant due to the bacteria's propensity to develop drug resistance.
 

Offline chris

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Can we convert H. pylori into a tool to help with vaccines?
« Reply #2 on: 15/06/2011 22:58:08 »
Did you listen to what Barry said though? He's identifying avirulent, transient-carriage strains that don't persist, so they wouldn't need treating anyway.
 

Offline CliffordK

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Can we convert H. pylori into a tool to help with vaccines?
« Reply #3 on: 16/06/2011 01:05:07 »
Yes,
I read the interview.

And, in most cases it may be self-limiting.  But, is that true in all cases?
  • People who have never had prior exposure to H Pylori, and thus have no prior anti-H Pylori antibodies
  • People who receive the vaccine on a regular basis, every year
  • People who are colonized with H Pylori, and are unable to mount an adequate immune response against it.
  • People with AIDS, or Transplants, or other imuno-deficiencies

"Live" vaccines such as OPV are given to children despite a low incidence of vaccine associated illness.  For a long time, vaccine associated polio was limited in the USA by giving children a couple of doses of IPV followed by a single dose of OPV.  However, the use of live OPV has now been discontinued in both the USA and UK.

OPV is still used in countries that have difficulties giving children multiple doses of IPV.

http://en.wikipedia.org/wiki/Polio_vaccine#Iatrogenic_.28vaccine-induced.29_polio

H Pylori, for the most part is non-lethal, but it has been associated with severe GI problems. 

What happens if the attenuated version is cultured with the wild version (I.E. a carrier person receives the vaccine)?

I certainly support the idea of scientific progress, but I get concerned with the idea of doing wide distribution of live designer pathogens, especially when we have methods to deliver an equally effective vaccine without live bugs.  What we need is a better method to take them from development to distribution, as well as perhaps better storage methods.  Can we make a long-term vaccine storage facility in Antarctica?
 

Offline chris

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Can we convert H. pylori into a tool to help with vaccines?
« Reply #4 on: 19/06/2011 20:36:07 »
Hi Clifford

Regarding polio, the reason that the live (OPV) has been phased out in polio-eliminated countries like the UK and the US is because the live form is infectious (by definition) and leaves the body (via faeces), re-seeding the environment with polio. And because the virus occasionally reverts to type (reverses the disabling mutations that attenuate the vaccine) this poses a difficulty with eradication, because it sustains the presence of wild-type polio in the environment.

Therefore, as we move towards eradication, authorities are switching towards (dead) IPV to prevent this occurrence, except in risk countries where it is prudent to remain with live vaccine for various reasons.

As far as the H. pylori story goes, you ask what happens if a modified H. pylori mixes with a virulent type, there are various ways to disable the bug or to prevent a risky recombination from happening to reduce the danger. However, the research is at any early stage with the first steps being to identify these avirulent strains.

You raise very good points though.

Chris
 

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Can we convert H. pylori into a tool to help with vaccines?
« Reply #4 on: 19/06/2011 20:36:07 »

 

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