I apologize if this has already been covered, but I was wondering:
Since there’s already the low path H5N1 in North America, and it’s been here, it seems, for some time, is there any chance that some people in North America have any sort of immunity to H5N1? Or, would there be no guarantee that low path H5N1 would stay low path if/once it was able to infect humans? Have there been any serological studies done? Any tests on mammals? Does an avian flu virus have to go through many major mutations before it’s able to infect any sort of mammal?
If, let’s say, a small percentage of the human population has been infected at some point with the “low path” H5N1, would it give any advantage if/when high path H5N1 came around?
I’m sorry if this is an ignorant question. It’s just been bouncing around in my head for awhile, and I was wondering if someone could clear it up for me.
Can we somehow take advantage of the low path H5N1 and use it against high path H5N1? Why/how are they so different, and why is it that the low path discoveries seem to be so easily dismissed as far as public health goes? Does the low path H5N1 currently circulating in North America have the potential to become as dangerous as the current high path strains of H5N1?
Thanks for your help!
It will depend on whether there is cross-immunogenicity between the LP and HP forms. If you look at seasonal flu, the reason why we need to make a new vaccine every season is because the HA changes so quickly that last season’s vaccine is no longer protective. I would be very surprised if the HA of H5, in evolving from LP to HP, including the addition of the series of basic amino acids to the cleavage site between HA1 and HA2, the 2 active molecules of the HA antigen, remains stable enough in terms of antigenicity for that to work. Plus we don’t even know whether people have been infected with the LP variety with antibodies, and if so whether there are sufficient numbers for any purpose.
Even if the HA is different, if, theoretically, I had been previously infected with a low path H5N1, would I have any advantage over a person whose immune system had never encountered any sort of H5N1? Or is the HA key for making effective antibodies?
Is the reason H1N1 is not as bad now as opposed to 1918 because the virus has changed, or because the population got used to H1N1? Both? I mean, I assume it must be both, but is one more important than the other, or are they dependent upon each other?
I guess I was hoping we could all go out and hug a bunch of ducks with low path H5N1, so our bodies would get used to it, even if it’s a very distant strain of H5N1 that winds up coming around.
It would be sweet if it were that easy. Hugging ducks. Don’t you think?
o - ps - if you are in Indonesia or China, please don’t go out and hug a bunch of ducks.
If you look at the research attempts to make H5N1 vaccines, the WHO has had to supply multiple vaccine strains because previous strains show no protection against the current circulating ones. That shows you the degree to which the HA changes and the low chance of sufficient cross-immunity being present to make your dream work!
Good try, though. :-)
Thank you for your help! My mind can rest easy now. Or, not. But I understand more better now, so thank you.
KK,
Please also consider the potentially damaging effects of a Low Path strain on your body that may weaken your immune response to the later HP H5N1.
NS1 – at 19:11 a little off topic but I wanted to ask you about the 15 year girl in Indo. Her brothers died of H5N1, and she was not found H5 positive but was H1 positive. Can H5N1 and H1N1 exchange genetic material (easily)? Thought you would be the one here to ask.
NS1 - how would it weaken the immune response to HP H5N1? Do you mean because the body wouldn’t totally freak out, cytokine storm-style? Wouldn’t that be good, unless you were very young, very old, or otherwise sick? Or is there some other reason why a prior LP H5N1 infection would be disadvantageous when it comes to HP H5N1?
Being infected with both at the same time would be a bad thing, right? As in Effect Measure’s 9/19/06 post re: moderation of virulence?
“In other words, many strains are co-circulating and the virulence of even the lowest of them is higher than would occur if superinfection weren’t possible.”
Superinfection, I think, means infection with more than one strain.
So, the more strains of H5N1 does not equal the merrier, at least as far as hosts are concerned. Right? Does this have anything to do with why prior LP H5N1 might not be a good thing?
Thanks again for your good brains and good words.
Dennis,
Many occassions are on record of H1Nx and H5Nx sharing genetic material via reassortment and recombination.
kk-
In my opinion, a weak immune system is never a benefit. I believe that we are distantly off-base in any conversation that makes the half-dozen logic jumps to come to the conclusion that a weakened immune system will assist against H5N1.
Dual infection only means that the potential for genetic acquistion exists.
Proximity = Opportunity.
Sometimes the bandit jumps on your train car and takes all the watches and jewelry and other times a nurse boards the train car just in time to assist the delivering mother.
We can’t always predict the potential exchanges . . . unless your name is Dr. Henry Niman.
An he’s onto a system of rules that I wish he could share with us sooner rather than later.
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