What RNAi (RNA interference) normally does is to silence the expression of genes, not affect the genes themselves. So to treat a virus with it, you design a piece of RNA (easy to do) that will silence a particular gene in the virus and shut that virus down. 

It doesn't have to be anything major. Think of it like pulling loose a small wire on somebody's engine. You don't have to do much to make the car unable to run, but you do have to pick the right wire. So, this piece of RNA is fed to bees, and it will silence whatever gene it is targeted to. If the bees don't even have this gene (the virus gene) it is harmless to them. Except, there may be immune response to the foreign RNA. 

But even this may be good, because the bee immune system will then attack anything with this particular gene sequence including the virus. So in this scenario, the RNA acts like a vaccine. By using a harmless strand of RNA, you may stimulate the immune response against virus.

My main concern was that if the RNA sequence is not carefully designed, you can get "off target" effects which means that the wrong genes may be turned off or even on. Off target effects are a major problem with RNA interference. 

There is some evidence that viruses can in fact affect the genes of their host. But we don't know why this is, and if it is a good or a bad thing. Best case scenario is this: the host (honey bee) has incorporated some foreign genes to obtain protection against them, again similar to getting vaccinated. Worst case scenario is that the virus has inserted code into the host genome to weaken the host defenses in some way.

It has become clear that the treatment itself (RNA in syrup) does not harm bees, and has little in the way of long-term effects either good or bad. Ideally, such a technique would work quickly and not have long term negative effects. If it is cheap enough it can be reapplied as needed. 

The beauty of using RNA is that it is cheap to make, can be recoded as needed to more specifically match the target, and it should break down very quickly, leaving no long term changes. Changing the coding is necessary to target different pathogens (viruses, nosema, even mites) and also, it may need to be adjusted as the pests mutate (viruses can change very quickly to escape cellular immune attacks -- that's why flu virus vaccines have to be updated regularly. 

If viruses can be knocked down in this way, this will be a monumental breakthrough, not just for honey bees, but for crops and even people.

* * *

Non-protein coding RNAs, and in particular small RNAs, were recently revealed as master chief regulators of gene expression in all organisms. Immediately after its discovery, the potent effect of small RNAs has been exploited to specifically downregulate gene expression in a timely controlled manner. Such technology is commonly used in the laboratory but also for bio- medical applications. Indeed, artificially synthesized small RNAs or dsRNA can be introduced exogenously to look for transient and localized effects.

With this study, the possible incidence of RNA contained in the food diet on animal/human health will certainly become an explosive field of investigation. This study also implies precise awareness from biotechnolo- gists who intend to make use of dsRNA, especially in the field of plant protection against pests.

Ingested plant miRNAs regulate gene expression in animals
Cell Research advance online publication 25 October 2011

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