Genetic Engineering of Viruses

00:01 Now, the virology field was revolutionized about 30 years ago by making DNA copies of viral genomes by the recumbinant DNA technology.

00:13 And this allows you to introduce any change into a virus that will-- that makes studying these viruses in the laboratory, making vaccines, making therapeutic products very easy. We call this an infectious DNA clone.

00:27 Whether the virus has a DNA or an RNA genome, its genome can be made into DNA and cloned into a bacteria plasmid which can be grown in bacteria produced in high quantities.

00:38 And then, we can introduce all sorts of changes into it.

00:41 We can make deletion, insertion, substitution, nonsense, or missense mutations to study the virus.

00:46 We can introduce foreign proteins to use the virus as a vector.

00:49 For example, one of the Ebola virus vaccines that's currently being shown to be very successful in West Africa is actually a rabies-like virus with an Ebola protein coding region inserted into it.

01:02 That was made possible by this technology.

01:05 So, you can design any virus that you'd like, within reason, of course.

01:09 You can reconstruct the genome from the sequence, which I'll tell you about in a moment. It's called synthetic virology.

01:17 And because of the power of this technology, a lot of people are worried about it and so, there have been a lot of discussions over whether this is safe or not.

01:27 Now, in this example, we're reconstructing influenza virus from a DNA copy of the RNA virus genome.

01:34 And this, we're showing for simply one of the eight segments.

01:37 You have to do this eight times to get an influenza virus.

01:40 You start with the yellow molecule labeled minus RNA, that's the virus RNA genome.

01:46 You make a double-stranded DNA copy of it, you put it in a plasmid and that plasmid when introduced into cells, will produce both negative-stranded viral RNA as well as plus-stranded mRNA to make proteins.

01:58 So, you put eight of these plasmids into cells, one coding for each of the viral segments and outcomes infectious virus.

02:07 We call this transfection. We introduce a DNA into cells and outcomes virus.

02:13 Let me tell you an interesting news of this technology.

02:16 Back in 1918, there was a huge and very serious outbreak of influenza virus.

02:23 It's often called Spanish flu, although that's not where it originated.

02:27 This outbreak killed millions of people globally, coincided with World War I, so troop movements probably had a lot to do with its spread.

02:38 But we didn't have this virus isolated from this outbreak.

02:41 We didn't isolate influenza virus until 1933.

02:45 So, in the 1990s, investigators determined the sequence of this virus because it had never been isolated.

02:56 They determined the sequence from material that had been obtained from people who died and were frozen in Alaska.

03:06 They opened the grave, they took biopsies of the lungs.

03:09 These people were known to die--have died from influenza virus, and then they extracted enough material to determine the genome sequence.

03:17 They also got more sequence from pathology slides that had been prepared from army recruits who had died of the infection.

03:24 Their lungs had been sectioned and preserved and stored, and we could recover a little bit of sequence from that as well.

03:30 So, the sequence of all eight segments was determined.

03:33 It was built into DNA and the virus was recovered.

03:36 So, we reconstructed the 1918 virus when we never had it before.

03:41 We reconstructed it from the sequence.

03:43 So, this can be done with just about any virus.

03:45 And people have been studying this virus and we've learned a lot about it.

03:48 We've learned many important things and of course, all of these studies are done under high containment because if this virus got out, it could likely be very dangerous.