5.6 Michael Emerman — Host-virus Co-evolution

Michael Emerman: [00:00:00] Thank you. It's an honor to speak at this meeting. My assigned task is to talk about HIV-host coevolution. This is the HIV retrovirus life cycle. The idea is that there are these numbers of restriction factors that block various stages of the life cycle. They are viral antagonists that prevent these restrictions factors from blocking [00:00:30] that. That sets up this virus-host arms race over evolutionary history. We've used this arms race to understand cross species transmissions, to understand how HIV adapted to humans, how HIV came to be from SIVcpz, and how [SIV]cpz came to be from other viruses in terms of adaptation. We learned a lot about virus-host biology by doing this [00:01:00] approach.

Before I get there, I'm going to take a step back, and I'm not the first one to show a picture of Howard Temin (1934–1994) at this meeting. John Coffin was student number two, I was student number 10. I learned how to do science from Howard Temin, among other things, I learned how to develop hypotheses of the type X means Y means Z. How they design the simple as possible experiment to answer [00:01:30] the question at hand. How to read, how to look at other people's data and make up my own mind what it meant no matter what they said. And I learned a lot about retroviruses. This was during the time—I was a graduate student during the time 1981 to 1986, so that was the period where AIDS was first described, when HIV—the virus that known to be HIV was [00:02:00] discovered. I worked on using developing retroviral vectors to understand normal gene regulation. I realized that I wasn't interested in viruses as tools, and I wasn't interested in viruses as models. I was more than student in viruses as pathogens. And even though I was student in a small town in the Midwest. There are a lot of virologists in [University of Wisconsin-Madison], and [00:02:30] there was a lot of interest in the potential viral etiology of AIDS and a lot of interest in HIV in general then, and I became the lab HIV expert.

Sometime during this period, Luc Montagnier called Howard Temin and said he was going to be in the neighborhood, and could he stop by and be in the seminar. Turned out he was actually in Milwaukee, but he took the Greyhound bus to [00:03:00] Madison, and me and another postdoc where assigned and go pick him up the bus station. I think on the way to the lab, I asked him if I could do a postdoc on his lab. Then later that day he said, "Sure." I went from Madison to Paris, and this is me with Luc Montagnier. It was great to be an American in Paris. And to be an American to Pasteur [Institute], because I spoke and I wrote [00:03:30] English very well. I will say, I was a very fast editor. Even though many people there didn't talk to each other, they all talked to me because they gave me their papers to edit. I re-wrote a lot of papers. I wrote a lot of letters to Ben Lewin [chuckles] I knew what everybody is doing, and when it was convenient for me, I can pretend I didn't speak French. Luc Montagnier left us alone and let us do what [00:04:00] we wanted.

We published this—when I first I went there was when we first had cloned HIV-2, we started to work on that. (1, 2, 3, 4, 5) We did functional studies with HIV-2, we did studies with vpx. We made use of HIV envelope. We did some first studies on rev. You should notice Luc Montagnier is actually, we should put him somewhere in the middle. [00:04:30] Sometimes we didn't put in there at all and he seemed to be fine with that. I knew that I had gone native because when we published the rev paper in cell, one of the reviewers suggest that we have a native English speaker correct the paper for us. [laughs]

Then I went to Seattle so this is a picture of the Fred Hutch. One of the great things about the Fred Hutch is that it's a very, very collaborative place. [00:05:00] One of the divisions I'm in, the division of basic sciences is known for these faculty retreats we have, where people just get up and talk about stuff they think is interesting and they are going to work or think they're going to work on. Everybody else gives them lots of ideas. What I was interested in were these accessory genes. This is an old slide I have of the genome of HIV-1 and of HIV-2 and these little [00:05:30] open reading frames were called accessory genes because you can knock them out and sometimes they didn't do anything. The idea that I had was these were the most interesting ones because these were the ones which are going to be important in vivo, and they were likely to be things that interacted with DNA [unintelligible 00:05:46]

That had been born out by the first one of these interactions to be discovered, which what Mike Malim talked about, which was vif, and then APOBEC. I gave a talk about the idea that all of these accessory [00:06:00] genes were going to be interacting with host factors, and I talked about the species specificity which had been known by then. There was a new faculty member Harmit Malik who immediately came up with idea of using genetic conflict to understand these factors. Harmit studied genetic conflict, which is two entities trying to evolve from each other. He studied it mostly in the context of [00:06:30] histones. He was looking for systems where you had both sides of the players. His very first postdoc was Sara Sawyer, who was the one that we recruited to this kind of thing.

We came up with this idea of using genetic conflict to understand virus-host interactions. The idea here is that you have a viral encoded antiviral factor, restriction factor, you have an antagonist. [00:07:00] Over evolutionary time, you have host which will escape from the virus. There will be polymorphisms and the population that allow some host to survive better than others. Then you will have viruses which will either in that species or from another species re-adapt. This sets up, this scenario where if you look at a sequence where nothing has happened, you get some mutations but you don't accumulate mutations. Whereas, in the presence of the antagonist, you accumulate many more mutations than when you would've expected. This is the sign of what's called positive selection.

The way, the metric for looking at positive selection is something like this. We have an amino acid sequence here, which encodes "Seattle." That's four mutations here, down here, but the dN/dS that is the number of mutations which changed amino acids, over the ones that we don't [00:08:30] change amino acids is less than one, which is purifying selections. So "Seattle" still looks pretty much like "Seattle." In this scenario, we still have four mutations here, but now the dN/dS is greater than one where most mutations are now changing amino acids. Seattle becomes "tea time," which is very big chance because Seattle is a coffee town. [laughter] I probably told that joke several hundred times. [laughter] Until I was asked [00:08:30] if this talk I had retired that joke forever but I resurrected it.

We can look at dN/dS, the way we look at it is over a phylogenetic tree. We had the sequences of things from a gene from a bunch of different primates. We calculate the dN/dS ratio actually from the common ancestors. This dN/dS is to this primate from the common ancestor between B and C, that is from here to here. [00:09:00] So we say positive selection occurred along this branch. We can also use this to look much further back in evolutionary time because we can calculate the ancestors at each node. We can see episodes of positive selection here at the common ancestor of A, B, and C. Here's the common ancestor of A, B, C, and D where there's positive selection on this branch, but not so much on this branch, which allows us to go much further back in time.

The initial question [00:09:30] that Sara Sawyer and Harmit and I posed was, "Does APOBEC3G bear the signatures of adaptive evolution? Is there an arms race? Has APOBEC3G evolved in response to Vif and its known antagonist?

The first question fell pretty easily, where we sequenced APOBEC3G over a large number of primates, and we did these dN/dS ratios. (6) The surprise was we found that, the adaptive evolution APOBEC3G [00:10:00] was much, much more ancient than we ever had expected it to be. We found positive selection in APOBEC3G in every lineage, everywhere, all the time, which was not what we were expecting.

That led to this idea of what we call paleovirology: that there are more ancient things that we know about that are driving selection on the genes that we know are important today.

The second half of the question is, has Vif driven this? Took much, much longer and it took us [00:10:30] a long time to understand how to use this method with the idea that you had to look in the right places. (7) There was a long time between here and here where we actually show that APOBEC3G and Vif actually are coevolving in genetic conflict. And the way that this was done is we had to look in the right places. In this case, we looked specifically among the SIVagm's, where we could see that this is a population where the conflict is ongoing at the [00:011:00] Vif–APOBEC3G interface.

Let me briefly talk about three ways we use these methods to understand HIV biologies. The first is that the sites of direct interactions between virus and host proteins can be mapped using positive selection. The main idea is that the selection occurs at the interface between virus protein [00:11:30] and the host protein. It is actually the interface where you expect the positive selection to occur, which is one of the reasons it took us a long time to find an APOBEC3G. This is actually a structure of MxA (human myxovirus resistance protein A) and the positive selection is occurring down here in this unordered loop four, which actually isn't the thing important for HIV, but just an illustration of how we use this model. We can do this at a codon level which is how [00:12:00] we do this model, actually.

There were a lot of examples I could show about how we've used positive selection to map sites of interaction, and I was going to show Trim5, but I thought that Joe was going to talk about that so I took that slide out. Let me show that in tetherin instead. Tetherin is a restriction factor discovered by Paul [Bieniasz] here in the front row. Positive selection looks like this. This is the C terminus of tetherin and this is a phylogenetic tree of a bunch [00:12:30]of different primates here. And this amino acid at the C Terminus can be a tryptophan, it can be a leucine, it can be a cysteine, it can be a proline, and it jumps back and forth in evolution. It goes back and forth from one thing to another. That is what positive selection looks like. And that's what told us that this was the part of tetherin which was going to be important. It turns out that this is the part which is [00:13:00] the binding site for Nef. Humans do not have this region right here because this is a little bit out of order. It told us that this is more ancient. So vpu, another accessory protein of HIV, requires sequences in the transmembrane domain. And there is an amino acid here which was shown to be important, but this is not positive selection. Here, we have genetic drift where all the Hominoids have one thing, [00:13:30] Old World Monkeyshave another thing, New World Monkeys have a third thing. This says that Vpu was new, Nef was old. In humans where this site of interaction is deleted, that is all humans have a deletion over the site of positive selection, led to one of the adaptations of HIV-1 to humans, and that the Vpu gene had to adapt to a sequence in the transmembrane domain to antagonize human tetherin. [00:14:00] We have lots of other examples of how we use this for other restriction factors as well.

We can determine the age of pathogenic viruses by using this method. Let me go back to a while ago when people were sequencing HIV and SIV strains and trying to figure out how old these things were. In the beginning we got ridiculous numbers where they concluded common [00:14:30] ancestor of HIV-1 and HIV-2 was about 40 years ago. (7) There was one which was a little bit better, which calculated that HIV-1 and SIV separated by 1,000 years ago. (8) Mike Worobey, who talked last night, did a really nice thing where he had a calibration point of the island of Bioko, where there are monkeys separated from the mainland by about 10,000 years, which give him a calibration point, which showed that all these numbers were off [00:15:00] by a lot. (9) And he used this to estimate that it is about 30,000 years.

And even that actually had to be wrong. One of the reasons we knew it was wrong, well, we thought it was probably wrong, was that there was an endogenous retrovirus in a prosimian, so very distantly related to the other SIVs, but this one was at least 4 million years old. Big difference between 30,000 and 4 million. [00:15:30] The way we use this method of evolution-driven genetic conflict is, over time, we have these antiviral factors and we can figure out when the site of interaction of these antiviral factors has changed. So if we know the interaction site, we can see on a phylogenetic tree when that has changed. When that has changed, we postulate a pathogenic challenge, that is, an ancient virus that drove [00:16:00] that change. We don't have this half of the equation because we don't have those viruses, but we do have this half, and this half of all the rate that we can measure.

The idea is we have these different interfaces, and we can put those on a phylogenetic tree. You can see the common answer here is this circle because there's a circle here and there's a circle here, which meant that the common ancestor here was a circle, and here was a circle [00:16:30] and that it changed here. Here we have something which drove that change, and here's one which was older, where there was a change at the surface of the antiviral factor and the antagonists that was here. And so we say that there was a selective force which drove that change, that it is a pathogenic virus, which couldn't encode an antagonist for this. [00:17:00]

With APOBEC3G, we knew where to look. (10) That is, we knew the sites where APOBEC3G bound to Vif, and it's someplace in this region. The way we do this is not just by looking at sequences, but actually doing functional studies. There is an alanine at this sequence. This is in the guenons (cercopithecus monkeys) down here. The viruses which affects those guenons or SIV De Brazza (SIVdeb) can—this is the virus infectivity assay. [00:17:30] Vif, which is encoded by the SIVdeb can overcome the APOBEC3G of all of these monkeys that have the A here, but none of the other Vif's, though shown here, but we have a lot of other ones, can overcome an APOBEC3G that has that mutation. Yet, it's only that mutation, which is important, because if we just change that one amino acid, now, all the Vifs can [00:18:00] overcome it. It says that that was an escaped mutant, and then the virus re-adapted to that. So when I talk about making hypotheses based on simple experiments, that's what I mean here.

Here we have Cercopithecus. They all have an A here, their out-group has this D. We know that this is an escape mutant for a pathogenic—something that drove that selection, the ancestor must have had an A. This was 5 million years [00:18:30] ago between these variants. So there was a something which drove that change 5 million years ago, that had an antagonist that acts at APOBEC3G with the exact same specificity as our modern lentiviruses.

So that led us to the conclusion that the primary lentiviruses are not 30,000 years old, they're millions of years old, at least 5 million years. We have another set of data on another set of monkeys that put it at least [00:19:00] 10 million years. Welkin Johnson is another person who uses this kind of technique. He did it totally independently with Trim5 and capsid interactions and came up with the same conclusion, that the primary lentiviruses are at least 10 million years old. (11) These are a whole bunch of primate lentiviruses, and we can say that there was a pathogenic lentiviruses, some semi-primates at least 5 million years ago, and probably longer. The reason I say pathogenic is that [00:19:30] we have selection going on.

Finally, the thing that we use this for is that we can predict new antiviral activities based on positive selection. This is just one example. (12) We did a screen of all TRIM family members of which there are a lot, and one of the most interesting ones was this gene TRIM52, which based on the signals of positive selection, and its other signals of evolution, [00:20:00] we predicted it would be an antiviral gene. It was not antiviral against HIV though. But paper just came out last week, showing the TRIM52 inhibits a Flavivirus. (13) so that we can actually identify these things and we can't always figure out right away what they're good at, but somebody will, sometimes.

The idea here is that the viruses we have are modern, but they are precursors of much more ancient things. [00:20:30] The immune system we have today was not driven by the viruses we have today. Our immune system was selected for by the viruses we had in the past. We can tell our modern viruses that our modern antiviral genes. We can use this information to calculate back when there were changes in the specificity of this antiviral genes, and then then postulate when there are pathogenic viruses in the past that caused those changes. The important thing is not what [00:21:00] these viruses are, but the fact that they affect the specificity and the repertoire of what we have today in terms of our innate immunity. And also what viruses can or cannot adapt to humans.

When I talk about some future paths, this actually means what we're doing. Using evolutionary signals to define holes in the human innate immune system. That is by looking at lots of [00:21:30] different primates and their evolution, we can figure out what genes actually—the immune system we have is not always the immune system we want. There are genes which don't work in humans that work in other primates and we can use this to figure that out.

We are continuing to apply these principles of positive selection to uncover additional lentiviral restriction proteins. For some of the specialists in the audience, there is a paradox of restriction factors that don't show [00:22:00] the signature of positive selection and we're trying to figure out now what that means.

Every year at my lab there's a hike to different lakes in a mountain. This year we went to Summit Lake near Mount Rainier, and these are people in my lab. This was the first picture we took on my lab in 1992, where everybody had a lot more here. This is [unintelligible 00:22:23] Ramani, he is someone you might recognize and that's me. Thank you.

[applause] [00:22:30] 

Paul Bieniasz (Moderator): Okay. One over there.

Michael: Yes.

Paul: Jon. Go ahead, Jon.

Jonathan Stoye: You talked about a pathogenic lentivirus driving the changes. Do you actually mean a pathogenic lentivirus or could it be some other kinds of virus? For example, TRIM5 sees MLV (murine leukemia virus). Could it have something like MLV [00:23:00] that drove those changes rather than a lentivirus?

Michel: No. I mean a lentivirus, probably. It is that the exact same specificity of a lentivirus that is what's driving this. It's hard to imagine that—In the beginning, I think we thought that, but it's the level of specificity between the escaped mutants and the mutations in restriction factor probably mean it is a lentivirus. [00:23:30] If I only had one gene, I would say, okay, maybe, but we have multiple genes where the selection is driving it to the same place. We need a virus that has lots of these different characteristics and those are lentiviruses. It's a combination of these things that it's probably lentiviruses.

Audience 2: All right. That was very impressive. What I wanted to find out—so when you look at the pathogenicity of [00:24:00] those [unintelligible] compared to all the others, is there a way that we can predict when the pathogenicity got associated with retroviruses and what possibly drove this system? What implications that could be moving forward to say being able to do something, now like we are looking at functional cure?

Michel: Yes. That's a great question. The question that this addresses is that mostly SIVs [00:24:30] today are not pathogenic. Some of what we've done a little bit explains, not the mechanism, but the rationales—That these are very ancient viruses. There has been a lot of time for host adaptation to be tolerized to their virus versus their pathogenic effects, which may have affected it earlier in their evolution. Second part, is that we will cure HIV before humans evolve. Yes.

Paul: Ron. [00:25:00].

Michael: Oh, sorry, Ron.

Ronald Desrosiers: If a particular, APOBEC sequence protects against some Vifs but not others, might then one then expect an advantage to having heterozygotes or great variation in the number of APOBEC alleles, say, in the human population to protect against a broader range of cross-species transmissions?

Michael: Yes, that's a great question. When we talked about this host [00:25:30] virus arms race, viruses evolve much faster. And the question always comes up: How does the host ever win? The host wins with heterozygotes, by having different versions of the same gene that the virus can't evolve around. We've seen that in various monkey species. HIV has not been around in humans long enough to cause any of that kind of pressure. In humans there are—APOBEC3G does not have any [00:26:00] interesting polymorphisms that cause protection where we would see it. Some of the other APOBEC genes do, but they don't have quite the effect.

Audience 4: There are many more viruses in the world than just the lentiviruses. In the case of lentiviruses you had clues about what genes to look at, but can you see evidence of selection that you could attribute to other viruses, or where you're still looking for viruses to attribute [00:26:30] them to?

Michael: Yes. This method is most mostly been applied to lentiviruses. We're trying to do it with some other system. MxA is actually a good example, where we can see positive selection along certain lineages. It is likely either an ortho- or paramyxoviruses, but it's taken us a little bit longer to get into these other fields, but I believe that this will be useful for a lot of things.

Ruth Ruprecht: [00:27:00] Mike, what you have described as evolution based upon protein-protein interaction, but retroviruses, especially lentiviruses like to have this complex RNA structures. Could you comment on the selection driven by RNA structures interacting with hosts structures?

Michael: [00:27:30] I'll think about that more. I probably could, but I can't right now. RNA is harder because we don't have a metric to standardize it. With DNA, we can look for coding versus non-coding. RNA, it's a whole order of magnitude harder, you have to look at folding versus non-folding structures, and there aren't good metrics yet, but I think there are people who do that kind of thing, but I don't.

Paul: Last question,

Carol Carter: Mike, do the endogenous retroviruses or retroelements influence this at all?

Michael: John Coffin hates when I say this, but: the signature in APOBEC3G is so constant that, in some sense, it may be hard to imagine that it is always exogenous viruses which are driving some of the selection, which is definitely not Vif. The APOBECs also work on retroelements, and in our very first paper, that was one of the things we propose actually, a lot of this has been driven by the constant pressure of retroelements, and John hates it when I say that.

Paul: Okay. Let me just close by saying what you've seen this morning is just a sample of the incredibly rich biology that has dominated the study of HIV and has served as a model for the study of other viruses. Thanks to all the speakers. [00:29:00] Thank you for being here.

[00:29:04] [END OF AUDIO]

Citations

1. Cordonnier, Agnès, Luc Montagnier, and Michael Emerman. “Single Amino-Acid Changes in HIV Envelope Affect Viral Tropism and Receptor Binding.” Nature 340, no. 6234 (August 1989): 571–74. doi:10.1038/340571a0.
2. Emerman, Michael, Mireille Guyader, Luc Montagnier, David Baltimore, and Mark A. Muesing. “The Specificity of the Human Immunodeficiency Virus Type 2 Transactivator Is Different from That of Human Immunodeficiency Virus Type 1.” The EMBO Journal 6, no. 12 (December 1987): 3755–60. doi:10.1002/j.1460-2075.1987.tb02710.x.
3. Emerman, Michael, Rosemay Vazeux, and Keith Peden. “The Rev Gene Product of the Human Immunodeficiency Virus Affects Envelope-Specific RNA Localization.” Cell 57, no. 7 (June 30, 1989): 1155–65. doi:10.1016/0092-8674(89)90053-6.
4. Guyader, M., M. Emerman, L. Montagnier, and K. Peden. “VPX Mutants of HIV-2 Are Infectious in Established Cell Lines but Display a Severe Defect in Peripheral Blood Lymphocytes.” The EMBO Journal 8, no. 4 (April 1, 1989): 1169–75. doi:10.1002/j.1460-2075.1989.tb03488.x.
5. Guyader, Mireille, Michael Emerman, Pierre Sonigo, François Clavel, Luc Montagnier, and Marc Alizon. “Genome Organization and Transactivation of the Human Immunodeficiency Virus Type 2.” Nature 326, no. 6114 (April 1987): 662–69. doi:10.1038/326662a0.
6. Sawyer, Sara L., Michael Emerman, and Harmit S. Malik. “Ancient Adaptive Evolution of the Primate Antiviral DNA-Editing Enzyme APOBEC3G.” PLOS Biology 2, no. 9 (July 20, 2004): e275. doi:10.1371/journal.pbio.0020275.
7. Smith, T. F., A. Srinivasan, G. Schochetman, M. Marcus, and Gerry Myers. “The Phylogenetic History of Immunodeficiency Viruses.” Nature 333, no. 6173 (June 9, 1988): 573–75. doi:10.1038/333573a0.
8. Sharp, Paul M., and Wen-Hsiung Li. “Understanding the Origins of AIDS Viruses.” Nature 336, no. 6197 (November 24, 1988): 315–315. doi:10.1038/336315a0.
9. Worobey, Michael, Paul Telfer, Sandrine Souquière, Meredith Hunter, Clint A. Coleman, Michael J. Metzger, Patricia Reed, et al. “Island Biogeography Reveals the Deep History of SIV.” Science 329, no. 5998 (September 17, 2010): 1487–1487. doi:10.1126/science.1193550.
10. Compton, Alex A., and Michael Emerman. “Convergence and Divergence in the Evolution of the APOBEC3G-Vif Interaction Reveal Ancient Origins of Simian Immunodeficiency Viruses.” PLOS Pathogens 9, no. 1 (January 24, 2013): e1003135. doi:10.1371/journal.ppat.1003135.
11. McCarthy, Kevin R., Andrea Kirmaier, Patrick Autissier, and Welkin E. Johnson. “Evolutionary and Functional Analysis of Old World Primate TRIM5 Reveals the Ancient Emergence of Primate Lentiviruses and Convergent Evolution Targeting a Conserved Capsid Interface.” PLOS Pathogens 11, no. 8 (August 20, 2015): e1005085. doi:10.1371/journal.ppat.1005085.
12. Malfavon-Borja, Ray, Sara L. Sawyer, Lily I. Wu, Michael Emerman, and Harmit S. Malik. “An Evolutionary Screen Highlights Canonical and Noncanonical Candidate Antiviral Genes within the Primate TRIM Gene Family.” Genome Biology and Evolution 5, no. 11 (November 1, 2013): 2141–54. doi:10.1093/gbe/evt163.
13. Fan, Wenchun, Mengge Wu, Suhong Qian, Yun Zhou, Huanchun Chen, Xiangmin Li, and Ping Qian. “TRIM52 Inhibits Japanese Encephalitis Virus Replication by Degrading the Viral NS2A.” Scientific Reports 6, no. 1 (September 26, 2016): 33698. doi:10.1038/srep33698.

Index

• 1.5 John Coffin — The Origin of Molecular Retrovirology
• 4.0.2 Ruth Ruprecht — Session 4, Introduction 2
• 4.1 Ronald Desrosiers — The Origin of SIVmac: Non-human Primate Models for HIV
• 4.4 Michael Worobey — Spread of HIV in the New World
• 5.3 Michael Malim — Discovery of APOBEC Restriction
• African green monkeys, vervet monkeys (Chlorocebus)
• APOBEC
• arms race
• Bioko, Equatorial Guinea
• capsid, capsid protein (p24)
• Carter, Carol A.
• Cercopithecus monkeys (guenons)
• coevolution
• control — experimental control, control group, blinded experiment
• credit, priority
• cure vs. remission of HIV/AIDS
• De Brazza's monkey (Cercopithecus neglectus)
• early theories of AIDS etiology
• education and early career
• env
• epistemic object becomes the technical object
• Flavivirus
• Fred Hutchinson Cancer Research Center
• Genes
• histone
• hypothesis
• in vitro vs. in vivo
• Johnson, Welkin E.
• Lewin, Benjamin
• Malik, Harmit S.
• mechanism
• Milwaukee, Wisconsin
• models (model systems, model organisms, modeling)
• molecular clock
• Montagnier, Luc (b. 1932)
• murine leukemia virus (MLV)
• MxA (human myxovirus resistance protein 1)
• natural selection, evolutionary selection, evolutionary fitness
• nef
• Paris
• Pasteur Institute (Institut Pasteur)
• phylogenetics
• reading frame, open reading frame
• restriction factor
• retrovirus classification, subfamilies, and genera
• rev
• Sawyer, Sara L.
• scientific competition and collaboration
• Seattle
• sensitivity and specificity; false positive, false negative; biological specificity
• sequencing
• Session 5: Molecular Biology of the Extraordinary Virus
• simian immunodeficiency virus (SIV)
• Stoye, Jonathan P. (b. 1952)
• structural biology
• Temin, Howard M. (1934–1994)
• tetherin
• TRIM5α (TRIM5alpha)
• University of Wisconsin-Madison
• vif
• vpu
• vpx