Ep. 124: “HIV Latency” Featuring Dr. Sharon Lewin

This is episode 124 of the Immunology Payout Cast, HIV Latency with Dr. Sharon Lewin. Hey everyone, this is Dr. Jason Golds with Dr. Brenda Rat. Welcome back to Immunology Podcast, where you have conversations with immunologists. The Immunology Podcast is brought to you by Stemsel Technologies, a global biotechnology company supporting life science research and fostering communication and collaboration in science. If you enjoy the Immunology Podcast, rate us and leave a review. We're always looking for feedback on how the podcast can be improved and for suggestions on guests. Today we have Dr. Sharon Lewin from the Doherty Institute on the Podcast to talk about her research on HIV. We also got our usual random of recent highlights in Immunology news coming up, but first. Scientific research is challenging, but isolating your cells shouldn't be. Save time and energy by choosing a cell isolation method that lets you isolate a wide range of cell types from virtually any sample source without the use of columns. For a limited time, request a free EZ-Sept sample and get a complimentary pair of highly coveted science socks. Request your free cell isolation kit sample now at stemcell.com/easy-sepsox. Alright, so you got to go skiing recently. Yeah, you did not get to fly. I did not. Nope. We shut down almost the whole country from a giant snowstorm followed by ice and then cold. Well, my condolences. I hope you guys get a couple of days in like, you know, above freezing a little bit, and so I'm hoping it all melts it should, but it's a little rough. Alright, okay. You never have the weather. Why don't you. Let's talk about the science. That's nice and warm because hot off the press. It is in a, there you go. It's definitely hot off the press. Alright, I'm going to talk to you about a paper that came out March 5th, which is in the future in cell. It's like in a low future. I know, right? Sympathetic alpothelial crosstalk governs tissue resident memory T cell immunoservailants in the skin. Again, first authors ping-zang corresponding authors are ting-zhu and being zang. Alright. So sympathetic nerves, right? The adrenaline flight or fight. They found so there is a known effect where more CD8 tissue resident memory cells, TRMs are protective against cancer, right? Because they're going to see them there and kill the cancer cells. But they were trying to understand how that's regulated in the skin. And so they first looked at sympathetic nerves and tried to understand, okay, there's sympathetic nerves near these CD8 cells. And then they're like, and so they showed that if they did a dread receptor, and that's those receptors that are designed to be exclusively activated by drugs, you can inhibit the sympathetic system. In mice, it goes away. So you basically blast them with a chemical that inhibits a sympathetic system and CD8 resident, the CD8 TRMs go by by. So that was established that that's the thing that happens. And then, and then they also did it through another chemical that wasn't, you know, genetically derived. Like, okay, well, let's knock out the main receptor ADR B2 on all different types of immune cell populations, because that's clearly what's going to go on here. And then we'll see which immune cell population is driving this effect. And that did nothing. And they're like, okay, well, if it's not the immune cells directly, they're being influenced here, right, by the signaling, then what is it? And so they went and found it was keratinocytes. And so they figured out, again, using genetic models that it's the keratinocytes that really drive this. So you have these keratinocytes that respond to sympathetic stimulation or inhibition. If you stimulate it, the cells go away. And you have more cancer or you have more eventually they show more melanoma, but they go, there's more of these cells. And if you inhibit sympathetic drive, you have more cells. Okay. So they're like how. And so they started to then dissecting what pathway could be used here. And so they eventually determined it was the chemokine. Except, oh, and really quick by very correction on the author because they finally get here. There's two first authors, pang zang and juju meow. So then the authors go on and in pretty elegantly dissect the pathways out and identify the critical chemokine here that's driving this, which I'll get to, which is CX CL 16. And discover that the container innocent keratinocytes secreted and pull in the resident memory cells, because if you oblate the resident memory cells receptor or you oblate it, the chemokine in these skin cells, it stops working. Now, the cool thing on these mice is they can use the, they can locally inject chemokine inhibitors or adrenergic chemicals or the special drug for the dread receptors into one side of the backs subcutaneous leave versus the other with saline. And so you have a same mouse control a lot of these studies, because it's the skin right so they can look at local effects. And then they go and take this to a melanoma system and show that. If you block melanoma or if you put Mel E to use a melanoma system, the. The cell, oh, so sorry, take a step back. They also use an OVA system and show that the cells that move are clonally related, right. So there's not proliferate. It's not driving proliferation, which was a question it's not driving proliferation, the resident memory C cells is driving recruitment, which is how they got to it being a chemokine based effect. And they showed that if they did some type of signal that's causes clonal expansion and OVA plus CFA, you get about you get more clones at the site, if that makes sense. So you have the skin cells pulling clonal clones to the location you're not having them reproduce based on a sympathetic drive. It's migration, not, not reproduction. And then they put, they then use a melanoma system, which like in this system, immune cells, suppress it. And if you have more resident memory cells there, it's known that you have less of this cancer. And guess what, when you do sympathetic inhibition, you get more. Less cancer. If you turn on the system through acute stress or chemicals, like, you know, good old adrenaline, but they're a little more sophisticated than that. You get these are chemical that hyperactivates it. You get more cancer growth. And basically, chilling out and not being stressed in your skin through inhibition and sympathetic systems, pulls more resident memory, CD8 cells there, which help immune surveil against cancer. Again, another like, it feels like almost holistic medicine or something. It's like, don't be stressed because that's gonna affect your creatinus sites. Yeah, like testosterone was like, you know, you need your PC low cell sweet chill. Teases get recruited so meditate, but I have cancer. It doesn't matter. Just meditate. I don't know. I mean, I find you very interesting. I think there is enough anecdotal evidence of just that not being terribly stressed is good for you. So I guess this having some inside of mechanisms by which this connection is explained is very, very interesting. So yeah, don't be stressed. It's gonna cause you to lose your chill. Yeah. Very interesting. Yeah. Okay. So from my side today, I have a very B cell centric selection today. And it's good because I have like, Beatles doing opposite things here and the different circumstances. I think it's a nice, it's a nice combination of paper to have today. So I want to start with B cells being, being bad, I guess, or Beatles being problematic. So this paper is published in science, immunology, I think 30th of January, and it's called B cells drive city for diesel, immunosenscence and age associated health decline. and first authors are Sadkan and mine and the senior authors are twin brothers, Sean and Daniel winner from the University of Toronto. So I thought that was very funny. How would you like to have a lab together with your twin brother? Repi. I think it's great. I think it's great. So well onto the paper itself. So as the title already kind of keeps away. There's a lot of interest and there's a lot to understand about the role of this infamaging quote unquote a process in which with age comes this chronic low grade inflammation that increases. As we get older and that is linked to a lot of the pathology and age related complications of old age. And in particular, we know that it's, you know, associated with the crease vaccine efficiency, increases of the pathogens, increased proportions of activated B cells, T cells and kind of inflammatory mediators and that's something that is kind of well known and well established. And so in this paper, I find it kind of cool that the concept of kind of this paper is pretty simple. What happens if we don't have B cells. In terms of this inflammation because in the same way that T cells have suffer kind of clear changes in the repertoire, in the sense of the proportion of naive T cells versus effector memory central memory, there's an increase in effector subsets. B cells also change. And in humans, there is these, well, and there's a the concept of a age associated B cell that I think is better defined in mice and kind of been translated into humans. These are B cells that are expressing city 11c, I think also some markers. So they're kind of a little bit more inflammatory. They are also expressing. So it's mostly, there's a T bed positive. They, they in the context of, so they are, they are the increasing amount in all elderly mice and also some populations in human that were I think they're more associated with what is called a term that I don't think people use so much, which is called a typical B cells that are associated with human and human studies of chronic infection in which you have again this. This city 11c positive T bed positive highly these T cell active at B cells are capable of activating the T cells very strongly, and this accumulate this kind of phenotype accumulates with age. And so in this paper, basically what they do is say they have mice in which they have a. They are knocked out in B cell and B cells. So, of course, they can only do this because they have mice in you know, pedestrian free conditions. So they're, you know, they're not going to die. Of course, if you don't have B cells in the real world, mostly going to die. So sometimes it's a when you look at the conclusions of this work, there's, we mustn't forget that there's a trade of there's a reason why we have B cells. It's not just to drive immuno fluorescence, but in order to, you know, to protect us from the seas, but this in a way this paper shows that this protection comes at a cost. So what do they do? They have this B cell knockout cells in knockout mice and they compare, they compare the look at the mice as they as they age and then. They compare and just shows their role in T cell and going to inflome aging in general. So they, when they look into age, when they remove the B cells from this H mice, they look around two years of age, so 24 months, that's quite a senior mouse. You see basically a reduction in this inflome aging and in this H immune system phenotype and particularly on the changes that happen with age in the distribution of naive T cells versus exhausted and factor memory T cells and central memory T cells. There's more of a conservation of naive T cells in both the sense of their phenotype, but also in a reduction in the loss of clonality that is also very associated with age, you end up having expanded clones, you have less diversity on your T cell repertoire. This is something that they see at least partially corrected by the absence of B cells indicated that B cells are playing an important role in driving this clonal expansion slash differentiation of T cell. So the small mice part of these pieces that are expanded mice to have pieces are this ABCs, this age associated B cells, and which is also, so in this case, they are defying them as CD 21 negative and CD 23 negative CD 11 C positive T positive B cells. So that's completely the most, this result with the absence of B cells is the most is the defining result of this paper is the fact that by removing the B cells, you end up preventing a lot of the inflome aging. And when they look at the stimulate the T cells from this move from these B cell knockout mice and with PMA, I don't know, I see they also see that they are producing less inflammatory cytokines and associated with more or more naive phenotype in general. And they're not proliferating so much X vivo, so a lot of measurements they do in the show that that if you are, they are less, they are going to less differentiated, but also if you stimulate with C 3 C 28, you have the cells that have very actively very well similarly to what naive cells do. So again, indicating that they are they have characteristics are associated with a younger phenotype. This results, this translates in the mice, this translates in better health span and lifespan and they have this frail to scores are improved and which kind of indicate the quality of the aging of the mice. And in general, this mice have better less senescent associated phenotypes this test, the secretory phenotype that have reduced fibrosis. So they basically again, they seem to be spared for from a lot of the hallmark signs of aging. And they see that they can even if they are the pleatin B cells using anti-CD 20 monoclon antibodies like our retoxymal equivalent, they can also reduce, they can improve the abundance of naive cells, even if they know if they, the pleatin B cells in kind of middle age mice 12, so 14 to 15 months old. And this actually helps restore or kind of recuperate some of these quote unquote kind of young T cell phenotypes and improves also the kind of the overall health of the mice. So how is this, what is connecting the B cells and the T cells and the aging and they show that a key factor here is signaling through the insulin receptor in the B cells. And insulin receptor, so hyper insulinemia is also associated with with with age. And we know that activation of the of the activation of the insulin receptor activates has a lot of also metabolic effects. And it also activates pathways like P13 kinase and AKT that drive M to activation and these are all associated with inflammation and immune cell activation in general. And so what they see is that this these B cells that are the C at M and C positive TV positive B cells that are associated with age, they are expressing the insulin receptor and they're responding to this stimulation through the insulin receptor they have increased activation of the M third pathway and this seems that so they conclude that the insulin signaling is in a way supporting the expansion of this particular self subset. And this cells because they have increased expression of MHC class 2, which is dependent on insulin receptor signaling, which is a show using flux mice that this is kind of the connection between the age, the B cells and the effects on the T cells. because they are being stimulated through increased amounts of MHC+2 on these B cells. And this is kind of mechanistically how the B cells are inducing this activation and this aging of the TISL compartment directly. And that these C11C positive T-vit positive B cells are important in connecting this compartment. And so I thought it was pretty cool because again, there's a lot we don't understand about the role of this especially adaptive immune system in both associated with H, but also causing the symptoms of aging, so to say. And of course, we're not going to get rid of our B cells because we need to not die of infection, but I think it's very interesting to see whether we could in a way modulate the B cells that could actually have some meaningful effect on our immune system as a whole and how we age the whole. So it sounds like just by doing their job, they cause other cells to do their job and that makes them get aged. Yeah. Yeah, I know why you just get tired from doing work. Yeah. Yeah, but I think that this B cells, so this particular C11C T-bed, I think they are, well, I'm not a B-sex person, sometimes for me, they feel like they're a bit an overkill, like they're, you see them in the context of chronic diseases and they usually associated with negative effects of B cells. So it looks like they are a slightly undesired version of B cells. Every cell has a main purpose for why it exists, otherwise we would have long ago. So I bet they're needed for infection and getting and coordinating inflammatory responses in inflammation, oxidative damage, and getting old. And so sure, if you get rid of all inflammation, you can age and glory and die of a pathogen before you get old. I mean, that is, that is in a way for what I see, that's kind of the trade-off, you are stuck with this, you need a, it's much more important to keep you safe from pathogen than to prevent you from aging, once you have kids who cares, evolution doesn't. Yeah, exactly. Like are you going to make it or are you not going to make it, that is the question. Well, I have a story that definitely happens with aging. It is glorious, it is microbiome-mediated, and it is wacky. So pretty much every one of my checkboxes have been filled with this paper. So it is in nature coming out the 28th of January, which this time is in the past, intestinal macrophages modulate a sinucleopathy along the gut-brain axis. First author, Sebastian D'Shepper, co-second authors, I think I'm doing this right, are victorious, constant elos, and James Conway, and co-last authors are so young, hung, and Tim Bartles. So in Parkinson's disease, there is, that's called alpha, sinuclean pathology, right? So that's where these alpha, sinuclean proteins get aggregated. You get these Louis bodies and other things. And then when they're in certain neurons, you no longer have motor control, because it borks up your motor control of your body when these neurons go and die. That's basically Parkinson's disease explained very, very briefly. So one of the interesting things is that constipation often occurs very early in Parkinson's disease, sometimes decades earlier before motor symptoms. But constipation is a motor problem in and of itself, right? And there are T cells responsive to alpha, sinuclean, AS, or alpha, as I'm going to call it here. So the question is, does Parkinson's start in the gut? And then spread to the brain. And because we all love efficiency these days in our busy, busy lives, is the answer apparently in this, from this paper is yes, yes, it does. So there's an enteric nervous system. And what they do is they create a, they use a mouse model, but they also can inject human proteins. So they'll, in this study, they use a mouse model that has this alpha, sinuclean buildup. And then they also have the proteins themselves from mice and people they can inject. These bad proteins versus good protein or they'll get bad, bad neuronal tissue or good neuronal tissue and proteins from humans. And that's the basis of these models, right? So they'll be injecting, they'll either have a mouse model that develops more of these misfolded proteins, which leads to Parkinson's symptoms, or they will have injections into the gut of either human or mouse. They usually do a lot of mouse work and then show human too, right to lock it in. So they identify that this really happens in my enteric plexus, more so than laminopropria, where this sinuclean gets absorbed when they do, in just the baseline models, they see buildups there early on or when you inject it, it'll build up there. They see a lot of macrophages in here doing their work. And so they're like, huh, why is it that the Mac, what are these macrophages doing? So what the macrophages do is they chew on all this naughty, naughty protein because that's what they're supposed to do, right? And they establish that it goes in and it sits there and hangs out. And if you inject into the, into the enteric area, the macroph, these proteins, you get this propagation from the enteric nervous system into the CNS over time of Parkinson's pathology based on both symptoms of the mice and looking at the brain. And you usually see the tissue first, right? You can see the tissue damage before you have the symptoms. So how is the hell is that happening? Well, they see more T cells and more T cells, clonally that are clonally aligned to this protein misfolding go to the brain over time. They're like, OK, so something about the, the macrophage uptake makes more T cells trained against this protein to go to the brain. OK, well, those T cells then go into the brain and destroy the brain cells that have the same, you know, same proteins, because that protein is there, right, this alpha S protein is there and that leads to the damage. So it's CD3, you know, CD3 T cells, not, you know, not particularly specific, they, they can see the damage. They then try to figure out, well, how is this being conducted? And so they then look at the macrophages and try to understand the signaling there and determine that macrophage, mesenteric macrophages through TGF1 beta are basically activating the T cells and telling them to go find other proteins in the body that have this bad naughty protein and go kill them. And so the macrophages are up taking this bad naughty protein early from misfolding in the gut, accumulating it there and then telling the T cells to go, hey, this is bad. Go find this everywhere else. And so if you do macrophage depletion in the intestinal area, you get rid of the entire phenotype. And so the story of Parkinson's, which is very like that, to me, this is a big deal is that it starts in the gut develops immune priming in the intestine and then conducts along the enteric nervous system or along the gut brain access, not the enteric nervous system. And the gut brain access. These cells are near the enteric nervous system. This is the enteric plexus, right, the mesenteric complexus, telling them to go up to the brain and go finish the job there. And so maybe if you start having a typical constipation, you could screen for this and then go on some type of therapy to suppress it so your brain doesn't get fried and you don't get actual Parkinson's because the constipation is such a leading symptom. And there you go. So I'm a bit confused about, in this case, a teacher of beta. Let's have them out. - Macrophages tell the T cells to go have a party. - Is there other side of, because I was thinking of a bit of, more of an anti-inflammatory cytokine, so I'm a bit, yeah, I would expect that. - It was a little weird. - Are these T cells that migrate, that are responding to these macrophages? What kind of phenotype do they have, do you know what they do? - They just most looked at the total T cell compartment, but they were formally interested in alpha-sidinuclein. They were primed to target alpha-sidinuclein. They're not just a T cell, right? They're T cells that have been coordinated by the macrophages to have the same target. - Yeah, I guess that's, yeah, it's not surprising 'cause we knew that there is this clear connection with the gut, and then what you mentioned, the, so I think, and it also makes sense given the environment of the gut that something will get primed in there. - And if you knock out TGF data of the Parkinson effect goes away, the cells don't, they don't cause disease. - Yeah. - That's very, that's very interesting. I wonder whether, yeah, I guess, definitely could have a improved screening, and I wonder whether something can be done because it's just starting, maybe still you're still in time to prevent - And to be creating the muscularis macrophages. Not the laminopropria goes epithelial cell, then laminopropria, the muscularis, and the muscularis is what touches the enteric nervous system, because the enteric nervous tells the muscles to move, right? So it's those macrophages, the ME macrophages. - Right, yeah, they have to be there close to where the protein is to be found. Very interesting. All right, so why don't I close this session today with another B cell paper, as I promised, and this one is published in Immunity. B cell in trinsic isletocycnelling regulates inflammation by promoting IELTS and expression in city 25 positive age associative B cell. So again, we're going to the age associated B cells, and in this case is a mechanism of kind of regulation of more tolerance. And first author, Juliet Gauthier, from corresponding author, Céline de la Loi at the University of Rome in France. And this is also really interesting another take on the role of these different subsets of B cells in inflammatory settings. And in this case, I think it's not so much about aging, although they are discussing this quote-unquote age associated B cells, but it's more about their role in inflammatory environments, and how these B cells respond to interferon gamma, they express a tea bed, they are kind of again known for interacting with kind of inducing more an inflammatory environment. But in this case, this is not always a case. So I think this kind of what confuses me a bit is not being a big B cell immunologist. So it looks like there's still a lot of the nomenclature still a bit confusing, because in this paper, they are looking at a way for this ABCs to be more anti-inflammatory by producing IL-10. But let me start from the beginning. This paper, the kind of the premise behind this paper is IL-2, we all know, good old IL-2 as a diesel immunologist, IL-2 is very much in my mind. And I think a lot about how IL-2 drives regulatory T-cells, CD-4 T-cells, CD-8 T-cells, how important it is. It has been, I know it was originally identified as a T-cell proliferation factor, but B cells also express IL-2 receptor, including CD-25, the high affinity IL-2 receptor. And B cells upregulate the expression of these receptors upon activation through their B-cell receptor. And other stimulations, the CD-40, a T-cell receptor engagement, things like that, activated B cells can respond to IL-2. So I guess the question is, what is IL-2 doing and does it matter? Because in the end, yeah, things pretty clear that most of what IL-2 does is affecting the T-cells, but let's see what our B-cells doing. IL-2 drives the differentiation of plasma cells. And through mechanisms that include the repression of Bach II, which is a known kind of necessary step to differentiate cells that are, you know, in the germinal centers of B cells, they start, they get activated, they go to the germinal center, they interact with T-cells, and they, you know, they affinity-majorate and they change their, their, their, the device of the device switch, and eventually they develop into plasma cells that are, you know, producing a lot of antibodies. And this plasma cells have different and transcription factors and different, the different programming than germinal center B cells. And they're usually more kind of permanently differentiated. And what they see in this paper kind of giving out the punchline is that there is a coordination between different stimulation that include the B-cell receptor IL-5, which is known for kind of increasing the activation status of B cells in collaboration with B-cell receptor stimulation, and that on top of this IL-2 also affects the differentiation of these B cells. And what is interesting is that it promotes, by promoting Bach II and preventing the loss of Bach II, promotes IL-10 expression in these B cells, and this ends up having a regulatory effect on the, kind of, the, the, the role of these B cells. So how does this work? What they do in this paper, they take IL-2, they, they knock out IL-2 receptor beta chain. And these results in B cells that are not capable of responding to IL-2, but also not IL-15. They show that it's very, that it's very efficient, that there really is a loss of function. And although the B cells are mostly normal, there is, there's a difference in how this B cells respond to stimulation when there's IL-2 presence. So there, you can see that B cells can, if they don't have the IL-2 receptor beta, and they don't respond to IL-2, they differentiate differently. And basically, IL-2, the signaling IL-2, dampens the plasma cell's responses. So they have this teaser independent and dependent context. And basically, there's some intrinsic effect on the signaling of IL-2 that promotes, that restricts this differentiation into plasma cells and promotes regulatory functions. So if you have the knockout, you get more plasma cells. And basically, when they show, they, they, they are, they look at a lot of the details of the signaling and they show basically that, there is, it is really IL-2 that is promoting, the B cells are dependent, sorry. There's some, here's where we get complicated, because there's some differences between the Invitro and the Invivo results. But just to keep it a bit simple, because I was too much. So the, when I take activated splinic B cells, so they take them from a splinic Invitro, the B cells that don't have IL-2 receptor have a more skew response towards a pro-inflammatory program. And they have activations that wants to to, for, and T bed, which is this hallmarks of pro-inflammatory ABC, H-associated B cells. And this, that kind of moves towards a more extra-folicular plasma cell differentiation. So there's this IL-2 is, in general, if you have signaling, you, you limit this differentiation. And they see that one of the, the, the, the, the hallmarks of this, this, this absence of this differentiation is an increased production of IL-10. And I think this is probably the most interesting result because although they still see the differentiation of these ABCs, the most interesting thing is that they see an increase in the production of IL-10 when IL-2 is when these bees are being stimulated with IL-2 on their and they have their receptor. So, and they show that this, the way that this works is through MAF, which is a transcription factor that will, that induces IL-10 and is usually associated with anti-inflammatory responses. And the IL-2 MAF axis is what shapes a lot of these phenotype that they see in these ABCs, including the production of IL-10. And when they do, so they test if they have MAF deficient B cells and, and although they don't see differences in the phenotype of the B cell, they do see differences in the production of IL-10, which ultimately seems to be a major effect in the overall response. And in mice, if they have any A-E-A-E model and they show again that if you have IL-2 receptor beta knockout mice, they have a higher clinical scores. And this is associated with IL, increased IL-10 production that increases the A-E effect on the mice. So basically, I would say, the conclusion of this paper is that B cells can sense IL-2, they're not indifferent to IL-2. And that under the right circumstances, if you combine IL-2 and B cell receptor, and also they look into different gamma in a situation where you kind of inflammatory situation, different gamma, IL-5, B cell receptor stimulation, the addition of IL-2 and the sensing of IL-2 by this B cells, resulting them becoming an anti-inflammatory A-B-C, rather than a pro-inflammatory one, and that this is mediated by IL-2 signaling. Interesting that they sense it, but it's kind of a switch, but not completely. Yeah, because the cells are still there. So I think this is what it was a bit difficult for me to understand. Their cells are still there. They're not, I don't see how they change a lot in the frequencies themselves, but it's what they do. But I think also this is difficult because the way they are defining these A-B-C's, I was just different in mice and in humans. So I was a bit kind of challenged by making sure I understood the substances that we're talking about. I think the most important is IL-2 signaling. Together with interferium, with B-C-R signaling, has this kind of unexpected effect of making IL-10 in the cells that are usually kind of associated with extrafilticates for initiation and inflammatory results and IgG production, things like that. All right, well, we're going to be talking about HIV here with Dr. Sharon Lewin at the University of Melbourne in just a minute, but before we get to that. At scientific events, a great elevator pitch can help you make a strong first impression by clearly communicating who you are and why your research matters. The trick is to keep it short, focused, and memorable. To help you craft your own elevator pitch, download stem cells free worksheet that guides you through the process. Find it at stemcell.com/beyondthepaper. Now for the second part of today's episode, we are welcoming Dr. Sharon Lewin. She is director of the Dohert Institute and professor at the University of Melbourne in Australia. And she has done very amazing work on HIV infection and her lab tries to understand ways to cure or to improve the treatment of the disease, which is still very important, very relevant topic nowadays. So, Professor Lewin, thank you so much for joining us today. All right, to be here, thank you, Brenda. Thank you for being here. All right, HIV research, right? Yeah, that's right. Okay, why the heck is it so hard to cure? Well, HIV is a pretty smart virus and the reason why we can't cure HIV is because it has the capacity to integrate into the host genome. So, once a cell is infected, HIV virus becomes part of the DNA and stays there for life. When you put someone on antiviral therapy, it blocks active viral replication and it does that incredibly well. However, the virus, like many viruses, has two forms, a productive form and a latent form. And once it goes into latency and it always goes into latency, it basically borrows into the DNA and sits there inside a resting memory city for T cell and stays there for life because those cells have a very long half life. So, a lot of you've been working on HIV for a very long time and it's very interesting to see how has our understanding of these limitations of therapy has grown in time and how has the treatments that we can offer people also changed from that perspective. So, where are we now? Maybe last 30 years since the peak of the epidemic and now we've found solutions to keep people alive. We haven't been able to get rid of the virus but how good are the options that we have now? So, the antiviral options we have now are absolutely fantastic. 70% of people globally living with HIV and that's 41 million people have access to and are on these treatments. Most people are taking a single tablet a day and that tablet contains either two or three antiviral drugs. You can't just take a single antiviral drug but they're co-formulated into a single tablet or they're now beginning to take injectable antivirals so that you could have an injection every two months. That's less common but a very exciting new area because maybe one day we'll be able to give people an injection every six months or even every 12 months. There are clinical trials looking at that. For a person that goes on to this single tablet a day, the virus which starts at very high levels in the body, you can measure it in a range of 100,000 copies per mil of RNA, a million copies per mil of RNA. Within three to four weeks of going on to this treatment the virus disappears to undetectable levels or conventional laboratory assays that measure down to 20 copies per mil. Once someone is so-called undetectable, the viral load less than 20 copies per mil. We know it's still there but it's undetectable by conventional assays. Their CD4 T cells can recover, larger cause of thymus function, T cell proliferation and you make new embedded T cells. They're never quite normal. You always have persisting low level immune activation but you're actually your health does return to normal. Life expectancy returns to normal and amazingly enough when you're on antiviral therapy you can't transmit the virus. It's a really important thing for people living with HIV so nowadays we tell people if you're on treatment you don't need a condom if you have sex because you cannot transmit the virus and there's a big campaign called U=U, undetectable equals untransmissible. So therefore you might ask well if antiviral therapy is so good, why do you actually even need a cure, what's what are we all fussing about? Well, antiviral therapy does come at a cost. Now in my country in Australia where the government pays for the drugs that people living with HIV take, the average cost of antivirals is about 20 to 30 thousand dollars a year. That's when they're still on patent but the rest of the world low and middle income countries can access treatment generic drugs and they're around a hundred dollars a year. Sorry, I think I said a day, 20 to 30 thousand dollars a year but globally in low and middle income countries that's about a hundred dollars a year. So that's incredibly cheap but a hundred dollars a year is still a lot of money in low and middle income country which might spend less than that on their total health budget. And today we've had amazing support from global institutions primarily the US government to make antivirals accessible but then whether that's sustainable forever that we can cover that cost we know is not likely as we've just seen with disruptions with global health policy. So first of all come at a cost. Second they come also with some personal costs there's still a stigma and discrimination for people living with HIV. They have an infectious disease that stigmatized and they have it for life. So many people with HIV really want to cure. And third as I mentioned earlier and given this is an immunology podcast your immune system never quite returns to normal. So you still have low level ongoing immune activation pretty much in everyone living with HIV it's lower if you start treatment earlier and in some rare people it can return to normal but that means that people with HIV add a higher risk of immune related comorbidities which are we cost we know heart disease is driven by immune activation cancer neurological disease and these all occur at higher frequency in people with HIV. So taking it all together the job's not done as you said at the very beginning Brenda. This is the holy grail. If we can work out how to cure HIV, which effectively means safely stop antiviral therapy remains well and not transmit the virus to other people. That would be an incredible advance, not only for people with HIV, but for our global funders. You remove, it's estimated that if you want to treat 95% of people with HIV, which is really the global goal, it costs on average $20 billion a year. So imagine if we could free up that amount of money for the healthcare system. So there's still a very important need for a cure. So I'm going to put my hat on in two ways. One, 20 billion a year as an American doesn't sound too bad. But then secondly, if we have a cure, won't they just charge 10 years worth of drug costs in the developed world for a cure? Because that's what pharma does, right? Yeah, of course. If it's 30,000 a year in therapy, it's a $300,000 cure. And now I got to go cure how many millions of people at 300,000 a pop? Yeah, yeah, good point. The health economics, I don't not sure we need to get into that for an immunology podcast, the health economics stack up. If the cure intervention is cost at a reasonable level, either way, one big difference with HIV is that if someone stops taking their treatment and taking treatment for life is a really big deal. Imagine getting infected as a baby, which still happens. Most people get infected when they're sexually active, you know, their peak, which is using their 20s and 30s and they're on treatment for 60 or 70 years. If you stop treatment, your virus rebounds to normal back to its original levels in nearly everyone in two to three weeks and you become infectious again. So there's a public health imperative to get as many people as we can on treatment. Where are we today? With enormous amounts of effort and funding, we're at 70%. We've never got, we know, we're near 95% in many parts of the world. In my country, Australia, yes, we are. In the US, you know, we're near that level of 95% in the richest, one of the richest countries in the world. So it isn't an easy feat to get everyone on treatment and then get everyone in care for 60, 70 years and get everyone to have beyond treatment forever. So there's a health imperative and that also factors into the economic burden because once you go off treatment and you infect someone else, then that becomes another, you know, million dollar addition to the healthcare cost. So we could get, there's been quite a lot of modeling done. The treatment of the intervention is important, but if it is because of the nature of infectious of HIV and infectious disease, there is an economic benefit to this approach. Okay. So let's go back to the immunology behind HIV and and and their study of this disease of weight. So one of the big issues is that you can get red, you mentioned it, the, you can get rid of the circulating virus, but you're going to have this latent virus is reservoirs that are going to be in mostly in city fortices or maybe not and they're going to become activated as soon as you, so they're going to be obvious as soon as you pause or as soon as you remove the treatment or are there other, whether the kinds of triggers that result in this, in this reservoir activation, and is there, I know that some of your research has gone into understanding this reservoirs and what is the angle? Can we get rid of them somehow? Yeah. So the reservoir is predominantly city forticells, about 99% of the virus in people on treatment is sitting in city forticells, a small percentage also in monocyte macrophages. For a long time we thought that the virus was sitting just in resting memory t-cells, but actually it's sitting in all t-cell subsets, naive memory effect in activated. We always have a small number of activated t-cells circulating even when you're fit and healthy in activated in resting t-cells. And over the years we've learnt that the virus has got different levels of latency. So what I say latency, what I mean is the virus is integrating the host genome and transcriptionally silent. As soon as that t-cell is activated, because it is seeing its target antigen, you know, as all memory cells do, they see something far and suddenly activate proliferate and then revert to become effector cells and revert back to becoming central memory cells. The virus also gets triggered because activation of the t-cell also activates the virus. But what we've learnt and actually my work were going right back to some of the earliest work I did in the mid-90s during my postdoctoral fellowship at Rockefeller. I was then working with David Ho, who was time out of the year actually in 1995 for discovering why combination antiviral therapy so effective. And he did the first studies together with Marty Markwoods event of effective antivirals. We developed what was then very sexy assays still associated RNA using real-time PCR, which is a big deal at the time. And what we found was that real-time PCR, which is of course now very basic, using sensitive assays such as real-time PCR, you could find RNA always in people on antiviral therapy. In other words, the cells were not truly transcriptionally silent all the time. It gets a little bit more complex than that because HIV has quite a few steps in its viral life cycle transcription, like many, you know, any gene and any virus, once it's integrated in the host genome, you get transcription initiation, elongation, completion, splicing, protein production, and then release of ureons for the cell. And most of the virus that's sitting there is either integrated in silent or integrated and not just undergoes transcription initiation because a resting CD4 T-cell is not the right environment for the virus to take off. It needs a lot of transcription factors, NFKPB, PTFB, a whole lot of other transcription factors present in an activated cell to complete its transcription. But think of it that you've got these viruses ready to go. And as soon as the virus, as soon as that cells activated, ban it's off. And what we see, and this is actually an area that's not really well understood. Because if this was stochastic and you just were sitting ready to go in an antigen experience T-cell and it sees its right action and it goes off, you'd expect that the time to viral rebound after stopping anti-rich viral therapy would be variable because it's stochastic. It depends on that T-cell. And remember, only one in a million T-cells carries a replication component virus to someone on antiviral therapy. But actually it's not stochastic. When you stop antiviral therapy, pretty much 95% of people rebound in two to three weeks. And that says to me that there's always some virus ready to go, ready to pop out of a cell. But while you're an antiviral therapy, you don't see it because it never can go on to infect new cells. So what my lab's done over many years is develop better assays to develop these low levels of RNA. Understand where those cells are sitting in the body because they're not also accumulating most of these cells are sitting in tissue, in gut and in lymphoid tissue. And my own interest has been how to activate that virus and allow it to be visible to immune mediatic clearance while you're on treatment. So all those viruses that are sitting there ready to go, how do you get them to complete transcription so you can kill them while you're on antiviral therapy? And how do you do that without actually activating the T-cell? Because you can't do use broad spills. You know, you can't you, IL-2 has been tried and it and it's toxic. You can't use OK-T-3 or something like that to activate every T-cell. So Mike, that's been a really big interest of mine. Measuring and understanding RNA transcription and then how do you get that to get that going while someone's on antiviral therapy without activating the T-cell. And we've tried a million of one different ways and some of those, most of those approaches have been not HIV-specific, like histone decedalase inhibitors, if you, because you feel, alter the epigenic environment, you can fire off the virus. But none of those approaches have been HIV-specific. I've led clinical trials looking at them in vivo, not that effective, get a little bit of RNA, but no T-cell death. But over the last few years, we've got some really exciting work using HIV-specific approaches and mRNA, and I can get into that later. So what is going to work potentially for care, right? We've looked at vaccination. That's been a real bear. I think we've all been hoping for that and that's just been rough. What do we think is going to work? Yeah. Lots of things being tested. Lots of things looking promising. And the prince of samples of trying to find a cure. We haven't talked much about the immune response, so I'm able to get to that in a minute, but the principles are target the virus or target the immune system. Reduce the pool of infected cells to a small as you can get it or to zero. Some of the approach that I use, use by activating the virus or using pro-optotic drugs, which for needle clacks because these likely infected cells express high levels of survival proteins such as BCL-2. So there's been a lot of work on inhibiting pro-survival proteins in cancer, such as BCL-2 antagonists. A Melbourne-based discovery from Wee High. Now a license for the treatment of chronic lymphocytic chemit. For example, pro-optotic drugs will shrink the reservoir. We've got a clinical trial underway looking at that. The flip side is to boost immune control, whether it's T-cell mediated, N-K-cell mediated, or antibody mediated. And as you rightly said, obvious way is therapeutic vaccination, but that hasn't really worked. There's been one or two studies that look marginal at best, but it's really hard to re-educate those existing HIV specific T-cells or generate new functional HIV specific T-cells. It may be possible. Vaccination hasn't done it yet. The areas that look promising to do that are using different forms of immunotherapy. So one form that I've been very interested in is anti-PD1. So your listeners will know lots of anti-PD1. In fact, P-1 was identified as an immune exhaustion marker very early on initially of course in lymphocytic cytomegalovar in L-L-C-A-V, but very shortly after identified in chronic viral infections as being elevated in your viral specific T-cells, particularly HIV, but then shown in hepatitis B, hepatitis C and other human infections as well of course as in cancer. So in clinical trials of anti-PD1, there's now emerging a few of these studies when anti-PD1's given, we've done my own lives and a lot of work on when you give people with HIV with cancer, anti-PD1, we just did opportunistic observational studies. But when you give people HIV on anti-retro-therapy, anti-PD1 and stop treatment at the same time, so you're giving antigen exposure as well as an intervention to reverse T-cell exhaustion, there is some initial promising results that a subset about 20% of participants can control virus after receiving a short course of low dose anti-PD1. So we know that, and actually in monkey models, other work, we've done together with Affa McCoy and Lewis Picker at OHSU shows again, if you give the anti-PD1 at the time of stopping antiviral therapy, not while on antiviral therapy, but there's no antigen or very little antigen around, you can re-educate the existing T-cells to no longer be exhausted and functional and you can lower viral load. So there's quite a bit of work going on anti-PD1, we're currently doing a clinical trial here and soon to open in Singapore using low dose anti-PD1. Of course, the problem with the PD1 is immune-related adverse events which are acceptable in someone that has cancer but not in people with HIV. So that's one form of immunotherapy. And other form that had meant several clinical trials now, about five that have shown some efficacy is to give antibodies. And the antibodies that have been tested are broadly neutralizing antibodies. I think people will understand what that is, but in brief, some people with HIV make very good endogenous antibodies that can neutralize a wide range of variants. And if you isolate the B-cells, some of those people, and clone the right genes and you can manufacture broadly neutralizing antibodies, there's been a large number of broadly neutralizing antibodies described, several that have reached clinical trial and two that have been licensed to Gilead. And when you give those broadly neutralizing antibodies at the time of stopping antiviral therapy, in some participants you can also induce control. The virus is still there but it's controlled at low levels. So they look quite interesting and now people are using combination immunotherapy, recent paper and nature from a group at UCSF showing that if you give a combination of immunotherapy vaccine broadly neutralizing antibodies, TL and Inaiginous, they could induce control, not to the level that we need, but it's that you can shift the dial of immune dysfunction. And one last area that I think is really exciting is gene therapy. And there is a whole lot of ways gene therapy's been tested to actually CRISPR-Cas9 to target the virus. Clinical trials not yet shown to be effective. Insertional gene therapy to insert a gene of a B-NAB into the host to produce antibodies ongoing that's been done successfully in adults, but really promising in infant macaques because the gene is persistently expressed and basically the virus can't come back because the person is making their own indigenous, endogenous antibodies. And gene therapy like CART cells and also this, I mean, the work we're doing with mRNAs is essentially ultimately going to be a form of gene therapy. So there's lots of things, literally exciting stuff that's been tested. Or are you going to just get a bone marrow transplant? Yes, CCR5 Delta. Yeah, I mean, of course. Yeah, that is worth mentioning because it's proof of concept that the reservoir can be wiped out. And actually, in those cases, now nine cases reported around the world, not all with interestingly requiring a CCR5 negative donor, two of the nine have not had that one, had a wild type donor one, had a zygus for CCR5. You truly wipe out your reservoir and that's a mix of grass versus host disease, the conditioning treatment and having a new marrow with cells that you can't infect. So that's inspired many new directions of treatment. For sure. So it's great to see there's so many different avenues for treating this very elusive pathogen. I think that's all what we have time for now, but we just want to ask you one quick last question. So we like to ask our guests something to get to know them a little bit better. And our favorite question to ask is if you were not, you know, a more renowned HIV scientist, what do you think you will be doing with yourself? What is your, what would have been your other, your alternative universe? Yeah, well, I had always wanted to be an astronaut actually. I was really interested in physical science, love, physics and maths at school, kind of went into medicine, not terribly interested in medicine to be honest, but grew to love it. In Australia, you go straight into your chosen field or did you do my day, you don't do a free arts degree first. Yeah, I would be an astronaut and I still look at an engineer, you know, when I look at these massive, you know, big bridges, I think, wow, I would have loved to have built that. So I think astronaut or engineer. Sounds great. That was a great answer. Maybe you'll send an experiment to space one day, you know? It might affect the borough reservoir you never know. Indeed. All right. So it was great to have you. We had with us Sharon Lewin from the Peter Daharty Institute in Melbourne, Australia. Thank you so much for joining us. It was a great conversation. Thanks very much. Now bring us to the end of the first show. Don't forget to subscribe to our newsletter at immunogypodcast.com to get the show notes, including episode summaries and links to all of the interview and random papers. If you enjoyed the episode, feel free to share with a friend, colleague or social media. You can also reach out to us on X, at immunoportcast, [email protected] or via email at [email protected] with feedback or to suggest guests. See you next time.