nm0607: right then okay that's great yeah so i said in Finland about thirty per cent of cases are only thirty per cent of cases are acquired out of country and the rest acquired in country so the next thing i want to show you is the it says the situation in the U-K er current situation in the U-K er that's a bit grim er i was just going to explain you've got them in your handout sm0608: yeah sf0609: u-huh nm0607: now i haven't put them on this copy i can't get onto my hard disk it's er let's shut this off a minute and we'll talk about that when we move on nm0607: so if we look at the first table this this gives you the most up to date information for the U-K okay and what you can see is cumulatively at the end of last year about fifty-two-thousand people had been diagnosed or fifty- three-thousand almost fifty-three-thousand down in the bottom right-hand corner had been diagnosed with H-I-V and of those roughly thirty-thousand were homosexual spread men-men and roughly fifteen-thousand so slightly under a third were heterosexual spread and then intravenous drug abuse comes next and then a relatively small number from blood products about a thousand just under a thousand mother to infant transmission and then a couple of thousand where it's not quite clear how the transmission occurred the thing that you should notice along the bottom is that up until around about ninety- ninety-seven the number of newly acquired infections each year is relatively stable and then it starts to accelerate again and in fact in the period September two-thousand-and-one to September two-thousand-and-two there's been some five-thousand-three-hundred new infections diagnosed so you can see that after a period of about ten years of relatively stable new infection rates the epidemic is in this country is increasing again not dramatically but it is going up at the rate of roughly fifteen to twenty per cent increased incidence a year and if you look at table two what table two shows you is diagnosis by exposure category for just for one year just for the last year September two-thousand-and-one to September two- thousand-and-two and you can see that this sh-, this table shows you two things it shows you the distribution according to what type of category the infection was in so men-men and heterosexual spread and various subdivisions of heterosexual spread and you can see in there the figure that shows for heterosexual er s-, er spread acquired abroad no evidence of a high risk partner okay acquir-, U-K acquired no evidence of a high risk partner and you can see it broken down by region and the thing i want to come out of the broken down by region is you can see that both in terms of the acquired infections last year and the total number of infections acquired London is an epicentre yeah and then the final table i've given you is again year is is more total figures this is year of infectio-, year of infection over the last ten years and the area where the infection was acquired or was diagnosed in fact not necessarily acquired and again what emerges from that is you can see that across the total epidemic of the fifty-odd-thousand cases some were over thirty-thousand thirty-two-thousand were acquired in the London area what that's telling you is even in the epidemic in this country the the risk varies according to where in the country you are okay and that would be true in most countries risk is not uniform okay and it's it's a it's an important message to get across to you okay so you can see the situation globally is we've got some forty-million people infected but actually the U-S-A the U-S the U-K's contribution to this forty-million is pretty small it's only fifty-two- thousand in fact it's less than fifty-two-thousand really because you're talking about a significant fraction of the fifty-two-thousand diagnosed cases in this country will already be dead i can't remember what the total is it's around about thirty-thousand of them have already died so we're only contributing about twenty-thousand between twenty and thirty-thousand to that forty-million figure in this country okay all right that's all i'm going to say about the the epidemic okay the important message you've got to take across about the epidemic is it's a c-, huge global problem it's still an escalating grobal problem okay the numbers are going up rapidly they are not stable or going down okay and it's predominantly a problem in the developing world particularly sub-Saharan Africa where you've seen from some of the incidence figures i showed you in the last lecture that there are quite frightening consequences for social structures in some of those countries you know er less of a problem in the developed world more under control in the developed world more under more un-, control more under control still in this country most of the spread in this country is still homosexual spread although heterosexual spread is the most rapidly growing category and most of that heterosexual spread is infection acquired out of the country so by somebody going from this country and having a sex partner in a country where the generalized epidemic is a-, is going on at a high level rather than spread within the country all right what i want to do now is move away from talking about the epidemic in a broad sense and start talking about the virus okay and the infection so we have another chunk of handouts and i'll try and get this up while you hand those around if i can find me pointer again i've put the bally thing down here we go nm0607: right i hope you will already have seen a v-, a version of this sort of slide maybe not a precisely this but a version of this so this is the virus we're talking about H-I-V H-I-V is a retrovirus to remind you what that means is that is that unusually for a vir-, oops let me back up here oh bother unusually for a virus it has a diploid genome there are two pieces of single strand positive sense R-N-A contained within the virus particle the R-N-A is approximately ten kilobases in length just under ten kilobases in length it is it is surrounded by a capsid structure composed of a number of proteins P-twenty-four being the major protein and when H-I-V is diagnosed it is in fact antibodies against P-twenty-four that form the main basis of diagnosis so the bulk of H-I-V diagnosis does not involve looking directly for the agent itself for looking for the virus itself that usually comes as a confirmatory test the bulk of diagnosis is looking by looking for antibodies against this major structural protein P-twenty-four that makes up the inner capsid shell this capsid shell has a toroid type of structure a sort of bit like a a flattened ended cone m-, on the R-N-A is the reverse transcriptase enzyme this is a retrovirus so which group in the Baltimore classification scheme is this in sm0610: six nm0607: didn't hear it very loud sm0610: six nm0607: six that's right six so it goes through a D-N-A intermediate so the first thing that it's got to do when it gets inside the infected cell is convert its single strand positive sense R-N-A into duplex D-N-A and it's transcription from that duplex D-N-A that gives rise to the viral messenger R-N- A the toroidal capsid is surrounded if i can ever find my pointer again there we go is surrounded by matrix protein shown here in green that's then surrounded by a lipid envelope so this is a lipid containing virus and embedded in that lipid envelope is the envelope protein of the virus and the envelope protein is synthesized as a precursor called G-P- one-sixty the G-P standing for glycoprotein because this envelope protein is a glycoprotein and after synthesis G-P-one-sixty is cleaved to produce G-P-one-twenty which forms the head of the envelope protein sticking outside the lipid envelope and G-P-forty-one which is kind of like the stalk that through non-covalent interactions holds the G-P-one-twenty in place and the G-P-forty-one is a transmembrane protein it it goes through the lipid bilayer membrane okay down here at the bottom is the gene organization of this virus and it's like any other retrovirus it but has some additional genes what genes do normal retroviruses carry sf0611: gag pol and env sm0612: gag pol and env nm0607: gag pol and env and you can see here gag pol and env okay but H-I-V is unusual in having a number of othe-, additional proteins usually referred to as accessory proteins and the degree to which we understand what these accessory proteins actually do for the virus varies according to which protein we are talking about so for example you will already have heard in this lecture series quite extensively about tat and rev tat and rev are involved in the regulation of gene expression by this virus okay but you won't have heard anything yet for example about vif okay vif is another accessory protein that overlaps the carboxy terminal end of the coding region of the R-T gene the polymerase gene and the amino terminal region of the V-P-R gene and vif stands for virus infectivity factor it's the protein that m-, of H-I-V that the limited amount of H-I-V work that i do that's the protein that we work on vif is an interesting protein in that as the name implies it's required for virus infectivity and if this protein is absent and you try and grow virus in the normal host cells for this virus which are C-D-four-positive lymphocytes then the progeny virus that is produced is non-infectious it turns out that vif is actually required to overcome a normal cellular protein that's an inhibitory factor for H-I-V replication and i don't have time to go into the detail and anyway the detail is not pertinent to the rest of what i'm going to say so there are a number of accessory proteins down here and three major normal retrovirus proteins gag which m-, is a er is made as a polyprotein initially called er P-R-fifty-five 'cause of the fifty-five kilodalton precursor and that precursor is cleaved through the action of a virion encoded protease gene that undertakes the major cleavages necessary to convert P-R- fifty-five into P-seventeen P-twenty-four P-six P-one P-seven a number of structural proteins that make up this capsid shell here that i'm pointing to okay so that's the virus we're talking about let's move on then to look at the pattern of this infection now you can divide H-I-V infection into three broad stages there's the primary infection which occurs over a few weeks there's a long period of what is usually called clinical latency and then there's the terminal stage of disease which we usually refer to as AIDS and the important point to see down here is the scale you can see that the primary infection occurs over a matter of weeks the latent period can be years there are certainly people around who have been well for more than a dozen years and then for some reason that's not entirely clear gone into full-blown AIDS the point about this is once you go into AIDS you are going to die okay you may you may be it may be possible to hold you through using antivirals that i'll talk about in a minute in in some sort of semblance of reasonable health for a period of time but for example when A-Z-T zidovudine the main R-T antiviral inhibitor was u-, used extensively in the United States in monotherapy it improved your life expectancy as an AIDS victim from ten months to twenty months so it had an effect one shouldn't underestimate its effect but it didn't mean that you were going to survive for a long period of time and have a natural lifespan okay i want to talk a little bit about the division of these different er stages of the disease by symptomology and this really deals with the the clinical pattern of disease okay and i want to keep referring back to this as i talk about the clinical pattern of disease okay now of course once people started to diagnose H-I-V it became important to have available to clinicians some sort of definition of what stage of this process a particular patient that might present to them was at okay and two systems grew up quite quickly one was proposed by the C-D-C the Centre for Disease Control remember the place in Atlanta i said that is the sort of American equivalent of the P-H-L-S okay and the other grew up through a major hospital in the United States in Washington called the Walter Reed Hospital now the Walter Reed Hospital has a very long history of dealing with tropical diseases okay and these two er organizations proposed a staging system to allow clinicians to define when a patient presented to them what stage of disease that patient was in the C-D-C system defined people as being in stage one through to four and this was romanic one through to romanic four the Walter Reed system allowed you to divide people in a stages zero to six now it's important of course when a new disease comes along to have some sort of system of clinically defining the disease why is that [belch] important excuse me well it allows you to do surveillance studies that's the first thing it allows you to do it allows you to actually survey the disease particularly when you've got a disease that you know is going to is going to develop over a long period of time it allows you to survey its development it allows you to do epidemiological studies what is the incidence of infection and of course it will if you've got some sort of therapeutic intervention metha-, measur-, measure method it will allow you to measure how how good that therapeutic intervention is now these two schemes the C-D-C scheme and the Walter Reed scheme when they were first proposed in the middle nineteen- eighties they were both used they each have advantages and disadvantages the C- D-C system is largely based on clinical observation of the patient so basic simple clinical observation of the patient weight er symptomology okay very little lab very little involvement of lab indicators or immune system indicators by contrast the Walter Reed system is ba-, is mainly based on laboratory diagnostic assays now on a global scale the C-D-C system took over relatively quickly from the Walter Reed system and the main reason for that was because the disease grew rapidly in countries that were not well set up to do the laboratory diagnostic assays that could easily be done in the United States and so the C-D-C system is the system that you will most often hear about today and is the system that's broadly used to define what stage someone is in so in this system then stage one is the acute phase of infection and this acute primary infection period is most usually asymptomatic so the person is infected but most commonly they have no idea that they are infected they they exhibit no symptomology if they do exhibtib-, er exhibit symptomology it's basically a flu-like syndrome they might get some fever they might get a bit of nausea they might be a little bit lethargic perhaps a little bit of diarrhoea a sore throat et cetera but nothing that's very specific i mean there are lots of things that would cause that you know a bad night on the bevvy would cause most of those symptoms okay so in the acute phase there really er ev-, if there's any symptomology at all it's nothing that you can kind of put your finger on and say ah you know i know this person is probably infected with H-I-V because they've got this symptom okay the only lab indicators you get in this acute phase are a transient leukopenia and lympha-, lymphopenia so a transient drop leukope-, penia means drop basically so a transient drop in leukocyte numbers and lymphocyte numbers you might get an inversion of the ratio of C-D-four to C- D-eight cells in the bloodstream but it's important to realize that at this stage in the fect-, infection that is not due to a drop in C-D-four cells it's due actually to an increase in C-D-eight cells okay you may see some atypical lymphocytes in blood smears but you may not okay so the picture i'm painting then of stage one is somebody who's infected probably has no idea they're infected has no symptomology okay and will take somewhere between a few days and as long as three months to seroconvert now you remember i said to you that when people are diagnosed as being H-I-V positive the main form of diagnosis is seroconversion the production of antibodies against one of the structural proteins of the virus so in the period up to three months after the person has been infected there are probably no indicators either to that individual through symptomology or indeed to the health authorities through some sort of diagnostic assay that they've actually been infected unless the diagnosis is looking specifically for virus the reason for that is as you can see from the virus count here in the blue line it is during this period that virus titres in the bloodstream are probably at their highest level until you get right to the terminal stages of disease okay so what does that tell you about this individual in terms of societal risk sm0613: they're at their most infectious nm0607: yeah and sm0613: they don't know nm0607: and what does that mean for society sm0613: that you're going to get a lot of spread nm0607: exactly it's people in this phase here that as far as society is concerned are the greatest danger to society okay because these people don't know they're ill don't know that they've become infected are probably con-, going to continue in the lifestyle that they had prior to getting infected and so are probably going to continue to do the very acts that resulted in them being infected and so are very much more likely to infect other people and they're particularly likely to infect other people because they have the highest level of virus in their bloodstream so they have the greatest chance at this point of passing on the infection okay as far as seroconversion is concerned okay what is the first antibody you would expect to detect after a seroconversion what are the main classes of antibody that you get in the bloodstream there are three huh sf0614: I-G-G nm0607: I-G-G's one sm0615: I-G-M nm0607: I-G-M's two what's the third one sm0616: I-G-N nm0607: I-G sm0616: N nm0607: okay so which out of these three then are you most likely to detect first after infection sf0617: I-G-M sm0618: I-G-M nm0607: are we sure about that sm0618: nm0607: yeah sf0617: yeah nm0607: well you're right what happens with I-G-M remember is I-G-M is the antibody that's initially produced to an infection it rises very rapidly you can often detect an I-G-M response in a few days in the case of H-I-V you may un-, you may intec-, detect an I-G-M response in as little as five days post- infection if you go looking for it it peaks at about twenty-four days plus or minus seventeen and it disappears it goes back down again remember I-G-M drops away again and it disappears by day eighty-one plus or minus twenty-seven days so if you go looking for I-G-M to H-I-V four months after infection you won't find it right it's gone I-G-G can be most early detected about eleven days so almost two weeks after initial infection it doesn't peak to a hundred-and- thirty-three days plus or minus sixty-three days so it's about three months after the person's infected that I-G-G the stable long term antibody response that you will see in a human peaks okay so that's all i'm going to going to stay about stage one other than to say that you must notice that what happens at the end of stage one as far as the virus titre is concerned is that it drops and you should remember that this graph over here the virus titre is a log scale so it's a it's it's a little bit misleading to look at this graph and think oh well it doesn't actually go down very much it drops about a hundredfold to a thousandfold in terms of titre that means that at the end of the acute phase the person is going to be a hundred to a thousand times less likely to transmit the virus than they are at the peak of the acute phase this drop in virus is as a response of the immu-, is is comes from the immune response that has been activated against the virus both a humoral and cell-mediated immune response that is able to some degree to get the virus under control and eliminate it but the crucial thing is it's to some degree like all persistent virus infections the immune response in this case is not able to completely eliminate the virus it gets it under control but it doesn't eliminate it okay so that takes us from stage one then into stage two now stage two of infection is this period of what is usually referred to as clinical latency now what you can see in clinical latency is that first of all it can be very long okay it can also be relatively short so of course when it was realized that this period was of variable and somewhat indeterminate length the first thing that people started looking for were prognostic indicators was there any indicator during this period that would tell you how long it's going to last and why would that be important well it would be important because during this period the people are well they're not a-, they're not exhibiting any disease symptoms they are well okay if you acquire the infection at twenty years of age and somebody sells you well according to your prognostic indicator you're not likely to go out of this period of clinical latency for fifty years you're not going to worry about it too much right 'cause you're probably going to be killed by something else before you get to seventy yeah but if somebody says to you according to your prostic-, prognostic indicators your clinical peri-, period of clinical latency is going to be two years then you're going to start you know living life and spending money pretty quick because in five years you're going to be dead probably in four years you're going to be dead okay i i've i've laid it out in a in a dramatic fashion so that you realize that there was an enormous amount of pressure in the mid-eighties to try and come up with prognostic indicators because that's what people were worried about i am sick doctor you know i am infected with something doctor when am i going to get sick is the question that was being asked okay now what you can see that is going on during this period is there is a very slow but almost imperceptible rise in the viral load the level of virus in the bloodstream okay but at the same time there is a clear drop going on in the level of C-D-four-positive lymphocytes in the bloodstream and in fact the the first sort of indicator that people started to use were this level of C-D-four count i should just back up a second and just tell you a little bit about in the in the epidemic in the United States which was the e-, area where the long ter-, first long term studies were done they started by looking at about seven-thousand homosexuals over a ten year period yeah so the first ten years from the from the early nineteen-eighties through to the early nineteen-nineties and in that ten year period thirty-six per cent of them thirty-six per cent of the people had developed AIDS within that ten year period forty-four per cent of them were showing symptoms of going into AIDS by the end of the ten year period so these were people who were recruited early they were already infected early in the epidemic and followed over ten years so by the end of that ten years somewhere close to eighty per cent of them were already showing symptoms of going into disease but twenty per cent of them one in five were completely asymptomatic at the end of a ten year period and this is in the period where there was really virtually no er antiviral immuno-, er antiviral therapy going on okay now prognostic indicator C-D-four counts people in the early phase of the next stage stage three now stage three if you look at the recent literature stage three has kind of fallen into disrepute it used to be a period where people were said to have what's called either ARC AIDS Related Complex or P-G-L Progressive Generalized Lymphoadenopathy and in a sense what it was measuring was people starting to tip over into AIDS and one study for example looking at homosexual men who were already in P-G-L so were already at the end of stage two beginning of stage three followed them over twenty months so only two-and-a-half years and if their C-D-four count at the beginning of that twenty months was less than two-hundred per ml by the end of the twenty month period sixty per cent of them had progressed to AIDS by contrast if their C-D-four count was greater than three-hundred-and-fifty per ml only ten per cent of them were in full- blown AIDS sm0619: sorry what was the percentage of the first one nm0607: sixty sixty per cent of the people after twenty months were in full- blown AIDS if their C-D-four count at the beginning was this level and only ten per cent if it was this level it's important to point out to you that in these early studies there was a lot of controversy because people were not used to measuring C-D-four counts in humans and it took a little while to realize that actually your C-D your C-D- four count actually has a daily rhythm it goes up and down each day so of course if you were mea-, er d-, the count you were getting would depend on when in the day you measured it so there was quite a lot of confusion in the literature 'cause people were quoting different figures because they were measuring the counts at different times of the day okay once that was figured out once the diurnal rhythm of C-D-four counts were was figured out of course they started measuring at the same time each day so they could get comparative data so what about so that's stages one two and three and as i've said to you three has largely fallen into disrepute that takes us on to stage four stage four is what is now commonly referred to as full-blown AIDS how do you define the entry into stage four well three main criteria have been used the first is fever for persisting for more than a month involuntary weight loss at greater than ten per cent of baseline so this is not somebody going on a diet and managing to lose one stone in ten because they're on a diet this is somebody losing one stone in ten without trying okay and diarrhoea for more than a month and you've got to have all of these symptoms without any other concurrent reason other than the fact that you're infected with H-I-V so it's not just that you've kept on going to the same Indian restaurant and eaten you know a pretty nasty meal that's been giving you a you know bad diarrhoea for a month and you've not learned you know you'd better change your restaurant i mean it's it's you haven't got any other reason why this is happening to you other than that you're infected with H-I-V okay let's ask something about then the viral dynamics that are going on during these different phases if we look at the virus what's going on in in er the primary infection phase is the virus is growing flat out there's no immune response there of a-, of any s-, consequence the virus is just growing in a completely unrestricted fashion it has a doubling time of about ten hours peak viraemia will occur at about three weeks and each infected cell is going to seed roughly twenty new cells to become infected but the last sentence is quite important the virus load starts to drop rapidly as the immune response is activated so you should not be under the impression that the immune response that we amount to H-I-V is completely useless it's not it does a pretty good job at controlling the initial acute infection it reduces the viral load between a hundred and a thousandfold okay the only problem is it doesn't completely eliminate the virus during the asymptomatic phase you have something like ten-to-the-ten virus particles being made every day and you have something like ten-to-the-nine C-D-four-positive lymphocytes being made and eliminated every day so you can see that virus replication and elimination because remember if a C-D-four is cell is eliminated you're going to eliminate the virus that's replicating in that cell you have a rough balance here and this is sometimes referred to as the steady state what that means is that the whole infection is actually being sustained by only about ten-to-the-six to ten-to-the-seven ce-, T-cells in the body these are productively infected activated T-cells the si-, the size of the latent H-I- V reservoir okay is mostly in resting T-cells and it's about similar in size it's important to point out to you just to remind you that when somebody goes into stage four the immune system loses control of the virus replication again and virus replication takes off and so in stage four there's again a s-, the previo-, one of the previous slides showed you a viraemia a strong viraemia okay a lot of virus in the bloodstream a high chance of potential virus spread if the individual was indulging in activities that would be likely to spread the virus but remember there's a big contrast between somebody who's in the acute phase and somebody who's in the symptomatic end phase this is essentially a sexually transmitted disease if you don't know you're infected as will be the case in the acute phase you will be undertaking your normal sexual activity be it you know once a day once a week once a month once a year okay if you're in late stage AIDS you're not interested in sex i mean sex is the last thing you've got on your mind you know you've got on your mind coping with the symptomology that you're suffering from rapid weight loss you've got diarrhoea you've got fever as i explained to you on the first lecture you might have an opportusisti-, opportunistic infection like athlete's foot up to the knee it's sym-, in symptom terms it's a very unpleasant er end stage infection and so actually people in full-blown AIDS are not a major risk to society they might be a risk to the people who are actually treating them and the people who are treating them have to be careful that they don't come into contact with blood remember these people may be bleeding from a number of orifices but they they don't pose a large risk to society okay my time's up i'll stop there and continue next Tuesday sf0620: mm-hmm nm0607: tuesd-, Tuesday i think it is okay