COVID-19 and the immune system

Does infection confer immunity? Is the virus mutating? How long could immunity last? Arne Akbar, Professor of Immunology at UCL, answers some of the big questions surrounding the pandemic.

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Transcript

This transcript was automatically generated using speech recognition technology and may differ from the original audio. In citing or otherwise referring to the contents of this podcast, please ensure that you are quoting the recorded audio rather than this transcript.

Jessamy: Thanks for joining us for another special episode of The Lancet Voice. Today we're going to be talking to Professor Arne Ackbar. who is a professor of immunology about their recent report that the Academy of Medical Sciences has released in collaboration with the Society of Immunology. 

Gavin: Yeah, it's really exciting to have them as a guest.

Just before we start, Jessamy, just give us a little summary. What do we know about how the immune system reacts to COVID 19? 

Jessamy: What we do know is that the immune system seems to respond very strongly in some patients and to go into overdrive, which makes some patients very sick. The interesting thing about this particular report is that it brings together a whole group of different types of specialties and different types of scientists, virologists, immunologists, who come together and try and really Note down what it is that we do know and what it is that we don't know.

Arne: My name is Professor Arne Akbar. I'm a professor of immunology at University College London. I'm also the president of the British Society for Immunology. Three weeks ago, Professor Sir Robert Leckler asked me to chair a task force with the joint input of the British Society for Immunology and the Academy of Medical Sciences.

to try to find a way that we could put together all the information on immunology on COVID 19 that's available. And this went across a range of expertises, all the way from immunology to virology to vaccinology. So we convened by putting together a group of individuals, all with very big track records in their fields of interest, to get together and to decide what is known, what is not known about the disease.

Jessamy: That's great. And it's a really fantastic report. And I wondered whether, first of all, we might just touch on something that I found particularly interesting reading the report, which was about this sort of concept of mutations and that, there are over 2, 000 known mutations of the COVID 2 virus.

What are the implications of that for the clinical picture? Is there a sort of link to severity? And what does it mean for our understanding of how the virus was introduced to say the UK or other countries? 

Arne: As I say, with the group of people we have together, we have specialists in immunology, virology and other things as well.

Not any one person is a specialist in all the areas. But we wanted to get people together to find with the best minds on that particular topic, what's going on. And it's fair to say right now, there are many things we don't know about. We don't know about the mutation rates. The virus could mutate into a non pathogenic form as has been shown in some other diseases, or it could mutate in a different way.

This just highlights the need for ongoing research into this. But we right now at this stage don't know the answer to that question. 

Jessamy: But we know that the virus is mutating. 

Arne: From research that's going on right now, it's not so much known at this stage if it's mutating. It's known that if you use the parallel with other cases of different viruses, that there will be some mutation.

We don't know the rate at which it's mutating. 

Jessamy: And we don't know whether that would mean whether some cases might be more severe or not because they've got a different strand of the virus. 

Arne: We really don't know that, the answer to that, but it's a very important question. 

Jessamy: And how will we know the answer to that?

What is the sort of study that we need to be able to give us that evidence? 

Arne: We need to be able to collect the virus from different people, with different stages of the disease. People at the earlier stages who have mild symptoms, patients who've got very severe symptoms, and then the virologists need to actually examine the virus to find out whether the same virus is causing all the problems, or slightly different variants of the viruses are doing that.

And that is ongoing, but we don't know the answer to that yet. So 

Jessamy: we're waiting for that evidence, and that kind of a study on a large scale will be able to tell us that. 

Arne: Yes. And also the virus in different countries. Is it the same virus or is it slightly different variants of the same virus? All this data will become available in due course.

Jessamy: And just speculating on that a little bit, obviously we don't have the data so we don't know, but what's the kind of understanding or expectance from your group of experts? 

Arne: We, like everybody else, we're just waiting for the right groups to do the research. Not everyone on the group is actually working on the same thing.

We have the virologists, we have the immunologists. We have people working with other aspects of the immune system, and it's a worldwide effort. It's not just the UK task force. The research effort that's going on is worldwide. What we were trying to do with this group, but to bring people together, at least in the UK, with different expertise, all with an interest that could inform about COVID 19 and try to put together a schedule, what is important, what is known, what is not known, and try to find a way forward, but go forward in a concerted way.

rather than each different group doing a bit of research, but not joined up so no one knows about the research they're doing. 

Jessamy: Yeah, that's great. That kind of comprehensive initiative is certainly needed. So perhaps we might talk a little bit about infectiousness and infectivity. In your report you write about whether the sort of the dose of the virus an individual is To may potentially influence their disease severity.

Could you just talk us through some of that thinking? And if there is any evidence behind that at the moment and what some of the implications are. 

Arne: So the evidence that the dose of virus might be important comes from healthcare workers. So if you take the original example of the Chinese doctor who first publicized the fact that there was the new disease going on, he wasn't in a group with comorbidities, he wasn't in the older age group, but he was exposed to a lot of virus, without probably appropriate PPE at that stage, and he got sick and he got the virus and died.

A lot of people, healthcare workers, who don't have ostensibly any comorbidities, they're being exposed quite strongly to the virus. And that also suggests that if you have more exposure, the amount of exposure you've got may actually dictate the outcome and the severity. But it's anecdotal right now.

There's fairly strong evidence, but it's still anecdotal to some extent. The bigger the exposure, the worse the outcome. 

Jessamy: And what is the evidence that we need what's the study that we need that we'll be able to show that, as the the pandemic goes through different countries we'll get more evidence about healthcare workers and their exposure rates.

I know in Italy, at one point it was 20 percent of healthcare workers, but what sort of will be the When we say, okay, this is no longer anecdotal. This is a sort of, this is a definite association. There's some causal implications here. 

Arne: Which is one that's unethical. You give people different doses of the virus and look at the outcome.

So we can't do that. What we can do is use animal models with coronavirus infections, something very similar to the COVID 19 virus that we were investigating now. And in an animal system, which closely resembles what's going on in a human, we can ask the question about dose of virus and severity. 

Jessamy: And so then just moving slightly on to immunity, does infection with previous coronaviruses confer any kind of immunity?

And what might that mean? What might that look like? 

Arne: This is a very interesting question and one that many people are quite fixated on for good reason. And the honest answer is at this stage we don't know. We'd like to think there might be some protection that you might get from previous coronavirus infections.

Coronavirus is one of the viruses that causes the common cold, for example, but how much protection there is and how much cross reactivity there is between the virus that causes a mild cold or one that gives you severe disease is really not known. One possibility, which people would like to think, is that the people with mild symptoms might be ones who've got cross reactivity, but once again, we really don't know that.

Jessamy: And what do we need there to be able to find that out, or what's underway in terms of the research that's looking into that? 

Arne: What we could do is to follow the virus strains, the COVID 19, that SARS CoV 2 in people with mild and severe disease. And we could look for antibodies specifically against SARS CoV 2 and antibodies against other coronaviruses if the reagents are available.

And then in laboratory tests, you can see whether they actually cross react to the same part of the virus in SARS CoV 2 or not. So these are very much laboratory based tests that you could do that. 

Jessamy: Could you explain to us antibody dependent enhancement and what the relevance for that is with regard to vaccines?

Arne: In certain diseases, having antibody, preformed antibody, is actually detrimental, and that is probably because the antibody helps to let the virus actually enter the cell more quickly, or infect the cell more quickly. And one example of that is in dengue virus infection, where people who get it the first time, they recover and they, it's seemingly okay.

If they get it a second time, they put antibody and the antibody can bind to the virus. And that's in some mechanism, which is not totally understood, makes the virus more easily accessible for infection. So that antibody there actually enhances the infectivity of the virus. The second time around. 

Jessamy: And what does this mean for vaccines with regard to SARS CoV 2?

Arne: So this was a big worry but I think it's less of a worry now. Emerging data suggests that this may not be a big issue, antibody enhancement in SARS CoV 2. But obviously with some viral infections it is and that was, people were right to actually raise this as a possible cause for worry. But the emerging data right now suggests that this is not a major cause of concern.

Jessamy: And in your report you, you refer to the correlates of protection when you speak about immunity. What's meant by this exactly? 

Arne: When you have an infection, the immune system is not one agent working against one, one organism. The immune system consists of many multi layered parts, all of which actually collaborate together.

You've got the cells that make the antibody, but in order to make the antibody, these cells need to get a bit of a prompt from other cell types, but there are other cell types as well that can actually recognize and kill infected cells. You also have lots of protein mediators that are secreted by cells that can actually have direct antiviral effects.

Now what is not known is which of these are most important for the protection. virus. It might vary from person to person. There's evidence that some people who've got the virus, because you can detect the virus, don't have very much antibody, implying that maybe other parts of your immune system might be taking care of that individual.

So we need to know what's more important. Is it the cells themselves that combat the virus? Is it the mediators they produce? Is it the antibody? And how do these things work together? And so that's not really known, but by following samples from people with mild and severe disease, and also people throughout the course of the disease, from the initiation, all the way to the resolution, the end stage, where they're very much better, we can find out which parts of the immune system changes and the ones who have severe versus the individuals who have very mild disease.

And that would give us an idea of what correlates with the protection, hence the correlates to protection. 

Jessamy: And just talking about this kind of 20 percent of people who seem to show, almost no antibody response. What do we know from previous coronaviruses like MERS and SARS? 

Arne: There is a lot of evidence out about SARS and MERS, the SARS 1, the original coronavirus that became very prominent in our populations.

But we can't directly extrapolate because this virus is a little bit different. It causes more severity, for example, infects a different part of the airway. So this virus, SARS CoV 2, infects the upper airways, whereas SARS 1 was actually infecting cells lower down inside the lung. So we can look at previous data and say this might correlate, that might correlate, but really we don't know, and you maybe can't make that jump, and say definitively that what in the previous infections is exactly the same.

Jessamy: Do you think that it's fair to extrapolate any kind of implications for immunity from MERS and SARS that, some of that immunity lasted from months to up to 12 years in cases? Where are you on that sort of line about what we can extrapolate? 

Arne: If you were to think about this in an optimistic way, you would like to predict that maybe SARS CoV 2 is similar to the other coronaviruses that caused the problems and that you would have immunity.

But really at this stage we don't know. And we'd be optimistic and hope that you will have immunity. But until we do the actual studies of looking at people before and after they've recovered from the disease and looking longer term, like months or even a year afterwards, we won't know how long the immunity lasts.

And if the immunity does last, or doesn't last, what is the correlate? Is it with the antibody? Is it with the white cells, the T cells or other cell types that are involved? Or is it something else? Is it the interferons, the mediators that are secreted by cells? That's why we need to understand the correlates of immunity.

Jessamy: And so what is the difference between the sort of total measurable antibody and a protective virus neutralizing antibody? 

Arne: Virus consists of many proteins, and the immune system can recognize a lot of these fragments of the viral proteins. But which antibody will actually stop the virus from infecting other cells?

Which antibody can cause the ultimate destruction of the virus? That may not be the same as the antibodies that are generated against the virus. And so the antibodies that people are looking at now, which might be useful ones, are the ones that bind to the protein, the spike protein that is very much involved with the virus binding to these cells to infect them.

The idea being that if the antibodies can stop the virus binding to a cell, it will stop the cell from being infected. But there might be other antibodies to other parts of the virus that are also generated by the immune system, which might not stop the virus from getting into the cell, so you don't stop the infection.

So not all antibodies are the same. The ones that protect you are the ones that will stop the virus from causing the harmful problems, initially at least, by getting into the cell. 

Jessamy: And so which ones are we testing for at the moment, or which ones are the antibody tests? What do they focus on? 

Arne: The majority of antibody tests are antibodies against SARS CoV.

Most of them are against the spike protein. If you take the example of what part of the virus are people trying to generate an immune response to during vaccination, the majority of the vaccines that have been generated or been tested are against the spike protein. 

Jessamy: And in your report, you caution against, something that's had quite a lot of press, this idea of sort of immunity passports.

Could we discuss that a little bit more? 

Arne: As we discussed, because your immune system consists of many different parts that may confer the protection to you, it's not only the antibody that does this. In individuals that have potentially low amounts of antibody against the virus, you might still have immunity.

And so you could have your other cell types. And there are a multitude of different cells. I've just highlighted the few that are most well known. But there are many different cells that protects you in the body. You don't need the antibody. The cells are very active. And so if a person doesn't have the antibody, it doesn't necessarily mean they're not protected.

And that's a problem. You can't automatically view someone without the antibody as being someone who's at risk because they might already be protected. 

Jessamy: Yeah. And so that obviously has huge implications for people's ability to move around. society outside of 

In terms of maybe we could just talk a little bit about this sort of concept of people potentially being reinfected.

What is it that we need in terms of a study design to be able to show that people can't be reinfected? 

Arne: What we need to see are people who've recovered. And when they've recovered, what part of the immune system is very active? A lot of people are focusing on antibodies to the extent where there's a study that's just going on now in Southampton, where they're using plasma.

people who've recovered from the infection and plasma will contain a lot of antibody. They're trying to infuse that plasma into patients to see whether they can actually recover, whether you can actually pass the antibody from one person to another by this transfusion of the plasma from recovered patients.

And so there's studies like that going on, but it's very hard to do the direct test in a human. You can't reinfect somebody to see what happens. So we get to depend a lot on animal models that represent or show very closely what's happening in a human and then ask those questions there. 

Jessamy: Obviously, there's a lot of talk about vaccines.

There are lots of different avenues that are under investigation. What is it that we need to understand about the way that the SARS CoV 2 virus might mutate that has implications for a vaccine being effective or not? 

Arne: Something we haven't discussed yet, and this is really very important for SARS CoV 2, that is the vast majority of people who get severe disease are actually people who are older.

And if you then were to look further into the immune system of older people, it's very well recognized. that vaccination doesn't work very well in older people. Your immune system just goes downhill as you get older. And if it goes downhill, it's also very hard to re energize it after vaccination, which means that in SARS CoV 2, a vaccine might be very important to try to prevent the disease, but it won't work equally well in young and old people.

Which is why you need to consider other therapies to work or to be used in conjunction with the vaccination. This will include antiviral drugs, which are being tested right now. These also include drugs that might actually subdue parts of the immune system. Because in people with severe disease, there's an over exuberant amount of inflammation that goes on, part, cause in part by the immune system being uncontrolled.

And so you could use drugs to control the manifestation of the inflammation. You could use antiviral drugs and also vaccination. And what combination would you use for a person might depend on that person and how they're responding. And these are all unknowns, unfortunately, but a key factor in the whole disease is the aging aspect, the fact that aging and vaccination are not very good together.

Jessamy: So what does that mean for how we might be able to find a way out of this, that we would have to rely more on public health measures and treatment for this group of people, or that we'd have to get to a place where everybody was vaccinated? accept them and that might hurt immunity? What are the implications of that thought?

Arne: We need to make sure firstly that the virus has less impact on the population. So the measures like social distancing right now are really very important. If there's less virus around, there are less problems with people. We need to understand how we can boost the appropriate parts of the immune system in individuals.

We need to understand who's going to Act, who's going to get the disease more severely, and all the effort should be focused on those individuals to protect them, and obviously this will include the older population. Many of these questions are unknown right now, but this is why we have the research that's going on, and hopefully in a concerted way, to try to bring the appropriate people who know the answers, who are working towards the answers, but to all talk to each other.

This is a problem for this current infection. But after we have been through this one, the next hurdle is what will happen with the next one. And with the people and scientists working together now, we hope to actually find a way of addressing the problem. If another infection comes in to the system, how can we rapidly respond to it?

What are the questions we need to know as quickly as possible? What are the longer term questions? And hopefully this document, with the collaboration of all the people who put the input into this, is a roadmap into how to actually respond to a future threat, not just the current one. 

Jessamy: That's great, thank you.

Is there anything else that you'd like to say or speak to? 

Arne: Just to say that it's unusual for scientists to all get together and work closely together without thought of who's going to get the glory for the research. This is work that's been put together by a lot of different individuals.

Scientists are like mountain climbers. You want to climb the mountain first. You want to be the first one to the top. But in situations like this, you see the best of British science, where everybody collaborates. Everyone works together without too much thought of who's going to get the glory. There's a problem, we need to address it together, and the scientific community, which has been engineered by the British Society for Immunology and by the Academy of Medical Sciences, have come together to do this in a rapid way.

This might be a good formula for future threats. 

Gavin: So really fascinating to hear and some some really interesting points to, that kind of arise from your discussion, Jessamy. I think one of the things that's really worth highlighting is how vaccines affect different immune system ages. 

Jessamy: Yeah, I think it's interesting the point that they made about, the fact that we know that in an ageing immune system, then the response to vaccines is not necessarily as robust.

And that kind of coming into consideration when we're thinking about how a vaccine might be distributed and used to combat COVID 19. I think one of the most interesting things about that conversation was this sort of idea of some of the studies that we need to do to answer some of the key questions, the areas of uncertainty that we have in COVID 19.

and how some of them are basic science and some of them are clinical science. 

Gavin: Yes, and it's really, I wouldn't say intimidating is the right word, but it's really amazing to think how much of this is going to have to be done on extreme fast forward compared to how this kind of science is usually developed.

Jessamy: Exactly, the, as we've spoken about before, the kind of generation of knowledge at such a quick tempo and the interactions between basic scientists with clinical scientists to try and create new understanding for COVID 19 is a really fascinating aspect of this horrible situation that we're in.

Gavin: Yes, it's a really interesting risk reward balance, I think, in this particular case. 

Jessamy: Thanks so much for listening. You've been listening to another episode of the Lancet Voice looking at particular aspects of COVID 19. Please do let us know if there's any other content that you'd like to hear, COVID 19 or other related and you can find us on all of your basic platforms.