an autodidact meets a dilettante…

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Archive for the ‘ACE-2’ Category

Covid19: world progress, cytokine storms, our plans

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to be explored further

Canto: So while we need to be worried about – and to know something about – the cytokine storm that the Covid19 infection can lead to (and we’ll learn about that soon), there’s also a storm of activity on the SARS-CoV-2-fighting front.

Jacinta: Yes, intravenous zinc was talked about in the Medcram series as an effective tool in fighting viral pneumonia, and a world-first trial is being conducted by Austin Health and Melbourne University to test its effectiveness for Covid-19 sufferers with respiratory problems. We’re still catching up on the Medcram series, and update 52 talks of the drug ivermectin, already on the WHO list of essential medicines. The WHO website, incidentally, is promoting a ‘solidarity’ clinical trial for Covid-19 treatments, involving, singly or in combination, remdesivir, hydroxychloraquine, lopinavir, ritonavir and interferon beta-1a. So that gives some idea of the work that’s going on to fight symptoms and reduce the death rate.

Canto: And, you know, I’ve been feeling guilty about singling out the USA as the worst-case scenario all round. It’s not actually so. It’s not fair to look at total figures and point out that the USA tops the list for Covid19 fatalities, and draw calamitous conclusions. You have to take into account its much larger population compared, for example, to number two on the list, Spain. The US has suffered about 2.5 times the fatalities of Spain, but it has about 7 times the population. In fact, if you look at fatalities as a proportion of population, there are many countries worse off than the USA – namely Spain, Italy, France, the UK, Belgium (the worst hit), the Netherlands, Switzerland, Ireland and Sweden. All European countries, notably.

Jacinta: Yes and I’m sure they’ll all have their particular stories to tell about why this is happening to them, and will be wanting to learn lessons from Taiwan, Hong Kong, South Korea, and even our big faraway island, but I really want to look at solutions, in terms of eradicating the virus, or blocking it, or building up our immunity. Having said that, flattening the curve, and reducing fatalities, is a primary focus, which means continuing the physical distancing and looking for ways to keep economies running while this goes on. In spite of patches of civil libertarian activity here and there, the vast majority of our global population is on the same page with this, I think.

Canto: Well I’m looking at an Axios article from the Johns Hopkins website. It compares global performance under Covid19 to a mock pandemic exercise, Event 201, conducted some six months ago. They’ve found some positives and some negatives in their analysis. Positives – a greater degree of compliance with physical distancing measures than expected, ‘the degree of surge capacity augmentation in the health care system which has been possible’, and the rapid growth of international collaboration among scientists, leading to a quickened progress of trials for possible treatments. Negative – disparate and often contradictory messages from authorities – mostly political authorities – leading to confusion and distrust of governments and other institutions. This is partially explained by the complexity of the virus itself, which has made it difficult to characterise to the general public, and to be fully understood by non-medical authorities, such as political leaders.

Jacinta: It’s a weird situation, as there’s no end in sight, everyone’s worried about ending restrictions too soon, yet everyone’s worried about the economy, and those countries, like Australia, that are heading towards winter, are bracing for heightened problems, while northern hemisphere countries are hoping for summer’s relief but worried about the autumn when it might be hard to cope with a second outbreak, should it come. And medicos are warning that expectations of a vaccine in eighteen months might be overly optimistic. But I want to be optimistic – I want to look at anything that’ll reduce symptoms and save lives. One treatment, among many others it should be noted, is hydroxychloraquine, which is being given so much of a bad press, because of its being over-hyped by a Trump administration intent on getting political points for a silver-bullet cure. There have already been a number of small, less-than-gold-standard studies, some in which the drug is combined with the antibiotic azithromycin, and the results appear to be all over the place. We’re still awaiting the results of randomised, placebo-controlled, double-blinded studies, which are under way.

Canto: I note that a couple of reports on chloraquine and hydroxychloraquine on the JAMA website have been taken down, I suspect because of all the politicising. That’s a shame. Anyway I mentioned the cytokine storm at the beginning of this post, so I’ll try to comprehend it. A clue to the meaning comes in this mid-March article on the Lancet website. In an early sentence it mentions ‘cytokine storm syndrome’, and in the following sentence refers to the treatment of ‘hyperinflammation’. It seems the two terms are interchangeable. Another term, in the very next sentence, is ‘a fulminant and fatal hypercytokinaemia’….

Jacinta: Sounds like they’re just showing off.

Canto: Please don’t say that about our frontline covidtroops. Okay, a better site for understanding cytokines and their storms is this from New Scientist. As we’ve guessed, it’s an over-reaction of the immune system, sometimes fatal. Cytokines are small proteins, produced throughout the body, which trigger inflammation as an immune response. Sometimes the intensity of the cytokine response results in hyperinflammation. So you might say the cytokine storm is the cause and hyperinflammation the effect.

Jacinta: So this raises questions. For example, why do some have what seems an over-production of these cytokines and others don’t, in response to SARS-CoV-2 in particular? And what do these cytokines actually do to cause inflammation?

Canto: You’re asking me? Well, it’s conjectured that younger people don’t have the developed immune system that produces all these cytokines, and that’s why you don’t see symptoms. But that raises the question – do others have over-developed immune systems, but maybe only for this particular virus? Is there a general goldilocks level?

Jacinta: And is there a way of distinguishing between those who succumb to the hyperinflammation, which in turn can cause acute respiratory distress syndrome (ARDS), and those who succumb to the virus itself? Or is it always the immune response that does people in?

Canto: I don’t think so. If the immune response doesn’t work at all, I suspect the virus will spread like a cancer to the rest of the body?

Jacinta: That can’t be right. That’d mean those kids who don’t suffer the cytokine storm, or any immune reaction, would remain infected until it spread through their bodies and they dropped dead. That definitely isn’t happening.

Canto: No, you’re right – they’re developing antibodies, presumably, (and that’s a whole other story), without going through much in the way of suffering. In fact, children’s apparent immunity to the virus is something of a mystery that demands further research. If everyone could develop that kind of immunity…

Jacinta: So many questions we can’t answer. I mean, not just the myriad questions we, as dilettantes and autodidacts, can’t answer, but the fewer but many questions epidemiologists, virologists and ICU workers can’t answer. But I propose that we continue to try and educate ourselves and explore, in our feeble but earnest way. I propose that we dedicate this blog, for the foreseeable, to exploring terms and conditions, so to speak, and treatments, such as ‘cytokine’, ‘ACE-2’, ‘hypoxia’ and ‘quercetin’ and how they relate to or are affected by the Covid-19 infection. Like putting pieces together in a jigsaw puzzle, sort of. It might help us being overwhelmed by the whole picture.

Canto: Okay, let’s try it.


Coronavirus pandemic update 52, Medcram youtube video

Written by stewart henderson

April 29, 2020 at 11:55 am

Covid 19: How the SARS-CoV-2 virion does its thing

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filched from The Economist, a US website

Canto: We’ve been lapping up the excellent Medcram series of videos on the pandemic, and we’re now at episode 32 I think, from March 6, and a week’s a long time in Covid-19-world.

Jacinta: Yes and back then the largest number of confirmed cases outside of China was in South Korea, and that, I now understand, was largely because of the massive testing they’d engaged in – so elsewhere the infection was being under-reported, or barely known about.

Canto: And today, April 23, South Korea has dropped down to 27th on the list of reported cases. Interesting to note that by March 6 South Korea had tested some 140,000 people, almost 100 times more than the USA had done. As we know, the CDC had stuffed up by producing a flawed testing kit, which resulted in crucial delays.

Jacinta: And weren’t the South Korean tests more effective? They used a different type of test didn’t they?

Canto: According to a Bloomberg article referred to in the video, South Korea’s tests had a 95% sensitivity rate, much higher than those of the USA at the time. But neither the article nor the video went into detail about the type of test.

Jacinta: So I think the standard type of test used is called PCR, or RT-PCR, which means reverse transcriptase polymerase chain reaction, but I don’t really know what that means or how the tests work.

Canto: We’ll look at how the tests work later. Let’s use this video 32 to help us understand how this virus gets into a host cell and replicates.

Jacinta: Ok, so we have a cell with its nucleus, and its DNA in there, and outside the nucleus is the cell’s cytoplasm containing organelles such as ribosomes, mitochondria, lysosomes, microtubules and the like. The DNA is transcribed into single-stranded precursor messenger RNA. The RNA is then transported into the cytoplasm, where it’s modified, giving it a ‘five prime cap and a poly-A tail’. So one end has its nucleotide altered by the enzyme guanyl transferase. It has to be a guanine nucleotide connected to the mRNA with a particular triphosphate linkage. The poly-A tail is a string of adenine bases. These modifications form what’s called post-transcriptional RNA processing. Then the ribosome, about which we’ve learned so much from Venki Ramakrishnan, reads the mRNA from the five-prime end to the three-prime end. That’s in the ‘positive’ direction. It reads the nucleotides three at a time and comes up with a code (here it gets a bit vague), so that when three particular nucleotides line up, ‘a specific amino acid has to be placed on there’. And transfer RNA is involved here. So a by-product of this process is a protein (consisting of amino acids), made by the ribosome. That’s translation, not so clearly explained. Anyway, proteins are the central building blocks of our bodies, without which not.

Canto: Okay, sufficient unto the day. And remember, this transcription/translation process is known as ‘the central dogma of molecular biology’, in case you’re tested. Now we’ll turn to the virion. So the cell membrane that the virus needs to penetrate is a lipid bilayer. That bilayer is hydrophilic on the outside (that’s facing out from the cell and into the cell) and lipophilic on the inside. The coronovirus has the same lipid bilayer, with embedded proteins, notably the s-proteins or spike proteins which we know are used to attach to host cells. There are other structural proteins such as m-proteins (membrane proteins) and e-proteins (envelope proteins). Inside is the large RNA genome, protected by n-proteins (nucleocapsid proteins). Presumably there are other proteins too. Now, note that this is one virion, which is the built structure housing the virus (what enables it to survive for however long outside of a host), but also including the virus itself, which is essentially the genome. For the virus to replicate and spread, all those structural proteins have to be reproduced too.

Jacinta: The s-protein just happens to fit, like a key in a lock, a receptor protein in the human host cell membrane called the ACE-2 receptor. These ACE-2 receptors, full name angiotensin-converting enzymes, are found in our lungs, and elsewhere, such as the heart, the kidneys and the intestines. Once this connection is made, the viral RNA is released into the cytosol. And as it happens, this viral RNA also has a 5 prime cap and a poly-A tail just like the host’s mRNA. It isn’t clear from the video whether this is because it gets modified within the cytoplasm or it’s already ‘primed’ so to speak. Anyway, the cell’s ribosomes start to act on this rogue RNA as it would on its own mRNA. Meanwhile the structural proteins from the viral membrane are incorporated into the host membrane, possibly earmarking it for destruction.

Canto: The ribosome makes a protein from the viral RNA, called RNA-dependent RNA polymerase (RdRP), or an RNA replicase. The protein somehow makes another complementary strand of RNA, running in the opposite direction, from which the ribosome makes more protein, which makes more RNA and so forth. This RNA also codes for the structural proteins of the virion (because the RdRP somehow forms shorter strands of RNA, called sub-genomic RNAs, specific to the making of those proteins by the hijacked ribosomes), so enabling the spread of the virus.

Jacinta: The key, the video tells me, is in the name polymerase. That’s an enzyme that puts nucleotides together in long chains. Also, many ribosomes – there are thousands in our cells – are connected to the cell membrane and can help create new virions that can leave the cell in much the opposite way they entered, being packaged and then budded off. Through this hijacking process, one virion can come in, and any number of them can go out, and generally from the lung region. They’re naturally attacked by the immune system causing inflammation, possibly pneumonia and respiratory failure.

Canto: Yes and thanks to Dr Roger Seheult for all this, we hope we’re not misreading his work. He goes on to talk about the possibility of inhibiting this nasty polymerase, RdRP. We might talk about this, or not, in the next post.


Coronavirus update 32, with Dr Seheult – series of videos

The gene machine, by Venki Ramakrishnan

Written by stewart henderson

April 25, 2020 at 2:04 pm