Virus 1 Astra Zenica vaccine 0

It’s already happened. A mutated pandemic virus has rendered a vaccine useless. This is serious — the game of cat and mouse with the mutating pandemic virus (otherwise known as natural selection) has begun. You can read all about it here

https://www.sciencemag.org/news/2021/02/south-africa-suspends-use-astrazenecas-covid-19-vaccine-after-it-fails-clearly-stop?utm_source=Nature+Briefing&utm_campaign=6ada806177-briefing-dy-20210208&utm_medium=email&utm_term=0_c9dfd39373-6ada806177-46043190

For a leisurely stroll through the background needed to understand the Science and Nature articles I’m going to essentially republish (and refurbish) a very recent  post — trying to make things as accessible as possible. 

The human species as a culture medium for the pandemic virus

Creationists or not, we are all about to get an unwanted lesson in natural selection and evolution, courtesy of the current pandemic virus (SARS-CoV-2).  This is going to be a long post, which will contain an incredible case of meningitis, thoughts on selfish genes in viruses, evolution, natural selection and why we’re in for a very, very long haul with the pandemic virus.

As you probably know, mutant pandemic viruses (all different) have emerged (in England, South Africa, Brazil).  Even worse they appear to be more infectious, and some are more resistant to our vaccines (all of which were made before they appeared).  

Here is lesson #1 in natural selection.  Viruses have no brains, they barely have a genome.  The human genome contains 3 billion positions, the pandemic virus 30,000.  So we have 100,000 times more information in our genome than the virus does. 100,000 is about the number of inches in a mile and half.  

So how is the virus outsmarting us?  Simply by reproducing like mad.  The molecular machines that copy our genome are very accurate, making about 1 mistake per 100,000,000 positions copied — that’s still enough for the average newborn to have 30 new mutations (more if the parents are older).  The viral machine is much less accurate.  So lots of genome mutations are made (meaning that the viral proteins made from the genome change slightly).  Those that elude the vaccines and antibodies we’re throwing at them survive and reproduce, most don’t.  This is natural selection in action. Survival of the fittest.  Darwin wasn’t kidding.

What is so remarkable about the British and the South African variants, is that they contain multiple mutations (23 in the British variant, at least 3 in the South African variant).  Usually its just one or two.

 You’ve probably heard about the mutation changing just one of the 147 amino acids  in hemoglobin to cause sickle cell anemia. Here’s another.  APOE is a 299 amino acid protein.  It comes in 3 variants  — due to changes at 2 positions.  One variant greatly increases the risk of Alzheimer’s disease, another decreases it.  So even single mutations can be quite powerful. 

So how did these multiple mutations come about?  We likely now have an answer due to one very well studied case [ Cell vol. 183 pp. 1901 – 1912 ’20 ] in an immunocompromised patient with chronic lymphatic leukemia (CLL). She shed the virus for 70 days.  Even so, she wasn’t symptomatic, but because the patient had enough immune system to fight the virus to a draw, it persisted, and so its genome was always changing.  The authors were smart enough to continually sequence the viral genome throughout the clinical course and watch it change.  So that’s very likely how the virus accumulates mutations, it lived for a long time in a patient who lived a long time with a weakened immune system allowing the virus to merrily mutate without being killed and allowing the weakened immune system to effectively select viruses it can’t kill. 

Could this happen again? Of course.   There are some 60,000 new cases of CLL each year in the USA.  Many of them have abnormal immune systems even before chemotherapy begins.

Here is an example from my own practice. The patient was a 40 year old high school teacher who presented with severe headache, stiff neck and drowsiness.  I did a spinal tap to get cerebrospinal fluid (CSF) for culture so we could find the best possible antibiotic to treat the organism.  This was 30+ years ago, and we had no DNA testing to tell us immediately what to do.  We had to wait 24 hours  while the bugs grew in culture to form enough that we could identify the species and determine  the antibiotics it was sensitive to. . 

As the fluid came out, I had a sinking feeling; as it was cloudy, implying lots of white cells fighting the infection. Enough white cells to make CSF cloudy (it normally looks like water) is a very bad sign. So after starting the standard antibiotic to be used in the first 24 hours before the cultures came back, I called the lab for the cell count.  They said there weren’t any.  I thought they’d seriously screwed up maybe losing what I’d sent or mislabeling it and looking at the wrong sample, and I unpleasantly stormed down to the lab (as only an angry physician can do) to see the spinal fluid.  They were right.  The cloudiness of the CSF was produced by hordes of bacteria not white cells.  This was even worse as clearly the bacteria were winning and the patient’s immune system was losing, and I never expected the patient to survive.  But survive he did and even left the hospital.  

Unfortunately, the meningitis turned out to be  the first symptom of an abnormal immune system due to a blood malignancy — multiple myeloma. 

****

Addendum 2 February — I sent this post to an old friend and college classmate who is now a hematology professor at a major med school.  He saw a similar case —

“When I was a medical student I saw a pediatric sickle anemia patient (asplenic) with fever and obtundation. When I looked at the methylene-blue stained CSF, I thought that stain had precipitated. So I obtained a fresh bottle of stain and it looked the same. Only this time, I looked more closely and what I thought was precipitated stain were TNTC pneumococci.

I urge all my immunosuppressed patient to get vaccinated for covid-19. I worry that if many people don’t get vaccinated,  those who do will not be that better off.”

Addendum 3 February– I asked him if his patient had survived like mine —

answer 

“Unfortunately, no. With the pneumococcus, If antibiotics are not started within 4 hours after recognition, the train has left the station.”

 

****

So there are millions of active cases of the pandemic, and tons of people with medical conditions (leukemia, multiple myeloma, chemotherapy for other cancer) with abnormal immune systems, just waiting for the pandemic virus to find a home and proliferate for days to weeks.  Literally these people are culture media for the virus. Not all of them have been identified, so don’t try to prevent this by withholding vaccination from the immunocompromised — they’re the ones who need it the most. 

I think we’re in for a very long haul with the pandemic.  We’re just gearing up to stay on top of the viral sequence du jour.   Genome sequencing is not routine (it should be).  The South African and British mutations were picked up because a spike in cases led people to sequence the virus from these patients.  Viral genome sequencing and surveillance should be routine in most countries and should not wait for an infection spike to occur. 

You may come across the terms B.1.351 and  507Y.V2 — they are different names for the South African virus which beat Astra Zenica.  The British variant is also called B.1.1.7

The human species as a culture medium for the pandemic virus

Creationists or not, we are all about to get an unwanted lesson in natural selection and evolution, courtesy of the current pandemic virus (SARS-CoV-2).  This is going to be a long post, which will contain an incredible case of meningitis, thoughts on selfish genes in viruses, evolution, natural selection and why we’re in for a very, very long haul with the pandemic virus.

As you probably know, mutant pandemic viruses (all different) have emerged (in England, South Africa, Brazil).  Even worse they appear to be more infectious, and some are more resistant to our vaccines (all of which were made before they appeared).  

Here is lesson #1 in natural selection.  Viruses have no brains, they barely have a genome.  The human genome contains 3 billion positions, the pandemic virus 30,000.  So we have 100,000 times more information in our genome than the virus does. 100,000 is about the number of inches in a mile and half.  

So how is the virus outsmarting us?  Simply by reproducing like mad.  The molecular machines that copy our genome are very accurate, making about 1 mistake per 100,000,000 positions copied — that’s still enough for the average newborn to have 30 new mutations (more if the parents are older).  The viral machine is much less accurate.  So lots of genome mutations are made (meaning that the viral proteins made from the genome change slightly).  Those that elude the vaccines and antibodies we’re throwing at them survive and reproduce, most don’t.  This is natural selection in action. Survival of the fittest.  Darwin wasn’t kidding.

What is so remarkable about the British and the South African variants, is that they contain multiple mutations (23 in the British variant).  Usually its just one or two.

 You’ve probably heard about the mutation changing just one of the 147 amino acids  in hemoglobin to cause sickle cell anemia. Here’s another.  APOE is a 299 amino acid protein.  It comes in 3 variants  — due to changes at 2 positions.  One variant greatly increases the risk of Alzheimer’s disease, another decreases it.  So even single mutations can be quite powerful. 

So how did these multiple mutations come about?  We likely now have an answer due to one very well studied case [ Cell vol. 183 pp. 1901 – 1912 ’20 ] in an immunocompromised patient with chronic lymphatic leukemia (CLL). She shed the virus for 70 days.  Even so, she wasn’t symptomatic, but because the patient had enough immune system to fight the virus to a draw, it persisted, and so its genome was always changing.  The authors were smart enough to continually sequence the viral genome throughout the clinical course and watch it change. 

Could this happen again.  Of course?   There are some 60,000 new cases of CLL each year in the USA.  Many of them have abnormal immune systems even before chemotherapy begins.

Here is an example from my own practice. The patient was a 40 year old high school teacher who presented with severe headache, stiff neck and drowsiness.  I did a spinal tap to get cerebrospinal fluid (CSF) for culture so we could find the best possible antibiotic to treat the organism.  This was 30+ years ago, and we had no DNA testing to tell us immediately what to do.  We had to wait 24 hours  while the bugs grew in culture to form enough that we could identify the species and determine  the antibiotics it was sensitive to. . 

As the fluid came out, I had a sinking feeling; as it was cloudy, implying lots of white cells fighting the infection. Enough white cells to make CSF cloudy (it normally looks like water) is a very bad sign. So after starting the standard antibiotic to be used in the first 24 hours before the cultures came back, I called the lab for the cell count.  They said there weren’t any.  I thought they’d seriously screwed up maybe losing what I’d sent or mislabeling it and looking at the wrong sample, and I unpleasantly stormed down to the lab (as only an angry physician can do) to see the spinal fluid.  They were right.  The cloudiness of the CSF was produced by hordes of bacteria not white cells.  This was even worse as clearly the bacteria were winning and the patient’s immune system was losing, and I never expected the patient to survive.  But survive he did and even left the hospital.  

Unfortunately, the meningitis turned out to be  the first symptom of an abnormal immune system due to a blood malignancy — multiple myeloma. 

****

Addendum 2 February — I sent this post to an old friend and college classmate who is now a hematology professor at a major med school.  He saw a similar case —

“When I was a medical student I saw a pediatric sickle anemia patient (asplenic) with fever and obtundation. When I looked at the methylene-blue stained CSF, I thought that stain had precipitated. So I obtained a fresh bottle of stain and it looked the same. Only this time, I looked more closely and what I thought was precipitated stain were TNTC pneumococci.

I urge all my immunosuppressed patient to get vaccinated for covid-19. I worry that if many people don’t get vaccinated,  those who do will not be that better off.”

Addendum 3 February– I asked him if his patient had survived like mine —

answer 

“Unfortunately, no. With the pneumococcus, If antibiotics are not started within 4 hours after recognition, the train has left the station.”

 

****

So there are millions of active cases of the pandemic, and tons of people with medical conditions (leukemia, multiple myeloma, chemotherapy for other cancer) with abnormal immune systems, just waiting for the pandemic virus to find a home and proliferate for days to weeks.  Literally these people are culture media for the virus. Not all of them have been identified, so don’t try to prevent this by withholding vaccination from the immunocompromised — they’re the ones who need it the most. 

I think we’re in for a very long haul with the pandemic.  We’re just gearing up to stay on top of the viral sequence du jour.   Genome sequencing is not routine (it should be).  The South African and British mutations were picked up because a spike in cases led people to sequence the virus from these patients.  Viral genome sequencing and surveillance should be routine in most countries  — not waiting on an infection spike. 

 

 

Frameshifting

hed oga tet hec atw hoa tet her atw hob ith erp aw

Say what?  It’s a simple sentence made of 3 letter words frameshifted by one

he dog ate the cat who ate the rat who bit her paw

Codons are read as groups of three nucleotides, and frameshifting has always been thought to totally destroy the meaning of a protein, as an entirely different protein is made.

Not so says PNAS vol. 117 pp. 5907 – 5912 ’20. Normally a frameshifted protein has only 7% sequence identity with the original.  This is about what one would expect given that there are 20 amino acids, and chance coincidence would argue for 5%.  But there are more ways for proteins to be similar rather than identical.  One can classify our amino acids in several ways, charged vs. uncharged, aromatic vs. nonaromatic, hydrophilic vs. hydrophobic etc. etc.

The authors looked at 2,900 human proteins, then they frameshifted the original by +1 and compared the hydrophobicity profiles of the two.  Amazingly there was a correlation of .7 between the two, despite sequence identity of 7%.  Similarly frameshifting didn’t disturb the chance of intrinsic disorder.  So frameshifting is embedded in the structure of the universal genetic code, and may have actually contributed to its shaping.  Frameshifting could be an evolutionary mechanism of generating proteins with similar attributes (hydrophobicity, intrinsic order vs. disorder, etc.) but with vastly different sequences.  The evolution, aka natural selection aka deus ex machine aka God could muck about the ready made protein and find something new for it to do.   A remarkable concept.

The gag-pol precursor p180 of the AIDS virus is derived from the gag-pol mRNA by translation involving ribosomal frameshifting within the gag-pol overlap region.  The overlap is 241 nucleotides with pol in the -1 phase with respect to gag (that’s an amazing 80 amino acids).  I was amazed at the efficiency of coding of two different proteins (one and enzyme and one structural), but perhaps they aren’t that different in terms of hydrophobicity (or something else).

I’d love to see the hydropathy profile of the overlap of the two proteins, but I don’t know how to get it.

A probably original (and probably wrong) idea

This post is not for the pharmacologically or chemically faint of heart.  Drug chemists should have no problem with it. You’ll need to bring your own background to the party, older posts on this blog don’t provide it.

It involves a particularly well studied G protein coupled receptor (GPCR), the beta2 adrenergic receptor.  Our genome codes for over 800 GPCRs, and at least 30% of all the drugs we currently use bind to them.

So here are my notes on  the paper that set me to thinking.  The idea follows the **** at the end.

       [ Science vol. 335 pp. 1055 – 1056, 1106 – 1110 ’12 ]  Conformation changes on ligand binding follow a common theme in the 3 activated GPCRs (including the beta2 adrenergic receptor) that have so far been crystallized.  Agonist binding results in an outward displacement of transmembrane segments 5 and 6 (TM5 and TM6) which opens a pocket on the intracellular surface of the receptor accepting the G protein.  Binding of beta-arrestin to GPCRs requires phosphorylation of sites on the cytoplasmic surface on TM7 toward the carboxy terminus of the GPCRs.

        This work attached 19F probes to cysteines at the intracellular ends of TM6 and TM7 of the beta2 adrenergic receptor for NMR spectroscopy.  They used 2,2,2 trifluoroethanethol to label 3 native cysteine residues (#265, #327, #341).  With no bound ligand two conformations in the ligand free state are in equilibrium with each other.  Then different ligands were added.  Carvedilol induced a shift to the TM7 active state, but had little effect on the conformational equilibrium at TM6.  Carvedilol is an antagonist which blocks G protein signaling and induces receptor desensitization and internalization.  

      Older work shows that the weakest agonists loosen interactions (the ionic lock and toggle), that juxtaposeTM3 and TM6 in the inactive state.  More potent agonists perturb the Asn Pro X X Y sequence of TM7 which permits phosphorylation and beta-arrestin binding.  Substituents on the hydroxylamine tail of the ligand are important — large nonpolar groups are particularly effective.  

       Agonist induced receptor bias for G protein vs. beta-arrestin signaling is one of many instances of the plastic and multistate behavior characteristic of GPCRs. 

*****

So what’s the idea?  Drug chemists spend a lot of their time designing and making slightly different GPCR ligands to have slightly different effects.  On p. 1109 of the paper, the structures of 8 are given.  Probably hundreds exist.  The work here describes two different conformations of the beta2 GPCR, each of which triggers a different cellular response,  because each conformation binds a different set of proteins.  The drugs (particularly carvedilol which is in clinical use) cause the GPCR to favor one conformation over another.

Based on what we’ve been taught about neurotransmitters and neurotransmission, this makes no evolutionary sense.  The ‘natureal’ ligand for beta2 adrenergic GPCR is norepinephrine.  What selective advantage can there be to having the GPCR flopping between 2 (or more) conformations?  Well there might be if other neurotransmitters bound to it producing different conformations.

Back in the day there was a lot of talk about false neurotransmitters.  These were small molecules which somehow got into the synaptic vesicle and were released into the synaptic cleft when the vesicle was exocytosed, but which didn’t bind to the receptor.  One such false neurotransmitter was octopamine (norepinephrine without the meta-hydroxyl group).  It was thought to be formed in excess in liver failure, enter into synaptic vesicles and do nothing useful when released, causing hepatic encephalopathy.

A less fanciful example is available [ Neuron vol. 46 pp. 1 – 2, 65 – 74 ’05 ] Serotonin, a true neurotransmitter we all know and love, can enter dopamine neurons, when reuptake is blocked (by a tricyclic antidepressant, or by a SSRI), where it accumulates in synaptic vesicles.

Back in the day when I was in medical school, there was something called the Dale Feldberg law, which said that an identical chemical transmitter is liberated at all terminals of a single neuron.  We now know that this is wrong — neurons release two classes of chemical transmitters (1)  biogenic amines such as norepinephrine, dopamine and serotonin and (2) neuropeptides, and many release one from each class.  Whether or not a single neuron releases more than one biogenic amine isn’t known (despite the example above).

So perhaps the body is a better drug chemist than we think, and the same GPCR can bind different neurotransmitters with different effects, explaining the multiple conformations they adopt.  If true, this means that there are probably other transmitters out there that we don’t know about.  In the case of the beta2 adrenergic receptor, they are probably small molecules, as the binding site is deep within the transmembrane region of the GPCR.

So is this sort of thing why GPCRs have multiple conformations?