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The Assembly Pathway of an Icosahedral Single-Stranded RNA Virus Depends on the Strength of Inter-Subunit Attractions

The Assembly Pathway of an Icosahedral Single-Stranded RNA Virus Depends on the Strength of Inter-Subunit Attractions | Virology News | Scoop.it

The strength of attraction between capsid proteins (CPs) of cowpea chlorotic mottle virus (CCMV) is controlled by the solution pH. Additionally, the strength of attraction between CP and the single-stranded RNA viral genome is controlled by ionic strength. By exploiting these properties, we are able to control and monitor the in vitro co-assembly of CCMV CP and single-stranded RNA as a function of the strength of CP–CP and CP–RNA attractions. Using the techniques of velocity sedimentation and electron microscopy, we find that the successful assembly of nuclease-resistant virus-like particles (VLPs) depends delicately on the strength of CP–CP attraction relative to CP–RNA attraction. If the attractions are too weak, the capsid cannot form; if they are too strong, the assembly suffers from kinetic traps. Separating the process into two steps—by first turning on CP–RNA attraction and then turning on CP–CP attraction—allows for the assembly of well-formed VLPs under a wide range of attraction strengths. These observations establish a protocol for the efficient in vitro assembly of CCMV VLPs and suggest potential strategies that the virus may employ in vivo.

 
Ed Rybicki's insight:

I do love it when a paper is published that could have been done pretty much any time in the last 40 years - and with one of my favourite viruses, that I played with a LOT back there before 1980.

Ultracentrifugation, pH meters, ionic strength determinations, EM...all tried and true, and used 40+ years ago. OK, they also used cloned BMV RNA 1 cDNA, and did 3-D image reconstruction from EMs, but hey, they needn't have done that!  Nice, straightforward physicochemical studies, on a well-characterised virus, with good, simple conclusions. 

Namely, that assembly of the virus is NOT just a simple mix-CP-and-RNA-and-it-will-happen, but that it depends upon both pH, for modulating ionic interactions,and ionic strength for modulating ionic interactions AND the "hydrophobic effect", as we used to know it.

While their conclusions are relevant for assembly of heat- and nuclease-resistant nano particles in vitro, I wonder if they are physiologically relevant: if "correct" assembly depends upon first, turning on CP-RNA attraction (ionic strength shift), and second, turning on CP-CP attraction (pH shift) - where in the cell does that happen?

In their own words, "It is generally accepted that the cytoplasm of plant cells is maintained near neutral pH with ionic strength of approximately 0.1 M. Our in vitro results show that these conditions are insufficient for nucleocapsid formation in the absence of cellular host factors."

Yeeee-ee-eesssss...precisely. What happens in the cell? The answer could lie in the one thing they don't report, but that some of the heroes of my distant youth - people like JB Bancroft and Thom Hohn, both quoted (from 1970 and 1969 respectively) in this paper, DID do. Namely, investigate what happens at different CP and RNA concentrations, at constant pH and ionic strength.

You see, it was shown 30+ years ago - and I have been lecturing on it since then - that CP and RNA for viruses like BMV / CCMV and MS2 form different complexes with their cognate partners at different molecular ratios. That is, at low CP:RNA ratios, a high-affinity complex is formed, which is basically a ribonucleoprotein complex without structure. Increasing the CP:RNA ratio for both MS2 and CCMV, as I recall (maybe Dick Verduin was involved with CCMV), results in further lower-affinity association of CP with both RNA and already-bound CP - which acts as a nucleation complex - to result in full capsid assembly.

I note that the process in both cases was shown to be specific, for low CP:RNA ratios: that is, it was cognate CP and RNA doing the high affinity nucleation complex formation.

And these guys deliberately used a heterologous RNA...albeit one from a related virus, but still: what would have happened if they'd used CCMV RNA?

Still - great paper, taking me back to when I wrote an essay on "Assembly of Spherical Plant Viruses" in my Honours year in 1977, quoting quite a few of the same references these folk did. Ah, simpler times...B-)

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Novavax begins early-stage trial for combined influenza/COVID-19 vaccine

Novavax begins early-stage trial for combined influenza/COVID-19 vaccine | Virology News | Scoop.it
Vaccine developer Novavax Inc said on Wednesday it has initiated an early-stage study to test its combined flu and COVID-19 vaccine.
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Cosmic 'airburst' leveled a biblical city in the Jordan Valley

Cosmic 'airburst' leveled a biblical city in the Jordan Valley | Virology News | Scoop.it
"There's evidence of a large cosmic airburst, close to this city called Tall el-Hammam." The shock of the explosion over the city was enough to level it.
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God has nukes??
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500-million-year-old fossil fills in 'Cambrian explosion' puzzle

500-million-year-old fossil fills in 'Cambrian explosion' puzzle | Virology News | Scoop.it
A rare fossil discovery of an ancient worm-like creature sheds light on a period of time when many of the world's animal groups were first appearing.
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U.S. COVID death toll surpasses 1918 flu fatalities

U.S. COVID death toll surpasses 1918 flu fatalities | Virology News | Scoop.it
The recorded number COVID-19 deaths in the U.S. has now surpassed the known number of fatalities from the 1918 flu pandemic.
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Covid booster vaccine rollout to begin across UK next week. While Africa is still way undervaccinated. B-(

Covid booster vaccine rollout to begin across UK next week. While Africa is still way undervaccinated. B-( | Virology News | Scoop.it
Experts say a single dose of Pfizer should be offered at least six months after a second dose.
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Early Moderna vaccine recipients twice as likely to contract Covid

Early Moderna vaccine recipients twice as likely to contract Covid | Virology News | Scoop.it
Moderna Inc says people who received its COVID-19 vaccine last year are nearly twice as likely to get a breakthrough infection compared to those recently vaccinated.
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COVID-19 will soon surpass the Spanish flu as America’s deadliest pandemic 

COVID-19 will soon surpass the Spanish flu as America’s deadliest pandemic  | Virology News | Scoop.it
At its current pace, COVID-19 would surpass the 675,000 estimated U.S. deaths caused by the 1918 Spanish Flu pandemic—the deadliest pandemic in U.S. history—before the end of September.
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All 3 Major Vaccine Companies Suddenly Have Name Changes for Their Covid Shots — And People are Already Confused

All 3 Major Vaccine Companies Suddenly Have Name Changes for Their Covid Shots — And People are Already Confused | Virology News | Scoop.it
"All three major Covid-19 'vaccine' manufacturers have unveiled new names for their 'fully authorized' jabs, even as two pharmaceutical companies await FDA approval"...
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COVID patients face risk for self-attacking antibodies

COVID patients face risk for self-attacking antibodies | Virology News | Scoop.it
At least 1 in 5 hospitalized COVID-19 patients develops autoantibodies, antibodies that attack their own tissue within a week of admission, research finds.
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Hong Kong closely monitors human case of avian influenza A(H5N6) in Mainland 

Hong Kong closely monitors human case of avian influenza A(H5N6) in Mainland READING TIME 2 MIN     CHRISTIAN FERNSBY ▼ | September 19, 2021 The Centre for Health Protection (CHP) of the Department of Health is closely monitoring a human case of avian influenza A(H5N6) in the Mainland. ASIA   Centre for Health Protection The case involves a 40 year old woman living in Yongzhou in Hunan Province, who had prior exposure to a live poultry market before the onset of symptoms. She developed symptoms on September 8 and was admitted for treatment on the following day. The patient is in serious condition. From 2014 to date, 43 human cases of avian influenza A(H5N6) have been reported by Mainland health authorities. "All novel influenza A infections, including H5N6, are notifiable infectious diseases in Hong Kong," a spokesman for the CHP said. Travellers to the Mainland or other affected areas must avoid visiting wet markets, live poultry markets or farms. They should be alert to the presence of backyard poultry when visiting relatives and friends. They should also avoid purchasing live or freshly slaughtered poultry, and avoid touching poultry/birds or their droppings. They should strictly observe personal and hand hygiene when visiting any place with live poultry. Travellers returning from affected areas should consult a doctor promptly if symptoms develop, and inform the doctor of their travel history for prompt diagnosis and treatment of potential diseases. It is essential to tell the doctor if they have seen any live poultry during travel, which may imply possible exposure to contaminated environments. This will enable the doctor to assess the possibility of avian influenza and arrange necessary investigations and appropriate treatment in a timely manner. While local surveillance, prevention and control measures are in place, the CHP will remain vigilant and work closely with the World Health Organization and relevant health authorities to monitor the latest developments. The public should maintain strict personal, hand, food and environmental hygiene and take heed of the advice below when handling poultry: • Avoid touching poultry, birds, animals or their droppings; • When buying live chickens, do not touch them and their droppings. Do not blow at their bottoms. Wash eggs with detergent if soiled with faecal matter and cook and consume the eggs immediately. Always wash hands thoroughly with soap and water after handling chickens and eggs; • Eggs should be cooked well until the white and yolk become firm. Do not eat raw eggs or dip cooked food into any sauce with raw eggs. Poultry should be cooked thoroughly. If there is pinkish juice running from the cooked poultry or the middle part of its bone is still red, the poultry should be cooked again until fully done; • Wash hands frequently, especially before touching the mouth, nose or eyes, before handling food or eating, and after going to the toilet or touching public installations or equipment, such as escalator handrails, elevator control panels or door knobs, or when hands are dirtied by respiratory secretions after coughing or sneezing; and • Wear a mask if fever or respiratory symptoms develop, when going to a hospital or clinic, or while taking care of patients with fever or respiratory symptoms. ■ WHAT TO READ NEXT
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Gordon Brown calls for urgent action to avert ‘Covid vaccine waste disaster’ 

Gordon Brown calls for urgent action to avert ‘Covid vaccine waste disaster’  | Virology News | Scoop.it
More than 100m doses could be discarded by December if global leaders do not share jabs with poorest countries, warns former PM...
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Helium rain probably falls inside Jupiter and Saturn

Helium rain probably falls inside Jupiter and Saturn | Virology News | Scoop.it
New research validates a nearly 40-year-old prediction that helium rain is possible inside planets such as Jupiter and Saturn.
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Pakistan administers 10 millionth Covid vaccine dose

Pakistan administers 10 millionth Covid vaccine dose | Virology News | Scoop.it
Asad Umar says authorities aim to vaccinate 70m people by the end of this year.
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Mass booster vaccines unnecessary as immunity ‘lasting well’, says Oxford jab professor

Mass booster vaccines unnecessary as immunity ‘lasting well’, says Oxford jab professor | Virology News | Scoop.it
Prof Dame Sarah Gilbert urges ministers to send third doses to countries where only a small number of people have been jabbed...
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Iron Maiden's Bruce Dickinson on COVID battle: "It's not just a flu – it makes your willy shrivel"

Iron Maiden's Bruce Dickinson on COVID battle: "It's not just a flu – it makes your willy shrivel" | Virology News | Scoop.it
"I got what people are calling a breakthrough COVID infection"...
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Low oxygen is pushing fish into shallower water

Low oxygen is pushing fish into shallower water | Virology News | Scoop.it
As the ocean warms, oxygen concentrations go down. Fish are already moving into shallower waters, new research indicates.
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J&J: Real-world Data Confirms Efficacy Of Vaccine In The U.S.; Booster Shows 94% Protection

(RTTNews) - Johnson & Johnson (JNJ) said its single-shot vaccine showed strong and long-lasting protection in the real world. In a study that incl...
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xkcd: Vaccine Research

xkcd: Vaccine Research | Virology News | Scoop.it
Vaccine Research(alt-text) Honestly feel a little sheepish about the amount of time and effort I spent confirming "yes, the vaccine helps protect people from getting sick and dying" but I guess everyone needs a hobby. |< < ? > >| Archive Store What If? About
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Memory Killer T cells are primed in the Spleen during Influenza infection

Memory Killer T cells are primed in the Spleen during Influenza infection | Virology News | Scoop.it
This finding upends the long-held paradigm that priming during lung infections takes place only in the draining lymph nodes, and it will be key to developing more efficient vaccinations and therapies...
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Drought drives plant diversity more than temp

Drought drives plant diversity more than temp | Virology News | Scoop.it
The effects of drought on plant variety around the world could change our understanding of future diversity in a warming world.
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Why mRNA vaccines won't replace all others

Why mRNA vaccines won't replace all others | Virology News | Scoop.it
mRNA vaccines have proven highly effective for COVID-19. But that doesn't mean they're ready to replace all others, experts explain.
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...like I keep telling anyone who'll listen...B-)
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COVID vaccine immunity is waning — how much does that matter?

COVID vaccine immunity is waning — how much does that matter? | Virology News | Scoop.it
As debates about booster shots heat up, what’s known about the duration of vaccine-based immunity is still evolving.
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Scottish Covid vaccine trialists ‘treated like second-class citizens’ 

Scottish Covid vaccine trialists ‘treated like second-class citizens’  | Virology News | Scoop.it
Novavax volunteers fear start of vaccine passports next month could put them at further disadvantage...
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Now this would be SERIOUSLY fucking stupid!!
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Nursing homes are ground zero for COVID reinfections

Nursing homes are ground zero for COVID reinfections | Virology News | Scoop.it
New research sheds light on why COVID-19 hit nursing homes so hard: People in long-term care facilities had more reinfections than the general population.
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Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine | NEJM

Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine | NEJM | Virology News | Scoop.it
To the Editor: Polack et al. (Dec. 31)1 report a vaccine efficacy of 94.8% against Covid-19 after two doses of the messenger RNA (mRNA) vaccine BNT162b2 (Pfizer–BioNTech). The authors also report a...
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