Vipin M. Vashishtha Profile picture
Apr 8, 2023 16 tweets 8 min read Read on X
The indian saga of XBB.1.16 #Arcturus

It has been a month when @siamosolocani 1st flagged this variant. Later, I started tracking it. We are still amid an ongoing surge, it’s time to take a stock of the situation: what we do know, what we don’t 1/

What do we know for sure!

1-XBB.1.16 has succeeded in creating a new, significant surge in India after a gap of >6 months. A feat that even BA.5, BQ.1 & XBB.1.5 failed to achieve!
2/ ImageImage
2-XBB.1.16 definitely has got a growth advantage & more fitter than other circulating XBBs & has even replaced some other similar sublineages like XBB.1.5 & XBB.1.9 3/
@vinodscaria Image
3-XBB.1.16 is definitely not a more pathogenic variant than other Omicron’s progenies

4-This variant is still evolving, adding few more mutations. But not all new mutations are beneficial to the virus (i.e. E180V). 4/ Image
5-The chances of XBB.1.16 leading a new, significant wave (i.e. the 4th wave) akin to Jan’ 22 BA.2 wave are remote 5/
@JPWeiland Image
6-The new surge in cases is yet to peak in India. According to @JPWeiland India is more than 2 weeks from peak cases. 6/ Image
And, now let’s see what we still don’t know:
1-How big this new surge would be?
2-What are the key factors responsible for making XBB.1.16 a more fitter variant than its contemporaries? Higher immune evasion?
Higher infectiousness, i.e. higher ACE2 binding? 7/
A new study by @SystemsVirology suggests:

-a higher infectiousness (~1.2-fold greater than that of XBB.1.5) 8/

Image
However, XBB.1.16 doesn’t have significantly greater immune evasion than XBB.1.5. 9/

@SystemsVirology Image
We know XBB.1.5 & XBB.1.16 have almost similar Spike barring a few Spike mutations. However, above study suggests that mutations in the non-Spike region may be responsible for increased viral growth of XBB.1.16 10/ Image
The above mentioned study & some early work done by @StuartTruvile in NSW, Australia points that XBB.1.16 is not more immune evasive than XBB.1.5. @StuartTurville calls it “super similar to XBB.1.5 in neut evasion”. 11/ Image
Now, If it's not immune evasion, is the growth advantage is because of stronger ACE2 binding then?

No, in fact, the entry into cells is similar as with Omicrons including XBB.1.5. @StuartTurville has shown this 👇 12/ Image
Most evolutionary biologists now agree to believe that the increased fitness is mainly due to changes at non-Spike region of this variant.
Acc to @LongDesertTrain ORF1a:L3829F is probably the key mute responsible for its advantage over XBB.1.9 13/ Image
As per @SolidEvidence mutation in NSP6 of ORF1ab may be behind this higher fitness 14/ Image
Now, most experts believe the extra mutations at ORF9b & ORF1a are responsible to give “teeth” to this variant.
ORF9b is thought to be involved with suppressing interferon response, so they might make the virus slightly fitter by counteracting the innate immune system. 15/ Image
We still don’t know whether XBB.1.16 will become a global thing replacing the existing dominant variant XBB.1.5. However, all the indications point it will. This is the current projection by @JPWeiland for the US (an update on the CDC graph) 16/ Image

• • •

Missing some Tweet in this thread? You can try to force a refresh
 

Keep Current with Vipin M. Vashishtha

Vipin M. Vashishtha Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @vipintukur

Jul 4
A NEW study finds that anti-SARS-CoV-2 antibodies play a protective role against vital organ-related #LongCovid (LC) symptoms, especially cardiovascular symptoms, but are insufficient in preventing or limiting other highly prevalent LC symptoms, such as neurological, psychiatric and pulmonary. 1/Image
These data underscore the complexity of the potential involvement of anti-SARS-CoV-2 immune responses in either protecting against or contributing to the development of different #LongCovid phenotypes. 2/ Image
The disturbed immunological profile supports the idea of some sort of silent longCOVID, that may eventually manifest as critical clinical events, such as acute myocardial infarction or cerebral vascular accidents. 3/ Image
Read 5 tweets
Jun 26
A meta-analysis from Egypt of 125 studies involving over 4 million COVID survivors shows that months to years after infection, fatigue was the most common symptom at 43%. Around 27% of people experience cognitive impairment after COVID infection. 1/ Image
Further, 28% experienced memory issues, 24% sleep disorders, 20% headaches, 16% dizziness, 14% depression, and 13% anxiety, with significant variability depending on follow‑up time, disease severity, sex, and BMI. 2/ Image
Neurological symptoms are common & persistent in COVID survivors. This study highlights significant burden these symptoms place on individuals, emphasizing the need for well-resourced multidisciplinary healthcare services to support post-COVID recovery. 3/3
Read 4 tweets
Jun 24
A new review on neuroimmune pathophysiology of #LongCOVID explores how SARS-CoV-2 can cause lasting neurological symptoms through a combination of direct infection, immune dysregulation, and persistent inflammation. 1/ Image
Key mechanisms include viral antigen persistence, autoimmunity, blood–brain barrier disruption, neurotransmitter imbalances, and glial cell dysfunction. The authors link these processes to cognitive impairment, fatigue, dysautonomia, and other Long COVID symptoms. 2/ Image
Despite the perception that COVID-19 is now a mild disease, there is overwhelming evidence indicating that SARS-CoV-2 infection is capable of producing widespread post-acute sequelae in a significant percentage of infections. 3/ Image
Read 4 tweets
Jun 19
I think, therefore I age!

As people get older, a growing population of cells starts to consume more energy — perhaps because the cells accumulate damage that leads them to rev up processes such as inflammation. 1/ Image
An emerging hypothesis suggests that the brain accommodates these energy-hogging ‘senescent cells’ by stripping resources from other biological processes, which ultimately results in outward signs of ageing, such as greying hair or a reduction in muscle mass. 2/
It’s one example of a growing understanding of how our brains control ageing and how psychological stress can accelerate the process at a molecular level. 3/ Image
Read 5 tweets
Jun 17
A NEW study found that the SARS-CoV-2 nonstructural protein 15 (nsp15) helps the virus hide from the immune system in human lung and nasal cells. The nsp15 endoribonuclease is important in promoting virus replication and influencing disease severity. 1/ Image
SARS2 variants lacking this activity exhibit impaired replication & cause milder disease, highlighting nsp15 as a key virulence factor. This underscores the importance of nsp15’s endoribonuclease activity in both promoting virus replication & influencing disease severity. 2/ Image
The viral variants lacking nsp15 endoribonuclease activity elicited higher innate immune responses and exhibited reduced replication in human stem cell–derived lung alveolar type II epithelial cells, as well as in the lungs of infected hamsters. 3/ Image
Read 5 tweets
Jun 16
Researchers developed a 23-amino acid peptide that mimics ACE2 and effectively binds the SARS-CoV-2 spike protein, preventing viral entry. 1/ Image
The peptide demonstrated potent antiviral activity against both the original and Omicron strains, with a therapeutic index greater than 20, indicating strong potential for therapeutic use. 2/ Image
Moreover, future viruses from this family of coronaviruses may likely use ACE2 as their host cell receptor, as recently demonstrated in the MERS Virus of bats and, therefore, the ACE2 decoy therapeutic may have future applications as well. 3/ Image
Read 4 tweets

Did Thread Reader help you today?

Support us! We are indie developers!


This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Don't want to be a Premium member but still want to support us?

Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal

Or Donate anonymously using crypto!

Ethereum

0xfe58350B80634f60Fa6Dc149a72b4DFbc17D341E copy

Bitcoin

3ATGMxNzCUFzxpMCHL5sWSt4DVtS8UqXpi copy

Thank you for your support!

Follow Us!

:(