Can #SARSCoV2 #variants fully evade #vaccine induced protection? Or even natural protection?
The rapid emergence of too many different #variants shows that the virus is struggling to survive! That is why it’s changing so fast, probably, to prolong its stay in human bodies 1/
Though #vaccines may not be working perfectly against some #VOCs, but those fully vaccinated are protected against severe disease & death. No VOC can completely evade the vaccine induced protection, especially against severe disease & death! Why?.......... 2/
The #variants do not have changes in T-cell epitopes because when you are infected with a variant that evades an antibody, that variant can go to someone else and evade their antibody too. So it spreads through the population.... 3/
But, if you have a variant that evades a T-cell, it is not going to make a difference in the next person because everybody's T-cell #epitopes are different. And so, T-cell variants of viruses generally take many, many, many years to emerge. May be decades? 4/
Further, there are many many more T cells epitopes than of B cells. With fine-mapping of #Spike T cell epitopes very much still ongoing, around 280 #CD4 epitopes have already been identified & many more of #CD8 5/
While some 450 #CD8 epitopes have been described across #HLAI alleles, recognition of only very few of these would be impaired (for some alleles) in an individual primed by natural infection or vaccination to the wild-type virus & then encountering the variant 6/
An additional twist: T cell #epitopes may be gained, lost, or unchanged in a variant compared to original sequence virus. So, there may be even gain of additional T cells epitopes 7/
While most attention on likely 'correlates of protection' centers on #NAbs titer and, to a lesser extent, on #CD4 T cell response, it is likely that #CD8 immunity is important, and this response is strongly correlated with the antiviral CD4 response 8/
There are many people who have #activated T cells & no #antibodies, as people who have antibodies. It is unclear how many of those people with activated T cells and no antibodies actually have immunity. But it is difficult to make some guess in terms of percentage 9/
Are the antibodies totally redundant? No, you see influenza virus T cells are also important, yet when the virus changes its B-cell epitopes, we decide to change the vaccine. It means antibodies do contribute 10/
Antibodies prevent infection, not T-cells. They help in attenuation of the disease & prevent death. Even though my T-cells are great, I still want to have some antibodies. So, the two work together. 11/
Hence, the T-cell immunity is the last defense against an infection....can protect a lot of people in the face of even low Ab response. Some agammaglobulinemic people who don't make Abs but they don't have an unusually severe course, because the T cells are protecting them 12/

• • •

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

12 Jul
For how long protection against reinfection with #SARSCoV2 lasts after a symptomatic #Covid19 disease? Almost FIVE YEARS, according to a new modelling study 1/
papers.ssrn.com/sol3/papers.cf…
The duration of immunity in #SARSCoV2 infected people remains unclear. Recent studies have estimated that the correlate of 50% protection from re-infection was 20% of the mean convalescent #NAbs titre 2/
The sera collected from a cohort of 125 individuals with RT-PCR confirmed SARSCoV2 infections up to 386 days after symptom onset. In the subset of 65 sera collected from day 151 to 386 after symptom onset, all remained positive in PRNT50 3/
Read 10 tweets
11 Jul
A recent #Chinese study shows that the viral loads in the #Delta infections were ~1000 times higher than those in the earlier 19A/19B strain infections on the day when viruses were firstly detected 1/

virological.org/t/viral-infect…
#Delta not only had a shorter incubation period but also has a shorter latent period. So, the time difference stayed the same but with much higher viral load. That's terrible & explains near-vertical waves 2/
Because it binds & replicates faster, #Delta creates a higher viral load which triggers symptoms in a host much faster 3/
Read 8 tweets
11 Jul
Is it okay to label #delta variant as #Covid21?

I think it is too premature to even think so. AFAIK, there is still only one ST of #SARSCoV2. It is nothing but a SCAREMONGERING news! 1/

Like all viruses, #SARSCoV2 will continue to evolve. But it has limited number of moves available. It seems it is near to its ‘end game’. There is just not a lot of space for the spike to continue to change in ways that allow it to evade Abs but still bind to its receptors 2/
#Substitutions that allow the virus to resist antibodies will probably also decrease its affinity for #hACE2. This is exactly what we have seen with #DeltaPlus 3/
Read 5 tweets
10 Jul
Do children produce different types of #antibodies(Abs) against #SARSCoV2 than adults? 1/ Image
Yes, children mostly produced Abs aimed at #Spike protein, which the virus uses to enter cells. Adults generate similar Abs, but also develop Abs against the #Nucleocapsid protein, which is essential for viral replication 2/

pubmed.ncbi.nlm.nih.gov/33154590/
#Nucleocapsid protein is typically released in significant quantities only when a virus is widespread in the body.
What does it mean? The kids lacked nucleocapsid-specific Abs, which suggests that they aren’t experiencing widespread infection. 3/
Read 8 tweets
20 Jun
Can a respiratory #virus infection confer #immunity against the other #respiratory virus? A much-debated issue in the virus immunology for many decades. What is the probable immune mechanism & does it indeed exist? What is the evidence for & against this hypothesis? 1/
It is hypothesized that a respiratory virus infection confers immunity against the same and other respiratory viruses for a short time, perhaps a few weeks. This immunologic mechanism, known as #heterosubtypic ‘temporary non-specific immunity’ 2/
This immune protection is associated with activation of the innate immune response to viral infection mediated by the release of Type I #interferons (IFN) & other cytokines that have broad protective effects against a range of viruses 3/
Read 21 tweets
19 Jun
#Spike protein’ is the major target of #NAbs in infected/vaccinated people. The prefusion conformation of the Spike represents the most relevant target because Abs can successfully interfere w/ infection only if they prevent binding to target cells or prevent fusion itself 1/
Various approaches are adopted to express ‘#Spike’ protein in vivo, such as nucleic acid structures & virus vectors. Alternatively, other vaccine platforms like recombinant protein particles & inactivated vaccines can directly deliver this protein 2/
Most structural studies of the wild-type spike protein exhibited one #RBD in the 'open' conformation. By contrast, 2 or 3 RBDs were observed in the open conformation in the more infective #D614G mutant--the RBD #conformation plays a vital role in the infectivity of SARSCoV2 3/
Read 16 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

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

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!

:(