MRNA vaccinations (Lecture 14)

Innate immune system

non specific” immunity refers to immunity present designed for protection even in absence of antigen

Lymphatic system makes lymphocytes which attack foreign elements (innate) 

sin> primary barrier 

In lungs> cilia which knock out foreign objects

Adaptive

 immunity refers to activation by a specific antigen before adaptive immunity becomes activated, antigen has to be processed and analyzed 

Sex linked differences in immunity

in general women are more prone to autoimmune diseases 

>people that don't grow up in sterile environments have less incidence (pre-exposed) 

Men > non reproductive cancers 

Sex chromosome encoded genes and sex hormones modulate immunity directly or via microbiome

Reproductive status > female biased infectious

Pathogen associated damage> male bias 

How do cellular clock affect viral cycle

 influence viral infection ( from regulation of entry receptors to lipid dependent pathways ) (nucleic acid sensing and activity of immune cells regulated by cellular circadian clocks 

Sars covid characteristics

rs covid > (+) stranded RNA virus 

Phase 1: early phase ; anti virals

Phase 2: pulmonary phase: liquid in lungs

Phase 3: systemic hyper-inflammation and anti inflammatories 

How do vaccines work

Vaccine elicits production of memory B and T cells 

Neutralizing antibodies (vaccines target the viral proteins on surface that trigger binding to host 

Moderna’s development for vaccinations

Generate a mRNa in vitro to certain target> embedded the mrna inside particle > inject particle > mRna gets taken up by host cell and translated

Advantage: rapidly produced

Disadvantage: unstable  (can stabilize by using m5c and pseudouridine for preferred base-pair alterations vc lower immunogenicity while increasing translation efficiency (5’ cap, and ROf and poly a tail”

Modifications to increase mrna stability

-natural mrna undergo modifications form 5’ cap to methylation.

5’ poly a tale known o stabilize mRNa and enhance translation.

Otherwise Target it 

Encoded enzymes to cap mrna and modify internal nucleotides

Mrna will trigger an immune response  

Used a pseudouridine > to increase stability and decrease innate immunity 

> ability to package and deliver MRNA

How deliver synthetic mRNa (problem)

Problem: mrna is larger than cells also dense negative charge repulses cell membrane 

Mrna vaccine has to avoid nucleic acid degradation and also allows mrna to get into cell 

Lipid nanoparticles 

What sequence (nano spike protein)

Protein products are made by cleavage of larger proteins 

Prior work on respiratory syncytial virus showed importance of perfusion and post fusion changes producing a vaccine eliciting a stronger production

Mrna vaccine has to avoid nucleic acid degradation and also allows mrna to get into cell 

Lipid nanoparticles

Previous work on RSV (prefusion and post fusion)

Prior work on respiratory syncytial virus showed importance of perfusion and post fusion changes producing a vaccine eliciting a stronger production

> NAB were found in RSV (strong neutralizing antibodies)

> antibodies on F protein required for binding (which adopts a post fusion conformation) 

Pre fusion > post conformational changes

destroys NAB recognition

Strategy to improve vaccine–change structure of F protein so that its locked into proline locked into pre-fusion structure

Strategy to put into mRna vaccine

Once sequence published > adding 2aa for prolines locking the surface proteins involved in fusing cell into perfusion conformation> allows raising antibodies that will act as neutralizing

Large scale production of target proteins

> (challenge was purifying target protein from all other proteins)

Less of a problem for proteins can be secreted into culture media

Also post translational modification  

Large scale produciton of target mrna

faster (less components) (done invitro) plasmid or pcr products containing a coding region and upstream promoter mixed w AUGC in a tube 

ACE2 binding (AB1)

SARS COVID and vaccine elicit anitbodies that the virus uses to bind to ACE2

which neutralizes the spike down regulation

Antibodies (Ab1):

• These are the primary antibodies that the immune system generates to protect against the virus. They specifically bind to the spike protein to block the virus from interacting with the ACE2 receptor.

• These protective antibodies are referred to as Ab1.

CDR3

Part of the structure of antibodies that binds to the spike protein. This is crucial because the specific structure of the CDR3 region determines how well the antibody can bind and neutralize the virus.

AB2

• The body can also generate a different set of antibodies called Ab2. These antibodies target the parts of Ab1 (the antibodies that neutralize the spike protein).

• How Ab2 Works:

  • Binding to Ab1: Ab2 can bind to Ab1 and form an immune complex, leading to the clearance (destruction) of the Ab1 antibodies. This reduces the efficacy of the neutralizing antibodies (Ab1), meaning it could potentially impair the immune response against the virus.

  • Mimicking the Spike Protein: Some Ab2 antibodies can have regions that resemble the spike protein itself. These regions are known as paratopes.

    • These paratopes could interfere with the spike protein’s function by binding to the ACE2 receptor directly, just like the spike protein does.

    • This could block the ACE2 receptor from functioning normally in several ways:

      • Blocking ACE2 activity: By preventing the spike protein from binding to ACE2, Ab2 could prevent the virus from entering the cell, but it could also impair ACE2’s normal biological function.

      • Triggering or inhibiting ACE2 function: Ab2 could cause ACE2 to either be activated (stimulated) or downregulated (reduced expression).

      • Inducing an immune response: Ab2 could also provoke immune cells to attack the ACE2-expressing cells (cells that carry the ACE2 receptor), leading to further immune reactions.

Vaccinations for cancer

Helps produce neoantigens which are unique molecules that help immune cells identify cancer

>safely expose patients and induce T cell activation (anti tumor response) > eaten by cells and processed by APC which present antigens to surface safely destroying tumors