New Vaccines Flashcards
What are the regions of a DNA vaccine vector?
Expression unit - Promoter, Ag gene sequence, enhancer, ISS, Poly A tail
Production unit - Selectable market, OriR
What is a gene gun?
Bioballistic particle delivery system - can deliver DNA/RNA under certain conditions into tissues using high pressure in a vaccum
What are the advantages of DNA vaccines?
Safe - no live pathogen
Effective - only one step cloning process
Can included multiple vaccines in same vector
Can change gene of antigen if mutations occur (Influenza)
Can use eukaryotic promoter - endogenous protein
Elicit CD4/CD8 T cell and B cell
Few side effects (only minor inflammation at site of entry)
What are the disadvantages?
Low immunogenicity in trials
No polysaccharide capsule
Can induce chronic inflammatory response if DNA stays in cells too long
How does DNA vaccine work?
Plasmid internalised into cell, converted to RNA and protein.
Somatic cell (mycoyte) - proteosome - TAP - MHC I
APC (dendritic cell, macrophage, B cell) - MHC I and II
- can phagocytose somatic cell to induce MHC II - cross priming
Plasmid also contains CpG motifs to induce TLR 9 (PRR)
How many DNA vaccines are in ph3 CT?
84 - none approved yet for humans
Give some examples of DNA vaccines?
Zika virus - DNA plasmid with E and PRM outer coat proteins - phase 2 CT
Approved for veterinary use by FDA for West Nile Virus in horses
First DNA vaccine trial - HIV - not very successful, showed no CD4 and CD8 T cell increase, and only limited antibody production against gp120
What is a dendritic cell
APC - first cell to take up Ag - also responds to PRR (express costimulatory molecules) - migrates to lymph nodes to activate antibody
What are the methods an APC can take up things?
Engulfment of apoptotic bodies
macropinocytosis
Receptor mediated endocytosis (PRR)
What are the type of APC used in DC viruses?
CD34+ DC
What are the ways of getting a tumour antigen into the DC?
Load with known peptide Ag (useful when we know the antigen responsible for the tumour e.g. melanoma)
Cellular lysates ( useful when we dont know the Ag - lyse tumour and sprinkle contents over DC - DC takes up contents)
Microsomes (Fragments of ER and Ribsosomes from tumour cells)
What is the process for producing DC vaccines?
Collect DC precursors from blood of patient
Differentiate ex-vivo and load with tumour antigen. This takes around 3 days.
Resulting cells are aliquoted and frozen in liquid nitrogen
Patient can be vaccinated sub cutaneous with OWN DC
What are some examples of DC vaccines?
Ovarian Cancer
Wilms Tumour
