30-31 - Viruses As Research Tools and Assay of Animal Viruses Flashcards
(36 cards)
Name some of the useful properties of viruses which we can exploit…
- Trigger immune response
- Natural gene delivery vehicles
- Cytopathic (cell killing) effects
An early example of viruses used in medicine is…
Viral vaccines
(Edward Jenner using cowpox to innoculated against smallpox)
Types of vaccines in general use (4)…
- Live heterologous (cowpox - smallpox)
- Live attenuated (weakened, MMR)
- Killed whole virus (Salk vaccine for polio)
- Subunit (purified from virus (Influenza A) or recombinant proteins (HBV, HPV))
Describe host range attenuation (4)…
- Virus isolated and cultured on human cells
- Incubated on cells from a new host (e.g. monkey) 🙊
- Spontaneous mutation allows viral growth on monkey cells
- This virus can be used as a vaccine as it can’t grow on human cells
The disadvantage of killed and subunit vaccines is that they…
Only induce a humoral (antibody) response, when cell mediated response is often critical to an anti-viral immune response
The advantage of live vaccines is that they elicit…
Both humoral (antibody) and cell-mediated immune response
Give two reasons why it may not be possible to make a live vaccine for a particular virus…
- It can’t be grown in culture
- It cant be attenuated to a safe level
A potential solution to the problems associated with live vaccines and killed/subunit vaccines is…
Live recombinant viral vaccines
To create a live recombinant viral vaccine, the immunogenic gene from the pathogenic virus is…
Ligated into the genome of an existing viral vector
Give examples of applications of viral vectors in research (In vitro and In vivo)
-
In vitro
- Investigation of protein function
- Express a protein not normally expressed
- siRNA delivery to block gene expression
- Investigation of protein function
-
In vivo
- To create transgenic animals 🐁
List 5 commonly used viral vectors…
- Bacteriophage
- Baculovirus
- Adenovirus**
- Pox virus (Vaccinia)*
- Retroviruses*
*Mammalian host cells
**Specific human host cells
Bold = safety issues
Other than viral vaccines, give 3 further examples of viruses used as medical tools…
- Gene therapy (delivery of functional gene)
- Oncolytic therapy (targeting cancer cells)
- Phage therapy (targeting bacterial cells in infection)
Distinguish betwen ex vivo and in vivo approaches to gene therapy…
-
ex vivo (outside body)
- cells removed from body-> gene introduced -> cells returned
-
in vivo (in body)
- gene is introduced directly into body via virus or other gene vector
An example of ex vivo gene therapy is…
CAR-T (chimeric antigen receptor T cell) therapy
Phage therapy relies on enzymes produced by some bacteriophages, known as…
Lysins (or endolysin) which cleaves host cell wall
Oncolytic virotherapy is the use of a…
Lytic virus to destroy cancer cells
Outline the pros and cons of virotherapy…
-
Pros
- Can be combined w/ other cancer treatments
- Excellent safety profile
- Dual action (direct oncolysis and immune-mediated anticancer effect)
- Alternative cell killing mechanisms - overcome resistance
-
Cons
- Resistant cancer cells
- Limited replication and spreading (because tumour cells must be effectively destroyed)
- Antiviral immune response
Oncorine
First oncolytic virus approved for clinical use. Genetically modified adenovirus H101 for nasopharyngeal carcinoma
How can we detect and count viruses in the lab (2)…
- Cell based assays
- Protein based assays
(other techniques exists, but not covered in this module)
4 Steps to growing viruses in the lab…
- Grow cells in tissue culture
- Infect the cells with virus
- Incubate and observe for effects of viral infection
- Harvest cells/ medium to measure viable virus particles per ml
MOI (multiplicity of infection) ( = or ≠ )particles per cell
MOI (multiplicity of infection) ≠ particles per cell
The two main types of cell-based assay are…
- Plaque assay
- End-Point Dilution Assay (EPDA)
Plaque assays detect infectious virus particles. Each plaque observed represents…
1 viable infectious particle (PFU)
Limitations of plaque assays…
- The virus used must cause a visual cytopathic effect
- requires 7+ days
- requires maintainence of sterility
