Ways to fight virus Flashcards
What are some strategies to control infectious diseases?
- vaccine (but not effective if person is already infected)
- antivirals (can stop infection once it has started)
What does the best antiviral drug target?
- Inhibits a specific step in viral replication or pathogenesis (must be potent- block virus replication completely)
- must be safe
What is the current treatment for HIV?
- Highly active antiretroviral therapy (HAART)
- it is a combination of several (3-4) antiretroviral drugs
What is the purpose of a vaccine?
- To elicit an immune response that will prevent or limit disease upon first encounter with the target organism/antigen,
- Prevent disease, transmission and eradicate disease
What are some successful vaccines?
- smallpox
- polio (salk- inactivated virus, sabin- attenuated virus)
- diphtheria (toxoid- inactivates toxin)
What is passive immunisation?
- transfer of immune sera/cells to provide protection
- immediate protection but short term
eg. rabies immune globulin, maternal antibodies transferred to newborn
What is active immunisation?
- Introduction of foreign material into a host to stimulate an adaptive immune response
- Typically involves preparation containing one or more microbial agents or a vector that directly express one or more microbial antigens
What does a good vaccine typically need?
- Something to stimulate the innate immune system (infection- live attenuated or adjuvant)
- T cell epitopes (peptides that can bind to MHC proteins)
- B cell epitopes (relevant site that can neutralise pathogen or toxin
What are the benefits of live attenuated vaccines?
- pathogen replication creates strong innate immune signals
- diverse range of antigens expressed
- prolonged antigen expression
- higher antigen loads
- better t cell response
What are 2 ways attenuation of pathogen can be achieved?
- Through in vitro passage so it no longer grows well in human cells (can;t revert quickly back to wildtype)
- By targeted deletion of virulence genes/determinants
What is subunit vaccine?
- Contains component(s) of pathogen rather than the complete organism. eg. hepatitis B vaccine
What is toxoid vaccine?
- Immunisation with inactive forms of toxins. eg. tetanus/diphtheria
- antibodies bind to native toxin and block activity
What is conjugate vaccine?
- Consist of an antigen coupled to a carrier
- antigen is typically carbohydrate
- can’t stimulate a T cell response so need to be coupled with carrier
- haemophilus influenza B, streptococcus pneumoniae
What are DNA vaccine?
- Plasmids (bacterial DNA) provide ‘stranger’ stimuli to immune system
- elicit weak immune response, used for ‘priming’
What are adjuvants?
- delivery of signals 1,2 and 3 for T cells
- right type of help for B cells
What is a rotavirus?
- major cause of severe diarrhoea in young children
What are the key elements of an expression vector?
- promoter
- multiple cloning site
- origin replication
- antibiotic resistance gene
- epitope tag/reporter gene
- selectable marker (used for eukaryotic cells)
What are features of shuttle plasmids? What are they used for?
- generally quite small and have a greater range of restriction sites
- used in sub-cloning
Which plasmid is commonly used for protein expression in bacteria? What are it’s features?
- pGEX
- encodes for the epitope GST, used for purification
- has tac promoter, Ori, stop codon, amp resistance gene, Lac repressor gene, cleavable epitope (factor Xa)
What are the pros of prokaryotic expression?
- Convenient/easy
- produce and purify protein using the least expensive and easiest reagents and equipment
- best for large scale production of protein
What are the cons of prokaryotic expression?
- lack many of the immunogenic properties
- 3D native conformation
- lack PTMs (post translational modifications) needed for specific activity
