Vaccines Flashcards
Who realised the connection between people who were in regular contact with cows infected with cowpox not themselves becoming infected with smallpox?
When was the last natural case of smallpox?
Who developed the first attenuated Rabies vaccine?
Edward Jenner in 1796.
1977.
Louis Pasteur in 1985
What is a vaccine?
The name derives from Vacca (Latin for cow) due to Edward Jenners involvement. A Vaccine is a non-toxic antigenic preparation that are injected, inhaled or ingested. Induces a specific immune response against pathogen without the disease process.
What would an ideal vaccine do?
It should prime the recipients immune system to generate immunological memory.
Should confer lifelong immunity with a single immunisation, have no side effects and be >95% effective.
Should be simple, inexpensive, easily transportable and stable in extreme heat/moisture.
What are the reasons for vaccination?
Antimicrobials mostly used for treatment,
May be used for preventing infection and disease,
Antimicrobials are not always acceptable for prevention,
Vaccines prevent disease,
They are cost effective,
They are cheap,
They offer efficient protection
What are the requirements of a good vaccine?
They must be safe, Effective, Cheap, Easy to administer, Preferably oral, Defined composition, Known mode of attenuation in the case of live vaccines.
What are the types of vaccine.
Killed attenuated (inactivated)- e.g. Formaldehyde treated.
Live attenuated- specific mutant.
Component/subunit- e.g. Surface protein.
Conjugate- poor antigen covalently linked with immunological carrier.
DNA- correct copy of single gene.
Describe inactivated viruses.
They are most commonly used at present. They are whole culture or bacterial cells enriched with pathogenic determinants, or parts of bacterial cells.
They are inactivated with formaldehyde, and preserved with phenol. Attenuated vaccines are mixed with adjuvant.
Describe the use of inactivated vaccines.
They are administered intramuscularly, generally with two or more injections. This vaccine elicits IgM and IgG antibodies. The vaccine provides poor immunity as local mucosal surfaces and the duration of immunity is poor. If the mother is vaccinated she will have provide passive immunity for her offspring.
What are adjuvants?
Inactivated vaccines contain adjuvants that enhance the immune response to the vaccine. They induce inflammation at the site of the vaccination. Adjuvants can cause local irritation and swelling at the site of vaccination. Adjuvants used are aluminium hydroxide, aluminium phosphate, alum, mineral oil such as liquid paraffin.
Inactivated vaccines contain preserved antigens, preserved through the presence of phenol. List these preserved antigens.
Fimbriae, Capsules, Outer membrane proteins, Cell wall lipopolysaccharides, Iron binding proteins and heat shock proteins, Prototoxins and toxins/toxoids, Other secreted antigens.
How are live vaccines administered?
They are administered parenterally (any way that isn’t enterally, e.g. Intravenously) for systemic humoral and cellular immunity.
They can also be administered intranasally for the immunity in respiratory tract.
Can be administered enterally for intestinal and lactogenic immunity.
What is one aim, benefit and disadvantage of using live vaccines?
The aim of them is to produce a modified organism that mimics the natural behaviour of the original organism but does not cause significant disease.
Replication of the organism provides a sustained dose of antigen and appropriate immune responses.
Possesses limited viability in the host’s environment.
What are the advantages of using live attenuated bacterial vaccines?
Self limiting infection mimicking on a small scale the natural infection.
In theory will produce all antigens normally expressed in vivo by the pathogens.
May stimulate immune responses in ways which resemble those elicited during natural infection.
Can elicit mucosal immune responses if administered via the mucosa e.g. Orally.
What are the potential disadvantages of using live vaccines?
There is the possibility of adventitious agents in the cells and medium.
There is the possibility that the vaccine will revert to wild type (become virulent),
They have a limited shelf life,
They require cold storage,
They provide a risk to immunocompromised individuals.
Give an example of a successful live polio vaccine.
Oral live polio vaccine, gives better mucosal antibody responses than the killed vaccine.
Describe component vaccines.
They contain one or more protective antigens. These can be toxoids, secreted antigens or component/structural proteins. These are becoming increasingly used.
For successful component vaccines, moderate amounts of antigens are required, and they are administered with adjuvant.
What are purified antigen vaccines?
These are vaccines composed of molecules purified directly from the pathogen. For them to be made, the molecules that generate the immune response need to be identified. These can be polysaccharides, proteins or exotoxins.
What are conjugate vaccines?
These rely on covalently linking a protein carrier to a polysaccharide. This converts them into T cell dependent antigens.
The protein carriers include: tetanus toxoid, diphtheria toxoid and outer membrane protein from meningococcus group B.
Has been successful with: haemophilus influenza.
What are the problems with traditional technology when making bacterial (killed) vaccines?
The killed pathogen used may initiate an immune response with a poor efficacy that responds to an irrelevant antigen.
What are the problems with traditional technology when making bacterial (subunit) vaccines?
The critical epitopes may be destroyed through inactivation. They can be poorly immunogenic and may still be toxic if insufficiently treated.
What are the problems with traditional technology when making bacterial (live) vaccines.
They are produced by non-specific methods. The basis for attenuation is usually unknown. Control of this attenuation is difficult and they may revert to virulence in vivo.
Describe the need for mucosal vaccines.
Mortality and morbidity of deaths from infectious diseases is high, with deaths from infectious disease in 2001 being 14 million.
Current vaccines are unaffordable in developing countries, have a poor efficacy and their need for cold storage makes them difficult to transport). Mucosal vaccines could elicit both mucosal and systemic immunity.
Where are most infectious diseases acquired?
What are the defences at these sites?
At mucosal membranes.
Defences are the innate immunity of the anatomic barrier. Additionally the fact that there are mucosal associated lymphoid tissues at these sites such as Peyers patches. These secrete B cells and T cells.
What is the surface area of Mucosal associated lymphoid tissue?
> 400m2
