Adjuvants - Certain substances, when administered simultaneously with a specific antigen, will enhance the immune response to that antigen. Such compounds are routinely included in inactivated or purified antigen vaccines.
- Adjuvants in common use:
- Aluminium salts
- First safe and effective compound to be used in human vaccines.
- It promotes a good antibody response, but poor cell mediated immunity.
- Form precipitate with antigen, making complex more antigenic
- 2. Liposomes and Immunostimulating complexes (ISCOMS)
- 3. Complete Freunds adjuvant is an emulsion of Mycobacteria, oil and water
- Too toxic for man
- Induces a good cell mediated immune response.
- 4. Incomplete Freund's adjuvant as above, but without Mycobacteria.
- 5. Muramyl di-peptide
- Derived from Mycobacterial cell wall.
- 6. Cytokines
- IL-2, IL-12 and Interferon-gamma.
- Possible modes of action:
- By trapping antigen in the tissues, thus allowing maximal exposure to dendritic cells and specific T and B lymphocytes.
- By activating antigen-presenting cells to secrete cytokines that enhance the recruitment of antigen-specific T and B cells to the site of inoculation.
Subunit Vaccines - Immune response can be stimulated by one or a set of viral proteins.
- These can be a lot safer than attenuated or inactivated vaccines
- The subunits included are determined by identifying which proteins the antibodies recognize.
- Subunits vaccines
DNA Vaccines - DNA vaccines are at present experimental, but hold promise for future therapy since they will evoke both humoral and cell-mediated immunity, without the dangers associated with live virus vaccines.
- The gene for an antigenic determinant of a pathogenic organism is inserted into a plasmid. This genetically engineered plasmid comprises the DNA vaccine which is then injected into the host. Within the host cells, the foreign gene can be expressed (transcribed and translated) from the plasmid DNA, and if sufficient amounts of the foreign protein are produced, they will elicit an immune response.
- in recent years a new type of vaccine, created from an infectious agent's DNA called DNA vaccination, has been developed. It works by insertion (and expression, triggering immune system recognition) into human or animal cells, of viral or bacterial DNA. These cells then develop immunity against an infectious agent, without the effects other parts of a weakened agent's DNA might have. As of 2006, DNA vaccination is still experimental, but shows some promising results.
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