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What are the 4 different types of vaccine?

Which type of vaccine is most often used to induce Ab formation against polysaccharides?

1) a vaccine consisting of microorganisms, which are killed (e.g., polio vaccine) or inactivated (i.e., tetanus toxoin).

2) A vaccine, which is an attenuated or weakened agent (e.g, small pox vaccine) that cannot cause pathology but provokes a long lasting immunity.

3) subunit vaccines, which are components of the microorganism (e.g. heptatitis vaccine).

4) conjugate vaccine which consist of subunit of a microorganism, which cannot elicit an immune response are typically conjugated to a foreign protein which does elicit a response. In this way antibodies, which offer protection, can be made to the subunit component of the microorganism. This is most often how antibodies to polysaccharides are made.



What is the rationale for using an inactivated vaccine over an attenuated one?

The rationale for using one versus the other depends on the safety and immunogenicity of the inactivated and attenuated agent. Chemical modificationmmay make antigens ineffective. However, attenuated/weakened agent/pathogens may not provoke a protective response and in fact may cause pathology and/or side effects.


What are adjuvants? What is their function?


Adjuvants enhance generation of protective immune responses by increasing activity of APCs. Purified antigens are usually not strong enough to provoke an immune response and most acellular (e.g., tetanus toxoids) vaccine require adjuvants. One such adjuvant is aluminum salts. These create ionic charges on the surface of antigen and increases antibody production.

Pertussis toxoid is a strong adjuvant is often mixed with tetanus and diphtheria toxoid to allow for strong immune responses against all toxoids in the mixture.

One of the strongest adjuvants is sterile bacteria components (e.g., cell wall). It is thought that isolation of the bacterial components themselves may enhance immune response as well. Despite the fact that they augment very strong immune responses, they also induce severe inflammatory response, which makes them unsuitable for use in humans.

Adjuvants work on dendritic cells by provoking TLRs (see previous lectures on Innate Immunity and Phagocytosis/antigen presenting cells). Dendritic cells are critical in priming immune responses and development of memory T-cells and inevitably memory B-cells (though T-cells). Thus the thought of using TLR agonist as adjuvants is intriguing and may some day prove to be effective in developing much needed vaccines.


Explain how vaccines to polysaccharides are produced.

Remember from the Antibody Synthesis lecture that polysaccharides are T-independent antigens. T-independent compared to T-dependent antigens do not make memory B-cells, have no affinity maturation and are only IgM. Thus, by coupling polysaccharides to proteins you will be able to convert T-independent antigen into T-dependent antigens.


Explain the hapten carrier effect.

Haptens alone do not elicit response because they are not large enough. If attach haptens to carrier molecule, Antibodies are developed against the hapten. Most Abs are for hapten, some for the carrier, and some to both.