During the ongoing battle to control and prevent death by infectious disease, scientists sought to focus on the role of our adaptive immune system and improve the effectiveness of this setup. They attempted to do this by developing our immunological memory. This relates to the concept that subsequent exposure to an identical strain of pathogen will result in an enhanced and longer lived memory response to reduce the symptoms and even at the best of times prevent infection. Vaccines lead to a term referred to as Active Immunity. This is when exposure to an antigen from infection or vaccine stimulates memory.
We are born with maternal antibodies, however, these soon diminish and we are rapidly exposed to the potential dangers of primary infections that occur in the outside world. In order to avoid the undesirable symptoms that follow an infection scientists began to develop and administer vaccinations.
Vaccinations have eradicated Smallpox. They have mercilessly forced Polio to the brink of extinction. Measles along with Hepatitis A and B are nowadays not usually a worry providing you are vaccinated. In contrast, successful vaccinations are yet to be developed for diseases such as AIDs and Herpes, to name a few. This is due to the fact that they are Chronic Infections. In these cases the pathogen is able to evade the Immune System or subvert it into making ineffective responses that never deal with the core problem.
There are three types of vaccine; Live, Killed and Subunit. In this essay the main focus will be regarding the Subunit form as it covers the topic of administrating Polysaccharide and Polysaccharide-Protein vaccines.
To avoid the problems seen with whole organism vaccines we use Subunit ones. Live vaccines are known not to be suitable for patients who are already immunosuppressed as the potency is too strong for them to be able to control safely without acquiring any symptoms. The main aim is to trick the body into producing an antibody response. Polysaccharides in some bacteria coat the protein components (capsule). These components would otherwise aid detection of an intruder leading to action being taken. It is for this reason that plain polysaccharide vaccines were developed to provoke the immune system.
Polysaccharide vaccines are a type of Subunit vaccine. However, they have a reputation of being poor immunogens (a substance that provokes an immune response). The reason for this lies in the fact that these types of vaccines rely on T-independent B cells the immunogens are therefore known as T-cell independent Antigens. These can comprise of repeating polymers i.e. dextrin, bacterial polysaccharide and cell wall components e.g. Lipopolysaccharide (LPS) and Peptidoglycans (Narin and Helbert, 2007). B cells responding to polypeptide antigen require two signals to become fully activated. The first signal comes from cross-linking of the B-cell receptor and the second comes from T-cell receptor recognition of peptide-MHC complexes...