Immunity - Prevention and Treatment

What is immunity?

Immunity is the resistance to infection by invading micro-organisms. 

List types of immunity - providing examples

• Natural passive - breast milk

• Natural active - infected, become sick

• Artificial passive - injection of antibodies

• Artifical active - vaccine

Define naturally occuring immunity

Naturally occurring immunity occurs without any human/medical intervention(eg. Being infected with a pathogen and having an immune response)

Define artificial immunity

Artificial immunity occurs when people are given an antibody or antigen (eg.Being given a vaccine

Define active immunity:

Occurs when the body is exposed to a foreign antigen (either naturally or artificially) and it manufactures its own antibodies as a result of this exposure. 

Define passive immunity:

Occurs when a person receives antibodiesthat are not produced by themselves. 

explain why active immunity is long lived

Whilst antibody levels will naturally decrease over time, this response is longer lived due to the presence of memory cells (immune response triggered). When reinfected with same antigen the memory cells will stimulate antibodies to be produced rapidly, eliminating antigen before infection can produce symptoms. 

explain why passive immunity is short-lived

Antibodies are given so that immunity is established immediately (faster than an initial immune response). Passive immunity is short-lived (no immune response triggered) as antibodies are broken down and excreted. Lack of memory cells mean that antibody levels cannot increase rapidly on secondary exposure to that antigen. 

What is immunisation?

programming an immune response so that body cells can respond rapidly to infecting micro-organisms = developing immunity naturally or artificially. 

What is vaccination?

Artificial introduction of antigens (or pathogenic organisms) so that the ability to produce the appropriate antibodies is acquired without the person having to suffer the disease. 

What is a vaccine and what is their purpose?

A vaccine is the antigen preparation used in artificial immunisation.

Vaccines help to build immunity to pathogens and reduce the spread among populations and are therefore considered a preventative method.

How do vaccines work?

A vaccine (usually in the form of an injection) is given to the individual with a specific weakened or inactive part of the pathogen (antigen). This is why the person does not usually become ill or experience symptoms.

This encourages the body to create an immune response by creating its own antibodies and memory cells

On secondary/subsequent exposure to pathogen the memory cells trigger the rapid production of antibodies 

This response is more rapid and larger than an initial exposure and so the person will not experience any symptoms of the disease or the symptoms will be less severe.

Name and describe the types of vaccines:

• Live attenuated vaccines - living attenuated micro-organisms with reduced virulence = reduced ability to produce disease

• Inactivated vaccines - Dead micro-organisms. Immunity is shorter lived than live attenuated vaccines. 

• Toxoid vaccines - Inactivated bacterial toxins 

• Sub-unit vaccines - Fragment of a micro-organism

• Conjugate vaccines - contain pieces of bacterial coat including the carrier protein combined together

• Recombinant vaccines - genetically engineered vaccines where a virus protein is inserted into another virus

Methods of vaccine delivery:

• Most via infection

• Orally

• Fine nasal/ orgal spray

• Skin patches

• Ingestion in foods

What is the aus vaccination schedule and why is it so?

Most vaccinations don’t start until a child is 2 months old, and for most diseases more than one vaccination is necessary

Vaccination should not start too soon after birth, as the child’s blood contains antibodies from its mother via placenta or breast milk

If a newborn is given a vaccine, antibodies from the mother eliminate the antigens in the vaccine. A few months are also necessary for the child’s immune system to become activated & therefore able to prevent child from getting the disease.

what is an exception to the aus vaccination schedule, and why?

Exception: Hep B vaccine, due to the risk of infant being infected during birth. First vaccine given soon after birth to provide early protection for the baby

Impact of vaccination of populations (mass vaccination)

Use of vaccines in mass immunization programs has either eradicated or greatly reduced incidence of certain diseases throughout the world (e.g. Smallpox)

Define herd immunity:

The resistance to the spread of a contagious disease within a population that results if a sufficiently high proportion of individuals are immune to the disease, especially through vaccination.

Impact of herd immunity:

The reduction in the chance of disease in most susceptible individuals and increases the immunity of the populations

Requirements for herd immunity:

High portion of individuals must be immunised for herd immunity to be effective. The proportion of the population that needs to be immune to protect the population varies between diseases. Highly contagious diseases, such as measles, need a very high percentage of population to be vaccinated to provide protection. Smaller percentage is needed for less contagious diseases, such as Ebola

reason for and impact of vaccination declines

reason: As incidence of infectious diseases decline, people become complacent & may decide the risk of side effects from vaccine is higher than the risk of contracting the disease itself

impact: serious outbreak may occur

Types of factors individuals may consider for getting a vaccination

• Health

• Social

• Cultural

• Economic - keep in mind that if it is a vaccination schedule implemented by Aus, it is free

List and describe health factors to consider for vaccination

■Allergic reactions: One of the main risks. May occur, not so much from vaccine itself, but from a reaction to the medium in which the vaccine was cultured. List of components of each vaccine. E.g. Influenza vaccine manufactured in eggs

■Preservatives: Individuals concerned about vaccines claim that they can affect nervous system and lead to other health issues. After many investigations, no connection has been identified. Instead, it appears any reaction is due to chance

List and describe social factors to consider for vaccination

Ethical concerns with the use of animals to produce vaccines: Virus can only reproduce in living cells, manufacture of viral vaccines requires host tissue. E.g. Influenza cultured in chicken embryos & Japanese encephalitis in brains of mice

■Ethical concerns with the use of human tissue to produce vaccines: Many vaccines require human tissue because some viruses that cause disease in humans do not grow well in cells derived from other species. Human tissue avoids problems of cross-species infection from possible unknown viruses. E.g. Rubella manufactured using cultured human cells from foetuses

■Ethical concerns with informed consent: Key principle of ethics is informed consent. Some concern that trialling vaccines in developing countries may lead to their use in populations with low standards of education. Meaning people aren’t fully aware of the risks and may be open to exploitation by vaccine manufacturer

■Ethical concerns with testing on animals: most vaccines tested on animals before humans, to identify problems that could occur in humans. Legislation limits the way animals can be used; however, some people believe they should not be used at all

■Concerns about promoting sexual activity in teenagers: Some people believe vaccinating against HPV will encourage teenagers to be sexually active

■Availability: Vaccines may not be readily available in all areas

List and describe cultural factors to consider for vaccination

■Religious beliefs: Religious belief has often been cited as a reason for some Australian parents refusing to immunize their children. However, none of the major religions in Australia are opposed to immunization. There are a few religions, that rely on faith healing, that are opposed to vaccines. Also, the methods used to produce vaccines may contradict religious beliefs & lead to a choice not to participate in immunization programs

List and describe economic factors to consider for vaccination

■Cost of vaccine: may be too expensive for some people to afford

■Commercialisation: the interests of commercial vaccine production may affect its use

Describe what autoimmune diseases are & treatment of them

Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body.

The body actually attacks it’s own cells because the immune system mistakes some part of the body as a pathogen and attacks it. 

Most involve excessive activity of specific antibodies and t-lymphocytes. 

This may be restricted to certain organs or involve a particular tissue in different places. 

treatment: typically with immunosuppressive drugs which decreases the immune response. 

What are antibiotics:

Antibiotics are drugs used to fight infections of micro-organisms, particularly bacteria, but also fungi. They are effective for only specific types of bacteria/fungi.

Requirement of antibiotics:

must be toxic to the micro-organism but not to the patient

Define and describe antibiotic resistance - including the problem our attempts for solutions have caused

Antibiotic resistance is when the bacteria which are treated by antibiotics evolve to become resistant/ are no longer effected by the drug

Antibiotic resistance develops by natural selection, where some bacteria would be more resistant to the antibiotic than others of the same species. 

If resistant bacteria survive antibiotic attack they will then reproduce and pass on resistance to the next generation. 

Often occurs when antibiotics are prescribed to prevent rather than treat infections or when used as ‘growth promoters’ in farming. In the past this has been overcome by changing to a different type of antibiotic to treat the bacteria. Over time this has become a major problem, as bacteria have become resistant to most (multiple drug resistance) or all (total drug resistance) available antibiotics

For this reason, prescription from the doctor is required (in most countries) before antibiotics are given.

Name and descibe types of antibiotics:

Bactericidal: kill bacteria by changing the structure of the cell wall/membrane OR by disrupting the action of essential enzymes.

Bacteriostatic: stop bacteria from reproducing usually by disrupting protein synthesis

Define broad-spectrum and wide spectrum antibiotics:

Broad-Spectrum: affect a wide range of different types of bacteria

Narrow-Spectrum: only effective against specific types of antibiotics. 

what are antiviral medications

They are used to treat viral (viruses) infections.

How are antivirals desgined and why is this so?

antivirals are designed to inhibit (supress) the development of the virus.

Reason: Due to the nature of a virus finding new drugs to treat viruses can be difficult. Because the host cell produces the new virus particles, any drug that interferes with virus replication is likely to be harmful/toxic to the host cell.

How do antivirals inhibit (suppress) the development of the virus?

Antivirals target various stages of the viral lifecycle:

–block the entry of viral DNA/RNA into host cell

–interfere with reverse transcriptase enzyme needed to transcribe viral RNA into DNA

–prevent the release of virus from host cell

Three differences between antibiotics and vaccines: