Unit 4 - Immunology and Public Health

Unit 4 – Immunology and Public Health 1. The Immune System 2. Infectious Diseases and immunity Non-specific defences Specific cellular defences Transmission and control Active Immunisation and Vaccination and the evasion of immune responses

By the end of this section you will be able to ….. 2. Infectious Diseases & immunity b) Active immunisation, vaccination and evasion By the end of this section you will be able to ….. describe the process of antigenic variation give examples of pathogens that use antigenic variation describe why antigenic variation poses a problem to public health Describe how to set up an experiment to view the antibody-antigen interaction (PS)

Evasion of specific immune responses Not all diseases can be eradicated by vaccines. Some pathogens have evolved mechanisms that evade the immune system and therefore vaccines are of no or limited use. Pathogens can either: Undergo antigenic variation Malaria, Influenza, Trypanosomiasis (sleeping sickness) Directly attack the immune system HIV and TB

Let’s play Chinese Whispers! Re-cap What is antigen? Describe the specific immune response Describe the role of memory cells Let’s play Chinese Whispers!

Malaria To prevent the red blood cells, which the malaria protozoa hide in, from being destroyed they present a protein on the cell’s surface which causes it to stick to a blood vessel wall. It is also able to switch between many genes for this protein preventing the immune system producing appropriate antibodies in time.

Evolution of the FLU virus In this diagram, the antigens can change in two ways, but importantly, it means that the antibodies produced by memory cells cannot bind to them and inactivate the pathogen.

Trypanosomiasis A protozoa called Trypanosoma brucei causes the fatal disease called trypanosomiasis or ‘sleeping-sickness’. It has a glycoprotein coat which can contain one of many different antigens. About 1% of them can vary the antigen and replace the whole ‘coat’ when the immune system attacks. The new coat has different antigens so the immune system has to start again, giving it time to reproduce before destroying another 99%.

Survive and change Survive and change

Videos  Malaria: http://www.youtube.com/watch?v=qvlTOhCmxvY Trypanosomiasis: http://www.youtube.com/watch?v=4aVUrGO97Zg&list=PLXfKWnjanUc3He0aOwo7Uw0MuG0jlQjci Influenza: http://www.youtube.com/watch?v=ug-M1nIhfIA

1. Antigenic variation Some pathogens can change their antigens, avoiding the effect of immunological memory. Antigenic variation occurs in diseases like malaria and trypanosomiasis, and is one of the reasons why they are still so common in many parts of the world. Antigenic variation also occurs in the influenza virus, explaining why it remains a major public health problem and why at-risk individuals require to be vaccinated every year.

Antibody and Antigen interaction – using agar gel (Experiment) Agar gel can be used to observe antibodies reacting with antigens. The agar allows the proteins to diffuse towards each other When they meet they bind together. This is indicated by a white line in the agar.

Antibody and Antigen interaction – using agar gel (Experiment)

Antigen X placed in centre well AIM: To observe the presence of antibodies against antigen X in various pupils Blood plasma of Pupil A Blood plasma of Pupil B RESULTS Blood plasma of Pupil F What conclusion can be drawn from these results? Pupil C wanted to investigate what other antibodies she had. Explain how she could do this. Blood plasma of Pupil E Blood plasma of Pupil D Blood plasma of Pupil C

More Questions! Antigen X is actually from an Influenza virus Antigen X placed in centre well More Questions! Blood plasma of Pupil A Blood plasma of Pupil B Antigen X is actually from an Influenza virus All the pupils have suffered from influenza. Explain why a line did not form between ALL the pupils and antigen X. Explain why a line DID form between 3 of the pupils and antigen X. Blood plasma of Pupil F Blood plasma of Pupil E Blood plasma of Pupil D Blood plasma of Pupil C

Antigen H placed in centre well More Questions! Blood plasma of Pupil A Blood plasma of Pupil B Antigen X was replaced with an antigen from a different virus (antigen H). Only Pupils A and E have been vaccinated against this virus. Predict the results that would be observed from this experiment. Blood plasma of Pupil F Blood plasma of Pupil E Blood plasma of Pupil D Blood plasma of Pupil C

Can you now …. describe the process of antigenic variation give examples of pathogens that use antigenic variation describe why antigenic variation poses a problem to public health Describe how to set up an experiment to view the antibody-antigen interaction (PS)