2 Cells- Vaccines & HIV Flashcards
What do vaccines do?
Help the immune system recognise and destroy pathogens
What is the process of a vaccine?
-Insertion of antigens by injection/oral insertion
-Primary immune response is induced; the antigens inserted are weakened/dead so the vaccine doesn’t cause a full-scale infection with symptoms
-Memory cell production triggered by the immune response
-Immunity provided by memory cells; if the person is reinfected, a fast, strong secondary response will be induced
What are booster vaccinations?
Another vaccine given over time to make sure the memory cells are still in the body
Why are some vaccines in continuous trial?
-Some vaccines are continuously being changed due to antigens evolving at high rates
-Pathogens evolve to avoid detection by the immune system; making vaccines useless
-Pathogens with a high mutation rate (e.g. HIV) are the most difficult to vaccinate for
What is herd immunity?
The concept that if a large enough proportion of the population have immunity against a disease, the entire population are less likely to be infected, as those without immunity are less likely to come in contact with the disease
For a more contagious disease, 90% should be vaccinated
For a less contagious disease, 80% should be vaccinated
What is the benefit of herd immunity?
Offers protection for the most vulnerable people in a population (e.g. newborns and the elderly)
What is passive immunity?
Where an individual receives antibodies from an external source, and they don’t make them. Can be;
-Natural (antibodies transferred to a baby from mother’s breast milk)
-Artificial (antibodies transferred to individual by injection)
What is active immunity?
Where the immune system has created its own antibodies. Can be;
-Natural (antibodies created in response to catching a disease)
-Artificial (antibodies created in response to a vaccine)
What is HIV?
Human immunodeficiency virus (HIV) is a virus that inhibits the immune system
What is the structure of HIV?
-Capsid, protein inside the centre of the virus; contains enzymes and genetic material
-RNA, the genetic material, 2 strands and single-stranded, inside the capsid
-Enzymes; reverse transcriptase and integrase, important to role of HIV in infection
-Viral envelope, encloses capsid
-Glycoproteins on viral envelope surface, bind to cell surface membrane of T helper cells to infect cells
How does HIV replicate?
- The glycoproteins on the surface of HIV binds to receptor proteins on the cell surface membrane of T helper cells
- The capsid is injected into the T helper cells. RNA and enzymes (reverse transcriptase and integrase) are released from the capsid
- Reverse transcriptase converts RNA into DNA, which moves into the nucleus of the T helper cells
- Integrase inserts HIV DNA into T helper cells DNA
- Genes in HIV DNA are expressed in T helper cells. HIV proteins are synthesised and new HIV RNA is made
- New HIV viruses are released from T helper cells, which die. These infect more cells
What is AIDS?
Acquired immune deficiency syndrome (AIDS) is a condition that is caused by HIV infection
What causes AIDS?
When an HIV virus infects a T helper cell and replicates, the cells are killed. As HIV spreads through the body and more T helper cells are killed, the immune system weakens. Due to this, the individual is more susceptible to infections by other pathogens- this is AIDS
What are the symptoms of HIV and AIDS?
Initial HIV symptoms are flu-like (chills and fever) and are seen within 4 weeks of the infection. As the immune system weakens, individuals will be more vulnerable to infections (e.g. tuberculosis) and AIDS sufferers may die from one of them. AIDS can take up to 10 years to develop
Why are antibiotics ineffective against HIV and other viruses?
Antibiotics specifically target the ribosomes and enzymes in bacteria and they cannot be designed to target enzymes in viruses since they use host enzymes and ribosomes to replicate
