vaccines, diseases, monoclonal antibodies

• What is a vaccine?

  A vaccine is a suspension of antigens that are intentionally put into the body to induce artificial active immunity. 

  There are two main types of vaccines: Live attenuated/Inactivated

  Vaccinations produce long-term immunity as they cause memory cells to be created. The immune system remembers the antigen when reencountered and produces a secondary response.
• What are the advantages and disadvantages of vaccines?

  Vaccines can be:

  • Highly effective with one vaccination giving a lifetime’s protection and harmless
  • People can have a poor response
  • Antigenic variation in the antigens of pathogens causes the vaccines to not trigger an immune response or diseases caused by eukaryotes (eg. malaria) have too many antigens on their cell surface membranes making it difficult to produce vaccines that would prompt the immune system quickly enough
• What is herd immunity?

  Herd immunity arises when a sufficiently large proportion of the population has been vaccinated which makes it difficult for a pathogen to spread within that population.

  Those who are not immunised are protected and unlikely to contract it as the levels of the disease are so low.

  It is very important as it allows for the individuals who are unable to be vaccinated (e.g. children and those with weak immune systems) to be protected from the disease
• What is active immunity?

  • Active immunity is acquired when an antigen enters the body triggering a specific immune response (antibodies are produced)
  • Active immunity is naturally acquired through exposure to microbes or artificially acquired through vaccinations
  • Active immunity can take time to develop
  • The body produces memory/plasma cells, giving the person long-term immunity
• What is passive immunity?

  • Passive immunity is acquired without an immune response. Antibodies are not produced by the infected person
  • As the person’s immune system has not been activated then there are no memory cells that can produce antibodies in a secondary response. If a person is reinfected they would need another infusion of antibodies
• What is artificial/natural passive immunity?

  Artificial passive immunity occurs when: 

  • People are given an injection / transfusion of the antibodies. The antibodies were collected from people whose immune system had been triggered by a vaccination to produce tetanus antibodies

  Natural passive immunity occurs when:

  • Foetuses receive antibodies across the placenta from their mother.
  • Babies receive the initial breast milk from mothers which delivers a certain isotype of antibody
• What is HIV and how can it be transmitted?

  Human Immunodeficiency Virus is a retrovirus. The virus can only be transmitted by direct exchange of body fluids. This means HIV can be transmitted in the following ways:

  • sexual intercourse
  • blood donation
  • from mother to child across the placenta
• What is HIV made up of?

  • Two RNA strands
  • Proteins - including the enzyme reverse transcriptase
  • A protein capsid
  • A viral envelope consisting of a lipid bilayer and glycoproteins 
  • Attachment proteins
• How does HIV replicate?

  • The attachment protein attaches to a receptor molecule on the helper T-cell. 
  • The capsid is released into the cell and releases the RNA into the cell 
  • Inside the cell, RNA converted into DNA using reverse transcriptase. 
  • From this, viral DNA is inserted into the human DNA.
  • DNA transcribed into HIV RNA, then HIV mRNA translated into viral proteins
  • The viral proteins are assembled into new viruses, which are released from the cell and infect other cells.