Phagocyte

1
Phagocyte
phagocyte moves towards the bacterium
engulfs it
digests it
2
B cells
Receptor
B Cell
Naïve B cell
3
B cells and antibodies
B cell attaches to antigen cloning of daughter
cells
daughter cells produce antibodies
Antibodies neutralise antibodies
phagocyte consumes an antibody coated virus
4
Cytotoxic CD8 cells
CD8 cells can recognise markers on the outside of
infected cells
CD8 destroys infected cell which stops cell from
producing more virus or bacteria
5
Antigen presenting cells
These cells can engulf invading organisms
Antigens presented to CD4 cells
The foreign organism is broken up into smaller
pieces
6
CD4 cell
7
Analogy for the immune system
8
Naïve and Memory B cells

• Naïve B cell
• Once activated it divides many times making two
  types of clones
• The plasma cell which makes and releases large
  amounts of the appropriate antibody
• The memory B cell which can live for years
• Memory B cells
• The existence of memory B cells means that the
  body can respond much more quickly

9
CD4 and CD8

• Cluster of Differentiation
• Molecules on the surface of the cells that help
  the T cell attach to the antigen
• CD4 cells
• Th1 (humoral response) Th2 (cell mediated
  response) Th0 (??)
• CD8 cells
• Cytotoxic lymphocytes (CTL)
• CD45RA Naïve cells
• CD45RO Memory cells

10
CD4 count viral load over time
11
HIV virion
Fatty (lipid bilayer) membrane
Glycoprotein gp120
Protein p18
Reverse transcriptase enzyme
Protein p24
12
Vaccine - Ideal characteristics

• Prevent transmission by mucosa injecting
• Excellent safety profile
• Single dose administration
• Offers protection for a long time
• Low cost
• Stability and ease of administration
• Works against a wide range of different strains

13
Immune system responses

• Humoral response
• Based on antibodies and the B cells that produce
  them
• Cell-mediated response
• Based on cytotoxic CD8 cells
• Mucosal immunity
• The above but concentrated in the mucosal
  membranes where most transmission occurs
• Current trend
• is to aim to stimulate a sufficient HIV-specific
  CTL response to control or prevent HIV infection

14
Types of vaccine

• Live attenuated vaccines
• Defective or weakened form of the virus
• Previous example original smallpox vaccine,
  vaccinia
• Research in monkeys indicates may slowly lead to
  immune disease
• Inactivated or 'killed' vaccines
• Recombinant sub-unit envelope vaccines
• Recombinant vectored vaccines
• DNA vaccines and replicons
• Combination vaccines or prime and boost

15
Types of vaccine

• Live attenuated vaccines
• Inactivated or 'killed' vaccines
• Second classic technique (e.g. Dr Jonas Salk in
  creating the world's first successful polio
  vaccine)
• No-one has yet claimed any significant success
• Maybe difficult to distinguish between vaccine
  immune response and infection
• Recombinant sub-unit envelope vaccines
• Recombinant vectored vaccines
• DNA vaccines and replicons
• Combination vaccines or prime and boost

16
Types of vaccine

• Live attenuated vaccines
• Inactivated or 'killed' vaccines
• Recombinant sub-unit envelope vaccines
• Seek to stimulate antibodies to HIV by mimicking
  proteins on the surface of HIV (e.g. gp120)
• Initial research was strain-specific and produced
  poor antibody responses
• Recently more hope
• Recombinant vectored vaccines
• DNA vaccines and replicons
• Combination vaccines or prime and boost

17
Types of vaccine

• Live attenuated vaccines
• Inactivated or 'killed' vaccines
• Recombinant sub-unit envelope vaccines
• Recombinant vectored vaccines
• incorporate harmless bits of HIV into established
  vaccines
• ALVAC series of vaccines are canarypox based
  vaccines
• Vaccine strains of adenovirus
• recombinant rabies virus vaccines
• DNA vaccines and replicons
• Combination vaccines or prime and boost

18
Types of vaccine

• Live attenuated vaccines
• Inactivated or 'killed' vaccines
• Recombinant sub-unit envelope vaccines
• Recombinant vectored vaccines
• DNA vaccines and replicons
• involve HIV genetic sequences which, once
  injected, induce expression of HIV antigens by
  human cells.
• In the case of replicons, these sequences are
  wrapped in the outer coat of an unrelated virus.
• Combination vaccines or prime and boost