Chapter 1 Origin Of HIV And AIDS Flashcards
What does AIDS stand for and define it
AIDS stands for acquired immunodeficiency syndrome.
It is caused by a virus HIV ( human immunodeficiency virus) which enters the body and destroy ability to fight off infection.
What is an HIV antibody test
It’s a test to determine if a person has antibodies to HIV which indicates that the person has been exposed the most common test being ELISA test.
Who first discovered the HIV and AIDS
Dr.Luc Montagnier
Dr.Robert Gallo
Define vaccine
It is a substance given to stimulate immune system to protect person from infection by a specific micro organism.
What is the difference between HIV Incidence and HIV prevalence
HIV Incidence is the number of new cases of infection as a percentage.
HIV Incidence=n.o of new infection in specific year /n.o of previously uninfected people.
HIV Prevalence is the number of people living with HIV at a specific time
HIV prevalence= n.o of people infected / total population
What is a virus
A virus is a unicellular organism that can’t reproduce or replicate outside a host and only inside a host can they replicate. They produce more viruses by inserting own genetic code into the genetic code of host cells in a process called integration of genetic material.
Viruses are called intracellular parasites because they need to use the biochemical facilities of living cells to multiply.
Retrovirus is a type of virus that replicates by changing its genetic RNA into DNA by using hosts cells.
What is an immune system
It is the body’s response to pathogens
It has 3 lines of defense against invaders
1. Physical barriers like organs like the skin, sweat and gastric juices.
2.The innate immune system which is made up of cells that attack and engulf other living organisms this is seen when one experience inflammation for eg.(phagocytes)
Plasma proteins used to identify invaders and assist antibodies.
White blood cells used to devour these identified invaders.
3.called the adaptive or acquired immune system that is specialized by acquiring specific skills that makes it very effective in reacting to or killing specific pathogens.
What are the 4 phases of the specific immune system
- Recognition and warning
Distinguishing between friend and enemy identified through antigens which are any foreign substance which when introduced into the body causes an immune response like production of antibodies that react specifically with these antigens which are mainly composed of proteins present on the surface of viruses or bacteria.
Memory T cells and B cells that store the antibody for previous pathogens making the response instantaneous.
Some cells of innate immune system act as antigen presenting cells APCs which grab part of an antigen (epitope) from invader and show it on own surface.dendritic cells are the most NB APCs.
- mobilisation and battle
Lymphocytes like T or B lymphocytes involved in killing pathogens by being pre programmed to recognise pathogens. When activated they bind with infected cell which carry antigen on surface and then releases cytotoxins which kills the infected cell.
B lymphocytes located in lymph nodes and provide the immune system with ammunition to fight invaders. They can recognise whole pathogens without the need of pathogens to be processed before antigen can be recognized. Once stimulated B cell produce plasma B cells that mass produce antibodies against antigen.
- Demobilisation
Suppressor T cells order the CD4+T cells to stop mobilising and CD8+T cells stop attacking and release substance to stop B cells from making antibodies. - Active immunity and passive immunity.
Active long term memory: immune system through T and B cells remember specific invader or antigen and if body attacked by same pathogens again immune system quickly and efficiently react against it without becoming sick.
Long term immunity cab develop as cell mediated and humoral immune response. T cells involved in cell mediated immune response where T cells only formed after pathogens already infected some cells. B cells part of humoral immune response where antibodies are produced by immune system to recognise and neutralise pathogens before it can infect cells.
Immunization or vaccination is a substance that stimulates an infection by a specifc pathogens by introducing a protein component or antigen of the organism to immune system which stimulates it to produce memory B and T cells.
Passive short term memory : is the short term immunity that a newborn baby gets from it’s mother. Special antibody called IgG is transported across placenta. Colostrum also has antibodies transferred from mother to baby gut to protect against pathogens.
Define immune deficiency
A weakening or failing in the immune system to operate in supporting the body’s recovery.
Critically discuss HIV
Is a retrovirus and it’s circular in shape. Core of nucleas is cone shaped with single stranded RNA and several proteins called enzymes.
Viral enzymes include reverse transcriptase enzyme the protease enzyme and integrase enzyme which aid the copying of the virus inside host cell and injected with viral genetic material into host during infection.
2 most important proteins found in the inner core membrane are knob like proteins called gp120 and a smaller spike like protein called gp41 which play critical role in initial steps of infection which is attachment and penetrations into host cell.
Opportunistic infections: infection that wouldn’t normally cause disease in a healthy body but which exploits opportunity presented by inflected person weakened immune system to attack body.
Explain HIV infection and replication
HIV can enter through lesions in skin and transferred through intact mucus membrane in vagina due to dendritic cells called Langerhans cell.
Steps of infection
1. Attachment: gp120 makes contact with host cell CD4+Tcell and then attaches itself to CD4 receptors present on the surface of host cell. The gp 120 attaches to a co receptor on cell surface to bring gp140 protein of HIV into contact with cell membrane.
Co receptor include CCR5 for macrophages and CXCR4 for lymphocytes.
- Fusion: gp120 protein splits open and exposes gp41 causing fusion to take place between outer envelope of virus and outside membrane of host CD4+Tcells.
- Injection: virus sheds outer layer and injects genetic material and enzymes into CD4+T cells.
- Reverse transcription: HIV viral RNA must be changed to proviral DNA through reverse transcription where single stranded RNA is changed to double stranded DNA with the enzyme reverse transcriptase.
- Integration of genetic material: proviral DNA is transported to nucleus where it fuses with host cell DNA facilitated by enzyme integrase.
- Replication of genetic material: viral genetic material hijacked genome of host cell and employs machinery of host cell to replicate genetic material necessary for new viruses to be made.
- Production of new viruses: viral enzyme protease enable newly made RNA and viral proteins to be assembled into new copies of former virus release from the cell as functional HI viruses that kills original host cell and these new viruses travel into blood stream and infect additional cells where the whole process is repeated.
The results are that it produces more viruses and depletes n.o of CD4 T cells than the thymus gland can replace which impairs the whole immune system.
What causes HIV to change rapidly
The introduction of mutations into viral genome during reproduction
The variability of HIV is due to inaccuracy of its genetic copying mechanism and tendency to make errors.
Recombination between viral genomes that shuffle these mutations.
Recombinant viruses are generated when 2 viruses enter the same cell.
Define antigen
Any foreign substance which when introduced into the body elicits an immune response such as the production of antibodies that react specifically with these antigens which are composed of proteins and usually appear on surface of bacteria.
What are urban legends
Are ideas regarding the origin of HIV that consist of unsubstantiated conspiracy theories or stories that blame a person, organisation or government agency for making or spreading the virus.
Give the origin of HIV
Current scientific theory is that HIV has crossed many species barriers on several occasions from various primate species resulting in different groups of hi virus.
