HIV virology Flashcards
When was HIV first reported in the UK?
December 1981 - 2 cases
What were the first reported cases of HIV in the UK?
49 year old homosexual male with PCP and CMV infection
29 year old homosexual male with Kaposi’s sarcoma, CMV and cryptococcal pneuomnia
What are the names of the two distinct HIV viruses?
Human immunodeficiency virus 1 and 2
Where did HIV 1 originate from?
Related to viruses called Simian immunodeficiency virus (SIV) found in chimpanzees and gorillas in West Africa
Where did HIV 2 originate from?
Closely related to SIV found in the Sooty Mangabey
When were the HIV viruses thought to cross species?
Crossed from primates to humans in Africa in the late 19th century or early 20th century.
How did the virus jump species?
Bush meat theory - a hunter was bitten or cut while butchering an animal
- it isn’t known how SIV transformed into HIV and became capable of replicating in humans
Which factors triggered and epidemic of transmission?
Social changes
Urbanisation
Unsterile injections - vaccines, antibiotics, sleeping sickness
Genital ulcer diseases and sexual promiscuity
What was the first confirmed case of HIV in Africa?
1959 Congolese man
- HIV-1 infection detected in blood sample from a man in Kinshasa
- unknown whether he developed AIDS or not
How did HIV spread from Africa?
Spread to Haiti by an unknown person who contracted it in the Democratic Republic of the Congo A miniepidemic (1969) followed and HIV came from Haiti to the USA - that single person caused most AIDS cases outside of Sub-Saharan Africa.
Why does HIV spread most quickly though the male gay community?
Combination of sexual promiscuity and high transmission rates associated with anal intercourse
When was the first reported case of AIDS?
1981 - when prevalence of HIV infections in some communities was around 5%
What are the most at risk groups for developing an HIV infection?
Men who have sex with men Black African Women Black African Men Other women Other men IVDU
How is HIV transmitted?
HIV enters the body through open cuts, sores or breaks in the skin, through mucous membranes such as those inside the anus or vagina, or through direct injection.
What activities allow HIV transmission?
Anal or vaginal intercourse (not oral) Injecting drugs and sharing equipment Mother to child Transmission in health care settings Via donated blood or blood clotting factors
Which cells does HIV affect?
HIV cells infect cells in the immune system such as T-helper cells, macrophages and dendritic cells - as all of these cells carry CD4 receptors which allow HIV entry
How does an HIV infection cause depletion of CD4 T helper cells?
Direct viral killing of cell
Apoptosis of uninfected bystander cells
CD8+ cytotoxic T cell killing of infected CD4+ cells
Abnormal B cell activation resulting in excess/inappropriate immunoglobulin production
When is a person at most at risk when they have an HIV infection?
Once CD4+ cells fall below a critical level (less than 200) the person is a risk of opportunistic infections and some cancers.
What is the genetic contents of a HIV virus?
Two copies of single stranded RNA enclosed by a conical capsid composed of 2000 copies of the viral protein p24
The RNA is tighly bound to nucleocapsid proteins and the enzymes needed for the development of the virion.
A matrix composed of the viralprotein p17 surrouds the capsid ensuring integrity
What are the enzymes with the conical capsid containing the viral RNA?
Reverse transcriptase
Proteases
Ribonucleases
Inegrase
Describe the viral envelope for the HIV virus?
Two layers of phospholipids taken from the membrane of the human cell when a newly formed virus buds from the cell.
Embedded in the envelope are proteins from the host cell and about 70 copies of a complex HIV protein that protrudes through the surface of the virus
Describe the HIV protein that is embedded in the viral envelope and protrudes through the surface of the virus?
Env
- this consists of a cap made of three molecules (glycoprotein 120)
- a stem consisting of three gp41 molecules that anchor the structure into the viral envelope
What is the function of the Env protein?
The glycoprotein complex enables the virus to attach to and fuse with target cells
- often targeted in treatment
Where are the possible targets in an HIV lifecycle?
Fusion - when the virus fuses to the cell and dumps its contents
Conversion of viral RNA to DNA - so the virus can insert its genetic code into the host cell
Integration - where the viral DNA is inserted into the host DNA
Budding - when the vius buds off from the host cell and goes to infect another
