AIDS supplement
S.1 Origin and prevalence of HIV
History of HIV
• Originated in Africa in the late 1950’s
• Originally found in nonhuman primates and may
have mutated
• First documented in the US in 1969
• HIV was found to be the cause of AIDS in 19831984
S.1 Origin and prevalence of HIV
Prevalence of HIV
• Pandemic proportions
• ~ 38.6 million people are living with HIV
• At least 1% of adults has HIV
• Most people living with HIV live in developing
countries with the highest in India and South
Africa
S.1 Origin and prevalence of HIV
Prevalence of HIV
S.1 Origin and prevalence of HIV
Prevalence of HIV
S.2 Phases of HIV infection
Phases of HIV infection
• Category A:
– Asymptomatic but highly infectious
– CD4 count above 500 cells/mm3
• Category B:
– One or more related to an impaired immune system
– CD4 count between 200-499 cells/mm3
• Category C:
– At this point the person has AIDS in which they have one or
more of the AIDS opportunistic infections that eventually is the
cause of death
– CD4 count has fallen below 200 cells/mm3
S.2 Phases of HIV infection
Phases of HIV infection
S.3 HIV structure and life cycle
Structure of HIV
• Two single strands of
RNA
• Enveloped with
spikes (Gp120)
• Carries 3 enzymes
– Reverse transcriptase
– Integrase
– Protease
S.3 HIV structure and life cycle
HIV life cycle/replication
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Attachment: Gp120 binds to CD4 receptors
Fusion: HIV fuses with the cell membrane
Entry: uncoating occurs to release the RNA
Reverse transcriptase: RNA is transcribed into
double-stranded DNA
Integration: new DNA becomes part of the host cell’s
DNA in the nucleus (provirus)
Biosynthesis: produces more viral RNA and proteins
Assembly: assemble new parts into viral particles
Budding: viral particles bud from the cell membrane
taking a piece with it that becomes the envelope
Transmission to a new host: passed to a new host
S.3 HIV structure and life cycle
HIV life cycle
S.3 HIV structure and life cycle
Transmission and prevention of HIV
• Transmission is through sexual contact, dirty
needles, a blood transfusion or to a baby from their
mother
• Globally heterosexual sex is the most common mode
of transmission
• HIV is not passed through casual contact
• Prevention is through abstinence, sex with only one
uninfected partner and proper, consistent use of
condoms
S.3 HIV structure and life cycle
HIV testing and treatment
• HIV tests test for the presence of antibodies not the
virus itself
• Most people develop antibodies within 2-8 weeks of
infection but it can take 3-6 months (consider this
when being tested!)
• Treatments:
– Drug therapy: highly active antiretroviral therapy (HAART)
used a combination of drugs to inhibit HIV replication
– Vaccines: as of 2006, 27 vaccines are being tested in
humans but results are not expected until 2010 but these will
not be a cure
S.3 HIV structure and life cycle
Science Focus: HIV vaccines
• Difficulties in producing a vaccine
development:
– HIV viruses locally and globally are genetically
different
– No vaccine so far is 100% effective and may only
provide short-term protection
– Concerns that the vaccine may increase the
chances of getting the disease or even cause the
disease
– There is no ideal animal model for testing besides
humans themselves
S.3 HIV structure and life cycle
Bioethical Focus: AIDS
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Globally:
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95% of people living with HIV live in developing countries
80% of deaths are people ages 20-50
50% of new HIV infections are in people ages 15-24
Estimated that by the end of 2005, 65 million people have been infected yet
only 1 in 10 are aware of the infection
– 12 million orphans have been left behind
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In the US:
– 3% of people living with HIV live in the US
– For men:
• Male-male sexual contact is the main mode of transmission in the US (65%) while
heterosexual contact accounts for ~16%
– For women:
• Heterosexual contact accounts for 78% of HIV transmission
– African Americans are the hardest hit ethnic group
– About 1 million people living with HIV today and 25% do not know it