Aids

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 • • • • • • • • •

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 •

Globally: – – – –

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