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Emerging Diseases

Emerging Diseases. BIOL 119 Spring, 2011 Retroviruses and HIV. AIDS is Caused by a Retrovirus. RNA virus that works in reverse. Viral RNA is copied over into DNA Reverses the usual direction of copying. Retrovirus “life cycle”. Reverse Transcription and integration are two key steps.

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Emerging Diseases

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  1. Emerging Diseases BIOL 119 Spring, 2011 Retroviruses and HIV

  2. AIDS is Caused by a Retrovirus RNA virus that works in reverse Viral RNA is copied over into DNA Reverses the usual direction of copying

  3. Retrovirus “life cycle” Reverse Transcription and integration are two key steps. These two steps produce a form of the virus called the provirus.

  4. Provirus • Behaves exactly like a regular gene. • When active, produces more viral particles. • Can cause mutations that lead to cancer. • Can be passed on to subsequent generations through sperm and egg DNA. • Endogenous retroviruses are the ones that you inherit from your parents. • Most retroviruses are benign and do not cause disease.

  5. Human Retroviruses Timeline YearVirusEvent  1980          HTLV-I              first human retrovirus-Gallo lab at NIH  1981                                    first CDC report on AIDS (MMWR report)  1982          HTLV-II             second human retrovirus  1983          LAV                   from pre-symptomatic patient, virus later named HIV-1-from Pasteur Institute in Paris  1984          HTLV-III            Gallo lab contaminant  1984          ARV                  from San Francisco patient  1985          STLV-III            a primate retrovirus from macaques  1986          HIV-2                West African strain HIV-1 and HIV-2 are classified as lentiviruses (a type of retrovirus) because it takes so long for their symptoms to appear. HIV-2 is “weaker” than HIV-1 and is mainly confined to West Africa. Both are transmitted via body fluids; blood-borne or sexual.

  6. Targets of HIV-1 Receptor = molecule that virus attaches to CD4 Protein = primary receptor for HIV-1 CD4+ cells= cells that have the CD4 protein on their surface T cells, nervous system cells, other immune system cells. Opportunistic pathogens kill when immune system declines. CCR5 is another important receptor; CCR5/delta32 mutation is a resistant form HIV infection gradually wipes out the immune system and allows opportunistic pathogens to flourish.

  7. Antiviral Therapy • Virus mutates rapidly to become resistant to standard antiviral medications because reverse transcription is error-prone. • No one anti-retroviral (ARV) drug can hold the virus in check for long. • Combination therapy-the use of several classes of drugs at once-works better. • HAART-Highly Aggressive Anti-Retroviral Therapy

  8. Origins of HIV • HIV is very closely related to a virus found in other primates: SIV • The chimpanzee version of SIV (SIVcpz) is closest of all to HIV-1 • How did SIVcpz “jump” into humans? • Two main groups of hypotheses Zoonotic origin-came from wild animal contact Iatrogenic origin-introduced by western medical procedures in colonial Africa

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