Microbiology Unit 5

  1. HIV Viral Structure
    • it is a RNA virus enveloped with spikes because it dies quickly outside the host
    • retrovirus uses reverse transcriptase to synthesize DNA from RNA, makes a second strand of DNA and inserts it's DNA into the host DNA becoming a provirus
  2. AIDS
    • acquired immune deficiency disorder syndrome
    • destroys the immune system response by invading and destroys the Helper T cells and other CD4 cells (monocytes, macrophages and CNS cells also have CD4 receptor sites)
  3. CD4
    • it is the receptor site for macrophages, monocytes, and CNS cells
    • HIV targets these receptor sites
    • CD4 help Helper T cells to recognize foreign antigens in the body (such as viruses, bacteria, fungus, cancer)
    • Helper T cells are sentisized and signal B cells to start producing antibodies to the foreign antigen -- they also activate the T cells
    • when Helper T cells are destroyed, they can no longer stimulate B cells to produce antibodies and cannot activate T cell system
    • HIV infects CD4 cells goes into a dormant stage for an indefinite period of time
    • when the virus starts replicating within the CD4 cells, cells burst and virions go on to infect new CD4 cells, this continues until it kills all CD4 cells in the blood, lymph nodes, spleen, and other lymph glands until the immune system is gone
  5. HIV Stages
    • 4 stages
    • Stage 1 Acute Infection
    • Stage 2 Asymptomatic Disease
    • Stage 3 Persistent Generalized Lymphadenopathy (PGL)
    • Stage 4 Sympotmatic Aids Infection
  6. HIV Stage 1 Acute Infection (Viremia)
    • Duration is few weeks to 6 months
    • CD4 count is > 1000/ml which is normal --- HIV test would be normal
    • the virus is high in concentration in the bloodstream, but many patients are asymptomatic
    • very contagious
    • sx: rash, fever, diarrhea, lymphadenopathy, night sweats, fatigue
    • Spreads widely through the body mostly in lymph nodes and lympatic tissues
  7. HIV Stage 2 Asymptomatic Disease
    • Duration is 8-10 years on average without medication, this is due to the provirus replicating
    • CD4 count is > 1000/ml which is normal --- HIV test would be normal
    • may be asymptomatic or have some symptoms
    • considered HIV positive if there is an antibody performed -- called HIV Infection
    • virus is slowly replicating in the lymph nodes and lymphoid tissue, low viral numbers in the blood
  8. HIV Stage 3 Persistent Generalized Lymphadenopathy
    • lymphadenopathy longer than 6 months in 2 or more areas of the body along with an HIV positive status due to active replication of the virus
    • CD4 count is < 600/ml
    • most patients will go to stage 4
  9. Stage 4 Advanced AIDS or Symptomatic AIDS Infection
    • CD4 count is < 200/ml (death is imminent when CD4 < 50/ml)
    • there is a decline in T cells which allows the disease to occur actively
    • ARC - AIDS related Complex includes drop in 10% of weight, severe diarrhea, AIDS wasting
    • opportunistic infections occur
    • HIV encephalopthy can occur, similar to Alzheimer's Disease
    • Secondary infections
    • Secondary cancers
  10. Common opportunistic infections
    • 80-90% have neurologic diseases
    • PCP Pneumonia (Pneumocystis carinii) is a fungal pneumonia that affects > 80% of AIDS patients
    • CMV retinitis is seen in 75% of AIDS patients which can cause blindness
    • Kaposi's Sarcoma is seen in 25% of AIDS
    • Invasive cervical cancer is a recent opportunist infection in AIDS
  11. HIV in infants
    • HIV can be passed on to babies in 3 ways: in utero, during delivery, in breast milk
    • the rate of infection without intervention is 25%
    • with intervention, it is 2% when "bloodless C-section" and giving ZDV to infant
  12. Healthcare workers
    • use PPE to prevent infection
    • extremely low incidence in healthcare workers
    • far more likely to get Hepatitis B than HIV through direct exposure
  13. HIV Treatment
    • no cure, although control has greatly improved
    • AZT for adults
    • ZDV for infants
    • Interferon
    • Protease inhibitors - cocktails
    • Reverse transcriptase inhibitors
    • Fusion inhibitors
    • antibiotics used for bacterial infection
  14. Tests to monitor the progress of AIDS
    • CD4 cell counts
    • normal is > 1000/ml
    • as CD4 count decreases, disease progression increases
  15. Viral RNA Copies
    • more viral RNA means more viral load
    • as it goes up, it indicates AIDS progression
  16. HIV Means of Transmission
    • to enter the body, the virus must make contact with a break in the skin or with a mucus membrane
    • have intimate contact with body fluids of an infected person
    • most commonly through blood, semen, and vaginal secretions
    • sharing dirty needles by IV drug abusers when one has AIDS will transmit the disease
    • Receiving a blood transfusion with contaminated blood
  17. Diagnosis of HIV
    • ELISA method - screening test for AIDS; detects antibodies
    • has .47% false positive
    • If positive, a second test called the Western Blot is done to confirm HIV positive
    • no false negative results
  18. Western Blot Test
    • detects the HIV/AIDS virus
    • confirms the test
    • if positive, patient has AIDS
    • if negative, patient does not have AIDS
Card Set
Microbiology Unit 5