LECTURE 10 (AIDS) Flashcards
What are the properties of HIV?
- A retrovirus
What is a Retrovirus?
A virus that uses RNA as its genetic material instead of DNA and infects cells by copying their RNA into the DNA of the cell
What was known before HIV was discovered?
Two human retroviruses causing two types of leukaemia
What can happen to the infected DNA of a cell?
- Sit silently in the cell being copied normally along with the cell’s genetic material for an indefinite number of generations
- Take over control of the cell’s machinery causing uncontrolled reproduction typical of cancer
Describe how HIV targets CD4-T lymphocyte/T4 cell affects the cell
T4 cell’s role is to divide and reproduce itself in response to such an invasion and to attack the invader -> T4 cell infected with HIV -> activation of the cell activates the virus as well which produces thousands of copies of itself in a process that kills the T4 cell -> destruction of T4 cells disrupts the entire immune system
What are the functions of T4 cells?
- Attack foreign microbes
- Regulate other components of the immune system (e.g Plasma cells)
- Regulate proteins in blood that recognise foreign substances
Describe the phases of HIV
1) Mild, flu-like symptoms for a few weeks during which the virus is present in blood + body fluids and is easily transmitted to others -> body’s immune system produces specific antibodies
2) Latent period with the virus hidden in DNA of T4 cells -> person is quite healthy + less likely to transmit the virus -> but so many of T4 cells begin to die that they cannot be replaced rapidly enough
3) T4 cells drop below 20% of normal level, symptoms appear + person is vulnerable to opportunistic infections and certain tumours + more capable of transmission -> AIDS
The course of infection with HIV takes place over a number of years (TRUE/FALSE)
TRUE
What are Opportunistic infections?
An infection caused by an organism (pathogen) that does not normally cause disease
Explanation: Occur in people with weakened immune systems since cause only mild illness in healthy individuals but serious consequences in immunocompromised hosts
What is HIV?
A virus that attacks the immune system, specifically targeting CD4 cells crucial for the body’s defense against infections and diseases. HIV replicates and gradually weakens the immune system over time.
What is AIDS?
The final stage of HIV infection; a collection of symptoms and illnesses that occur when the immune system is severely damages by the HIV virus
Not everyone who has HIV progresses to AIDS (TRUE/FALSE)
TRUE
Explanation: With proper medical care and Antiretroviral treatment, people with HIV can live long and healthy lives without developing AIDS
What are the properties of the HIV screening test?
- Measures antibodies to the virus which begin to appear 3-6 weeks after the original infection
- Fast and inexpensive
- Sensitive enough to give first indication of virus
- Absence of antibodies in blood during the initial 3-6 week period after infection -> “window” of non-detectability may give newly infected people a false sense of security
What is the purpose of the HIV screening test?
- Diagnosing individuals at risk to determine whether they are infected so they can be counselled/treated
- Monitoring the spread of HIV in various populations via epidemiological studies
- Screening donated blood or organs to ensure they do not transmit HIV to a recipient of a transfusion or transplant
How does a therapy effective in reducing viral load help control the spread of HIV?
Measurement of “viral load” (concentration of virus in the blood) evaluates the effectiveness of therapeutic drugs -> Can influence an individual’s chances of transmitting the virus by sexual and other means -> Therapy reducing viral load can help control the spread of HIV
What are the modes of Transmission of HIV?
- Homosexual relations between men + Heterosexual relations
- Sharing of needles
- Transfusion with HIV-contaminated blood
What has been shown to protect men against contracting HIV from infected women?
Circumcision
Explanation: However, circumcision does not appear to protect women against contracting HIV from infected men
What is a special case of HIV transmission?
HIV transmission from an infected mother to her infant in utero or during delivery or through breastmilk -> transmission can be prevented if the mother take antiretroviral drugs
What are the factors that lead to HIV being the “disease of minorities”
- People tend to have sex with partners of the same race and ethnicity
- Minorities’ tendency to experience higher rates of other STDs which increase rick of transmission of HIV
- Socioeconomic issues associated with poverty
- Lack of awareness of HIV status
- Negative perceptions about HIV testing
What are the properties of Zidovudine (AZT)?
- First antiretroviral therapy
- Approved by FDA in 1987
- MOA: drug interfered with the replication of HIV by inhibiting the enzyme that copies the viral RNA into the cell’s DNA
- Effectiveness can wear off since the virus mutates rapidly
What are the different ways of treating HIV/AIDS?
- Protease inhibitors = interfere with the ability of newly formed viruses to mature and become infectious
- Highly active antiretroviral therapy (HAART) = combinations of drugs that attack the virus in different ways -> reduces the opportunity for HIV to mutate and develop resistance
What are the advantages of HAART (Highly active antiretroviral therapy)?
- Can reduce viral load to undetectable levels in the blood and bodily fluids -> greatly reduces the likelihood that the virus will be transmitted to others
- Encourages at-risk people to be tested and counseled
What are the disadvantages of HAART (Highly active antiretroviral therapy)?
- Virus manages to survive in protected reservoirs of the body -> rebounding into active replication when drugs are withdrawn
- Protease inhibitors can develop LIPODYSTROPHY (abnormal distributions of fat in the body) accompanied by other metabolic abnormalities
- Virus can develop resistance to these drugs if used improperly
What is the difficulty in developing an effective vaccine for HIV/AIDS?
- Virus constantly changes its appearance
- Lack of a good animal model for studying HIV/AIDS
What is the most effective way to fight AIDS?
To prevent transmission
Explanation: Requires education and efforts at motivating people to change their high-risk behaviour
Where did the virus come from?
It commonly infected African monkeys and apes and a mutation allowed one of these viruses to infect humans (cross-species transmission of viruses)
Where did HIV/AIDS start and who was the “first patient”?
The human form of the virus may have existed in isolated pockets of Africa for some time but was widely spread in late 1970s
The earliest case was Robert Rayford who died in 1969 at the age of 16 -> exhibited many symptoms of AIDS including KAPOSI’S SARCOMA (numerous internal lesions)
What is Kaposi’s Sarcoma?
A type of cancer that forms in the lining of blood and lymph vessels appearing as painless purplish spots on the legs, feet, face and even the digestive tract and lungs
CAUSE:
Infection with a virus called HUMAN HERPESVIRUS 8 (HHV-8) -> In healthy people it causes no symptoms because the immune system keeps it under control -> Immune system allows HHV-8 to multiply
RISK FACTORS:
- Organ recipients taking immune-suppressing drugs
- Older men of Eastern European, Mediterranean and Middle Eastern descent
- All ages in equatorial Africa
What caused the worldwide explosion of AIDS?
- Changing patterns of sexual behaviour
- Use of addictive drugs in developed and developing countries
- Ease of International air travel
