BIO SCI 45 Lecture Notes - Lecture 5: Lymph Node, Western Blot, Dendritic Cell

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byzantiummacaw133

14 Sep 2016

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Macrophages: produce virus, are not killed, can establish latent hiv infection, important for persistence of infection. Hiv must bind to cd4 to infect. Cd4 binding alone -> no entry of hiv virus particle. Additional co-receptor on cell surface for virus entry: co-receptors normally bind cell growth factors, cxcr4: co-receptor on t-helper cells, ccr5: hiv co-receptor on macrophages, different hivs prefer ccr5 or cxcr4, gp120 determines co-receptor preference. After infection, there is often acute infection syndrome: flu-like illness, swollen glands, goes away after a few weeks. Most free of any symptoms (asymptomatic) for a time: typically many years, produce antibodies to hiv. Not sufficient to prevent continued hiv infection. Symptoms of hiv infection: persistent enlarged lymph glands (lymphadenopathy syndrome, fevers or night sweats, progressively more serious as the immune system weakens. Progression from asymptomatic to aids: progressive depletion of t-helper lymphocytes, failure of humoral and cell-mediated immunity. Normal immune system: t-helper counts typically: > i,000/cubic millimeter of blood.

Related Questions

Question 1 10 pts

What three kinds of cells are infected by HIV?

macrophages, T-Helper cells and dendritic cells

B-cells, skin cells and T-helper cells

B-cells, T-Helper cells and T-killer cells

macrophages, dendritic cells and cytotoxic T-cells

Question 2 10 pts

Sometimes an HIV infected cell is not killed immediately after infection, but lives on, and continues to be a source of the infection for the lifetime of the patient. What is the mechanism that allows the HIV virus to remain in the cell, to get passed down to all descendants of that cell, and to retain the ability to be reactivated for the lifetime of the patient?

Question 3 10 pts

List the three processes that viruses are dependent on their host cells for.

Question 4 10 pts

What does the ELISA test for HIV infection measure?

HIV-specific antibodies

Hepatitis B-specific antibodies

circulating HIV particles

HIV-specific DNA

Question 5 10 pts

What is the cell surface receptor for HIV?

CD4

CD8

MHCII

HIV

Question 6 10 pts

What is the likely origin of HIV-1?

infection of humans by a simian virus native to the chimpanzee

germ warfare research by the CIA

sexually transmitted to humans through relations with sheep

a new human-chimpanzee hybrid virus accidentally made in a laboratory with recombinant DNA

Question 7 10 pts

How does AZT block the production of infectious virus?

It acts as a substitute for a DNA nucleotide that can only be inserted by the viral reverse transcriptase. The presence of the AZT in the DNA aborts the production of new viral DNA.

It directly blocks the reverse transcriptase.

It blocks the protease that cuts apart the three viral proteins, which is a necessary step during viral synthesis.

It blocks the adsorption of the virus to the CXCR4 and CCR5 receptors on the T-cell surface.

Question 8 10 pts

How do protease inhibitors work?

It blocks the protease that cuts apart the three viral proteins, which is a necessary step during viral synthesis.

It directly blocks the reverse transcriptase.

It acts as a substitute for a DNA nucleotide that can only be inserted by the viral reverse transcriptase. The presence of the AZT in the DNA aborts the production of new viral DNA.

It blocks the adsorption of the virus to the CXCR4 and CCR5 receptors on the T-cell surface.

Question 9 10 pts

What are the 2 most common causes of a false negative result in the HIV test?

Questions 10-13

The next set of 4 questions deal with the possible ways that a virus, not necessarily the HIV, can enter the body. Answer TRUE or FALSE to each question.

Question 10 2.5 pts

Some viruses can enter the body through breaks in the skin.

True

False

Question 11 2.5 pts

Some viruses can enter the body through the anal/genital tract.

True

False

Question 12 2.5 pts

Some viruses can enter the body through the oral cavity and the digestive tract.

True

False

Question 13 2.5 pts

Some viruses can enter the body through inhalation via the respiratory tract.

True

False

Below is a paragraph describing HIV infection as they relate to the progress of infection. Please help choose the correct answer in each parentheses.

HIV initially infects (CD4+, or CD8+, or B) cells. These are helper T cells that activate (CD4+ or ,CD8+ or, B) cytotoxic T cells and (CD4+, or CD8+, or B) cells which produce antibodies. If HIV kills (CD4+, or CD8+) T cells then they cannot to do their job of activating these cells thus causing HIV infected people to be immunocompromised. Sometimes HIV infected people enter a latency period where the virus is inactive. This latency period can last for several years. During latency HIV (DNA, or RNA) becomes integrated into the (CD4+ or CD8+, or B) host cells genome and stops producing viral HIV RNA and new HIV virions. However, for some unknown reason, HIV comes out of dormancy and the viral (RNA, or DNA ) that was integrated in the (CD4+ , or CD8+,) T cell genome begins to transcribe more viral (DNA , or RNA) to make more viral (DNA, or RNA) using the host cells machinery. The viral (DNA, or RNA) then gets translated by host cell ribosomes to make viral proteins that eventually become packaged into new HIV virions. Consequently, after the latency period HIV becomes activated in the host cell. These cells present HIV antigen on their cell surface and alert (CD8+ or CD4+ or B) cells to kill them. As they are killed the infected (CD4+, or CD8+, or B) cells release the HIV virions into the blood stream to infect other (CD4+ or CD8+) cells such as macrophages and dendritic cells. This explains why after latency we see (CD4+, or CD8+) T cells continue to decrease while at the same time viral (DNA, or RNA) levels increase.

Based on your answers to the fill in paragraph, which statement is true?

A. Once active in CD8+ T cells, HIV can now replicate with impunity and infect other cells which explains the increase in HIV RNA after latency.

B. The increase in active HIV after latency accounts for why HIV can remain dormant for years after the initial infection.

C. CD4+ levels stabilize after the latency period and explain why there is little increase in HIV RNA levels.

D. Opportunist infections can occur after HIV latency because there are very few helper T cells to left to activate cytotoxic T cells and B cells to mount an immune response.

1. A mutation in the gene encoding the integrase enzyme rendersthe protein non-functional. How would the affect the HIV infectioncycle?

Formation of the provirus would be stopped.
Reverse transcription would no longer be possible.
The gp120 glycoprotein would no longer be able to bind to the CCR5receptor.
Cutting and assembling the capsid would be halted.

2. If the viral gene is AUGCCCAGG and the mRNA used to make theviral protein is UACGGGUCC, then the virus is a :

Negative strand RNA virus
Double stranded DNA virus
Retrovirus
Positive strand RNA virus

3. Would treating prions with enzymes that digest nucleotides bean effective neutralization method?

No, prions lack amino acids.
Yes, prion nucleic acids would be susceptible to enzymaticdigestion.
No, prions lack phosphodiester bonds and would not be subject todigestion by these types of enzymes.
Yes, the bonds between the amino acids would be hydrolyzed.

4. Most Americans born before 1970 have a permanent scar ontheir shoulders from the smallpox vaccine. Why don't youngerAmericans have one?

Smallpox has been eradicated by a worldwide vaccinationprogram.
Smallpox is no longer lethal.
A safer less damaging vaccine was developed in the early1970's.
The vaccine is no longer effective due to antigenic shift.

5. What kind of pathogen would retain its ability to causeinfections after being treated with powerful proteolytic chemicalsthat would destroy all proteinaceous material?

A virus
A bacterium
A prion
A fungus
A viroid

6. Select all of the false statements concerning AIDS.

AIDS kills the patient.
Patients die as a result of opportunisticinfections.
AIDS shuts down the immune system.
HIV therapy (HAART) can clear the virus from thebloodstream.

HIV therapy (HAART) can clear the virus from the patient'sbody.

7. Why do viruses only infect specific types of cells?

Viruses only attack epithelial cells, such as the cells liningthe lungs.
If a host cell is weakened, viruses have an easier time infectingit.
The initial choice is random but once a cell type is chosen itbecomes the preferred host.
The host cells have the correct surface receptor that the virus canfit into.
Viruses infect the first cells they encounter.

8. Nucleotide analogs are a class of drugs that are highlyeffective against many types of viruses. They work by halting thereplication of viral genes. They are equally effective at stoppingthe spread of prion diseases.

True
False

9. An experimental chemical has been shown to selectively cleavephosphodiester bonds. How would the affect a virus?

Dissociate the envelope
Fragment the genome
Hydrolyze the protein coating
Alter the host binding site
Digest the capsid

10. HIV uses cell surface receptors to enter host cells. Whydoes switching from a CCR5 co-receptor to a CXCR4 co-receptoreventually shut down the immune system?

Macrophages have CCR5 co-receptors.
T-helper cells have CXCR4 co-receptors.
T-helper cells are not involved in coordinating immuneresponses.
Only macrophages are killed by HIV.

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BIO SCI 45 Lecture Notes - Lecture 5: Lymph Node, Western Blot, Dendritic Cell

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