BIOC31H3 Lecture Notes - Azide, Reverse Transcriptase, Mutation Rate

52 views2 pages

amethystreindeer873

19 Jan 2013

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Sustained immune activation during hiv infection can ultimately deplete the body"s supply of helper t cells and lead to the collapse of the host"s defences. An untreated hiv infection exhibits distinct phases, in which the loss of helper t cells happens at different rates and appears to be driven by different mechanisms. In the acute or initial, phase, hiv virions enter the host"s body and begin to replicate. Hiv gains entry into a host cell by first latching onto the cell-surface protein cd4, then binding to a coreceptor. The coreceptor used by most of the hiv strains responsible for new infections is ccr5: these viral strains can thus infect dendritic cells, macrophages, regulatory t cells, and especially memory and effector helper t cells. The acute phase ends when viral replication slows and the concentration of virions in the blood drops: this slow down may be because that the virus simply runs short of host cells it can easily invade.

Related Questions

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.

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

BIOC31H3 Lecture Notes - Azide, Reverse Transcriptase, Mutation Rate

Document Summary

Get access

Related Documents

BIOB51H3 Chapter Notes -Transversion, Allopatric Speciation, Phenotype

BIOL359 Chapter Notes - Chapter 1: Genetic Drift, Hominidae, Aids

BIOL359 Chapter Notes - Chapter 1: Tryptophan, Trim5Alpha, Genetic Drift

Related Questions