Viruses + Monoclonal Antibodies

Question 1

What are viruses?

Answer 1

Viruses are obligate intracellular parasites, meaning they only exist and reproduce as parasites within living organisms.

Question 2

What is a characteristic of all viruses?

Answer 2

All viruses are pathogenic and can withstand drying and long storage periods.

Question 3

What shapes do viruses typically have?

Answer 3

Viruses have geometric shapes but variations in genetic material and structure of capsid and envelope

Question 4

What variations exist in the structure of viruses?

Answer 4

Viruses vary in their genetic material and the structure of their protein coat and envelope.

Question 5

What is the capsid of a virus?

Answer 5

The capsid is made of repeating units of capsomeres, which minimize the amount of genetic material needed for coat production.

Question 6

What can the capsid of a virus be covered by?

Answer 6

The capsid can be covered by a lipid envelope produced by the host cell, which makes it easier for viruses to pass between cells but makes them vulnerable to substances that dissolve the lipid membrane.

Question 7

How do viruses attach to host cells?

Answer 7

Viruses attach to host cells using viral attachment particles, which target specific receptors on the host cell membrane.

Question 8

Are viruses specific to the tissues they infect?

Answer 8

Yes, viruses are specific in the tissues they attack due to specific antigens

Question 9

What are DNA viruses?

Answer 9

DNA viruses have viral DNA that acts directly as a template for new viral DNA and mRNA to induce the synthesis of viral proteins

Question 10

Can you give examples of DNA viruses?

Answer 10

Examples of DNA viruses include adenovirus (colds), smallpox, and lambda phage.

Question 11

What are RNA viruses?

Answer 11

RNA viruses do not produce DNA. They only contain single-stranded RNA (ssRNA). MORE LIKELY TO MUTATE

Question 12

What is the difference between positive and negative RNA viruses?

Answer 12

Positive RNA viruses act directly as mRNA and are translated by ribosomes (e.g., SARS, polio, Hep C), while negative RNA viruses must have their RNA transcribed before translation (e.g., Ebola, measles, influenza).

Question 13

What are RNA retroviruses?

Answer 13

RNA retroviruses have a protein capsid and lipid envelope, and their single strand of viral RNA directs the synthesis of reverse transcriptase. This enzyme makes DNA from the viral RNA, which then integrates into the host DNA and is used as template for new viral genome and proteins.

Question 14

Can you give examples of RNA retroviruses?

Answer 14

Examples of RNA retroviruses include HIV and some forms of leukemia.

Question 15

How is HIV transmitted?

Answer 15

HIV is transmitted through the exchange of bodily fluids.

Question 16

What is the structure of HIV?

Answer 16

HIV has two strands of viral RNA, a lipid bilayer envelope with glycoproteins, and other structures similar to normal RNA retroviruses, including attachment proteins.

Question 17

How does HIV replicate in the body?

Answer 17

HIV infects T-helper cells and changes its protein coat constantly, so it is not recognized as a pathogen. The viral RNA enters the cell, and reverse transcriptase makes a DNA copy, which binds to the host cell’s chromosomes. The viral DNA is replicated each time the host cell divides.

Question 18

What effect does HIV have on the immune system?

Answer 18

HIV reduces the number of T-helper cells, which prevents B cells from being activated, leading to an inability to produce antibodies.

Question 19

What are the symptoms of AIDS?

Answer 19

Shortly after infection, mild flu-like symptoms appear, but as the virus activates, it destroys immune cells, causing opportunistic infections (e.g., TB), which can lead to death due to the inability to produce antibodies.

Question 20

How are drugs used in HIV treatment?

Answer 20

Drugs are created to slow the spread of HIV throughout the body.

Question 21

How do bacteriophages replicate?

Answer 21

Bacteriophages inject their genome into the host, and most of the viral genome remains outside. The viral DNA forms a plasmid inside the bacterium.

Question 22

What is the process of virus entry into host cells?

Answer 22

Viruses can enter host cells via endocytosis, followed by digestion of the capsid, or by fusion of the viral envelope with the host cell membrane and release of viral genetic material into the cell.

Question 23

How do DNA viruses replicate?

Answer 23

DNA viruses can follow two pathways:

Lysogenic pathway: The virus enters a latent state as a provirus, where viral genes produce a repressor protein that prevents the production of viral proteins by making it impossible to translate viral DNA. VIRUSES ACTIVATED WHEN HOST IS DAMAGED CAUSING REPRESSOR PROTEINS TO DECREASE
Lytic pathway: The viral genetic material is replicated separately from the host DNA, leading to the production of new viral particles and causing the host cell to burst (virulent).

Question 24

What happens when a virus in the lysogenic state is activated?

Answer 24

The repressor protein decreases, and the viral DNA becomes active, leading to the replication of the virus.

Question 25

How do RNA viruses replicate?

Answer 25

Positive RNA viruses: The viral RNA is used directly as mRNA for translation into proteins and the production of RNA polymerase.
Negative RNA viruses: The RNA replicase enzyme transcribes the RNA strand using free bases in host cell to produce a sense strand that can be translated.
RNA retroviruses: The viral RNA is translated into DNA by reverse transcriptase, which is then inserted into the host’s DNA. Host cell transcriptase enzymes make new viral mRNA and genome

Question 26

What are the ways to treat viral infections?

Answer 26

Treatment strategies include targeting receptors on host cells, inhibiting enzymes involved in viral transcription or translation, and inhibiting protease enzymes that allow new viruses to exit host membranes.

Question 27

What is vaccination?

Answer 27

Vaccination involves introducing a suspension of antigens into the body to induce artificial active immunity, which triggers the production of specific antibodies by plasma cells.

Question 28

What are the types of vaccines?

Answer 28

Live attenuated vaccines: These use weakened pathogens to trigger a primary immune response and provide long-lasting immunity. However, they may not be suitable for immunocompromised individuals (e.g., MMR vaccine).
Inactive vaccines: These use killed pathogens or parts of pathogens, which cannot cause disease. They require booster doses and may use adjuvants to promote a longer-lasting immune response (e.g., polio and diphtheria vaccines).
Cross breeding: new viruses produced with antigens from same cell eg influenza with new strains

Question 29

What is antigenic variation?

Answer 29

Antigenic variation refers to the changes in antigens on the surface of viruses, which can complicate immune responses. Caused by eukaryotic viruses

Question 30

What are antigenic drift and antigenic shift?

Answer 30

Antigenic drift: Small changes in the shape and structure of antigens over time.
Antigenic shift: A major change in a strain of a virus, often leading to the emergence of new strains.

Question 31

What is antigenic concealment?

Answer 31

Antigenic concealment occurs when a virus hides its antigens inside cells or under a protein coat, or when it infects parts of the body that are difficult to reach by the immune system (e.g., HIV hiding in macrophages/T-cells or cholera in the small intestine).

Question 32

What are some ethical issues in vaccination?

Answer 32

Ethical issues include animal testing, obtaining consent for vaccination (especially for children), financial pressures to enter trials, the risk of side effects, deciding who to vaccinate first, and ensuring low-income countries have access to vaccines.

Question 33

What is herd immunity?

Answer 33

Herd immunity occurs when a sufficiently large proportion of the population has been vaccinated, making it difficult for a pathogen to spread within that population, thereby protecting those who cannot be vaccinated.

Question 34

What is ring immunity?

Answer 34

Ring immunity involves vaccinating individuals working near a vulnerable person to prevent the spread of the disease to that person.

Question 35

Why was the smallpox vaccination successful?

Answer 35

Smallpox vaccination was successful because:

The virus was stable and did not mutate.
The vaccine was live attenuated and could be produced cheaply.
It could be freeze-dried and stored at high temperatures, making it suitable for the tropics- transported without becoming unviable.
The symptoms were easy to identify, allowing for effective surveillance.
Humans were the only reservoirs of infection, making it easier to break the transmission cycle.

Question 36

What is active immunity?

Answer 36

Active immunity occurs when an antigen enters the body and triggers a specific immune response, leading to the production of memory cells and plasma cells for long-term immunity.

Question 37

What is passive immunity?

Answer 37

Passive immunity occurs when antibodies are transferred to an individual without activating their immune system, so no memory cells are produced. Examples include antibodies from breast milk, colostrum, placenta, or transfusions, IgA to protect against respiratory and GI tract infections

Question 38

What are monoclonal antibodies used for?

Answer 38

Monoclonal antibodies are used for diagnostic purposes (e.g., pregnancy tests, HIV diagnosis, cancer detection, tissue typing) and therapeutic purposes (e.g., treating rabies, preventing organ rejection, cancer treatment, autoimmune diseases).

Question 39

How are monoclonal antibodies produced for diagnosing blood clots in DVT px?

Answer 39

To detect blood clots, a mouse is injected with human fibrin. The mouse plasma cells produce antibodies against fibrin and collected form mouse spleen, which are then fused with tumor cells to form hybridomas. These hybridomas produce anti-fibrin antibodies, which are labeled with radioactive chemicals to detect clots. Gamma ray camera used to detect location of radioactively labelled antibody.

Question 40

What is enzyme-linked immunosorbent assay (ELISA)?

Answer 40

ELISA is a test that uses an enzyme attached to an antibody to produce a colored product when binding with a specific substrate.

Question 41

What are the types of ELISA?

Answer 41

Direct ELISA: Uses a single antibody specific to the antigen being tested (e.g., HIV test).
Indirect ELISA: Uses two antibodies, typically used for tests like prostate cancer screening, where the antigen is detected by antibodies attached to the vessel bottom.

Question 42

Therapeutic uses of monoclonal antibodies?

Answer 42

purified antibodies for rabies
preventing rejection of organs by intervening with T cells, autoimmune therapies by binding to antibodies responsible for inflammatory response eg in rheumatoid arthritis/asthma
leukaemia, multiple sclerosis and myasthenia gravis); the antibody (rituximab) binds to cell surface receptor proteins on B-cells (not plasma cells) and causes the death of the cells
preventing blood clots post angioplasty- binding to receptors on platelet and inhibiting fibrinogen
Herceptin (trastuzumab) used to treat breast cancer- recognises receptor proteins on the surface of cancer cells and binds to them allowing the immune system to identify and destroy them
ipilimumab binds to a protein produced by T-cells (whose role is to reduce the immune response) which results in the immune system remain active against the melanoma cancer cell

Question 43

How are monoclonal antibodies from animal cells genetically engineered?

Answer 43

Genetically engineering polypeptide chain to produce human antibodies and attach glycoproteins to heavy polypeptide chains as it is in humans