Viral Path Immun Response MCQ's

1. During most viral infections, lack of which cell surface molecule would be the most likely to cause a major problem to the defense of the host?

MHC class I

CD23

CD14

CD20

During viral infections, MHC class I molecules play a crucial role in presenting viral antigens to cytotoxic T cells, which then eliminate infected cells. If there is a lack of MHC class I molecules, the immune system would be unable to recognize and eliminate virus-infected cells effectively. This would result in a major problem for the defense of the host, as the virus could replicate and spread without being targeted by the immune system.

Explanation

During viral infections, MHC class I molecules play a crucial role in presenting viral antigens to cytotoxic T cells, which then eliminate infected cells. If there is a lack of MHC class I molecules, the immune system would be unable to recognize and eliminate virus-infected cells effectively. This would result in a major problem for the defense of the host, as the virus could replicate and spread without being targeted by the immune system.

2. Which structure serves as the target for neutralizing antibodies when dealing with an enveloped, (-) ssRNA virus?

RNA

Capsid

Lipid bilayer

Envelope glycoprotein

RNA polymerase

Neutralizing antibodies target the envelope glycoprotein of enveloped, (-) ssRNA viruses. The envelope glycoprotein is located on the surface of the virus and plays a crucial role in viral entry into host cells. By binding to the envelope glycoprotein, neutralizing antibodies can prevent the virus from attaching to and entering host cells, thereby neutralizing its infectivity. This makes the envelope glycoprotein an important target for developing vaccines and antiviral therapies against enveloped, (-) ssRNA viruses.

Explanation

Neutralizing antibodies target the envelope glycoprotein of enveloped, (-) ssRNA viruses. The envelope glycoprotein is located on the surface of the virus and plays a crucial role in viral entry into host cells. By binding to the envelope glycoprotein, neutralizing antibodies can prevent the virus from attaching to and entering host cells, thereby neutralizing its infectivity. This makes the envelope glycoprotein an important target for developing vaccines and antiviral therapies against enveloped, (-) ssRNA viruses.

3. Host defense against viral infections relies on a strong TH_o,,1 response. The T-helper-1 response is characterized by the secretion of:

1FN--y and 1L-12

IL-4 and IFN-y

IL-4 and 1L-12

IL-10 and IFN--y

1L-4 and TNF-ct

The correct answer is 1FN--y and 1L-12. The T-helper-1 response is characterized by the secretion of these cytokines. IFN-y is a pro-inflammatory cytokine that plays a crucial role in the defense against viral infections by activating immune cells and enhancing their antiviral functions. IL-12 is another pro-inflammatory cytokine that stimulates the production of IFN-y and promotes the differentiation of T-helper-1 cells. Therefore, a strong TH1 response, characterized by the secretion of IFN-y and IL-12, is important in host defense against viral infections.

Explanation

The correct answer is 1FN--y and 1L-12. The T-helper-1 response is characterized by the secretion of these cytokines. IFN-y is a pro-inflammatory cytokine that plays a crucial role in the defense against viral infections by activating immune cells and enhancing their antiviral functions. IL-12 is another pro-inflammatory cytokine that stimulates the production of IFN-y and promotes the differentiation of T-helper-1 cells. Therefore, a strong TH1 response, characterized by the secretion of IFN-y and IL-12, is important in host defense against viral infections.

4. As a means of virulence, some viruses encode virokines. A case in point is vIL-10 which is encoded by the Epstein-Barr virus (EBV). Which of the following immune functions would be most affected by this virokine?

The TH1 response

The TH2 response

The lectin-binding pathway of complement activation

The classical pathway of complement activation

The alternate pathway of complement activation

The TH1 response is the immune function that would be most affected by the virokine vIL-10 encoded by the Epstein-Barr virus (EBV). Virokines are proteins produced by viruses that mimic or interfere with host immune signaling molecules. vIL-10 is a viral mimic of the host cytokine IL-10, which is a key regulator of the TH1 immune response. By mimicking IL-10, vIL-10 can suppress the TH1 response, which is involved in cell-mediated immunity and defense against intracellular pathogens. Therefore, the presence of vIL-10 would likely dampen the TH1 response and impair the immune system's ability to fight off certain infections.

Explanation

The TH1 response is the immune function that would be most affected by the virokine vIL-10 encoded by the Epstein-Barr virus (EBV). Virokines are proteins produced by viruses that mimic or interfere with host immune signaling molecules. vIL-10 is a viral mimic of the host cytokine IL-10, which is a key regulator of the TH1 immune response. By mimicking IL-10, vIL-10 can suppress the TH1 response, which is involved in cell-mediated immunity and defense against intracellular pathogens. Therefore, the presence of vIL-10 would likely dampen the TH1 response and impair the immune system's ability to fight off certain infections.

5. Virulence factors play an important role in the pathogenesis of viral infections, and some of these factors alter host defence mechanisms. One such factor is the HCMV (human cytomegalovirus) U56 protein that inhibits TAP proteins (transporters associated with antigen processing). By inhibiting TAP, which host defence mechanism is affected by U56?

B-cell-mediated antigen presentation to naive CD4 cells

CD4+-mediated B-cell activation

Dendritic cell-mediated antigen presentation to naive CD4+ cells

Somatic cell-mediated antigen presentation to activated CD8+ ceilsCD4+ -mediated CD8+ cell activation

The HCMV U56 protein inhibits TAP proteins, which are involved in somatic cell-mediated antigen presentation to activated CD8+ cells. This means that the U56 protein affects the ability of somatic cells to present antigens to activated CD8+ cells, thereby compromising the host's immune response against viral infections.

Explanation

The HCMV U56 protein inhibits TAP proteins, which are involved in somatic cell-mediated antigen presentation to activated CD8+ cells. This means that the U56 protein affects the ability of somatic cells to present antigens to activated CD8+ cells, thereby compromising the host's immune response against viral infections.

6. You are now aware that there are a number of T cell types associated with specfic immune responses to particular pathogens. Which type of pathogen would you most associate with TH17 responses?

Intracellular bacteria

Extracellular bacteria

Metazoan parasites

Viruses

TH17 responses are primarily associated with extracellular bacteria. This is because TH17 cells are involved in the immune response against pathogens that reside outside of host cells, such as bacteria that infect the extracellular spaces of tissues. These cells help recruit other immune cells to the site of infection and promote the production of antimicrobial peptides and pro-inflammatory cytokines to eliminate the bacteria. Intracellular bacteria, on the other hand, are targeted by other T cell types such as TH1 cells. Metazoan parasites and viruses also elicit different immune responses, involving different types of T cells.

Explanation

TH17 responses are primarily associated with extracellular bacteria. This is because TH17 cells are involved in the immune response against pathogens that reside outside of host cells, such as bacteria that infect the extracellular spaces of tissues. These cells help recruit other immune cells to the site of infection and promote the production of antimicrobial peptides and pro-inflammatory cytokines to eliminate the bacteria. Intracellular bacteria, on the other hand, are targeted by other T cell types such as TH1 cells. Metazoan parasites and viruses also elicit different immune responses, involving different types of T cells.

7. "Virulence of viruses can be calculated in a number of ways. For Rhinovirus, for example, the HID₅₀ is sometimes given as between 0.1-6 ICID₃₀. What does TCID50 stand for?

The dose required to infect 50% of tissue culture cells

The dose required to kill 50% of infected tissue culture cells

Fifty percent of the dose required to infect all tissue culture cells

Fifty percent of the dose required to kill infected tissue culture cells

TCID50 stands for Tissue Culture Infective Dose 50. It is a measurement used to determine the concentration of a virus that is needed to infect 50% of a specific type of tissue culture cells. This measurement helps in assessing the infectivity and virulence of a virus.

Explanation

TCID50 stands for Tissue Culture Infective Dose 50. It is a measurement used to determine the concentration of a virus that is needed to infect 50% of a specific type of tissue culture cells. This measurement helps in assessing the infectivity and virulence of a virus.

8. What would be the phenotype of cells infected with HIV-1 during the primary stage of the infection?

CD4 CXCR4

CD8 CCR5

CD4 CCR5

CD8 / CXCR4

During the primary stage of HIV-1 infection, the virus primarily targets and infects CD4 T cells, which are immune cells that express the CD4 receptor. Additionally, the virus binds to the CCR5 co-receptor on the surface of these CD4 T cells. Therefore, the phenotype of cells infected with HIV-1 during the primary stage would be CD4 CCR5.

Explanation

During the primary stage of HIV-1 infection, the virus primarily targets and infects CD4 T cells, which are immune cells that express the CD4 receptor. Additionally, the virus binds to the CCR5 co-receptor on the surface of these CD4 T cells. Therefore, the phenotype of cells infected with HIV-1 during the primary stage would be CD4 CCR5.

9. An 8-year-old boy is diagnosed with swine flu. His chest x-ray is consistent with a viral pneumonia. Which of the following is responsible for his pneumonia?

Hemagglutinin and neuraminidase

Lack of adherence factors

Phagocytosis by alveolar macrophages

Toxin that paralyzes cilia of respiratory epithelium

Phagocytosis by neutrophils

Hemagglutinin and neuraminidase are responsible for the pneumonia in the 8-year-old boy diagnosed with swine flu. These are surface proteins found on the influenza virus. Hemagglutinin helps the virus attach to host cells, while neuraminidase helps the virus release from infected cells. In the case of swine flu, the viral pneumonia is caused by the influenza virus, and the presence of hemagglutinin and neuraminidase indicates the involvement of the virus in the pneumonia.

Explanation

Hemagglutinin and neuraminidase are responsible for the pneumonia in the 8-year-old boy diagnosed with swine flu. These are surface proteins found on the influenza virus. Hemagglutinin helps the virus attach to host cells, while neuraminidase helps the virus release from infected cells. In the case of swine flu, the viral pneumonia is caused by the influenza virus, and the presence of hemagglutinin and neuraminidase indicates the involvement of the virus in the pneumonia.

10. When LPS from extracellular Gram-negative bacteria is released into the patient, it interacts with a number of immune pattern recognition receptors which eventually results in activation of macrophages. What molecule initially binds to LPS and transfers this to macrophage-produced CD14?

MBP

LBP

TLR-4

CRP

Lipopolysaccharide-binding protein is a protein that in humans is encoded by the LBP gene.[1][2]

LBP is a soluble acute-phase protein that binds to bacterial lipopolysaccharide (or LPS) to elicit immune responses by presenting the LPS to important cell surface pattern recognition receptors called CD14 and TLR4.[3]

The protein encoded by this gene is involved in the acute-phase immunologic response to gram-negative bacterial infections. Gram-negative bacteria contain a glycolipid, lipopolysaccharide (LPS), on their outer cell wall. Together with bactericidal permeability-increasing protein (BPI), the encoded protein binds LPS and interacts with the CD14 receptor, probably playing a role in regulating LPS-dependent monocyte responses.

Explanation

Lipopolysaccharide-binding protein is a protein that in humans is encoded by the LBP gene.[1][2]

LBP is a soluble acute-phase protein that binds to bacterial lipopolysaccharide (or LPS) to elicit immune responses by presenting the LPS to important cell surface pattern recognition receptors called CD14 and TLR4.[3]

The protein encoded by this gene is involved in the acute-phase immunologic response to gram-negative bacterial infections. Gram-negative bacteria contain a glycolipid, lipopolysaccharide (LPS), on their outer cell wall. Together with bactericidal permeability-increasing protein (BPI), the encoded protein binds LPS and interacts with the CD14 receptor, probably playing a role in regulating LPS-dependent monocyte responses.

11. A 32-year old man with AIDS develops symptoms of retinitts. Which enzyme is encoded by the pathogen most likely responsible for the retinitts?

Integrase

5N-methyl capping enzyme

Neuraminidase

RNA-dependent RNA polymerase

Thymidine kinase

Im guessing its CMV

Explanation

Im guessing its CMV

12. A 23-year-old male patient presents with urethritis, including balanitis; arthritis, and uni;ateral uveitis. He admits to unprotected sex with a number of partners but denies any indications of a sexually transmitted disease. However, upon questioning the patient does admit that he might have had a temporary, slight, milky discharge from his urethra, which he had dismissed as being of no significance. While you are waiting for laboratory test results which of the following might you consider likely?

The patient had been infected by Neisseria gonnorrhoeae and would have low serum Rf levels

The patlent had not been infected with any infectious agent but would have high serum Rf levels

The patient had been infected with Neisseria gonnorrhoeae and would have high serum Rf

The patient had been infected with Chlamydia trachomatis and would have low serum Rf levels

The patient had been infected with Chlarnyclia trachornaris and would have high serum Rf levels

The patient's symptoms of urethritis, balanitis, arthritis, and unilateral uveitis, along with a history of unprotected sex, suggest a sexually transmitted infection. The fact that the patient had a temporary, milky discharge from his urethra further supports this. Chlamydia trachomatis is a common cause of urethritis and can also lead to complications such as reactive arthritis and uveitis. Rheumatoid factor (Rf) levels are typically low in Chlamydia infections. Therefore, it is likely that the patient has been infected with Chlamydia trachomatis and would have low serum Rf levels.

Explanation

The patient's symptoms of urethritis, balanitis, arthritis, and unilateral uveitis, along with a history of unprotected sex, suggest a sexually transmitted infection. The fact that the patient had a temporary, milky discharge from his urethra further supports this. Chlamydia trachomatis is a common cause of urethritis and can also lead to complications such as reactive arthritis and uveitis. Rheumatoid factor (Rf) levels are typically low in Chlamydia infections. Therefore, it is likely that the patient has been infected with Chlamydia trachomatis and would have low serum Rf levels.