Block 9 Micro Viral Pathogenesis

17 Questions | Total Attempts: 384

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Block 9 Micro Viral Pathogenesis - Quiz

Pathogens are microorganisms that cause disease and we get to understand how they do so by taking a pathogenesis course. Pathogens of all classes must have mechanisms for entering their host and for evading immediate destruction by the host immune system. To see how much you understood from block 9 micro viral pathogenesis take up the quiz below.


Questions and Answers
  • 1. 
    A 1-year-old toddler is admitted to the hospital in February following an abrupt onset of vomiting followed by watery diarrhea accompanied by low-grade fever. On admission, the child appears somnolent, has a fever of 38.8C (101.8F). His pulse is 130/min, respiratory rate 36/min, blood pressure 100/60 mmHg, and decreased skin turgor. Blood tests reveal an elevated white blood cell count (15,000/L) with 75% polymorphonuclear leukocytes. A stool sample is sent to the microbiology lab for analysis. Results reveal watery stools with no mucus, blood, leukocytes or parasites. A rapid antigen test is positive for a naked, segmented, dsRNA virus, so no stool culture is required. The diarrhea suffered by this child can be partially attributed to a viral protein (rotavirus NSP4) that alters the permeability of intestinal epithelial cell tight junctions and inhibits the glucose-coupled Na+ transport of these same cells, thereby increasing osmotic gap. What best describes this virulence mechanism?
    • A. 

      Alteration of viral replication or of the cell cycle

    • B. 

      Alteration of host defense mechanisms

    • C. 

      Facilitation of viral spread

    • D. 

      Toxicity

  • 2. 
    Virulence mechanisms play an important role in the pathogenesis of viral infections and these include mechanisms (1) that alter viral replication, (2) that alter host defense mechanisms, (3) that facilitate viral spread and (4) that are toxic to the host. Which of the following mechanisms would most likely be involved in viral spread in the human population?
    • A. 

      Apoptosis

    • B. 

      Autophagy

    • C. 

      Virokines

    • D. 

      Viroceptors

    • E. 

      Antigenic drift

  • 3. 
    Which of the following assertions is true?
    • A. 

      Terminally differentiated cells such as neurons are permissive to viral infection.

    • B. 

      Viral dissemination is invariably hindered by inflammation

    • C. 

      Polarized cells are non-permissive to viral infection

    • D. 

      Syncytia formation is a means of systemic dissemination

    • E. 

      Low pH is always detrimental to viruses

  • 4. 
    Which of the following statements is false?
    • A. 

      The successful infection of a host requires a minimum number of inoculating viruses

    • B. 

      The successful infection of a host requires terminally differentiated cells

    • C. 

      The successful infection of a host requires that the host cell is susceptible to the infection.

    • D. 

      The successful infection of a host requires that the host possesses inefficient local viral defenses at the time of infection

    • E. 

      The successful infection of a host requires that the host cells are accessible to the viruses.

  • 5. 
    Virulence mechanisms play an important role in the pathogenesis of viral infections and these include mechanisms (1) that alter viral replication, (2) that alter host defense mechanisms, (3) that facilitate viral spread and (4) that are toxic to the host. Which of the following mechanisms would favour viral replication?
    • A. 

      Apoptosis

    • B. 

      Virally-encoded proteins that increase cell cycling

    • C. 

      Virokines

    • D. 

      Viroceptors

    • E. 

      The tandem action of the double-stranded RNA (dsRNA) binding proteins 2’,5’-oligo(A) synthetase and RNase L

  • 6. 
    Virulence mechanisms play an important role in the pathogenesis of viral infections and some of these factors alter host defense mechanisms. One such factor is adenovirus E3-gp19K which inhibits MHC-I transport to the cell surface. Which host defense mechanism is affected by E3-gp19K?
    • A. 

      B cell-mediated antigen presentation to naïve CD4+ cells

    • B. 

      CD4+-mediated B cell activation

    • C. 

      Dendritic cell-mediated antigen presentation to naïve CD4+ cells

    • D. 

      Somatic cell-mediated antigen presentation to activated CD8+ cells

    • E. 

      CD4+-mediated CD8+ cell activation

  • 7. 
    All but one of these statements are true. Which one?
    • A. 

      Modes of viral transmission often dictate the tissues that will be infected and infected tissues often determine modes of transmission

    • B. 

      Modes of viral transmission seldom dictate the tissues that will be infected, but infected tissues often determine modes of transmission

    • C. 

      Modes of viral transmission often dictate the tissues that will be infected, but infected tissues seldom determine modes of transmission

    • D. 

      Modes of viral transmission seldom dictate the tissues that will be infected nor do infected tissues ever determine modes of transmission

    • E. 

      Modes of viral transmission randomly dictate the tissues that will be infected and infected tissues have random modes of transmission

  • 8. 
    What is the most direct mode of tissue damage resulting from virus infections?
    • A. 

      Cell destruction by NK cells

    • B. 

      Cell destruction by CTLs

    • C. 

      Cytolysis due to viral release

    • D. 

      Cell destruction by macrophages

    • E. 

      Cell destruction by neutrophils

  • 9. 
    Besides cell lysis, what is(are) the most common mode(s) of tissue damage resulting from viral infections?
    • A. 

      Cell destruction by NK cells

    • B. 

      Cell destruction by CTLs

    • C. 

      Cell destruction by mast cells

    • D. 

      Cell destruction by macrophages

    • E. 

      Cell destruction by neutrophils

  • 10. 
    All but one of these statements are true. Which one?
    • A. 

      Retroviral gp41 (TM protein) increases HIV virulence

    • B. 

      Some viruses incorporate host-cell surface proteins

    • C. 

      Virokines are antiviral host molecules

    • D. 

      Pustules can be a way to spread an infection from one host to another.

    • E. 

      RNA-dependent RNA polymerase is prone to error and is a cause for increased virulence.

  • 11. 
    A 37-year-old female presents to her gynecologist for a routine exam. Pertinent history reveals that it has been 5 years since her last exam, she is a smoker (half pack per day), had her first intercourse at age 15, has had 9 sexual partners over her lifetime and is on oral contraceptives. Gynecological exam is normal, except for lesions on the cervix seen by colposcopy. A Papanicolaou smear (Pap smear) from a lesion reveals the presence of high-grade squamous intraepithelial lesions (HSILs). In situ hybridization performed on a cervical biopsy from the same patient shows that cervical epithelial cells in the lesions contain L1 DNA belonging to the Human papillomavirus type 16. Inhibition of cyclin-dependent kinase inhibitors by HPV-16 protein E7 contribute significantly to the cellular transformation process. What best describes this pathophysiological mechanism?
    • A. 

      Alteration of viral replication or of the cell cycle

    • B. 

      Alteration of host defense mechanisms

    • C. 

      Facilitation of viral spread

    • D. 

      Toxicity

  • 12. 
    Virulence mechanisms play an important role in the pathogenesis of viral infections. Such mechanisms are involved in (1) the alteration of viral replication, (2) the alteration of host defense mechanisms, (3) the facilitation of viral spread and (4) host toxicity. Which of the following is an example of a virulence mechanism that contributes to disease due to the production of a toxin?
    • A. 

      Human cytomegalovirus viroceptor expression

    • B. 

      Rotavirus NSP4 protein expression

    • C. 

      Influenzavirus HA (hemagglutinin) protein expression

    • D. 

      Human papillomavirus DNA polymerase expression

  • 13. 
    Human herpesvirus 1 (HSV-1) gE-gI is a virally-encoded Fc-gamma receptor (crystallizable fragment-gamma receptor, or vFc-R) that localizes in both the virus envelope and the cell membrane of HSV-1-infected cells, thereby protecting the virus from clearance by the immune system. Which of the following immune responses is(are) most likely to be affected by gE-gI?
    • A. 

      Major histocompatibility complex class I (MHC class I)-antigen presentation

    • B. 

      Alternative pathway of complement activation

    • C. 

      Antibody-dependent cell cytotoxicity (ADCC)

    • D. 

      CD8+ cytotoxic T lymphocyte (CTL) cytotoxicity

  • 14. 
    16.1) A previously healthy 52-year-old man presents in the early stages of cirrhosis. It turns out that his cirrhosis is the result of an infection with the hepatitis C virus he acquired three decades ago. Contributing factors for the development of silent disease are (1) the capacity of the virus to suppress IFN-secretion by interfering with signaling downstream of TLR-3 and RIG-1, as well as (2) suppressing STAT-1 activation. How do these factors benefit the virus?
    • A. 

      Suppression of ADCC

    • B. 

      Suppression of NK cell-mediated cell cytotoxicity

    • C. 

      Suppression of CTL-mediated cell cytotoxicity

    • D. 

      Suppression of classical pathway of complement activation

    • E. 

      Suppression of Pkr- and 2’,5’ OAS/RNase L-mediated apoptosis

  • 15. 
    16.2) What best describes this virulence mechanism?
    • A. 

      Alteration of viral replication or of the cell cycle

    • B. 

      Alteration of host defense mechanisms

    • C. 

      Facilitation of viral spread

    • D. 

      Toxicity

  • 16. 
    17.1) Orf virus (Poxviridae), the etiologic agent for a rare occupational zoonosis called contagious pustular dermatitis, encodes a homologue of IL-10. Which of the following functions would mostly be affected by this homologue?
    • A. 

      Alternate pathway of complement activation

    • B. 

      Lectin pathway of complement activation

    • C. 

      Classical pathway of complement activation

    • D. 

      T helper 1 response

    • E. 

      T helper 17 response

  • 17. 
    17.2) What term best describes this molecule?
    • A. 

      Viroceptor

    • B. 

      Virokine

    • C. 

      Cytokine

    • D. 

      Virosubducer

    • E. 

      Cytoceptor

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