Midterm 2

Question 1

Which statement is true?
a. It could take days or months for infected animals to show clinical symptoms
after virus exposure
b. Clinical symptoms are obvious during incubation period in which virus replicates primarily at the entry site
c. Many animal viruses disseminate within the host via viremia
d. Different viruses have different sites of shedding and shedding patterns
e. Adaptive immune responses usually develop after virus dissemination

Answer 1

b. Clinical symptoms are obvious during incubation period in which virus replicates primarily at the entry site

Question 2

Rabbit pox virus was used as a bioweapon to control the exotic rabbit population in Australia. How did rabbit mortality rates change during the three successive releases of rabbit pox? Why?
a. The mortality rate remained the same because the virus and the host species are the same in the three outbreaks.
b. The mortality rate gradually increased from first to the third epidemics because the virus was selected to be more virulent to the host during the process.
c. The mortality rate gradually dropped from first to the third epidemics because rabbits with more resistance to disease were selected and made up a larger proportion of the rabbit population at each epidemic.
d. The mortality rate first increased in the second epidemics because the emergence of more virulent virus, however the mortality rate dropped in the third epidemics due to selection of more resistant hosts
e. The mortality rate dropped for the second epidemics due to the development of host resistance, however the emergence of the more virulent variant lead to the increase of mortality rate of the third epidemics

Answer 2

c. The mortality rate gradually dropped from first to the third epidemics because rabbits with more resistance to disease were selected and made up a larger proportion of the rabbit population at each epidemic.

Question 3

What is the most likely outcome for most members of a population that become infected with a common (endemic) virus?
a. Asymptomatic or mild infection
b. Moderate disease
c. Severe disease
d. Death of organism from the viral disease

Answer 3

a. Asymptomatic or mild infection

Question 4

Which statement is true?
a. Environmental factors such as humidity have no effect on virion stability
b. In some viral infections, uncontrolled host immune responses lead to
immunopathology and play major roles in viral pathogenesis.
c. Sialic acid is the receptor for influenza virus and it is expressed ubiquitously among cells. As a result, influenza virus can successfully infect and replicate in cells in most organs.
d. To be a successful parasite, animal viruses must complete the following steps and no others: infect a host, disseminate to tissues and exit the host.
e. All of above are true

Answer 4

b. In some viral infections, uncontrolled host immune responses lead to
immunopathology and play major roles in viral pathogenesis.

Question 5

Which virus can be transmitted through the germ line (gametes)? a. Herpes Simplex Virus type 1(double stranded DNA virus) b. Parvovirus (single stranded DNA virus)
c. Poliovirus (single stranded, positive sense RNA virus)
d. Rotavirus (double stranded RNA virus)
e. Moloney Murine Leukemia Virus (MMLV, a retrovirus)

Answer 5

e. Moloney Murine Leukemia Virus (MMLV, a retrovirus)

Question 6

M cells are
a. Specialized cells of the respiratory tract that produce secretions that cover the
epithelial layer
b. Specialized epithelial cells of the mucosal surface of the gastrointestinal tract that take up antigens in the gut contents to be “seen” by the host immune system.
c. Mature gastrointestinal epithelial cells that are non-dividing
d. Cells that produce tryptase, the enzyme necessary for mammalian influenza
viruses to become infectious
e. Refers to specialized mucous secreting cells that are found in both the
respiratory tract and the gastrointestinal tract

Answer 6

b. Specialized epithelial cells of the mucosal surface of the gastrointestinal tract that take up antigens in the gut contents to be “seen” by the host immune system.

Question 7

Bloody diarrhea and necrotizing enteritis are typical for canine parvovirus infection in dogs. What cell type does canine parvovirus infect?
a. Mature enterocytes
b. M cells covering domes
c. Dividing cells of the crypt
d. Lymphocytes in payer’s patch
e. Lymphocytes in intestinal epithelium

Answer 7

c. Dividing cells of the crypt

Question 8

Rotavirus infection results in watery diarrhea and blunting of villi in small intestines. What cell type does rotavirus infect?
a. Mature enterocytes
b. M cells covering domes
c. Dividing cells of the crypt
d. Lymphocytes in payer’s patch
e. Lymphocytes in intestinal epithelium

Answer 8

a. Mature enterocytes

Question 9

Which statement is not true?
a. A clinical manifestation of Varicella Zoster Virus (VZV) infection is skin rash
b. Infection with VZV is life-long.
c. VZV disease caused by a primary (initial) VZV infection is milder in an adult than as a child
d. VZV establish latency in sensory ganglion
e. All of above are not true

Answer 9

c. VZV disease caused by a primary (initial) VZV infection is milder in an adult than
as a child

Question 10

What is the primary transmission route for Norovirus (a non-enveloped RNA virus belong to Caliciviridae) in population?
a. Fecal-oral route
b. Blood
c. Respiratory route
d. Vector-dependent transmission
e. Sexual contact

Answer 10

a. Fecal-oral route

Question 11

Which virus infection of humans has the most variable incubation time?
a. Influenza virus
b. Rabies virus
c. Measles virus
d. Poliovirus
e. Herpes Simplex Virus type 1

Answer 11

b. Rabies virus

Question 12

Which statement is not true?
a. Fomites play an important role in virus spread. Frequently wash hands can significantly reduce virus transmission in populations.
b. The iceberg concept of infection represents a novel virus that first encounters a naïve population
c. The fact that humidity and temperature of the environment affect virus stability may explain the seasonality of virus infection
d. Successful prevention of a virus infection outbreak in a population by immunization requires that the majority of the population receive vaccination
e. All of the above are true.

Answer 12

b. The iceberg concept of infection represents a novel virus that first encounters a naïve population

Question 13

Which viruses can persistently infect an animal?
I. Influenza virus (ssRNA virus)
II. Papillomavirus(dsDNAvirus)
III. Cytomegalovirus (dsDNA virus)
IV. Rotavirus (dsRNA virus)
V. Epstein-Barr virus (dsDNAvirus)

a. I, III and V
b. II, III and V
c. I, II and IV
d. III, IV and V
e. I, II, III, IV and V

Answer 13

b. II, III and V

Question 14

Viruses can encode genes that affect virulence. Choose the possible mechanism how a virulence gene affects viral virulence
a. Virulence genes can affect virus replication capacity in particular cell type
b. Virulence genes can produce cytokines or receptor homologues to help the virus
evade host anti-viral response
c. Virulence genes can promote virus spread within host
d. Virulence genes can encode proteins that are toxic to cells
e. All of the above statements are possible.

Answer 14

All of the above statements are possible.

Question 15

In general, the rates of virus inactivation of enteric viruses are much ________ when compare to respiratory viruses. This reflects the fact that most enteric viruses are _______ viruses.
a. Faster, enveloped
b. Faster, non-enveloped
c. Slower, enveloped
d. Slower, non-enveloped
e. All of the above combinations are possible.

Answer 15

d. Slower, non-enveloped

Question 16

In mammals, the following are considered secondary lymphoid organs
I. Bronchus-associated lymphoid tissue
II. Bone Marrow
III. Peyer’s Patch
IV. Thymus
V. Mesenteric Lymph Node

a. I and III
b. II and IV
c. I, III, and V
d. All of the above
e. None of the above

Answer 16

c. I, III, and V

Question 17

Which Toll-like receptors are more important in virus infection?
I. TLR3
II. TLR4
III. TLR5
IV. TLR7/8
V. TLR9

a. I, III and V
b. II, III and V
c. I, II and IV
d. I, IV and V
e. I, II, III, IV and V

Answer 17

d. I, IV and V

Question 18

Where are the TLRs important in viral infection located in cells?
a. Nuclear membrane
b. Nucleus
c. Rough Endoplasmic Reticulum
d. Plasma membrane
e. Endosome

Answer 18

e. Endosome

Question 19

Which statement is true?
a. TLRs on plasma membrane recognize specific molecular patterns of free virions.
b. All TLRs signal through the Myd88 signaling cascade.
c. Activation of signaling transduction pathways by TLR ligation leads to
production of proinflammatory and anti-viral cytokines
d. Activation of NF-kB in virus infections is always TLR-dependent
e. Transfection of synthetic ssRNA into dendritic cells will lead to drastic
production of IFN-gamma

Answer 19

c. Activation of signaling transduction pathways by TLR ligation leads to
production of proinflammatory and anti-viral cytokines

Question 20

What is the key cell type responsible for initiating both innate and adaptive immune responses to a virus infection?
a. Epithelial cells
b. Neutrophils
c. Dendritic cells
d. NK cells
e. T lymphocytes

Answer 20

c. Dendritic cells

Question 21

Which of the immune system components listed below are examples of humoral antiviral mechanisms:
I. Natural Antibody
II. Macrophages
III. Complement
IV. NK cells

a. I and II
b. I and III
c. II and IV
d. I and IV
e. None of the Above

Answer 21

b. I and III

Question 22

What is the key cell type responsible for killing viral-infected cells in an antigen/virus- specific manner without presence of antibodies?
a. NK cells
b. Macrophages
c. CD4+ T cells
d. CD8+ T cells
e. B cells

Answer 22

d. CD8+ T cells

Question 23

Which isotype of antibody is most abundant in mucosal surfaces?
a. IgA
b. IgD
c. IgG
d. IgM
e. IgE

Answer 23

a. IgA

Question 24

Complement:
a. Is a cellular component of blood that is involved in control of inflammation, the
activation of phagocytes, and lysis of virus infected cells
b. Complement blocks interaction of virions with receptors
c. Is produced in the spleen
d. Activation of complement pathway can leads to formation of membrane attack complex and cell/virion lysis
e. All of the above are true

Answer 24

d. Activation of complement pathway can leads to formation of membrane attack complex and cell/virion lysis

Question 25

How does IFNa limit viral replication?
I. IFN-alpha induces synthesis of 2’5-oligoadenylate synthetase which subsequently activates endonuclease to specifically degrade viral mRNA
II. IFN-alpha blocks interaction of protein kinase and eIF2 to inhibit all protein synthesis in the cell.
III. IFN-alpha promotes cleavage of cellular eIF4G protein to inhibit cellular protein synthesis to inhibit all protein synthesis in the cell.
IV. IFN-alpha induces the protein kinase that phosphorylates eIF-2 to inhibit all protein synthesis in the cell.

a. I and II
b. I and III
c. I and IV
d. I, II and III
e. I, III and IV

Answer 25

c. I and IV

Question 26

Release of inflammatory cytokines from infected cells at the site of infection results in…
I. Proliferation and mobilization of lymphocytes in the bone marrow
II. Blocks Neutrophil and Monocyte activation and migration to the site of
infection
III. Production of complement in the spleen
IV. Generation of flu-like symptoms such as fever, lethargy
a. I and IV
b. I and II
c. I and III
d. I, II and III
e. I, III and IV

Answer 26

a. I and IV

Question 27

Which cell type serves as antibody secreting cells?
a. M cells
b. Plasma cells
c. Langerhan cells
d. NK cells
e. Macrophages

Answer 27

b. Plasma cells

Question 28

NK cells recognize and kill virus infected cells when:
I. The activating receptor on NK cells is bound to MHC class I on the infected cell
II. The inhibitory receptor on NK cells is bound to MHC class I on the infected cells
III. The inhibitory receptor on NK cells is NOT bound to MHC class I on the infected cells due to a decrease in MHC class I expression
IV. It binds to the Fc receptor of antibody bound to viral antigen on the target cell surface

a. I and II
b. I and III
c. I and IV
d. II and IV
e. III and IV

Answer 28

e. III and IV

Question 29

Which of the following is true about apoptosis
I. Activation of the caspase pathway prevents apoptosis from occurring
II. High concentration of TNF produced by some cytotoxic cells can lead to
cell apoptosis
III. RNA viruses are usually the only viruses that code for proteins that
inhibit steps of apoptosis initiation
IV. High levels of cytoplasmic calcium or nuclear p53 can initiate apoptosis

a. All of the Above
b. I and III
c. II and IV
d. I and IV
e. II and III

Answer 29

c. II and IV

Question 30

Which isotype of antibody is most abundant in serum and has longest half-life?
a. IgG
b. IgM
c. IgA
d. IgD
e. IgE

Answer 30

a. IgG

Question 31

Which of the statements is true:
a. IgM is the first antibody subtype produced in response to a viral infection
b. IgM is at relatively high concentration levels in the serum at late stage of viral infection
c. IgM cannot activate complement.
d. IgM is not involved in the antiviral response, as it is primarily involved in allergic
reactions
e. IgM is primarily involved in antibody dependent cellular cytotoxicity

Answer 31

a. IgM is the first antibody subtype produced in response to a viral infection

Question 32

In general, what is true about the difference between Th1 and Th2 responses in viral infections?
a. A Th1 response cannot suppress a Th2 response
b. A Th1 response is characterized by a high level of IFN-gamma secretion
c. A Th2 response generates a cell-mediated response with lots of cytotoxic T cells
d. A Th1 response generates an antibody dominated response
e. A Th2 response is characterized by a high level of IFN-gamma secretion

Answer 32

b. A Th1 response is characterized by a high level of IFN-gamma secretion

Question 33

As part of the adaptive immune response to a virus infection, IgG antibodies can interact with:
I. Molecular patterns that are present on most viruses
II. NK cells and viral glycoproteins on infected cell to induce lysis of the infected cell
III. 3 dimensional shape of the viral proteins
IV. MHC class I and II

a. All of the above
b. I and II
c. II and IV
d. II and III
e. None of the Above

Answer 33

d. II and III

Question 34

Which molecule is expressed on Th cells?
a. Receptor for complement
b. T cell receptor that binds to MHC I
c. CD4 molecule
d. CD8 molecule
e. None of the above

Answer 34

c. CD4 molecule

Question 35

The following are generally true in regard to the role of antibodies in a virus infection.
I. Antibodies secreted from immature B lymphocytes react to a specific linear AA sequences or conformational structures on virions.
II. In viral infections the only role of antibodies is lysis of infected cells.
III. Antibody response plays a major role in preventing host from viral
infection
IV. Antibody bound to the virion can “neutralize” the virus by preventing the
virion from interacting its cellular receptor and establishing infection
V. Antibody bound to the virion can “opsonize” the virus making it more
susceptible to phagocytosis and degradation by a macrophage.

a. I, II and III
b. II, III and IV
c. II, IV, and V
d. III, IV and V
e. I, III and IV

Answer 35

d. III, IV and V

Question 36

Choose the correct statement
a. In an outbreak of a common viral disease, everyone exposed to the same virus
on the same occasion will have similarly severe disease.
b. The virus titer in primary viremia is always higher than in secondary viremia.
c. Rhinovirus is more stable in lung than in nose because the temperature in lung is more close to 37 °C
d. In certain viral infections such as dengue virus, virus-specific antibodies may enhance the spread of virus into immune cells and make the disease worth upon second exposure of the virus
e. Transmission of poliovirus is equally efficient by fecal-oral and venereal routes because the receptors for poliovirus are found in all tissues.

Answer 36

d. In certain viral infections such as dengue virus, virus-specific antibodies may enhance the spread of virus into immune cells and make the disease worth upon second exposure of the virus

Question 37

How does type 1 IFNs limit viral replication?
I. It induces synthesis of 2’5-oligoadenylate synthetase which subsequently activates endonuclease to specifically degrade viral mRNA
II. It blocks interaction of protein kinase and eIF2 to inhibit all protein synthesis in the cell.
III. It promotes cleavage of cellular eIF4G protein to inhibit cellular protein synthesis to inhibit all protein synthesis in the cell.
IV. It induces the protein kinase that phosphorylates eIF-2 to inhibit all protein synthesis in the cell.

a. I and II
b. I and III
c. I and IV
d. I, II and III
e. I, III and IV

Answer 37

c. I and IV

Question 38

From the following, choose the correct statement(s) about common viral infections at
the level of animal population:

I. The majority of animals exposed either are not infected or develop subclinical disease after infection
II. In general, virus that only transmitted vertically will lead to more infections, more rapidly than a virus is transmitted only horizontally
III. A good strategy for virus survival is to kill all susceptible hosts.
IV. The majority of animals exposed are infected and develop classic disease

a. I
b. I,II
c. I, II, III
d. IV
e. II, IV

Answer 38

a. I

Question 39

Which virus is transmitted to humans through needles (transfusion, accidental needle sticks an occupational hazard of health care workers, drug abuse)?
a. Poliovirus
b. Rotavirus
c. Hepatitis B Virus
d. Herpes Simplex Virus type 2
e. Human Papillomavirus

Answer 39

c. Hepatitis B Virus

Question 40

Which statement about measles virus infection is not true?
a. The most recent measles outbreaks in the U.S. mainly occurs in communities with low measles vaccine coverage
b. Virus spreads to many organs after secondary viremia
c. The vaccine for measles virus is very effective. The introduction of the vaccine significantly lowered the incidence of measles virus infection in the United States.
d. The reason for the outbreak of measles in early 1990s involving college students was the failure of vaccine to elicit protective response toward the circulating measles virus strain.
e. All of above are not true

Answer 40

d. The reason for the outbreak of measles in early 1990s involving college students was the failure of vaccine to elicit protective response toward the circulating measles virus strain.

Question 41

If you are a researcher who is working to develop a measles animal model. Which route of measles inoculation would you use to mimic natural measles transmission in humans?
a. Intra-conjunctival and intranasal inoculation
b. Intracerebral challenge inoculation
c. Intravenous challenge inoculation
d. Intravaginal challenge inoculation
e. Intrarectal challenge inoculation

Answer 41

a. Intra-conjunctival and intranasal inoculation

Question 42

To determine the distribution of measles viruses in tissues, you use a green fluoresce protein expressing measles virus plan to visualize the tissue tropism of measles virus. Which tissues do you expect to see glowing green signals in a measles virus infected monkey?
a. Spleen
b. Skin
c. Lymph nodes
d. Buccal mucosa
e. All of the above

Answer 42

e. All of the above

Question 43

43. In measles virus infection, the virus shedding starts
    a. Before skin rashes developed
    b. After skin rashes developed
    c. At the time of skin rashes developed
    d. After measles virus specific antibodies produced
    e. In a random order

Answer 43

a. Before skin rashes developed

Question 44

Which is not a possible outcome of measles infection in human?
a. Immunosuppression
b. Subacute sclerosing panencephalitis (SSPE)
c. Developed long-lasting measles memory immune response for at least 65 years
d. Develop memory T cell responses
e. All of the above outcomes are possible

Answer 44

e. All of the above outcomes are possible

Question 45

Which statement is not true about innate immunity?
a. Transfection of synthetic ssRNA into dendritic cells will lead to high level
production of IFN-g
b. NK cells kill virus-infected cells with decreased MHC I expression because the NK cells killing is no longer inhibited by their receptor for MHC I molecules.
c. Natural antibodies react with various types of molecules with low-affinity
d. Macrophages can present antigens to T cells to elicit adaptive anti-viral immune responses.
e. In tissues, macrophages have longer lifespan than neutrophils (Neutrophils survive for less than 1 day in tissues)

Answer 45

a. Transfection of synthetic ssRNA into dendritic cells will lead to high level production of IFN-g

Question 46

Viruses can evade detection by the host immune system by:
I. Encoding proteins that directly block induction of antiviral innate immune response genes
II. Encoding proteins that induce apoptosis
III. Encoding proteins that inhibit inflammation
IV. limiting NK cell killing of infected cells by reducing expression of MHC class I

a. I and II
b. I, II and III
c. I and III
d. I and IV
e. All of the Above

Answer 46

c. I and III

Question 47

Which statements are true?
I. Anti-viral cytotoxic CD8+ T cells recognize specific viral peptides presented in MHC class II on the surface of antigen presenting cells
II. Anti-viral cytotoxic CD8+ T cells release anti-viral cytokines such as IFN-g
III. Anti-viral cytotoxic CD8+ T cells recognize a specific viral peptide associated with MHC I molecules on the cell surface via their TCR
IV. Anti-viral cytotoxic CD8+ T cells recognize the Fc receptor of antibody bound
to the antigen on the target cell and direct cell killing
V. Anti-viral cytotoxic CD8+ T cells kill target cells by producing perforin to make
holes in cell membranes and by introducing enzymes into the target cells

a. I, II, and III
b. I, II, and IV
c. II, III, and V
d. II, IV and V
e. I, IV and V

Answer 47

c. II, III, and V

Question 48

In general, what is the sequence of events in an immune response to an acute virus infection
I. Antibody production
II. NK cell activation and expansion
III. Cytotoxic T cell response
IV. IFN-alpha/beta production

a. I–>II–>III–>IV
b. IV–>III–>II–>I
c. II–>III–>IV–>I
d. III–>IV–>II–>I
e. IV–>II–>III–>I

Answer 48

e. IV–>II–>III–>I

Question 49

Which arm of the antiviral immune response is most critical for preventing viral infections?
a. NK cell activation by interferons
b. Antiviral T cell responses
c. Complement mediated antiviral activities
d. Antiviral antibody responses
e. Innate antiviral immune responses

Answer 49

d. Antiviral antibody responses

Question 50

Which statement is not true about how chronic viral infections evade the immune system?
a. Herpes Simplex Virus restricts its viral gene expression during latency in neurons to ensure minimal stimulation of host immune response
b. Herpes Simplex Virus encodes protein that inhibit the transport of peptide into endoplasmic reticulum and thus interfere with MHC class I antigen presentation and anti-viral CD8+ T cell responses
c. Human Immunodeficiency Virus encodes protein that reduces transcription of MHC I gene to evade anti-viral CD8+ T cell responses
d. Human Immunodeficiency Virus mutates rapidly and produce antigenic variants to escape from T cell recognition
e. All of above are true

Answer 50

e. All of above are true