Flashcards in levinson questions Deck (52)
159: viruses enter cells by adsorbing to specific sites on the outer membrane of cells. each of the following statements regarding this event is correct except:
A: the interaction determines the specific target organs for infection
B: the interaction determines whether the purified genome of a virus infection
C: in interaction can be prevented by neutralizing antibody
D: if the sites are occupied, interfere with virus infection occurs
160: many viruses mature by budding through the outer membrane of the host cell. each of the following statements regarding these viruses is correct except:
A: some of these viruses cause multinucleated giant cell formation
B: some new viral antigens appear on the surface of the host cell
C: some of these viruses contain host cell lipids
D: some of these viruses do not have an envelope
161: biochemical analysis of a virus reveals the genome to be composed of eight unequally sized pieces of single-stranded RNA, each of which is complementary to viral mRNA in infected cells. which one of the following statements is unlikely to be correct?
A: different proteins are encoded by each segment of the viral genome
B: the virus particle contains a virus-encoded enzyme that can copy the genome into its complement
C: purified RNA extracted from the virus particle is infectious
D: the virus can acquire new antigens via reassortment of its RNA segments
162: latency is an outcome particuarly characteristic of which one of the following virus groups?
D: influenza viruses
163: each of the following statements concerning viral serotypes is correct except:
A: in naked nucleocapsid viruses, the serotype is usually determined by the outer capsid proteins
B: in enveloped viruses, the serotype is usually determined by the outer envelope proteins, especially the spike proteins
C: some viruses have multiple serotypes
D: some viruses have an RNA polymerase that determines serotype
164: the ability of a virus to produce disease can result from a variety of mechanisms. which one of the following is least likely?
A: cytopathic effect in infected cells
B: malignant transformation of infected cells
C: immune response to virus-induced antigens on the surface of infected cells
D: production of an exotoxin that activates adenylate cyclase
165: which one of the following forms of immunity to viruses would be least likely to be lifelong?
A: passive immunity
B: passive-active immunity
C: active immunity
D: cell-mediated immunity
170: a stock of virus particles has been found by electron microscopy to contain 10^8 particles/mL, but a plaque assay reveals only 10^5 plaque-forming units/mL. the best interpretation of these results is that:
A: only one particle in 1000 is infectious
B: a nonpermissive cell line was used for the plaque assay
C: several kinds of viruses were present in stock
D: the virus is a temperature-sensitive mutant
172: each of the following statements concerning viral surface proteins is correct except:
A: they elicit antibody that neutralizes infectivity of the virus
B: the determine the species specificity of the virus-cell interaction
C: they participate in active transport of nutrients across the viral envelope membrane
D: they protect the genetic material against nucleases
block 1, 2: your summer research project is to study the viruses that cause upper respiratory tract infections. you have isolated a virus from a patient's throat and find that its genome is RNA. futhermore, you find that the genome is the complement of viral mRNA within the infected cell. Of the following, which one is the MOST appropriate conclusion you could draw?
A: the virion contains a polymerase
B: the purified genome RNA is infectious
C: the genome RNA is segmented
D: a single-stranded DNA is synthesized during replication
E: the genome RNA encodes a precursor polypeptide that must be cleaved by a protease
167: you have isolated a virus from the stool of a patient with diarrhea and shown that its genome is composed of multiple pieces of double-stranded RNA. which one of the following is least likely to be true?
A: each piece of RNA encodes a different protein
B: the virus encodes an RNA-directed RNA polymerase
C: the virion contains an RNA polymerase
D: the genome integrates into the host chromosome
173: each of the following statements concerning viral vaccines is correct except:
A: in live, attenuated vaccines, the virus has lost its ability to cause disease but has retained its ability to induce neutralizing antibody
B: in live, attenuated vaccines, the possibility of reversion to virulence is of concern
C: with inactivated vaccines, IgA mucosal immunity is usually induced
D: with inactivated vaccines, protective immunity is due mainly to the production of IgG
174: the major barrier to the control of rhinovirus upper respiratory infections by immunization is:
A: the poor local and systemic immune response to these viruses
B: the large number of serotypes of the rhinoviruses
C: the side effects of the vaccine
D: the inability to grow the viruses in cell cultures
191: each of the following statements about both poliovirus and rhinoviruses is correct except:
A: they are noneveloped RNA viruses
B: they have multiple antigenic types
C: their virons contain an RNA polymerase
D: they do not integrate their genome into host cell DNA
select the one lettered option that is most closely associated with the numbered items.
A: DNA enveloped virus
B: DNA non-enveloped virus
C: RNA enveloped virus
D: RNA non-enveloped virus
214: each of the following statements regarding poliovirus and its vaccine is correct except:
A: poliovirus is transmitted by the fecal-oral route
B: pathogenesis by poliovirus primarily involves the death of sensory neurons
C: the live, attenuated vaccine contains all three serotypes of poliovirus
D: an unimmunized adult traveling to countries where there is a known risk of being infected with poliovirus should receive the inactivated virus
215: which one of the following strategies is most likely to induce lasting intestinal mucosal immunity to poliovirus?
A: paranteral (intramuscular) immunization with inactivated vaccine
B: oral administration of poliovirus immune globulin
C: parenteral immunization with live vaccine
D: oral immunization with live vaccine
245: which of the following conditions is least likely to be caused by adenoviruses?
260: each of the following statements concerning rhinoviruses is correct except
A: rhinoviruses are picornaviruses (ie small, noneneveloped viruses with an RNA genome)
B: rhinoviruses are an important cause of lower respiratory tract infections, especially in patients with chronic obstructive pulmonary disease
C: rhinoviruses do not infect the GI tract because they are inactivated by the acid pH in the stomach
D: there is no vaccine against rhinoviruses because there are too many antigenic types
265: each of the following statements concerning adenovirus is correct except:
A: adenoviruses are composed of a double-stranded DNA genome and a capsid without an envelope
B: adenoviruses cause both sore throat and pneumonia
C: adenoviruses have only one serologic type
D: adenoviruses are implicated as a cause of tumors in animals but not humans
268: each of the following statements concerning rhinoviruses is correct except:
A: rhinoviruses are the most common cause of the common cold
B: rhinoviruses grow better at 33 C than at 37 C, hence they tend to cause disease in the upper respiratory tract rather than the lower respiratory tract
C: rhinoviruses are members of the picornaviruses family and hence resemble poliovirus in their structure and replication
D: the immunity provided by the rhinovirus vaccine is excellent because there is only one serotype
269: which one of the following statements concerning poliovirus infection is correct?
A: congenital infection of the fetus is an important complication
B: the virus replicates extensively in the GI tract
C: A skin test is available to determine prior exposure to the virus
D: amantadine is an effective preventive agent
block two, 12: the two most common types of viral vaccines are killed vaccines adn live, attenuated vaccines. Regarding these vaccines, which one of the following statements is the most accurate?
A: killed vaccines induce a longer-lasting response than do live, attenuated vaccines
B: killed vaccines are no longer used in this country because they do not induce secretory IgA
C: killed vaccines induce a broader range of immune responses than do live, attenuated vaccines
D: killed vaccines are safer to give to immunocompromised patients than are live, attenuated vaccines
block two, 29: regarding poliovirus, which one of the following is most accurate?
A: poliovirus remains latent within sensory ganglia, and reactivation occurs primarily in immunocompromised patients
B: when the live, attenuated virus in the oral vaccine replicates, revertant mutants can occur that can cause paralytic polio
C: the widespread use of the killed vaccine in the countries of North and South America has led to the virtual elimination of paralytic polio in these areas
D: the current recommemdation is to give the live, attenuated vaccine for the first 3 immunizations to prevent the child from acting as a reservoir, followed by boosters using the killed vaccine
clinical cases 9: a 20-year-old man has a severe headache and vomiting that began yesterday. he is now confused. on examination, his temperature si 39 degres C and his neck is stiff. Spinal fluid reveals no bacteria on Gram stain, 25 lymphs, normal protein, and normal glucose. culture of the spinal fluid on blood agar shows no bacterial colones. Diagnosis?
viral meningitis, which is most often caused by coxsackie virus. can isolate the virus from spinal fluid.
clinical cases 11: a 3-month-old girl has watery, nonbloody diarrhea. stool culture reveals only normal enteric flora. Diagnosis?
think rotavirus, the most common cause of diarrhea in infants. the elisa test for rotavirus antigen in the stool is positive, which confirms the diagnosis
166: which one of the following statements concerning interferons is least accurate?
A; interferons are proteins that influence host defenses in many ways, one of which is the induction of antiviral state
B: interferons are synthesized only by virus-infected cells
C: interferons inhibit a broad range of viruses, not just the virus that induced the interferon
D: interferons induce the synthesis of a ribonuclease that degrades viral mRNA
175: the feature of the influenza virus genome that contributes most to the antigenic variation of the virus is:
A: a high G+C content, which augments binding to nucleoproteins
B: inverted repeat regions, which create "sticky ends"
C: segmented nucleic acid
D: unique methylated bases
177: each of the following statements concerning interferon is correct except:
A: interferon inhibits the growth of both DNA and RNA
B: interferon is induced by double-stranded RNA
C: interferon made by cells of one species acts more effectively in the cells of that species than in the cells of other species
D: interferon acts by preventing viruses from entering the cell