Deck 48: Laboratory Methods in Basic Virology

Question 1

The term antigenic drift refers to

A)mutation during genome replication resulting in minor antigenic change and relatively mild influenza outbreaks every 1 to 3 years.
B)reassortment of the segmented viral genome during co-infection in nonhuman animals, resulting in major antigenic change and periodic worldwide outbreaks.
C)what happens when human virus infects a cell at the same time as an animal influenza virus.
D)All of the above are correct.

Answer 1

A
The term antigenic drift refers to mutation during viral genome replication. It results in minor antigenic change and relatively mild influenza outbreaks every 1 to 3 years.

Question 2

Viral capsids are composed of many individual subunits called

A)capsomeres.
B)virions.
C)capsules.
D)nucleocapsids.

Answer 2

A
Viruses are composed of a nucleic acid genome surrounded by a protein coat called a capsid. Together the genome and capsid are referred to as the nucleocapsid. Viral capsids are composed of many individual subunits called capsomeres. Capsomeres assemble into an icosahedral or irregular-shaped capsid. Irregular-shaped capsids usually assume a helical form. Icosahedral-shaped capsids are cubical with 20 flat sides, whereas helical capsids are spiral shaped. Some of the larger viruses have a lipid-containing envelope that surrounds the capsid. In addition, many viruses have glycoprotein spikes that extend from the surface of the virus, acting as attachment projections or as enzymes. The entire virus, including nucleic acid, capsid, envelope, and glycoprotein spikes, is called the virion, or viral particle.

Question 3

Tzanck smears are prepared by

A)pressing a microscope slide against the base of an ulcer to collect infected and noninfected cells.
B)aspirating a small "drop" of vesicle fluid and smearing this onto a microscope slide.
C)removing vesicle fluid by dabbing with a sterile gauze and then smearing this onto a microscope slide.
D)collecting fecal sample with a swab and rolling the swab onto a microscope slide.

Answer 3

A
Tzanck smears from cutaneous vesicles are prepared by carefully unroofing the vesicle. If a tuberculin syringe is used, the small "drop" of vesicle fluid should be aspirated first, to be used in case viral or bacterial culture is needed. Flush needle with viral transport medium and add rinse to viral transport tube. With the roof of the vesicle folded back, carefully remove excess fluid by dabbing with a sterile gauze. Press a clean glass microscope slide against the base of the ulcer. Lift, move slide slightly, and press again. Cells from the base of the ulcer will stick to the slide, making an "impression smear" of infected and noninfected cells.

Question 4

Which viruses are unique because of their ability to alter antigenic composition, thus reinfecting "nonimmune" susceptible hosts?

A)Coronaviruses
B)Herpes viruses
C)Influenzae viruses
D)Filoviruses

Question 5

The term syncytia is used to describe

A)the ability of virions to synchronize penetration and release from host cells.
B)multinucleated cells formed from the fusion between cells penetrated by virions and other host cells nearby.
C)the attraction of viral particles to specific tissue types within the host.
D)the attachment of viral particles to certain transmitting molecules like blood cells to enable infectious spreading of the virus.

Question 6

In general, specimens collected for detection of virus should be

A)placed in ice and transported to the laboratory at once.
B)frozen until processing occurs.
C)processed within 1 to 2 days of collection.
D)inoculated into cell culture at the bedside.

Question 7

The specimen of choice for detecting rotavirus is a

A)throat swab.
B)urine sample.
C)bronchoalveolar wash.
D)feces sample.

Question 8

The specimen of choice for detecting respiratory syncytial virus is a

A)throat swab.
B)nasopharyngeal aspirate.
C)bronchoalveolar wash.
D)lung biopsy.

Question 9

The term viral tropism refers to

A)the attraction of viral particles to specific tissue types within the host.
B)the attachment of viral particles to certain transmitting molecules like blood cells to enable infectious spreading of the virus.
C)the recognition and attachment of the virus to a limited number of host cell types, allowing infection of some tissues but not others.
D)the attraction of viral particles to specific host types.

Question 10

This virus causes a benign disease with rash and fever unless it occurs in a pregnant patient, where it can infect the developing fetus and result in multiple congenital anomalies.

A)Alpha virus
B)Rabies virus
C)Poxvirus
D)Rubella virus

Question 11

Detection of virus in cell culture by hemadsorption

A)is useful in detecting viruses that release via cell lysis.
B)involves virally encoded glycoprotein hemagglutinins.
C)involves adsorption of red blood cells to the outer membranes of uninfected cells but not to infected cells.
D)has been used effectively in patients infected with arboviruses.

Question 12

The protein coat that surrounds the nucleic acid of a virion is called a

A)capsomere.
B)capsid.
C)capsule.
D)nucleocapsid.

Question 13

The most pathogenic of the hemorrhagic fever viruses, this group of long filamentous viruses include Marburg and Ebola.

A)Coronaviruses
B)Bunyaviruses
C)Caliciviruses
D)Filoviruses

Question 14

Together, the genome and protein coat of a virion is called a

A)capsomere.
B)capsid.
C)capsule.
D)nucleocapsid.

Question 15

Varicella-zoster virus, Epstein-Barr virus, and cytomegalovirus are included in this widely disseminated group of viruses.

A)Coronaviruses
B)Herpes viruses
C)Caliciviruses
D)Filoviruses

Question 16

Viruses that cause arbovirus diseases such as yellow fever, dengue, and West Nile, as well as Japanese and St.Louis encephalitis viruses, belong to what group of viruses?

A)Flaviviruses
B)Bunyaviruses
C)Caliciviruses
D)Filoviruses

Question 17

A large, diverse group of viruses, most of which are transmitted by mosquitoes, which includes the deadly Hantavirus is called

A)coronaviruses.
B)bunyaviruses.
C)caliciviruses.
D)filoviruses.

Question 18

This rhabdovirus is present in saliva and is transmitted by animal bite; it invades the peripheral and central nervous systems.

A)Rubella virus
B)Alpha virus
C)Rabies virus
D)Poxvirus

Question 19

During viral assembly, viral envelopes are acquired

A)by production of envelope constituents by host cellular DNA.
B)as the virion buds from a host cell membrane.
C)through replication of viral nucleic acid.
D)as host cell lysis produces many membrane fragments.

Question 20

The specimen of choice for detecting cytomegalovirus is a

A)sample of lung tissue.
B)urine sample.
C)bronchoalveolar wash.
D)pleural fluid.

Question 21

Concerning the two immunofluorescence methods of diagnosing viral infection, which statement is correct?

A)Direct immunofluorescence is generally more rapid and specific than indirect immunofluorescence.
B)Indirect immunofluorescence is best suited to situations in which large quantities of virus are suspected.
C)Signal amplification of the direct test decreases specificity by increasing nonspecific background fluorescence.
D)High-quality monoclonal antibodies improve the sensitivity and specificity of the direct test.
E)All of the above are correct.

Question 22

Calcium alginate swabs are not acceptable for the detection of

A)herpes simplex virus.
B)enterovirus.
C)rabies virus.
D)rotavirus.

Question 23

Lip and genital specimens are most likely collected for the detection of

A)varicella zoster virus.
B)herpes simplex virus.
C)cytomegalovirus.
D)rotavirus.

Question 24

A drawback with ELISAs is

A)that they are not well suited for high-volume testing or for when rapid results are needed.
B)the inability of the technologist to make specimen quality evaluations from assessment of the number of cells present.
C)that they cannot be performed by those with minimum training.
D)that they do not include vials of positive and negative sera for quality monitoring of test procedures.

Question 25

Influenza A and B viruses can be detected in clinical specimens using

A)cell culture.
B)shell vial assay.
C)enzyme immunoassay.
D)FA staining methods.
E)All of the above are correct.

Question 26

Concerning the two immunofluorescence methods of diagnosing viral infection, which statement is correct?

A)Direct immunofluorescence is generally more rapid and specific than indirect immunofluorescence.
B)Direct immunofluorescence is best suited to situations in which large quantities of virus are suspected.
C)Signal amplification of the indirect test decreases specificity by increasing nonspecific background fluorescence.
D)Indirect immunofluorescence should be used when lower quantities of virus are suspected, such as for detection of respiratory viruses in specimens from adult patients.
E)All of the above are correct.

Question 27

Direct immunofluorescent FA testing involves

A)unlabeled antiviral antibody and a labeled antiglobulin.
B)labeled antiviral antibody and virus.
C)labeled antiviral antibody and a labeled antiglobulin.
D)unlabeled antiviral antibody and virus.

Question 28

Measures to enhance detection of virus in viral cultures include

A)centrifugation of specimen and using supernatant to inoculate medium.
B)vortexing with sterile glass beads.
C)filtering specimen using a disposable 0.22-mm filter.
D)All of the above are correct.

Question 29

Which immunoglobulin may form insoluble aggregates upon thawing, giving a false-negative result with previously frozen serum samples?

A)IgG
B)IgE
C)IgM
D)IgA
E)All of the above are correct.

Question 30

During the fall, winter, and spring, stool specimens from infants should most likely be tested for

A)varicella zoster virus.
B)herpes simplex virus.
C)cytomegalovirus.
D)rotavirus.

Question 31

To avoid transplacental infection followed by congenital defects, which series of serologic tests is often performed during pregnancy?

A)Toxoplasma, rubella, cytomegalovirus, and herpes simplex virus
B)Toxoplasma, rubella, varicella-zoster virus, and herpes simplex virus
C)Rubella, cytomegalovirus, varicella-zoster virus, and herpes simplex virus
D)Rubella, cytomegalovirus, herpes simplex virus, and papilloma virus

Question 32

The test of choice for use with CSF to diagnose aseptic meningitis caused by enterovirus is

A)cell culture.
B)PCR.
C)antigenemia immunoassay.
D)shell vial assay.

Question 33

Viral transport media used to transport specimens

A)contain protein, such as serum, albumin, or gelatin.
B)contain antimicrobials.
C)include Stuart's medium, Amie's medium, Leibovitz-Emory medium, Hanks balanced salt solution (HBSS), and Eagles tissue culture medium.
D)All of the above are correct.

Question 34

If a 2- to 3-day delay in processing of a specimen for viral culture is unavoidable, the specimen should be

A)refrigerated until processing occurs.
B)frozen until processing occurs.
C)inoculated into cell culture at the bedside.
D)allowed to sit at room temperature or warmer, such as in an incubator.

Question 35

Indirect immunofluorescent FA testing involves

A)unlabeled antiviral antibody and a labeled antiglobulin.
B)labeled antiviral antibody and virus.
C)labeled antiviral antibody and a labeled antiglobulin.
D)unlabeled antiviral antibody and virus.

Question 36

Measures to avoid bacterial contamination in viral cultures include

A)centrifugation of specimen.
B)vortexing with sterile glass beads.
C)filtering specimen using a disposable 2-mm filter.
D)All of the above are correct.

Question 37

Cytomegalovirus can be detected in clinical specimens using

A)cell culture.
B)shell vial assay.
C)antigenemia immunoassay.
D)All of the above are correct.

Question 38

Long-term storage of a specimen for viral culture for more than 6 days should include

A)holding specimen at 4°? C.
B)holding specimen at -70° C.
C)diluting or emulsifying in viral transport medium and holding at -70° C.
D)holding specimen at 20° C.

Question 39

Membrane ELISA tests in clinical virology

A)are well suited for high-volume testing and where rapid results are not needed.
B)cannot be performed by those with minimum training.
C)include vials of positive and negative sera for quality monitoring of test procedures.
D)involve a handheld reaction chamber with a cellulose-like membrane, reagents to apply to the membrane, and a chromogenic reaction.
E)All of the above are correct.

Question 40

Urine specimens are most likely collected for the detection of

A)varicella zoster virus.
B)herpes simplex virus.
C)cytomegalovirus.
D)rotavirus.

Question 41

Advantage of the shell vial culture over conventional cell culture for virus is that

A)virus is detected more quickly using the shell vial technique.
B)inoculated shell vials can be stored for up to 9 weeks before use for viral culture.
C)CPE is more easily interpreted.
D)centrifugation is not necessary for optimal detection.
E)All of the above are correct.

Question 42

The term primary cell line refers to

A)those lines that cannot be subcultured more than once or twice to avoid decreased receptivity to viral infection.
B)those lines that remain virus-sensitive through not more than 10 subcultures.
C)those lines that remain virus-sensitive through 20 to 50 subcultures.
D)those lines that can be subcultured and remain sensitive to virus infections indefinitely.

Question 43

To diagnose active viral disease with serologic methods, the specimen of choice would be

A)an acute-phase serum specimen collected at the onset of infection.
B)acute and convalescent sera.
C)a single post-acute serum, collected between acute and convalescent times.
D)All of the above are correct.

Question 44

The term blind passage in virology

A)refers to a technique that is less frequently used today because of the added time and expense involved.
B)describes a technique that is used to detect viruses that may not produce cytopathic effects (CPE) in the initial culture tube but will when the "beefed-up" inoculum is passed to a second tube.
C)describes a technique that can be used to dilute toxicity and thus prevent ambiguous CPE caused by toxicity.
D)describes a technique that is performed by scraping the monolayer off the sides of the tube and inoculating 0.25 mL of the resulting suspension into a new cell culture.
E)All of the above are correct.

Question 45

The major form of control of viral diseases has been

A)vaccination.
B)immune prophylaxis.
C)antiviral chemotherapeutic agents.
D)eradication.

Question 46

Successful cultivation of virus in the laboratory includes

A)incubation of the culture immediately at 30° C.
B)allowing the virus to adsorb to the cell monolayer for at least 2 to 4 hours.
C)removing the inoculum and culture medium after the initial adsorption period and replacing it with fresh maintenance medium.
D)adding new growth medium periodically.
E)All of the above are correct.

Question 47

Immune status tests are used to

A)identify patients who have been infected by a virus in the past.
B)identify patients who have been vaccinated for a virus in the past.
C)identify the presence of lifelong immunity to reinfection of a virus.
D)All of the above are correct.

Question 48

A less demanding, easily automated technique for batch testing for the detection of antiviral antibody that can be used to detect IgM-specific antibodies free of common interfering factors is the

A)complement fixation (CF).
B)enzyme-linked immunosorbent assay (ELISA).
C)indirect immunofluorescence (IF).
D)anticomplement immunofluorescence (ACIF).

Question 49

Viruses can be stored by

A)freezing at 20°C.
B)freezing in liquid nitrogen.
C)inoculating to continuous cell lines such as HEp-2.
D)refrigeration at 2° to 6°C.

Question 50

The difference between maintenance medium and growth medium used in viral cell cultures is that

A)maintenance medium includes antimicrobials to prevent bacterial contamination.
B)growth medium is made from Eagle's minimum essential medium (EMEM).
C)maintenance medium contains Earle's balanced salt solution.
D)maintenance medium contains less serum than growth medium.

Question 51

When testing for antiviral IgM antibody, false-negative results may occur when

A)rheumatoid factor combines with homologous or virus-specific IgG present in the patient specimen.
B)high levels of strongly binding homologous IgG antibodies prevent binding of IgM molecules.
C)antibody-Fc receptors occur in cells infected with virus.
D)All of the above are correct.