Answers to Virology MCQ Paper 2

Answers to virology MCQ Paper 2

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Answers to Multiple Choice Questions - Paper 2

Instructions for candidates

The examination consists consists of 30 multiple choice questions, each divided into 5 different parts. Eac h part c ontains a statement which could be true or false. Eac h question will have at least one pa rt which is true. For each part, you should indicate whether you think it is true (T), false (F), or don’t know (DN). You must fill in in the relevant square with a black pen. One mark will be given for each correct answer and one mark deducted for e ach incorrect answer. You will not be marked for those questions for which you have indicated "don’t know".

1. Viruses may contain

True

DNA

True

RNA

True

Glycoprotein

True

Enzymes

False

Cell wall

Comments Comments

Viruses Viruses may may contain either DNA, DNA, or RNA. RNA. They may may contain enzymes such as polymerases, polymerases, and have glycoproteins glycoproteins in their envelope

2. Viruses are

True

Obligate in intracellular pa parasites

False

May divide by binary fission

False

Have their own metabolism

True

May contain enzymes for replication

True

May have an envelope

Comments Comments

Unlike Unlike bacteria, viruses viruses do not have their own metabolism metabolism and do do not divide divide by binary fission. fission. They They are intracellular intracellular parasites and may c ontain enzymes for their replication. Some viruses possess possess a lipid envelope.

3. The following statements are true

Fals alse

All virus ruses are are sen senssitive tive to anti antivi vira rall agen agents ts

True

Virus Virus infected cells may be transformed.

True

Viruses may have a lipid envelope enve lope

True

Viruses Viruses may produce cytopathic changes in cell culture

True

Some Some viruses are destroyed by lipid lipid solvents

Comments Comments

To date, only only a few viruses viruses can be treated by antiviral agents. Some Some viruses viruses such as oncornaviruses can transform transform cells. cells. Some Some may have a lipid lipid envelope which may be destroyed by lipid solvents. solvents.

4. The following are direct dete ction methods

True

Detection of rotavirus antigen in faecal specimens

False

Single radia l haemolysis (SRH)

False

CMV DEAFF test

True

Electron microscopy microscopy

True

P olymerase chain reaction

Comments Comments

SRH SRH is a serological serological assay, and the CMV DEAFF test is a rapid rapid culture test. The The rest are used to detect virus particles, antigens, antigens, and nucleic acid directly from a specimen

5. The following methods may be used for serological diagnosis



True

Complement-fixa tion tests (CFT)

False

Polymerase chain reaction (PCR)

True

Single Single Radial Haemolysis (SRH)

False

CMV DEAFF test

True

Western blot

Comments

PCR detects viral genomes directly. The The CMV DEAFF test is a rapid culture culture assay. Western Western blot is is mainly mainly used as a serological serological test

6. A serological diagnosis of a primary viral infection may be made

False

Detection of viral-specific viral-specific IgA

False

Detection of viral-specific viral-specific IgD

False

Detection of viral-specific viral-specific IgE

True

Detection of viral-specific viral-specific IgM

True

Seroconversion

Comments Comments

A diagnosi diagnosiss of a primary primary viral infection infection may be made by the detection of IgM IgM and/or seroconv seroconversi ersion. on.

7. The following are e xamples of viral genome detection (molecular methods) methods)

True

Southern blot

False

Western blot

False

RIBA (Recombinant (Reco mbinant immunoblot assay)

True

Branched DNA

True

Polymerase chain reaction (PCR)

Comments Comments

Southern blot, blot, branched DNA, DNA, and PCR are viral genom genomee detection methods. methods. Western Western blot and RIBA RIBA are serologi serological cal assays assays

8. The following statements are true

False

For cytomegalovirus cytomegalovirus (CMV), (CMV), the cytopathic (CPE) effect usually usually appears within 24-48 hours

True

For some viruses, the CPE is so characteristic that so further identification is required.

True

Paramyxovirus causes syncytia formation in cell culture

False

A given given virus always produce identical CPE in different cell cultures

True

Immmunofluroescence Immmunofluroescence may be used to identify a virus in cell culture

Comments Comments

It takes 1-3 weeks for CMV-specific CMV-specific CPE CPE to appear. For some some viruses such as herpes simplex, simplex, the CPE is so characteristic that so further identification identification is required.

9. Poliovirus can be typed by

False

Single Single radial haemolysis (SRH)

False

Haemagglutination Haemagglutinat ion inhibition test (HAI)

False

DEAFF test

True

Neutralization Neutralization test

True

Hybridization Hybridization with specific nucleic acid probes

Comments Comments

Polioviruses Polioviruses can be typed by by neutralization neutralization tests and hybridization hybridization with specific nucleic acid probes. SRH SRH and HAI are not used. The DEAFF test is used for the isolation of CMV



10. Immunofluorescence Immunofluorescence techniques can be used to detect the following directly from the speci men.

True

Chlamydia

True

CMV

True

Respiratory Respirato ry Syncytial Virus (RSV)

True

Influenza virus

True

Rabies virus

Comm omments ents

All the the abo above ve

11. The following statements are true for the haemagglutination-inhibition haemagglutination-inhibition (HAI) test.

False

Not a quantitative test

True

Treatment of patient serum is necessary to remove non-specific non-specific inhibitors inhibitors

True

Animal blood is nece ssary

True

Usually more specific than complement fixation tests (CFT)

True

May be used for the diagnosis diagnosis of rubella infection

Comments Comments

HAI is is a quantitative test. It is is widely widely used in in rubella rubella serology. serology. It is usually more specific specific than CFT. CFT. Treatment of patient patient serum is necessary to remove non-specific inhibitors. inhibitors.

12. Regarding cell culture

False

Viruses can only be culture d using cell lines

False

The presence of cytopathic effect is the only way to detect a virus

True

The neutralization test is the mainstay mainstay of identification of a poliovirus poliovirus isolate isolate

False

The haemagglutination haemagglutinat ion inhibition test is the mainstay of identifica tion of a respiratory respirat ory syncytial syncytia l virus (RSV) isolate

False

Whole blood is the specimen of choice for many common viruses

Comments Comments

Viruses Viruses may may also be cultured cultured in eggs eggs and animals. animals. The The presence of virus may be detected by CPE as well as haemadsoption, haemadsoption, and presence of viral particles and antigen.

13. A standard Polymerase Chain Reaction (PCR) consists of

False

Denaturation, annealing, annealing, and ligation ligation steps

True

Denaturation, annealing, and extension steps

True

dNTPs

True

Mg++ ions

True

Taq polymerase

Comments Comments

Denaturation Denaturation,, annealing, annealing, and ligati ligation on steps occur in LCR. LCR. PCR consists consists of Denaturation, Denaturation, annealing annealing,, and extension steps. steps. It requires dNTP, Mg++, ta q polymerase, a nd t arget-specific arget-specific oligonucleotide oligonucleotide primers.

14. Modification of a standard PCR include

True

Nested PCR

False

branched DNA (bDNA)

True

RT-PCR (Reverse transcription PCR)



True

Quantitative PCR

False

3SR (Isothermal (Isother mal amplification)

Comments Comments

Nested Nested PCR, RT-PCR RT-PCR and quantitative quantitative PCR are modifi modification cationss of the PCR protocol. protocol. bDNA and 3SR 3SR are alternative alternative amplification amplification techniques.

15. Safety measures for preventing PCR contamination include

True

The use of uracil-N-glycosylase urac il-N-glycosylase (UNG)

True

Use Use of filtered pipette tips

True

Separate areas for master mix, template, and PCR product operation

True

Dedicated pipettes for master mix, template, and PCR products

True

Ultraviolet irradiation

Comments Comments

All All the above above may be useful useful in in preventing preventing contaminati contamination on of PCR. PCR.

16. The following statements are usually true

True

PCR is more sensitive sensitive than branched DNA assays

Fal False

Bran Branch ched ed DNA is more ore sen sensi siti tive ve than than Lig Ligase ase cha chaiin reac reacti tion on

True

Exponential amplification amplification occurs in PCR

True

Linear amplification amplification occurs in branched DNA

True

PCR is extremely liable liable to contamination

Comments Comments

Exponential amplifi amplification cation occurs in in PCR, LCR LCR and NASBA NASBA/3SR. /3SR. Therefore these techniques are extremely liable liable to contamination and are more sensitive than branche d DNA, where linear amplification amplification occurs.

17. Laboratory diagnosis of infectious mononucleosis mononucleosis include

True

Detection Dete ction of VCA-IgM

False

Detection of VCA-IgA

False

Seroconversion against EBNA

True

Paul-Bunell test

True

VCA IgG avidity test

Comments

Diagnosis Diagnosis of infectious mononucleosis mononucleosis is usually usually made by the Pa ul-Bunell ul-Bunell where hete rophil antibodies are detect ed and by the detection of EBV-IgM. EBV-IgM. VCA-Ig VCA-IgG G avidity test may be used t o confirm equivocal cases. Detec tion of elevate d titres of VCA-IgA VCA-IgA correlates with an increased risk for nasopharyngeal carcinoma and is used as a screening test. Seroconversion against against EBNA does not t ake place until months after the initial initial illness. illness.

18. Viruses that routinely establish latent infections in human sensory ganglia include

False

Epstein-Barr virus

True

Herpes Simplex Virus type 1

True

Varicella-Zoster Virus

True

Herpes Simplex Virus type 2

False

Human herpesvirus 6

Comments Comments

All the above herpesviruses can cause latent infections. However, However, only HSV HSV 1+2, and VZV VZV routinely establish establish latent latent infections in human sensory ganglia.



19. Rapid diagnosis of CMV disease i nclude

True

CMV pp65 antigenaemia

False

Conventional cell culture

True

DEAFF test

True

Detection Dete ction of CMV-DNA in blood by PCR

False

Rising antibody titres

Comments

Rapid diagnosi diagnosiss of CMV disease include include CMV CMV pp65 antigenaemia, antigenaemia, DEAFF DEAFF test, and Detection of CMV-DN CMV-DNA A in blood by PCR. 20. The following viruses viruses are associated with respiratory infections

False

Rotaviruses

True

Adenoviruses

True

Influenza viruses

False

HTLV-1

True

RSV

Comments Comments

Rotaviruses cause diarrhoea. HTLV-1 HTLV-1 is associated with with adult T-cell T-cell leukaemia leukaemia and tropical tropical spastic spastic paraparesis.

21. The following viruses viruses are thought to cause gastroenteritis

False

Ente roviruses

True

Ade noviruses

True

Norwalk-like viruses

True

Astroviruses

True

Rotaviruses

Comments Comments

Although Although enteroviruses may be found found in faeces, they are not associated associated with gastroenteritis. gastroenteritis. The other viruses viruses are associated associated with gastroenteritis.

22. The following viruses are transmitted from animals to humans

True

Influenza A H5N1

False

HTLV-1

True

Hantaviruses

False

P oliomyelitis

True

Rabies

Comments

Influenza A H5N1 is is otherwise otherwise known as the "bird "bird flu" It It afflicted Hong Kong in late late 1997 and was transmitted transmitted from poultry poultry to humans. Hantaviruses is transmitted transmitted from rodents to humans and rabies can be transmitted from various mammals to humans.

23. A chronic carrier state may occur in the following:

False

Hepatitis A

True

Hepatitis B

True

Hepatitis C

True

Hepatitis Delta

False

Hepatitis E

Comments Comments

A chronic chronic carrier carrier state can exist exist in hepatitis hepatitis B, B, C and Delta Viru Viruss infection infectionss



24. The following viruses are tr ansmitted by blood

False

Rubella

True

HIV

False

Measles

True

HBV

True

HCV

Comments Comments

HIV, HIV, HBV and HCV are transmitted transmitted by blood. Rubella and measles are transmitted transmitted via respiratory respiratory droplets

25. The following may be useful for prognostic purposes in HIV-infected individuals

False

HIV envelope antibody

True

HIV-p24 antigen

True

CD4 count

False

CD8 count

True

HIV viral load

Comments Comments

HIV envelope antibody remains remains high high throughout the course course of HIV infections and thus does not carry any prognostic prognostic value. HIV-p24 HIV-p24 antigen had been widely used in the past as a prognostic prognostic marker but it has been superseded by HIV viral load. CD4 count plays an important role in telling us what stage the disease is at.

26. The following markers are usually present in a hepatitis B carrier with chronic active hepatitis

True

HbsAg

False

HbsAb

False

Anti-HBc IgM

True

HBV-DNA

True

HbeAg

Comments Comments

In patients with with chronic active hepatitis, hepatitis, HBV replication is is present and hence HBV-DNA HBV-DNA and HbeAg. HbsAg HbsAg is present. present. Anti-HbcIgM Anti-HbcIgM is normally normally absent although it may occasionally be dete cted during periods of exac erbations.

27. Regarding viral infection of the central nervous system (CNS)

True rue

Meni eningi ngitis tis may occur ccur tog togethe etherr with ence enceph phal aliitis tis

True True

Enter Enterov ovir irus uses es are are one one of the the com commo mones nestt caus causes es of CNS CNS infect nfectio ions ns in child childho hood od

False

Electron Elect ron microscopy of the cerebrospinal cere brospinal fluid (CSF) is a useful diagnostic test

Fals alse

PCR PCR has has no role ole in in the the diagn agnosi osis of CNS infec nfecti tion onss

True rue

The dete detect ctiion of anti antibo body dy in the the CSF CSF is is a use usefu full diag diagno nost stiic mar marke kerr

Comments Comments

Meningitis Meningitis usually occurs together with with encephalitis. Enteroviruses Enteroviruses are one of the commonest causes of CNS infections in childhood. Electron microscopy is too insensitive insensitive to be useful as a diagnostic diagnostic test. P CR assays for HSV are now routinely used for the diagnosis of herpes simplex encephalitis. The detection of antibody in the CSF is a useful diagnostic marker

28. Regarding rash illnesses

True

Varicella-zoster Varicella-zoste r virus (VZV) (VZV) infection infect ion may cause a vesicular rash

Fals Falsee

The The ras rash h caus caused ed by parv parvov oviirus rus B19 B19 is is due due to the the pre prese sence nce of viru viruss in the skin skin



Fals alse

Meas easles is usual ually diag diagno nossed by viral cul cultur ture

True

Herpes simplex virus (HSV) (HSV) infection infect ion is usually diagnosed by viral culture

False

VZV cannot cann ot be grown in cell culture

Comments Comments

Varicella-zoster Varicella-zoster virus (VZ (VZV) V) infection may may cause a vesicular rash. rash. The rash rash caused by parvovirus parvovirus B19 is is probably an allergic allergic reaction due to the deposition of immune complexes. Measles is usually diagnosed by serology. Herpes simplex virus (HSV) infection is usually diagnosed by viral culture. VZV can be grown in cell culture although this is rarely used for diagnosis.

29. Rubella infection

True

Can be asymptomatic

True

May be indistinguishable from parvovirus parvov irus B19

False

Can have serious side effects when occurring in a woman in the third trimester of pregnancy

True

Is usually usually preventable by vaccination

True

May be acquired by having close contact with an infant with congenital rubella syndrome

Comments Comments

Rubella infection infection can be asymptomatic. asymptomatic. It may be indistin indistinguis guishable hable clinically clinically from parvovirus B19 B19 infection. The most most serious effects occur when a pregnant woman is infected in the first trimester trimester of pregnancy. It is usually usually preventable by vaccination. Infants with congenital rubella rubella syndrome pose a great infectious risk since they may excre te virus in great quantities up to 1 year of age.

30. Regarding laboratory tests for rubella

True

Rubella immunity immunity may be determined by an enzyme immunoassay immunoassay

Fal False

CFT CFT is com commonl only used used for for the the di diagno agnossis of acut acutee inf infec ecti tion on

True

IgM antibody is usually detectable after the onset of rash

False

Rubella vi virus ca cannot be be cu cultured

Fal False

PrePre-na nata tall dia diag gnos nosis of of rub rubel ellla in in a foe foetu tuss is is si simple ple and and rel reliiabl able

Comments Comments

Rubella immuni immunity ty may be determined by an enzyme enzyme immunoassay. immunoassay. CFT is not commonly commonly used for the diagnosi diagnosiss of rubella rubella infection; Haemagglutination-i Haemagglutination-inhibiti nhibition on tests a re. IgM antibody is usually detectable a fter the onset of rash Rubella virus can be cultured although this is rarely used as a method of diagnosis. diagnosis. Pre-nat al diagnosis diagnosis of rubella in a foetus such as amniocentesis involve some some degree of risk to the fetus.

Answers to Virology MCQ Paper 2

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