Virology

Question 0

Mutations can produce antigenic, drug-resistant or attenuated variants
Genomic reassortment causes epidemics
Complementation: one virus produces a protein that can be used by another virus
Phenotypic mixing: two different viruses infect the same cell

Answer 0

Viral genetics

Question 1

Naked viruses with double-stranded circular DNA and an icosahedral nucleocapsid
Least 100 types
Direct contact or sexually
Infect squamous cells and induce formation of cytoplasmic vacuole (koilocytes)
Genes E6 and E7

Answer 1

HPV

Question 2

Only causes disease in immunocompromised hosts

Causes progressive multifocal leukoencephalopathy (PML) in patients with AIDS

Answer 2

JC Polyoma Virus

Question 3

Only causes disease in immunocompromised hosts

Causes hemorrhagic cystitis and neuropathy and in patients with solid organ (kidney) and bone marrow transplants

Answer 3

BK Polyoma Virus

Question 4

Enveloped virus with icosahedral nucleocapsid and linear double-stranded DNA

Answer 4

Herpes Simplex Viruses

Question 5

Member of flavivirus family
Most common cause of epidemic encephalitis
Most prevalent in SEA
transmitted by Culex mosquitoes
Thalamus infarcts on CT scan

Answer 5

Japanese B Encephalitis

Question 6

Flavivirus
Bird-mosquitoes-man cycle
Initial self-limited febrile illness with progression to neuroinvasive disease

Answer 6

West Nile Fever

Question 7

“Thread-like” viruses
Longest viruses
Outbreak of hemorrhagic fever in Zaire (1976)
100% mortality rate

Answer 7

Ebola Hemorrhagic Fever

Question 8

Retrovirus causing adult T-cell leukemia and a HTLV-associated myelopathy
HP: malignant T cells with flower-shaped nucleus

Answer 8

Human T-cell lymphotropic virus (HTLV)

Question 9

Envelope virus with two copies (diploid) of a single-stranded, positive-polarity RNA genome
Most complex of the known retroviruses
Many serotypes

Answer 9

Human Immunodeficiency Virus

Question 10

Enveloped virus with an icosahedral nucleocapsid and one ss-positive-RNA
Transmission: respiratory droplet, transplacental

Infection confers lifelong immunity
Prevented by giving live-attenuated vaccine
Should not be given to immunocompromised patients or to pregnant women

Answer 10

Rubella virus

Question 11

Incubation of 14-21 days
Prodrome followed by 3-day maculopapular rash and posterior auricular LAD
Face-trunk-arms-legs
Immune complex polyarthritis in adults

Answer 11

German measles

Question 12

p24, p7 proteins

p17 protein

Answer 12

Gag gene

Function:

• nucleocapsid (p24, p7)
• matrix (p17)

Question 13

Reverse transcriptase protein

Protease protein

Integrase protein

Answer 13

Pol gene

Function:

• transcribes RNA genome into DNA (reverse transcriptase)
• cleaves precursor polypeptides (protease)
• integrates viral DNA into host cell DNA (integrase)

Question 14

gp120 protein

gp41 protein

Answer 14

env gene

Function:

• attachment to CD4 protein ANTIGENICITY CHANGES RAPIDLY (gp120)
• fusion with host cell (gp41)

Question 15

Group-specific antigen

Located in the core

Not known to vary

Antibodies against p24 do not neutralize HIV infectivity but serve as important serologic markers of infection

Answer 15

p24

Question 16

Interacts with the CD4 receptor

Gene mutates rapidly –> many antigenic variants

Antibody neutralizes HIV infectivity, but the rapid appearance of variants –> difficult to prepare vaccine

High mutation rate may be due to lack of an editing function in the reverse transcriptase

Answer 16

gp120

Question 17

Most immunogenic region of gp120

Answer 17

V3 loop

Question 18

Mediates the fusion of the viral envelope with the cell membrane at the time of infection

Answer 18

gp41

Question 19

Proteins: tat

Function: activation of transcription of viral genes

Answer 19

Tat gene

Question 20

Proteins: rev

Function: transport of late mRNAs to cytoplasm

Answer 20

rev gene

Question 21

Proteins: Nef

Function: decreases CD4 and class I MHC proteins

Answer 21

nef gene

Question 22

Proteins: Vif

Function: enhances hypermutation

Answer 22

vif gene

Question 23

Proteins: vpr

Function: transport in nondividing cells

Answer 23

vpr gene

Question 24

Proteins: vpu Function: enhances virion release

Answer 24

vpu gene

Question 25

``` Transmission: Original source - chimpanzee Transfer of body fluids Transplacental and perinatal Needlestick ```

Answer 25

Human Immunodeficiency Virus

Question 26

Stages of infection (HIV)

Answer 26

- phase 0 (infection) - phase 1 (window period) - phase 2 (seroconversion) - phase 3 (latent period) - phase 4 (early symptomatic) - phase 5 (aids)

Question 27

HIV acquired through sexual intercourse, blood, or perinatally

Answer 27

Phase 0 - INFECTION

Question 28

Rapid viral replication but HIV test is negative

Answer 28

Phase 1 - WINDOW PERIOD

Question 29

Peak of viral load, positive HIV test, mild flu-like illness, lasting 1-2 weeks

Answer 29

Phase 2 - SEROCONVERSION

Question 30

Asymptomatic, CD4 goes down, lasts 1-15 years

Answer 30

Phase 3 - LATENT PERIOD

Question 31

CD4 500 to 200, lasts 5 years, mild mucocutaneous, dermatologic and hematologic illnesses

Answer 31

Phase 4 - EARLY SYMPTOMATIC

Question 32

CD4 <200, lasts 2 years, AIDS-defining illnesses develop

Answer 32

Phase 5 - AIDS

Question 33

Distinguished from all other RNA viruses by the presence of an unusual enzyme, reverse transcriptase Reverse transcriptase - which converts a single-stranded RNA viral genome into double-stranded viral DNA

Answer 33

Retroviridae

Question 34

Infected during the 1st trimester ``` Associated abnormalities: Patent ductus arteriosus Congenital cataracts Sensorineural deafness Mental retardation ```

Answer 34

Congenital Rubella Syndrome

Question 35

Enveloped virus with one piece of single-stranded, positive-polarity RNA Hypervariable region in envelope glycoprotein 6 serotypes Diagnosis by anti-HCV or HCV RNA Transmission: - most prevalent blood-borne pathogen - major mode: blood-borne (IV drug abusers) - minor modes: needle-stick, vertical transmission, sexual Pathogenesis: - replication in liver by liver-specific micro-RNA - hepatocellular injury due to immune attack - alcoholism greatly enhances rate of hepatocellular CA - chronic carriage of HCV is much higher than HBV Spectrum of disease: - incubation period of 8 weeks - clinical presentation resembles hepatitis B - autoimmune reactions - main cause of essential mixed cryoglobulinemia

Answer 35

Hepatitis C Virus Treatment: Acute hepatitis C - interferon Chronic hepatitis - peginterferon Liver transplantation for severe cirrhosis

Question 36

Enveloped virus with helical nucleocapsid and one piece of single-stranded, positive-polarity RNA Prominent club-shaped spikes form a "corona" 2 serotypes Transmission: - horseshoe bat (reservoir) - Civet cat (intermediate host) - respiratory droplet transmission Spectrum of disease: - COMMON COLDS (2nd most common colds) - severe acute respiratory syndrome (SARS)

Answer 36

Coronavirus

Question 37

DNA VIRUSES DNA Viruses are HHAPPPy viruses

Answer 37

Hepadna Herpes Adeno Pox Parvo Polyoma Papilloma

Question 38

All DNA viruses have DOUBLE-stranded DNA except

Answer 38

PARVOVIRUS

Question 39

All DNA viruses have linear DNA except

Answer 39

Papilloma Polyoma Hepadna

Question 40

All DNA viruses are icosahedral except All DNA viruses replicated in the nucleus except

Answer 40

POXVIRUS

Question 41

Naked virus with icosahedral symmetry Single-stranded DNA genome One serotypes MOT: respiratory droplets & transplacental Not oncogenic No vaccine

Answer 41

Parvovirus B19 (FIFTH DISEASE)

Question 42

NAKED DNA viruses double-stranded linear DNA and an icosahedral nucleocapsid Only virus with fiber (PENTON) 41 antigenic types MOT: aerosol droplet, respiratory fecal-oral, direct contact ``` Spectrum of disease: URT: pharyngitis, conjunctivitis, coryza LRT: bronchitis, atypical pneumonia GIT: acute gastroenteritis GUT: hemorrhagic cystitis Histopath: COWDRY TYPE B intranuclear inclusions ``` Not oncogenic Has vaccine

Answer 42

Adenovirus

Question 43

NAKED DNA viruses with double-stranded circular DNA and an icosahedral nucleocapsid Least 100 types MOT: direct contact or sexually Pathogenesis: Infect squamous cells and induce formation of cytoplasmic vacuole (koilocytes) Genes E6&E7 Is oncogenic Has vaccine

Answer 43

Human Papillomavirus

Question 44

Bright red cheek rash (slapped cheeks) with fever, coryza and sore throat

Answer 44

Erythema Infectiosum (FIFTH DISEASE)

Question 45

Transient by put severe aplastic anemia in children Sickle cell anemia, thalassemia or spherocytosis

Answer 45

Aplastic crisis

Question 46

Fetal infections on PARVOVIRUS

Answer 46

1st trimester: fetal death 2nd trimester: hydrops fetalis

Question 47

Immune-complex arthritis of small joints

Answer 47

Arthritis

Question 48

Pancytopenia in immunodeficiency patients in PARVOVIRUS

Answer 48

CHRONIC B19 infection