10 - DNA Viruses

Question 1

Herpes viruses

Answer 1

• Large dsDNA genomes encoding 100-200 genes
• All herpesviruses are enveloped icosahedral viruses
• Induce latent infections in humans

Question 2

Subfamilies of herpesviruses

Answer 2

• Alpha subfamily (neurons and epithelia)
• Beta and gamma subfamilies (leukocytes and epithelia)

Question 3

Alpha subfamily of herpesviruses

Answer 3

• Herpes simplex virus type 1
• Herpes simplex virus type 2
• Varicella zoster

Question 4

Beta and gamma subfamilies of herpesviruses

Answer 4

• Human cytomegalovirus
• Epstein Barr virus
• Human herpes virus 6-8
• B virus

Question 5

Where does HSV-1 persist in a latent state

Answer 5

Trigeminal ganglia and is reactivated by trauma, fatigue, sunlight, emotional stress

Question 6

Herpes simplex virus type 1 (HSV-1)

Answer 6

• cold sore, is a recurrence of the first or primary infection
• Herpetic whitlow is HSV infection of fingers and thumbs (often caused by autoinoculation secondary to genital herpes and health care workers)

Question 7

Herpes simplex virus type 2 (HSV-2)

Answer 7

• Associated with genital herpes
• Infects epithelial cells of external genitalia, rectum and adjacent skin

Question 8

Neonatal herpes

Answer 8

• HSV-2 can be transmitted to newborns during delivery
• Results in blindness and neurological disease in babies.
• Caesarian delivery recommended

Question 9

Varicella Zoster Virus (VZV)

Answer 9

• Receptor is mannose-6-phosphate
• Acquired by respiratory route (airborne)
• Vesicles similar to those produced in HSV are formed, and form lesions, but unlike the HSV lesions are not infectious
• Shingles is reactivation of chickenpox

Question 10

2 main syndromes caused by VZV

Answer 10

• Varicella (chickenpox)
• Zoster (shingles)

Question 11

Shingles

Answer 11

• the virus becomes dormant in the dorsal root ganglion but can also affect any sensory nerve
• Can be reactivated to cause shingles
• Usually only one such event in a lifetime (elderly or immunocompromised)

Question 12

Example of drug to treat HSV and VZV

Answer 12

Acyclovir

Question 13

Human cytomegalovirus (HCMV)

Answer 13

• 80% prevalence
• Infection is initiated through a nonspecific interaction with heparan sulfate proteoglycans
• Life long
• Interferes with host immune functions including antigen presentation, cytokine production, and natural killer cell activity

Question 14

Cytomegalo

Answer 14

Enlarged cell

Question 15

Risk groups for HCMV

Answer 15

• Organ transplant recipients
• Immunocompromised (especially AIDS patients)
• Newborns

Question 16

Epstein Barr virus (EBV)

Answer 16

• Causes infectious mononucleosis (glandular fever/kissing disease)
• Infects epithelial cells lining the throat.
• New virus particles infect memory B cells, which rapidly proliferate and take on an atypical appearance that is useful in diagnosis

Question 17

How does EBV spread

Answer 17

Present in oropharyngeal secretions and therefore is spread by mouth-to-mouth contact or shared drinking glasses

Question 18

Manifestations of EBV

Answer 18

Enlargement of lymph nodes and spleen, sore throat, fever, headache, and general tiredness and weakness

Question 19

Severe diseases caused by EBV

Answer 19

• Burkitt’s lymphoma
• nasopharyngeal carcinoma

Question 20

Burkitt’s lymphoma

Answer 20

• Tropical africa
• Coinfection with malaria, or immunodeficiency
• Those infected with HIV

Question 21

Human papilloma virus (HPV)

Answer 21

• Nonenveloped icosahedral, small dsDNA viruses
• Infect epithelial cells through micro-abrasions causing genital warts and/or cancerous lesions
• Spread by direct contact and by autoinoculation via scratching

Question 22

How many strains of HPV are there and how many are transmitted sexually

Answer 22

> 170 strains with >40 transmitted sexually

Question 23

HPV16 and 18

Answer 23

Responsible for most cervical cancers in women

Question 24

HPV 6 and 11

Answer 24

Responsible for genital warts and laryngeal papillomatosis

Question 25

how are early pre cancerous changes of HPV detected

Answer 25

Via pap smears

Question 26

Nona-valent human papillomavirus vaccine

Answer 26

- 9 HPV strains, including 6, 11, 16 and 18 - School-based National HPV Vaccination Programs (Targets young adolescent)

Question 27

Hepatitis B virus (HBV)

Answer 27

- dsDNA virus - Infect liver cells (hepatocytes) and causes hepatitis (inflammation of the liver) - Most infections are acute and the virus is cleared by immune response

Question 28

Transmission of HBV

Answer 28

- Parenteral transmission - Highest concentration of virus found in blood (lower conc. in semen, vaginal fluid) - 50% of acute HBV is acquired sexually - Needlestick injury, needle sharing, tattooing, acupuncture

Question 29

Clinical features of HBV

Answer 29

- symptomatic acute hepatitis: fatigue, malaise, fever, abdominal pain, icterus (jaundice), pruritus (itching) - Usually asymptomatic in neonates and young children

Question 30

Hepatitis B replication

Answer 30

- Virus enters the cell - Capsid disassembly - Viral relaxed circular DNA enters nucleus of cell - CCC-DNA created - Transcription to RNA occurs - RNA is packaged up into a new capsid - New virus is created - Virus leaves cell.

Question 31

What happens if HBV is not cleared

Answer 31

- Virus continues to replicate and patient becomes chronic carrier (continued HBV infection 6 months after infection) - Associated with development of cirrhosis (liver damage and scarring) and liver cancer (hepatocellular carcinoma)

Question 32

Prevention of perinantal HBV transmission

Answer 32

providing hepatitis B immune globulin and hepatitis B vaccine to infants within 12 hours of birth

Question 33

Blood tests for HBV

Answer 33

- Hepatitis B surface antigen (HBsAg) is detectable in blood soon after infection - Clearance of HBsAg from blood, and appearance of anti-HBs, indicates recovery - Persistence of HBsAg (> 6 months after infection), lack of anti-HBs, indicates chronic infection (carrier state)

Question 34

Polyoma virus JC

Answer 34

Fatal demyelinating disease of the CNS: progressive multifocal leukoencephalopathy (PML) in which oligodendrocytes are destroyed