Microbiology - Virology-2

Question 1

Questions

Answer 1

Answers

Question 2

What must a positive (+) stranded RNA virus do/have to replicate?

Answer 2

Nothing. The positive (+) stranded RNA can immediately be translated by the host’s ribosomes into protein.

Question 3

What must a negative (-) stranded RNA virus do/have to replicate?

Answer 3

Negative (-) stranded RNA viruses must carry, in their capsid, an enzyme called RNA-dependent RNA polymerase.

Question 4

What does the retrovirus carry in order to replicate? How does the retrovirus replicate?

Answer 4

Reverse transcriptase.
With reverse transcriptase, RNA is transcribed to DNA. DNA undergoes transcription to mRNA, which is then translated to proteins.

Question 5

In a DNA virus, which strand is read?

Answer 5

The positive (+) strand is read, and the negative (-) strand is ignored.

Question 6

What are the two types of capsids?

Answer 6

Icosahedral and helical

Question 7

What are the DNA viruses?

Answer 7

Mnemonic: HHAPPPy viruses
Herpes
Hepadna
Adeno
Papova
Parvo
Pox

Question 8

Which DNA virus is single stranded?

Answer 8

Parvoviridae

Question 9

Which DNA virus does not have icosahedral symmetry?

Answer 9

Poxviridae

Question 10

Which DNA viruses are naked? Which are enveloped?

Answer 10

Naked: PAP
Papova
Adeno
Parvo
Enveloped:
Hepadna
Herpes
Pox

Question 11

Which RNA virus is double stranded?

Answer 11

Reoviridae

Question 12

Which RNA viruses are noneveloped?

Answer 12

Picorna, Calici, and Reoviridae

Question 13

Which RNA viruses undergo replication in the nucleus?

Answer 13

Retro and Orthomyxo

Question 14

In DNA virus replication, what are the three stages and what is produced during each?

Answer 14

Immediate early and Early: initially transcribed mRNA here encodes enzymes and proteins needed for DNA replication and for further transcription of late mRNA.
Late: The capsid structural proteins are synthesized from the late mRNA genome.

Question 15

What are the orthomyxoviridae viruses?

Answer 15

Influenza

Question 16

What is the structure of the orthomyxoviridae viruses?

Answer 16

The orthomyxoviridae are spherical virions. At the virion cent er lie 8 segments of negative (-) stranded RNA put together with a protein (nucleocapsid protein – NP) into a helical symmetry capsid.

Question 17

What are two glycoproteins that stud the outer membrane of the orthomyxoviridae?

Answer 17

Hemagglutinin Activity (HA)
Neuraminidase Activity (NA)

Question 18

What is the function of HA and NA?

Answer 18

Hemagglutinin (HA) can attach to host sialic acid receptors, present on the surface of RBCs and on upper respiratory tract cell membranes.
HA is needed for adsorption.
Neuraminidase (NA) cleaves neuraminic acid and disrupts the mucin barrier covering mucosal epithelial cells. This exposes the sialic acid sites.

Question 19

What is antigenic drift? Antigenic shift?

Answer 19

Antigenic drift: mutations to the HA or NA, leading to changes in their antigenic nature.
Antigenic shift: a complete change of HA, NA, or both.

Question 20

What are some differences between Paramyxoviridae and Orthomyxoviridae?

Answer 20

a) the negative (-) stranded RNA is in a single strand, not segmented
b) HA and NA are part of the same glycoprotein spike, not 2 different ones
c) Fusion (F) protein causes host cells to fuse together into multinucleated giant cells

Question 21

What are the four paramyxoviridae? Where do they all infect?

Answer 21

Parainfluenza
Respiratory syncytial virus
Mumps virus
Measles virus
All adsorb to and replicate in the upper respiratory tract.

Question 22

What is croup?

Answer 22

Croup is a parainfluenza infection of the larynx and other upper respiratory sructures (laryngotracheobronchitis) that occurs in children. Swelling of these structures produces airway narrowing. Stridor (wheezing sound) and a barking cough occur as air moves through the narrowed upper airways.

Question 23

What is the number one cause of pneumonia in young children?

Answer 23

Respiratory Syncytial Virus (especially in infants less than 6 months of age)

Question 24

How does RSV differ from the other paramyxoviridae?

Answer 24

RSV lacks both HA and NA glycoproteins

Question 25

What structures are involved in mumps virus infection?

Answer 25

``` Parotid gland (Parotitis) Testes (Orchitis) ```

Question 26

What is another name for Measles? How does it spread?

Answer 26

Rubeola | Spreads through nasopharyngeal secretions by air or by direct contact.

Question 27

What is the path of infection for measles?

Answer 27

``` Exposure Two week incubation Prodrome: conjunctivitis, swelling of the eyelids, photophobia, high fevers, hacking cough, rhinitis, and malaise Koplik’s spots Rash ```

Question 28

What are Koplik’s spots?

Answer 28

A day or two before the rash, patients infected with measles develop small red-based lesions with blue-white centers in the mouth

Question 29

What is the measles rash? How does it spread?

Answer 29

The measles rash is red, flat to slightly bumpy (maculopapular). It spreads out from the forehead to the face, neck, and torso, and hits the feet by the third day. As the measles rash spreads downward, the initial rash on the head and shoulders coalesces.

Question 30

What is a severe complication of measles?

Answer 30

Encephalitis: rare, but 10% of patients die Subacute sclerosing panencephalitis (SSPE): slow form of encephalitis caused by measles virus. Slowly progressing CNS disease, with mental deterioration and incoordination.

Question 31

``` Match the virus with its family: HAV Deltavirus HBV Flavivirus HCV Flavivirus HDV Hepevirus HEV Hepadnaviridae HGV Picornaviridae ```

Answer 31

``` HAV: Picorna HBV: Hepadna HCV: Flavivirus HDV: Deltavirus HEV: Hepevirus HGV: Flavivirus ```

Question 32

How are the hepatitis viruses transmitted?

Answer 32

Hepatitis A and E are transmitted via the fecal-oral route. | Hepatitis B, C, D, and G are transmitted via blood-to-blood (parenteral) contact.

Question 33

What lab values are found in acute viral hepatitis? Why?

Answer 33

AST and ALT are very high GGT, alkaline phosphatase, and bilirubin are slightly elevated In viral hepatitis, necrosis of hepatocytes causes the release of AST and ALT. GGT and alkaline phosphate are enzymes found in the bile pericanalicular cells, which are destroyed later on and to a lesser extent. As the infection worsens, the liver swells and the canaliculi narrow, resulting in bilirubin backup.

Question 34

What are the symptoms of hepatitis A infection?

Answer 34

``` Acute hepatitis (never chronic) Fulminant hepatitis (1-4%) and death (1%) ```

Question 35

What indicates an old HAV infection and no active disease?

Answer 35

Anti-HAV IgG. This antibody lasts indefinitely and is protective against future infection with HAV.

Question 36

What is the intact Hepatitis B virus called?

Answer 36

Dane particle.

Question 37

When a patient has anti-HBsAg, what does it mean? What about HBeAg?

Answer 37

Anti-HBsAg: The patient is immune against HBV. | HBeAg: this is a marker for active disease and a highly infectious state.

Question 38

When can pregnant mothers transmit HBV to their offspring?

Answer 38

When HBeAg is in the mother’s blood (90% transmission rate).

Question 39

What are the disease states caused by HBV?

Answer 39

1) Acute hepatitis 2) Fulminant hepatitis: severe acute hepatitis with rapid destruction of the liver. 3) Chronic hepatitis: a) Asymptomatic carrier: never develops antibodies against HBsAg, harbors virus without liver injury b) Chronic-persistent hepatitis: low-grade “smoldering” hepatitis c) Chronic active hepatitis: acute hepatitis state that continues without normal recovery (lasts > 6-12 months) d) Co-infection with HDV

Question 40

What causes liver injury during infection with HBV?

Answer 40

Liver injury appears to occur from a cell-mediated immune system attack on HBV. Viral antigens on the surface of infected hepatocytes are targets for cytotoxic T cells. Immune complexes can deposit in tissues and activate the immnune system, resulting in arthritis, and skin and kidney damage.

Question 41

What patients are more likely to be asymptomatic carriers of HBV?

Answer 41

Patients who have immunosupressed states, such as malnutrition, AIDS, and chronic illness, are more likely to be asymptomatic carriers because their immune system does not attack.

Question 42

What does the presence of HBsAg mean?

Answer 42

The presence of HBsAg always means there is a LIVE virus and infection, either acute, chronic, or carrier.

Question 43

What allows infection of Hepatitis D virus? What are the disease states of HDV and which one is more severe?

Answer 43

HDV is an RNA virus that can only replicate in the presence of HBV envelope, HBsAg. Co-infection: HBV and HDV are transmitted together parenterally. Superinfection: HDV infects a person who has chronic HBV infection. More severe, as lack of Anti-HBsAg allows both viruses to infect chronically.

Question 44

What are complications of HCV infection?

Answer 44

50% of patients get chronic hepatitis 20% develop cirrhosis Increased risk of hepatocellular carcinoma

Question 45

What two hepatitis viruses can predispose patients to chronic active hepatitis, cirrhosis, and hepatocellular carcinoma?

Answer 45

HBV and HCV.

Question 46

Why do HAV and HEV survive and infect in the gut?

Answer 46

Naked viruses do not rely on an envelope, and are not destroyed in the gut.