Lec 10: Reoviruses (dsRNA virus)

Question 1

Icosahedral viruses with dsRNA genomes isolated from…
Initially, no…

THEREFORE –>

Answer 1

…the Respiratory tracts and Enteric tracts of humans/animals
… no disease could be associated = Orphan

–> R + E + O = REOviruses

Question 2

Reovirus host =

Answer 2

mammals, birds, fish, invertebrates including insects, plants and fungi

Question 3

most of the plant reoviruses are transmitted between plants by =
The viruses replicate…

Answer 3

= insect vectors
…in BOTH the plant and the insect, generally causing disease in the plant, but little or no harm to the infected insect.

Question 4

The most common cause of diarrhea is

Answer 4

a virus that infects the gut – “stomach flu.”

Question 5

the cause of most types of food poisoning =

Answer 5

= Infection by bacteria

Question 6

Rotaviruses are a major cause of

but…

Answer 6

gastroenteritis among children <5 y/o

…but other viruses such as Norovirus (+ssRNA) may also cause gastroenteritis

Question 7

We focus on

Answer 7

Rotaviruses that infect human and animals

Question 8

diarrhea death rate is high in

Answer 8

developing countries

Question 9

Rotaviruses seasonality: (3)

Answer 9

• Winter months (Nov. through May in US)
• Gradual spread from West to East
• Year-round in the Tropics

Question 10

Rotaviruses transmission

& vehicles?

Answer 10

mainly via fecal-oral route

& food, water, and fomites (ex: clothing/bedding)

Question 11

Rotaviruses are very resistant to

Answer 11

environmental conditions in temperate climate months

Question 12

Rotavirus virion shape =

Answer 12

spherical, with structures resembling the spokes of a wheel, so the viruses were named after the Latin word “rota” (= wheel)

Question 13

Rotavirus virion structure =

Answer 13

triple-layered particle as the capsid has 3 layers, each constructed from a distinct Virus Protein (VP)

Question 14

Rotavirus virion inner and middle layers =

Answer 14

constructed from VP2 and VP6 respectively, are perforated by channels

Question 15

Rotavirus virion middle layer =

Answer 15

contains the ‘spokes’ of the ‘wheel’ and is the major component of the virion

Question 16

Rotavirus virion outer layer =

Answer 16

constructed from VP7, which is glycosylated.

Question 17

Rotavirus have __ _____ genome segments

Answer 17

11 dsRNA

Question 18

Rotavirus genome segment codes…
…total of =
…to be exact,…

Answer 18

one protein, except one that codes 2 proteins.
So there are a total of 12 proteins.
to be exact –> 6 structural proteins (VP) and 6 non-structural proteins (NSP).

Question 19

VP =

NSP =

Answer 19

structural proteins (VP)
non-structural proteins (NSP)

Question 20

NSP4 acts as

Answer 20

a viral enterotoxin

Question 21

NSP4 is not

Answer 21

packed into the virions

Question 22

NSP4 induces

Answer 22

dose- and age-dependent diarrhea in lab animals

Question 23

NSP4 increases…

disturbing. ..
damages. ..

Answer 23

• intracellular Ca++ concentration
• disturbing the cellular electrolyte homeostasis,
• and also damages tight junction between cells.

Question 24

To attenuate the symptoms of rotavirus-induced diarrhea:

Answer 24

Immunize mice with an NSP4-based vaccine, followed by specific antibody production

Question 25

Rotaviruses infect cells called _______ @…

Answer 25

enterocytes @ the ends of the villi (finger-like extensions) in the small intestine.

Question 26

2 possible ways in which a rotavirus virion can enter the cell:

Answer 26

1. ) direct penetration of the virion across the plasma membrane
2. ) endocytosis

Question 27

rotaviruses =

7 Baltimore classes

Answer 27

class III
dsRNA

Question 28

first step of rotavirus replication:

Answer 28

The outer layer of the virion is removed, leaving a double-layered particle in which transcription is activated

Question 29

A problem that dsRNA viruses must overcome is:

However, Most of these viruses, including the rotaviruses, have solved this problem by…

Answer 29

the fact that dsRNA is a potent inducer of a number of cell defense mechanisms including apoptosis, interferon production and RNA silencing

ensuring that the viral dsRNA is always enclosed within virus protein structures, and is never free in the cytoplasm to trigger these defenses.

Question 30

The final stages of virion assembly involve:

Answer 30

the addition of the outer layer of the capsid and the spikes

Question 31

Virions are released from the cell either by: (2)

Answer 31

lysis or exocytosis

Question 32

as a result of rotavirus disease/infection…

Answer 32

1. ) Enterocytes on the villi are destroyed, leading to reduced absorption of water, salts and sugars from the gut.
2. ) tight junctions between cells are damaged by NSP4, allowing leakage of fluid into the gut.
3. ) secretion of water and solutes by secretory cells, result in diarrhea and this can lead to dehydration

Question 33

Rotavirus-mediated diarrhea 3 “punches”:

Answer 33

1. ) reduced absorption of water, salts and sugars from the gut due to destroyed enterocytes
2. ) leakage of fluid into the gut due to damaged tight junction between cells
3. ) Secretion of water and solutes by secretory cells

Question 34

(Diarrhea development)

After a short incubation period of one to two days,…

Answer 34

…the onset of the illness is sudden, with watery diarrhea lasting four to seven days, vomiting and rapid dehydration.

Question 35

Diagnosis of a rotavirus infection is…

The main techniques are…

Answer 35

…relatively easy as such large numbers of virus particles (up to 1011 particles/ ml of faeces) are shed.
…ELISAs, EM, etc.

Question 36

Rotavirus disease treatment =

Answer 36

Simple treatment: rehydrating the patient with a solution of salts and sugar

Question 37

In some parts of the world, the means for rotavirus treatment are not…

Answer 37

…available.

~1/2 million deaths of infants and young children due to rotavirus infections worldwide.

Question 38

most rotavirus infections are confined to…

sometimes the virus may…

Answer 38

…the gut,

…cross the gut and infect other tissues.

Question 39

Rotaviruses are relatively resistant to…

and susceptible to…

Answer 39

…handwashing agents

…disinfection with 95% ethanol, ‘Lysol’, formalin

Question 40

Rotaviruses Vaccines: (2)

Answer 40

RotaTeq (Live oral vaccine)

Rotarix (Live attenuated vaccine)