Lec 11: Picornaviruses (& other +ssRNA viruses) Class IV

Question 1

class IV virus genome is

Answer 1

+ssRNA that functions as mRNA.

Question 2

The first virus molecules to be synthesized in an infected cell are

Answer 2

proteins, in contrast to all other viruses, where transcription of virus genes must occur before virus protein synthesis can start.

Question 3

picornavirus hosts =

Answer 3

mammals and birds.

Question 4

Most picornaviruses grow readily in…

Answer 4

…cell culture, are easy to purify and are stable, making them popular viruses for laboratory studies.

Question 5

Some important picornaviruses: (3)

Answer 5

Hepatitis A virus
Poliovirus
Foot & Mouth disease virus

Question 6

cvirus transmitted through:

Answer 6

ingestion of contaminated food and water, or through direct contact with an infectious person

Question 7

Hepatitis A Epidemics can be

Answer 7

explosive in growth and cause significant economic losses.

Question 8

most effective ways to combat the Hepatitis A (2)

Answer 8

Improved sanitation and vaccines

Question 9

Hepatitis A virus infections

Answer 9

happen in many countries with poor sanitation.

Question 10

In most infants and young children, Hepatitis A infection is

Answer 10

asymptomatic or mild, and leads to life-long immunity

Question 11

When adults become infected with Hep A about 75% develop

Answer 11

jaundice.

Question 12

______ hepatitis A is a ____ complication, which can be fatal.

Answer 12

severe

rare

Question 13

The average incubation period for Hepatitis A is

Answer 13

28 days (range: 15–50 days)

Question 14

Hep A also causes

Answer 14

jaundice

Question 15

the majority of Poliovirus infections are _______ ________ infections of the…

Answer 15

relatively harmless

…oropharynx and the gut.

Question 16

Serious Poliovirus disease occurs only after…
resulting in…
and…

Answer 16

…other tissues become infected
…viraemia (virus in the blood)
…spread of infection to the central nervous system.

Question 17

viraemia =

Answer 17

(virus in the blood)

Question 18

Serious poliovirus disease is very rare in…
If, however, there is less poliovirus in the human environment, so that most infections occur after these antibodies have disappeared, then…
So, polio is a disease primarily associated with…

Answer 18

…babies, who still have anti-poliovirus antibodies acquired from their mothers.
…infection of the central nervous system is more likely.
…improving standards of hygiene and sanitation!

Question 19

Poliovirus infection of the central nervous system may result in

Answer 19

meningitis (from which most patients recover completely),
encephalitis and/or
paralytic poliomyelitis.

Question 20

paralytic poliomyelitis is due to

Answer 20

virus replication in motor neurones of the spinal cord or the brain stem, resulting in paralysis of limbs and/or breathing muscles

Question 21

The use of _____ has proved very effective in preventing polio.

Answer 21

vaccine

Question 22

By the start of the 21st century, the annual number of world cases was

Answer 22

1% of the number of cases in 1988

Question 23

Polio has been eradicated from

Answer 23

many parts of the world and there is hope that the disease will soon be completely eradicated.

Question 24

Foot and mouth disease virus aka

Answer 24

(FAMDV)

Question 25

(FAMDV) range

Answer 25

has a much wider host range than other picornaviruses

Question 26

Outbreaks of foot and mouth disease can have

Answer 26

serious economic consequences, e.g. milk production drops.

Question 27

(FAMDV) Usually do not infect

however…

Answer 27

humans

…HAND, foot and mouth disease is common in children

Question 28

(HFAMD) caused by: (2)

Answer 28

Coxsackievirus A16
Enterovirus 71 (EV-71)
(both +ssRNA virus)
NOT by FAMDV

Question 29

(HFAMD) 
Transmission:
Symptoms: 
Infect: 
Usually no \_\_\_\_\_\_\_ is needed

Answer 29

Transmission: contact with the mucus, saliva, or feces of an infected person

Symptoms: mild fever followed by a rash

Infect: mostly children <5 yr, occasionally adults

Usually no TREATMENT is needed

Question 30

(Picornavirus Virion - Capsid) symmetry?

Answer 30

Icosahedral symmetry,

made from 60 copies each of 4 virus proteins (VP1–4, numbered from the largest to the smallest).

Question 31

Evolution of picornaviruses has generated a lot of…
some of which is…
This antigenic variability creates problems for…

Answer 31

…variability in the capsid proteins.
…reflected in the existence of distinct serotypes
…the development of vaccines against these viruses.

Question 32

(Picornavirus Virion - Genome) type?

Answer 32

+ssRNA

Question 33

(Picornavirus Virion - Genome)

consists of…

Answer 33

one very large ORF flanked by untranslated regions.

Within the untranslated region at the 5 end there is much secondary structure

Question 34

(Picornavirus Replication)

Attachment via

Answer 34

receptor CD155, a glycoprotein expressed on the surface of many cell types

Question 35

“CD”:

Answer 35

cluster of differentiation (also known as cluster of designation or classification determinant) is a protocol used for the identification and investigation of cell surface molecules providing targets for immunophenotyping of cells.)

Question 36

(Picornavirus Replication)

Entry: (2)

Answer 36

1. ) transfer of the RNA from the virion into the cytoplasm at the plasma membrane, leaving the capsid at the cell surface (injects RNA)
2. ) endocytosis

Question 37

Picornavirus transcription and genome replication: (3)

Answer 37

1. ) The genome acts as a template for synthesis of (−) RNA.
2. ) (−) RNA acts as the template for synthesis of (+) RNA,
3. ) Some of these (+) RNA functions as mRNA, some as progeny genomes and some as templates for further (−) RNA synthesis.

Question 38

(Picornavirus Replication)

Assembly and exit:

Answer 38

A copy of the genome enters a procapsid to form a virion. Progeny virions leave the cell when it lyses

Question 39

(Picornavirus recombination)

A cell is infected with…

Answer 39

…two strains of a virus. In the progeny virions there may be some that have part of the genome of strain 1 and part that of strain 2.

Question 40

(Picornavirus recombination)

The oral polio vaccine contains…

Answer 40

…attenuated strains of all three poliovirus serotypes.