9: vir-vir interactions

Question 1

What are the most important Virus environments?

Answer 1

• another virus
• host cell
• host organism

Question 2

What are the different types of interactions between viruses?

Answer 2

• Advantageous
• Disadvantageous (interference)
• Neutral (virusexaltation)

Question 3

Different types of Advantageous type of interaction:

Answer 3

• On nucleic acid level (recombination)

- on protein level (complementation, phenotype mixing)

Question 4

Recombination in interactions between viruses:

Answer 4

exchange of genetic information

–> new virus generation - inherited new properties

Question 5

Intramolecular recombination in interactions between viruses:

Answer 5

• derailing of the polymerase during replication
• aujeszky´s disease virus: even 70% transfer
• sometimes between non-related viruses (Polyoma - Adenovirus)
• also with RNA viruses (i.e FMDV)

Question 6

Genetic reassortment in interactions between viruses:

Answer 6

• viruses with segmented genome (ie Orthomyxoviridae)
• exchange of segments during viral assembly
• sudden, major antigentic changes –> antigen shift

Question 7

Types of Reactivation:

Answer 7

Marker rescue

• Cross-reactivation
• Multiple reactivation

(this is the reason for why it is impotant to not use different live vaccines within a short time interval!)

Question 8

What is Cross-reactivation?

Answer 8

• attenuated vaccine strain + related virus
• repair of the defected virulence-genes
• i.e herpesviruses

Question 9

What is Multiple reactivation?

Answer 9

• between two attenuated virus-strains
• different defected genomic regions
• mutual completion

Question 10

Complementation in interactions between viruses:

Answer 10

• between defective and competent (helper) viruses
• exchange of enzymes (mainly polymerase)
• -> multiplication of the defected virus

Question 11

Types of multiplication of the defected virus:

Complementation in interactions between viruses

Answer 11

• heat-sensitive mutant + wild type virus
• avirulent virus + inactivated virulent virus (pox)
• dependovirus + adenovirus)

Question 12

Phenotype mixing in interactions between viruses:

Answer 12

• exchange of structural proteins
• leukosis + sarcoma virus: acquiring envelope proteins
• transcapsidation (polio + coxsackievirus)

Question 13

What does Interference, in interactions between viruses, mean?

Answer 13

One virus inhibits the multiplication of the other

Question 14

What are the different types of interference?

Answer 14

• Adsorption interference
• Autointerference
• Heterologous interference

Question 15

Adsorption interference?

Answer 15

competition for the same cell-surface receptor

• related viruses
• after phenotype mixing
• different viruses, but the same receptor (ie. CAR)

Question 16

Autointerference?

Answer 16

• complete and imcomplete forms of the same virus
• also adsorption
• incomplete virion: shorter nucleic acid ( –> higher mobility, plymerase affinity)
• competition for enzymes, ribosomes (defective interfering particles, DI)
• large amounts of incomplete progeny viruses (–> self-limiting infections (paramyxo, rhabo..)

Question 17

Heterologous interference?

Answer 17

• non-related viruses
• viral suppressor protein production
• ie. herpes, adenovirus - inhibits pox

Question 18

Virusexalation in interactions between viruses:

Answer 18

• the viruses are able to multiplicate independently

- the simultaneous infection does not effect the multiplication

Question 19

What is special about Virusexalation in interactions between viruses?

Answer 19

changes the viral influence on the hos cell or organism:

• increased pathogenicity (poliovirus + coxsackievirus in monkey)
• cytopathic effect appears (Classical swine fever virus, BVDC, newcastle disease virus