1. COPY CHOICE RECOMBINATION
+ strand
+ strand

2. Other methods recombination
Take advantage quirks in virus replication
eg. Coronaviruses (include SARS virus)

3. RECOMBINATION - SOME USES
mapping by recombination frequency
mapping by marker rescue

4. RECOMBINATION - SOME USES
marker rescue
TK - mt
TK mutant HSV
TK - wt
TK - wt
TK wt HSV

5. RECOMBINATION - SOME USES
mapping by recombination frequency
mapping by marker rescue
development of recombinant viruses for vaccines and therapeutic reasons

6. RECOMBINATION - SOME USESTK
vaccinia virus T K
rabies G
rabies G
vaccinia virus for use
as rabies vaccine

7. raccoon eating bait with rabies vaccine in it

8. REASSORTMENT

9. REASSORTMENT form of recombination (non classical) very efficient
segmented viruses only
can occur naturally
used in some new vaccines
eg for influenza and rotaviruses

10. INFLUENZA VIRUS cold adapted temperature-sensitive attenuated
live vaccine
intranasal delivery
approved 2003
adapted fromTreanor JJ Infect. Med. 15:714

11. NON-SEGMENTED NEGATIVE STRAND RNA VIRUSES
no classical recombination
no copy choice
no reassortment
least ability to exchange genetic material

12. other aspects of viral genetics

13. COMPLEMENTATION ts M ts N wt N wt M
Interaction at the functional level, NOT the nucleic acid level
ts N
wt M
ts M
wt N
ts mutant 1
ts mutant 2
Progeny virus assembled using wt N and wt M proteins
Genomes in progeny are either ts M or ts N
mutants which can complement are generally in different genes

14. DEFECTIVE VIRUSES genome
lack gene(s) necessary for a complete infectious cycle
‘helper’ virus provides missing functions
package me!
copy me!
genome
package me!
copy me!

15. DEFECTIVE VIRUSES some examples of defective viruses
some retroviruses (use related helper)
hepatitis delta virus (uses unrelated helper)

16. DEFECTIVE INTERFERING (DI) VIRUSES (PARTICLES)
decrease replication of helper virus
compete for viral precursors, etc.
may modulate wt infections
occur naturally eg. DI measles virus in subacute scelerosing panencephalitis - SSPE

17. PHENOTYPIC MIXING no changes in genome possibly altered host range
possibly resistant to antibody neutralization

18. PHENOTYPIC MIXING
PSEUDOTYPE

19. Antigenic variation 1-Antigenic shift 2- 1-Antigenic drift
Occur in some viruses such as Influenza virus