COPY CHOICE RECOMBINATION

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COPY CHOICE RECOMBINATION + strand + strand www.freelivedoctor.com

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

RECOMBINATION - SOME USES mapping by recombination frequency mapping by marker rescue www.freelivedoctor.com

RECOMBINATION - SOME USES marker rescue TK - mt TK mutant HSV TK - wt TK - wt TK wt HSV www.freelivedoctor.com

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

RECOMBINATION - SOME USES TK vaccinia virus T K rabies G rabies G vaccinia virus for use as rabies vaccine www.freelivedoctor.com

raccoon eating bait with rabies vaccine in it www.freelivedoctor.com

REASSORTMENT www.freelivedoctor.com

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

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

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

other aspects of viral genetics www.freelivedoctor.com

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 www.freelivedoctor.com

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! www.freelivedoctor.com

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

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 www.freelivedoctor.com

PHENOTYPIC MIXING no changes in genome possibly altered host range possibly resistant to antibody neutralization www.freelivedoctor.com

PHENOTYPIC MIXING PSEUDOTYPE www.freelivedoctor.com

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

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